FILTER BANK CIRCUIT, SPECTRUM ANALYZER, SIGNAL ...GENERATOR, AND METHOD FOR CONTROLLING FILTER BANK CIRCUIT USING SAME

Abstract

To provide a filter bank circuit which can support measurement or testing of all bandwidths by securing overlap in the entire filter group by switching the filter groups with simple switching control while securing a guard band within each filter group by using an electronically switchable switch and the multiple filter groups, and provide a spectrum analyzer, a signal analyzer, a signal generator using the same, and a control method of the filter bank circuit.SOLUTION: A filter bank circuit 10 includes, for example, a one-pole two-throw changeover switch 20 and filter groups G1, G2. The filter groups G1, G2 have m filters 21, 22, respectively. The filters 21, 22 are set in pass bands that do not overlap with the pass bands of other filters 21, 22 in the group, but overlap with the pass bands of the filters 21, 22 in the mutually-different groups.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a filter bank circuit that switches filters on a group-by-group basis to maintain overlap between filter bands, and to a spectrum analyzer, a signal analyzer, a signal generator, and a method for controlling the filter bank circuit that use the same. [Background technology]

[0002] Some measuring instruments require the function of a splitter to separate each channel from a signal bundled into multiple frequency channels, or conversely, the function of a multiplexer to combine multiple frequency channels.

[0003] As an example of this type of measuring equipment, a frequency conversion device having a signal demultiplexing section that divides a specified frequency range into multiple bands, extracts signal components from each of the divided bands, and outputs them in parallel has been known (for example, Patent Document 1, etc.).

[0004] Also, a front-end circuit is known that is provided at the front end of a measuring device and has three circulators, three transmit filter banks, and three receive filter banks between a first switch connected to a first antenna and an RFIC, and that supports transmission and reception of multiple (three types of) frequencies (e.g., FIG. 4 of Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-246956 A [Patent Document 2] JP 2014-120842 A Summary of the Invention [Problem to be solved by the invention]

[0006] Examples of measuring instruments having a front-end circuit equipped with a filter function such as a transmission filter bank and a reception filter bank described in Patent Document 2 include a spectrum analyzer and a test signal generator.

[0007] A conventional spectrum analyzer includes a filter bank 200 having a structure shown in Fig. 17, for example, in front of a frequency conversion section (corresponding to the frequency conversion section 100 in Fig. 4) constituting a front-end circuit. This filter bank 200 has a configuration in which a movable section 201, which houses a plurality of band-pass filters (BPFs) 1, BPF2, ...BPFn each having a different passband in the millimeter wave band, is held in a mounting section 202 so that it can move in the direction of the arrow in the figure (up and down). An input side (In) wave guide (waveguide) 203a and an output side (Out) wave guide 203b are provided on both ends of the mounting section 202, and the wave guides 203a and 203b are arranged on a straight line. In this conventional filter bank 200, the movable part 201 is moved within the mounting part 202 so that a BPF (in this example, BPF3) corresponding to a desired frequency is located between the radio wave guides 203a, 203b on both sides, thereby extracting a signal of a frequency component corresponding to the pass band of BPF3 from the signal to be measured input from the input side (In).

[0008] In a spectrum analyzer that employs the above-mentioned filter bank 200, it is necessary that adjacent filter bands of BPF1 to BPFn overlap each other so that there is no band that cannot be measured. Moreover, this overlapping band needs to be wider than the band occupied by the signal under measurement or the test signal so that the signal under measurement or the test signal is not dropped out.

[0009] According to the above-mentioned configuration of the conventional filter bank 200, since a plurality of BPFs are mechanically switched, the switching time is long and the mechanical life for switching is limited. On the other hand, today, with the increasing demand for measuring faster signals such as 5G and millimeter wave bands, it is difficult for the filter bank 200, which uses a mechanical switch for switching, to support high-speed and high-precision switching of passbands.

[0010] One known filter technology that does not cause problems with switch switching time and life span is one in which a filter group is formed using a duplexer configuration that combines hybrid circuits that have no moving parts.

[0011] However, with a filter group having this splitter configuration, it was necessary to provide an appropriate guard band (a non-overlapping band area) so that adjacent filter bands in the filter group would not overlap. For this reason, a filter group having a splitter configuration with no moving parts could not be directly applied as a filter bank for a spectrum analyzer, which requires adjacent filter bands to overlap. In other words, even if a filter group having a conventional splitter configuration with no moving parts is directly applied to the front-end circuit of a spectrum analyzer, it is not possible to ensure overlap between adjacent filter bands because the splitter requires guard bands, resulting in bands that cannot be measured.

[0012] Therefore, for the front-end circuits of spectrum analyzers and test signal generators, there has traditionally been a strong demand for a configuration that uses a group of filters consisting of a splitter or multiplexer with no moving parts, capable of supporting smooth and highly accurate measurement of all bands without the problems of long switching times and life span that are associated with mechanical filter banks.

[0013] The present invention has been made to solve these problems in the related art, and has an object to provide a filter bank circuit that uses electronically switchable switches and a plurality of filter groups, and that is capable of measuring or testing all bands by ensuring overlap across the entire filter group by switching the filter groups with simple switching control while ensuring a guard band within each filter group, and a spectrum analyzer, signal analyzer, signal generator, and method of controlling the filter bank circuit that use the same. [Means for solving the problem]

[0014] In order to solve the above problems, a filter bank circuit according to claim 1 of the present invention includes a single-pole, n-throw changeover switch (20, 20-1) that switches between one input section (20a) and n (n is an integer of 2 or more) output sections (20b, 20c, 20d), and n groups of filters (G1 to Gn) that are connected to the n output sections, respectively, and each of the filter groups includes m (m is an integer of 2 or more) filter circuits (21, 22, 23), and each of the filter circuits is set to a passband that does not overlap with the passband of other filter circuits within the group and overlaps with the passband of each of the filter circuits of the other groups by a predetermined bandwidth (ol1 to ol7) between the groups, and the predetermined bandwidth is set to a band wider than a band occupied by the signal under measurement or the test signal so that the signal under measurement or the test signal is not dropped.

[0015] With this configuration, the filter bank circuit according to claim 1 of the present invention can maintain the overlap between the passbands of the filters in different groups while maintaining the guard band between the passbands of the filters in the filter groups by switching between the multiple filter groups for each group. This makes it possible to measure the signal under test or test the device under test for all bands with appropriate overlap bands, without the need for long switching times or complicated switching control as with a mechanically switched filter bank, by using a filter group that does not have a moving part.

[0016] Furthermore, the filter bank circuit according to claim 2 of the present invention may be configured to input predetermined frequency components, and extract the predetermined frequency components by dividing the input frequency components into n×m overlapping passbands using m filter circuits for each of the n groups.

[0017] With this configuration, the filter bank circuit according to claim 2 of the present invention has no bands that cannot be measured or tested for a signal to be measured or a test signal of a specified frequency component, and can extract frequency components from which unnecessary radio waves are suppressed by extremely simple switching control of the change-over switch in a short time.

[0018] In addition, in the filter bank circuit according to claim 3 of the present invention, the filter circuit may be configured as a filter bank using a branch line coupler (BLC) that passes frequency components of the pass band set corresponding to the filter circuit.

[0019] With this configuration, the filter bank circuit of claim 3 of the present invention employs a filter bank using a BLC and a band pass filter (BPF), which, together with the use of a change-over switch, enables the structure to be simplified and the cost to be reduced.

[0020] In addition, in the filter bank circuit according to claim 4 of the present invention, the filter circuit may be configured as a band pass filter (BPF) that passes frequency components of the pass band set corresponding to the filter circuit.

[0021] With this configuration, the filter bank circuit according to claim 4 of the present invention can easily realize each filter circuit in the filter group using a general-purpose band-pass filter, thereby simplifying the structure and reducing costs.

[0022] In the filter bank circuit according to claim 5 of the present invention, the filter circuits (41a, 41b, 41c, 42a, 42b, 42c) have an input port, an output port, and a transfer port, and a frequency component inputted from the input port is inputted to the filter. circuit a circulator (45a to 45f) for outputting the frequency component to the output port when the frequency component corresponds to the frequency pass band of the filter, and inputting the frequency component from the transfer port to the input port of the next stage when the frequency component is outside the frequency pass band; circuit and a band-pass filter (46a to 46f) in which the passband is set according to the frequency passband of the input signal.

[0023] With this configuration, the filter bank circuit according to claim 5 of the present invention can easily realize each filter circuit in the filter group using general-purpose circulators, low-pass filters, etc., thereby simplifying the structure and reducing costs.

[0024] In addition, in the filter bank circuit according to claim 6 of the present invention, the filter circuit may be configured by combining a high-pass filter (HPF) and a low-pass filter (LPF), and may be configured to pass frequency components of the passband set corresponding to the filter circuit.

[0025] With this configuration, the filter bank circuit according to claim 6 of the present invention can easily realize each filter circuit in the filter group using general-purpose high-pass filters and low-pass filters, thereby simplifying the structure and reducing costs.

[0026] In order to solve the above problems, a spectrum analyzer according to claim 7 of the present invention has a frequency conversion section (100) having a filter (113) that provides a signal under test of a predetermined frequency component to a mixer (111) together with a local signal output from a local signal generator (112) and extracts a signal of a predetermined intermediate frequency band from the mixed output, and a detector (120) that detects the signal of the intermediate frequency band, and changes the frequency of the local signal in response to an analysis target frequency to determine the spectrum characteristics of the signal under test, comprising: request The present invention is characterized in that the filter bank circuit (10) according to claim 1 is provided, and the filter bank circuit (10) has a switching control means (151) for controlling the changeover switch, to which the signal to be measured is inputted to the input section, so that the plurality of filter groups are repeatedly selected in order in group units according to the frequency to be analyzed, and for each of the filter groups which are repeatedly selected in order, frequency components passing through the filter circuit having the pass band corresponding to one frequency band of the frequency to be analyzed are sequentially extracted.

[0027] With this configuration, the spectrum analyzer according to claim 7 of the present invention can extract frequency components corresponding to multiple (n × m) overlapping passbands from the signal to be measured input to the filter bank circuit while suppressing unnecessary radio waves, and output the frequency components to the detector. By using a filter group that has no moving parts, it is possible to realize smooth measurement of the spectral characteristics of signals of all bands without the need for long switching times and complicated switching control as with a mechanically switched filter bank.

[0028] Furthermore, the spectrum analyzer according to claim 8 of the present invention may further include a plurality of local signal generators (112-1, 112-2) provided corresponding to the plurality of filter groups, respectively, mixers (111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, 111-8) provided corresponding to each of the filter circuits constituting the plurality of filter groups, and a local frequency setting means (152) for setting a local frequency for the mixer corresponding to the filter circuit having the pass band corresponding to the one frequency band in the filter group to be selected next when measuring the spectral characteristics by the filter circuit having the pass band corresponding to the one frequency band in the filter group currently being selected.

[0029] With this configuration, the spectrum analyzer according to claim 8 of the present invention can eliminate the unnecessary waiting time required to set the local frequency between the time when each filter circuit constituting a selected filter group is measured and the time when each filter circuit constituting the next filter group is measured, thereby enabling smooth measurement.

[0030] In order to solve the above problems, a signal analyzer 2 according to claim 9 of the present invention has a frequency conversion unit (100F) having a filter (113F) that supplies a signal under test of a predetermined frequency component to a mixer (111F) together with a local signal output from a local signal generator (112F) and extracts a signal of a predetermined intermediate frequency band from the mixed output, and a signal analysis unit (153F) that converts the signal of the intermediate frequency band into a digital signal by an ADC (125) and then analyzes the waveform of the signal, and in this signal analyzer (2) that changes the frequency of the local signal according to a frequency to be analyzed and analyzes the waveform of the signal under test, the signal analyzer (2) has a frequency conversion unit (100F) having a filter (113F) that supplies a signal under test of a predetermined frequency component together with a local signal output from a local signal generator (112F) to a mixer (111F) and extracts a signal of a predetermined intermediate frequency band from the mixed output, and requestThe present invention is characterized in that the filter bank circuit (10) according to claim 1 is provided, and a switching control means (151F) is provided for controlling the changeover switch, to which the signal to be measured is inputted to the input section, so that a plurality of the filter groups are selected in group units according to the frequency to be analyzed, and for each of the selected filter groups, a frequency component passing through the filter circuit having the passband corresponding to one frequency band of the frequencies to be analyzed is extracted, and the waveform of the signal of the frequency component is analyzed after converting it from an analog signal to a digital signal.

