JPH06326740A - Mobile radio equipment - Google Patents

Abstract

PURPOSE:To stabilize an oscillating frequency of a reference oscillator with the accuracy equal to that for a stable transmission wave from a base station by obtaining a frequency error from control data for carrier reproduction. CONSTITUTION:A frequency error based on an oscillating frequency error of a reference oscillator 6 is superimposed on an intermediate frequency signal received by a demodulator 3. The demodulator 3 provides an output of demodulation data and also an output of frequency data representing a frequency of a reproduced carrier. The frequency data are fed to a frequency error detection circuit 4, in which a frequency error with respect to the predetermined intermediate frequency signal frequency is detected. A reference oscillation control circuit 5 receiving the detection output generates a frequency error compensation signal to compensate the frequency error and inputs the signal to the reference oscillator 6 thereby controlling the oscillating frequency of the frequency reference signal till the frequency error reaches a predetermined error or below and making the oscillating frequency stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used in digital mobile radio communications using angle modulation. In particular, the present invention relates to a mobile wireless device suitable for a communication system that requires a small carrier drift. The present invention is suitable for use in digital mobile radio communication in the UHF band.

[0002]

2. Description of the Related Art In the case of performing communication by angle modulation, carrier quality drifts, so that the transmission quality deteriorates significantly. Looking at the transmission characteristics within the pass band, characteristic deterioration such as distortion of transmission signals, deterioration of frequency characteristics, and deterioration of error rate occurs. In addition, out-of-band transmission characteristics increase leakage power to adjacent channels. In order to prevent this, (1) the channel arrangement should be sufficiently wide compared to the transmission bandwidth,
Either (2) increasing the stability of the local oscillator or modulator that causes the carrier wave drift, or (3) detecting the carrier wave drift and automatically adjusting it to a desired carrier wave frequency.

However, in the method (1), considering that the effective radio frequencies are more and more limited with respect to the future increase in the communication volume, a communication system in which one radio frequency is assigned to one speech channel, in particular. Then, it is difficult to take the channel arrangement at wide intervals. In addition, even in multiplex communication and other communication methods that require a wide transmission band, narrowing of the transmission bandwidth by multilevel modulation and other technologies is being promoted due to the recent tightness of radio frequencies, and a margin for carrier drift is realized. Therefore, it is difficult to widen the wireless channel interval.

The method (2) does not pose a problem when a highly stable oscillator can be used as in the fixed wireless communication system. However, this is a problem when a small and simple mobile wireless device such as a mobile communication system is required. Generally, in a mobile wireless device, a crystal oscillator that stably oscillates at a relatively low frequency is used as a reference oscillator, and a voltage-controlled oscillator is phase-locked to obtain a carrier band frequency signal, or
A direct digital synthesizer directly oscillates a carrier wave phase-locked to generate one or a plurality of local oscillation signals. In this case, the stability of the crystal oscillator used as the reference oscillator becomes a problem.

As a crystal oscillator having improved stability against temperature change, a temperature-compensated crystal oscillator (TCXO: Temperat) is used.
ure Compensated Crystal Oscillator) is known. However, when mass production is considered under the constraint that the mobile communication device is equipped with the mobile communication device, the practical stability is considered to be about 1.5 to 2 ppm. Further, a temperature change of the oscillation frequency of the crystal is stored in a memory, and the frequency is controlled by controlling the capacitance array based on the temperature information from the temperature detecting element (DTCXO: Digitall).
y Temperature Compensated Crystal Oscillator) has also been put into practical use, and it has become possible to set the compensation accuracy for temperature changes to 0.5 ppm or less. However, none of the oscillators can compensate the oscillation frequency with respect to aging. As the method (3), a method of frequency-locking a local oscillator with a received wave having high frequency accuracy is generally used. A conventional example of this method will be described below.

FIG. 8 shows a configuration example of a mobile radio device having a general frequency stabilizing function used in a mobile communication system using analog angle modulation.

