JP2013098854A - Reception system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To receive signals with low noise with reduced influence of interference signals.SOLUTION: A reception system includes: a local oscillation signal generation unit for generating a frequency swept local oscillation signal; a first frequency conversion unit for converting the frequency of a radio signal and outputting the signal, by multiplying an inputted radio signal and a local oscillation signal; and a signal processing unit for detecting a signal contained in the radio signal and separating the detected signal, based on the frequency transition speed of a signal in frequency domain, obtained by converting the frequency converted radio signal to a frequency domain signal, and the frequency sweeping speed of the local oscillation signal.

Description

  The present invention relates to a receiving system for receiving a radio signal.

  In recent years, with the development of wireless communication systems such as mobile phones and wireless LANs, frequency demand has increased. In particular, in the frequency band of several GHz band, frequencies are densely allocated, and it is difficult to secure a new frequency band. For this reason, it has been studied to increase the frequency utilization efficiency by using “spatial” and “temporal” among the already assigned frequencies.

  For this realization, a cognitive radio system that is used as communication after grasping an available frequency band that changes depending on the use situation, software radio technology that can flexibly cope with various radio standards, and the like are expected. A required wireless receiver for sensing is required to be able to receive a signal with a low reception level with high accuracy and to detect the absence of another system.

  A conventional wireless receiver uses a bandpass filter before and after the low noise amplifier to remove interference signals outside the desired band. As a band-pass filter of a wireless device in the microwave band, a SAW (SURFACE ACOUSTIC WAVE) filter, a boundary acoustic wave filter, a dielectric filter, and the like are used. SAW filters and boundary acoustic wave filters are used as built-in filters in recent mobile phones because they have a large amount of suppression of signals outside the desired band, and can be mass-produced at a small size and low cost (Non-patent Document 1). Dielectric filters are used in base station receivers that handle relatively broadband wireless signals.

  As a conventional wireless receiver, a direct conversion type receiver that requires a small number of circuit components is used in a portable terminal that receives only one channel (Non-patent Document 2). In a system that receives multiple channels simultaneously, a heterodyne or superheterodyne receiver may be used. In heterodyne and superheterodyne receivers, if there is an interference signal in the image band, it becomes difficult to determine and demodulate the power of the desired signal. Therefore, a frequency converter such as a SAW filter or an image suppression mixer is used to remove the interference signal in the image band. (Non-patent Document 3).

However, in a cognitive radio system or software defined radio that supports various frequencies, it is not desirable to use a bandpass filter in the RF band because the frequency band that can be received is limited. A frequency variable band pass filter or the like has been studied. However, there is a problem that a variable range is generally narrow and an insertion loss is larger than a fixed frequency filter. In particular, if the insertion loss of a bandpass filter arranged in front of the low noise amplifier is large, the noise figure of the receiver increases, and a weak signal may not be received and demodulated.
Further, when a band-pass filter is not used, the frequency converter of the radio receiver has a problem that interference signals in the harmonic band interfere with each other because the receiver has sensitivity in a band that is an integral multiple of the local oscillator signal. As a solution to this problem, a method using an FIR filter that makes the frequency that becomes the null point variable has been proposed (Non-Patent Document 4).

Kei Nezu, “Filter using“ Boundary Elastic Wave ”Developed by Murata Manufacturing Co., Ltd.”, Nikkei Electronics, Nikkei BP, May 7, 2007, pp. 12-13 Yoshida, Kato, Tomizawa, Odaka, Tsurumi, "Configuration and Prototype Evaluation of Software Defined Radio Reception System Using Direct Conversion and Low-IF System", IEICE Transactions 2001/7 vol. J84-B, no. 7, 2001. Tsunehara Tsuneo, "Introduction to CMOS RF Circuit Design-2nd-", Nikkei Electronics, Nikkei BP, January 28, 2008, pp. 164-174 Rahim Bagheri, Ahmad Mirzaei, Saeed Chehrazi, Mohammad E. Heidari, Minjae Lee, Mohyee Mikhemar, Wai Tang, and Asad A. Abidi, An 800-MHz-6-GHz Software-Defined WirelessReceiver in 90-nm CMOS, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 41, NO. 12, pp. 2860-2876, DECEMBER 2006.

  However, when the technique described in Non-Patent Document 4 is used, there is a problem that an increase in the circuit scale is caused if the variable range of the frequency that becomes the null point is widened. As described above, there are various problems in receiving a broadband wireless signal with low noise and high sensitivity.

  The present invention has been made in view of such circumstances, and in a cognitive radio system or software defined radio corresponding to various frequencies, a reception system capable of performing reception with low noise and reduced influence of an interference signal. Is to provide.

  In order to solve the above problem, the present invention provides a local oscillation signal generation unit that generates a local oscillation signal that is swept in frequency, and frequency-converts the radio signal by multiplying the local oscillation signal by the input radio signal. Output the frequency conversion unit, convert the frequency-converted radio signal into a frequency domain signal, sweep the frequency of the signal in the frequency domain obtained by the conversion, and the frequency of the local oscillation signal And a signal processing unit that detects a signal included in the wireless signal based on the speed and separates the detected signal.

  In the invention described above, the signal processing unit may calculate, for each signal in the frequency domain, the frequency of the signal, the speed at which the signal transitions, and the frequency of the local oscillation signal. The frequency of the radio signal corresponding to the signal is calculated from the sweeping speed.

