Waveguide attenuator, spectrum analyzer, signal analyzer, signal generator using the same, and control method for waveguide attenuator

Abstract

The present invention provides a waveguide attenuator capable of maintaining a constant attenuation over a wide bandwidth and improving the accuracy of signal levels even when applied to equipment requiring signal level adjustment, as well as a spectrum analyzer, signal analyzer, signal generator, and control method for a waveguide filter using the same. [Solution] The waveguide attenuator 10 is made up of a rectangular waveguide in which a waveguide 15 with a rectangular cross-section is formed, and the radio waves propagating within the waveguide 15 are attenuated by resistive films 23 provided along the length direction (Y direction) of the waveguide 15 on a pair of short side inner wall surfaces (inner wall surface 17a of groove 15a and inner wall surface 17b of groove 15b), and the resistive films 23 are provided in a form in which the width (dimension in the Z direction) gradually differs from the length (dimension in the Y direction).

Description

[Technical Field]

[0001] The present invention relates to a waveguide attenuator that arranges a resistive film inside the waveguide of a waveguide to attenuate a signal by a predetermined level, a spectrum analyzer using the same, a signal analyzer, a signal generator, and a control method for a waveguide filter. [Background Art]

[0002] In a transmission path formed by a waveguide, a waveguide attenuator that provides a predetermined attenuation is used to adjust a signal to a desired level and improve impedance matching. As this type of waveguide attenuator, for example, there is a structure in which a resistive film substrate is provided inside a waveguide.

[0003] As an example of a waveguide attenuator using a resistive film substrate, a structure is known in which a plurality of pad attenuators having resistors of different shapes formed on the surface of a plate-shaped resistor support are prepared, and a pad attenuator having a resistor pattern matching a desired attenuation is inserted through a longitudinally elongated hole provided at the center of the upper surface of a rectangular waveguide to adjust the attenuation. A fixed waveguide attenuator having such a structure has been conventionally known (for example, Patent Document 1, etc.). [Prior Art Literature] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Laid-Open No. 3-333501 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] In waveguide attenuators that attenuate signals by providing a resistive film inside a waveguide, such as the waveguide fixed attenuator described in Patent Document 1, if the dimension of the resistive film in the direction parallel to the propagation direction of radio waves inside the waveguide is defined as, for example, "length," and the dimension of the resistive film in the direction perpendicular to the propagation direction of radio waves inside the waveguide (the direction corresponding to the height of the waveguide) is defined as, for example, "width," then generally there is only one type of width for the resistive film implemented in a single waveguide attenuator (the width is constant).

[0006] Today, with the development of 5G and beyond in communication devices such as mobile terminals, and the progress of development of various equipment used for testing these communication devices, there is a growing demand for waveguide attenuators that can handle wide bandwidths, such as from 100 GHz to 180 GHz.

[0007] In this context, conventional waveguide attenuators employing a resistive film of constant width had a problem with non-uniform attenuation with respect to frequency when used in broadband applications. For example, if the resistive film width was narrow, the attenuation increased as the frequency increased, while if the resistive film width was wide, the attenuation decreased as the frequency increased. Therefore, for example, in broadband applications from 100 GHz to 180 GHz, conventional waveguide attenuators could not achieve flatness (constantness) of attenuation, and improvement was needed.

[0008] Furthermore, when using waveguide attenuators in devices that require adjustment to a desired signal level, such as spectrum analyzers and signal generators, if a waveguide attenuator that does not achieve constant attenuation for each frequency, as in conventional devices, is implemented, it affects the accuracy of the signal level of the signal under measurement in spectrum analyzers and the accuracy of the output signal level in signal generators. Here, while variations in signal levels can be suppressed by applying frequency-specific correction values ​​through calibration, it is desirable to suppress variations in the signal level of the original signal itself.

[0009] Furthermore, in waveguide attenuators with a resistive film substrate inside the waveguide, variations in the dimensions of the dielectric and resistive film substrate are prone to occur during the manufacturing process. In particular, due to the property that the thickness of the dielectric greatly affects the amount of attenuation, it was extremely difficult to achieve the desired amount of attenuation despite the aforementioned dimensional variations. For example, if the design value for the dielectric thickness is 150 μm, it may become 140 μm during manufacturing, which affects not only the amount of attenuation but also the slope of the attenuation with respect to frequency.

[0010] Thus, conventional waveguide attenuators, a) It is difficult to achieve constant attenuation over a wide bandwidth. b) If variations in the dimensions (especially thickness) of the dielectric material occur during the manufacturing process, it will take a lot of time and effort to achieve the desired attenuation. c) When applied to equipment such as spectrum analyzers and signal generators, the difficulty in achieving a constant attenuation rate is a major drawback, and it is prone to affecting the accuracy of the signal level. That was the problem.

[0011] The present invention aims to provide a waveguide attenuator that can maintain a constant attenuation over a wide bandwidth and improve the accuracy of the signal level even when applied to equipment that requires signal level adjustment, as well as a spectrum analyzer, signal analyzer, signal generator, and control method for a waveguide filter using the same. [Means for solving the problem]

[0012] To solve the above problems, the waveguide attenuator according to claim 1 of the present invention is a waveguide attenuator that is composed of a rectangular waveguide in which a waveguide (15) with a rectangular cross-section is formed, and attenuates radio waves propagating in the waveguide by a resistive film (23) provided on the inner wall surface (17a, 17b) of the waveguide along the propagation direction (Y direction) of radio waves in the waveguide, characterized in that the resistive film has a structure in which the dimension in the direction perpendicular to the propagation direction of radio waves in the waveguide (Z direction) (defined as "width") gradually differs from the dimension in the direction parallel to the propagation direction of radio waves in the waveguide (Y direction) (defined as "length").

[0013] With this configuration, the waveguide attenuator according to claim 1 of the present invention has a structure in which the resistive film has a gradually different dimension in the direction perpendicular to the propagation direction of radio waves in the waveguide (= "width") compared to the dimension in the direction parallel to the propagation direction of radio waves in the waveguide (= "length"). As a result, the amount of attenuation can be kept constant over a wide bandwidth, and the accuracy of the signal level can be improved even when applied to equipment that requires adjustment of the signal level.

[0014] Furthermore, in the waveguide attenuator according to claim 2 of the present invention, the inner wall surface of the waveguide is a pair of opposing inner wall surfaces, and the resistive film may be provided on either one or both of the pair of opposing inner wall surfaces of the waveguide.

[0015] With this configuration, the waveguide attenuator according to claim 2 of the present invention is not limited to a structure in which the resistive film is provided on one of the pair of inner wall surfaces, but can also be provided on both, thereby increasing the variations in the structure of the resistive film.

[0016] Furthermore, in the waveguide attenuator according to claim 3 of the present invention, the rectangular waveguide is divided into two along its longitudinal direction and comprises a first waveguide section (11a) having an inner wall surface (17a) corresponding to one of the pair of inner wall surfaces and a groove 15a corresponding to half of the waveguide, and a second waveguide section (11b) having an inner wall surface (17b) corresponding to the other of the pair of inner wall surfaces and a groove 15b corresponding to the remaining half of the waveguide, and the two sections are joined facing each other so that the waveguide is formed by the groove 15a and the groove 15b, and the resistive film is provided on a resistive film substrate (22) made of a dielectric, and the resistive film substrate may be configured to be detachably attached to the inner wall surface of the first waveguide section and the inner wall surface of the second waveguide section, respectively, with the resistive film provided on it.

[0017] With this configuration, the waveguide attenuator according to claim 3 of the present invention has a structure in which the resistive film substrate (dielectric) on which the resistive film is provided can be attached and detached. Therefore, by preparing various types of resistive film substrates in advance, even if variations in the dimensions (especially the thickness) of the dielectric or resistive film occur during the manufacturing stage, the desired attenuation amount can be obtained quickly and easily by trying to replace it with a different resistive film substrate.

[0018] Furthermore, in the waveguide attenuator according to claim 4 of the present invention, the resistive film substrate may be composed of a plurality of substrates (22a, 22b, 22c, 22d), and a plurality of resistive films (23a, 23b, 23c, 23d) may be provided on each of the plurality of substrates, and a structure in which the width of the resistive films gradually differs may be formed by mounting the plurality of substrates side by side.

[0019] With this configuration, the waveguide attenuator according to claim 4 of the present invention uses separate substrates on which resistive films of multiple widths and lengths are provided. Therefore, even if there are variations in the dimensions of the resistive film plate (dielectric) or resistive film during the manufacturing stage, it is possible to achieve a constant attenuation amount by replacing the resistive film substrate.

[0020] Furthermore, in the waveguide attenuator according to claim 5 of the present invention, the resistive film substrate may be configured of a single substrate, and a plurality of said resistive films may be provided on said single substrate in a form in which said widths are gradually different from each other.

[0021] With this configuration, the waveguide attenuator according to claim 5 of the present invention can be manufactured by providing a plurality of resistive films on a single substrate in a form in which the widths are gradually different, thereby improving manufacturability.

[0022] Furthermore, in the waveguide attenuator according to claim 6 of the present invention, said resistive film may have a structure with two types of said widths. With this configuration, since the waveguide attenuator according to claim 6 of the present invention has two types of resistive film widths, particularly when a resistive film is provided on each of a plurality of resistive film substrates, the work of replacing the resistive film substrate to achieve a desired attenuation amount can be reduced.

[0023] Furthermore, in the waveguide attenuator according to claim 7 of the present invention, said resistive film may have a structure in which said width changes continuously. With this configuration, the waveguide attenuator according to claim 7 of the present invention can further improve the manufacturability of the resistive films, particularly when a plurality of resistive films are provided on a single substrate in a form in which the widths are gradually different.

