JP2013074391A - Transmitter receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve precision of a transmission frequency of a single-wave simplex type transmitting-receiving circuit of a transmitter receiver including a single-wave simplex type transmitting-receiving circuit in addition to a first receiving circuit exclusively for base station.SOLUTION: The transmitter receiver is provided with a first frequency measurement unit which measures the frequency of a signal received by the first receiving circuit, and a second frequency measurement unit which measures the frequency of a signal received by a second receiving circuit of the transmitting-receiving circuit, also provided with a frequency error detection unit which detects an error of the frequency measured by the second frequency measurement unit on the basis of the frequency measured by the first frequency measurement unit, and further provided with a frequency control unit which receives a transmission signal by the second receiving circuit and controls the oscillation frequency of a voltage-controlled oscillator as a reference clock so as to reduce the error detected by the frequency error detection unit when performing transmission by the transmitting-receiving circuit.

Description

  The present invention relates to a transceiver used for wireless communication with a base station such as a fire fighting radio. More specifically, the present invention relates to a transmitter / receiver that compensates for a change in transmission frequency at the time of transmission due to a change in oscillation frequency due to a temperature change or a change with time of a local oscillator provided in the transmitter / receiver.

  The business-use narrowband digital radio communication system uses the standard ARIB STD-T61 as an internal reference clock for generating an oscillation signal used for transmission / reception in a mobile station based on a stable frequency signal transmitted from a base station. It is said that the frequency may be controlled. A conventional example of this control will be described below.

FIG. 6 is a block diagram showing the transceiver of the first conventional example (Patent Document 1).
6 includes a radio circuit unit 101, a logic circuit unit 102, an antenna 110, and an operation unit 146. The radio circuit unit 101 is connected to a reception circuit and a transmission circuit via an antenna duplexer 111. .

The reception circuit amplifies the reception signal from the antenna duplexer 111 in the wireless circuit unit 101 by the amplifier 112, and down-converts the frequency of the reception signal twice by the first mixer 113 and the second mixer 116. Then, the demodulator 120 that demodulates the received signal through the amplifier 119, and the signal processing by the received signal processor 143 through the A / D converter 133 in the logic circuit unit 102, outputs an audio signal.
The transmission circuit performs digital processing on the audio signal input by the transmission signal processing unit 142 in the logic circuit unit 102, converts it to an analog signal by the D / A converter 130, and then uses the modulation unit 121 in the wireless circuit unit 101. The modulated signal is amplified by the amplifier 122, the frequency of the transmission signal is up-converted twice by the second mixer 123 and the first mixer 125, sent to the antenna duplexer 111 via the amplifier 127 which is a transmission amplifier, and transmitted from the antenna 110. Is done.

A control unit 144 is provided in the logic circuit 102, and the received signal processing unit 143 detects frequency information transmitted from the base station and supplies the signal to the control unit 144 together with signal processing for outputting an audio signal. The control unit 144 compares this frequency information with the oscillation frequency of the VC-TCXO (voltage controlled temperature compensated crystal oscillator) 128 to calculate the frequency deviation Δf. Then, the control unit 144 generates a digital voltage for controlling the oscillation frequency of the VC-TCXO 128 so that the frequency deviation Δf becomes zero, and applies it to the frequency adjustment terminal of the VC-TCXO 128 via the D / A converter 132. To do. As a result, the oscillation frequency of the VC-TCXO 128 is AFC controlled based on the oscillation frequency of the base station. Further, the temperature information from the temperature detection unit 129 is supplied to the control unit 144 via the A / D converter 131 and is used for controlling the oscillation frequency of the VC-TCXO 128 by the control unit 144.
The oscillation signal of the VC-TCXO 128 is connected as a reference clock for the first PLL circuit 115 and the second PLL circuit 118.

The first PLL circuit 115 controls the oscillation frequency of the VCO (voltage controlled oscillator) 114 and the VCO 126 using the oscillation signal of the VC-TCXO 128 as a reference clock. The VCO 114 is connected to the mixer 113 as a first local oscillation circuit on the reception side, and the VCO 126 is connected to the mixer 125 as a second local oscillation circuit on the transmission side.
The second PLL circuit 118 controls the oscillation frequency of the VCO 117 and VCO 124 using the oscillation signal of the VC-TCXO 128 as a reference clock. The VCO 117 is connected to the mixer 113 as a first local oscillation circuit on the reception side, and the VCO 126 is connected to the mixer 125 as a second local oscillation circuit on the transmission side.