  In addition, the present invention provides the signal processing unit according to the above-described invention, wherein the signal processing unit further includes a frequency of the signal in the frequency domain when the local oscillation signal generation unit performs a sweep to increase the frequency of the local oscillation signal. Is increased, the radio signal corresponding to the detected signal is determined to be a lower sideband signal of the local oscillation signal, and the local oscillation signal generation unit performs a sweep to increase the frequency of the local oscillation signal When the frequency of the signal in the frequency domain decreases, it is determined that the radio signal corresponding to the detected signal is an upper-band signal of the local oscillation signal, and the local oscillation signal generator generates the local oscillation When the frequency of the signal in the frequency domain decreases when sweeping to reduce the frequency of the signal, the radio signal relative to the detected signal is the local oscillation If the frequency of the signal in the frequency domain increases when the local oscillation signal generator sweeps to reduce the frequency of the local oscillation signal, the detection is performed. It is determined that the radio signal corresponding to the received signal is a signal in the upper side band of the local oscillation signal.

  Further, the present invention is the above-described invention, wherein the signal processing unit further changes the frequency at a speed that is an integral multiple of the speed at which the frequency of the local oscillation signal is swept among the signals in the frequency domain. When there are a plurality of signals to be processed and the frequency of the signals becomes 0 [Hz] at the same time, it is determined that the signal is a harmonic generated in the own system.

  Moreover, the present invention is characterized in that, in the above-described invention, the signal processing unit reduces the gain in the frequency conversion unit when it is determined that a harmonic is generated in its own system.

  Further, the present invention is the above-described invention, wherein the signal processing unit multiplies the local oscillation signal in a frequency band with a small phase noise out of the frequency band in which the local oscillation signal is swept, and the frequency converted signal A signal included in the wireless signal is detected by using.

  In the present invention, the signal processing unit may further use the frequency of the local oscillation signal and information indicating the initial phase of the carrier wave of the radio signal to detect the detected signal. It is characterized by demodulating.

  Further, the present invention is the above-described invention, wherein the signal processing unit is configured to use frequency information indicating a use application, a radio power standard, a radio modulation scheme, and a position used in the use application for each frequency band in the radio signal. A signal included in the wireless signal is detected by using.

  In the invention described above, the signal processing unit may include a desired signal included in a target frequency band for detecting a signal in the radio signal, a signal included in a frequency band other than the target frequency band, and the An interference signal which is a signal in an image band of a desired signal is detected, and the frequency band of the local oscillation signal in which the frequency of the interference signal frequency-converted in the frequency converter does not match the frequency of the desired signal is The frequency of the local oscillation signal is selected as a frequency band to be swept, and the local oscillation signal generator is controlled to sweep the local oscillation signal in the selected frequency band.

  Further, the present invention is the above-described invention, wherein the signal processing unit generates a frequency conversion signal whose frequency is swept at a speed corresponding to a change speed of the frequency of the detected signal, and the frequency conversion signal A signal is multiplied by the frequency-converted radio signal, and a signal included in the radio signal is detected based on the signal obtained by the multiplication.

  Further, according to the present invention, in the above-described invention, a frequency conversion signal generation unit that generates a frequency conversion signal whose frequency is swept at a speed corresponding to a frequency change speed of the local oscillation signal, and the frequency conversion And a second frequency converter that multiplies the frequency-converted radio signal by the frequency-converted radio signal and outputs the signal obtained by the multiplication, and the signal processor is output by the second frequency converter. A signal included in the wireless signal is detected based on a signal to be transmitted.

  Further, the present invention is characterized in that, in the above-described invention, the second frequency conversion unit performs multiplication on an analog signal.

  Further, the present invention is characterized in that, in the above-described invention, the signal processing unit controls a speed of changing the frequency of the local oscillation signal based on the detected signal.

According to the present invention, a signal contained in a predetermined radio signal can be detected from the speed at which the frequency of the local oscillation signal is swept and the speed at which the frequency of the signal obtained by frequency conversion of the radio signal changes. . At this time, the frequency in the radio signal with respect to the detected signal can be calculated from the frequency of the local oscillation signal and the speed at which the frequency is swept, and the speed at which the frequency of the signal obtained by frequency conversion of the radio signal changes. It can be determined whether or not a radio signal is present in a predetermined frequency range.
In this way, it is possible to determine whether or not a signal exists in a predetermined frequency range without performing filtering processing on the radio signal, thereby causing loss in filtering processing and an increase in noise figure. Therefore, low noise reception processing can be performed. In addition, since it can be determined whether the detected signal is a signal in a predetermined frequency range or an interference signal outside the predetermined frequency range, the interference signal is detected and separated from the radio signal, and the influence of the interference signal can be determined. Reduced reception processing can be performed.

It is a schematic block diagram which shows the structure of the receiver 100 in 1st Embodiment. It is a schematic block diagram which shows the structural example of the signal processing part 170 in the embodiment. It is a figure which shows an example of the signal of the radio frequency band in this embodiment, a local oscillation signal, and the signal of IF band. It is a figure which shows the other example of the signal of the radio frequency band in this embodiment, a local oscillation signal, and the signal of IF band. It is a flowchart of the determination process which detects the desired signal and interference signal which the signal processing part 170 in this embodiment performs. 4 is a diagram illustrating an example of unnecessary waves generated in the receiver 100. FIG. It is a figure which shows the outline | summary of the harmonic detection method in this embodiment. It is the schematic which shows the case where a harmonic influences with respect to a desired signal. FIG. 10 is a schematic block diagram illustrating a configuration of a reception system 200 as a modification example of the receiver 100. It is a figure which shows an example of the local oscillation signal and the sweep speed (slope) of its harmonic. FIG. 10 is a schematic block diagram illustrating a first modification of the configuration of the signal processing unit 170. It is a graph which shows the frequency change of IF signal at the time of multiplying the digital signal of time series data by using the detected desired signal as a signal for frequency conversion. 12 is a schematic block diagram illustrating a second modification of the configuration of the signal processing unit 170. FIG. 10 is a schematic block diagram illustrating a configuration of a modified example of the receiver 100. FIG.