[0024] In order to solve the above problem, a spectrum analyzer according to claim 8 of the present invention comprises: a frequency conversion section (100) that attenuates a signal under measurement in a predetermined frequency range to a predetermined level by a waveguide attenuator (90), supplies the attenuated signal under measurement together with a local signal output from a local signal generator (112) to a mixer (111), and includes a filter (113) that extracts a signal in a predetermined intermediate frequency band from the mixed output; and a detector (120) that detects the signal in the intermediate frequency band, wherein the spectrum analyzer (1) changes the frequency of the local signal in accordance with an analysis target frequency to obtain spectrum characteristics of the signal under measurement, wherein the waveguide attenuator according to any one of claims 1 to 5 is used as said waveguide attenuator.

[0025] With this configuration, the spectrum analyzer according to claim 8 of the present invention has a structure in which the width of the resistive film mounted on the waveguide attenuator gradually varies with respect to the length, whereby the attenuation for each frequency achieved by the waveguide attenuator can be stabilized over a wide bandwidth. Therefore, it is possible to improve the accuracy of the signal level in the spectrum analyzer using the same.

[0026] In order to solve the above problem, the signal analyzer according to claim 9 of the present invention comprises: a frequency conversion unit (100A) that attenuates a signal under test in a predetermined frequency range to a predetermined level by a waveguide attenuator (90A), supplies the attenuated signal under test together with a local signal output from a local signal generator (112A) to a mixer (111A), and has a filter (113A) that extracts a signal in a predetermined intermediate frequency band from the mixing output of the mixer; and a signal analysis unit (153A) that analyzes the waveform of the intermediate frequency band signal after converting the signal into a digital signal by an ADC (125). In the signal analyzer (2) that analyzes the waveform of the signal under test by changing the frequency of the local signal in accordance with the frequency to be analyzed, the waveguide attenuator according to any one of claims 1 to 5 is used as said waveguide attenuator.

[0027] With this configuration, the signal analyzer according to claim 9 of the present invention has a structure in which the width of the resistive film mounted on the waveguide attenuator gradually varies with respect to the length, whereby the attenuation for each frequency achieved by the waveguide attenuator can be stabilized over a wide bandwidth. Therefore, it is possible to improve the accuracy of the signal level in the signal analyzer using the same.

[0028] To solve the above problems, the signal generator according to claim 10 of the present invention has a frequency conversion unit (100B) that provides a test signal in the intermediate frequency band output from a signal generator (130) together with a local signal output from a local signal generator (112B) to a mixer (111B) and converts it into a signal in a predetermined frequency range, and a waveguide attenuator (90B) that attenuates the frequency-converted signal to a predetermined level, and the frequency of the local signal is changed according to the test frequency for testing the object under test (DUT), and the frequency-converted signal from the frequency conversion unit is attenuated by the waveguide attenuator and then sent out as a test signal for the object under test, characterized in that the waveguide attenuator is the waveguide attenuator described in any one of claims 1 to 5.

[0029] With this configuration, the signal generator according to claim 10 of the present invention has a structure in which the width of the resistive film mounted on the waveguide attenuator gradually differs with respect to its length, thereby enabling the constant attenuation amount for each frequency by the waveguide attenuator to be achieved over a wide bandwidth, and thus making it possible to improve the accuracy of the signal level in a signal analyzer using this device.

[0030] To solve the above problems, the waveguide attenuator control method according to claim 11 of the present invention is a waveguide attenuator control method in a spectrum analyzer, signal analyzer, or signal generator using a waveguide attenuator (10) described in any one of claims 2 to 5, and is characterized by including: a setting step (S2, S22) of setting a target attenuation amount; a detection step (S11) of selecting the waveguide attenuator corresponding to the target attenuation amount, inputting a signal, and detecting the attenuation amount of the signal; a determination step (S12) of determining whether the detected attenuation amount is within an allowable range for the target value; and a replacement step (S15) of replacing the resistive film substrate attached to the inner wall surface of the first waveguide section and the inner wall surface of the second waveguide section with another resistive film substrate until an attenuation amount within an allowable range for the target value is detected.

[0031] With this configuration, the waveguide attenuator control method according to claim 11 of the present invention makes it possible to create a waveguide attenuator that can stabilize the attenuation amount over a wide bandwidth while replacing the resistive film substrate, and it is possible to easily achieve a constant attenuation amount even if there are variations in the dimensions of the resistive film substrate (dielectric) or resistive film during the manufacturing stage. Furthermore, when this waveguide attenuator is applied to equipment that requires signal level adjustment, it is possible to improve the accuracy of the signal level. [Effects of the Invention]

[0032] The present invention provides a waveguide attenuator that can maintain a constant attenuation over a wide bandwidth and improve the accuracy of signal levels even when applied to equipment that requires signal level adjustment, as well as a spectrum analyzer, signal analyzer, signal generator, and control method for a waveguide filter using the same. [Brief explanation of the drawing]

[0033] [Figure 1] This is an external view of a waveguide attenuator according to one embodiment of the present invention. [Figure 2] Figure 1 shows the cross-sectional structure of the waveguide attenuator with respect to surface A. [Figure 3] This is a plan view showing the inner surface configuration of the first waveguide section and the second waveguide section constituting a waveguide attenuator according to one embodiment of the present invention, where (a) shows the first waveguide section and (b) shows the second waveguide section. [Figure 4] This is a schematic diagram showing the arrangement of resistive films in the first waveguide section of a waveguide attenuator according to one embodiment of the present invention. [Figure 5] This is a schematic diagram showing another example of the arrangement of the resistive film in the first waveguide section of a waveguide attenuator according to one embodiment of the present invention. [Figure 6] This is a schematic diagram showing yet another example of the arrangement of the resistive film in the first waveguide section of a waveguide attenuator according to one embodiment of the present invention. [Figure 7] This is a schematic diagram showing another example of the arrangement of the resistive film in the first waveguide section of a waveguide attenuator according to one embodiment of the present invention. [Figure 8] This graph shows the relationship between the combination of lengths of two types of resistive films with different widths inside the waveguide of a waveguide attenuator according to one embodiment of the present invention, and the amount of attenuation. [Figure 9] This graph shows the simulation results of S21 for the D-band signal of a waveguide attenuator according to one embodiment of the present invention. [Figure 10] This graph shows the relationship between the combination of resistive film lengths and the amount of attenuation in a waveguide attenuator according to one embodiment of the present invention, taking into account the thickness of the resistive film substrate, and shows an example where the thickness of the resistive film substrate is thinner than the standard thickness. [Figure 11] This graph shows the relationship between the combination of resistive film lengths and the amount of attenuation in a waveguide attenuator according to one embodiment of the present invention, taking into account the thickness of the resistive film substrate, and shows an example where the thickness of the resistive film substrate is greater than the standard thickness. [Figure 12] This figure shows a general configuration of a spectrum analyzer using a waveguide attenuator according to one embodiment of the present invention. [Figure 13] This flowchart shows the signal measurement and control operation of a spectrum analyzer using a waveguide attenuator according to one embodiment of the present invention. [Figure 14] This flowchart shows the waveguide attenuator manufacturing process performed in conjunction with the signal measurement and control operation of a spectrum analyzer using a waveguide attenuator according to one embodiment of the present invention. [Figure 15] This figure shows a general configuration of a signal analyzer using a waveguide filter according to one embodiment of the present invention. [Figure 16] This figure shows a general configuration of a signal generator using a waveguide filter according to one embodiment of the present invention. [Figure 17] This flowchart shows the signal transmission control operation in a signal generator using a waveguide filter according to one embodiment of the present invention. [Modes for carrying out the invention]

[0034] The following describes embodiments of the waveguide attenuator according to the present invention, a spectrum analyzer, a signal analyzer, a signal generator, and a control method for the waveguide attenuator using the same.

[0035] (overview) The waveguide attenuator according to the present invention (see Figure 1) has an attenuation function that takes a signal in a high-frequency range, such as the D-band region (100 to 180 GHz), as input from one port, attenuates it to a predetermined level, and outputs it to the other port.

[0036] The waveguide attenuator according to the present invention is based on a rectangular waveguide having a waveguide with a rectangular cross-section (see waveguide 15 in Figures 1 and 2), and a resistive film is provided on a pair of opposing inner wall surfaces within the waveguide along the direction of radio wave propagation, and the resistive effect is used to attenuate the signal propagating within the waveguide.

[0037] In the case of a waveguide with a rectangular cross-section, the pair of inner wall surfaces mentioned above include the long side inner wall surfaces (the upper and lower pair of inner wall surfaces in Figure 2: corresponding to the inner diameter dimension "a" of the rectangular waveguide standard) and the short side inner wall surfaces (the left and right pair of inner wall surfaces in Figure 2: corresponding to the inner diameter dimension "b" of the rectangular waveguide standard). In this invention, the resistive film is attached to one of these short side inner wall surfaces. In such a structure, the structure of the resistive film provided on each of the opposing short side inner wall surfaces is defined as follows: the dimension in the direction of radio wave propagation within the waveguide (Y direction) is defined as "length," and the dimension in the direction perpendicular to the direction of radio wave propagation and corresponding to the height of the waveguide (Z direction) is defined as "width" (see Figure 3).

[0038] In conventional waveguide attenuators, the width of the resistive film is constant, making it difficult to maintain a constant attenuation across the entire high-frequency range, for example, 110 to 170 GHz. In this respect, the waveguide attenuator according to the present invention has a structure in which the width of the resistive film gradually changes with respect to the direction of radio wave propagation.