In the above first conventional example, the control unit 144 stores the transmission frequency information output from the reception signal processing unit 143 from the base station, the oscillation frequency of the VC-TCXO 128, and the temperature information from the temperature detection unit 129. A control voltage to be given to the VC-TCXO 128 is generated based on the compensation information stored in the unit 145.
When the signal from the base station serving as the reference is not received, the control voltage is generated based on the value of the control voltage of the VC-TCXO 128 when the signal from the base station stored in the storage unit 145 is received.

Next, a second conventional example will be described.
As shown in FIG. 7, the transmitter / receiver of a mobile station used in a fire fighting radio, etc. has a receiving circuit that receives a signal sent from the base station, a communication to the base station, a transmission to the base station, or other Mobile stations (such as emergency vehicles in the field) are used for communication between 1-wave simplex transmission / reception circuits used for communication between each other, and communication with the base station is a 2-wave duplex system. Communication with the station is a one-wave simplex system.
The transmitter / receiver shown in FIG. 7 includes a first receiving circuit 41 and a base station receiving antenna 1 for receiving a transmission signal from a base station, and a transmitting / receiving circuit 42 including a transmitting circuit 43 and a second receiving circuit 44, and a transmitting / receiving antenna. 9.

  The first receiving circuit 41 includes a base station receiving antenna 1, an amplifier 2, a first mixer 3, a BPF (band pass filter) 4, a second mixer 5, a BPF 6, an A / D converter 7, and a first demodulator 8. And connected to the received signal processing unit 30.

The output of the first demodulator 8 is composed of a first frequency measurement unit 18, a frequency control unit 25, and a D / A converter 24, and generates a control voltage for controlling the oscillation frequency of the VC-TCXO 23. To the VC-TCXO 23.
The oscillation signal of the VC-TCXO 23 serves as a reference clock for the first reception synthesizer (PLL circuit) 20, the second reception synthesizer 21, and the transmission synthesizer 22 that are connected in parallel. Generates a local oscillation signal and inputs it to the first mixers 3 and 12 and the quadrature modulation unit 27.
Further, a TCXO (temperature compensated crystal oscillator) 14 for local oscillation is connected to the second mixer 5 of the first receiving circuit 41 and the second mixer 15 of the second receiving circuit 44.

The transmission / reception circuit 42 includes a transmission circuit 43 and a second reception circuit 44, and is connected to the transmission / reception antenna 9 via the transmission / reception changeover switch 10.
The second receiving circuit 44 includes an amplifier 11, a first mixer 12, a BPF 13, a second mixer 15, a BPF 16, an A / D converter 17, and a second demodulator 19 from one terminal of the transmission / reception selector switch 10. The reception signal processing unit 31 is connected.

  The transmission circuit 43 includes a modulation unit 29, a D / A converter 28, a quadrature modulation unit 27, and an amplifier 26 from the transmission signal processing unit 32, and is connected to the transmission / reception antenna 9 via the other terminal of the transmission / reception changeover switch 10. ing.

  In the above configuration, the first receiving circuit connected to the base station receiving antenna 1 amplifies the received signal received from the base station by the amplifier 2 and uses the oscillation signal of the VC-TCXO 23 as the reference clock. The local oscillation signal generated by the reception synthesizer 20 is mixed with the first mixer 3 to down-convert the frequency of the reception signal to convert it to a first IF (intermediate frequency) signal. Further, the oscillation signal of the TCXO 14 Mixing is performed by the mixer 5 and the frequency is down-converted to be converted into a second IF signal.

Only the necessary frequency band signals of the first IF signal are extracted by the BPF 4 and the second IF signal is extracted by the BPF 6, quantized by the A / D converter 7, and input to the first demodulator 8. The signal input to the first demodulator 8 is demodulated into a baseband signal (digital signal) by the first demodulator.
The demodulated baseband signal is subjected to digital signal processing by the reception signal processing unit 30 and reproduced as an audio signal.