[0031] With this configuration, the signal analyzer according to claim 9 of the present invention can extract frequency components corresponding to multiple (n × m) overlapping passbands from the signal under test input to the filter bank circuit, with unnecessary radio waves suppressed, and output the extracted frequency components to the ADC, with overlapping bands secured so that the signal under test is not lost. By using a filter group that has no moving parts, it is possible to smoothly and accurately realize signal analysis targeting signals of all bands, without the need for long switching times or complicated switching control as with a mechanically switched filter bank.

[0032] In order to solve the above problems, a signal generating device 3 according to claim 10 of the present invention has a frequency conversion unit (100E) that provides a test signal in an intermediate frequency band output from a signal generating unit (130) to a mixer (111E) together with a local signal output from a local signal generator (112E) to convert the signal into a millimeter wave band signal, changes the frequency of the local signal according to a test frequency for testing a device under test (DUT), and transmits the signal after the frequency conversion by the frequency conversion unit as the test signal for the device under test, wherein the signal after the frequency conversion is input to a stage subsequent to the frequency conversion unit. request The filter bank circuit (10E) according to claim 1 is provided, and the changeover switch has a configuration in which the n output units function as input units (20b1, 20c1) and the one input unit functions as an output unit (20a1), and a filter bank circuit (10E) corresponding to one frequency band of the test target frequencies is provided. GeneralThe present invention is characterized in that it has a switching control means (151E) for switching and controlling the change-over switch to which the frequency-converted signal is input to the input section so that the filter group having the filter circuit having a transmission band is selected, and the test signal is sent from the selected filter group.

[0033] With this configuration, the signal generating device according to claim 10 of the present invention can extract frequency components corresponding to multiple (n × m) overlapping passbands from the frequency-converted signal input to the filter bank circuit, with unnecessary radio waves suppressed, and send them as test signals, with overlapping bands secured so that the test signal is not lost.By using a filter group that has no moving parts, it is possible to smoothly test the device under test for signals of all bands without the need for long switching times and complicated switching control as with a mechanically switched filter bank.

[0034] In order to solve the above problem, a control method for a filter bank circuit according to claim 11 of the present invention is a control method for a filter bank circuit in a spectrum analyzer, a signal analyzer, or a signal generator that uses the filter bank circuit (10) according to claim 1, and is characterized in that it includes a setting step (S1, S11) of setting an analysis target frequency or a test target frequency, a step (S2, S12) of calculating the filter circuit to be selected from the filter group based on the set analysis target frequency or test target frequency, a step (S5, S13) of setting a path of the change-over switch corresponding to the filter circuit to be selected and controlling the change-over switch to select the filter group to which the selected filter circuit belongs, and a step (S5, S7, S9, S14) of measuring, or extracting for analysis, or for sending a test signal, a frequency component that passes through the filter circuit calculated in the calculation step, from the filter group switched by the change-over control step.

[0035] With this configuration, the filter bank circuit control method of claim 11 of the present invention, when the filter bank circuit is mounted on a spectrum analyzer, or a signal analyzer, or a signal generator, can divide the frequency range to be analyzed or the frequency to be tested into multiple (n × m) overlapping passbands, and extract the frequency components of each passband from the signal to be measured or the test signal while suppressing unnecessary radio waves.By simply controlling the switching of the switch, it is possible to eliminate bands in which signals cannot be measured, analyzed, or tested, and also to shorten the switching time of the switch. Effect of the Invention

[0036] The present invention can provide a filter bank circuit that uses an electronically switchable switch and a plurality of filter groups, and can respond to measurement or testing of all bands by switching the filter groups with simple switching control while ensuring a guard band within each filter group, thereby ensuring overlap across the entire filter group, as well as a spectrum analyzer, signal analyzer, signal generator, and filter bank circuit control method that use the same. [Brief description of the drawings]

[0037] [Figure 1] FIG. 2 is a configuration diagram of a filter bank circuit according to an embodiment of the present invention. [Diagram 2] 2 is a schematic diagram showing the passbands of filters constituting a filter group of a filter bank circuit according to an embodiment of the present invention; FIG. [Diagram 3] 4 is a graph showing the frequency characteristics of each filter constituting a filter group of a filter bank circuit according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing a general configuration of a spectrum analyzer using a filter bank circuit according to an embodiment of the present invention. [Diagram 5] 1 is a diagram showing a configuration of a main part of a filter bank circuit including a local signal supply path in a spectrum analyzer using a filter bank circuit according to an embodiment of the present invention; [Figure 6] FIG. 11 is a diagram showing the operation timing when a spectrum analyzer using a filter bank circuit according to an embodiment of the present invention measures a signal, where (a) shows the switching operation of a changeover switch, and (b) shows the local signal setting operation for one local signal generator. [Figure 7] 5 is a flowchart showing a signal measurement control operation in a spectrum analyzer using a filter bank circuit according to an embodiment of the present invention. [Figure 8] FIG. 11 is a block diagram showing a configuration including a main portion of a local signal supply path of a filter bank circuit according to a first modified example of the present invention. [Figure 9] FIG. 11 is a diagram showing the operation timing when a spectrum analyzer using a filter bank circuit according to the first modification of the present invention measures a signal, where (a) shows the switching operation of a changeover switch, and (b) shows the setting operation of local signals for each of two local signal generators. [Figure 10] 10 is a flowchart showing a signal measurement control operation in a spectrum analyzer that uses a filter bank circuit according to the first modified example of the present invention. [Figure 11] FIG. 11 is a diagram showing a configuration of a filter bank circuit according to a second modified example of the present invention. [Figure 12] FIG. 11 is a diagram showing a configuration of a filter bank circuit according to a third modified example of the present invention. [Figure 13] 1 is a diagram showing the configuration of a signal analyzer using a filter bank circuit according to an embodiment of the present invention; [Figure 14] 1 is a diagram showing a configuration of a signal generating device using a filter bank circuit according to an embodiment of the present invention; [Figure 15] 1 is a configuration diagram of a filter bank circuit of a signal generating device using a filter bank circuit according to an embodiment of the present invention. [Figure 16] 5 is a flowchart showing a signal transmission control operation in a signal generating device using a filter bank circuit according to an embodiment of the present invention. [Figure 17]FIG. 1 is a diagram showing a configuration of a filter bank provided in a front-end circuit of a conventional spectrum analyzer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, a filter bank circuit according to the present invention, a spectrum analyzer, a signal analyzer, a signal generator, and a method of controlling the filter bank circuit using the same will be described.

[0039] (overview) The filter bank circuit 10 according to the present invention corresponds to the filter bank circuits 10A, 10B, 10C, 10D, and 10E according to the embodiments and modifications described below, and receives a signal of a predetermined frequency component, and extracts and outputs only a signal of a frequency component in a desired frequency band while suppressing unnecessary radio waves, i.e., spurious waves, contained in the input signal. The filter bank circuit 10 is provided in a front-end circuit 101 of a spectrum analyzer (see FIG. 4) that measures the distribution (spectrum) of frequency components contained in a high-frequency signal, a signal analyzer (see FIG. 13) that analyzes the waveform of the frequency components contained in a high-frequency signal, and a signal generator (see FIG. 14) that generates a test signal for a receiving sensitivity test of a device under test (DUT). The above-mentioned predetermined frequency component that the filter bank circuit 10 according to the present invention can handle is, for example, a sub-terahertz region of 100 GHz or more and less than 1 THz.

[0040] The filter bank circuit 10 according to the present invention has a plurality (e.g., n) groups of filter groups G1 to Gn, each of which has a plurality (e.g., m) of filters (corresponding to filters 21a, 21b, 21c, 22a, 22b, 22c, 23a, 23b, and 23c in the following embodiment), and further has a single-pole, n-throw changeover switch 20 (see FIG. 1) that switches the connection between one input section 20a that inputs an input signal (signal under measurement) and n output sections 20b, 20c, 20d, ... to which the filter groups G1 to Gn are respectively connected. By controlling the changeover switch 20 so that the input section 20a is sequentially connected to the n output sections 20b, 20c, 20d, ..., the signal under measurement can be selectively supplied to each of the filter groups G1 to Gn through each of the output sections 20b, 20c, 20d, ....

[0041] Within each of the filter groups G1 to Gn, the filter bands (passbands) of the m filters are set to frequency bands (non-overlapping frequency bands) that ensure a guard band, while between the groups, the passbands are set so that filters in the same order in each group overlap each other.

[0042] According to the filter bank circuit 10 of the present invention having the above configuration, for example, when an input signal is switched in sequence from the filter group G1 to the filter groups G2, G3, G4, ..., it is possible to maintain the overlap of the passbands between the alternately ordered filters among the filters arranged in the order of 1 to n in each of the filter groups G1, G2, G3, G4, ..., and to ensure the guard bands between the adjacent filters of each of the filter groups G1, G2, G3, G4, .... Therefore, according to a configuration in which the filter bank circuit 10 of the present invention is provided in the front-end circuit 101 of a spectrum analyzer, a signal analyzer, or a signal generator, it is easier to control the switching of the filter groups G2, G3, G4, ..., and the switching time can be shortened, in addition to which rapid and highly accurate measurement or testing of high-frequency components with suppressed spurious waves can be realized, compared to a conventional device using a mechanically switched filter bank (see FIG. 17).

[0043] In the following, an embodiment of a filter bank circuit 10 (10A) according to the present invention (see FIGS. 1 to 3), an embodiment of a spectrum analyzer 1 using the filter bank circuit 10 (10A) (see FIGS. 4 to 7), an embodiment of a spectrum analyzer 1 using a filter bank circuit 10B according to Modification 1 (see FIGS. 8 to 10), an embodiment of a filter bank circuit 10C according to Modification 2 (see FIG. 11), an embodiment of a filter bank circuit 10D according to Modification 3 (see FIG. 12), an embodiment of a signal analyzer 2 using the filter bank circuit 10A (see FIG. 13), and an embodiment of a signal generating device 3 using the filter bank circuits 10A, 10B, 10C, and 10D as the filter bank circuit 10E (see FIGS. 14 to 16) will be described in order.

[0044] In the following embodiments, for convenience, up to three filter groups (filter groups G1, G2, G3), up to three filters in each of filter groups G1, G2, G3, and frequency bands in the range of f1 to f12 are disclosed; however, the number of filter groups, filters in a filter group, and frequency bands can be any number n, m, or (n×(m+1)), as described above.

[0045] (Filter bank circuit 10A according to one embodiment) Fig. 1 shows the configuration of a filter bank circuit 10A according to an embodiment of the present invention. As shown in Fig. 1, the filter bank circuit 10A according to the present embodiment includes a changeover switch 20, a first filter group G1, and a second filter group G2.

[0046] The changeover switch 20 has one input section 20a and two output sections 20b and 20c, and is configured as a single-pole / double-throw switch (SPDT SW) that electronically switches the connection between the input section 20a and one of the two output sections 20b and 20c. The changeover switch 20 is configured so that the above-mentioned signal to be measured is input to the input section 20a. The output sections 20b and 20c are connected to the first filter group G1 and the second filter group G2, respectively. As a result, the changeover switch 20 outputs the signal to be measured to the first filter group G1 by controlling switching so that the input section 20a and the output section 20b are connected, and outputs the signal to be measured to the second filter group G2 by controlling switching so that the input section 20a and the output section 20c are connected.

[0047] In the changeover switch 20, the first filter group G1 has a plurality of filters 21a, 21b, and 21c that do not overlap with each other, that is, have frequency bands (hereinafter, bands) f1, f3, f5, and f7 as their passbands, respectively, that can secure guard bands for each other. In the following description, the filters 21a, 21b, and 21c may be collectively referred to as the filter 21.

[0048] On the other hand, the second filter group G2 has a plurality of filters 22a, 22b, and 22c whose passbands are bands f2, f4, f6, and f8 that do not overlap with each other and can secure guard bands for each other. In the following description, the filters 22a, 22b, and 22c may be collectively referred to as filter 22. The filters 21a, 21b, and 21c and the filters 22a, 22b, and 22c, together with filters 23a, 23b, and 23c (see FIG. 11) and filters 41a, 41b, 41c, 42a, 42b, and 42c (see FIG. 12), which will be described later, constitute a filter circuit of the present invention.