[0039] For example, in this invention, there are, for instance, two types of resistive films with different widths and multiple types with arbitrary lengths. By arranging these resistive films of multiple widths × lengths in a line along the direction of radio wave propagation on a pair of opposing short inner walls within the waveguide, a desired amount of attenuation can be achieved. In this way, the waveguide attenuator according to the present invention can stabilize the amount of attenuation in the high-frequency range of 110 to 170 GHz by having a structure in which the width of the resistive film gradually changes with respect to the direction of radio wave propagation.

[0040] The waveguide attenuator according to the present invention can be applied to various devices that handle the above-mentioned high-frequency band signals, such as a spectrum analyzer (see Figure 12) that measures the distribution (spectrum) of frequency components contained in a high-frequency signal, a signal analyzer (see Figure 15) that analyzes the waveform of the above-mentioned frequency components, and a signal generator (see Figure 16) that generates a test signal for testing the receiving sensitivity of a device under test (DUT).

[0041] According to the configuration of the spectrum analyzer, signal analyzer, and signal generator using the waveguide attenuator of the present invention, the amount of attenuation can be kept constant across the entire high-frequency range (e.g., 110 to 170 GHz), and while the structure is easy to manufacture, it is capable of high-precision measurement, analysis, and DUT testing of high-frequency signals.

[0042] In the following sections, we will sequentially describe embodiments of the waveguide attenuator 10 and the resistive film 23 used therein according to the present invention (see Figures 1 to 7), various simulation results related to the waveguide attenuator 10 (see Figures 8 to 11), embodiments of the spectrum analyzer 1 using the waveguide attenuator 10 (see Figures 12, 13, and 14), embodiments of the signal analyzer 2 using the waveguide attenuator 10 (see Figure 15), and embodiments of the signal generator 3 using the waveguide attenuator 10 (see Figures 16 and 17).

[0043] (Waveguide attenuator) First, the configuration of the waveguide attenuator 10 according to one embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 shows an external view of the waveguide attenuator 10 according to one embodiment of the present invention, and Figure 2 shows the structure of the cross-section of the waveguide attenuator 10 on surface A in Figure 1. Figure 3 is a plan view showing the internal structure of the first waveguide section 11a and the second waveguide section 11b that constitute the waveguide attenuator 10 according to one embodiment of the present invention, where (a) shows the first waveguide section 11a and (b) shows the second waveguide section 11b.

[0044] Figures 1 to 3 include orthogonal three-dimensional coordinate indices to facilitate understanding the structure of each element of the waveguide attenuator 10 (including the waveguide 15 and resistive film 23). According to the orthogonal three-dimensional coordinate indices, the X, Y, and Z directions refer to the width, length, and height directions, respectively, for the external appearance of the waveguide attenuator 10 and the structure of the waveguide 15 (see Figures 1 and 2). For the structure of the resistive film 23 provided within the waveguide 15, as described above, the Y and Z directions refer to the length and width directions, respectively (see Figure 3).

[0045] As shown in Figure 1, the waveguide attenuator 10 according to this embodiment has an overall rectangular parallelepiped shape that is long in one direction (Y direction), and is constructed by combining a first waveguide section 11a and a second waveguide section 11b, each having an equivalent shape (rectangular parallelepiped), such that their front surfaces 12a and 12b face each other and are in close contact and joined.

[0046] The waveguide attenuator 10 has a structure that conforms to the standard specification for rectangular waveguides, for example, WR6.5. The WR6.5 standard specifies conditions such as a frequency range of 110 to 170 [GHz], a frequency band of [D band], and an inner diameter of 1.651 × 0.8255 (width-to-height ratio of 2:1) [mm]. However, the structure of the waveguide attenuator 10 according to this embodiment is not limited to WR6.5 and can be applied to various other standards as well.

[0047] The first waveguide section 11a and the second waveguide section 11b are made of, for example, aluminum, copper, or brass. In the case of those made of copper or brass, the entire inner surface of the waveguide 15 may be gold-plated.

[0048] As shown in Figure 1, the first waveguide section 11a and the second waveguide section 11b each have grooves 15a and 15b formed therein, which constitute a waveguide 15 with a rectangular cross-section. By arranging them opposite each other so that the waveguide 15 is formed by both grooves 15a and 15b, a rectangular waveguide structure is realized. Each groove 15a and 15b is sized to divide the waveguide 15 in half, and together they form a waveguide 15 with an inner diameter corresponding to the aforementioned rectangular waveguide standard (WR6.5). The waveguide attenuator 10 has openings 13 and 14 of the waveguide 15 at both ends in the longitudinal direction, but there is no directionality of input and output of radio waves (distinction between input end and output end).

[0049] The first waveguide section 11a and the second waveguide section 11b are detachably mounted on their inner wall surfaces, which correspond to a pair of short-side inner wall surfaces of the rectangular waveguide 15 in the rectangular waveguide structure, using substrate mounting holes 19a, 19a. A resistive film 23 (not shown in Figure 1) is provided on the resistive film substrates 22, 22 in the manner described above. The resistive film substrates 22 and resistive film 23 will be described in detail later with reference to Figures 2 and 3.

[0050] As shown in Figure 2, in the waveguide attenuator 10 according to this embodiment, the first waveguide section 11a corresponds to the left half of the figure and has a rectangular groove 15a on the surface of the front side surface 12a facing the second waveguide section 11b (corresponding to the right half of the figure), with an appropriate height H in the Z direction and an appropriate depth D in the X direction. The groove 15a is formed in a rectangular shape with a uniform height H and depth D throughout the entire Y (length) direction of the first waveguide section 11a, from one end to the other.

[0051] The inner walls of the U-shaped groove 15a (which is an inverted U-shape when viewed from the front in Figure 2) are referred to as the inner wall surfaces 16a, 17a, and 18a of the groove 15a, respectively. In the first waveguide section 11a, substrate mounting holes 19a, 19a are provided at the corner portions at both ends of the inner wall surface 17a of the groove 15a (the portions that intersect with the inner wall surfaces 16a and 17a). The substrate mounting holes 19a, 19a can be formed, for example, by cutting a part of each corner portion inward and then cutting (cutting) them out with a wire or the like so that they penetrate in the longitudinal direction of the first waveguide section 11a.

[0052] The resistive film substrate 22 is mounted (fitted) into the substrate mounting holes 19a, 19a along the inner wall surface 17a of the groove 15a. The resistive film substrate 22 is made of a dielectric material, such as known material such as quartz or alumina, and it is desirable that a material suitable for the operating frequency be selected.

[0053] As shown in Figures 2 and 3, the resistive film substrate 22 is composed of a thin dielectric plate-like member having a width and thickness and an appropriate length that allows it to be movably fitted in the Y direction between the substrate mounting holes 19a, 19a. The resistive film substrate 22 may be composed of multiple substrates, each having different appropriate lengths, or it may be composed of a single substrate having an appropriate length.

[0054] Regardless of the above configuration, the resistive film substrate 22 can be mounted by inserting one end in the longitudinal direction into the substrate mounting holes 19a, 19a from, for example, the front side of the paper in Figure 2, and then pushing it forward (towards the back of the paper) until it is properly positioned inside the first waveguide section 11a. The mounted resistive film substrate 22 can also be removed from the mounted state by performing the reverse operation. Thus, the resistive film substrate 22 has a structure that allows it to be attached and detached (inserted and removed) along the inner wall surface 17a of the groove 15a of the first waveguide section 11a using the substrate mounting holes 19a, 19a.

[0055] The resistive film substrate 22 has a resistive film 23 provided on its surface. The resistive film 23 is an element that determines the amount of attenuation of radio waves within the waveguide 15, and is made of a resistive material such as nichrome or tantalum nitride. It is desirable that the resistive film 23 be made of a material suitable for the operating frequency. The structure and mounting method of the resistive film 23 will be explained in detail later with reference to Figures 4 to 7.

[0056] The second waveguide section 11b also has a structure similar to that of the first waveguide section 11a. As shown in Figure 2, the second waveguide section 11b corresponds to the right half of the figure and has a rectangular groove 15b on the surface of the front side surface 12b facing the first waveguide section 11a (corresponding to the left half of the figure), with an appropriate height H in the Z direction and an appropriate depth D in the X direction. The groove 15b is formed in a rectangular shape with a uniform height H and depth D throughout the entire Y (length) direction of the second waveguide section 11b, from one end to the other.

[0057] In Figure 2, the inner walls of the U-shaped groove 15b are referred to as inner wall surfaces 16b, 17b, and 18b, respectively. In the second waveguide section 11b, substrate mounting holes 19b, 19b are provided at the corners of both ends of the inner wall surface 17b (where it intersects with the inner wall surfaces 16b and 18b). The substrate mounting holes 19b, 19b are equivalent to the substrate mounting holes 19a, 19a described above.

[0058] The resistive film substrate 22 is mounted (fitted) in the substrate mounting holes 19b, 19b along the inner wall surface 17b of the groove 15b. The resistive film substrate 22 is equivalent to the one mounted on the inner wall surface 17a of the groove 15a of the first waveguide section 11a, and is configured to be removable (inserted and removed) within the groove 15b of the second waveguide section 11b along the inner wall surface 17b using the substrate mounting holes 19b, 19b. The resistive film substrate 22 is provided with a resistive film 23 of a predetermined width (for example, widths W0 and W1)1. Note that the substrate mounting holes 19b, 19b and the opposite substrate mounting holes 19a, 19a can be implemented in other forms, such as having a square cross-sectional shape, as long as they can detachably hold the resistive film substrate 22.