  Hereinafter, an overview of a receiver (reception system) according to an embodiment of the present invention will be described with reference to the drawings. The receiver in the following embodiment frequency-converts a radio frequency band into an intermediate frequency (IF) band (or baseband frequency band) signal. At this time, the frequency is converted into an IF band signal using a local oscillation signal having a certain sweep speed (frequency change speed). The IF band signal is separated into a desired signal and an interference signal in the image band and the harmonic band based on the difference in sweep speed (frequency change speed), and the desired signal is extracted. Here, sweeping means changing the frequency of a local oscillation signal used for frequency conversion from a certain frequency to a different frequency in a predetermined step.

(First embodiment)
FIG. 1 is a schematic block diagram illustrating a configuration of a receiver 100 according to the first embodiment. As shown in the figure, a receiver 100 as a receiving system includes a wideband LNA (Low Noise Amplifier) 110, a local oscillation signal generator 120, a frequency converter 130, a frequency band limiter 140, and a gain. An adjustment unit 150, an analog-digital conversion unit (ADC) 160, and a signal processing unit 170 are provided.

The broadband LNA 110 amplifies an RF (Radio Frequency) signal received via the antenna, and outputs the amplified RF signal to the frequency conversion unit 130.
The local oscillation signal generation unit 120 includes a local oscillator 121 that generates a local oscillation signal (LO ₁ ) having a certain frequency. The local oscillation signal generation unit 120 outputs the local oscillation signal generated by the local oscillator 121 to the frequency conversion unit 130. The local oscillator 121 can be used by sweeping the oscillation frequency at a predetermined constant speed. The sweep rate of the local oscillator signal LO ₁ and Vosc1.

  The frequency conversion unit 130 converts the RF signal in the radio frequency band into an IF band signal. The frequency converter 130 receives a local oscillation signal and an RF signal. The frequency converter 130 multiplies the local oscillation signal and the RF signal, and outputs the signal converted to the IF band by multiplication to the frequency band limiter 140.

The frequency band limiting unit 140 passes an IF band signal included in the signal output from the frequency conversion unit 130, attenuates a signal other than the IF band, and outputs the attenuated signal to the gain adjustment unit 150.
Gain adjusting section 150 performs gain adjustment on the IF band signal output from frequency band limiting section 140. The gain adjustment unit 150 amplifies the level of the signal attenuated by the signal processing in the frequency conversion unit 130 or the frequency band limiting unit 140 to a predetermined power level, and the amplified signal is sent to the analog-digital conversion unit 160. Output.

  The analog-digital conversion unit 160 performs sampling on the signal output from the gain adjustment unit 150 at a predetermined sampling frequency, converts the signal into a digital signal corresponding to the intensity of the analog signal, and converts the digital signal of time-series data Is generated. In addition, the analog-to-digital conversion unit 160 outputs the generated digital signal of time series data to the signal processing unit 170.

The signal digitized by the analog-digital conversion unit 160 is input to the signal processing unit 170. The signal processing unit 170 performs Fourier transform on the input signal, and calculates frequency information of the IF band signal. The frequency information includes power information and phase information for each frequency.
In addition, the signal processing unit 170 detects at which RF frequency the signal is present by measuring a change in the time direction in the frequency information of the IF band signal. At this time, the signal processing unit 170 separates received signals such as desired signals and interference signals included in the input digital signal based on the frequency change speed (sweep speed) of the local oscillation signal LO ₁ and the frequency information. Perform detection.

  FIG. 2 is a schematic block diagram illustrating a configuration example of the signal processing unit 170 in the present embodiment. As shown in the figure, the signal processing unit 170 includes a Fourier transform unit 171, a determination unit 172, a filter unit 173, a synchronization unit 174, a demodulation unit 175, and a decoding / error correction unit 176.

The Fourier transform unit 171 performs a Fourier transform on the digital signal of the time series data input from the analog-digital conversion unit 160 to convert it into a time domain signal. Based on the frequency change rate of the Fourier-transformed signal and the local oscillation signal LO ₁ , the determination unit 172 determines the IF band signal in the RF band of the signal corresponding to the frequency component having power equal to or higher than the predetermined threshold power P 0. The frequency is calculated, and it is determined whether or not the desired signal exists in the frequency band that is the sensing target in the RF signal received by the device itself. Further, the determination unit 172 detects the frequency, power, and phase in the RF band of the signal corresponding to the frequency component having power equal to or higher than the threshold power P0 in the IF band signal, and outputs the detection result as frequency information.
The filter unit 173 extracts a desired signal from the digital signal of the time series data based on the frequency information output from the determination unit 172. The synchronization unit 174 synchronizes with the extracted desired signal. The demodulator 175 demodulates the synchronized signal. The decoding / error correction unit 176 performs decoding and error correction on the demodulated signal to reproduce received data.

  Note that the signal conversion method for measuring changes in the time direction of frequency information from digital signals of digitized time-series data performs short-time Fourier transform, wavelet transform, Wigner distribution analysis, etc. in addition to Fourier transform. A time frequency conversion method may be used. The value to be detected may be a magnitude such as a correlation value, and is not limited to the signal power level.

FIG. 3 is a diagram illustrating an example of a radio frequency band signal, a local oscillation signal, and an IF band signal in the present embodiment. Here, a case where the local oscillation signal generation unit 120 generates the local oscillation signal LO ₁ having the frequency F ₁ will be described. Assume that the sweep rate of the local oscillation signal is Vosc1, and there are a desired signal (RF ₁ ) and an interference signal (RF ₂ and RF _M ) in the radio frequency band.
As shown in FIG. 3A, when the local oscillator 121 sweeps the local oscillation signal LO ₁ at the sweep speed Vosc1, the local oscillation signal LO ₁ and the local oscillation signal LO ₁ are doubled and N-multiplied to the IF band. The frequency-converted signals (IF ₁ , IF ₂ and IF _M ) transition in frequency in the IF band as time elapses.
At this time, the transition amount per unit time of the frequency of IF ₁ is the desired signal is equal to the sweep rate Vosc1 of the local oscillation signal LO _1. On the other hand, the frequency of the IF ₂ and IF _M is an interference signal varies at twice and M times the rate of the local oscillation signal Vosc1. A desired signal IF ₁ the transition speed based on the interference signal IF ₂ and IF _M can be separated. Further, by adding the frequency difference of the IF band signal detected at the same time to the frequency of the local oscillation signal at a certain time, the determination unit 172 included in the signal processing unit 170 has a radio frequency at which the detected signal exists. Can be determined.