[0049] In the first filter group G1, the filters 21a, 21b, and 21c have different filter characteristics but the same circuit structure, and each of them has an input-side hybrid 25a1, 25b1, and 25c1, an output-side hybrid 26a1, 26b1, and 26c1, and two BPFs 27a1, 27b1, and 27c1 connected in parallel between the hybrids 25a1, 25b1, and 25c1 and the hybrids 26a1, 26b1, and 26c1. That is, the filters 21a, 21b, and 21c (as well as the filters 22a, 22b, and 22c described later) are configured as a filter bank using branch-line couplers (BLCs) (=hybrids 25a1, 25b1, 25c1, 26a1, 26b1, and 26c1). Here, the passband of the BPF 27a1 of the filter 21a is set to band f1, the passband of the BPF 27b1 of the filter 21b is set to band f3, and the passband of the BPF 27c1 of the filter 21c is set to band f5.

[0050] In filter 21a, the signal under test coming from the input-side hybrid 25a1 is input to the BPF 27a1, which passes frequency components of band f1 and outputs them from the output-side hybrid 26a1 to the frequency conversion section (see frequency conversion section 100 in FIG. 4), while allowing other frequency components to be input to the input-side hybrid 25b1 of the next-stage filter 21b via the input-side hybrid 25a1.

[0051] Filter 21b inputs the frequency components input from the input-side hybrid 25b1 to the BPF 27b1, and the BPF 27b1 passes frequency components of band f3 and outputs them from the output-side hybrid 26b1 to the frequency conversion section, while inputting other frequency components via the input-side hybrid 25b1 to the input-side hybrid 25c1 of the next-stage filter 21c.

[0052] Filter 21c inputs the frequency components input from the input-side hybrid 25c1 to BPF 27c1, which passes the frequency components of band f5 and outputs them from the output-side hybrid 26c1 to the frequency conversion section, while passing the frequency components of band f7 through the input-side hybrid 25c1 and outputting them to the frequency conversion section.

[0053] As for the second filter group G2, the filters 22a, 22b, and 22c each have a hybrid 25a2, 25b2, and 25c2 on the input side, a hybrid 26a2, 26b2, and 26c2 on the output side, and two BPFs 27a2, 27b2, and 27c2 connected in parallel between the hybrids 25a2, 25b2, and 25c2 and the hybrids 26a2, 26b2, and 26c2. The filters 22a, 22b, and 22c are also configured as a filter bank using BLC. Here, the BPF 27a2 of the filter 22a is set to a passband of band f2, the BPF 27b2 of the filter 22b is set to a passband of band f4, and the BPF 27c2 of the filter 22c is given a passband of band f6.

[0054] The filter 22a inputs the signal under test received from the hybrid 25a2 on the input side to the BPF 27a2, which passes frequency components of band f2 and outputs them from the hybrid 26a2 on the output side to the frequency conversion section, while allowing other frequency components to pass through the hybrid 25a2 on the input side and be input to the hybrid 25b2 on the input side of the next-stage filter 22b.

[0055] The filter 22b inputs the frequency components input from the input-side hybrid 25b2 to the BPF 27b2, and the BPF 27b2 passes frequency components of band f4 and outputs them from the output-side hybrid 26b2 to the frequency conversion section, while inputting other frequency components via the input-side hybrid 25c2 to the input-side hybrid 25c2 of the next-stage filter 22c.

[0056] The filter 22c inputs the frequency components input from the input-side hybrid 25c2 to the BPF 27c2, which passes the frequency components of band f6 and outputs them from the output-side hybrid 26c2 to the frequency conversion section, while passing the frequency components of band f8 through the input-side hybrid 25c2 and outputting them to the frequency conversion section.

[0057] In this way, in the filter bank circuit 10A, the filters 21a, 21b, and 21c constituting the first filter group G1 and the filters 22a, 22b, and 22c constituting the second filter group G2 are configured to extract, by switching control of the change-over switch 20, the frequency components of bands f1, f3, f5, and f7 and the frequency components of bands f2, f4, f6, and f8 from the signal under test input to the input section 20a of the change-over switch 20, for each group, and output them to the frequency conversion section (see frequency conversion section 100 in Figure 4).

[0058] Next, the filter characteristics of the filters 21a, 21b, and 21c constituting the first filter group G1 and the filters 22a, 22b, and 22c constituting the second filter group G2 will be described. Fig. 2 is a diagram showing the passbands of the filters 21a, 21b, and 21c and the filters 22a, 22b, and 22c divided into two groups (filter groups G1 and G2) in the filter bank circuit 10A according to this embodiment, where (a) shows the passbands of the filters 21a, 21b, and 21c constituting the first filter group G1, (b) shows the passbands of the filters 22a, 22b, and 22c constituting the second filter group G2, and (c) shows the passbands covered by both the first filter group G1 and the second filter group G2.

[0059] As shown in Fig. 2(a), the filters 21a, 21b, 21c, and 21c+1 constituting the first filter group G1 have filter characteristics (passbands) that pass adjacent non-overlapping frequency bands (bands) f1, f3, f5, and f7. The filters 22a, 22b, 22c, and 22c+1 constituting the second filter group G2 have passbands that pass adjacent non-overlapping frequency bands f2, f4, f6, and f8 as shown in Fig. 2(b). Here, for convenience, the filter 21c+1 refers to the filter portion of the filter 21c in Fig. 1 that passes the components of the band f7, and the filter 22c+1 refers to the filter portion of the filter 22c that passes the components of the band f8.

[0060] In Figures 2(a) and (b), the frequency bands (bands) f1, f3, f5, f7, and f2, f4, f6, f8 that can be passed by the filters 21a, 21b, 21c, 21c+1 and the filters 22a, 22b, 22c, 22c+1 have, for example, equal bandwidths on both the high-frequency and low-frequency sides of the center frequency of each band.

[0061] FIG. 2(c) shows the passbands of the filters 21a, 21b, 21c, and 21c+1 that constitute the first filter group G1 and the passbands of the filters 22a, 22b, 22c, and 22c+1 that constitute the second filter group G2.

[0062] As shown in FIG. 2(c), in the filter bank circuit 10A according to this embodiment, between each filter 21a, 21b, 21c of the first filter group G1 and each filter 22a, 22b, 22c of the second filter group G2, the passbands are set so that filter 21a and filter 22a, filter 22a and filter 21b, filter 21b and filter 22b, filter 22b and filter 21c, filter 21c and filter 22c, filter 22c and filter 21c+1, and filter 21c+1 and filter 22c+1 have mutually overlapping passbands (overlap regions) ol1, ol2, ol3, ol4, ol5, ol6, ol7, ...

[0063] Here, assuming that the filter groups G1 and G2 are the first and second group, and the arrangement order of the filters 21 and 22 in the filter groups G1 and G2 is the first to fourth from the left side of FIG. 3, the first filter 21a in the first group and the first filter 22a in the second group, the first filter 22a in the second group and the second filter 21b in the first group, the second filter 21b in the first group and the second filter 22b in the second group, the second filter 21b in the first group and the second filter 22b in the second group, the second filter 21a in the second group and the second filter 22b in the second group, the second filter 21b in the first group and the second filter 22b in the second group, the second filter 21b in the second group and the second filter 22b in the second group, the second filter 21a in the first ... The passbands ol1, ol2, ol3, ol4, ol5, ol6, and ol7 of filter 22b and the third filter 21c in the first stage group, the third filter 21c in the first stage group and the third filter 22c in the second stage group, the third filter 22c in the second stage group and the fourth filter 21c+1 in the first stage group, and the fourth filter 21c+1 in the first stage group and the fourth filter 22c+1 in the second stage group are configured so that they overlap with each other.

[0064] Table 1 below shows an example of specifications including passbands of the filters 21a, 21b, 21c, 21c+1 and the filters 22a, 22b, 22c, 22c+1 described with reference to Figures 2(a) and 2(b). Table 2 below shows an example of specifications regarding overlapping bands between the filters 21a, 22a, 21b, 22b, 21c, 22c, 21c+1, 22c+1 described with reference to Figure 2(c). [Table 1] [Table 2]

[0065] Fig. 3 shows a specific example of the frequency characteristics of the filters 21a, 21b, 21c, 21c+1, 22a, 22b, 22c, and 22c+1 constituting the first filter group G1 and the second filter group G2 shown in Fig. 2. Fig. 3 shows an example of pass characteristics when the frequency range from 255 GHz to 325 GHz is divided into eight bands and these eight bands are assigned to the filter 21a of the first filter group G1, the filter 22a of the second filter group G2, the filter 21b of the first filter group G1, the filter 22b of the second filter group G2, the filter 21c of the first filter group G1, the filter 22c of the second filter group G2, the filter 21c+1 of the first filter group G1, and the filter 22c+1 of the second filter group G2, in that order.

[0066] 3, filter 21a has a pass band of, for example, 253-264 GHz and a center frequency of 258 GHz, and overlaps with filter 22a in a frequency band of, for example, 260-264 GHz. Filter 22a has a pass band of, for example, 260-272 GHz and a center frequency of 267 GHz, and overlaps with filter 21a under the above-mentioned conditions, and overlaps with filter 21b in a frequency band of, for example, 268-272 GHz. Filter 21b has a pass band of, for example, 268-281 GHz and a center frequency of 274 GHz, and overlaps with filter 22a under the above-mentioned conditions, and overlaps with filter 22b in a frequency band of, for example, 276-281 GHz. Filter 22b has, for example, a passband of 276-288 GHz and a center frequency of 282 GHz, overlapping with filter 21b under the above-mentioned conditions and overlapping with filter 21c in the frequency band of, for example, 285-288 GHz.

[0067] Moreover, the filter 21c has a pass band of, for example, 285-295 GHz, a center frequency of 290 GHz, overlaps with the filter 22b under the above-mentioned conditions, and overlaps with the filter 22c in the frequency band of, for example, 292-295 GHz. The filter 22c has a pass band of, for example, 292-305 GHz, a center frequency of 298 GHz, overlaps with the filter 21c under the above-mentioned conditions, and overlaps with the filter 21c+1 in the frequency band of, for example, 300-305 GHz. The filter 21c+1 has a pass band of, for example, 300-312 GHz, a center frequency of 306 GHz, overlaps with the filter 22c under the above-mentioned conditions, and overlaps with the filter 22c+1 in the frequency band of, for example, 308-313 GHz. Filter 22c+1 has a passband exceeding 308, a center frequency of 320 GHz, and overlaps with filter 21c+1 under the conditions described above.

[0068] According to the configuration of the filter bank circuit 10A including filters 21a, 21b, 21c, and 21c+1 constituting the first filter group G1 having the passband characteristics shown in FIG. 3, and filters 22a, 22b, 22c, and 22c+1 constituting the second filter group G2, by controlling the changeover switch 20 to switch over the frequency band between the passband of filter 21a constituting the first filter group G1 and the passband of filter 22c+1 constituting the second filter group G2, it is possible to cover measurements targeting all of these frequency bands while overlapping adjacent bands f1, f2, f3, f4, f5, f6, f7, and f8 with each other, as shown in FIG. 2(c). For example, it is possible to eliminate frequency bands whose spectrum characteristics cannot be measured in the millimeter wave band.

[0069] (Spectrum analyzer 1 using filter bank circuit 10A) 4 is a diagram showing a general configuration of a spectrum analyzer 1 that uses the above-mentioned filter bank circuit 10 A. The spectrum analyzer 1 is assumed to have a function of analyzing signals in the millimeter wave band.

[0070] This spectrum analyzer 1 has a frequency conversion section 100, a detector 120, a control section 150, an operation section 160, and a display section 161, and further includes the above-mentioned filter bank circuit 10A in the preceding stage of the frequency conversion section 100.

[0071] The frequency conversion section 100 is configured to include a mixer 111, a local signal generator 112, and a filter 113.

[0072] Mixer 111 is a functional unit that functions as a frequency conversion means for converting the signal under test from an RF frequency to an intermediate frequency signal (IF frequency) and outputting the signal by mixing a signal of each frequency component (RF frequency) in which spurious waves are suppressed and output from filter bank circuit 10A with a local signal input from local signal generator 112.

[0073] Local signal generator 112 generates a local signal to be sent to mixer 111 based on a local signal (reference signal) input from local oscillation signal source 9 .

