JP2023079661A - Wireless station and method for correcting frequency error - Google Patents

Abstract

To provide a wireless station and a method for correcting frequency errors with which it is possible to suppress a variation in the frequency accuracy of each oscillator in a wireless station equipped with a plurality of oscillators.SOLUTION: A wireless station 1 comprises: a first oscillator 11 for outputting a first reference signal whose first target value is a target frequency; at least one second oscillator 12 for outputting a second reference signal whose second target value, consisting of the first target value with a target deviation added, is a target frequency; and a signal generation unit 26 for generating an object signal whose first intermediate frequency is a target frequency, on the basis of the second reference signal. The wireless station 1 further includes: a demodulation unit 33 for demodulating a second intermediate frequency signal generated for the object signal so as to generate a demodulated signal; a deviation detection unit 34 for detecting a frequency deviation between the first and the second reference signals on the basis of the demodulated signal; and an error correction unit 35 for correcting a frequency error of the second reference signal with respect to the second target frequency in accordance with a discrepancy of the frequency deviation from the target deviation.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radio station and frequency error correction method.

The local oscillator is composed of an oscillation circuit composed of discrete components and a PLL (Phase-Locked Loop)-VCO (Voltage Controlled Oscillator) having one reference frequency oscillator. An example of a radio station equipped with this type of local oscillator is disclosed in Patent Document 1.

A PLL-VCO may be realized by a PLL IC (Integrated Circuit) in which a VCO is built. The PLL IC enables FM (Frequency Modulation), specifically FSK (Frequency Shift Keying), in a wide band of 10 MHz or more and 1400 MHz or less.

JP-A-9-326752

When the PLL IC described above is used near an integer multiple of the oscillation frequency of the reference frequency oscillator that constitutes the PLL-VCO, integer boundary spurious may occur. When an integer boundary spurious occurs, the transmitting radio station cannot meet the spurious standards stipulated by the Radio Law, and the receiving radio station may experience spurious reception in which radio waves other than the desired radio wave are received. .

In order to suppress the influence of integer boundary spurious on transmission and reception, there are radio stations that have a plurality of reference frequency oscillators and switch between the plurality of reference frequency oscillators. A frequency error occurs in the reference frequency oscillator due to aging. The magnitude of the frequency error due to aging may vary from reference frequency oscillator to reference frequency oscillator.

For example, in a radio station that communicates with a base station, a reference frequency oscillator that is used when frequency-converting a received signal received from the base station is adjusted based on the received signal to match the reference frequency oscillator of the base station. It is possible to correct the frequency error of the reference frequency oscillator provided by the station. By correcting the frequency error as described above, the frequency accuracy of the reference frequency oscillator used during reception can be maintained. However, since the reference frequency oscillator used to generate the transmission signal to be transmitted to the base station cannot correct the frequency error as described above, the frequency accuracy may deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a radio station and a frequency error correction method capable of suppressing variation in frequency accuracy of each oscillator in a radio station equipped with a plurality of oscillators. Purpose.

In order to achieve the above object, the radio station according to the first aspect of the present invention includes:
a first oscillator that outputs a first reference signal whose first target value is the target frequency;
at least one second oscillator for outputting a second reference signal having a target frequency as a second target value obtained by adding a target deviation to the first target value;
a signal generator that generates a target signal having a target frequency at a first intermediate frequency based on the second reference signal;
frequency-converting the target signal using the first reference signal to generate a second intermediate frequency signal whose frequency is a second intermediate frequency lower than the first intermediate frequency; a demodulator that generates a demodulated signal by demodulating;
a deviation detector that detects a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal;
an error correction unit that corrects the frequency error of the second reference signal with respect to the second target value according to the deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation;
Prepare.

Preferably, the signal generating section generates the target signal, which is a modulated signal, by performing modulation based on input target data and the second reference signal.

Preferably, the signal generator generates the target signal that is a non-modulated signal based on the second reference signal.

Preferably, the signal generator generates a conversion signal that is a non-modulated signal based on the first reference signal,
receiving a signal generated by performing modulation based on a target signal whose frequency matches the first target value; performing frequency conversion using the conversion signal based on the received signal; Further comprising a receiving unit that generates a first intermediate frequency signal whose intermediate frequency is the target frequency,
The demodulator generates the second intermediate frequency signal by frequency-converting the target signal or the first intermediate frequency signal using the first reference signal, and demodulates the second intermediate frequency signal. to generate the demodulated signal,
The deviation detector detects a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal when the demodulator generates the demodulated signal based on the target signal. , when the demodulator generates the demodulated signal based on the first intermediate frequency signal, detecting a frequency deviation between the first reference signal and the target signal based on the demodulated signal;
The error correction unit corrects a frequency error of the first reference signal with respect to the target signal according to the frequency deviation between the first reference signal and the target signal, and corrects the first reference signal and the second reference signal. A frequency error of the second reference signal with respect to the second target value is corrected according to a deviation of the frequency deviation from the signal from the target deviation.

Preferably, the error correction section corrects the frequency error of the first reference signal with respect to the target signal according to a frequency compensation amount for reducing the frequency deviation between the first reference signal and the target signal.

Preferably, the error correction section corrects the frequency error of the second reference signal with respect to the second target value according to the deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation. After correction, the frequency error of the second reference signal with respect to the second target value is corrected according to the frequency compensation amount.