The antenna 1 transmits a base station transmission wave whose frequency is stable.
The frequency is converted into an intermediate frequency signal by the receiving circuit 2, and the intermediate frequency signal is passed to the noise removing circuit 10. As the noise elimination circuit 10, for example, a band pass filter is used. The oscillation frequency error of the reference oscillator 6 is superimposed on the intermediate frequency signal via the frequency synthesizer 7. This intermediate frequency signal is measured by the frequency counter 11,
The measurement result is input to the frequency error detection circuit 4. The frequency error detection circuit 4 compares the measurement result with a preset intermediate frequency signal frequency to detect a frequency error. The detected frequency error is input to the reference oscillator control circuit 5. The reference oscillator control circuit 5 generates a frequency error compensation signal for compensating the frequency error, inputs this to the reference oscillator 6, and outputs the oscillation frequency of the reference oscillator 6 until the frequency error becomes equal to or less than a predetermined value. To control.

The reference oscillator 6 stabilized in this way
Output signal is supplied to one or a plurality of frequency synthesizers 7. The output of the frequency synthesizer 7 is used as a local oscillation signal for frequency conversion of the received wave in the reception circuit 2 and also as a local oscillation signal for frequency conversion of the transmission signal into a radio frequency in the modulation circuit 8. . The output of the modulation circuit 8 is
It is transmitted to the wireless section via the power amplifier 9. By sharing the frequency synthesizer 7 as the local oscillator of the modulation circuit 8, the transmission frequency of the mobile radio device can be stabilized to the same extent as the stable base station transmission frequency accuracy.

FIG. 9 shows a configuration example of the modulation circuit 8. A signal in the baseband band is input to the modulation input terminal 81, and the angle modulator 82 generates an angle modulation signal by this signal. The local oscillation signal from the frequency synthesizer 7 is input to the local oscillation signal input terminal 83, and the mixer 84 frequency-converts the output of the angle modulator 82 into a desired carrier frequency,
Output to the modulation output terminal 85. Here, the case where the local oscillation signal input terminal 83, the mixer 84, and the frequency synthesizer 7 have a one-stage configuration has been shown, but these may have a multi-stage configuration and sequentially perform frequency conversion to obtain a desired carrier frequency. It is also possible to directly modulate a local oscillation signal having a desired carrier frequency.

[0010]

When analog angle modulation is used, it is possible to measure the frequency with high accuracy by counting the intermediate frequency signal with a frequency counter. However, in the case of a digital modulation method such as FSK or PSK that transmits a digital signal, the carrier frequency deviates because the phase shift of each symbol is biased due to the pattern of the data to be transmitted, and an error occurs in the counter measurement. May occur. This is a negligible value when the data sequence is random, but when there is data of a specific pattern that has a bias of the modulation phase transition even in part, the carrier frequency shifts, causing a measurement error. . Therefore, when the reference oscillator is controlled based on the frequency measurement value of the intermediate frequency signal, the measurement error is also superimposed on the output of the reference oscillator, and there is a problem that the desired frequency stability cannot be obtained.

As a technique for solving this, Japanese Patent Application No. 5-6
No. 3762 (unpublished at the time of filing of the present application, hereinafter referred to as “the previous application”) describes that the frequency of the reproduced carrier wave in the demodulator is not affected by the modulation data sequence, and thus the reproduced carrier wave output from the demodulator is used. A technique for accurately measuring the frequency drift of an intermediate frequency signal by counting the frequency with a frequency counter is disclosed.

An object of the present invention is to improve the technique disclosed in the previous application and to provide a mobile radio device capable of performing frequency stabilization with high accuracy.

[0013]

According to a first aspect of the present invention, there is provided a mobile radio including means for obtaining a frequency error from control data for carrier recovery in a carrier recovery circuit in a demodulator. Machine is provided. When the carrier recovery circuit divides a fixed frequency signal to generate a reproduced carrier signal, the frequency division ratio data may be used.

According to a second aspect of the present invention, there is provided a mobile radio having a means for obtaining a frequency error from the symbol phase data output by the detector in the demodulator.

According to a third aspect of the present invention, the demodulator has a structure for outputting control data for reproducing a carrier wave in a carrier wave reproducing circuit or frequency data obtained by the control data, and measures the frequency of the intermediate frequency signal. There is provided a mobile radio device characterized by comprising: a frequency counter for operating the frequency counter; and a means for selecting one of the count value data output from the frequency counter and the data from the demodulator to obtain a frequency error from the data. It

According to a fourth aspect of the present invention, the demodulator is configured to output the symbol phase data or the data obtained from the symbol phase data. The frequency counter measures the frequency of the intermediate frequency signal, and the frequency counter. And a means for selecting one of the count value data and the data from the demodulator to obtain the frequency error from the data.

