Receiving device and signal processing method

Abstract

To provide a receiving device that enables visual discrimination between spurious and desired wave components regardless of the width of the band of a received signal.SOLUTION: A receiving device includes a receiver for receiving a radio signal, and a signal processor. The receiver includes a preselector, a frequency converter, and an A / D converter. The preselector limits the band of the received radio signal. The frequency converter mixes the output of the preselector with a local signal to obtain an intermediate frequency signal. The A / D converter generates digital data of the intermediate frequency signal. The signal processor includes an image generator, a calculator, and a spurious manifestation processor. The image generator generates a spectrum image of the radio signal from the digital data. The calculator calculates a spurious generation band from the frequency of the radio signal and the frequency of the local signal. The spurious manifestation processor manifests the spuriousness in the spectrum image.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] An embodiment of the present invention relates to a receiving apparatus and a signal processing method. [Background technology]

[0002] Spurious emissions are particularly problematic in receivers that handle wide-band, high-frequency signals. In many receivers, the received signal is mixed with a local oscillator signal and down-converted to an intermediate frequency band. In this case, if the band of the received signal is too wide, it becomes difficult to separate the desired wave component from the spurious emissions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-45227 A Summary of the Invention [Problem to be solved by the invention]

[0004] In existing receivers, a preselector is installed in front of the mixer to suppress spurious signals by limiting the band of the signal before frequency conversion. With this configuration, it is difficult to remove spurious signals if the band of the received signal is too wide. For this reason, there is no choice but to rely on the mixer's ability to remove spurious signals, but in any case, no fundamental solution has been taken at present.

[0005] SUMMARY OF THE DISCLOSURE An object of the present invention is to provide a receiving device and a signal processing method that enable visual distinction between spurious and desired wave components regardless of the width of the band of the received signal. [Means for solving the problem]

[0006] According to an embodiment, a receiving device includes a receiver that receives a radio signal and converts it into digital data, and a signal processing unit that processes the digital data. The receiver includes a preselector, a frequency conversion unit, and an analog / digital converter. The preselector limits the band of the received radio signal. The frequency conversion unit mixes an output of the preselector with a local signal to obtain an intermediate frequency signal. The analog / digital converter digitally converts the intermediate frequency signal to generate digital data. The signal processing unit includes an image generation unit, a calculation unit, and a spurious manifestation processing unit. The image generation unit generates a spectrum image of the radio signal from the digital data. The calculation unit calculates the spurious occurrence band from the frequency of the radio signal and the frequency of the local signal. The spurious manifestation processing unit manifests the spurious in the spectrum image. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a system diagram showing an example of a wideband receiving device. [Diagram 2] FIG. 2 is a table showing frequency components output from mixer 13 of FIG. [Diagram 3] FIG. 3 is a diagram for explaining how the preselector can remove harmonic components. [Figure 4] FIG. 4 is a diagram for explaining why the preselector cannot remove the harmonic components. [Diagram 5] FIG. 5 is a block diagram showing an example of a receiving device according to the first embodiment. [Figure 6] FIG. 6 is a functional block diagram showing an example of the signal processing unit 21 shown in FIG. [Figure 7] FIG. 7 is a diagram showing an example of a spectrum image displayed on the display 22. As shown in FIG. [Figure 8] FIG. 8 is a block diagram showing an example of a receiving device according to the second embodiment. [Figure 9] FIG. 9 is a functional block diagram showing an example of the processor 23 of the signal processing unit 21 shown in FIG. [Figure 10]FIG. 10 is a diagram showing another example of the spectrum image displayed on the display 22. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment will be described with reference to the drawings. First, the relationship between the reception band and spurious emissions will be described. FIG. 1 is a system diagram showing an example of a wideband receiving device. In FIG. 1, a radio signal (frequency f RF ) is amplified by a low-noise amplifier 11, has its band limited by a preselector 12, and is converted into a local signal (frequency f LO ) in the mixer 13. The intermediate frequency signal (frequency f IF ) is subjected to anti-aliasing filter 15 to remove aliases, and then input to analog / digital (A / D) converter 16 where it is converted into a received data signal.