A frequency error correction method according to a second aspect of the present invention includes:
A first oscillator that outputs a first reference signal whose first target value is a target frequency; and at least one oscillator that outputs a second reference signal whose second target value is a target frequency by adding a target deviation to the first target value A frequency error correction method performed by a radio station comprising two second oscillators,
generating a target signal whose first intermediate frequency is a target frequency based on the second reference signal;
frequency-converting the target signal using the first reference signal to generate a second intermediate frequency signal whose frequency is a second intermediate frequency lower than the first intermediate frequency; By demodulating, a demodulated signal is generated,
detecting a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal;
A frequency error of the second reference signal with respect to the second target value is corrected according to a deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation.

A radio station according to the present invention includes a first oscillator that outputs a first reference signal whose first target value is a target frequency; and at least one second oscillator for outputting a reference signal. The radio station determines a second target according to the deviation from the target deviation of the frequency deviation between the first reference signal and the second reference signal detected based on the demodulated signal generated from the target signal based on the second reference signal. Correct the frequency error of the second reference signal with respect to the value. This makes it possible to suppress variation in frequency accuracy of each oscillator in a radio station having a plurality of oscillators.

FIG. 1 is a block diagram showing the configuration of a radio station according to Embodiment 1 of the present invention; Flowchart showing an example of operation of the frequency error correction method performed by the radio station according to Embodiment 1 Flowchart showing an example of operation of the frequency error correction method performed by the radio station according to Embodiment 1 Block diagram showing the configuration of a radio station according to Embodiment 2 of the present invention Flowchart showing an example of operation of a frequency error correction method performed by a radio station according to Embodiment 2 FIG. 3 is a block diagram showing the configuration of a modification of the radio station according to the embodiment of the present invention; Flowchart showing a modification of the operation of the frequency error correction method performed by the radio station according to the embodiment

Hereinafter, a radio station and a frequency error correction method according to embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are given to the same or equivalent parts.

(Embodiment 1)
The radio station 1 according to Embodiment 1 will be described using a double superheterodyne radio station as an example. The radio station 1 shown in FIG. 1 includes a first oscillator 11 that outputs a first reference signal whose first target value is the target frequency, and a second target value that is the first target value plus the target deviation. at least one second oscillator 12 for outputting a second reference signal. In Embodiment 1, radio station 1 includes one first oscillator 11 and one second oscillator 12 .

In the reception mode, the radio station 1 uses the first reference signal to perform reception processing for receiving signals from other radio stations. Furthermore, in the transmission mode, the radio station 1 performs transmission processing for transmitting signals to other radio stations using the second reference signal. The radio station 1 corrects the frequency error of the second oscillator 12 in accordance with the frequency error of the first oscillator 11 in the error correction mode. Specifically, in the error correction mode, the radio station 1 performs frequency conversion using the first reference signal based on the target signal that is generated using the second reference signal and whose first intermediate frequency is the target frequency. A second intermediate frequency signal is generated, and a frequency deviation between the first reference signal and the second reference signal is detected from a demodulated signal obtained by demodulating the second intermediate frequency signal. Then, the radio station 1 corrects the frequency error of the second reference signal with respect to the second target value according to the frequency deviation and the target deviation.

In order to suppress the deterioration of the frequency accuracy of each oscillator of the radio station 1, specifically, the frequency accuracy of the first oscillator 11 and the second oscillator 12, when correcting the frequency error of the second reference signal, It is preferable to correct the frequency error of the first reference signal. As an example of processing for correcting the frequency error of the first reference signal, the radio station 1 receives a signal generated by performing modulation based on the target signal whose frequency is the first target value in the reception mode, The frequency error of the first reference signal with respect to the first target value may be corrected based on the received signal. In Embodiment 1, the radio station 1 receives a signal generated by performing modulation based on the target signal from a base station, which is an example of another radio station having a reference oscillator that outputs the target signal, A frequency error of the first reference signal with respect to the first target value is corrected based on the received signal.

Each part of the radio station 1 will be described below, taking as an example a case where frequency modulation, specifically, FSK (Frequency Shift Keying) is used as a modulation method. The radio station 1 includes an input unit 21 for receiving input of data, an input signal processing unit 22 for performing signal processing on the data input by the input unit 21 to generate transmission data, and a signal processing unit 22 for correcting a frequency error. A data output unit 23 that outputs conversion data for generating correction data and a non-modulated signal used for frequency conversion, and a symbol mapper 24 that maps transmission data or correction data to multilevel FSK symbols. , provided.

The radio station 1 further includes an oscillator switch 25 connected to the first oscillator 11 and the second oscillator 12 and outputting the first reference signal or the second reference signal, and a second reference signal output by the oscillator switch 25. and a signal generation unit 26 that generates a conversion signal that is a non-modulated signal according to the target signal or the modulated signal for transmission, or the first reference signal output by the oscillator switch 25 . The radio station 1 further includes a signal switcher 27 that outputs the target signal, the modulated signal for transmission, or the signal for conversion acquired from the signal generator 26, and generates a transmission signal from the modulated transmission signal output by the signal switcher 27. and a transmitting unit 28 for transmitting the data. A transmission signal generated by the transmission section 28 is transmitted to any other wireless station via the transmission/reception switching section 29 and the antenna 30 .