According to a fifth aspect of the present invention, means for selecting one of the intermediate frequency signal output from the receiving circuit and the reproduced carrier signal of the demodulator, a frequency counter for measuring the selected signal frequency, and A mobile wireless device is provided, which is provided with means for obtaining an oscillation frequency error of a reference oscillator from a count value of a frequency counter.

[0018]

As a demodulator installed in a mobile radio for digital communication, generally, a synchronous detector, an adaptive synchronous detector,
Delay detectors and the like are known. These can be realized by combining individual analog components and digital components, but in general, they are formed into an LSI by a logic circuit or the like in order to achieve size reduction, weight reduction, and no adjustment.

The synchronous detector and the adaptive synchronous detector are provided with a carrier recovery circuit for obtaining a phase reference for detecting a received modulated wave, and can perform demodulation operation by following the frequency drift of the local oscillator. . Further, in the case of the delay detector, it is known that the carrier frequency error is detected as the rotation of the symbol phase. In these demodulators, even if the modulation data sequence is not completely randomized, the frequency error detected from the reproduced carrier frequency or the symbol phase rotation does not depend on the pattern of the modulation data. Therefore, this is used to detect the frequency error.

When the frequency error is obtained from the control data for reproducing the carrier wave, not only the frequency can be stabilized at high speed and with high accuracy, but also the frequency counter is not required, so that the circuit scale can be reduced.

When obtaining the frequency error from the symbol phase data, the frequency error is detected from the phase rotation amount within a fixed time to compensate the oscillation frequency error of the reference oscillator. Also in this case, not only can frequency stabilization be achieved with high accuracy, but a frequency counter is not required and the circuit scale can be reduced.

When either the frequency of the intermediate frequency signal or the data from the demodulator can be selected to detect the frequency error, for example, the demodulator can first follow the measurement result of the frequency error of the intermediate frequency signal. The oscillation frequency of the reference oscillator is controlled so that it falls within the frequency range, and then the frequency error is detected from the data output from the demodulator. As a result, it is possible to perform accurate frequency stabilization even with respect to the frequency error of the reference oscillator that exceeds the tracking range of the demodulator.

Similarly, when one of the intermediate frequency signal and the reproduction carrier frequency is selected and measured by the frequency counter, the frequency range in which the demodulator can follow is first determined from the measurement result of the frequency error of the intermediate frequency signal. Then, the oscillation frequency of the reference oscillator is controlled, and then the reproduced carrier frequency is measured by the frequency counter to detect the frequency error. As a result, it is possible to perform accurate frequency stabilization even with respect to the frequency error of the reference oscillator that exceeds the tracking range of the demodulator.

[0024]

1 is a block diagram showing a mobile radio device according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing a carrier recovery circuit in a demodulator.

This mobile radio device includes a receiving circuit 2 which receives an angle-modulated digital radio signal by an antenna 1 and outputs an intermediate frequency signal, a demodulator 3 which demodulates the received signal from the intermediate frequency signal, and a receiving circuit 2. A frequency synthesizer 7 for supplying a local oscillation frequency to the circuit 2, a reference oscillator 6 for generating a signal serving as a frequency reference of the frequency synthesizer 7, and an intermediate frequency via the frequency synthesizer 7 due to an oscillation frequency error of the reference oscillator 6. A frequency error detection circuit 4 as frequency error detection means for detecting a frequency error superimposed on a signal, and a reference oscillator control circuit 5 for controlling the oscillation frequency of the reference oscillator 6 based on the output of the frequency error detection circuit 4 are provided. Prepare A demodulator 3 having a synchronous detection waveform or an adaptive synchronous detection waveform is used, and a carrier recovery circuit for reproducing a carrier of an intermediate frequency signal is provided therein. The mobile radio also includes a modulation circuit 8 that performs modulation using the output of the frequency synthesizer 7 as a carrier, and a power amplifier 9 that amplifies the modulated wave.

A feature of this embodiment is that the demodulator 3 outputs a numerical value related to the control data for reproducing the carrier wave in the carrier wave reproducing circuit as frequency data, and the frequency error detecting circuit 4 uses this frequency data. The frequency error is obtained from the above.