The second receiving circuit 44 amplifies the received signal that has received a signal from another mobile station by the amplifier 11, and generates a local oscillation signal generated by the second receiving synthesizer 21 using the oscillation signal of the VC-TCXO 23 as a reference clock. By mixing in the first mixer 12, the frequency of the received signal is down-converted and converted to a first IF (intermediate frequency) signal. Further, the oscillation signal of the TCXO 14 is mixed by the second mixer 15, the frequency is down-converted and converted into a second IF signal, quantized by the A / D converter 17, and input to the second demodulator 19. The signal input to the second demodulator 19 is demodulated into a baseband signal (digital signal) by the second demodulator.
The demodulated baseband signal is subjected to digital signal processing by the reception signal processing unit 31 and reproduced as an audio signal.

  The transmission circuit 43 performs digital signal processing on the audio signal input by the transmission signal processing unit 32, converts the signal modulated by the modulation unit 29 into an analog signal by the D / A converter 28, and transmits the signal by the quadrature modulator 27. A modulated wave is generated together with the carrier wave inputted from the synthesizer 22, amplified by the amplifier 26, and sent to the transmission / reception selector switch 10.

  Further, the frequency error is measured by the first frequency measuring unit 18 from the symbol received from the baseband signal output by the first demodulating unit 8, and the frequency control unit 25 minimizes the measured frequency error by VC− The oscillation frequency of the TCXO 23 is controlled.

JP 2008-219719 A

  In the transmitter / receiver of the first conventional example shown in FIG. 6, in order to convert the received signal into the first IF signal and the second IF signal, the two PLL circuits 115 and 118 are provided using the VC-TCXO 128 having high frequency stability as a reference clock. To generate a local oscillation signal. Although the accuracy of the IF frequency is improved by using two PLL circuits, there is a problem that the circuit configuration is complicated and expensive, and the power consumption increases.

In the transmitter / receiver of the second conventional example shown in FIG. 7, the second local oscillation signal supplied to the second mixers 5 and 15 uses the oscillation signal of the TCXO 14, so that the second PLL circuit as in the first conventional example is required. However, the circuit configuration is simple and inexpensive.
However, the compensation of the oscillation frequency of the TCXO 14 is only the temperature compensation performed by the oscillator itself, and cannot compensate for the error due to the change of the oscillator over time, etc. Therefore, there is an error between the design oscillation frequency and the actual oscillation frequency. May occur.
The control of the reception frequency of the transceiver of the second conventional example is performed by receiving a signal with high frequency accuracy from the base station and converting it to the first IF frequency and the second IF frequency by the first mixer 3 and the second mixer 5, respectively. The frequency measurement unit 18 measures the frequency of the baseband signal output from the first demodulator 8 at the subsequent stage, and the frequency control unit 25 detects an error from the frequency of the normal baseband signal without error. A digital voltage for controlling the oscillation frequency of the VC-TCXO 128 for canceling the detected error is output, and the oscillation frequency of the VC-TCXO 23 controlled via the D / A converter 24 is corrected. Therefore, when an error occurs in the oscillation frequency of the TCXO 14, the oscillation frequency of the TCXO 14 is changed by controlling the VC-TCXO 23 based on the received signal from the base station and changing the first local oscillation frequency generated by the first reception synthesizer. Correct the error. The oscillation signal of the VC-TCXO 23 is also used as a clock for generating a carrier wave of the transmission circuit. When the oscillation frequency of the VC-TCXO 23 is corrected by an error in the oscillation frequency of the TCXO 14, the transmission signal There was a problem that the frequency also fluctuated and the accuracy of the frequency was lowered.

  The present invention has been made in view of the above-described problems. In a transceiver having a single-wave simplex transmission / reception circuit in addition to a first reception circuit dedicated to a base station, the present invention serves as a reference clock during transmission. The object is to improve the accuracy of the transmission frequency by controlling the oscillation frequency of the VC-TCXO 23.