The radio station 1 further includes a receiving section 31 that generates a first intermediate frequency signal from the received signal received by the antenna 30 and supplied via the transmission/reception switching section 29, and a target signal or receiving section that is output from the signal switching device 27. and a signal switcher 32 for outputting the first intermediate frequency signal generated in 31 . Based on the target signal or the first intermediate frequency signal output from the signal switcher 32, the radio station 1 further converts the frequency using the first reference signal to generate a second intermediate frequency signal, is provided to generate a demodulated signal. The radio station 1 further includes a deviation detector 34 for detecting the frequency deviation between the first reference signal and the target signal and the frequency deviation between the first reference signal and the second reference signal based on the demodulated signal, and and an error correction unit 35 for correcting the frequency error of the first oscillator 11 and the second oscillator 12 .

The radio station 1 further includes an output signal processing section 36 for extracting output data from the demodulated signal, and an output section 37 for outputting the output data.

The radio station 1 is provided with a controller 50 to control the above components. The controller 50 includes a CPU (Central Processing Unit) 51 , I/O (Input/Output) 52 , RAM (Random Access Memory) 53 , and ROM (Read-Only Memory) 54 . To avoid complication and facilitate understanding, signal lines from the controller 50 to each part of the radio station 1 have been omitted. The controller 50 is connected to each section of the radio station 1 via an I/O 52, and controls the start and end of processing of each section and the content of the processing. The CPU 51 executes control programs stored in the ROM 54 to control the radio station 1 . Commands, data, etc. input via the I/O 52 are processed and temporarily stored in the RAM 53 . The CPU 51 reads commands, data, etc., stored in the RAM 53 as necessary, and controls the radio station 1 .

Details of each part of the radio station 1 having the above configuration will be described below. The first oscillator 11 has a crystal oscillator and an oscillation circuit, and outputs a first reference signal. In the first embodiment, the first reference signal is a sinusoidal clock signal. The first target value f1, which is the target frequency of the first reference signal, is, for example, 50.40 MHz. The second oscillator 12 has a crystal oscillator and an oscillation circuit, and outputs a second reference signal. In the first embodiment, the second reference signal is a sinusoidal clock signal.

The input unit 21 has a microphone that captures voice and generates an analog voice signal, a low-frequency amplifier that amplifies the amplitude of the analog voice signal, and the like.

The input signal processing unit 22 converts the amplified analog audio signal from AD (Analog-to-Digital), compresses and encodes it, adds a synchronization word, a header, etc., and generates data for transmission. A sync word is a known bit data sequence.

The data output unit 23 outputs correction data used when correcting the frequency error to the symbol mapper 24 . In Embodiment 1, the correction data is fixed data including a synchronization word. The synchronization word included in the correction data is the same as the synchronization word included in the transmission data. The data output unit 23 outputs conversion data used for generating non-modulated signals used for frequency conversion to the signal generation unit 26 . Conversion data is, for example, data in which 0s are consecutive.

The symbol mapper 24 maps the transmission data generated by the input signal processing unit 22 or the correction data generated by the data output unit 23 to symbols, and outputs modulation data indicating the mapped symbols. For example, if radio station 1 performs quaternary FSK, symbol mapper 24 assigns 2-bit data 00 a symbol of +1, 2-bit data 01 a symbol of −1, and 2-bit data 10 a symbol of +3. , and the -3 symbol is assigned to the 2-bit data 11 . A frequency shift amount is determined for each symbol.

The oscillator switcher 25 outputs the first reference signal obtained from the first oscillator 11 in the reception mode, and outputs the second reference signal obtained from the second oscillator 12 in the transmission mode or the error correction mode.

The signal generator 26 performs frequency modulation based on the input target data and the second reference signal output by the oscillator switch 25 to generate a target signal that is a modulated signal, or the oscillator switch 25 A conversion signal, which is a non-modulated signal, is generated based on the output first reference signal. Target data used to generate the target signal is modulation data input from the symbol mapper 24 .

Specifically, the signal generator 26 includes a phase comparator 38 that outputs a phase difference signal based on the first reference signal and a signal divided by a frequency divider 41 described later, and a phase comparator 38 that converts the phase difference signal into a voltage. a VCO (Voltage Controlled Oscillator) 40 that oscillates at an oscillation frequency corresponding to the control voltage; and a frequency divider 41 that rotates.

The phase comparator 38 outputs a phase difference between the first reference signal or the second reference signal output from the oscillator switch 25 and the signal output from the VCO 40 and divided by the frequency divider 41. Output a signal.

The loop filter 39 converts the phase difference signal output by the phase comparator 38 into a current, integrates and smoothes the current to convert it into a voltage, and outputs this voltage to the VCO 40 as a control voltage.

In the reception mode, the VCO 40 generates and outputs a conversion signal S1, which is an unmodulated signal whose frequency is lower than the reception frequency by the first intermediate frequency, based on the first reference signal. For example, in the reception mode, the VCO 40 generates a signal obtained by superimposing conversion data output from the data output section 23 on a carrier signal whose frequency is lower than the reception frequency by the first intermediate frequency and indicating that the amount of frequency deviation is 0. is generated as a conversion signal S1. The reception frequency is, for example, a frequency included in the range of 360 MHz or more and 400 MHz or less. The first intermediate frequency is, for example, 49.95 MHz.