[0059] As shown in Figure 2, the first waveguide section 11a and the second waveguide section 11b, having the structures described above, are joined together at close range to form a waveguide attenuator 10 having a waveguide 15 with a rectangular cross-section consisting of grooves 15a and 15b.

[0060] In this waveguide attenuator 10, the inner wall surface 17a of the first waveguide section 11a and the inner wall surface 17b of the second waveguide section 11b correspond to a pair of opposing short-side inner wall surfaces in the waveguide 15. As described above, a resistive film substrate 22 is detachably mounted on this pair of short-side inner wall surfaces, and a resistive film 23 having a predetermined width is provided on the resistive film substrate 22.

[0061] In this embodiment, the resistive film 23 may have, for example, two different widths and multiple different lengths. The width of the resistive film 23 is not limited to two types. While having many width variations of the resistive film 23 contributes to improving the attenuation function of the waveguide attenuator 10, considering the work of replacing the resistive film substrate 22 along with the resistive film during the manufacturing process of the waveguide attenuator 10, having many width variations complicates the replacement work (in the case of conventional resistive films with a constant width, even more substrates and replacement work would be required). To avoid this complexity, it is desirable to limit the width of the resistive film 23 to at most three to four types. The resistive film 23 may also be tapered in shape, with a width that changes gradually (continuously) (see Figures 6 and 7).

[0062] Next, embodiments of the resistive film substrate 22 and the resistive film 23 provided thereon in the waveguide attenuator 10 according to this embodiment will be described in detail with reference to Figures 4 to 7.

[0063] Figure 3 is a plan view showing the inner surface configuration of the first waveguide section 11a and the second waveguide section 11b that constitute the waveguide attenuator 10 according to this embodiment, where (a) shows the first waveguide section 11a and (b) shows the second waveguide section 11b.

[0064] In the waveguide attenuator 10 according to this embodiment, a resistive film substrate 22, on which a resistive film 23 having the planar shape shown in Figure 3(a) is provided, is detachably mounted on the inner wall surface 17a of the groove 15a in the first waveguide section 11a. Here, the resistive film substrate 22 is composed of resistive film substrates 22a, 22b, 22c, and 22d arranged sequentially in the Y direction from the opening 13 to the opening 14. The dimensions of the resistive film substrates 22a, 22b, 22c, and 22d in the direction of radio wave propagation (Y direction) inside the waveguide 15, i.e., the length, are such that each of the resistive film substrates 22a, 22b, 22c, and 22d has an appropriate length.

[0065] Resistive films 23a, 23b, 23c, and 23d are provided on resistive film substrates 22a, 22b, 22c, and 22d, respectively, by depositing the aforementioned material. Regarding the dimensions in the Z direction, i.e., the width, of the resistive films 23a, 23b, 23c, and 23d, resistive films 23c and 23d have a width W0, while resistive films 23a and 23b have a smaller width (for example, W1). Thus, the resistive films 23a, 23b, 23c, and 23d have a structure in which their widths gradually differ with respect to the length in the direction of radio wave propagation (Y direction) inside the waveguide 15.

[0066] In Figure 3(a), the resistive films 23a and 23d, positioned at both ends in the longitudinal direction, have triangular notches formed at their tips. These notches are designed to prevent reflection of signals input from the front of the tip.

[0067] On the other hand, in the second waveguide section 11b, a resistive film substrate 22 having a resistive film 23 with a planar shape as shown in Figure 3(b) is detachably mounted on the inner wall surface 17b of the groove section 15b. This resistive film substrate 22 is equivalent to the resistive film substrate 22 mounted in the first waveguide section 11a. That is, the arrangement structure of the resistive film substrates 22a, 22b, 22c, and 22d in the second waveguide section 11b is equivalent to that of the resistive film substrates 22a, 22b, 22c, and 22d in the groove section 15a of the first waveguide section 11a, except that the arrangement of the resistive film substrates 22a, 22b, 22c, and 22d in the resistive film substrate 22 is reversed left to right when viewed from the front.

[0068] The first waveguide section 11a and the second waveguide section 11b, whose inner surfaces have the structure shown in Figure 3, are joined together by bringing their respective front surfaces 12a and 12b to face each other, thereby realizing the structure of a waveguide attenuator 10 in which a resistive film 23 is provided on each of the pair of short inner wall surfaces of the waveguide 15 (inner wall surface 17a of the first waveguide section 11a and inner wall surface 17b of the second waveguide section 11b (see Figure 2)) in a manner in which the width gradually changes along the longitudinal direction of the waveguide 15.

[0069] As described above with reference to Figures 1 to 3, the waveguide attenuator 10 according to this embodiment is characterized in that the structure of the resistive film 23 provided on a pair of opposing inner wall surfaces 17a and 17b of the waveguide 15 along the direction of radio wave propagation (Y direction) has a structure in which the dimension (= width) in the direction perpendicular to the direction of radio wave propagation (Z direction) gradually differs from the dimension (= "length") in the direction parallel to the direction of radio wave propagation within the waveguide 15 (Y direction), and the resistive film 23 is detachable from the inner wall surfaces 17a and 17b.

[0070] With this structure, the waveguide attenuator 10 according to this embodiment can achieve constant attenuation over the entire frequency range of a wide bandwidth (for example, the D band) compared to conventional attenuators that have a resistive film of a certain width inside the waveguide.

[0071] In one embodiment described with reference to Figures 1 to 3, a resistive film 23 having the above structure (a structure in which the dimension in the Z direction (= width) within the waveguide 15 gradually differs from the dimension in the Y direction (= "length")) is provided on a pair of opposing inner wall surfaces 17a and 17b of the waveguide 15. However, the present invention is not limited to this, and the resistive film 23 may be provided on either one (one side) of the pair of opposing inner wall surfaces 17a and 17b of the waveguide 15.

[0072] Next, various forms of the resistive film 23 of the waveguide attenuator 10 according to this embodiment will be described with reference to Figures 4 to 7.

[0073] In this embodiment, the waveguide attenuator 10 has a structure in which the resistive films 23 provided on a pair of short inner wall surfaces 17a and 17b of the waveguide 15 have gradually different widths, and the resistive film substrate 22 on which the resistive films 23 are provided is detachable. As long as these features are not impaired, various arrangements of the resistive films 23 can be selected. In the following, the arrangement of the resistive films 23 will be described using the first waveguide section 11a (see Figure 3(a)) of the first waveguide section 11a and second waveguide section 11b of the waveguide attenuator 10 as an example, but it goes without saying that the second waveguide section 11b (see Figure 3(b)) also has a similar arrangement.

[0074] Figure 4 shows the arrangement of the resistive films 23 (see Figure 3) mounted on the waveguide attenuator 10 according to this embodiment. Four resistive film substrates 22a, 22b, 22c, and 22d, each provided with resistive films 23a, 23b, 23c, and 23d respectively, are arranged in a row, realizing an arrangement of resistive films 23 whose width gradually changes with respect to the direction of radio wave propagation (changing between width W0 and width W1). In the example in Figure 4, the resistive films 23a, 23b, 23c, and 23d provided on the resistive film substrates 22a, 22b, 22c, and 22d arranged in a row may appear to have gaps between them due to the precision of the vapor deposition formation on each individual resistive film substrate 22a, 22b, 22c, and 22d, but from the viewpoint of electrical connection, it is desirable that they be connected without gaps.

[0075] Figure 5 shows another arrangement of the resistive films 23 mounted on the waveguide attenuator 10 according to this embodiment, in which resistive films 23a, 23b, 23c, and 23d are arranged on the surface of a single resistive film substrate 22 in the same arrangement as shown in Figure 4.

[0076] Figure 6 shows yet another arrangement of the resistive film 23 mounted in the waveguide attenuator 10 according to this embodiment, and includes tapered resistive films 23b1 and 23c1. In this example, multiple resistive film substrates 22a, 22b, 22c, and 22d (the same arrangement as in Figure 4), each provided with resistive films 23a, 23b1, 23c, and 23d1 respectively, are arranged in a row. This arrangement structure includes tapered resistive films 23b1 and 23c1, and although it cannot be said that there are two types of widths, it realizes an arrangement of resistive films 23 in which the width gradually changes with respect to the direction of radio wave propagation.

[0077] Figure 7 shows another arrangement of the resistive films 23 mounted on the waveguide attenuator 10 according to this embodiment, in which resistive films 23a, 23b1, 23c1, and 23d are arranged in a row on the surface of a single resistive film substrate 22 in the same arrangement as shown in Figure 6.

[0078] The arrangement of the resistive films 23 shown in Figures 4 to 7 is merely an example. In the present invention, one or more resistive film substrates 22, each having a wider variety of widths and lengths, are prepared. From these resistive film substrates 22, one or more substrates 22 necessary to obtain the desired attenuation can be selected to realize an arrangement of resistive films 23 in a single row.

[0079] (Manufacturing procedures and results of various simulations related to manufacturing) The waveguide attenuator 10 according to this embodiment can be manufactured by selecting one or more resistive film substrates 22 corresponding to the desired attenuation amount from among the multiple resistive film substrates 22 prepared as described above, and attaching them to the inner wall surface 17a of the first waveguide section 11a and the inner wall surface 17b of the second waveguide section 11b, respectively.

[0080] Furthermore, the selection of the resistive film substrate 22 must be made with consideration of the relationship between frequency, attenuation, and the size of the resistive film 23. For example, a thick resistive film 23 has the characteristic that the attenuation decreases as the frequency increases, while a thin resistive film 23 has the characteristic that the attenuation increases as the frequency increases. Therefore, when aiming to flatten the attenuation, it is desirable to select a resistive film substrate 22 on which a resistive film 23 of an appropriate size is attached, taking this characteristic into account.