[0009] Incidentally, spurious signals are generated by intermodulation occurring in nonlinear circuits such as the mixer 13. In the system of Fig. 1, if we assume that the input and output have the same nonlinearity as the mixer 13, and express the input as x(t) and the output as y(t), the output of the system can be approximated as a polynomial of t, as shown in equation (1).

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[0010] The signal of formula (2) is input to the system of Figure 1. Formula (2) expresses the difference between the frequencies (f 1 and f 2 ) represents two sine waves.

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[0011] x(t) in equation (1) is x in equation (2) 1 (t), x 2 (t), substituting equation (2) into equation (1) gives equation (3).

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[0012] By expanding equation (3), we obtain equation (4).

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[0013] Applying equation (4) to the mixer 13 in Figure 1, f 1 is the frequency of the radio signal RF and f 2 f LO The output frequency (f RF -f LO ) is f IF As shown in the table in Figure 2, the other frequencies are spurious components due to intermodulation. XX is defined as a coefficient, which has a different value for each frequency.

[0014] As shown in FIG. 3, the reception band f BW F RF If the reception frequency is within a narrow band above or below f, it is easy for the preselector 12 to suppress the intermodulation components (harmonic waves). However, as shown in FIG. BW F RF When the frequency is as wide as 2×f RF ) is included in the passband of the preselector 12, it is not possible to remove the intermodulation components (harmonic waves) from the output of the mixer 13. In this way, in a wideband receiving device, the preselector cannot remove the harmonic wave components, and intermodulation components occur within the processing band, making it difficult to meet the spurious requirements. Next, a first embodiment and a second embodiment will be described.

[0015] <First embodiment> Fig. 5 is a block diagram showing an example of a receiving device according to the first embodiment. In Fig. 5, the receiving device includes a receiver 10 having an antenna 1, and a display device 20. The receiver 10 receives a radio signal arriving at the antenna 1 and converts it into digital data using functional blocks similar to those of the wideband receiving device (Fig. 1). The display device 20 includes a signal processing unit 21 that processes the digital data, and a display 22 connected to the signal processing unit 21.

[0016] Fig. 6 is a functional block diagram showing an example of the signal processing unit 21 shown in Fig. 5. The signal processing unit 21 is a computer including a processor 23 and a storage unit 24. The storage unit 24 stores a program 24a for causing the computer to function as the signal processing unit 21, received signal data 24b sent from the receiver 10 (Fig. 5), and spectrum image data 24c. The signal processing unit 21 also includes a ROM 25, a RAM 26, and a communication unit 27.

[0017] The processor 23 includes an image generating unit 23a, a calculating unit 23b, and a spurious manifestation processing unit 23c as processing functions according to the embodiment.

[0018] The image generator 23a performs a fast Fourier transform (FFT) on the received signal data 24b (digital data) to generate spectrum data. The image generator 23a then generates a spectrum image of the wireless signal received by the antenna 1 from the spectrum data.

[0019] The calculation unit 23b detects the frequency of the signal component and calculates the frequency of the radio signal and the frequency of the local signal from the local oscillator 14 (f LO ) and calculate the spurious generation band (frequency) using, for example, equation (4).

[0020] The spurious emission specification processing unit 23c specifies the spurious emission calculated by the calculation unit 23b in the spectrum image generated by the image generation unit 23a.

[0021] 7 is a diagram showing an example of a spectrum image displayed on the display 22. The spectrum image shows the amplitude versus frequency of a radio signal in a graph with the horizontal axis representing frequency and the vertical axis representing amplitude, and typically the strongest peak represents the peak (a) of the desired wave component. Additionally, in the embodiment, in the spectrum image, the band (b) of the spurious component is displayed, for example, in a color different from other bands. That is, the spurious manifestation processing unit 23c makes the color of the band in which the spurious occurs different from the other bands. Alternatively, the spurious band may be manifested by displaying a marker (c).