In the transmission mode, the VCO 40 generates a transmission modulated signal S2, which is a modulated signal in which modulation data based on transmission data is superimposed on a carrier wave signal whose frequency is the transmission frequency based on the second reference signal, and outputs the modulated signal. do. The transmission frequency is, for example, a frequency included in the range of 360 MHz or more and 400 MHz or less.

In the error correction mode, the VCO 40 generates and outputs a target signal S3 in which modulation data based on correction data is superimposed on a carrier wave signal whose frequency is the first intermediate frequency based on the second reference signal.

The signal switcher 27 sends the conversion signal S1, which is a non-modulated signal output from the VCO 40, to the receiver 31 in the reception mode. The signal switcher 27 sends the modulated signal for transmission S2 output from the VCO 40 to the transmitter 28 in the transmission mode. The signal switcher 27 sends the target signal S3 output from the VCO 40 to the signal switcher 32 in the error correction mode.

The transmission unit 28 amplifies the modulated signal for transmission to a desired level suitable for transmission, reduces unnecessary signals such as harmonics, generates a transmission signal, and transmits the signal via the transmission/reception switching unit 29 and the antenna 30. Send the signal to another radio station.

The receiving unit 31 includes an amplifier 42 that amplifies a received signal received by the antenna 30 and supplied via the transmission/reception switching unit 29, a mixer 43 that generates a first intermediate frequency signal from the received signal output by the amplifier 42, Prepare.

The amplifier 42 has, for example, an LNA (Low Noise Amplifier) and amplifies the received signal. The mixer 43 multiplies the conversion signal S1 output from the signal switcher 27 and the received signal amplified by the amplifier 42 to generate and output a first intermediate frequency signal having a frequency of the first intermediate frequency.

In the receive mode, the signal switcher 32 sends the first intermediate frequency signal acquired from the mixer 43 of the receiver 31 to the demodulator 33 . In the error correction mode, the signal switcher 32 sends the target signal S3 acquired from the VCO 40 via the signal switcher 27 to the demodulator 33 .

The demodulator 33 multiplies the first reference signal by the output of the signal switcher 32 to generate a second intermediate frequency signal whose frequency is a second intermediate frequency lower than the first intermediate frequency; An AD converter 45 that generates digital data from an intermediate frequency signal, and an FM (Frequency Modulation) detector that performs demodulation processing on the digital data generated by the AD converter 45 to generate a demodulated signal. 46 and.

In receive mode, the mixer 44 outputs a second intermediate frequency signal whose frequency is the difference between the frequency of the first reference signal and the first intermediate frequency signal. When the first target value f1, which is the target frequency of the first reference signal, is 50.40 MHz and the first intermediate frequency is 49.95 MHz, the mixer 44 operates at a value obtained by subtracting 49.95 MHz from 50.40 MHz. Output a second intermediate frequency signal of 0.45 MHz.

In the error correction mode, the mixer 44 outputs a second intermediate frequency signal whose frequency is the difference between the frequency of the first reference signal and the frequency of the target signal S3.

The AD converter 45 AD-converts the second intermediate frequency signal to generate digital data and sends the digital data to the FM detector 46 .

The FM detector 46 determines to which of four predetermined amplitude levels the value of each data acquired from the AD converter 45 corresponds, and outputs 2-bit data associated with the determined amplitude level. Specifically, any one of 00, 01, 10 and 11 is output as a demodulated signal.

The deviation detector 34 detects a synchronous word contained in the demodulated signal, and a synchronous word detector 47 detects the frequency deviation between the first reference signal and the target signal and the frequency deviation between the first reference signal and the second reference signal based on the synchronous word. and a deviation calculator 48 that detects the frequency deviation from the

The synchronization word detector 47 repeats the correlation calculation between the demodulated signal and the synchronization word by shifting one symbol, in other words, by two bits. As a result of the correlation calculation, if the correlation value is equal to or greater than the threshold, it can be considered that the synchronization word has been detected.

A deviation calculator 48 calculates a frequency deviation from a DC (Direct Current) offset included in the symbol corresponding to the detected synchronization word. The deviation calculator 48 preferably outputs the moving average value of the frequency deviation as the frequency deviation.

When the radio station 1 is in the receive mode and the first oscillator 11 has a frequency error, specifically, when the frequency of the first reference signal deviates from the first target value, the mixer 43 outputs The frequency of the first intermediate frequency signal deviates from the target value of the first intermediate frequency. As a result, the frequency of the second intermediate frequency signal that is the output of the mixer 44 deviates from the second intermediate frequency that is the target value. The deviation calculator 48 calculates the frequency deviation of the second intermediate frequency signal, in other words, the frequency deviation between the first reference signal and the target signal, from the demodulated signal based on the second intermediate frequency signal, and calculates the calculated frequency deviation. It is sent to the error corrector 35 .

When the radio station 1 is in the error correction mode and the second oscillator 12 has a frequency error, specifically, the difference between the frequency of the first reference signal and the frequency of the second reference signal is different from the target deviation. In this case, the center frequency of the target signal S3 deviates from the target value of the first intermediate frequency. As a result, the center frequency of the frequency of the second intermediate frequency signal, which is the output of the mixer 44, deviates from the second intermediate frequency, which is the target value. The deviation calculator 48 calculates the deviation of the center frequency of the second intermediate frequency signal, in other words, the frequency deviation between the frequency of the first reference signal and the frequency of the second reference signal, from the demodulated signal based on the second intermediate frequency signal. Then, the calculated frequency deviation is sent to the error corrector 35 .