[0081] The detailed manufacturing procedure will be described later with reference to Figure 14, but in manufacturing the waveguide attenuator 10, first, the desired attenuation amount is determined, and based on the results of simulations performed in advance, a resistive film substrate 22 or a combination of resistive film substrates 22 corresponding to that attenuation amount is selected.

[0082] Next, the selected resistive film substrate 22, or a resistive film substrate 22 that matches the combination, is mounted on the inner wall portion 17a of the groove portion 15a of the first waveguide portion 11a and the inner wall portion 17b of the groove portion 15b of the second waveguide portion 11b, respectively (see Figures 4 to 7).

[0083] After mounting the resistive film substrate 23, a preliminary assembly is performed to combine the first waveguide section 11a and the second waveguide section 11b to form the waveguide attenuator 10 (see Figure 1).

[0084] Next, while inputting a signal to the temporarily assembled waveguide attenuator 10, the amount of attenuation at this time is measured using an externally connected network analyzer or the like. The resistive films 23 attached to the inner wall portion 17a of the first waveguide section 11a and the inner wall portion 17b of the second waveguide section 11b are swapped until the measured amount of attenuation at this time falls within the acceptable range relative to the predetermined desired attenuation amount (set value).

[0085] During the above replacement process, if it is determined that the difference is within an acceptable range, the resistive film 23 is fixed in place, and the waveguide attenuator 10 is assembled to complete the process. Through the above manufacturing process, a waveguide attenuator 10 having a desired attenuation amount for broadband (e.g., D-band) signals can be manufactured.

[0086] Next, various simulation data referenced in the manufacturing process of the waveguide attenuator 10 according to this embodiment will be explained with reference to Figures 8 to 11.

[0087] Figure 8 shows a graph illustrating the relationship between the length combinations of resistive films 23 with two different widths inside the waveguide of the waveguide attenuator 10 according to this embodiment and the amount of attenuation. In Figure 8, the horizontal axis represents the amount of attenuation [dB], and the vertical axis represents the length of the resistive film 23 [mm]. Regarding the width of the resistive film 23, the upper line segment in the graph corresponds to a narrow width (=W1) (resistive films 23a, 23b, etc. in Figure 4), and the lower line segment corresponds to a wide width (=W0) (resistive films 23c, 23d, etc. in Figure 4).

[0088] The graph in Figure 8 shows that, for example, when manufacturing a waveguide attenuator 10 with an attenuation of 30 dB, a combination of a narrow resistive film 23 with a length of 12 mm and a wide resistive film 23 with a length of 6 mm is suitable. For other attenuations, the lengths of the narrow and wide resistive films 23 required to obtain those attenuations can also be easily read from the same graph. Thus, the graph in Figure 8 is useful for smoothly carrying out the process of "selecting combinations based on the results of simulations conducted in advance" in the manufacturing procedure described above.

[0089] Figure 9 is a graph showing the simulation results of S21 for D-band signals of waveguide attenuators 10 manufactured by the procedure described above to achieve each desired attenuation. In Figure 9, the vertical axis is S21 (insertion loss), and the horizontal axis is frequency. In Figure 9, for example, for waveguide attenuators 10 for an attenuation of 30 dB, the range of variation from the target attenuation of 30 dB at the time of manufacture is shown by the width between the two dotted lines, and it can be seen that the range of variation can be kept extremely small (within the acceptable range) throughout the entire frequency range of 100 to 180 GHz. According to the graph in Figure 9, it can be seen that for other attenuations (target values) as well, the variation in attenuation is extremely small throughout the entire frequency range of 100 to 180 GHz, and the attenuation is constant.

[0090] Figure 10 is a graph showing the relationship between the length combination of the resistive film 23 and the attenuation amount, taking into account the thickness of the resistive film substrate 22 on which the resistive film 23 is provided. It shows an example where the thickness of the resistive film substrate 22 is thinner than the standard thickness. The reason why the graph in Figure 10 differs from the graph in Figure 8 is that it reflects the effect of the resistive film substrate 22 on which the resistive film 23 is provided being formed thinner than the reference thickness (standard thickness) in the graph in Figure 8.

[0091] Even if resistive films 23 of the same size are provided, the attenuation will be smaller if the thickness of the resistive film substrate 22 is thinner than standard. To compensate for the decrease in attenuation due to the thinner resistive film substrate 22, one method is to increase the length of the resistive film 23. In light of this method, the graph shown in Figure 10 shows that, for example, in order to reliably manufacture a waveguide attenuator 10 having an attenuation of 30 [dB], a combination of a narrow-width resistive film 23 with a length of slightly less than 15 mm and a wide-width resistive film 23 with a length of slightly less than 7 mm is suitable.

[0092] This indicates that a longer length should be selected for the resistive film substrate 22 than the length when it is of standard thickness (12 mm for the narrow resistive film 23 and 6 mm for the wide resistive film 23), as can be read from the graph in Figure 8. The same can be read for other attenuation values ​​from the graph in Figure 10. As a result, when the resistive film substrate 22 is formed thinner than the standard thickness, a waveguide attenuator 10 that achieves the target attenuation can be manufactured by selecting longer lengths for the narrow resistive film 23 and the wide resistive film 23.

[0093] Figure 11 is a graph showing the relationship between the length combination of the resistive film 23 and the attenuation amount, taking into account the thickness of the resistive film substrate 22 on which the resistive film 23 is provided. It shows an example where the thickness of the resistive film substrate 22 is greater than the standard thickness. The reason why the graph in Figure 11 differs from the graph in Figure 8 is that it reflects the effect of the resistive film substrate 22 on which the resistive film 23 is provided being formed to be thicker than the reference thickness (standard thickness) in the graph in Figure 8.

[0094] Even if resistive films 23 of the same size are provided, the attenuation will increase if the thickness of the resistive film substrate 22 is thicker than standard. To compensate for the increase in attenuation due to the increased thickness of the resistive film substrate 22, one method is to shorten the length of the resistive film 23. In light of this method, the graph shown in Figure 11 shows that, for example, when manufacturing a waveguide attenuator 10 with an attenuation of 30 [dB], a combination of a narrow-width resistive film 23 with a length of slightly less than 10 mm and a wide-width resistive film 23 with a length of slightly less than 6 mm is suitable.

[0095] This indicates that, as can be read from the graph in Figure 8, the resistive film substrate 22 should be selected to be shorter than the length when it is of standard thickness (12 mm for the narrow-width resistive film 23 and 6 mm for the wide-width resistive film 23). The same can be read from the graph in Figure 11 for other attenuation values. This means that when the resistive film substrate 22 is formed to be thicker than the standard thickness, a waveguide attenuator 10 that achieves the target attenuation can be manufactured by selecting shorter lengths for the narrow-width resistive film 23 and the wide-width resistive film 23.

[0096] As described above, the waveguide attenuator 10 according to this embodiment is composed of a rectangular waveguide in which a rectangular waveguide 15 is formed, and attenuates the radio waves propagating within the waveguide 15 by a resistive film 23 provided on the inner wall surfaces 17a and 17b of the waveguide 15 along the direction of propagation of radio waves within the waveguide 15 (Y direction), wherein the resistive film 23 has a structure in which the dimension in the direction perpendicular to the direction of propagation of radio waves within the waveguide 15 (Z direction) (defined as "width") gradually differs from the dimension in the direction parallel to the direction of propagation of radio waves within the waveguide 15 (Y direction) (defined as "length").

[0097] With this configuration, the waveguide attenuator 10 according to this embodiment has a structure in which the resistive film 23 has a gradually different dimension in the direction perpendicular to the propagation direction of radio waves in the waveguide 15 (= "width") compared to the dimension in the direction parallel to the propagation direction of radio waves in the waveguide 15 (= "length"). As a result, the amount of attenuation can be kept constant over a wide bandwidth, and the accuracy of the signal level can be improved even when applied to equipment that requires signal level adjustment.

[0098] Furthermore, in the waveguide attenuator 10 according to this embodiment, the inner wall surface of the waveguide is a pair of opposing inner wall surfaces 17a and 17b, and the resistive film 23 is provided on either one or both of the pair of opposing inner wall surfaces 17a and 17b of the waveguide 15.

[0099] With this configuration, the waveguide attenuator 10 according to this embodiment is not limited to a structure in which the resistive film 23 is provided on either one of the pair of inner wall surfaces 17a and 17b, but can also be provided on both, thereby increasing the variations in the structure of the resistive film.

[0100] Furthermore, the waveguide attenuator 10 according to this embodiment is composed of a rectangular waveguide which is divided into two along its longitudinal direction, and consists of a first waveguide section 11a having one of a pair of inner wall surfaces 17a and 17b and a groove 15a corresponding to half of the waveguide 15, and a second waveguide section 11b having the other inner wall surface 17b and a groove 15b corresponding to the remaining half of the waveguide 15, and can be joined facing each other so that the waveguide 15 is formed by the grooves 15a and 15b, and the resistive film 23 is provided on a resistive film substrate 22 made of dielectric material, and the resistive film substrate 22 is configured to be detachable from the inner wall surface 17a of the first waveguide section 11a and the inner wall surface 17b of the second waveguide section 11b, respectively, with the resistive film 23 provided on it.

[0101] With this configuration, the waveguide attenuator 10 according to this embodiment has a structure in which the resistive film substrate 22 (dielectric) on which the resistive film 23 is provided can be attached and detached. By preparing various types of resistive film substrates 22 in advance, even if variations in the dimensions (especially the thickness) of the dielectric or resistive film 23 occur during the manufacturing stage, the desired attenuation amount can be obtained quickly and easily by trying to replace it with a different resistive film substrate 22.