  According to a first aspect of the present invention, a first receiving circuit that receives and demodulates a transmission signal from the base station and a transmission circuit that transmits a signal having a frequency different from the transmission frequency from the base station are received and demodulated. A single-wave simplex transmission / reception circuit comprising a reception circuit, and a common reference for generating a first local oscillation signal of each of the first reception circuit and the second reception circuit and a transmission signal of the transmission circuit In a transceiver having a voltage-controlled oscillator serving as a clock and an oscillator that generates a second local oscillation signal common to the first receiving circuit and the second receiving circuit, the signal received by the first receiving circuit is the first A first frequency measurement unit that measures the frequency error of the reception frequency from the baseband signal demodulated by the demodulation unit, and a frequency error of the reception frequency from the baseband signal demodulated by the second demodulation unit of the signal received by the second reception circuit A second frequency measuring unit for measuring; a frequency error detecting unit for detecting a difference between the frequency error measured by the first frequency measuring unit and the frequency error measured by the second frequency measuring unit; When transmitting a signal to a base station or another mobile station, the oscillation frequency of the voltage controlled oscillator is reduced so as to reduce the error detected by the frequency error detector by taking the transmission signal into the second receiving circuit. It is the transmitter / receiver characterized by providing the frequency control part which controls.

  According to a second aspect of the present invention, a first receiving circuit that receives and demodulates a transmission signal from the base station and a transmission circuit that transmits a signal having a frequency different from the transmission frequency from the base station are received and demodulated. A single-wave simplex transmission / reception circuit comprising a reception circuit, and a common reference for generating a first local oscillation signal of each of the first reception circuit and the second reception circuit and a transmission signal of the transmission circuit In a transceiver having a voltage-controlled oscillator serving as a clock and an oscillator that generates a second local oscillation signal common to the first receiving circuit and the second receiving circuit, a second of the signals received by the first receiving circuit A first frequency measuring unit for measuring an intermediate frequency; a second frequency measuring unit for measuring a second intermediate frequency of a signal received by the second receiving circuit; and a second intermediate frequency measured by the first frequency measuring unit. And the second frequency measurement A frequency error detection unit that detects a difference between the second intermediate frequencies measured in (2) is provided, and when transmitting a signal to the base station or another mobile station in the transmission circuit, the transmission signal is taken into the second reception circuit, A transceiver comprising a frequency control unit for controlling an oscillation frequency of the voltage controlled oscillator so as to reduce an error detected by the frequency error detection unit.

  According to a third aspect of the present invention, in the transceiver according to the first or second aspect, a switch is provided for taking in a transmission signal from the transmission circuit to the second reception circuit side.

  According to a fourth aspect of the present invention, in the transceiver according to the first or second aspect, a directional coupler is provided for taking in a transmission signal from the transmission circuit to the second reception circuit side. It is.

  According to a fifth aspect of the present invention, in the transceiver according to the first or second aspect, the first frequency measurement unit measures the frequency at predetermined time intervals while the first reception circuit is receiving a transmission signal from the base station. The measured frequency is held until the next measurement, and when the transmission circuit does not receive a transmission signal from the base station when transmitting a signal to the base station or another mobile station, the held frequency is used. It is characterized by this.

  According to the first and second aspects of the invention, the transmission signal of the own station is taken into the second receiving circuit, the frequency of the baseband signal or the second intermediate frequency of the taken signal is measured, and the base station serving as the reference TCXO oscillation frequency of the second local oscillation by controlling the oscillation frequency of the VC-TCXO so as to eliminate the difference from the baseband signal frequency or the second intermediate frequency. Thus, the accuracy of the transmission frequency of the local station is improved.

  According to the third and fourth aspects of the invention, there is an effect that the configuration for taking in the transmission signal transmitted from the own station from the transmission circuit side to the second reception circuit side is extremely simple.

  According to the fifth aspect of the present invention, since the signal from the base station serving as the frequency reference is not always transmitted, the frequency is measured every predetermined time when receiving the base station, and the latest measured value By holding this, there is an effect that even if the transmission signal from the base station is not received when the own station transmits, the frequency error detection unit can detect an error using the held frequency.

It is a block diagram which shows Example 1 of the circuit of the transmitter / receiver by this invention. (A) is a block diagram of the demodulator, and (b) is a constellation diagram showing the magnitude and phase of the demodulated IQ signal. It is a constellation figure explaining the effect | action of a frequency measurement part. It is a block diagram which shows Example 2 by this invention. It is a block diagram which shows Example 3 by this invention. It is a block diagram which shows a 1st prior art example. It is a block diagram which shows a 2nd prior art example.