[0074] Filter 113 is a filter function unit that inputs the IF signal that has been frequency converted by mixer 111, passes only signals of frequency components in a certain preset band of the input IF signal, and inputs them to detector 120.

[0075] The detector 120 is a processing circuit that detects the intensity of the signal (IF) of each band that is input after passing through the filter 113 .

[0076] The control unit 150 has a control function for comprehensively controlling the entire spectrum analyzer 1 including the filter bank circuit 10A, as well as a filter switching control unit 151, a frequency sweep control unit 152, and a spectrum data acquisition unit 153.

[0077] The filter switching control section 151 electronically switches and controls the connection between one pole (input section) and two throws (output sections) of, for example, a single-pole, double-throw type changeover switch 20 (see FIG. 1) provided in the filter bank circuit 10A. The filter switching control section 151 constitutes the switching control means of the present invention.

[0078] The frequency sweep control unit 152 is a functional unit that executes frequency sweep control for changing the frequency of the local signal that the local signal generator 112 outputs to the mixer 111 within a specified frequency range, based on the local signal (reference signal) input from the local oscillation signal source 9. The frequency sweep control unit 152 constitutes a local frequency setting means of the present invention.

[0079] The spectrum data acquisition unit 153 is a part that acquires spectrum data including the intensity of a signal component of a desired frequency band within the analysis target frequency range detected by the detector 120, and performs display control on the display unit 161, etc.

[0080] The operation unit 160 has input means such as various keys, switches, buttons, etc., and is operated by the user when making various settings related to the measurement of the signal under measurement, etc. The display unit 161 is composed of, for example, a liquid crystal display, and is a functional unit that displays a setting screen related to the measurement of the signal under measurement, measurement results, etc.

[0081] In the spectrum analyzer 1 shown in Fig. 4, a signal under test (input signal) in the millimeter wave band is provided to a mixer 111 of a frequency conversion unit 100 via a filter bank circuit 10A, mixed with a local signal output from a local signal generator 112, and a signal in a predetermined intermediate (IF) frequency band is extracted from the mixed output by a filter 113. The frequency of the local signal is swept and variably adjusted by a frequency sweep control unit 152 of a control unit 150 in accordance with a desired frequency range to be analyzed, and a signal component in the desired frequency range to be analyzed is extracted as an intermediate frequency band signal over time, and its intensity is detected by a detector 120. Note that, for ease of explanation, an example in which the frequency conversion process (heterodyne conversion) of the frequency conversion unit 100 is performed only once is shown here, but in order to accurately analyze a high-frequency signal such as the millimeter wave band, the frequency conversion process is performed multiple times to convert the signal into an intermediate frequency band that can be digitally processed.

[0082] In the control unit 150, the spectrum data acquisition unit 153 stores the signal intensity detected by the detector 120 for each analysis target frequency as spectrum data, for example, in accordance with the analysis target frequency set by the operation unit 160, and causes the display unit 161 to display this.

[0083] At this time, the filter switching control unit 151 controls the switching switch 20 in the filter bank circuit 10A in accordance with the frequency to be analyzed, and performs switching control to switch the filter groups G1 and G2 to the group to which the filter 21 or filter 22 belongs, the group having a passband that includes the frequency to be analyzed.

[0084] In addition, the frequency sweep control unit 152 performs sweep control of the frequency corresponding to the passband of the filter 21 or filter 22 selected according to the frequency to be analyzed at that time, in accordance with the switching control of the filter groups G1, G1 by the filter switching control unit 151.

[0085] In the configuration of the spectrum analyzer 1 shown in FIG. 4, the signal under test (RF Input) as the input signal to the front-end circuit 101 is, for example, a signal in the frequency range of 255 to 315 GHz (f RF ), and the signal under test (IF Output) as the output signal is, for example, a signal in the frequency range of 23 to 31 GHz (f IF That is, the spectrum analyzer 1 according to this embodiment is capable of taking in, for example, a signal received from a mobile phone (5G, LTE, XG-PHS, W-CDMA, CDMA2000, GSM, etc.) or various wireless communications (WLAN, Bluetooth, GPS, ISDBT, etc.) as an input signal (RF Input), suppressing spurious waves by the filter bank circuit 10 in the front-end circuit 101, and then measuring the spectrum characteristics of each desired frequency component.

[0086] In FIG. 4, the control unit 150 may be a control unit of the main body of the spectrum analyzer 1, or may be configured as a separate device such as a PC (personal computer).

[0087] In the spectrum analyzer 1 configured in this manner, the filter groups G1 and G2 are electronically switched by controlling the changeover switch 20, and therefore the switching time is short and the life of the switching device is long compared to a mechanical switching configuration. In this case, the multiple filters 21 and 22 constituting the filter groups G1 and G2 have passbands that do not overlap within the group but have overlapping passbands between the groups, so that the overlap between the passbands of the filters of the different groups of filter groups G can be maintained by switching between the multiple groups of filter groups (abbreviated as G) while maintaining the guard bands between the bands. This makes it possible to support smooth spectrum measurement of all bands by using multiple filter groups G that do not have moving parts, without the need for long switching times and complicated switching control as with a mechanically switched filter bank.

[0088] A more detailed description will be given of the configuration of the spectrum analyzer 1. Fig. 5 shows the configuration of the main part of the filter bank circuit 10A, which is included in the configuration of the spectrum analyzer 1 using the filter bank circuit 10A shown in Fig. 4, and in particular takes into account the local signal supply path.

[0089] In the spectrum analyzer 1 (see FIG. 4) having a filter bank circuit 10A in the front-end circuit 101, as described above, the frequency components that have passed through each of the filters 21a, 21b, and 21c of the first filter group G1 or each of the filters 22a, 22b, and 22c of the second filter group G2 in the filter bank circuit 10A are then input to the mixer 111 and frequency converted to an IF frequency.

[0090] In order to accommodate this frequency conversion, the spectrum analyzer 1 of this embodiment is equipped with, for example, one local signal generator 112 associated with the filter bank circuit 10A, as shown in FIG. 5, and mixers 111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, and 111-8 corresponding to bands f1, f2, f3, f4, f5, f6, f7, and f8, respectively, that pass through the filter bank circuit 10A. In the spectrum analyzer 1, when measuring a signal, the frequency components that have passed through the first filter group G1 or the second filter group G2 in the filter bank circuit 10A and the local signal generated by the local signal generator 112 in accordance with the frequency components that have passed are mixed in mixers 111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, and 111-8, respectively, and sent to the downstream detector 120 as a measured signal converted to an intermediate frequency.

[0091] At that time, the filter switching control unit 151 performs switching control of the changeover switch 20 of the filter bank circuit 10A, and the frequency sweep control unit 152 performs frequency sweep control to cause the local signal generator 112 to generate a local frequency corresponding to the frequency component that has passed through the first filter group G1 or the second filter group G2.

[0092] 6 is a timing chart showing the operation of the filter bank circuit 10A during signal measurement by the spectrum analyzer 1 according to this embodiment, where (a) shows the switching operation of the changeover switch 20 ("SPDT SW control") and (b) shows the setting operation of a local signal for the local signal generator 112 ("LO frequency setting"). As shown in FIG. 6(a), regarding the switching control of the changeover switch 20, the filter switching control unit 150 alternately switches from the first filter group G1 (f1, f3, f5, f7 route) to the second filter group G2 (f2, f4, f6, f8 route) and switches from the second filter group G2 to the first filter group G1 at the timings shown by the dotted vertical lines. The control unit 150 controls the frequency sweep control unit 152 to set a local signal for the signal generator 112 ("LO setting") and then measure the frequency based on that setting ("f1 measurement", etc.) in accordance with the alternating switching between the first filter group G1 and the second filter group G2, so that this pattern is repeatedly performed in the order of, for example, bands f1, f2, f3, ....

[0093] When the measurement operation control based on the operation timing shown in Fig. 6(a) is viewed from the viewpoint of the setting operation of the local signal for local signal generator 112, it becomes as shown in Fig. 6(b). In this case, since there is one local signal generator 112, the operation timing is such that the operations of setting the local frequency ("LO setting"), subsequently measuring band f1 ("f1 measurement"), then setting the local frequency ("LO setting"), subsequently measuring band f2 ("f2 measurement") are performed in order for the desired frequencies (for example, in the order of f1, f2, f3, f4, ...).

[0094] By controlling the "SPDT SW control" and "LO frequency setting" shown in Figure 6, the operation of measuring the corresponding frequency after setting the LO is repeated, but there is no overlap of the passband within the f1, f3, f5, f7 route and the f2, f4, f6, f8 route, and it is possible to perform measurements while maintaining the overlap of the passband between the f1, f3, f5, f7 route and the f2, f4, f6, f8 route.

[0095] Based on the above-mentioned flow of the switching control of the changeover switch 20 (see FIG. 6(a)) and the LO frequency setting control (see FIG. 6(b)), next, the signal measurement control operation in the spectrum analyzer 1 according to this embodiment will be described with reference to the flowchart shown in FIG.

[0096] In this example, the spectrum analyzer 1 receives a signal under test in the millimeter wave band (255 to 315 GHz band), extracts signals in a predetermined desired frequency band, for example, bands f1, f2, f3, f4, f5, f6, f7, and f8 from the signal under test using filters 21a, 21b, 21c, 22a, 22b, and 22c in the filter bank circuit 10A, converts the extracted frequency components to IF frequencies, and then inputs them to the detector 120 to measure the frequency spectrum. The spectrum is then measured, and the measurement results are displayed on the display unit 161.

[0097] To perform the above measurement operation, the user performs an operation to set the sweep frequency range (analysis target frequency range) of the spectrum analyzer 1 on the operation unit 160 (step S1). The parameters to be set here include, for example, a center frequency and a sweep frequency span, a start frequency and a stop frequency, and a start frequency and a sweep frequency span.

[0098] Next, the control unit 150 calculates a filter (in this example, filters 21a, 21b, and 21c (hereinafter referred to as filters 21), and 22a, 22b, and 22c (hereinafter referred to as filters 22) to be selected from the sweep frequency range set in step S1 and an LO setting (local frequency setting condition) (step S2). Here, if multiple filters are to be selected, the control unit 150 calculates an LO setting for each of the filters 21 and 22.

[0099] Subsequently, the control unit 150 determines whether a single filter 21 or a plurality of filters 22 are to be selected (step S3).

[0100] Here, if it is determined that a single filter 21 or filter 22 is to be selected (step S3: "single"), the control unit 150 sets the path of the changeover switch 20 corresponding to the path of that filter 21 or filter 22, and also sets the local frequency (LO frequency) (step S41).

[0101] Next, in the control section 150, the filter switching control section 150 controls the changeover switch 20 to switch between the first filter group G1 and the second filter group G2 based on the path setting in step S41, and accordingly, the frequency sweep control section 152 controls the frequency sweep for the local signal generator 112 based on the LO setting in step S41 while performing measurement on the filter 21 or filter 22 (step S42). If a single filter 21 or filter 22 is selected, the above measurement operation is terminated, and a determination is made as to whether or not the measurement is to be performed in continuous mode in step S10, and if it is not to be performed, the process is terminated.

[0102] On the other hand, if it is determined that a plurality of filters 21, 22 are to be selected ("multiple" in step S3), control unit 150 performs processing from step S4 onwards. First, control unit 150 sets the LO frequency corresponding to the filter to be selected first (for example, filter 21) in local signal generator 112 (step S4).

[0103] Next, the control unit 150 sets a path of the changeover switch 20 corresponding to the filter 21 that is selected first, and performs measurement with the filter 21 that is selected first (step S5).

[0104] Thereafter, control unit 150 waits until the measurement is completed in step S5, and sets the LO frequency corresponding to filter 22 to be selected secondly in local signal generator 112 (step S6).

[0105] Subsequently, the control unit 150 sets a path of the changeover switch 20 corresponding to the second selected filter 22, and performs measurement with the second selected filter 22 (step S7).

[0106] When the measurement in step S7 is completed, the control unit 150 checks whether there is a next filter 21 to be selected (step S8).

[0107] If it is determined that there is no filter 21, 22 to be selected next (NO in step S8), the control unit 150 advances the process to step S10.