[0102] Furthermore, in the waveguide attenuator 10 according to this embodiment, the resistive film substrate 22 is composed of a plurality of resistive film substrates 22a, 22b, 22c, and 22d, and a plurality of resistive films 23a, 23b, 23c, and 23d are provided on each of the plurality of resistive film substrates 22a, 22b, 22c, and 22d, respectively, and by mounting the plurality of resistive film substrates 22a, 22b, 22c, and 22d side by side, a structure is formed in which the width of the resistive films 23 gradually differs.

[0103] With this configuration, the waveguide attenuator 10 according to this embodiment uses separate substrates for the resistive film substrate 22, each having a resistive film 23 of multiple widths and lengths. Therefore, even if there are variations in the dimensions of the resistive film substrate 22 (dielectric) or the resistive film during the manufacturing stage, it is possible to achieve a constant attenuation amount by replacing the resistive film substrate 22.

[0104] Furthermore, the waveguide attenuator 10 according to this embodiment has a configuration in which the resistive film substrate 22 is made up of a single resistive film substrate 22, and a plurality of resistive films 23 are provided on the single resistive film substrate 22 in a form in which their widths gradually differ.

[0105] With this configuration, the waveguide attenuator 10 according to this embodiment can be manufactured by providing a single resistive film substrate 22 with multiple resistive films 23 arranged in a manner that gradually changes in width, thereby improving manufacturability.

[0106] Furthermore, the waveguide attenuator 10 according to this embodiment has a structure in which the resistive film 23 has two different widths. Because the waveguide attenuator 10 according to this embodiment has two different widths for the resistive film 23, in particular, when a resistive film 23 is provided on each of a plurality of resistive film substrates 22, the work of replacing the resistive film substrates 22 to achieve the desired attenuation amount can be reduced.

[0107] Furthermore, in the waveguide attenuator 10 according to this embodiment, the resistive film 23 has a tapered structure in which the width changes continuously. With this configuration, the waveguide attenuator 10 according to this embodiment can further improve the manufacturability of the resistive film 23, especially when multiple resistive films 23 are provided in a tapered shape on a single resistive film substrate 22.

[0108] Next, embodiments of devices to which the waveguide attenuator 10 according to this embodiment is applied will be described. The waveguide attenuator 10 according to this embodiment can be applied to the waveguide section of various devices that handle high-frequency signals such as the D band. Typical devices of this type include, for example, spectrum analyzers, signal analyzers, and signal generators.

[0109] The waveguide attenuator 10 according to this embodiment is often implemented in the form of a waveguide attenuator bank circuit (attenuator bank circuit: ATT bank circuit) when applied to spectrum analyzers, signal analyzers, and signal generators. The ATT bank circuit comprises multiple waveguide attenuators 10 corresponding to different attenuation levels, and has a configuration that allows selection of the waveguide attenuator 10 having the desired attenuation level by a switch or the like. Each waveguide circuit 10 is connected to the input and output waveguides using well-known techniques such as flanges or screws. Below, embodiments of spectrum analyzers, signal analyzers, and signal generators to which the ATT bank circuit is applied to the circuit portion where signal level adjustment is required will be described. However, the waveguide attenuator 10 according to this embodiment is not limited to the three types of measuring instruments described above, but can be applied to measuring instruments that handle wireless signals in general.

[0110] (Spectrum analyzer) Figure 12 shows a general configuration of a spectrum analyzer 1 employing an ATT bank circuit 90 using multiple waveguide attenuators 10 according to this embodiment. The spectrum analyzer 1 is assumed to have broadband signal analysis capabilities.

[0111] The spectrum analyzer 1 according to this embodiment includes an ATT bank circuit 90, a frequency conversion unit 100, a detector 120, a control unit 150, an operation unit 160, and a display unit 161. The ATT bank circuit 90 has a configuration that allows switching the attenuation amount in 1 dB increments over an attenuation range of, for example, 1 to 30 dB. The control of switching the attenuation amount of the ATT bank circuit 90 can be performed, for example, by the variable attenuation control unit 151 of the control unit 150, which will be described later.

[0112] The frequency conversion unit 100 is comprised of a mixer 111, a local signal generator 112, and a filter 113.

[0113] The mixer 111 is a functional unit that acts as a frequency conversion means, which converts the signal under measurement from an RF frequency to an intermediate frequency signal (IF frequency) by mixing the signals of each frequency component (RF frequency) attenuated by a predetermined amount output from the ATT bank circuit 90 with the local signal input from the local signal generator 112, and outputs it.

[0114] The local signal generator 112 generates a local signal for transmission to the mixer 111 based on the local signal (reference signal) input from the local oscillator signal source 9.

[0115] The filter 113 is a filtering unit that receives the IF signal frequency-converted by the mixer 111, passes only the frequency components of a predetermined band of the input IF signal through, and inputs it to the detector 120.

[0116] The detector 120 is a processing circuit that detects the intensity of each input band signal (IF) that has passed through the filter 113.

[0117] The control unit 150 has a control function that comprehensively controls the entire spectrum analyzer 1, including the ATT bank circuit 90, as well as an attenuation variable control unit 151, a frequency sweep control unit 152, and a spectrum data acquisition unit 153. The control unit 150 may be the control unit of the spectrum analyzer 1 main unit, or it may be configured as a separate device such as a PC (personal computer).

[0118] The variable attenuation control unit 151 is a functional unit that switches and controls multiple waveguide attenuators 10 that constitute the ATT bank circuit 90 to set a desired variable attenuation amount.

[0119] The frequency sweep control unit 152 is a functional unit that performs frequency sweep control, which changes the frequency of the local signal output by the local signal generator 112 to the mixer 111 within a specified frequency range, based on the local signal (reference signal) input from the local oscillator signal source 9.

[0120] The spectrum data acquisition unit 153 acquires spectrum data including the intensity of signal components in a desired frequency band within the analysis target frequency range detected by the detector 120, and performs display control and other operations on the display unit 161.

[0121] The operation unit 160 has input means such as various keys, switches, and buttons, and is operated by the user when making various settings related to the measurement of the signal under test. The display unit 161 is a functional unit that is composed of, for example, a liquid crystal display and displays setting screens and measurement results related to the measurement of the signal under test.

[0122] In the spectrum analyzer 1 shown in Figure 12, the broadband signal under measurement (input signal) is attenuated via the ATT bank circuit 90 and supplied to the mixer 111 of the frequency conversion unit 100, where it is mixed with the local signal output from the local signal generator 112. From the mixed output, a signal in a predetermined intermediate (IF) frequency band is extracted by the filter 113. The frequency of the local signal is swept and varied by the frequency sweep control unit 152 of the control unit 150 to correspond to the desired analysis target frequency range. The signal components in that desired analysis target frequency range are extracted as signals in the intermediate frequency band over time, and the intensity of these signals is detected by the detector 120.

[0123] 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, according to the analysis target frequency set by the operation unit 160, as spectrum data, and displays the spectrum data on the display unit 161.

[0124] The variable attenuation control unit 151 selects and controls the waveguide attenuator 10 by switching a switch according to a preset attenuation amount, and variably controls the attenuation amount of the ATT bank circuit 90 so that it becomes the set attenuation amount.

[0125] The frequency sweep control unit 152 performs frequency sweep control related to frequency conversion in the frequency conversion unit 100.

[0126] In the configuration of the spectrum analyzer 1 shown in Figure 12, the signal to be measured as the input signal (RF Input) to port 27 of the ATT bank circuit 90 is, for example, a signal in the frequency range of 255 to 315 GHz (f RF The signal (IF Output) is attenuated and output from port 28, and further frequency-converted and output, for example, a signal in the frequency range of 23~31GHz (f IF ) In other words, the spectrum analyzer 1 according to this embodiment can take in a received signal received from, for example, 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), attenuate it by a predetermined amount in the ATT bank circuit 90, and then measure the spectral characteristics of a desired frequency component.

[0127] Next, the signal measurement and control operation of the spectrum analyzer 1 according to this embodiment will be explained with reference to the flowchart shown in Figure 13.

[0128] To perform signal measurement, the user, for example, sets the sweep frequency range (analysis target frequency range) of the spectrum analyzer 1 using the operation unit 160 (step S1). Examples of parameters set here include the center frequency, sweep frequency span, start frequency, and stop frequency.

[0129] Furthermore, the user performs an operation on the control unit 160 to set the signal attenuation amount in the ATT bank circuit 90 (step S2). Here, the attenuation amount is set in 1 dB increments, for example, within an attenuation range of 1 to 30 dB.

[0130] As a result of the above operation, the control unit 150 controls the variable attenuation control unit 151 to select an ATT corresponding to the attenuation amount set in step S2 by switching a switch or the like (step S3).

[0131] Subsequently, upon receiving the operation to start measurement, the control unit 150 inputs the signal to be measured to the ATT bank circuit 90, and the variable attenuation control unit 151 controls the signal to be measured to be attenuated by the ATT (waveguide attenuator 10) selected in step S3 above, and inputs it to the frequency conversion unit 100 (step S4).

[0132] Next, in the control unit 150, the frequency sweep control unit 152 performs frequency sweep control based on the sweep frequency range set in step S1, in accordance with the input of the attenuated signal under test to the frequency conversion unit 100, and converts the input signal under test into an IF signal (step S5), and inputs the IF signal to the detector 120.

[0133] Furthermore, the control unit 150 controls the detector 120 to extract the frequency components after frequency conversion by the frequency conversion unit 100 (step S6), and to perform a measurement of the spectral characteristics of the signal of those frequency components (step S7). Here, the spectrum data acquisition unit 153 acquires spectrum data including the intensity of the signal components in the desired frequency band (the analysis target frequency range set in step S1) detected by the detector 120, and performs spectrum display control to display the spectrum data on the display unit 161.