  A single-wave simplex comprising a first receiving circuit that receives and demodulates a transmission signal from the base station, and a second receiving circuit that receives and demodulates a signal having a frequency different from the transmission frequency from the base station. A voltage-controlled oscillator having a transmission / reception circuit of a type and serving as a common reference clock for generating a first local oscillation signal of each of the first reception circuit and the second reception circuit and a transmission signal of the transmission circuit; A baseband signal obtained by demodulating a signal received by the first receiving circuit by a first demodulating unit in a transceiver having an oscillator that generates a second local oscillation signal common to the first receiving circuit and the second receiving circuit; A second frequency that measures the frequency error of the reception frequency from a first frequency measurement unit that measures the frequency error of the reception frequency and a baseband signal that is demodulated by the second demodulation unit of the signal received by the second reception circuit A frequency error detection unit that detects a difference between the frequency error measured by the first frequency measurement unit and the frequency error measured by the second frequency measurement unit, and a base station or other Frequency control for controlling the oscillation frequency of the voltage-controlled oscillator so as to reduce the error detected by the frequency error detection unit by taking the transmission signal into the second receiving circuit when transmitting a signal to the mobile station By providing the unit, the error of the oscillation frequency of the oscillator that generates the second local oscillation signal is corrected to improve the accuracy of the transmission frequency of the local station.

Next, Example 1 of the present invention will be described.
The transceiver of the present invention has the configuration shown in the block diagram of FIG. The basic configuration as a transceiver is the same as that of the second conventional example shown in FIG. 7, and the description of the parts common to the second conventional example is omitted.
The transmitter / receiver of the present invention is different from the transmitter / receiver of the second conventional example in that the change-over switch 33 for taking in the transmission signal to the second reception circuit when the transmission circuit 43 transmits to the base station or another mobile station. And a second frequency measuring unit 34 that is connected to the second demodulating unit 19 on the second receiving circuit 44 side and that measures a frequency error from a symbol received from a baseband signal, and is measured by the second frequency measuring unit 34 The frequency error and the frequency error measured by the first frequency measurement unit 18 connected to the first demodulation unit 8 are input to the frequency error detection unit 35, and the frequency error of the received signal from the base station and the transmission signal of the own station are detected. The difference is that the difference from the frequency error is detected.
Based on the difference value detected by the frequency error detector 35, the frequency control unit 25 controls the oscillation frequency of the VC-TCXO 23.

Next, the operation of the transceiver configured as described above will be described. However, a general transmission / reception operation as a transceiver is the same as that in FIG.
A transmission signal from the base station is received by the base station receiving antenna 1, a second IF signal is generated by the first receiving circuit 41, and demodulated into a baseband signal by the first demodulator 8.
The demodulated baseband signal is digitally processed by the reception signal processing unit 30 and reproduced as an audio signal, and the frequency of the baseband signal is measured by the first frequency measurement unit 18.

On the other hand, when the transmission circuit 43 transmits to the base station or another mobile station, the audio signal input by the transmission signal processing unit 32 is subjected to digital signal processing, and the signal modulated by the modulation unit 29 is converted by the D / A converter 28. The signal is converted into an analog signal, a modulated wave is generated together with the carrier wave inputted from the transmission synthesizer 22 by the quadrature modulator 27, amplified by the amplifier 26 and sent to the transmission / reception selector switch 10, and the transmission signal is changed by the selector switch 33. The transmission circuit is switched to the second reception circuit. At this time, the transmission / reception changeover switch 10 is not transmitted on the second receiving circuit side.
The second receiving circuit 44 receives and processes the captured transmission signal to generate a second IF signal, which is demodulated into a baseband signal by the second demodulator 19, and a frequency error is calculated from the received symbol from the demodulated baseband signal. It is measured by the dual frequency measuring unit 34.

  The frequency error measured by the first frequency measurement unit 18 and the frequency error measured by the second frequency measurement unit 34 are input to the frequency error detection unit 35 to detect the error, and the frequency control unit 25 After controlling the oscillation frequency of the VC-TCXO 23 in a direction to reduce the error, the transmission / reception selector switch 10 is switched to the transmission circuit side to perform the main transmission.