  FIG. 3B is a waveform diagram showing a frequency change of the signal in the IF band when the sweep shown in FIG. In the figure, the horizontal axis indicates time, and the vertical axis indicates the frequency at which the signal after frequency conversion to the IF band is detected. As shown in the figure, the sweep rate of the local oscillation signal appears as the frequency change rate (slope) of the signal converted into the IF band. That is, assuming that the received signal such as a desired signal and an interference signal is a line spectrum in each frequency band, the line spectrum is shifted in frequency on the time axis by performing frequency conversion while sweeping the local oscillation signal. Will be observed. At this time, since the amount of frequency transition per unit time of the observed line spectrum becomes equal to the sweep speed of the local oscillation signal, it is possible to detect in which frequency band the line spectrum exists. Further, the frequency at which the desired signal and the interference signal exist can be determined by adding the frequency difference of the signal observed at that time to the oscillation frequency of the LO signal at a certain time.

FIG. 4 is a diagram illustrating another example of a radio frequency band signal, a local oscillation signal, and an IF band signal in the present embodiment. Here, the case where the local oscillation signal generation unit 120 generates the local oscillation signal LO ₁ having the frequency F ₁ will be described. It is assumed that the sweep speed of the local oscillation signal is Vosc1, and signals (RF ₁ and RF ₂ ) are present in the radio frequency band. RF ₁ is a desired signal and is located in the upper side band of the local oscillation signal LO ₁ . RF ₂ is an image band interference signal and is located in the lower sideband of LO ₁ .
As shown in FIG. 4A, when the local oscillator 121 sweeps the local oscillation signal LO ₁ at the sweep speed Vosc1, the signals (IF ₁ and IF ₂ ) frequency-converted to the IF band by the local oscillation signal LO ₁ are: As the time passes, the frequency in the IF band changes.

FIG. 4B is a waveform diagram showing the frequency change of the signal in the IF band when the sweep shown in FIG. 4A is performed. In the figure, the horizontal axis indicates time, and the vertical axis indicates the frequency at which the signal after frequency conversion to the IF band is detected. As shown in the figure, the sweep rate of the local oscillation signal appears as the frequency change rate (slope) of the signal converted into the IF band.
The amount of transition of the frequency of the desired signal IF ₁ per unit time is equal to −Vosc1. On the other hand, the interference signal IF ₂ is changed at a rate of the local oscillation signal Vosc1. That is, the transition speed is reversed. The determination unit 172 can separate the desired signal IF ₁ and the image band interference signal IF ₂ based on the difference in increase / decrease of the transition speed.

FIG. 5 is a flowchart of determination processing for detecting a desired signal and an interference signal performed by the signal processing unit 170 in the present embodiment. Here, a case where the local oscillator 121 included in the local oscillation signal generation unit 120 performs sweeping in a direction in which the frequency increases will be described.
The signal processing unit 170 receives the digital signal of the time-series data converted into the digital signal from the analog-digital conversion unit 160, the frequency and sweep speed of the local oscillation signal, and the determination unit 172 outputs the frequency for each frequency in the IF band. Power information and phase information are detected (step S101). Instead of the power information and phase information for each frequency, the frequency at which the power exceeding the threshold is detected may be detected.
The determination unit 172 measures the received power in the Fourier-transformed signal, and determines whether there is a signal whose measured received power is equal to or higher than a predetermined threshold power P0 (step S102). When there is no signal whose received power is equal to or higher than the threshold power P0 (step S102: NO), the determination unit 172 ends the process of detecting the received signal.

On the other hand, when there is a signal whose reception power is equal to or higher than the threshold power P0 (step S102: YES), the determination unit 172 determines whether or not the frequency change speed of the signal is Vosc1 (step S103). If speed is Vosc1 (step S103: YES), the lower sideband of frequency converted by a local oscillation signal _{LO 1 (Low side band; LSB} ) determines that component (step S104), and terminates the process for detecting a received signal To do.
If the frequency change rate of the signal is not Vosc1 (step S103: NO), the determination unit 172 advances the process to step S105.

The determination unit 172 determines whether or not the frequency change rate of the signal having the threshold power P0 or more is −Vosc1 (step S105). If the frequency change rate is −Vosc1 (step S105: YES), the local oscillation signal is determined. The upper side band (Upper Side Band; USB) component frequency-converted with LO ₁ is determined (step S106), and the process of detecting the received signal is terminated.
On the other hand, when the frequency change rate of the signal having the threshold power P0 or higher is not −Vosc1 (step S105: NO), the determination unit 172 advances the process to step S107.

The determination unit 172 determines whether or not the frequency change rate of the signal having the threshold power P0 or more is N × Vosc1 (step S107). If the frequency change rate is N × Vosc1 (step S107: YES), the local unit It is determined that the LSB component is frequency-converted with the Nth harmonic wave of the oscillation signal LO ₁ (step S108), and the process of detecting the received signal is terminated.
On the other hand, when the frequency change rate of the signal is not N × Vosc1 (step S107: NO), the determination unit 172 advances the process to step S109.

The determination unit 172 determines whether or not the frequency change rate of the signal having the threshold power P0 or more is −N × Vosc1 (step S109), and when the frequency change rate is −N × Vosc1 (step S109: YES). Then, it is determined that the signal is a USB component obtained by frequency conversion of the local oscillation signal LO _{1 with} the Nth harmonic wave (step S110), and the process of detecting the reception signal is ended.
On the other hand, when the frequency change rate of the signal is not −N × Vosc1 (step S109: NO), the determination unit 172 ends the process of detecting the reception signal.