The error correction section 35 corrects the frequency error of the first reference signal and the second reference signal according to the frequency deviation detected by the deviation detection section 34 . Specifically, the error correction unit 35 adjusts the frequency of the first reference signal by controlling the first oscillator 11 so as to reduce the frequency deviation between the first reference signal and the target signal. Furthermore, the error correction unit 35 controls the second oscillator 12 so that the frequency deviation between the first reference signal and the second reference signal output by the first oscillator 11 whose frequency error has been corrected approaches the target deviation. Adjust the frequency of the reference signal.

The output signal processing unit 36 extracts audio data from the demodulated signal synchronized with the synchronization word detected by the synchronization word detection unit 47 of the deviation detection unit 34, and converts it to DA (Digital-to-Analog). to generate an analog audio signal and send it to the output unit 37 .

The output unit 37 has a low-frequency amplifier that amplifies an analog audio signal, and a speaker that outputs the analog audio signal amplified by the low-frequency amplifier.

The frequency error correction processing performed by the radio station 1 having the above configuration will be described below. When the radio station 1 is activated, it enters a reception mode, and starts the frequency error correction processing of the first reference signal shown in FIG.

Based on the first reference signal obtained from the first oscillator 11 via the oscillator switch 25, the signal generator 26 generates the conversion signal S1, which is an unmodulated signal whose frequency is lower than the reception frequency by the first intermediate frequency. and output (step S11). The signal switcher 27 sends the conversion signal S1 generated in step S11 to the mixer 43 included in the receiver 31 .

The mixer 43 multiplies the signal received from the base station, which is received by the antenna 30, supplied via the transmission/reception switching unit 29, and amplified by the amplifier 42, by the conversion signal S1 to generate a first intermediate frequency signal. , is output (step S12).

The mixer 44 provided in the demodulator 33 multiplies the first reference signal by the first intermediate frequency signal generated in step S12 supplied via the signal switcher 32 to generate a second intermediate frequency signal, and outputs the second intermediate frequency signal. (step S13).

The FM detection unit 46 included in the demodulation unit 33 performs demodulation processing on digital data generated by AD-converting the second intermediate frequency signal generated in step S13 by the AD converter 45, and performs demodulation. A signal is generated (step S14).

The deviation detector 34 detects the frequency deviation of the second intermediate frequency signal, in other words, the frequency deviation between the first reference signal and the target signal, based on the synchronization word included in the demodulated signal generated in step S14. , the detected frequency deviation is sent to the error corrector 35 (step S15).

The error correction unit 35 corrects the frequency error of the first reference signal output by the first oscillator 11 according to the frequency deviation detected in step S15 (step S16). For example, the error correction unit 35 corrects the frequency error of the first reference signal with respect to the target signal according to the frequency compensation amount for reducing the frequency deviation between the first reference signal and the target signal. When the process of step S16 is completed, the radio station 1 ends the process of correcting the frequency error of the first reference signal. After that, the radio station 1 repeats the process of correcting the frequency error of the first reference signal shown in FIG. 2 at predetermined time intervals. As a result, the frequency of the first reference signal output by the first oscillator 11 provided in the radio station 1 can be made to follow the reference oscillator provided in the base station and outputting the target signal.

After the frequency error of the first reference signal is corrected by the above-described processing, for example, when the wireless station 1 enters the error correction mode by operating an operation unit (not shown) of the wireless station 1, the wireless station 1 3 is started to correct the frequency error of the second reference signal.

In the error correction mode, the signal generator 26 converts the carrier wave signal having the first intermediate frequency based on the second reference signal obtained from the second oscillator 12 via the oscillator switch 25 to the correction data. A target signal S3, which is a modulated signal on which modulation data is superimposed, is generated and output (step S21). The signal switcher 27 sends the target signal S3 generated in step S21 to the signal switcher 32 . The signal switcher 32 receives the target signal S3 generated in step S21 from the signal switcher 27 and sends the target signal S3 to the demodulator 33 .

The mixer 44 included in the demodulation unit 33 multiplies the first reference signal by the target signal S3 generated in step S21 supplied via the signal switches 27 and 32 to generate a second intermediate frequency signal, and outputs the second intermediate frequency signal. (step S22).

The FM detection unit 46 included in the demodulation unit 33 performs demodulation processing on digital data generated by AD-converting the second intermediate frequency signal generated in step S22 by the AD converter 45, and performs demodulation. A signal is generated (step S23).

The deviation detector 34 detects the frequency deviation of the second intermediate frequency signal, in other words, the frequency deviation between the first reference signal and the second reference signal, based on the synchronization word included in the demodulated signal, and detects the detected frequency. The deviation is sent to the error corrector 35 (step S24).