[0108] On the other hand, if it is determined that there is a filter 21, 22, ... to be selected next (YES in step S8), the control unit 150 repeatedly performs the processes equivalent to the above steps S6 and S7 (processing performed by replacing "2nd" with "nth") for the next filter 21, 22, ... to be selected (step S9) until there is no filter 21, 22, ... to be selected next. Then, if it is determined that there is no filter 21, 22, ... to be selected next during this repeated process (NO in step S8), the control unit 150 proceeds to the process of step S10.

[0109] In step S10, the control unit 150 checks whether or not continuous measurement is set. If continuous measurement is set (YES in step S10), the control unit 150 returns to step S3 and continues the process from step S3 onward. On the other hand, if continuous measurement is not set (NO in step S10), the control unit 150 ends the series of measurement operation controls described above.

[0110] In the series of measurement operations shown in FIG. 7, the first selected filter 21 (step S5), the second selected filter 22 (step S7), the next selected filter 21, and the filters 22, 21 selected thereafter (step S97) are, for example, as shown in FIG. 2(c), the first filter 21a of the first-stage group, the first filter 22a of the second-stage group, the second filter 21b of the first-stage group, the second filter 22b of the second-stage group, the third filter 21c of the first-stage group, the third filter 22c of the second-stage group, the fourth filter 21c+1 of the first-stage group, the fourth filter 22c+1 of the second-stage group, ...

[0111] In this way, the spectrum analyzer 1 of this embodiment can achieve signal measurement without non-overlapping bands in a short time and with high accuracy by electronically controlling the changeover switch 20 without using a mechanically switching filter bank (see FIG. 17), and can accommodate wider bands such as millimeter wave band measurement.

[0112] (Variation 1) FIG. 8 shows a configuration including a main part of a local signal supply path of a filter bank circuit 10B according to the first modification of the spectrum analyzer 1 according to the present embodiment. In FIG. 8, the same parts as those of the filter bank circuit 10A shown in FIG. 5 are denoted by the same reference numerals. As shown in FIG. 8, the filter bank circuit 10B according to the first modification is provided with two local signal generators, that is, a local signal generator (LO1) 112-1 corresponding to the first filter group G1 and a local signal generator (LO2) 112-2 corresponding to the second filter group G2. The other configuration is the same as that of the filter bank circuit 10A according to the first embodiment described above. In order to drive and control the filter bank circuit 10B according to the first modification, a frequency sweep control unit 152 in a control unit 150 (see FIG. 4) has a functional configuration capable of individually performing frequency sweep control for the local signal generators 112-1 and 112-2 provided in the filter bank circuit 10B.

[0113] Fig. 9 is a timing chart showing the operation of the filter bank circuit 10B during signal measurement by the spectrum analyzer 1 employing the filter bank circuit 10B according to the modified example 1. Here, Fig. 9(a) shows the switching operation of the changeover switch 20 ("SPDT SW control"), and Fig. 9(b) shows the setting operation of the local signals for the local signal generators 112-1 and 112-2 ("LO1, LO2 frequency setting").

[0114] 9(a), regarding the switching control of the changeover switch 20, the frequency sweep control unit 152 performs switching from the first filter group G1 (f1, f3, f5, f7 route) to the second filter group G2 (f2, f4, f6, f8 route) at the timing indicated by the two-dot chain vertical line, and performs switching from the second filter group G2 (f2, f4, f6, f8 route) to the first filter group G1 (f1, f3, f5, f7 route) at the timing indicated by the dotted vertical line. The control unit 150 performs control so that the frequency components passing through the desired filter 21 in the first filter group G1 and the frequency components passing through the desired filter 22 in the second filter group G1 are alternately measured (for example, in the order of bands f1, f2, f3, ...) in accordance with the alternating switching between the first filter group G1 and the second filter group G2.

[0115] When the measurement operation control based on the operation timing shown in Fig. 9(a) is viewed from the viewpoint of the setting operation of local frequencies LO1, LO2 for local signal generators 112-1, 112-2, it becomes as shown in Fig. 9(b). In this case, since there are two local signal generators 112-1, 112-2, control is performed such that LO2 corresponding to the f2, f4, f6, f8 routes in the second filter group G2 is set by local signal generator 112-2 during measurement of each frequency component corresponding to the f1, f3, f5, f7 routes in the first filter group G1, and LO1 corresponding to the f1, f3, f5, f7 routes in the first filter group G1 is set by local signal generator 112-1 during measurement of each frequency component corresponding to the f2, f4, f6, f8 routes in the second filter group G2.

[0116] 9, no setting of LO1 or LO2 is required between the measurement of, for example, band f1 in the first filter group G1 and the measurement of, for example, band f2 in the second filter group G2, and no time is required to set LO1 or LO2 between frequency measurements of different routes, as compared to the case of using one local signal generator 112 shown in Fig. 6. As a result, in the configuration of the spectrum analyzer 1 using the filter bank circuit 10B according to the second modification, unnecessary waiting time related to LO setting that does not contribute to the measurement is eliminated, and measurement can be realized in a shorter time than the configuration example shown in Fig. 6, in which there is no overlap of passbands in the individual routes of the f1, f3, f5, f7 routes and the f2, f4, f6, f8 routes, and in which the passbands of adjacent routes between the f1, f3, f5, f7 routes and the f2, f4, f6, f8 routes overlap.

[0117] Based on the flow of "SPDT SW control" and "LO1, LO2 frequency setting" controls described with reference to Fig. 9, the signal measurement control operation in the spectrum analyzer 1 employing the filter bank circuit 10B according to the first modification will be described with reference to the flowchart shown in Fig. 10. In Fig. 10, the same processing steps as those in the signal measurement control operation in the spectrum analyzer 1 employing the filter bank circuit 10A shown in Fig. 7 are denoted by the same reference numerals.

[0118] In Fig. 10, the processing steps S4A, S6A, and S41A that are different from the processing steps shown in Fig. 7 will be mainly described. In this spectrum analyzer 1, when it is determined that the filter 21 or filter 22 selected in step S3 is a single filter ("single" in step S3), the control unit 150 sets the path of the changeover switch 20 corresponding to the path of that filter, and also sets the local frequency (LO1 or LO2) (step S41A).

[0119] Next, in the control unit 150, the filter switching control unit 151 controls the changeover switch 20 to switch between the first filter group G1 and the second filter group G2 based on the path setting in step S41A, and accordingly, the frequency sweep control unit 152 controls the frequency sweep for the local signal generator 112-1 or the local signal generator 112-2 based on the LO (LO1 or LO2) setting in step S41A, while performing measurement on the filter 21 or the filter 22 (step S42).

[0120] On the other hand, if it is determined that a plurality of filters 21, 22 are selected in step S3 ("multiple" in step S3), control unit 150 performs the processes of steps S4A to S7. First, control unit 150 sets the LO (LO1 or LO2) frequency corresponding to filter 21 or filter 22 selected first in local signal generator 112-1 or local signal generator 112-2 corresponding to that filter 21 or filter 22 (step S4A).

[0121] Next, the control unit 150 sets a path of the changeover switch 20 corresponding to the filter (for example, the filter 21) that is selected first, and performs a measurement with the filter 21 that is selected first (step S5).

[0122] During the measurement in step S5, the control unit 150 sets the LO (LO2) frequency corresponding to the second selected filter 22 in the local signal generator 112-2 corresponding to that filter 22, similar to step S4A (step S6A).

[0123] Subsequently, the control unit 150 sets a path of the changeover switch 20 corresponding to the second selected filter 22, and performs measurement with the second selected filter 22 (step S7).

[0124] Thereafter, when it is determined in step S8 that there is a filter 21, 22, ... to be selected next (YES in step S8), the control unit 150 replaces "2nd" with "nth" and repeats steps S6A and S7 described above until there is no filter 21, 22, ... to be selected next (step S9). Even during the measurement period using the second to nth filters, the control unit 150 continues to set the LO (LO1, LO2, ...) frequency for the local signal generator 112-1 or local signal generator 112-2 corresponding to the filter 21, 22, ... to be selected next, to measure the selected filter 21, 22, ..., and during the measurement using the filter 21, 22, ..., to set the LO (LO2, LO1, ...) frequency corresponding to the filter 22, 21, ... to be selected next.

[0125] 10, in the spectrum analyzer 1, while one of the first filter group G1 and the second filter group G2 is measuring, the LO frequency of the other is set, and when measurement of the next passband begins, the LO frequency setting is already completed (see FIG. 9), so there is no wait time until the LO frequency setting is complete, and measurement can begin immediately. With this signal measurement operation, there is no need to consider waiting for the LO frequency setting to be completed when controlling the switching of the selector switch 20.

[0126] (Variation 2) The configuration of a filter bank circuit 10C according to Modification 2 of the spectrum analyzer 1 according to the present embodiment is shown in Fig. 11. As shown in Fig. 11, the filter bank circuit 10C according to Modification 2 includes a single-pole, three-throw changeover switch 20-1, and is configured to be able to selectively supply an input signal from the input section 20a to any one of the first filter group G1, the second filter group G2, or the third filter group G3 by controlling the changeover switch 20-1 to switch the input section 20a to any one of the output sections 20b, 20c, and 20d.

[0127] In the filter bank circuit 10C according to the second modification, the first filter group G1 includes filters 21a, 21b, and 21c having non-overlapping bands f1, f4, f7, and f10 as their passbands, respectively. The second filter group G2 includes filters 22a, 22b, and 22c having non-overlapping bands f2, f5, f8, and f11 as their passbands, respectively. The third filter group G3 includes filters 23a, 23b, and 23c having non-overlapping bands f3, f6, f9, and f12 as their passbands, respectively.

[0128] The filters 21a, 21b, and 21c constituting the first filter group G1, the filters 22a, 22b, and 22c constituting the second filter group G2, and the filters 23a, 23b, and 23c constituting the third filter group G3 (hereinafter, sometimes referred to as filters 23) are each provided with two BPFs 27a1, 27b1, and 27c1 between the input-side hybrids 25a1, 25b1, and 25c1 and the output-side hybrids 26a1, 26b1, and 26c1, respectively, in the same manner as in the above-described embodiment (see FIGS. 1 and 5). The filter groups G1, G2, and G3 are each made up of a BLC filter bank having two BPFs 27a2, 27b2, and 27c2 arranged between each of the hybrids 25a2, 25b2, and 25c2 on the input side and each of the hybrids 26a2, 26b2, and 26c2 on the output side, and a BLC filter bank having two BPFs 27a3, 27b3, and 27c3 arranged between each of the hybrids 25a3, 25b3, and 25c3 on the input side and each of the hybrids 26a3, 26b3, and 26c3 on the output side. Here, the number of filters 21, 22, and 23 constituting each of the filter groups G1, G2, and G3 can be any number.

[0129] Regarding the passbands (bands f1, f4, f7, f10; bands f2, f5, f8, f11; and bands f3, f6, f9, f12) of the filters 21a, 21b, and 21c constituting the first filter group G1, the filters 22a, 22b, and 22c constituting the second filter group G2, and the filters 23a, 23b, and 23c constituting the third filter group G3, adjacent passbands (bands) are set to overlap in the order of band f1 to band f12, as shown on the input side of the changeover switch 20-1 in FIG. 11.

[0130] Here, the grouping of the filter group G will be described. Referring to the filter bank circuits 10A and 10B according to the above-mentioned embodiment and modified example 1, when the overlap between the filters 21 and 22 is large, the grouping (two-partitioning) of the filter groups G into two filter groups G1 and G2 may not provide sufficient guard bands. In response to a demand to increase the number of guard bands, it can be said that three-part division into three filter groups G1, G2, and G3 as in modified example 2 is more advantageous than two-part division. In particular, when the present invention is applied to a signal analyzer, if the signal to be analyzed becomes wideband, the overlap band also becomes large. Therefore, when the guard bands cannot be obtained, the number of divisions is increased to deal with the situation.

[0131] However, in the present invention, the grouping of the filter group G is not limited to two or three divisions, and as described above, the number of divisions may be increased to a larger number n (n is an integer equal to or greater than 3) and a single-pole, n-throw switch (SPnT SW) may be used as the changeover switch 20. With a configuration in which the filter groups G1 to Gn are divided into n divisions using SPnT SW, it becomes possible to obtain a sufficient guard band for each group.

[0132] In a filter bank circuit 10C according to Modification 2 having divided filter groups G1, G2, and G3 shown in Fig. 11, except that the number of switching paths is changed from two to three, it can be operated by controlling the measurement operation in accordance with the flowchart shown in Fig. 7, similarly to the filter bank circuit 10A shown in Fig. 1. The configuration of the filter bank circuit 10C according to Modification 2 has the advantage that it is easier to ensure guard bands between the filters 21, 22, and 23 in the filter groups G1, G2, and G3 than the filter bank circuit 10A shown in Fig. 1.