As the carrier wave recovery circuit in the demodulator 3, it is possible to use a structure in which the frequency of the reproduced carrier wave is changed by changing the frequency division ratio of the variable frequency divider composed of the logic circuit. An example of this configuration is shown in FIG.

This carrier recovery circuit comprises a detector 31, a control circuit 32, a fixed oscillator 33 and a variable frequency divider 34. The intermediate frequency signal is input to the detector 31, the intermediate frequency signal is detected based on the phase reference signal supplied from the variable frequency divider 34, and phase data is output. Control circuit 32
Detects the frequency error from the phase data and outputs the frequency division ratio data to control the frequency division ratio of the variable frequency divider 34. The variable frequency divider 34 frequency-divides the output of the fixed oscillator 33 according to the frequency division ratio data and outputs a phase reference signal to the wave detector 31. The reproduced carrier signal is included in this phase reference signal.

In this configuration, since the output frequency is uniquely determined for the frequency division ratio data input to the variable frequency divider 34, the numerical value represented by this frequency division ratio data can be used as the frequency data. The carrier recovery circuit follows the frequency drift of the intermediate frequency signal and functions as a kind of narrow band filter, and averages the instantaneous frequency fluctuations due to the modulation component.Therefore, the frequency drift of the intermediate frequency signal with respect to the predetermined frequency from the frequency data Can be accurately detected.

The operation of the mobile radio device of this embodiment will be described below.

The reception wave received by the antenna 1 is frequency-converted into an intermediate frequency signal by the reception circuit 2 and input to the demodulator 3. The intermediate frequency signal input to the demodulator 3 includes
A frequency error based on the oscillation frequency error of the reference oscillator 6 is superimposed. If this frequency error is within the tracking range of the demodulator 3, the frequency of the reproduced carrier wave follows the intermediate frequency signal on which the frequency error is superimposed. The demodulator 3 outputs demodulated data and frequency data representing the frequency of the reproduced carrier wave. This frequency data is supplied to the frequency error detection circuit 4, and the frequency error detection circuit 4 detects the frequency error with respect to the predetermined intermediate frequency signal frequency. The detection output is supplied to the reference oscillator control circuit 5. The reference oscillator control circuit 5 generates a frequency error compensation signal for compensating the frequency error, inputs this to the reference oscillator 6, and controls the oscillation frequency of the frequency reference signal until the frequency error becomes equal to or less than a predetermined value. Control and stabilize operation.

In this embodiment, the frequency error of the intermediate frequency signal is detected by utilizing the fact that the frequency of the reproduced carrier wave in the demodulator 3 is not affected by the modulation data series. Therefore, it is possible to stabilize the frequency with high accuracy even for a digital modulated wave having a specific data pattern. Further, the demodulator 3 and a circuit for realizing the frequency stabilizing function, that is, the frequency error detection circuit 4 and the reference oscillator control circuit 5 are provided.
All can be configured by logic circuits, and can be easily integrated into an LSI. Therefore, downsizing, low power consumption, and no adjustment are possible, which is suitable for a mobile wireless device. Further, in the present embodiment, since it is not necessary to measure the reproduced carrier frequency with the frequency counter, high speed frequency stabilizing operation can be performed. Further, since the frequency counter and the noise removing circuit are unnecessary, there is an advantage that the circuit scale can be reduced.

FIG. 3 is a block diagram showing a mobile radio device according to the second embodiment of the present invention. This embodiment differs from the first embodiment in that the frequency error is obtained from the symbol phase data output by the detector in the demodulator 3. That is, the demodulator 3
Is provided with a detector that detects the intermediate frequency signal and outputs the symbol phase data, and the frequency error detection circuit 4 is configured to obtain the frequency error from the symbol phase data output by the detector or the processed data. .

The frequency stabilizing operation of this embodiment will be described. The symbol phase data obtained by detecting the received modulated wave is extracted from the demodulator 3 and input to the frequency error detection circuit 4, and the frequency error with respect to the predetermined intermediate frequency signal frequency is detected from the phase rotation amount. In this case, the demodulator 3 may use any of the synchronous detection waveform, the adaptive synchronous detection waveform, and the delayed detection waveform. The output signal of the frequency error detection circuit 4 is input to the reference oscillator control circuit 5. The reference oscillator control circuit 5 generates a frequency error compensation signal in order to compensate the frequency error, and inputs this to the reference oscillator 6. In this way, the oscillation frequency of the reference oscillator 6 is controlled and stabilized until the frequency error becomes equal to or less than the predetermined value.