[0134] According to the spectrum analyzer 1 of this embodiment, each ATT (waveguide attenuator 10) used in the ATT bank circuit 90 has a structure in which the width of the resistive film 23 gradually differs in relation to its length. As a result, the attenuation amount for each frequency by these waveguide attenuators 10 can be made constant over a wide bandwidth, thereby improving the accuracy of the signal level in the spectrum analyzer 1.

[0135] (Manufacturing of waveguide attenuators) The waveguide attenuator 10 constituting the ATT bank circuit 90 can be manufactured, for example, by utilizing the signal measurement operation of the spectrum analyzer 1 shown in Figure 13 and repeating the signal measurement operation multiple times to produce one with the desired attenuation amount. The manufacturing operation of the waveguide attenuator 10 can be carried out during the signal measurement operation shown in Figure 13, for example, immediately following the measurement of the spectrum characteristics in step S7 (see step S10: waveguide attenuator manufacturing operation).

[0136] The manufacturing process for the waveguide attenuator 10 in step S10 will be explained with reference to the flowchart shown in Figure 14. This manufacturing process can be carried out, for example, by an externally connected PC (not shown) or by a manufacturing support control unit (not shown) provided as one of the control function units in the spectrum analyzer 1.

[0137] In carrying out the manufacturing work of the waveguide attenuator 10, it is assumed that the ATT (waveguide attenuator 10) that has been provisionally assembled according to the procedure described above is used in the ATT bank circuit 90.

[0138] As shown in Figure 14, during the manufacturing operation of the waveguide attenuator 10, the manufacturing support control unit measures the amount of attenuation of the signal (signal to be measured) by the waveguide attenuator 10 selected in step S4 of Figure 13 from among the ATTs (waveguide attenuators 10) that constitute the ATT bank circuit 90 during the signal measurement operation shown in Figure 13 (step S11).

[0139] Next, the manufacturing support control unit compares the measured attenuation amount with the attenuation amount set in step S2 of Figure 13 (step S12), and determines whether the difference between the two is within a preset tolerance range.

[0140] If it is determined that the above difference is within an acceptable range (step S13), the process is terminated. In this case, the resistive film substrate 22 currently attached to the inner wall portion 17a of the first waveguide portion 11a and the inner wall portion 17b of the second waveguide portion 11b is fixed in place, completing the waveguide attenuator 10.

[0141] If it is determined that the above difference exceeds the acceptable range (step S14), the resistive film substrates 22 attached to the inner wall portion 17a of the first waveguide section 11a and the inner wall portion 17b of the second waveguide section 11b are replaced with another resistive film substrate 22 that is likely to eliminate the above difference (step S15). After replacing the resistive film substrates 22, the process returns to step S1, for example, in Figure 13, and the signal measurement operation described above by the spectrum analyzer 1 is performed again.

[0142] From this point onward, the above replacement procedure is repeated as long as it is determined that the difference exceeds the acceptable range, and the signal measurement operation shown in Figure 13 is performed. During this time, if it is determined that the above difference is within the acceptable range, the resistive film substrate 22 that is currently installed is fixed, and the main assembly of the waveguide attenuator 10 is performed. By performing the above manufacturing procedure for all waveguide circuits 10 that constitute the ATT bank circuit 90, it is possible to manufacture individual waveguide attenuators 10 that can achieve their respective target attenuation amounts.

[0143] As described above, the waveguide attenuator control method according to this embodiment includes a setting step (S2, S22) of setting a target attenuation amount; a detection step (S11) of selecting a waveguide attenuator 10 corresponding to the target attenuation amount, inputting a signal, and detecting the signal attenuation amount; a determination step (S12) of determining whether the detected attenuation amount is within an acceptable range relative to the target value; and a replacement step (S15) of replacing the resistive film substrate 22 mounted on the inner wall surface 17a of the first waveguide section 11a and the inner wall surface 17b of the second waveguide section 11b with another resistive film substrate 22 until an attenuation amount within an acceptable range relative to the target value is detected.

[0144] This control method allows for the manufacture of a waveguide attenuator 10 that can stabilize the attenuation over a wide bandwidth while replacing the resistive film substrate 22, and makes it easy to achieve a constant attenuation even if there are variations in the dimensions of the resistive film substrate 22 (dielectric) or resistive film 23 during the manufacturing stage. Furthermore, when this waveguide attenuator 10 is applied to equipment that requires signal level adjustment, it is possible to improve the accuracy of the signal level.

[0145] (Signal analyzer) Figure 15 shows a general configuration of a signal analyzer 2 using the waveguide attenuator 10 according to this embodiment. The signal analyzer 2 includes a frequency conversion unit 100A, an analog-to-digital converter (ADC) 125, a control unit 150A, an operation unit 160, and a display unit 161, and is equipped with an ATT bank circuit 90A in front of the frequency conversion unit 100A.

[0146] The ATT bank circuit 90A is equivalent to the ATT bank circuit 90 applied to the spectrum analyzer 1 shown in Figure 12.

[0147] The frequency conversion unit 100A comprises a mixer 111A, a local signal generator 112A, and a filter 113A.

[0148] Mixer 111A converts the signal under test from RF frequency to intermediate frequency signal (IF frequency) by mixing the signals of each frequency component (RF frequency) attenuated by a predetermined amount output from ATT bank circuit 90A with the local signal input from local signal generator 112A, and outputs it.

[0149] The local signal generator 112A generates a local signal for transmission to the mixer 111A based on the local signal (reference signal) input from the local oscillator signal source 9.

[0150] Filter 113A is a filtering unit that receives the IF signal frequency-converted by mixer 111A, passes only the frequency components of a predetermined band of the input IF signal through, and inputs it to ADC 125.

[0151] The ADC125 is a functional unit that converts the signal (the signal under measurement), which has been attenuated by the ATT bank circuit (90A) and frequency converted by the frequency conversion unit (100A), from an analog signal to a digital signal.

[0152] The control unit 150A includes a variable attenuation control unit 151A, a frequency control unit 152A, and a signal analysis unit 153A. The variable attenuation control unit 151A is equivalent to the variable attenuation control unit 151 provided in the control unit 150 of the spectrum analyzer 1 (see Figure 12).

[0153] The frequency control unit 152A controls the setting of the local frequency so that it can receive signals within the specified analysis frequency range when the frequency conversion unit 100A converts the frequency of the signal under measurement. The local signal generator 112A, which is part of the frequency conversion unit 100A, has a configuration that allows the local frequency to be varied according to the received RF frequency. Therefore, the frequency control unit 152A may be configured to drive and control the local signal generator 112A and sweep the local frequency.

[0154] The signal analysis unit 153A performs a process to analyze the waveform of the signal (the signal under measurement) converted into a digital signal by the ADC 125, specifically, it performs a process to generate waveform analysis data for displaying the digital signal as a spectrum or other waveform.

[0155] The signal analysis process of the signal analyzer 2 having the above configuration proceeds in the same manner up to step S4 compared to the signal measurement operation of the spectrum analyzer 1 shown in Figure 12 (see Figure 13). In the subsequent signal analysis operation, the signal analyzer 2 inputs the signal under measurement, which has been attenuated by the ATT selected in step S4 of the ATT bank circuit 90A, from port 28 to the frequency conversion unit 100A for frequency conversion and inputs it to the ADC 125. The ADC 125 converts the frequency-converted signal from an analog signal to a digital signal and inputs it to the signal analysis unit 153A. The signal analysis unit 153A generates waveform analysis data from the digital signal input from the ADC 125 for displaying the digital signal as a spectrum or other waveform. The control unit 150A performs control for signal analysis, such as displaying the waveform analysis data generated by the signal analysis unit 153A on the display unit 161.

[0156] According to the signal analyzer 2 of this embodiment, each ATT (waveguide attenuator 10) used in the ATT bank circuit 90A has a structure in which the width of the resistive film 23 gradually differs in relation to its length. As a result, the attenuation amount for each frequency by these waveguide attenuators 10 can be made constant over a wide bandwidth, thereby improving the accuracy of the signal level in the signal analyzer 2.

[0157] (Signal generator) Figure 16 shows a general configuration of a signal generator 3 using a waveguide attenuator 10 according to this embodiment. The signal generator 3 is assumed to be a test signal generator that generates a test signal for performing a broadband signal reception sensitivity test on the DUT.

[0158] The signal generator 3 according to this embodiment includes a frequency conversion unit 100B, a signal generation unit 130, a control unit 150B, an operation unit 160, a display unit 161, and an ATT bank circuit 90B provided downstream of the frequency conversion unit 100B. The frequency conversion unit 100B is composed of a mixer 111B, a local signal generator 112B, and a filter 113B, and the control unit 150B is composed of an attenuation variable control unit 151B, a frequency control unit 152B, and a signal generation control unit 153B.

[0159] The ATT bank circuit 90B is equivalent to the ATT bank circuit 90 applied to spectrum analyzer 1 (see Figure 12) and the ATT bank circuit 90A applied to signal analyzer 2 (see Figure 15).

[0160] The frequency conversion unit 100B, under the control of the signal generation control unit 153B, feeds the intermediate frequency band test signal output from the signal generation unit 130, along with the local signal output from the local signal generator 112B, to the mixer 111B and converts it into a wideband signal. At that time, the frequency conversion unit 100B changes the frequency of the local signal according to the test target frequency set, for example, in the operation unit 160, in order to test the DUT, and sends the frequency-converted signal to the next stage.

