JP2017011365A - Receiver and reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver and a reception method, capable of compensating frequency shift corresponding to Doppler shift while keeping sufficient resistance for an interference wave, with a simple configuration.SOLUTION: A receiver 1 includes: a frequency synthesizer 12 for generating a local oscillation signal by dividing an output of a reference frequency source 11 according to an input division number; a demodulation part 14 for demodulating a reception signal whose frequency is converted with the local oscillation signal; and a digital frequency compensation part 15 for controlling the number of division according to an amount of frequency deviation of the reception signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a receiving device and a receiving method, and more particularly to a receiving device mounted on an artificial satellite and a receiving method thereof.

  The receiving device mounted on the artificial satellite has a function of receiving a modulated command signal from the ground station, demodulating it, and passing it to each part of the artificial satellite.

  In recent years, geostationary satellites are located close to each other, and when a command is transmitted to an artificial satellite, a command signal for an adjacent artificial satellite may become an interference wave, resulting in a communication failure. For this reason, there is an increasing demand for receivers with band restrictions so as not to be affected by the channels of adjacent artificial satellites.

  In addition, even for a receiver installed on a satellite operated in geostationary orbit, the frequency shift of the received carrier wave (Doppler shift) due to the Doppler effect due to the relative motion of the satellite relative to the ground station until the orbit is inserted. It is necessary to cope with. For example, it is required to design a receiving apparatus so that it can be demodulated even if it shifts to any frequency within a band having a width of about +/− 23 ppm with respect to a reference carrier wave.

  For example, Patent Documents 1 to 5 disclose techniques related to compensation for the frequency deviation.

  Patent Document 1 discloses a so-called heterodyne radio receiver that performs frequency conversion using a local oscillation signal generated by a VCXO (Voltage Controlled Crystal Oscillator) and a frequency multiplier and demodulates a transmission signal. It is disclosed. The wireless receiver disclosed in Patent Document 1 repeatedly sweeps the frequency of a local oscillation signal with a frequency bandwidth greater than or equal to the frequency drift width of the carrier frequency or with a frequency bandwidth greater than or equal to the frequency drift width of the local oscillation signal. .

  Patent Document 2 discloses a technique for capturing a signal from a satellite that is shifted from a center frequency by Doppler shift. The capturing unit identifies a frequency in a protruding manner in a frequency characteristic obtained by time-frequency conversion of a signal obtained by squaring a satellite signal from each satellite, and captures each satellite signal based on the specific frequency.

  The synthesizer described in Patent Document 3 generates a local oscillation signal based on a reference oscillation signal output from a reference oscillator having a MEMS vibrator, detects a frequency fluctuation of the local oscillation signal, and based on the detected frequency fluctuation. Adjust the frequency of the local oscillation signal.

  In addition, the synthesizer described in Patent Document 4 uses a frequency adjustment unit when adjusting the frequency of a local oscillation signal generated based on a reference oscillation signal output from a MEMS vibrator, and a frequency adjustment in which the quality of the output signal becomes a quality limit threshold. The unit is configured to be within F.

  Further, Patent Document 5 discloses a delta sigma modulation type fractional frequency division PLL frequency synthesizer that performs fractional frequency division by modulating a frequency divider that divides the output frequency of the voltage controlled oscillator.

International Publication No. 2006/073013 International Publication No. 2009/019754 International Publication No. 2009/116262 JP 2009-194615 A JP 2005-295341 A

  Since the command receiving apparatus supports Doppler shift as described above, it is necessary to use a receiver including an analog frequency compensation circuit or a circuit that can allow a frequency shift in the demodulator itself.

  When the former method is used, there is a problem that the configuration becomes complicated. In the case of a configuration using a VCXO in the frequency compensation circuit as described in Patent Document 1, 1. The allowable frequency range is limited to the variable frequency range of VCXO. 2. Since the frequency of the VCXO fluctuates, another frequency source is required to supply a reference frequency to other analog parts and digital parts. Since an analog circuit is used for control, there is a problem that a circuit for compensating for a frequency shift due to environmental fluctuations such as temperature and atmospheric pressure is separately required.