[0133] (Variation 3) In the spectrum analyzer 1 according to this embodiment, the filters 21, 22, ... constituting the filter groups G1 to Gn are not limited to a BLC filter bank configuration using branch-line couplers as hybrids, such as the filters 21a, 21b, 21c and the filters 22a, 22b, 22c shown in FIG. 1.

[0134] 12 shows the configuration of a filter bank circuit 10D according to Modification 3 of the spectrum analyzer 1 of the present embodiment. In the filter bank circuit 10D according to Modification 3, the changeover switch 20, the local signal generators 112-1 and 112-2, and the mixers 111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, and 111-8 are equivalent to those in the filter bank circuit 10B according to Modification 1 (see FIG. 8).

[0135] In a filter bank circuit 10D according to the third modification, a first filter group G1 includes filters 41a, 41b, and 41c, and a second filter group G2 includes filters 42a, 42b, and 42c. The filters 41a, 41b, and 41c include circulators 45a, 45b, and 45c, and BPFs 46a, 46b, and 46c, respectively. The filters 42a, 42b, and 42c include circulators 45d, 45e, and 45f, and BPFs 46d, 46e, and 46f, respectively. Each of the circulators 45a, 45b, 45c and circulators 45d, 45e, 45f has an input port (first port) for inputting the signal under measurement, an output port (second port) for outputting a signal of the signal under measurement that is in a set passband, and a transfer port (third port) for transferring a signal of the signal under measurement that is outside the set passband to the next stage.

[0136] The BPFs 46a, 46b, and 46c constituting the first filter group G1 are provided in a combination with adjacent non-overlapping bands f1, f3, f5, and f7 as passbands, and the BPFs 46d, 46e, and 46f constituting the second filter group G2 are provided in a combination with adjacent non-overlapping bands f2, f4, f6, and f8 as passbands. In addition, between the first filter group G1 and the second filter group G2, the bands f1, f2, f3, f4, f5, f6, f7, and f8 are set to have an overlapping area between adjacent bands.

[0137] In the spectrum analyzer 1 including the filter bank circuit 10D according to the third modification, when the changeover switch 20 is switched so that the input section 20a is connected to the output section 20b, the input signal is supplied to the first filter group G1 side. At this time, among the signal components of the bands f1, f3, f5, and f7 that are the input signal, the signal component of the band f1 is supplied to the mixer 111-1 through the circulator 45a and the BPF 46a. The signal component of the band f3 is input from the circulator 45a to the circulator 45b, and then is supplied to the mixer 111-2 through the BPF 46b. The signal component of the band f5 is input to the circulator 45c through the circulators 45a and 45b, and then is supplied to the mixer 111-3 through the BPF 46c. The signal component of band f7 passes through circulators 45a and 45b and enters circulator 45c, and is then supplied to mixer 111-4 without passing through BPF 46c.

[0138] Also, when the changeover switch 20 is switched so that the input section 20a is connected to the output section 20c, the input signal is supplied to the second filter group G2 side. At this time, among the signal components of bands f2, f4, f6, and f8, which are the input signal, the signal component of band f2 is supplied to the mixer 111-5 through the circulator 45d and the BPF 46d. The signal component of band f4 is input from the circulator 45d to the circulator 45e, and then is supplied to the mixer 111-6 through the BPF 46e. The signal component of band f6 is input to the circulator 45f through the circulators 45d and 45e, and then is supplied to the mixer 111-7 through the BPF 46f. The signal component of band f8 is input to the circulator 45f through the circulators 45d and 45e, and then is supplied to the mixer 111-8 without passing through the BPF 46f.

[0139] At this time, the spectrum analyzer 1, for example, by using the control unit 150 to control the switching of the changeover switch 20 in accordance with the flowchart shown in FIG. 10 and to control the LO (LO1, LO2) frequency setting for the local signal generators 112-1, 112-2, sets the LO frequency of the first filter group G1 or the second filter group G2 while the other is measuring, similar to when the filter bank circuit 10B of variant example 1 is provided, thereby enabling signal measurement operation with no wait time until the LO frequency setting is completed.

[0140] (Other variations) As another modification of the filter bank circuit 10A used in the spectrum analyzer 1 according to this embodiment, the filters 21, 22, ... constituting the filter groups G1 to Gn may be configured to use, for example, a BPF, a low-pass filter (LPF), a high-pass filter (HPF), and a band-elimination filter (BEF), either alone or in combination, instead of using the above-mentioned BLC filter bank or a circulator.

[0141] As a specific example, in the filter bank circuit 10 according to another modification, the filters 21, 22, ... may be configured only with BPFs that pass frequency components in a passband set corresponding to the filters 21, 22, .... According to this configuration, each of the filters 21, 22, ... in the filter group G can be easily realized using a general-purpose BPF, which is expected to simplify the structure and reduce costs.

[0142] Furthermore, in filter bank circuit 10A according to yet another modification, filters 21, 22, ... may be configured with HPFs that pass frequency components in a frequency band above a pass band set for each filter 21, 22, ..., and LPFs that pass frequency components in a frequency band below the pass band. With this configuration, filters 21, 22, ... in filter group G can be easily realized using general-purpose HPFs and LPFs, simplifying the structure and reducing costs.

[0143] Additionally, in this embodiment, various modifications or applications of the configuration of the filter bank circuit 10 are possible within the scope of the gist that guard bands are secured between each filter in the filter groups G1 to Gn and overlap between the passbands of each filter is maintained between the filter groups G1 to Gn.

[0144] As described above, the filter bank circuit 10 (10A, 10B, 10C, 10D) according to this embodiment has one input section 20a, a single-pole, n-throw changeover switch 20 that switches between n (n is an integer of 2 or more) output sections 20b, 20c, 20d, ..., and n groups of filter groups G1, G2, ..., Gn that are respectively connected to the n output sections 20b, 20c, 20d, .... The filter groups G1, G2, ..., Gn each include m (m is an integer of 2 or more) filters 21, 22, .... Each of the filters 21, 22, ... is set to a passband that does not overlap with the passband of the other filters 21, 22, ... within the group, and overlaps with the passband of each filter 21, 22, ... of the other groups by a predetermined bandwidth (ol1, ol2, ...) between the groups, and the predetermined bandwidth is set to a bandwidth wider than the bandwidth occupied by the signal to be measured or the test signal so that the signal to be measured or the test signal is not dropped. Here, the numbers n and m can be selected arbitrarily.

[0145] With this configuration, the filter bank circuit 10 according to this embodiment can maintain overlap between the passbands of the filters 21, 22 of different groups of filter groups G while maintaining guard bands between the passbands of the filters 21, 22 in the filter group G by switching between the multiple filter groups G (G1, G2, ...) for each group. This makes it possible to measure a signal under test or test a DUT for all bands with appropriate overlap bands, without requiring a long switching time or complicated switching control as with a mechanically switched filter bank (see FIG. 17) by using a filter group G that does not have a moving part.

[0146] Moreover, the filter bank circuit 10 according to this embodiment is configured to input frequency components in the millimeter wave band of 255 to 315 GHz, and extract the frequency components in the millimeter wave band by dividing the frequency components into n×m overlapping passbands using m filters 21, 22, ... for each of n groups.

[0147] With this configuration, the filter bank circuit 10 of this embodiment does not have any bands that cannot be measured or tested for the millimeter wave band signal under test or test signal, and can extract frequency components from which unnecessary radio waves are suppressed by extremely easy and quick switching control of the change-over switch 20.

[0148] In addition, in the filter bank circuit 10A according to this embodiment, the filters 21 and 22 constituting the filter groups G1 and G2 are configured as a filter bank using a BLC that passes frequency components in a passband set corresponding to the filters 21 and 22.

[0149] As a result, the filter bank circuit 10A according to this embodiment employs a filter bank using BLC and BPF, which, together with the use of the changeover switch 20, allows for a simplified structure and reduced costs.

[0150] Furthermore, in the filter bank circuit 10 according to this embodiment, the filters 21 and 22 may be configured as BPFs that pass frequency components in a passband set corresponding to the filters 21 and 22. This allows the filters 21 and 22 in the filter groups G1 and G2 in the filter bank circuit 10 to be easily realized using general-purpose BPFs, simplifying the structure and reducing costs.

[0151] In the filter bank circuit 10D according to the present embodiment, the filters 41a, 41b, 41c, 42a, 42b, and 42c each have an input port, an output port, and a transfer port, and are configured to include circulators 45a to 45f that output a frequency component input from the input port to the output port when the frequency component corresponds to the stage number, and input the frequency component to the input port of the next stage from the transfer port when the frequency component is not the frequency component, and BPFs 46a to 46f that are connected to the output port and have a passband set according to the stage number. As a result, in the filter bank circuit 10D, the filters 21 and 22 in the filter groups G1 and G2 can be easily realized using general-purpose circulators and BPFs, which simplifies the structure and reduces costs.

[0152] Furthermore, in the filter bank circuit 10 according to this embodiment, the filters 21 and 22 may be configured as a combination of an HPF and an LPF, and may pass frequency components in a passband set for the filters 21 and 22. This allows the filters 21 and 22 in the filter groups G1 and G2 of the filter bank circuit 10 to be easily realized using general-purpose HPFs and LPFs, thereby simplifying the structure and reducing costs.

[0153] Moreover, the spectrum analyzer 1 according to this embodiment has a frequency conversion section 100 having a filter 113 that supplies a millimeter wave band signal under measurement to a mixer 111 together with a local signal output from a local signal generator 112 and extracts a signal of a predetermined intermediate frequency band from the mixed output, and a detector 120 that detects the signal of the intermediate frequency band, and determines the spectral characteristics of the signal under measurement by changing the frequency of the local signal in accordance with the frequency to be analyzed, and the above-mentioned filter bank circuit 10 (10A, 10B, 10C, 10D) is provided in the stage preceding the frequency conversion section 100.

[0154] This spectrum analyzer 1 has a filter switching control unit 151 that controls switching of the changeover switch 20, to which the signal to be measured is inputted to the input unit 20a, so that a plurality of filter groups G1, G2 are repeatedly selected in order on a group basis according to the frequency to be analyzed, and is configured to sequentially extract frequency components that pass through filters 21, 22 having a passband corresponding to one frequency band of the frequencies to be analyzed for each of the filter groups G1, G2 that are selected in order.

[0155] With this configuration, the spectrum analyzer 1 can extract frequency components corresponding to multiple (maximum (n × m)) overlapping passbands from the signal to be measured input to the filter bank circuit 10 while suppressing unnecessary radio waves, and output the frequency components to the detector 120.By using the filter groups G1 and G2 which have no moving parts, it is possible to realize smooth measurement of the spectral characteristics of signals in all bands without the need for long switching times or complicated switching control as with a mechanically switched filter bank (see FIG. 17).

[0156] In addition, the spectrum analyzer 1 of this embodiment further includes a plurality of local signal generators 112-1, 112-2 provided corresponding to the plurality of filter groups G1, G2, respectively, mixers 111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, 111-8 provided corresponding to each of the filters 21, 22 constituting the plurality of filter groups G1, G2, respectively, and a frequency sweep control unit 152 that sets local frequencies for the mixers 111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, 111-8 corresponding to the filters 21, 22 having a pass band corresponding to one frequency band in the filter groups G1, G2 to be selected next when measuring the spectral characteristics of the filters 21, 22 having a pass band corresponding to one frequency band in the selected filter groups G1, G2.

[0157] With this configuration, the spectrum analyzer 1 of this embodiment can eliminate the unnecessary waiting time for setting the local frequency between the time when the measurement is made by each of the filters 21, 22 constituting the selected filter group G1, G2 and the time when the measurement is made by each of the filters 21, 22 constituting the next filter group G1, G2, and can perform the measurement smoothly.

[0158] Furthermore, a method for controlling the filter bank circuit 10 in a spectrum analyzer 1 that uses the filter bank circuit 10 according to this embodiment includes a setting step (S1) of setting a frequency to be analyzed, a step (S2) of calculating the filters 21, 22 to be selected from the filter groups G1, G2 based on the set frequency to be analyzed, a step (S5) of setting a path for the changeover switch 20 corresponding to the selected filters 21, 22 and controlling the changeover switch 20 to select the filter group G1, G2 to which the selected filters 21, 22 belong, and steps (S5, S7, S9) of extracting frequency components that pass through the filters 21, 22 calculated in the calculating step, from the filter groups G1, G2 switched in the changingover control step.