In the present embodiment, since it is not necessary to measure the reproduced carrier frequency using the frequency counter, high speed frequency stabilizing operation becomes possible. Further, since the frequency counter is unnecessary, there is an advantage that the circuit scale can be reduced.

FIG. 4 is a block diagram showing a mobile radio device according to the third embodiment of the present invention. This embodiment differs from the first and second embodiments in that the data output from the demodulator 3 and the count value of the intermediate frequency signal can be selected.
That is, the demodulator 3 is configured to output control data for reproducing the carrier wave in the carrier wave reproducing circuit, symbol phase data from the wave detector, or data obtained by processing the data, and as the frequency error detecting means,
Frequency counter 11 for measuring the frequency of the intermediate frequency signal
And a signal selection circuit 12 and a frequency error detection circuit 4 for selecting one of the count value data output from the frequency counter 11 and the data from the demodulator 3 and obtaining a frequency error from the data. The noise removing circuit 10 is inserted between the receiving circuit 2 and the frequency counter 11.

The operation of the mobile wireless device of this embodiment will be described below. This embodiment can be used for frequency drift compensation that exceeds the tracking range of the demodulator 3.

As in the first embodiment, the received modulated wave is frequency-converted by the receiving circuit 2 into an intermediate frequency signal. The signal selection circuit 12 is connected to the side of the intermediate frequency signal in the initial state. The intermediate frequency signal passes through the noise removing circuit 10 and is frequency-measured by the frequency counter 11. At this time, the measurement frequency includes an error due to an oscillation frequency error of the reference oscillator 6 and a frequency shift due to the influence of the modulation data series, but a relatively wide range of intermediate frequency signal frequencies can be detected. The measurement result is input to the frequency error detection circuit 4, and the frequency error detection circuit 4 detects the frequency error with respect to the predetermined intermediate frequency signal frequency and outputs the frequency error signal. This frequency error signal is input to the reference oscillator control circuit 5, and the reference oscillator control circuit 5 compensates the oscillation frequency error of the reference oscillator 6. At this time, the oscillation frequency error corresponding to the error included in the intermediate frequency measurement value remains, but since the modulation signal of digital communication is generally scrambled by the pseudo-random sequence, the residual frequency error is reduced by the demodulator 3 It is kept within the following range of.

Next, the signal selection circuit 12 switches the connection to the frequency error detection circuit 4 to the demodulator 3 side. The frequency error detection circuit 4 detects a frequency error based on the data from the demodulator 3 and outputs a frequency error signal. This frequency error signal is input to the reference oscillator control circuit 5, and the reference oscillator control circuit 5 generates a frequency error compensation signal for compensating for the frequency error and inputs this to the reference oscillator 6 to determine the frequency error in advance. The oscillation frequency of the reference oscillator 6 is controlled until it becomes equal to or less than the given value.

The data output from the demodulator 3 may be selected as the initial state of the signal selection circuit 12. In this case, when the frequency error is small and is within the tracking range of the demodulator 3 from the beginning, the time required for frequency stabilization can be shortened.

This embodiment can be used when it is expected that the frequency error of the intermediate frequency signal will exceed the tracking range of the demodulator 3. The frequency error of the intermediate frequency signal is corrected by using a frequency counter with a wide frequency measurement range so that the frequency can be stabilized even if the magnitude of the frequency error of the intermediate frequency signal is outside the tracking range of the demodulator 3. The measurement is performed, and rough compensation is performed until the error range can be followed by the demodulator 3. After that, a frequency error is detected from the reproduced carrier frequency data of the demodulator 3 to perform highly accurate error compensation. Therefore, it is possible to perform a highly accurate frequency stabilizing operation even with respect to a wider range of frequency errors.

In this embodiment, the frequency error detection circuit 4 can detect the frequency error from both the output data of the demodulator 3 and the output of the frequency counter 11, but since the output data format is different, different processing is performed. May be required. In that case, a frequency error may be detected from each and the detection result may be selected.