  When the latter method is used, in recent years, the Ka band (30 GHz band) has been actively used for satellite communication due to the tightness of the frequency band. In order to allow such a large frequency shift in the demodulator, a simple configuration is required. It has become difficult to realize. In the configuration described in Patent Document 2, a satellite signal from each satellite is squared, the signal is time-frequency converted, the obtained frequency characteristic is generated, and a circuit for specifying the frequency of the protruding aspect is provided. It has a complicated structure. Patent Documents 3 to 5 do not disclose a technique that can cope with the Doppler shift while sufficiently limiting the bandwidth with a simple configuration.

  An object of the present invention is to provide a receiving apparatus and a receiving method capable of compensating for a frequency shift corresponding to a Doppler shift while maintaining sufficient resistance against an interference wave with a simple configuration.

  A receiving apparatus according to the present invention includes a frequency synthesizer that generates a local oscillation signal obtained by dividing the output of a reference frequency source based on an input frequency division number, and a demodulation that demodulates a reception signal that has been frequency-converted by the local oscillation signal. And a digital frequency compensation unit that controls the frequency division number based on the frequency shift amount of the received signal.

  The reception method of the present invention generates a local oscillation signal obtained by dividing the output of a reference frequency source based on an input frequency division number, demodulates the reception signal frequency-converted by the local oscillation signal, and receives the reception signal. The frequency division number is controlled based on the frequency shift amount.

  According to the present invention, it is possible to compensate for the frequency shift corresponding to the Doppler shift while maintaining sufficient resistance against an interference wave with a simple configuration.

FIG. 1 is a block diagram showing the configuration of the first embodiment. FIG. 2 is a flowchart showing the operation of FIG. FIG. 3 is a block diagram showing the configuration of the second embodiment. FIG. 4 is a flowchart showing the operation of FIG. FIG. 5 is a block diagram showing a configuration of the third embodiment. FIG. 6 is a flowchart showing the operation of FIG.

  Hereinafter, the configuration of the embodiment of the present invention will be described using a command receiving device mounted on an artificial satellite as an example.

The command receiving device receives the modulated signal from the ground station, demodulates it, and delivers the signal to the satellite. In recent years, satellite arrangements on geostationary satellites are close to each other, and when a command is transmitted to a satellite, a command signal for an adjacent satellite may become an interference wave, which may cause a communication failure. For this reason, there is an increasing demand for a command receiving device that limits the band of a received carrier wave and is not affected by the channel of an adjacent satellite. By using the present invention and configuring the receiving apparatus so as not to react to signals outside the desired band, it is possible to design a receiving apparatus that is resistant to jamming waves. With the configuration of the present invention, the following effects can be obtained.
・ Can handle wide frequency shifts.

Since the variable frequency range of the VCO (Voltage Controlled Oscillator) used in the synthesizer is the frequency range that can be pulled in, the bandwidth can be increased. Further, since the frequency compensation is performed digitally, stable performance independent of environmental conditions such as temperature can be obtained.
-The receiver configuration is simplified.

  Compared with the frequency compensation performed by analog, the number of components is reduced, and it can be created at low cost. In particular, since the reference frequency source that is separately required for the demodulator can be shared with that of the local oscillation signal, significant simplification is achieved. Further, in the case of a receiver having a demodulating unit using a phase synchronization circuit, the demodulating unit also serves as frequency detection, and thus further simplification is possible.

  Hereinafter, the configuration of an embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the receiving device 1 according to the first embodiment of the present invention includes a frequency synthesizer 12 that generates a local oscillation signal obtained by dividing the output of the reference frequency source 11 based on an input frequency dividing number. A frequency conversion unit 13 that performs frequency conversion using a local oscillation signal is provided. Further, a demodulator 14 that demodulates the received signal frequency-converted by the local oscillation signal, and a digital frequency compensator 15 that controls the frequency division number input to the frequency synthesizer 12 are provided.

  Further, the digital frequency compensator 14 pulls in the received signal when the demodulator 14 does not detect the received signal, and based on the frequency shift amount of the received signal detected when the demodulator 14 detects the received signal. The frequency dividing number input to the frequency synthesizer 12 is controlled.