[0159] With this configuration, according to the control method of the filter bank circuit 10, the frequency to be analyzed can be divided into multiple (n × m) overlapping passbands, and the frequency components of each passband can be extracted from the signal under measurement while suppressing unnecessary radio waves. By simply controlling the changeover switch 20, it is possible to eliminate bands that cannot be measured or tested, and also to shorten the switching time of the changeover switch 20.

[0160] (Signal analyzer 2 using filter bank circuit 10) The filter bank circuit 10A according to the above embodiment is not limited to the spectrum analyzer 1 shown in FIG. 4, but can also be applied to, for example, a signal analyzer 2 that performs analysis processing of signals in a predetermined frequency band.

[0161] 13 is a diagram showing a general configuration of a signal analyzer 2 that uses a filter bank circuit 10A. This signal analyzer 2 has a frequency conversion section 100F, an analog-to-digital converter (ADC) 125, a control section 150F, an operation section 160, and a display section 161, and also has a filter bank circuit 10A (see FIG. 1) having the above-mentioned configuration in the stage preceding the frequency conversion section 100F.

[0162] The frequency conversion section 100F is configured to include a mixer 111F, a local signal generator 112F, and a filter 113F.

[0163] The mixer 111F mixes a signal (RF frequency) of each frequency component in which spurious waves are suppressed and output from the filter bank circuit 10A with a local signal input from the local signal generator 112F, thereby converting the signal under measurement from an RF frequency to an intermediate frequency signal (IF frequency) and outputting the signal.

[0164] Based on a local signal (reference signal) input from a local oscillation signal source 9, the local signal generator 112F generates a local signal to be sent to the mixer 111F.

[0165] The filter 113F is a filter function unit that receives the IF signal frequency-converted by the mixer 111F, passes only the signal of the frequency components of the input IF signal in a certain band set in advance, and inputs the signal to the ADC 125. Here, the overlap band is set so that the signal of the frequency components of the IF signal in a certain band set in advance (the signal under test) is not dropped in the filter bank circuit 10A. In other words, the overlap band needs to pass a band wider than the IF band signal.

[0166] The ADC 125 converts the signal (signal under measurement) that has passed through the filter bank circuit 10A and has been frequency-converted by the frequency conversion section 100F from an analog signal to a digital signal.

[0167] The control section 150F has a filter switching control section 151F, a frequency control section 152F, and a signal analysis section 153F. The filter switching control section 151F is equivalent to that provided in the control section 150 of the spectrum analyzer 1 (see FIG. 7).

[0168] The frequency control section 152F controls the setting of a local frequency so that a signal in a specified analysis target frequency range can be received when the frequency conversion section 100F converts the frequency of the signal under test. The local signal generator 112F constituting the frequency conversion section 100F has a configuration capable of varying the local frequency according to the received RF frequency. Therefore, the frequency control section 152F may be configured to control the local signal generator 112F and sweep the local frequency.

[0169] The signal analysis unit 153F executes a process of analyzing the waveform of the signal (signal under measurement) converted into a digital signal by the ADC 125, specifically, a process of analyzing the modulated signal and performing waveform analysis data for displaying the waveform of the digital signal, such as a spectrum, and generating a modulation analysis result.

[0170] In order to perform signal analysis processing in the signal analyzer 2 having the above configuration, for example, a frequency to be analyzed is set by a predetermined setting operation in the operation unit 160. This processing corresponds to the processing of step S1 (see FIG. 7) in the spectrum analyzer 1.

[0171] Next, the control unit 150F performs a process of calculating the filters 21, 22 to be selected from the filter groups G1, G2 in the filter bank circuit 10A based on the set analysis target frequency. This process corresponds to the process of step S2 (see FIG. 7) in the spectrum analyzer 1.

[0172] Subsequently, the control unit 150F sets a path for the changeover switch 20 corresponding to the filters 21, 22 to be selected, which are calculated in the above calculation process, and then the filter switching control unit 151F controls the changeover switch 20 to select either the filter group G1, G2 to which the filter 21, 22 to be selected belongs. This process corresponds to the process of step S5 (see FIG. 7) in the spectrum analyzer 1.

[0173] As a result, in the filter bank circuit 10A, the signal under measurement input from the input section 20a of the changeover switch 20 passes through the filters 21, 22 calculated by the above-mentioned calculation process among the filter groups G1, G2 switched by the above-mentioned switching control, and is output, and the frequency components that have passed through are input to the frequency conversion section 100F as the object of analysis.

[0174] In the frequency conversion unit 100F, the frequency component (signal under test) input from the filter bank circuit 10A and the local signal input from the local signal generator 112F are mixed in the mixer 111F to convert them to an intermediate frequency band, and a signal of a predetermined intermediate frequency band is extracted from the mixed output by the filter 113F and sent to the ADC 125.

[0175] The ADC 125 converts the frequency-converted signal from an analog signal to a digital signal and inputs it to the signal analysis unit 153F. The signal analysis unit 153F performs processing to analyze the modulated signal and waveform analysis data for displaying the waveform of the digital signal input from the ADC 125, such as spectrum, and to generate a modulation analysis result. Furthermore, the control unit 150F performs control for signal analysis, such as displaying the waveform analysis data generated by the signal analysis unit 153F on the display unit 161.

[0176] Here, a signal analyzer 2 using a filter bank circuit 10A is illustrated as an example, but the filter bank circuit 10A may also use other filter bank circuits 10, such as the filter bank circuit 10B according to the above-mentioned modification example 1, the filter bank circuit 10C according to modification example 2, and the filter bank circuit 10D according to modification example 3.

[0177] In this way, the signal analyzer 2 of this embodiment has a frequency conversion unit 100F having a filter 113F that supplies a signal under measurement of a predetermined frequency component to a mixer 111F together with a local signal output from a local signal generator 112F and extracts a signal of a predetermined intermediate frequency band from the mixed output, and a signal analysis unit 153F that converts the intermediate frequency band signal into a digital signal by an ADC 125 and then analyzes the waveform of the signal, and analyzes the waveform of the signal under measurement by changing the frequency of the local signal in accordance with the frequency to be analyzed.

[0178] The signal analyzer 2 of this embodiment has a filter bank circuit 10 having the above-mentioned configuration provided in front of the frequency conversion section 100F, and has a filter switching control section 151F that controls switching of the change-over switch 20, through which the signal to be measured is input to the input section 20a, so that a plurality of filter groups G1, G2 are selected in group units according to the frequency to be analyzed, and for each selected filter group G1, G2, frequency components passing through filters 21, 22 having a pass band corresponding to one frequency band of the frequencies to be analyzed are extracted, and the waveform of the signal of the frequency components is analyzed after conversion from an analog signal to a digital signal.

[0179] With this configuration, the signal analyzer 2 of this embodiment can extract frequency components corresponding to multiple (n × m) overlapping passbands from the signal under measurement input to the filter bank circuit 10A, with unnecessary radio waves suppressed, and output the frequency components to the ADC 125, with overlapping bands secured so that the signal under measurement is not lost.By using a filter group that has no moving parts, signal analysis of signals in all bands can be smoothly and accurately realized without the need for long switching times or complicated switching control required by a mechanically switched filter bank.

[0180] Furthermore, a control method for the filter bank circuit 10A in a signal analyzer 2 that uses the filter bank circuit 10A according to this embodiment includes a setting step (S1) of setting a test target frequency, steps (S2, S12) of calculating filters 21, 22 to be selected from the filter groups G1, G2 based on the set test target frequency, steps (S5, S13) of setting paths for the changeover switch 20 corresponding to the selected filters 21, 22 and controlling the changeover switch 20E to select the filter group G1, G2 to which the selected filters 21, 22 belong, and a step of extracting frequency components that pass through the filters 21, 22 calculated in the calculating step, from the filter groups G1, G2 switched in the switching control step.

[0181] According to the control method of this filter bank circuit 10A, when the filter bank circuit 10A is mounted on the signal analyzer 2, the test target frequency can be divided into multiple overlapping passbands, and by simple switching control of the selector switch, the bands in which the DUT cannot be tested can be eliminated, and the switching time of the selector switch can also be shortened.

[0182] (Signal Generator 3 Using Filter Bank Circuit 10E) The filter bank circuits 10, such as the filter bank circuit 10A according to the above embodiment, the filter bank circuit 10B according to the first modification, the filter bank circuit 10C according to the second modification, and the filter bank circuit 10D according to the third modification, may be implemented not only in the spectrum analyzer 1 shown in FIG. 4 but also in, for example, a signal generating device 3 that performs a receiving sensitivity test on a DUT.

[0183] 14 is a diagram showing a general configuration of a signal generating device 3 using the above-mentioned filter bank circuit 10. The signal generating device 3 is assumed to be a test signal generating device that generates a test signal for testing the receiving sensitivity of a DUT for a millimeter wave band signal.

[0184] The signal generating device 3 includes a frequency conversion section 100E, a signal generating section 130, a control section 150E, an operation section 160, a display section 161, and a filter bank circuit 10E provided in the subsequent stage of the frequency conversion section 100E. The frequency conversion section 100E is configured with a mixer 111E, a local signal generator 112E, and a filter 113E, and the control section 150E is configured with a filter switching control section 151E, a frequency control section 152E, and a signal generation control section 153E.

[0185] In the signal generating device 3, the frequency conversion unit 100E, under the control of the signal generation control unit 153E, provides the intermediate frequency band test signal output from the signal generating unit 130 together with the local signal output from the local signal generator 112E to the mixer 111E to perform processing to convert them into a millimeter wave band signal. At that time, the frequency conversion unit 100E changes the frequency of the local signal by the frequency control unit 152E according to a test target frequency set by, for example, the operation unit 160 in order to test the DUT, and sends the signal after frequency conversion to a subsequent stage as a test signal for the DUT.

[0186] The above-mentioned filter bank circuits 10A, 10B, 10C, 10D, etc. can be used as the filter bank circuit 10E provided in the subsequent stage, but the following description will be given assuming a configuration using the filter bank circuit 10A (see FIG. 1).

[0187] 15, the filter bank circuit 10E in the signal generating device 3 has a configuration in which the filter bank circuit 10A shown in FIG. 1 is implemented in such a manner that an IF signal (a test signal input from the signal generating unit 130 to the frequency converting unit 100E) is input to the frequency converting unit 100E and converted to an RF frequency (f1, f2, f3, ...), which is input to an input section 20b1 or 20c1 of the changeover switch 20E via a filter group G1 or filter group G2, and is selected by a changeover signal and can be sent as a test signal serving as an RF Output to an output section 20a1 of the changeover switch 20E. That is, in the filter bank circuit 10E used in the signal generating device 3, the changeover switch 20E has a configuration in which the output sections 20b and 20c of the changeover switch 20 of the filter bank circuit 10A function as the input sections 20b1 and 20c1, respectively, and the input section 20a functions as the output section 20a1.

[0188] In testing a DUT using the signal generating device 3, after the test frequency is set in the operation unit 160, a test signal that satisfies the set conditions and is generated from the signal generating unit 130 under the control of the signal generation control unit 153E is frequency converted to an RF signal in the frequency conversion unit 100E and then input to the input units 20b1, 20c1 of the changeover switch 20E in the filter bank circuit 10E.

[0189] At this time, in the control unit 150E, the filter switching control unit 151E controls the changeover switch 20 to which the frequency-converted signals (f1, f2, f3, ...) are input so that the filter groups G1 and G2 are selected in groups according to the set test target frequency. In the filter group G1 or filter group G2 selected by this switching control, the signals of bands f1, f3, f5, ... and the signals of bands f2, f4, f6, ... pass through the filters 21 and 22 having the corresponding passbands, respectively, and are extracted as test signals. The extracted test signals are transmitted from an RF transmission unit (not shown) to the DUT.

[0190] The signal transmission control operation in the signal generator 3 for the above-mentioned DUT test is performed according to the flowchart shown in Fig. 16. In order to control the signal transmission in the signal generator 3 for the DUT test, for example, a frequency, i.e., a test target frequency, is set by a predetermined setting operation in the operation unit 160 (step S11).