The error correction unit 35 corrects the frequency error of the second reference signal output by the second oscillator 12 according to the deviation of the frequency deviation detected in step S24 from the target deviation (step S25). For example, the error corrector 35 corrects the frequency error of the second reference signal with respect to the second target value so that the frequency deviation between the first reference signal and the second reference signal approaches the target deviation. When the process of step S25 is completed, the radio station 1 ends the process of correcting the frequency error of the second reference signal. After that, the radio station 1 repeats the process of correcting the frequency error of the second reference signal shown in FIG. 3 at predetermined time intervals. As a result, the frequency of the second reference signal output by the second oscillator 12 included in the radio station 1 can follow the frequency of the first reference signal output by the first oscillator 11 .

As described above, the radio station 1 according to Embodiment 1 detects the frequency deviation between the first reference signal and the second reference signal based on the demodulated signal generated from the target signal S3 based on the second reference signal. The frequency error of the second reference signal with respect to the second target value is corrected according to the deviation from the target deviation of . As a result, the frequency of the second reference signal output by the second oscillator 12 can be made to follow the frequency of the first reference signal output by the first oscillator 11, and variations in frequency accuracy of each oscillator in the radio station 1 can be reduced. Suppressed.

According to the radio station 1, since the frequency error of the second reference signal output by the second oscillator 12 is corrected in accordance with the first reference signal output by the first oscillator 11, when a signal cannot be received from another radio station, Even so, it is possible to suppress variation in frequency accuracy of each oscillator in the radio station 1 .

Furthermore, by correcting the frequency error of the first reference signal according to the frequency deviation between the first reference signal and the target signal detected based on the demodulated signal generated from the received signal, the first oscillator 11 outputs The frequency of the first reference signal can follow the frequency of the target signal output by the reference oscillator provided in another radio station. As a result, it becomes possible to suppress the deterioration of the frequency accuracy of each oscillator in the radio station 1 . By performing the frequency error correction process as described above, it is possible to correct the frequency error of each oscillator in the radio station 1 including a plurality of oscillators, specifically the first oscillator 11 and the second oscillator 12. .

According to the radio station 1, in both the process of correcting the frequency error of the first reference signal and the process of correcting the frequency error of the second reference signal, the deviation is detected based on the synchronization word detected by the synchronization word detector 47. The frequency deviation calculated by the calculator 48 is used. Therefore, there is no need to provide a circuit for detecting the frequency deviation separately for correcting the frequency error of the first reference signal and the second reference signal, and complication of the structure of the radio station 1 is suppressed.

(Embodiment 2)
The method of correcting the frequency error of the second reference signal with respect to the second target value is not limited to the above example. A radio station 2 that corrects the frequency error of the second reference signal using a target signal that is a non-modulated signal will be described in a second embodiment, focusing on differences from the radio station 1 according to the first embodiment.

The radio station 2 according to Embodiment 2 shown in FIG. 4 has the same configuration as the radio station 1, but the data output unit 23 outputs only conversion data, and the signal generation unit 26 outputs non-modulated signals. It differs from the radio station 1 in that it generates a signal S4.

The data output unit 23 outputs conversion data used for generating non-modulated signals used for frequency conversion to the signal generation unit 26 . Conversion data is, for example, data in which 0s are consecutive.

The signal generator 26 generates a conversion signal S1, which is a non-modulated signal, based on the first reference signal output by the oscillator switch 25, and generates a non-modulated signal S1 based on the second reference signal output by the oscillator switch 25. to generate the target signal S4.

Specifically, in the receive mode, VCO 40 generates and outputs conversion signal S1 based on the first reference signal, as in the first embodiment. In the transmission mode, VCO 40 generates and outputs transmission modulated signal S2 based on the second reference signal, as in the first embodiment. In the error correction mode, the VCO 40 generates and outputs the target signal S4, which is an unmodulated signal whose frequency is the first intermediate frequency, based on the second reference signal. Specifically, in the error correction mode, the VCO 40 superimposes the conversion data output from the data output unit 23 on the carrier wave signal whose frequency is the first intermediate frequency and indicates that the frequency deviation amount is 0. A target signal S4, which is a signal, is generated.

The signal switcher 27 sends the conversion signal S1 output from the VCO 40 to the receiver 31 in the reception mode. The signal switcher 27 sends the modulated signal for transmission S2 output from the VCO 40 to the transmitter 28 in the transmission mode. The signal switcher 27 sends the target signal S4 output from the VCO 40 to the signal switcher 32 in the error correction mode.

In the receive mode, the signal switcher 32 sends the first intermediate frequency signal acquired from the mixer 43 of the receiver 31 to the demodulator 33 . In the error correction mode, the signal switcher 32 sends the target signal S4 acquired from the VCO 40 to the demodulator 33 via the signal switcher 27 .

In receive mode, the mixer 44 outputs a second intermediate frequency signal whose frequency is the difference between the frequency of the first reference signal and the first intermediate frequency signal. In the error correction mode, the mixer 44 outputs a second intermediate frequency signal whose frequency is the difference between the frequency of the first reference signal and the frequency of the target signal S4.

The FM detector 46 outputs the demodulated signal to the sync word detector 47 and deviation calculator 48 . In the error correction mode, the deviation calculator 48 calculates the frequency deviation from the DC offset of the demodulated signal. The deviation calculator 48 preferably outputs the moving average value of the frequency deviation as the frequency deviation.