In FIG. 1, the change-over switch 33 is provided between the amplifier 11 and the first mixer 12, but may be provided in front of the amplifier 11 when the signal level to be captured is small.
More detailed control operation will be described later.

Next, the oscillation frequency of each crystal oscillator and each PLL will be described.
The base station transmission frequency transmitted from the base station to the mobile station is f _FH , the transmission frequency transmitted from the mobile station to the base station (also a frequency for communication between mobile stations) is f _FL , the first IF frequency is f _IF1 , and the second IF frequency. F _IF2 , the oscillation frequency of the VC-TCXO 23 of the transceiver is f _REF , the frequency deviation with respect to the oscillation frequency f _REF of the VC-TCXO 23 is Δα, the oscillation frequency of the TCXO 14 is f _LO2 , and the oscillation frequency f _LO2 of the TCXO 14 Assuming that the frequency deviation is Δβ, the oscillation frequencies of the VC-TCXO 23 and the TCXO 14 are as follows.
The oscillation frequency of the VC-TCXO 23: f _REF × (1 + Δα) (1)
TCXO14 oscillation frequency: f _LO2 × (1 + Δβ) (2)

At this time, the oscillation frequencies of the synthesizers 20, 21, and 22 have the same frequency deviation as the oscillation frequency of the VC-TCXO 23, and are as follows.
Oscillation frequency of first receiving synthesizer 20: f _LO1H = (f _FH + f _IF1 ) × (1 + Δα) (3)
Oscillation frequency of second reception synthesizer 21: f _LO1L = (f _FL + f _IF1 ) × (1 + Δα) (4)
Oscillation frequency of transmission synthesizer 22: f _FLT = f _FL × (1 + Δα) (5)

From Equations (3) and (4), the first IF frequency output from the first mixers 3 and 12 is as follows.
First IF frequency of the first receiving circuit 41: f _IF1H = f _IF1 × (1 + Δα) + f _FH × Δα (6)
First IF frequency of second receiving circuit 44: f _IF1L = f _LO1L -f _FLT = f _IF1 × (1 + Δα) (7)

From equations (6) and (7), the second IF frequency output from the second mixers 5 and 15 is as follows.
Second IF frequency of the first receiving circuit 41: f _IF2H = f _IF1 × (1 + Δα) + f _FH × Δα−f _LO2 × (1 + Δβ) (8)
Second IF frequency of second receiving circuit 44: f _IF2L = f _IF1 × (1 + Δα) −f _Lo2 × (1 + Δβ) (9)

Therefore, if the difference (f _IF2H −f _IF2L ) between the frequencies measured by the first frequency measuring unit 18 and the second frequency measuring unit 34 is taken, the oscillation frequency deviation Δβ of the TCXO 14 is canceled out, and the frequency error is f _FH × Δα. Only the term remains.
When the oscillation frequency of the VC-TCXO 23 is controlled so that this frequency error becomes 0, Δα = 0, and the oscillation frequency of the VC-TCXO 23 can be made to accurately follow the frequency of the transmission signal from the base station.
As a result, the internal reference clock of the transceiver can accurately follow the transmission frequency of the base station without being affected by the deviation of the oscillation frequency (second local oscillation frequency) of the TCXO 14.

Next, control of the oscillation frequency of the VC-TCXO 23 by the frequency control unit 25 from measurement of the reception frequency by the first frequency measurement unit 18 will be described in detail.
First, as shown in FIG. 2A, the first demodulator 8 generates a second IF signal, a carrier signal 49 of the second IF signal by a π / 2 phase shifter 40, and a clock signal delayed in phase by π / 2. Multiplication (mixing) is performed by the mixers 36 and 37, and harmonic components are suppressed by the LPFs 38 and 39, and an IQ signal (baseband signal) is output.
The relationship between the IQ signal and the phase and amplitude of the carrier wave can be expressed by a constellation as shown in FIG. In the case of the QPSK modulation method, the symbol position is a white circle position. In the case of the 1 / 4π shift QPSK modulation method, the positions of symbols are alternately white and black circles.