As described above, in the IF band digital signal input from the analog-to-digital converter 160, the determination unit 172 uses the frequency change rate of the signal whose power is equal to or higher than the threshold power P0, the local oscillation signal LO ₁ , 2 × LO ₁ ,..., N × LO ₁ are compared with the frequency change speed (sweep speed). Thereby, it is possible to detect which frequency signal in the radio frequency band is a signal having power equal to or higher than the threshold power P0, and whether it is an LSB component or a USB component.
In this way, it is possible to specify whether the frequency conversion is performed using the fundamental wave of the local oscillation signal or the harmonic conversion thereof based on the frequency change speed (sweep speed).

FIG. 6 is a diagram illustrating an example of unnecessary waves generated in the receiver 100. In the receiver 100, a harmonic (unwanted wave) of a desired signal may be generated in the broadband LNA 110, the frequency conversion unit 130, the gain adjustment unit 150, or the like. This harmonic increases when the power of the desired signal is large.
For example, as shown in FIG. 6, when the desired signal frequency _{f 1} is obtained in a broadband LNA110 and frequency converter 130, twice the harmonic or frequency 2f ₁ with respect to the frequency _{f 1,} the desired signal sometimes harmonics of twice the frequency _{2f IF1} occurs for the frequency _{f IF1} of the converted IF band signal.
A harmonic detection method for determining whether or not harmonics are generated in the receiver 100 will be described. FIG. 7 is a diagram showing an outline of the harmonic detection method in the present embodiment. As shown in the figure, at the point where the IF frequency is 0 [Hz], it is detected when the graphs showing the frequency changes (the slopes are Vosc1, 2 × Vosc1, 3 × Vosc1) of the detected signals cross each other. Each signal can be determined as a harmonic generated in the receiver 100. In other words, a signal whose IF frequency is 0 [Hz] at the same time (timing) during frequency sweep of the local oscillation signal can be determined as a harmonic generated in the receiver 100.

  When the received power of the desired signal is large and harmonics of the desired signal are generated in the receiver 100, the gain adjustment of a circuit (for example, the wideband LNA 110, the frequency converting unit 130, the gain adjusting unit 150, etc.) in the receiver 100 is performed. By doing so, the generation of harmonics can be suppressed. Specifically, when the signal processing unit 170 detects that the harmonics of the desired signal are generated, the signal processing unit 170 reduces the gain in the wideband LNA 110, the frequency conversion unit 130, or the gain adjustment unit 150 to generate harmonics. Suppress.

However, when the received power of the interference signal is large, if the gain of the circuit in the receiver 100 is lowered, the desired signal may not be demodulated when the received power of the desired signal is weak.
FIG. 8 is a schematic diagram showing a case where a harmonic influences a desired signal. As shown in the figure, when the graph showing the frequency of the harmonics of the interference signal in the IF band intersects with the graph showing the frequency of the desired signal in the IF band, the interference signal harmonics interfere with the desired signal. End up. In this case, the frequency of the local oscillation signal output from the local oscillator 121 is changed to a frequency in which the frequency in the IF band of the harmonics of the interference signal and the frequency in the IF band of the desired signal do not overlap with each other. The influence of the interference signal can be reduced without adjusting the gain of the circuit. In addition, when the power level of the desired signal is weak relative to the power level of the interference signal, it is possible to reduce the influence of the desired signal from the interference signal in the IF band. The accuracy of detection can be further improved.
Specifically, when the signal processing unit 170 determines that the frequencies of the desired signal and the interference signal in the IF band overlap, the signal processing unit 170 does not overlap the frequencies of the desired signal and the interference signal in the IF band. The local oscillation signal generator 120 is controlled to make the frequency the frequency of the local oscillation signal LO ₁ .

In general, since a wideband receiver inputs a plurality of radio signals, a wideband LNA, a frequency converter, a gain adjuster, and the like approach power saturation, and harmonics and intermodulation distortion may occur in the receiver. As the signal power of the desired signal approaches saturation, errors in amplitude information and phase information become large and demodulation becomes difficult. Further, when the power of the interference signal approaches saturation, its harmonics and intermodulation distortion become interference components.
On the other hand, when the receiver 100 in the present embodiment detects an interference signal (image signal or harmonic band radio signal) with a large power, the gain of the broadband LNA 110, the frequency converter 130, or the gain adjuster 150 is detected. By performing the adjustment, harmonics generated in the receiver can be suppressed.

As described above, the receiver 100 in the present embodiment can detect and separate the desired signal and the image signal of the desired signal, and the interference signal frequency-converted with the harmonics of the local oscillation signal LO _1. The desired signal can be detected and separated. As described above, the receiver 100 can detect a desired signal without using a bandpass filter or an FIR filter for an RF band signal, so that the detection accuracy of the desired signal in the radio frequency band is improved. be able to. Since receiver 100 does not use a bandpass filter or FIR filter, the noise figure can be reduced and a weak desired signal can be demodulated.
In receiver 100, since the out-of-band suppression amount of the bandpass filter in the RF band may be small, interference signals may be suppressed using a wideband and low-loss filter.