FIG. 5 is a block diagram showing a mobile radio device according to the fourth embodiment of the present invention. This embodiment differs from the third embodiment in that the frequency error is detected from the reproduced carrier signal instead of the data from the demodulator 3. That is, the receiving circuit 2
A signal selection circuit 12 as means for selecting one of the intermediate frequency signal output by the carrier recovery circuit and the reproduced carrier signal output by the carrier recovery circuit in the demodulator 3, and a frequency counter 11 for measuring the selected signal frequency, The frequency error detection circuit 4 is provided as means for obtaining the oscillation frequency error of the reference oscillator 6 from the count value of the frequency counter 11. The noise removing circuit 10 is inserted between the receiving circuit 2 and the signal selecting circuit 12.

The operation of the mobile radio device of this embodiment will be described below. This embodiment can be used for frequency drift compensation that exceeds the tracking range of the demodulator 3.

As in the first embodiment, the received modulated wave is frequency-converted into an intermediate frequency signal by the receiving circuit 2. The signal selection circuit 12 is connected to the side of the intermediate frequency signal in the initial state. The intermediate frequency signal passes through the noise removing circuit 10 and the signal selecting circuit 12, and the frequency is measured by the frequency counter 11. At this time, the measurement frequency includes an error due to an oscillation frequency error of the reference oscillator 6 and a frequency shift due to the influence of the modulation data series, but a relatively wide range of intermediate frequency signal frequencies can be detected. The measurement result is input to the frequency error detection circuit 4, and this frequency error detection circuit 4
Detects a frequency error with respect to a predetermined intermediate frequency signal frequency and outputs a frequency error signal. This frequency error signal is input to the reference oscillator control circuit 5, and the reference oscillator control circuit 5 compensates the oscillation frequency error of the reference oscillator 6. At this time, the oscillation frequency error corresponding to the error included in the intermediate frequency measurement value remains, but since the modulation signal of digital communication is generally scrambled by the pseudo-random sequence, the residual frequency error is reduced by the demodulator 3 It is kept within the following range of.

Next, the signal selection circuit 12 switches the connection to the frequency counter 11 to the reproduced carrier wave output on the demodulator 3 side and measures the reproduced carrier wave frequency. The output of the frequency counter 11 is input to the frequency error detection circuit 4 and is compared with a predetermined intermediate frequency signal frequency to detect the frequency error. The output of the frequency error detection circuit 4 is input to the reference oscillator control circuit 5, and the reference oscillator control circuit 5
Generates a frequency error compensation signal for compensating the frequency error and inputs it to the reference oscillator 6, and controls the oscillation frequency of the reference oscillator 6 until the frequency error becomes equal to or less than a predetermined value.

As the initial state of the signal selection circuit 12, the reproduced carrier wave output from the demodulator 3 may be selected. In this case, when the frequency error is within the tracking range of the demodulator 3 from the beginning, the time required for frequency stabilization can be shortened.

This embodiment can be used when it is expected that the frequency error of the intermediate frequency signal exceeds the tracking range of the demodulator 3. The frequency error of the intermediate frequency signal is corrected by using a frequency counter with a wide frequency measurement range so that the frequency can be stabilized even if the magnitude of the frequency error of the intermediate frequency signal is outside the tracking range of the demodulator 3. The measurement is performed, and rough compensation is performed until the error range can be followed by the demodulator 3. After that, a frequency error is detected from the reproduced carrier frequency data of the demodulator 3 to perform highly accurate error compensation. Therefore, it is possible to perform a highly accurate frequency stabilizing operation even with respect to a wider range of frequency errors.

FIG. 6 is a block diagram showing a mobile radio device according to the fifth embodiment of the present invention. This embodiment is provided with an erroneous pull-in detection circuit 13 which detects the erroneous pull-in of the demodulator from the demodulated data series output from the demodulator 3 and outputs the magnitude and direction of the frequency error of the intermediate frequency signal. Different from the first and second embodiments.