[0022] As described above, in the first embodiment, the frequency f of the local signal, which is known, is LO The frequency at which spurious components appear is calculated from the frequency of the radio signal to be received, and the spurious band is clearly distinguished and displayed in the spectrum image. This allows the user to recognize at a glance that spurious components are occurring, eliminating the risk of misinterpreting the observation results.

[0023] That is, in the embodiment, spurious signals are not directly removed, but are clearly distinguished from desired wave components, thereby preventing a user from misinterpreting the spurious signals and the desired wave. As a result, according to the first embodiment, spurious signals can be visually distinguished from desired wave components regardless of the width of the band of the received signal, and thus it is possible to prevent misinterpretation of the observation results.

[0024] <Second embodiment> Fig. 8 is a block diagram showing an example of a receiving device according to the second embodiment. In Fig. 5, the receiving device includes a receiver 10 and a receiver 30, each of which includes an antenna 1. The receiver 10 generates received signal data (first digital data) of a wireless signal through a system similar to that shown in Figs. 1 and 5, and sends the data to a signal processing unit 21 of a display device 20.

[0025] Similarly, the receiver 30 generates received signal data (second digital data) of the wireless signal by the A / D converter 16 and sends it to the signal processing unit 21 of the display device 20. However, the receiver 30 has a variable attenuator 31 in the stage preceding the preselector 12. The variable attenuator 31 attenuates the wireless signal received by the antenna 1 by a settable amount of attenuation. The subsequent preselector 12 limits the bandwidth of the output of the variable attenuator 31.

[0026] Fig. 9 is a functional block diagram showing an example of the processor 23 of the signal processing unit 21 shown in Fig. 8. The processor 23 includes, as its processing functions, an image generating unit 23a, a spurious manifestation processing unit 23c, and an identifying unit 23d.

[0027] The image generating unit 23a performs FFT processing on the received signal data (first digital data) of the received signal that has not passed through the variable attenuator 31 and the received signal data (second digital data) of the received signal that has passed through the variable attenuator 31, to generate spectrum data. Then, the image generating unit 23a generates spectrum images of the wireless signals received by the receivers 10 and 30 from the respective spectrum data.

[0028] The identifying unit 23d compares the difference between the peak based on the first digital data and the peak based on the second digital data in the spectrum data with the attenuation set in the variable attenuator 31 to identify the spurious generated in the spectrum data.

[0029] The spurious emission specifying processor 23c specifies the spurious emission identified by the specifier 23d in the spectrum image generated by the image generator 23a.

[0030] Fig. 10 is a diagram showing another example of a spectrum image displayed on display 22. In Fig. 10, the solid line indicates the spectrum waveform from receiver 10, and the dotted line indicates the spectrum waveform from receiver 30. A level difference occurs between the two waveforms due to the attenuation set in variable attenuator 31 of receiver 30. In Fig. 10, the level difference at the maximum peak is ΔA1, the level difference at the next peak is ΔA2, and the level difference at the peak after that is ΔA3.

[0031] Then, the identification unit 23d compares ΔA1 to ΔA3 with the attenuation set in the variable attenuator 31, determines that the peaks showing the same attenuation as the set attenuation are original signal components (desired wave components), and identifies the other peaks as spurious.

[0032] Referring to equation (4), the cross modulation coefficient is f IF Therefore, a peak that shows the same attenuation as the set attenuation of the variable attenuator 31 can be regarded as the original received signal. On the other hand, a peak that shows an attenuation different from the set attenuation of the variable attenuator 31 can be regarded as a spurious component.