In the determination process shown in FIG. 5, the frequency band for detecting the presence of the signal to be determined using the threshold power P0 may be limited to a specific frequency band. In this case, for example, an IF band in which the phase noise of the local oscillation signal LO ₁ output from the local oscillator 121 is lower than a predetermined level may be selected as a frequency band for detecting a signal to be determined. The predetermined level for the phase noise is determined in advance according to the reception performance required for the receiver 100.
In addition, when a digital filter is used after analog-to-digital conversion, the accuracy of detecting a radio signal can be improved by selecting the passband of the digital filter to be a low frequency, so that the phase noise of the local oscillation signal LO ₁ and The frequency band for detecting a signal in the signal processing unit 170 may be selected using the passband of the digital filter as a condition for selecting the IF band.
Further, a signal is detected by measuring in advance a frequency band that is less affected by spurious in the receiver 100 and an external interference signal, and selecting the frequency band as a frequency band in which the signal processing unit 170 detects a signal. It is effective to improve the accuracy of

In addition, the signal processing unit 170 may perform demodulation as well as frequency and power determination on the digital signal input from the analog-digital conversion unit 160. In particular, a signal modulated using a frequency modulation method or an amplitude modulation method can be easily demodulated. When the phase of the local oscillation signal LO ₁ output from the local oscillator 121 is controlled, not only the frequency of the local oscillation signal LO ₁ but also phase information indicating the initial phase of the carrier wave of the RF signal is used. Is synchronized with the phase of the local oscillation signal LO ₁ , the signal can be demodulated even when receiving a phase modulation signal such as QPSK (Quadrature Phase Shift Keying). In this case, when detecting a signal having a threshold power P0 or higher, the signal processing unit 170 calculates a frequency in the radio frequency band for the signal, and demodulates the signal using phase information indicating an initial phase at the calculated frequency. The phase information may be stored in advance in the signal processing unit 170 according to the radio frequency band in which the signal is detected.

  Further, the signal processing unit 170 may have a database that stores frequency usage information indicating the usage, the wireless power standard, the radio modulation scheme, the position used in the usage, and the like for each radio frequency band. . At this time, the signal processing unit 170 may use the frequency use information in the determination process illustrated in FIG. Thereby, the signal processing unit 170 can improve the detection accuracy of the RF signal in each radio frequency band. In addition, the signal processing unit 170 may demodulate the digital signal input from the analog-digital conversion unit 160 by performing demodulation corresponding to the modulation scheme indicated by the frequency use information. The signal processing unit 170 may acquire the frequency usage information by inquiring of a server device having a database that stores the frequency usage information.

In the above-described embodiment, the configuration in which the receiver 100 is a single device has been described. However, the present invention is not limited to this, and a reception system including a plurality of devices may be used.
FIG. 9 is a schematic block diagram illustrating a configuration of a reception system 200 as a modification of the receiver 100. In the receiving system 200, the same components as those of the receiver 100 shown in FIG. The reception system 200 includes a reception device 210, a signal processing device 270, and a network line 280 that connects the reception device 210 and the signal processing device 270. The receiving system 200 includes two devices, a receiving device 210 and a signal processing device 270.
The receiving apparatus 210 includes a wideband LNA 110, a local oscillation signal generation unit 120, a frequency conversion unit 130, a frequency band limiting unit 140, a gain adjustment unit 150, and an analog-digital conversion unit 160. The output of the analog-digital conversion unit 160 is transmitted to the signal processing device 270 provided at a position different from the receiving device 210 via the network line 280. Similarly to the signal processing unit 170, the signal processing device 270 performs Fourier transform on the input signal and calculates frequency information of the IF band signal. Further, the signal processing device 270 detects at which RF frequency the signal is present by measuring a change in the time direction in the frequency information of the IF band signal. At this time, the signal processing device 270 separates and detects the received signal based on the frequency change speed (sweep speed) of the local oscillation signal LO ₁ and the frequency information.
In order to perform the separation and detection of the received signal performed by the signal processing device 270 at a higher speed, it is desirable to perform using a computing device having a high computing capacity. On the other hand, in the receiving system 200, a high-performance workstation or the like provided at a different position from the receiving device 210 can be used as the signal processing device 270 via the network line 280. In addition, a configuration in which a plurality of receiving devices 210 are arranged at different positions and the signal processing device 270 is connected to each receiving device 210 via the network line 280 is a common database for sharing monitoring results such as radio wave usage conditions. It is suitable for construction.
Note that the signal transmitted from the receiving apparatus 210 to the signal processing apparatus 270 may be an analog signal before being converted into a digital signal by the analog-digital conversion unit 160. In addition, when transmitting from the receiving apparatus 210 to the signal processing apparatus 270, any one of an analog signal transmission system and a digital signal transmission system may be selected.

Further, in the above-described embodiment, the influence of the interference signal included in the reception signal may be reduced in the same manner as the case where the influence of the unnecessary wave generated inside the receiver 100 is reduced. FIG. 10 is a diagram illustrating an example of the local oscillation signal and the sweep speed (slope) of the harmonics thereof. In the figure, the horizontal axis indicates time, and the vertical axis indicates the frequency at which the signal after frequency conversion to the IF band is detected. In a region where the graph showing the frequency change of the desired signal and the graph showing the frequency change of the interference signal overlap, an error in determining the received power and performing demodulation becomes large. After detecting the presence of the interference signal, the signal processing unit 170 may select the frequency of the local oscillation signal LO ₁ so that a region affected by the interference signal does not occur for the desired signal. As a result, it is possible to improve the accuracy of reception power determination and demodulation.