Each of the first to fourth embodiments is capable of highly accurate frequency stabilization against a frequency error within a certain range. However, the TCXO that can be installed in mobile radios
There are many restrictions on parts cost, size, etc.
There is a limit to the improvement of frequency stability. Further, since the frequency synthesizer as the local oscillator oscillates in synchronization with the TCXO, the frequency error increases as the carrier frequency increases. For this reason, when the phase rotation of the received modulated wave due to this reaches a level where it cannot be distinguished from the original modulation phase transition, it exceeds the frequency drift range that the demodulator can follow, and data demodulation cannot be performed normally. Will end up. For example, in the case of QPSK modulation with the bit rate f _b , the phase inversion within one symbol time cannot follow the frequency drift exceeding ± π / 4 radians, that is, f _b / 16 [Hz]. This value is f _b is 40kbit /
2.5 kHz for a QPSK transmission system of about sec
Becomes This is a relatively high carrier frequency, eg 1.5
When converted into the frequency stability required for the reference oscillator of the mobile radio used in the GHz band, it corresponds to 1.7 ppm. The TCXO used for the reference oscillator has a frequency stability of 1.7 ppm or less in consideration of temperature characteristics, power supply voltage characteristics, and long-term stability due to aging,
It is difficult to satisfy all the characteristics such as low cost, small size and light weight, and low power consumption required as a mobile wireless device.

Therefore, in this embodiment, when the frequency error frequency of the intermediate frequency signal falls within the tracking range of the demodulator 3,
The erroneous pull-in detection circuit 13 detects it to stabilize the frequency. This operation will be described below.

As in the first or second embodiment, the received modulated wave is frequency-converted into an intermediate frequency signal by the receiving circuit 2 and input to the demodulator 3. The demodulator 3 outputs demodulated data and also frequency data or symbol phase data. The demodulated data output from the demodulator 3 is input to the false lead-in detection circuit 13.

When the frequency error of the intermediate frequency signal is large and the phase rotation of the received modulated wave due to this becomes indistinguishable from the original modulation phase shift, the demodulator 3 causes a false synchronization phenomenon due to erroneous pull-in. Since the symbol determination is always erroneous in a fixed direction, a fixed conversion occurs in the demodulated data sequence. For example, a signal having a specific data pattern such as a frame synchronization word is uniquely converted into another data pattern according to the positive / negative direction of the frequency error. The false lead-in detection circuit 13 stores these data patterns and detects the false lead-in state of the demodulator by performing coincidence detection or correlation detection between the data patterns and the demodulated data series.

As the erroneous pull-in detection circuit 13, a frame synchronization word detection circuit provided in a general mobile radio for digital communication may be used, or a smaller circuit scale can be used. Further, if coincidence detection or correlation detection is performed on the data pattern corresponding to the positive and negative phase rotation directions of the received modulated wave due to frequency drift, the direction of frequency drift is determined and the determination result is output as a frequency error detection signal. You can also

When the frequency error is large, the erroneous pull-in detection circuit 13 outputs a frequency error detection signal, and the reference oscillator control circuit 5 compensates the frequency of the reference oscillator 6 based on this frequency error detection signal. When the frequency error is small, the frequency error detection signal is not output from the false lead-in detection circuit 13. However, it may be configured to output a signal indicating that a data pattern such as a normal frame synchronization word is detected. At this time, the frequency error detection circuit 4 detects the frequency error of the reproduced carrier from the frequency data or the symbol phase data output from the demodulator 3, and the oscillation frequency of the reference oscillator 6 is compensated by the control signal from the reference oscillator control circuit 5. To do.

In the present embodiment, the frequency pull-in detection circuit 13 is used at the beginning of the frequency stabilizing operation so that the frequency can be stabilized even when the frequency error of the intermediate frequency is outside the tracking range of the demodulator 3. The output frequency error detection signal is monitored, and if a large frequency error is detected here, the reference oscillator control circuit 5 generates a compensation signal so that the demodulator 3 can follow the error range. After that, the carrier frequency error is detected with high accuracy from the frequency data or the symbol phase data output from the demodulator 3, and the oscillation frequency of the reference oscillator 6 is controlled to stabilize the frequency.

As described above, the present embodiment is capable of highly accurate frequency stabilizing operation even for a wider range of frequency errors.

FIG. 7 shows a modification of the fifth embodiment. This example differs from the fifth embodiment in that the frequency carrier is measured by the frequency counter 11 instead of obtaining the frequency error from the frequency data or the symbol phase data from the demodulator 3.

As in the fifth embodiment, the received modulated wave is frequency-converted into an intermediate frequency signal by the receiving circuit 2 and input to the demodulator 3. The demodulator 3 outputs the demodulated data and the reproduced carrier wave. The demodulated data output from the demodulator 3 is input to the false lead-in detection circuit 13.