When receiving and demodulating a signal from the base station, the first frequency measurement unit 18 detects the phase change amount Δθ and the frequency change amount Δf from the symbol of the received signal.
The second frequency measurement unit 34 detects the phase change amount Δθ and the frequency change amount Δf from the symbol of the signal that has received the transmission signal of the local station, averages the detected phase change amount Δθ over several frames, and converts it into a frequency. Frequency error.
As shown in FIG. 3, each phase change amount Δθ is detected by setting the reference position predicted from the previously detected symbol position as (I1, Q1) and the actual detected symbol position as (I2, Q2). Δθ = tan ⁻¹ (Q2 / I2) −tan ⁻¹ (Q1 / I1).
The frequency change amount Δf is converted by Δf = Δθ / 2π × 4800 when the symbol rate (modulation speed) is 4800 sps.

The frequency error detection unit 35 calculates and outputs the difference between the measurement result of the first frequency measurement unit 18 and the measurement result of the second frequency measurement unit 34.
The frequency control unit 25 adjusts the control voltage of the VC-TCXO 23 when the frequency difference value calculated by the frequency error detection unit 35 exceeds an allowable value (for example, within ± 200 Hz), and performs the next control. Do.

When the frequency measured by the second frequency measurement unit 34 is higher than the frequency measured by the first frequency measurement unit 18, the control voltage to the VC-TCXO 23 is adjusted so as to lower the oscillation frequency.
Conversely, when the frequency measured by the second frequency measuring unit 34 is smaller than the frequency measured by the first frequency measuring unit 18, the control voltage to the VC-TCXO 23 is adjusted so as to raise the oscillation frequency.
That is, when the transmission frequency of the own station is higher, the transmission frequency is lowered by lowering the oscillation frequency of the VC-TCXO 23, and when the transmission frequency of the own station is lower, the oscillation frequency of the VC-TCXO 23 is raised. Increase the frequency.

As described above, when the own station transmits to the base station or another mobile station, the transmission signal is taken into the second receiving circuit 44, the frequency is measured by the second frequency measuring unit 34, and the error is detected by the frequency error detecting unit 35. The transmission frequency is corrected by adjusting the control voltage to the VC-TCXO 23, but the frequency of the transmission signal is measured by the second frequency measurement unit 34 during transmission, and the error by the frequency error detection unit 35 is detected. Then, the transmission frequency may be corrected by operating the frequency control unit 25 based on the error held at the next transmission.
Since the base station does not always transmit to the mobile station when the own station transmits to the base station or another mobile station, the first receiving circuit 41 receives a signal from the base station. The first frequency measurement unit 18 measures the frequency of the signal from the base station at predetermined time intervals, holds the latest measurement value, and corrects the transmission frequency when the local station transmits the latest measurement. Use the value.

  In the above embodiment, an error is detected from the baseband signal demodulated by the first demodulator 8 and the baseband signal demodulated by the second demodulator 19 to control the oscillation frequency of the VC-TCXO 23. However, the present invention is not limited to this, and the second IF frequency output from the A / D converter 7 of the first receiving circuit 41 and the A of the second receiving circuit 44 are not limited to this, as shown in FIG. An error may be detected by the frequency error detection unit 35 for the second IF frequency output from the / D converter 17 to control the oscillation frequency of the VC-TCXO 23.

  In the first and second embodiments, the changeover switch 33 is used to capture the transmission signal of the own station from the transmission circuit 43 to the second reception circuit 44. However, the present invention is not limited to this. For example, FIG. As shown, a directional coupler 46 may be used. When taking in before transmitting from the transmission / reception antenna 9, the dummy changeover switch 47 and the dummy loader 48 may be provided, and the dummy changeover switch 37 may be switched to the dummy loader side.