Further, the signal processing unit 170 of the above-described embodiment generates a digital signal whose frequency changes as a frequency conversion signal based on the detected frequency change pattern of the desired signal, and records the generated frequency conversion signal. You may make it multiply with the digital signal of the placed time series data. More specifically, when the detected speed change frequency of the desired signal is V1, a signal with a sweep speed of V1 is generated as a frequency conversion signal, and a digital signal of time-series data recorded and generated The frequency conversion signal thus multiplied is multiplied. In this case, since the frequency of the desired signal and the frequency of the frequency conversion signal are constant, the frequency of the desired signal is constant in the digital signal multiplied by the frequency conversion signal. On the other hand, the frequency of the interference signal changes according to the sweep speed of the local oscillation signal and the sweep speed of the frequency conversion signal even after multiplication by the frequency conversion signal.
In this way, by multiplying the frequency conversion signal, the center frequency of the interference signal changes at a new change speed, the change speed of the desired signal becomes zero, and the center frequency becomes constant. Improve the accuracy of separating and removing interference signals by limiting the band of a digital signal containing a desired signal with a constant center frequency using a digital filter that limits the band other than the band of the desired signal. be able to.
In this case, the signal processing unit 170 may be configured as shown in FIG. FIG. 11 is a schematic block diagram illustrating a modified example of the configuration of the signal processing unit 170. As shown in the figure, a frequency conversion unit 277 is newly provided in the configuration of the signal processing unit 170 shown in FIG. The frequency conversion unit 277 generates a frequency conversion signal based on the speed at which the frequency of the desired signal detected by the determination unit 172 changes. In addition, the frequency conversion unit 277 multiplies the digital signal of the time series data input from the analog-digital conversion unit 160 by the generated frequency conversion signal, and passes the signal obtained by the multiplication to the filter unit 173. Output. The filter unit 173 extracts a desired signal from the signal input from the frequency conversion unit 277 instead of the time-series data digital signal.

In the signal processing unit 170 of the above-described embodiment, the detected desired signal may be used as a frequency conversion signal, and the frequency conversion signal may be multiplied by a time-series data digital signal. FIG. 12 is a graph showing the frequency change of the IF signal when the detected desired signal is multiplied by the time-series data digital signal using the frequency conversion signal. FIG. 12A is a diagram showing the local oscillation signal and its harmonic sweep speed (gradient) before multiplication by the frequency conversion signal. FIG. 12B is a diagram showing the sweep speed (slope) of the local oscillation signal and its harmonics after multiplication by the frequency conversion signal. Since the difference between the frequency of the desired signal and the frequency of the frequency conversion signal is always constant, conversion is performed by multiplying the time-series data digital signal input from the analog-digital conversion unit 160 by the frequency conversion signal. The frequency of the desired signal in the later digital signal can be made constant as shown in FIG. In addition, by making the frequency of the desired signal constant, various signal processing necessary for reception signal processing can be performed using a general processing method.
In this case, the signal processing unit 170 may be configured as shown in FIG. FIG. 13 is a schematic block diagram illustrating a modification of the configuration of the signal processing unit 170. As shown in the figure, a frequency conversion unit 377 is newly provided in the configuration of the signal processing unit 170 shown in FIG. The frequency conversion unit 377 outputs the digital signal of the time series data input from the analog-digital conversion unit 160 to the Fourier transform unit 171. Further, the frequency conversion unit 377 multiplies the digital signal of the recorded time series data as the frequency conversion signal by using the desired signal detected by the determination unit 172, and outputs the multiplication result to the filter unit 173. The filter unit 173 extracts a desired signal from the signal input from the frequency conversion unit 377 instead of the digital signal of time series data.

Further, in the modified example of the signal processing unit 170 shown in FIG. 13 described above, a frequency conversion signal is generated based on the detected frequency change pattern of the desired signal, and the frequency conversion unit 377 converts the frequency conversion signal into time series. The data digital signal may be multiplied. Note that the frequency change pattern includes a case where the change of the local oscillation signal used for frequency conversion is not continuous but discretely as in a frequency hopping receiver. Even in this case, the frequency of the desired signal can be made constant as shown in FIG. Thereby, the frequency component of the desired signal after Fourier transform can be emphasized, and signal detection performance can be improved. Since the detected frequency change pattern of the desired signal has a correlation with the frequency change pattern of the local oscillation signal, the frequency conversion signal may be generated based on the frequency change pattern of the local oscillation signal.
Further, the frequency conversion using the frequency conversion signal having the same pattern as the detected frequency change pattern of the desired signal may be performed before conversion to a digital signal as shown in FIG. 14, for example. FIG. 14 is a schematic block diagram illustrating a configuration of a modified example of the receiver 100. In addition to the configuration of the receiver 100, the receiver 300 includes a frequency conversion signal generation unit 320, a frequency conversion unit 330, and a frequency band limiting unit 340. The frequency conversion signal generation unit 320 generates a local oscillation signal LO ₂ whose frequency changes in the same pattern as the frequency change pattern of the desired signal frequency-converted to the intermediate frequency by the local oscillation signal LO ₁ . The frequency converting unit 330 multiplies the signal output from the frequency band limiting unit 140 by the local oscillation signal LO ₂ and converts the frequency of the signal output from the frequency band limiting unit 140. The frequency band limiting unit 340 passes a signal corresponding to the frequency band to be sensed among the signals frequency-converted by the frequency converting unit 330, attenuates signals other than the frequency band, and outputs the attenuated signal to the gain adjusting unit 150. . Thus, frequency conversion may be performed on the analog signal, and the frequency of the desired signal may be made constant in the signal processing unit 170.

In the above-described embodiment, the configuration in which the radio frequency band RF signal is converted into the IF band signal has been described. However, the present invention is not limited thereto, and the radio frequency band RF signal is converted into the baseband signal. It may be.
In the above-described embodiment, the configuration in which the sweep speed is set to a predetermined constant speed has been described. However, the present invention is not limited to this, and the sweep speed may be changed as time passes. As a method of changing the sweep speed, for example, the frequency may be discretely changed like frequency hopping.
Further, the signal processing unit 170 may perform feedback control for controlling the sweep speed based on the determination result or the signal demodulation result. For example, the sweep speed of the local oscillation signal LO ₁ may be decreased when the frequency spectrum corresponding to the desired signal after FFT spreads in the signal processing unit 170 beyond a predetermined frequency width. Also, when the power level of the frequency spectrum corresponding to the desired signal after the FFT in the signal processing unit 170 falls below the power a predetermined, may slow down the sweep rate of the local oscillator signal LO _1. Further, when the signal error rate when the signal processing unit 170 demodulates and decodes the desired signal is greater than or equal to a predetermined value, the sweep speed of the local oscillation signal LO ₁ may be reduced. By performing control to reduce the sweep speed of the local oscillation signal LO ₁ based on the desired signal detected by the signal processing unit 170, the spread of the frequency spectrum of the desired signal can be suppressed, and the accuracy of detecting the desired signal is improved. Can be made.