When the radio station 2 is in the error correction mode and the second oscillator 12 has a frequency error, specifically, the difference between the frequency of the first reference signal and the frequency of the second reference signal is different from the target deviation. In this case, the center frequency of the target signal S4 deviates from the target value of the first intermediate frequency. As a result, the center frequency of the frequency of the second intermediate frequency signal, which is the output of the mixer 44, deviates from the second intermediate frequency, which is the target value. The deviation calculator 48 calculates the deviation of the center frequency of the second intermediate frequency signal, in other words, the frequency deviation between the frequency of the first reference signal and the frequency of the second reference signal, from the demodulated signal based on the second intermediate frequency signal. Then, the calculated frequency deviation is sent to the error corrector 35 .

Frequency error correction processing performed by the radio station 2 having the above configuration will be described below. The frequency error correction processing of the first reference signal in the receive mode is the same as in the first embodiment. After the frequency error of the first reference signal is corrected, for example, when the operation unit (not shown) of the radio station 2 is operated to switch the radio station 2 to the error correction mode, the radio station 2 is operated as shown in FIG. 2 Start the frequency error correction process for the reference signal.

In the error correction mode, the VCO 40 generates the target signal S4, which is an unmodulated signal whose frequency is the first intermediate frequency, based on the second reference signal (step S31). The signal switcher 27 sends the target signal S4 generated in step S31 to the signal switcher 32 . The signal switcher 32 receives the target signal S4 generated in step S31 from the signal switcher 27 and sends the target signal S4 to the demodulator 33 .

The mixer 44 included in the demodulator 33 multiplies the first reference signal by the target signal S4 generated in step S31 supplied via the signal switches 27 and 32 to generate a second intermediate frequency signal, and outputs the signal. (step S32). The processing from steps S23 to S25 performed after the processing of step S32 is completed is the same as the processing from steps S23 to S25 in FIG.

When the process of step S25 is completed, the radio station 2 ends the process of correcting the frequency error of the second reference signal. After that, the radio station 2 repeats the process of correcting the frequency error of the second reference signal shown in FIG. 5 at predetermined time intervals. As a result, the frequency of the second reference signal output by the second oscillator 12 included in the radio station 2 can follow the frequency of the first reference signal output by the first oscillator 11 .

As described above, the radio station 2 according to Embodiment 2 detects the frequency deviation between the first reference signal and the second reference signal based on the demodulated signal generated from the target signal S4 based on the second reference signal. The frequency error of the second reference signal with respect to the second target value is corrected according to the deviation from the target deviation of . As a result, the frequency of the second reference signal output by the second oscillator 12 can be made to follow the frequency of the first reference signal output by the first oscillator 11, and variations in frequency accuracy of each oscillator in the radio station 2 can be reduced. Suppressed.

In the process of correcting the frequency error of the second reference signal, the radio station 2 calculates the frequency deviation between the first reference signal and the second reference signal based on the demodulated signal output by the FM detector 46. There is no need to wait for the completion of the detection process of Therefore, the radio station 2 can quickly perform the frequency deviation calculation process.

The present invention is not limited to the examples of embodiments described above. The number of second oscillators provided in the radio stations 1 and 2 is arbitrary. As an example, the radio station 3 shown in FIG. 6 comprises two second oscillators 12,49. When the radio station 2 is in the error correction mode and corrects the frequency error of the second oscillator 49, the VCO 40 generates a carrier wave signal having a first intermediate frequency based on the second reference signal output by the second oscillator 49. Then, the target signal S3 superimposed with the modulation data based on the correction data is generated and output.

The method of correcting the frequency error of the first reference signal is not limited to the above example. As an example, the radio station 1-3 determines the frequency error of the first reference signal based on the received signal received from another radio station that communicates with the base station and whose oscillator frequency error has been corrected. may be corrected. As another example, the radio station 1-3 includes a frequency counter that is calibrated according to an externally supplied signal, such as a PPS (Pulse Per Second) signal. The frequency error of the first reference signal may be corrected according to the frequency of .

Immediately after the radio station 1-3 is activated, for example, after correcting the frequency error of the first reference signal as shown in FIG. 2, and then correcting the frequency error of the second reference signal as shown in FIG. As shown in FIG. 7, the frequency error of the first reference signal and the frequency error of the second reference signal may be corrected according to the frequency deviation between the first reference signal and the target signal.

The processing from steps S11 to S16 shown in FIG. 7 is the same as the processing shown in FIG. After step S16, the error correction unit 35 corrects the frequency error of the second reference signal output by the second oscillator 12 according to the frequency deviation detected in step S15 (step S17). For example, the error correction unit 35 causes the second oscillator 12 to output an amount of frequency compensation that reduces the frequency deviation between the first reference signal used to correct the frequency error of the first reference signal in step S16 and the target signal. corrects the frequency error of the second reference signal. In other words, the amount of adjustment of the frequency of the first reference signal and the amount of adjustment of the frequency of the second reference signal are the same. By correcting the frequency error between the first reference signal and the second reference signal according to the frequency deviation between the first reference signal and the target signal as shown in FIG. 7, the frequency error can be corrected in a shorter time. It becomes possible.

In the above-described embodiment, the VCO 40 oscillates over a frequency band including a transmission frequency and a reception frequency, such as a range of 360 MHz or more and 400 MHz or less, to an intermediate frequency band, such as 49.95 MHz. Although possible, the radio station 1-3 may comprise a VCO capable of oscillating in the working frequency band and a VCO capable of oscillating in the intermediate frequency band.