[0191] Next, the control unit 150E calculates the filters 21, 22 to be selected from the filter groups G1, G2 in the filter bank circuit 10A, and the setting conditions of the local frequency (LO setting) based on the set test target frequency (step S12).

[0192] Next, the control unit 150E sets the path of the changeover switch 20E corresponding to the filters 21, 22 to be selected, which was calculated in step S12, and then the filter switching control unit 151E controls the changeover switch 20E to select either the filter group G1, G2 to which the filters 21, 22 to be selected belong (step S13).

[0193] As a result, in the filter bank circuit 10E, the test signal input from the input parts 20b1, 20c1 of the changeover switch 20E passes through the filters 21, 22 calculated by the above calculation process among the filter groups G1, G2 switched by the above switching control, and is output from the output part 20a1 of the changeover switch 20E. The control part 150E controls the changeover switch 20E to send out the signal of the frequency component output from the output part 20a1 as the test signal (step S14).

[0194] As described above, the signal generating device 3 according to this embodiment has a frequency conversion section 100E that provides the intermediate frequency band test signal output from the signal generating section 130 together with the local signal output from the local signal generator 112E to the mixer 111E to convert them into a millimeter wave band signal, changes the frequency of the local signal according to a test frequency for testing the DUT, and sends out the signal after frequency conversion by the frequency conversion section 100E as a test signal for the DUT, and has a configuration in which a filter bank circuit 10E is provided in the subsequent stage of the frequency conversion section 100E. Considering that the signal flow is reversed, the filter bank circuit 10E can be configured by the above-mentioned filter bank circuits 10A, 10B, 10C, 10D, etc.

[0195] This signal generating device 3 has a filter switching control unit 151E that controls the switching of the changeover switch 20E, and selects a filter group G1 or G2 having a passband corresponding to the test frequency according to the test frequency, and sends out the selected filter group as a test signal.

[0196] With this configuration, the signal generating device 3 of this embodiment can extract frequency components corresponding to a plurality of (n×m) (in the example shown in FIG. 15, (2×4)=8) overlapping passbands from the frequency-converted signal input to the filter bank circuit 10E, with overlapping bands secured so that the test signal is not lost, while suppressing unnecessary radio waves, and send them out as test signals.By using the filter groups G1 and G2 that do not have moving parts, it is possible to smoothly test the DUT for signals of all bands without requiring long switching times or complicated switching control as in a mechanically switched filter bank (see FIG. 17).

[0197] Furthermore, the control method of the filter bank circuit 10E in the signal generating device 3 using the filter bank circuit 10E according to this embodiment includes a setting step of setting a test target frequency (see step S11 in FIG. 16), a step of calculating the filters 21, 22 to be selected from the filter groups G1, G2 based on the set test target frequency (see step S12 in FIG. 16), a step of setting a path for the change-over switch 20 corresponding to the selected filters 21, 22 and controlling the change-over switch 20 to select the filter group G1, G2 to which the selected filters 21, 22 belong (see step S13 in FIG. 16), and a step of extracting frequency components that pass through the filters 21, 22 calculated in the calculating step from the filter groups G1, G2 switched in the switching control step, in order to send a test signal (see step S14 in FIG. 16).

[0198] According to the control method of this filter bank circuit 10E, the test target frequency can be divided into multiple (n × m) overlapping passbands, and the frequency components of each passband can be extracted from the test signal while suppressing unnecessary radio waves. This makes it possible to eliminate bands that cannot be tested by simple switching control of the changeover switch 20, and also shorten the switching time of the changeover switch 20.

[0199] 15 shows an example of filter bank circuit 10E having two filter groups (filter groups G1 and G2), three filters each in filter group G1 and G2, and frequencies f1 to f8, but similar to the above-mentioned embodiment, the number of filter groups, filters in a filter group, and frequencies can be any number, such as n, m, or (n×(m+1)).When n filter groups are provided, a 1-pole n-throw type changeover switch 20 (SPnT switch) is used.

[0200] Furthermore, in the signal generating device 3 according to this embodiment, it goes without saying that various modifications and applications are possible for each element in the filter bank circuit 10E, similar to the filter bank circuits 10A, 10B, 10C, and 10D used in the above-described spectrum analyzer 1. [Industrial Applicability]

[0201] As described above, the present invention has the effect of being able to accommodate measurement or testing of all bands by using an electronically switchable switch and a plurality of filter groups, and by switching the filter groups with simple switching control while ensuring a guard band within each filter group, and thereby ensuring overlap across the entire filter group, and is useful for filter bank circuits, spectrum analyzers, signal analyzers, and signal generators that use the filter bank circuits, and general methods of controlling filter bank circuits. [Explanation of symbols]

[0202] 1. Spectrum Analyzer 2. Signal Analyzer 3. Signal Generator 9 Local Oscillator Signal Source 10, 10A, 10B, 10C, 10D, 10E Filter bank circuits 20, 20-1, 20E changeover switch 20a Input section 20a1 Output section 20b, 20c, 20d output section 20b1, 20c1 Input section 21, 21a, 21b, 21c Filter (filter circuit) 22, 22a, 22b, 22c Filter (filter circuit) 23a, 23b, 23c Filter (filter circuit) 25, 26 Hybrid 27 Bandpass Filter (BPF) 41a, 41b, 41c, 42a, 42b, 42c Filter (filter circuit) 45a, 45b, 45c, 45d, 45e, 45f Circulators 46a, 46b, 46c, 46d, 46e, 46f BPF 100, 100E, 100F Frequency conversion section 101 Front-end circuit 111, 111-1, 111-2, 111‐3, 111-4, 111-5, 111-6, 111-7, 111-8, 111E, 111F Mixers 112, 112-1, 112-2, 112E, 112F Local Signal Generator 113, 113E, 113F Filters 120 Detector 125 ADC 130 Signal Generator 150, 150E, 150F Control Unit 151, 151E, 151F Filter switching control section (switching control means) 152 Frequency sweep control section (local frequency setting means) 152E, 152F Frequency control section (local frequency setting means) 153 Spectrum Data Acquisition Unit 153E Signal generation control section 153F Signal analysis section 160 Operation section 161 Display section G1, G2, G3 Filter Groups ol1, ol2, ..., ol7 overlapping bands

Claims

1. A one-pole, n-throw type changeover switch (20, 20-1) for switching between one input section (20a) and n output sections (20b, 20c, 20d) (n is an integer of 2 or more); n groups of filters (G1 to Gn) connected to the n output units, respectively; Each of the filter groups has m filter circuits (21, 22, 23) (m is an integer equal to or greater than 2), each of the filter circuits is set to a passband that does not overlap with the passband of the other filter circuits within the group, and between the groups, the passbands are set to overlap with the passbands of the filter circuits of the other groups by a predetermined bandwidth (ol1 to ol7); a predetermined bandwidth set to a bandwidth wider than a bandwidth occupied by the signal under measurement or the test signal so that the signal under measurement or the test signal is not dropped out.

2. 2. The filter bank circuit according to claim 1, wherein a predetermined frequency component is input, and the predetermined frequency component is extracted by dividing the input frequency component into n×m overlapping passbands by m filter circuits for each of the n groups.

3. 3. The filter bank circuit according to claim 1, wherein the filter circuit is configured as a filter bank using a branch line coupler (BLC) that passes frequency components of the pass band set corresponding to the filter circuit.

4. 3. The filter bank circuit according to claim 1, wherein the filter circuit is configured with a band pass filter (BPF) that passes frequency components in the pass band set corresponding to the filter circuit.

5. The filter circuits (41a, 41b, 41c, 42a, 42b, 42c) each have an input port, an output port, and a transfer port, and when a frequency component input from the input port is a frequency component corresponding to the frequency passband of the filter circuit, the frequency component is output to the output port, and when the frequency component is outside the frequency passband, the frequency component is input from the transfer port to the input port of the next stage; and a band-pass filter (46a to 46f) connected to the output port, the passband of which is set according to a frequency passband of the filter circuit; 3. The filter bank circuit according to claim 1, further comprising:

6. 3. The filter bank circuit according to claim 1, wherein the filter circuit is configured by a combination of a high-pass filter (HPF) and a low-pass filter (LPF), and passes frequency components of the pass band set corresponding to the filter circuit.

7. A spectrum analyzer (1) having a frequency conversion section (100) including a filter (113) for providing a signal under test of a predetermined frequency component to a mixer (111) together with a local signal output from a local signal generator (112) and extracting a signal of a predetermined intermediate frequency band from the mixed output, and a detector (120) for detecting the signal of the intermediate frequency band, and changing the frequency of the local signal according to a frequency to be analyzed to obtain the spectrum characteristics of the signal under test, The filter bank circuit (10) according to claim 1 is provided in the preceding stage of the frequency conversion unit, a switching control means (151) for controlling the changeover switch, the input section of which receives the signal under test, to switch the changeover switch in such a way that the plurality of filter groups are repeatedly selected in order on a group-by-group basis in accordance with the frequency to be analyzed; and sequentially extracting, for each of the filter groups which are repeatedly selected in order, frequency components which pass through the filter circuit having the passband corresponding to one frequency band of the frequencies to be analyzed.

8. a plurality of local signal generators (112-1, 112-2) provided corresponding to the plurality of filter groups, respectively; mixers (111-1, 111-2, 111-3, 111-4, 111-5, 111-6, 111-7, 111-8, etc.) provided corresponding to each of the filter circuits constituting the plurality of filter groups; a local frequency setting means (152) for setting a local frequency for the mixer corresponding to the filter circuit having the pass band corresponding to the one frequency band in the filter group to be selected next when the spectrum characteristic is measured by the filter circuit having the pass band corresponding to the one frequency band in the filter group being selected; 8. The spectrum analyzer of claim 7 further comprising:

9. A signal analyzer (2) comprising: a frequency conversion unit (100F) having a filter (113F) that supplies a signal under test of a predetermined frequency component to a mixer (111F) together with a local signal output from a local signal generator (112F) and extracts a signal of a predetermined intermediate frequency band from the mixed output; and a signal analysis unit (153F) that converts the signal of the intermediate frequency band into a digital signal by an ADC (125) and then analyzes the waveform of the signal, and changes the frequency of the local signal according to a frequency to be analyzed, The filter bank circuit (10) according to claim 1 is provided in the preceding stage of the frequency conversion unit, a switching control means (151F) for controlling the changeover switch, the input section of which receives the signal under test, to select one of the filter groups in a group unit in accordance with the analysis target frequency; A signal analyzer characterized by extracting, for each of the selected filter groups, frequency components passing through the filter circuit having the passband corresponding to one of the frequencies to be analyzed, converting the signal from an analog signal to a digital signal, and then analyzing the waveform of the signal of the frequency components.

10. A signal generating device (3) having a frequency conversion section (100E) that provides a test signal in an intermediate frequency band output from a signal generating section (130) to a mixer (111E) together with a local signal output from a local signal generator (112E) to convert the signal into a millimeter wave band signal, changes the frequency of the local signal in response to a test frequency for testing a device under test (DUT), and transmits the signal after frequency conversion by the frequency conversion section as the test signal for the device under test, The filter bank circuit (10E) according to claim 1 is provided in a stage subsequent to the frequency conversion unit, to which the signal after the frequency conversion is input, The changeover switch has a configuration in which the output portion functions as an input portion (20b1, 20c1) and the input portion functions as an output portion (20a1), a switching control means (151E) for controlling switching of the switch to which the frequency-converted signal is input to the input section so that the filter group including the filter circuit having a communication band corresponding to one of the test target frequencies is selected; A signal generating device comprising: a signal generator for transmitting the test signal from a selected one of the filters.

11. A method for controlling a filter bank circuit in a spectrum analyzer, a signal analyzer, or a signal generator using the filter bank circuit (10) according to claim 1, comprising: A setting step (S1, S11) of setting an analysis target frequency or a test target frequency; calculating the filter circuit to be selected from the filter group based on the set analysis target frequency or test target frequency (S2, S12); setting a path of the changeover switch corresponding to the selected filter circuit, and controlling the changeover switch to select the filter group to which the selected filter circuit belongs (S5, S13); a step (S5, S7, S9, S14) of measuring or extracting frequency components passing through the filter circuit calculated in the calculating step from the group of filters switched by the switching control step, for analysis or for sending a test signal; 13. A method for controlling a filter bank circuit comprising:

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