  A program for realizing the functions of the receiver and the receiving system in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed. You may perform the process which determines the presence or absence of a signal. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

100, 300 ... receiver (reception system)
110 ... Broadband LNA
DESCRIPTION OF SYMBOLS 120 ... Local oscillation signal generation part 121 ... Local oscillator 130 ... Frequency conversion part (1st frequency conversion part)
140, 340 ... Frequency band limiting unit 150 ... Gain adjusting unit 160 ... Analog-digital conversion unit 170 ... Signal processing unit 171 ... Fourier transform unit 172 ... Determination unit 173 ... Filter unit 174 ... Synchronization unit 175 ... Demodulation unit 176 ... Decoding / Error correction unit 200 ... reception system 210 ... reception device 270 ... signal processing device 277, 377 ... frequency conversion unit 280 ... network line 320 ... frequency conversion signal generation unit 330 ... frequency conversion unit (second frequency conversion unit)

Claims (13)

A local oscillation signal generator for generating a local oscillation signal to be swept in frequency;
A first frequency conversion unit for frequency-converting and outputting the radio signal by multiplying the input radio signal by the local oscillation signal;
Converting the frequency-converted radio signal into a frequency-domain signal, and the radio signal based on a speed at which the frequency of the signal in the frequency domain obtained by the conversion changes and a speed at which the frequency of the local oscillation signal is swept A signal processing unit that detects a signal included in the signal and separates the detected signal. The receiving system according to claim 1,
The signal processing unit
For each signal in the frequency domain, calculating the frequency of the radio signal relative to the signal from the frequency of the signal, the speed at which the signal transits the frequency, and the speed at which the frequency of the local oscillation signal is swept. Receiving system characterized. The receiving system according to claim 1 or 2,
The signal processing unit further includes:
When the frequency of the signal in the frequency domain increases when the local oscillation signal generator sweeps to increase the frequency of the local oscillation signal, the radio signal corresponding to the detected signal is below the local oscillation signal. Determine that the signal is a waveband,
When the frequency of the signal in the frequency domain decreases when the local oscillation signal generator sweeps to increase the frequency of the local oscillation signal, the radio signal corresponding to the detected signal is an upper side wave of the local oscillation signal. It is determined that the signal is a band,
When the frequency of the signal in the frequency domain decreases when the local oscillation signal generator sweeps to reduce the frequency of the local oscillation signal, the radio signal corresponding to the detected signal is below the local oscillation signal. Determine that the signal is a waveband,
When the frequency of the signal in the frequency domain increases when the local oscillation signal generator sweeps to reduce the frequency of the local oscillation signal, the radio signal corresponding to the detected signal is an upper side wave of the local oscillation signal. It is determined that the signal is a band signal. The receiving system according to any one of claims 1 to 3,
The signal processing unit further includes:
Among the signals in the frequency domain, there are a plurality of signals whose frequencies change at an integer multiple of the frequency of sweeping the frequency of the local oscillation signal, and the frequency of the signal becomes 0 [Hz] at the same time. In this case, it is determined that the signal is a harmonic generated in the own system. The receiving system according to claim 4,
The signal processing unit
When it is determined that harmonics are generated inside the own system, the gain in the first frequency converter is reduced. The receiving system according to any one of claims 1 to 5,
The signal processing unit
A signal contained in the radio signal is detected using a signal obtained by multiplying the local oscillation signal in a frequency band in which the phase oscillation is swept by a local oscillation signal in a frequency band with a small phase noise. Receiving system. The receiving system according to any one of claims 1 to 6,
The signal processing unit further includes:
The receiving system, wherein the detected signal is demodulated using a frequency of the local oscillation signal and information indicating an initial phase of a carrier wave of the radio signal. The receiving system according to any one of claims 1 to 7,
The signal processing unit
Detecting a signal included in the radio signal using frequency information indicating a use application, a radio power standard, a radio modulation scheme, and a position used in the use application for each frequency band in the radio signal. Receiving system. The receiving system according to claim 3,
The signal processing unit
Detecting a desired signal included in a target frequency band for detecting a signal in the radio signal, a signal included in a frequency band other than the target frequency band, and an interference signal that is an image band signal of the desired signal;
The frequency band of the local oscillation signal whose frequency is not matched with the frequency of the desired signal is selected as a frequency band for sweeping the frequency of the local oscillation signal. A control system for sweeping the local oscillation signal in the selected frequency band is performed on the local oscillation signal generator. The receiving system according to any one of claims 1 to 9,
The signal processing unit
Generating a frequency conversion signal in which the frequency is swept at a speed corresponding to the speed of change of the frequency of the detected signal;
A receiving system, wherein the frequency conversion signal is multiplied by the frequency-converted radio signal, and a signal included in the radio signal is detected based on the signal obtained by the multiplication. The receiving system according to any one of claims 1 to 9,
A frequency conversion signal generation unit that generates a frequency conversion signal in which the frequency is swept at a speed corresponding to a change speed of the frequency of the local oscillation signal;
A second frequency converter that multiplies the frequency conversion signal and the frequency-converted radio signal and outputs a signal obtained by the multiplication; and
The signal processing unit
A reception system that detects a signal included in the radio signal based on a signal output from the second frequency conversion unit. The receiving system according to claim 11, wherein
The second frequency conversion unit performs multiplication on an analog signal. The receiving system according to any one of claims 1 to 12,
The signal processing unit
A receiving system that controls a speed of changing a frequency of the local oscillation signal based on the detected signal.

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