  The receiving device 1 needs to detect the frequency of the carrier wave of the received signal in order to detect the frequency shift. In general, FM modulation or PM modulation is used for satellite communication. For this reason, the demodulator 14 includes a phase synchronization circuit 141 and can easily obtain the frequency shift amount of the carrier wave of the received signal. The receiving apparatus 1 uses the obtained frequency shift amount to control the frequency division number of the frequency synthesizer 12 and compensate for the frequency shift.

  As the reference frequency source 11, for example, a TCXO (Temperature Compensated Crystal Oscillator) or an OCXO (Oven Controlled Crystal Oscillator) may be used.

  As the frequency synthesizer 12, for example, a fractional type frequency synthesizer may be used. For the frequency synthesizer 12, a variable frequency range, that is, a VCO having a wide pull-in frequency range is used.

  The demodulator 14 demodulates the FM modulated or PM modulated received signal converted to the intermediate frequency. The frequency characteristic of the demodulator 14 is a frequency characteristic in which the band is limited so that it is not included in the frequency range in which the command signal for the adjacent satellite is normally demodulated. The demodulator 14 includes a phase synchronization circuit 141, and the phase synchronization circuit 141 acquires the frequency shift amount of the received signal.

  Furthermore, the receiving apparatus 1 includes a digital frequency compensator 15 for frequency acquisition because the carrier wave of the received signal is shifted in frequency. For example, as shown in FIG. 1, the digital frequency compensation unit 15 includes a frequency characteristic extension unit 151 that extends the frequency characteristic of the demodulation unit 14, and a pull-in detection that detects whether the demodulation unit 14 pulls in the frequency of the carrier wave. Part 152. The demodulator 14 is configured to be able to temporarily expand the frequency characteristics according to an instruction from the frequency characteristics expansion unit 151.

  Next, the operation of this embodiment will be described. FIG. 2 is a flowchart showing the operation of FIG.

  First, the pull-in detection unit 152 determines whether or not the carrier frequency is being pulled in (step S1). If the frequency of the carrier wave is not drawn, that is, if the received signal is not detected, the frequency characteristic expanding unit 151 determines that there is a frequency deviation in the carrier wave of the received signal, and extends the frequency characteristic of the demodulating unit 14. (Step S2). Then, it is determined whether a received signal has been detected (step S3). If detected, the demodulator 14 detects the frequency shift amount of the carrier wave of the received signal (step S4). If not detected, the process returns to step S2, and the frequency characteristics are further expanded within a range in which no interference wave is drawn.

  The digital frequency compensation unit 15 controls the frequency division number input to the frequency synthesizer 12 according to the frequency shift amount detected by the demodulation unit 14 (step S5).

  The frequency characteristic expansion unit 151 returns the frequency characteristic of the demodulation unit 14 to the normal frequency characteristic (step S6).

  As described above, according to the configuration of the present embodiment, when the frequency is not drawn, the frequency characteristic extension unit 151 temporarily extends the frequency characteristic of the demodulation unit 14 and the carrier wave of the received signal is drawn. With a simple configuration, the frequency shift can be compensated even if there is a large Doppler shift with respect to the frequency characteristic of the demodulator 14. In addition, when the carrier wave of the received signal is drawn, the frequency characteristic of the demodulator 14 is returned to the normal frequency characteristic before the expansion, so that the demodulator 14 does not react to frequencies other than the specified frequency at normal times. Sufficient tolerance can be obtained against interference waves.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing the configuration of the second embodiment.

  As shown in FIG. 3, the digital frequency compensation unit 16 of the receiving device 2 includes a frequency characteristic limiting unit 161 that limits a frequency characteristic based on an input signal, instead of the frequency characteristic extending unit 151. Different from the embodiment. The demodulator 17 of this embodiment has a frequency characteristic that can be demodulated with sufficient quality over the entire range where the Doppler shift of the received signal is performed.

  Next, the operation of this embodiment will be described. FIG. 4 is a flowchart showing the operation of FIG.

  The frequency characteristic restricting unit 161 restricts the frequency range input to the demodulating unit 17 so that the command signal for the adjacent satellite does not become an interference wave in normal times.