The target deviation, which is the target value of the frequency deviation between the first reference signal and the second reference signal, is arbitrary. In the radio station 2, the target deviation between the first reference signal and the second reference signal output by the second oscillator 12 and the target deviation between the first reference signal and the second reference signal output by the second oscillator 49 may be the same. may be different.

In radio station 1-3, input signal processing section 22, data output section 23, symbol mapper 24, error correction section 35, output signal processing section 36, FM detection section 46, synchronization word detection section 47, and deviation calculation section 48 are provided. realized by a DSP (Digital Signal Processor), the signal generator 26 is realized by a PLL IC (Integrated circuit) with a built-in VCO, and the mixer 44 and the AD converter 45 are realized by an IF (Intermediate Frequency). ) may be realized by a detection IC.

The modulation method of the radio station 1-3 is not limited to 4-level FSK, and any method can be used as long as the frequency deviation can be detected from the demodulated signal. As an example, the radio station 1-3 may perform binary FSK, or may perform multi-level FSK other than 4-level FSK. As another example, the radio station 1-3 may perform PSK (Phase Shift Keying), such as π/4DQPSK (Differential Quadrature Phase Shift Keying). , QAM (Quadrature Amplitude Modulation).

In addition, the hardware configuration and flowcharts described above are examples, and can be arbitrarily changed and modified.

1, 2, 3 radio station
11 first oscillator
12 second oscillator
21 input section
22 input signal processor
23 data output unit
24 symbol mapper
25 oscillator switch
26 signal generator 27, 32 signal switch
28 transmitter
29 transmission/reception switching unit
30 Antenna
31 receiver
33 Demodulator
34 deviation detector
35 error correction unit
36 Output signal processor
37 Output section
38 phase comparator
39 loop filter
40 VCOs
41 frequency divider
42 amplifier 43, 44 mixer
45 AD converter
46 FM detector
47 sync word detector
48 deviation calculator
49 second oscillator
50 controller
51 CPUs
52 I/O
53 RAM
54 ROMs
S1 conversion signal
S2 Modulated signal for transmission S3, S4 Target signal

Claims (7)

a first oscillator that outputs a first reference signal whose first target value is the target frequency;
at least one second oscillator for outputting a second reference signal having a target frequency as a second target value obtained by adding a target deviation to the first target value;
a signal generator that generates a target signal having a target frequency at a first intermediate frequency based on the second reference signal;
frequency-converting the target signal using the first reference signal to generate a second intermediate frequency signal whose frequency is a second intermediate frequency lower than the first intermediate frequency; a demodulator that generates a demodulated signal by demodulating;
a deviation detector that detects a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal;
an error correction unit that corrects the frequency error of the second reference signal with respect to the second target value according to the deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation;
A radio station with The signal generation unit generates the target signal, which is a modulated signal, by performing modulation based on input target data and the second reference signal.
A radio station according to claim 1. The signal generator generates the target signal, which is a non-modulated signal based on the second reference signal.
A radio station according to claim 1. The signal generator generates a conversion signal that is a non-modulated signal based on the first reference signal,
receiving a signal generated by performing modulation based on a target signal whose frequency matches the first target value; performing frequency conversion using the conversion signal based on the received signal; Further comprising a receiving unit that generates a first intermediate frequency signal whose intermediate frequency is the target frequency,
The demodulator generates the second intermediate frequency signal by frequency-converting the target signal or the first intermediate frequency signal using the first reference signal, and demodulates the second intermediate frequency signal. to generate the demodulated signal,
The deviation detector detects a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal when the demodulator generates the demodulated signal based on the target signal. , when the demodulator generates the demodulated signal based on the first intermediate frequency signal, detecting a frequency deviation between the first reference signal and the target signal based on the demodulated signal;
The error correction unit corrects a frequency error of the first reference signal with respect to the target signal according to the frequency deviation between the first reference signal and the target signal, and corrects the first reference signal and the second reference signal. correcting the frequency error of the second reference signal with respect to the second target value according to the deviation from the target deviation of the frequency deviation from the signal;
A radio station according to any one of claims 1 to 3. The error correction unit corrects the frequency error of the first reference signal with respect to the target signal according to a frequency compensation amount that reduces the frequency deviation between the first reference signal and the target signal.
A radio station according to claim 4. After correcting the frequency error of the second reference signal with respect to the second target value according to the deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation, corrects the frequency error of the second reference signal with respect to the second target value according to the frequency compensation amount;
A radio station according to claim 5 . A first oscillator that outputs a first reference signal whose first target value is a target frequency; and at least one oscillator that outputs a second reference signal whose second target value is a target frequency by adding a target deviation to the first target value A frequency error correction method performed by a radio station comprising two second oscillators,
generating a target signal whose first intermediate frequency is a target frequency based on the second reference signal;
frequency-converting the target signal using the first reference signal to generate a second intermediate frequency signal whose frequency is a second intermediate frequency lower than the first intermediate frequency; By demodulating, a demodulated signal is generated,
detecting a frequency deviation between the first reference signal and the second reference signal based on the demodulated signal;
correcting the frequency error of the second reference signal with respect to the second target value according to the deviation of the frequency deviation between the first reference signal and the second reference signal from the target deviation;
Frequency error correction method.

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