  DESCRIPTION OF SYMBOLS 1 ... Base station receiving antenna, 2 ... Amplifier, 3 ... 1st mixer, 4 ... BPF, 5 ... 2nd mixer, 6 ... BPF, 7 ... A / D converter, 8 ... 1st demodulation part, 9 ... Transmission / reception antenna DESCRIPTION OF SYMBOLS 10 ... Transmission / reception changeover switch, 11 ... Amplifier, 12 ... 1st mixer, 13 ... BPF, 14 ... TCXO, 15 ... 2nd mixer, 16 ... BPF, 17 ... A / D converter, 18 ... 1st frequency measurement part , 19 ... second demodulator, 20 ... first reception synthesizer, 21 ... second reception synthesizer, 22 ... transmission synthesizer, 23 ... VC-TCXO, 24 ... D / A converter, 25 ... frequency control unit, DESCRIPTION OF SYMBOLS 26 ... Amplifier, 27 ... Quadrature modulation part, 28 ... D / A converter, 29 ... Modulation part, 30 ... Reception signal processing part, 31 ... Reception signal processing part, 32 ... Transmission signal processing part, 33 ... Changeover switch, 34 ... second frequency measurement unit, 35 ... frequency Error detection unit 36, 37 ... mixer, 39, 39 ... LPF, 40 ... π / 2 phase shifter, 41 ... first receiver circuit, 42 ... transmitter / receiver circuit, 43 ... transmitter circuit, 44 ... second receiver circuit, 46 ... Directional coupler, 47 ... Dummy changeover switch, 48 ... Dummy loader, 49 ... Carrier wave.

Claims (5)

A single-wave simplex comprising a first receiving circuit that receives and demodulates a transmission signal from the base station, and a second receiving circuit that receives and demodulates a signal having a frequency different from the transmission frequency from the base station. A voltage-controlled oscillator having a transmission / reception circuit of a type and serving as a common reference clock for generating a first local oscillation signal of each of the first reception circuit and the second reception circuit and a transmission signal of the transmission circuit; In the transceiver having an oscillator that generates a second local oscillation signal common to the first receiving circuit and the second receiving circuit,
A first frequency measurement unit that measures a frequency error of a reception frequency from a baseband signal demodulated by a first demodulation unit for a signal received by the first reception circuit;
A second frequency measurement unit that measures a frequency error of the reception frequency from the baseband signal demodulated by the second demodulation unit for the signal received by the second reception circuit;
A frequency error detection unit for detecting a difference between the frequency error measured by the first frequency measurement unit and the frequency error measured by the second frequency measurement unit;
When transmitting a signal to a base station or another mobile station by the transmission circuit, the voltage controlled oscillator is configured so that the transmission signal is taken into the second reception circuit and the error detected by the frequency error detection unit is reduced. A transceiver having a frequency control unit for controlling the oscillation frequency of the transmitter. A single-wave simplex comprising a first receiving circuit that receives and demodulates a transmission signal from the base station, and a second receiving circuit that receives and demodulates a signal having a frequency different from the transmission frequency from the base station. A voltage-controlled oscillator having a transmission / reception circuit of a type and serving as a common reference clock for generating a first local oscillation signal of each of the first reception circuit and the second reception circuit and a transmission signal of the transmission circuit; In the transceiver having an oscillator that generates a second local oscillation signal common to the first receiving circuit and the second receiving circuit,
A first frequency measuring unit for measuring a second intermediate frequency of the signal received by the first receiving circuit;
A second frequency measuring unit for measuring a second intermediate frequency of the signal received by the second receiving circuit;
A frequency error detection unit for detecting a difference between the second intermediate frequency measured by the first frequency measurement unit and the second intermediate frequency measured by the second frequency measurement unit;
When transmitting a signal to a base station or another mobile station by the transmission circuit, the voltage controlled oscillator is configured so that the transmission signal is taken into the second reception circuit and the error detected by the frequency error detection unit is reduced. A transceiver having a frequency control unit for controlling the oscillation frequency of the transmitter.   3. The transceiver according to claim 1, further comprising a switch for taking a transmission signal from the transmission circuit into the second reception circuit.   3. The transceiver according to claim 1, further comprising a directional coupler for taking a transmission signal from the transmission circuit into the second reception circuit. The first frequency measurement unit measures the frequency every predetermined time while the first receiving circuit receives a transmission signal from the base station, and holds the measured frequency until the next measurement,
3. The transmission / reception according to claim 1, wherein when the transmission circuit does not receive a transmission signal from the base station when transmitting a signal to the base station or another mobile station, the held frequency is used. Machine.

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