  First, the pull-in detection unit 152 determines whether the frequency of the carrier wave is being pulled in as in the first embodiment (step S1). If the frequency is not pulled in, the frequency characteristic limiting unit 161 relaxes the frequency characteristic limitation on the demodulating unit 17 (step S7). It is determined whether a received signal has been detected (step S3), and if detected, the demodulator 17 detects the amount of frequency shift (step S4). If not detected, the process returns to step S7, and the restriction on the frequency characteristics is further relaxed within a range in which no interference wave is drawn.

  The digital frequency compensation unit 16 controls the frequency division number input to the frequency synthesizer 12 in accordance with the frequency shift amount detected by the demodulation unit 17.

  The frequency characteristic limiter 161 limits the frequency range for the demodulator 17 so that the command signal for the adjacent satellite does not become an interference wave, as before relaxation (step S7).

  As described above, according to the configuration of the present embodiment, the frequency characteristic limiting unit 161 limits the frequency range that is normally input to the demodulating unit 17 so that the command signal for the adjacent satellite does not become an interference wave. Is not pulled in, the restriction on the frequency range for the demodulator 17 is temporarily relaxed, and the carrier wave of the received signal is drawn. For this reason, with a simple configuration, it is possible to compensate for the frequency shift even if there is a Doppler shift while maintaining sufficient resistance against an interference wave in a normal state.

  Next, a third embodiment of the present invention will be described. FIG. 5 is a block diagram showing a configuration of the third embodiment.

  As shown in FIG. 5, in the receiving apparatus 3 of this embodiment, the digital frequency compensation unit 18 includes first and second sweep units 181 that continuously change the frequency synthesizer frequency division number. Different from the embodiment.

  Next, the operation of this embodiment will be described. FIG. 6 is a flowchart showing the operation of FIG.

  First, the pull-in detection unit 152 determines whether the carrier frequency is being pulled in (step S1). If the frequency is not drawn, the sweep unit 181 continuously changes the frequency division number of the frequency synthesizer 12 to sweep the frequency range (step S9).

  The pull-in detection unit 1152 determines whether a reception signal is detected (step S3), and when the reception signal is detected, the sweep unit 181 stops changing the frequency division number (step S10).

  As described above, according to the configuration of the present embodiment, when the frequency is not drawn, the frequency division number of the frequency synthesizer 12 is continuously changed, and when the reception signal is detected, the frequency division number is changed. Stop. For this reason, as in the first and second embodiments, with a simple configuration, the frequency shift is compensated for the Doppler shift while maintaining sufficient resistance against interference waves in normal times. Can do.

  While the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

1, 2, 3 Receiver 11 Reference frequency source 12 Frequency synthesizer 13 Frequency conversion unit 14, 17 Demodulation unit 15, 16, 18 Digital frequency compensation unit 141 Phase synchronization circuit 151 Frequency characteristic expansion unit 152 Acquisition detection unit 161 Frequency characteristic limitation unit 181 sweep

Claims (5)

A frequency synthesizer that generates a local oscillation signal obtained by dividing the output of the reference frequency source based on the input frequency division number;
A demodulator that demodulates the received signal frequency-converted by the local oscillation signal;
A digital frequency compensator for controlling the frequency division number based on the frequency shift amount of the received signal;
A receiving device. The digital frequency compensator is
When the frequency of the carrier wave is not drawn, the frequency characteristic of the demodulator is temporarily expanded, and when the received signal is detected, the frequency division number input to the frequency synthesizer is controlled based on the frequency shift amount of the received signal And a frequency characteristic expansion unit that returns the frequency characteristic to a frequency characteristic before expansion,
The receiving device according to claim 1. The digital frequency compensator is
When the frequency of the carrier wave is not drawn, the restriction on the frequency range input to the demodulator is temporarily relaxed, and when the received signal is detected, the frequency is input to the frequency synthesizer based on the frequency shift amount of the received signal. A frequency characteristic limiting unit that controls a frequency division and limits the frequency range;
The receiving device according to claim 1. The digital frequency compensator is
When the frequency of the carrier wave is not drawn, the frequency synthesizer is continuously changed in frequency, and when a received signal is detected, a sweep unit that stops the frequency sweep is included.
The receiving device according to claim 1. A local oscillation signal is generated by dividing the output of the reference frequency source based on the input frequency division number,
Demodulate the received signal frequency-converted by the local oscillation signal,
A receiving method for controlling the frequency division number based on a frequency shift amount of the received signal.

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