[0033] The identification result by the identification unit 23d is passed to the spurious emission indication processing unit 23c. Then, the spurious emission indication processing unit 23c indicates the identified spurious emission in the spectrum image of Fig. 10. In Fig. 10, the marker (c) indicates that the spurious emission is present.

[0034] As described above, in this embodiment, multiple receivers are provided, and at least one of the receivers is provided with a variable attenuator to attenuate the received signal of that system.The spectrum of the attenuated received signal is compared with the spectrum of the unattenuated received signal, and a peak showing attenuation corresponding to the set attenuation amount is identified as a desired wave component.In addition, a peak showing an attenuation amount not corresponding to the set attenuation amount is identified as a spurious component.

[0035] In this way, the spurious components can be reliably identified and clearly indicated in the spectrum image. Therefore, according to the second embodiment, it is also possible to visually distinguish between the spurious and the desired wave components regardless of the width of the band of the received signal, and it is possible to prevent misinterpretation of the observation results.

[0036] Although some embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0037] 1...antenna, 10...receiver, 11...low noise amplifier, 12...preselector, 13...mixer, 14...local oscillator, 15...anti-aliasing filter, 16...analog / digital converter, 20...display device, 21...signal processing unit, 22...display device, 23...processor, 23a...image generation unit, 23b...calculation unit, 23c...spurious explicit processing unit, 23d...identification unit, 24...memory unit, 24a...program, 24b...received signal data, 24c...spectrum image data, 25...ROM, 26...RAM, 27...communication unit, 30...receiver, 31...variable attenuator.

Claims

1. A receiver that receives the radio signal and converts it into digital data; a signal processing unit for processing the digital data, The receiver includes: a preselector for limiting a band of the received radio signal; a frequency conversion unit that mixes an output of the preselector with a local signal to obtain an intermediate frequency signal; an analog / digital converter that digitally converts the intermediate frequency signal to generate the digital data; The signal processing unit includes: an image generating unit that generates a spectrum image of the radio signal from the digital data; a calculation unit that calculates a spurious generation band from a frequency of the radio signal and a frequency of the local signal; a spurious manifestation processing unit that manifests the spurious in the spectrum image.

2. a first receiver for receiving and converting a wireless signal into first digital data; a second receiver for receiving the wireless signal and converting it into second digital data; a signal processing unit that processes the first digital data and the second digital data, The first receiver comprises: a preselector for limiting a band of the received radio signal; a frequency conversion unit that mixes an output of the preselector with a local signal to obtain an intermediate frequency signal; an analog / digital converter that digitally converts the intermediate frequency signal to generate the first digital data; The second receiver comprises: a variable attenuator for attenuating the received radio signal by a settable amount of attenuation; a preselector for limiting the bandwidth of the output of the variable attenuator; a frequency conversion unit that mixes an output of the preselector with a local signal to obtain an intermediate frequency signal; an analog / digital converter that digitally converts the intermediate frequency signal to generate the second digital data; The signal processing unit includes: an image generating unit that generates a spectrum image of the radio signal from the first digital data and the second digital data; an identifying unit that identifies a spurious component by comparing a difference between a peak based on the first digital data and a peak based on the second digital data with a set attenuation amount; a spurious manifestation processing unit that manifests the spurious in the spectrum image.

3. 3. The receiving device according to claim 1, wherein the spurious emission revealing processor differentiates a color of the band in which the spurious emission occurs from other bands.

4. 3. The receiving device according to claim 1, wherein the spurious emission specifying processing unit indicates the spurious emission by attaching a marker to the spurious emission.

5. A signal processing method by a processor that processes digital data obtained by digitally converting an intermediate frequency signal generated by mixing a radio signal with a local signal, comprising the steps of: generating a spectrum image of the wireless signal from the digital data; a step of the processor calculating a spurious generation band from a frequency of the radio signal and a frequency of the local signal; the processor manifesting the spurs in the spectrum image; and displaying, by the processor, a spectrum image showing the spurious components on a display.

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