[0161] The ATT bank circuit 90B is configured such that port 27 is connected to the output side of the frequency conversion unit 100A and port 28 is connected to the input side of the RF transmission unit. A signal converted to an RF frequency from the frequency conversion unit 100A (a test signal input from the signal generation unit 130) is input to port 27, and this input signal is attenuated by a preset amount and transmitted as a test signal which is the RF output.

[0162] The transmission control operation of the test signal of the signal generator 3 during DUT testing will be explained with reference to the flowchart shown in Figure 17.

[0163] To perform testing of the DUT, the user, for example, sets the frequency, i.e., the test frequency, on the control unit 160 (step S21). Examples of parameters set here include the center frequency, start frequency, and stop frequency.

[0164] Furthermore, the user can set the signal attenuation amount in the ATT bank circuit 90B by operating the control unit 160 (step S22).

[0165] As a result of the above operation, the control unit 150B controls the variable attenuation control unit 151B to select an ATT corresponding to the attenuation amount set in step S2 by switching a switch or the like (step S23).

[0166] Subsequently, upon receiving the operation to start measurement, the control unit 150B converts the frequency of the signal generated by the signal generation unit 130 using the frequency conversion unit 100B, and inputs the frequency-converted signal to the ATT bank circuit 90B from port 27 (step S24).

[0167] Accordingly, the variable attenuation control unit 151B controls the ATT bank circuit 90B, attenuating the signal under measurement using the ATT (waveguide attenuator 10) selected in step S23, and outputting it from port 28 to an RF transmission unit (not shown) (step S25).

[0168] Furthermore, the control unit 150B drives and controls the RF transmission unit, and sends out the frequency component signal input from port 28 of the ATT bank circuit 90B as a test signal (step S26).

[0169] Even when controlling the transmission of the test signal of the signal generator 3 described above, it is possible to manufacture the ATT (waveguide attenuator) to be used in the ATT bank circuit 90B by following the same procedure (see Figure 14) as the waveguide attenuator manufacturing operation (step S10) performed using the signal measurement operation of the spectrum analyzer 1 shown in Figure 13. However, it goes without saying that the waveguide attenuator manufacturing operation is not limited to being carried out by mounting it on equipment such as the spectrum analyzer 1 or the signal generator 3, but can be done in various ways, such as connecting a PC and checking the amount of attenuation while replacing the resistive film substrate 22 until the target amount of attenuation is obtained.

[0170] According to the signal generator 3 of this embodiment, each ATT (waveguide attenuator 10) used in the ATT bank circuit 90B has a structure in which the width of the resistive film 23 gradually differs in relation to its length. As a result, the attenuation amount for each frequency by these waveguide attenuators 10 can be made constant over a wide bandwidth, thereby improving the accuracy of the signal level in the signal generator 3. [Industrial applicability]

[0171] As described above, the present invention has the effect of being able to keep the attenuation constant over a wide bandwidth and improving the accuracy of the signal level even when applied to equipment that requires adjustment of the signal level. It is useful in general for waveguide attenuators that adjust the attenuation by providing a resistive film inside the waveguide, spectrum analyzers, signal analyzers, signal generators, and waveguide filter control methods that use the same. [Explanation of symbols]

[0172] 1. Spectrum analyzer 2. Signal Analyzer 3. Signal Generator 9. Local oscillator signal source 10 Waveguide Attenuator 11a First waveguide section 11b Second waveguide section 12a Front side of the first waveguide section 12b Front side view of the second waveguide section 13, 14 aperture 15 Waveguides 15a, 15b Groove 16a, 18a Inner wall surface of groove 15a 16b, 18b Inner wall surface of groove 15b 17a Inner wall surface of groove 15a (one of the pair of short-side inner wall surfaces of the waveguide) 17b Inner wall surface of groove 15b (the other of the pair of short-side inner wall surfaces of the waveguide) 19a, 19b Mounting holes for circuit board 22, 22a, 22b, 22c, 22d Resistive film substrate (substrate) 23, 23a, 23b, 23b1, 23c, 23c1, 23d Resistive film 90, 90A, 90B ATT bank circuits (waveguide attenuators) 100, 100A, 100B frequency conversion section 111, 111A, 111B Mixer 112, 112A, 112B Local Signal Generators 113, 113A, 113B filters 120 Detector 125 Analog-to-Digital Converter (ADC) 130 Signal generation unit 150, 150A, 150B control unit 151, 151A, 151B Variable Attenuation Control Unit 152 Frequency sweep control unit 152A, 152B Frequency Control Unit 153 Spectrum data acquisition unit 153A Signal analysis section 153B Signal Generation Control Unit 160 Operation section 161 Display section

Claims

1. A waveguide attenuator comprising a rectangular waveguide in which a waveguide (15) with a rectangular cross-section is formed, wherein a resistive film (23) is provided on the inner wall surface (17a, 17b) of the waveguide along the propagation direction (Y direction) of the radio waves in the waveguide attenuates the radio waves propagating in the waveguide, Waveguide attenuator characterized in that the resistive film has a structure in which the dimension in the direction perpendicular to the propagation direction of radio waves in the waveguide (Z direction) (defined as "width") gradually differs from the dimension in the direction parallel to the propagation direction of radio waves in the waveguide (Y direction) (defined as "length").

2. The inner wall surface of the waveguide is a pair of opposing inner wall surfaces. The waveguide attenuator according to claim 1, characterized in that the resistive film is provided on either one or both of the pair of opposing inner wall surfaces of the waveguide.

3. The rectangular waveguide is divided into two parts along its longitudinal direction, and consists of a first waveguide section (11a) having an inner wall surface (17a) corresponding to one of the pair of inner wall surfaces and a groove 15a corresponding to half of the waveguide, and a second waveguide section (11b) having an inner wall surface (17b) corresponding to the other of the pair of inner wall surfaces and a groove 15b corresponding to the remaining half of the waveguide, and can be joined facing each other so that the waveguide is formed by the groove 15a and the groove 15b. The resistive film is provided on a resistive film substrate (22) made of a dielectric material. The waveguide attenuator according to claim 2, characterized in that the resistive film substrate is configured to be detachably attached to the inner wall surface of the first waveguide section and the inner wall surface of the second waveguide section, respectively, while the resistive film is provided on it.

4. The resistive film substrate is composed of a plurality of substrates (22a, 22b, 22c, 22d), and a plurality of resistive films (23a, 23b, 23c, 23d) are provided on each of the plurality of substrates. The waveguide attenuator according to claim 3, characterized in that a structure is formed in which the width of the resistive film gradually differs by mounting the plurality of substrates in a row.

5. The resistive film substrate is composed of a single substrate, The waveguide attenuator according to claim 3, characterized in that a plurality of the resistive films are provided on the single substrate in a form in which the widths gradually differ.

6. The waveguide attenuator according to claim 4 or 5, characterized in that the resistive film has two different widths.

7. The waveguide attenuator according to claim 4 or 5, characterized in that the resistive film has a structure in which the width changes continuously.

8. A spectrum analyzer (1) has a frequency conversion unit (100) that attenuates a signal to be measured in a predetermined frequency range to a predetermined level using a waveguide attenuator (90), and feeds the attenuated signal to be measured together with a local signal output from a local signal generator (112) to a mixer (111), and a filter (113) that extracts a signal in a predetermined intermediate frequency band from the mixing output, and a detector (120) that detects the signal in the intermediate frequency band, and changes the frequency of the local signal according to the frequency to be analyzed to determine the spectral characteristics of the signal to be measured, A spectrum analyzer characterized in that the waveguide attenuator used is the waveguide attenuator described in any one of claims 1 to 5.

9. A signal analyzer (2) has a frequency conversion unit (100A) that attenuates a signal to be measured in a predetermined frequency range to a predetermined level using a waveguide attenuator (90A), and feeds the attenuated signal to be measured together with a local signal output from a local signal generator (112A) to a mixer (111A), and a filter (113A) that extracts a signal in a predetermined intermediate frequency band from the mixing output; and a signal analysis unit (153A) that converts the signal in the intermediate frequency band into a digital signal using an ADC (125) and then analyzes the waveform of the signal, and analyzes the waveform of the signal to be measured by changing the frequency of the local signal according to the frequency to be analyzed, A signal analyzer characterized in that the waveguide attenuator is the waveguide attenuator described in any one of claims 1 to 5.

10. A signal generator (3) includes a frequency conversion unit (100B) that receives a test signal in the intermediate frequency band output from a signal generation unit (130) together with a local signal output from a local signal generator (112B) and converts it into a signal in a predetermined frequency range, and a waveguide attenuator (90B) that attenuates the frequency-converted signal to a predetermined level, wherein the frequency of the local signal is changed according to the test frequency for testing the object under test (DUT), and the frequency-converted signal from the frequency conversion unit is attenuated by the waveguide attenuator before being sent out as the test signal for the object under test, A signal generating device characterized in that the waveguide attenuator is the waveguide attenuator described in any one of claims 1 to 5.

11. A method for controlling a waveguide attenuator in a spectrum analyzer, signal analyzer, or signal generator using a waveguide attenuator (10) according to any one of claims 3 to 5, Setting steps (S2, S22) to set the target attenuation amount, A detection step (S11) involves selecting the waveguide attenuator corresponding to the target attenuation amount, inputting a signal, and detecting the attenuation amount of the signal. A determination step (S12) to determine whether the detected attenuation amount is within the allowable range relative to the target value, Until an attenuation amount within the allowable range relative to the target value is detected, the resistive film substrates attached to the inner wall surfaces of the first waveguide section and the inner wall surfaces of the second waveguide section are replaced with other resistive film substrates in a replacement step (S15), A method for controlling a waveguide attenuator, characterized by including the following:

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