When the frequency error of the intermediate frequency signal is large, the erroneous pull-in detection circuit 13 outputs a frequency error detection signal, and the reference oscillator control circuit 5 compensates the frequency of the reference oscillator 6 based on this frequency error detection signal. I do. Also,
When the frequency error is small, the false error detection circuit 13 does not output the frequency error detection signal. However, it may be configured to output a signal indicating that a data pattern such as a normal frame synchronization word is detected. At this time, the frequency of the reproduced carrier wave is measured by the frequency counter 11, the frequency error is detected by the frequency error detection circuit 4 from the measured value, and the oscillation frequency of the reference oscillator 6 is compensated by the reference oscillator control circuit 5.

In this embodiment, the frequency error detection signal output from the erroneous pull-in detection circuit 13 is monitored, and if a large frequency error is detected here, the demodulator 3 is allowed to follow the error range. Then, the reference oscillator control circuit 5 generates a compensation signal. After that, the frequency error of the reproduced carrier wave output from the demodulator 3 is measured with high accuracy using the frequency counter 11, and the oscillation frequency of the reference oscillator 6 is controlled to stabilize the frequency.

Also in this case, similarly to the fifth embodiment, it is possible to perform a highly accurate frequency stabilizing operation against a wide range of frequency errors.

[0063]

As described above, the mobile wireless device of the present invention can accurately measure the error of the carrier frequency by obtaining the frequency error from the control data for reproducing the carrier, and the oscillation frequency of the reference oscillator. Can be stabilized with the same accuracy as that of a stable base station transmission wave. Further, since the reproduced carrier frequency error can be detected without using a frequency counter, the circuit can be downsized and the high-speed frequency can be stabilized.

When the frequency error is detected from the rotation amount of the symbol phase using the symbol phase data of the received modulated wave output from the demodulator, the reproduced carrier frequency error can be detected without using the frequency counter. It is possible to downsize the circuit and stabilize the high-speed frequency.

When either the frequency of the intermediate frequency signal or the data from the demodulator is selected and used to detect the frequency error, the frequency error of the reference oscillator that exceeds the tracking range of the demodulator is detected. However, highly accurate frequency stabilization is possible. That is, first, the oscillation frequency of the reference oscillator is controlled so that the frequency error can be tracked by the demodulator based on the measurement result of the frequency error of the intermediate frequency signal, and then the frequency error is detected and compensated from the reproduced carrier data. be able to.

Similarly, when one of the intermediate frequency signal and the reproduction carrier frequency is selected and measured by the frequency counter, the frequency range in which the demodulator can follow is first determined from the measurement result of the frequency error of the intermediate frequency signal. Then, the oscillation frequency of the reference oscillator is controlled, and then the reproduced carrier frequency is measured by the frequency counter to detect the frequency error. This enables highly accurate frequency stabilization even with respect to the frequency error of the reference oscillator that exceeds the tracking range of the demodulator.

Further, when the magnitude and direction of the frequency error are determined by utilizing the fact that the pattern conversion of the demodulated data due to the false pulling occurs when the frequency error of the reference oscillator exceeds the tracking range of the demodulator, the demodulation is performed. It is possible to stabilize the frequency with high accuracy even if the frequency error exceeds the tracking range of the instrument.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a mobile wireless device according to a first embodiment of the present invention.

FIG. 2 is a block configuration diagram showing an example of a carrier recovery circuit provided in a demodulator.

FIG. 3 is a block diagram showing a mobile wireless device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a mobile wireless device according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a mobile wireless device according to a fourth embodiment of the present invention.

FIG. 6 is a block configuration diagram showing a mobile wireless device according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a modification of the fifth embodiment.

FIG. 8 is a block diagram showing a conventional mobile wireless device.

FIG. 9 is a diagram showing a configuration example of a modulation circuit.

[Explanation of symbols]

 1 Antenna 2 Reception Circuit 3 Demodulator 4 Frequency Error Detection Circuit 5 Reference Oscillator Control Circuit 6 Reference Oscillator 7 Frequency Synthesizer 8 Modulation Circuit 9 Power Amplifier 10 Noise Elimination Circuit 11 Frequency Counter 12 Signal Selection Circuit 13 False Pull Detection Circuit 31 Detector 32 Control circuit 33 Fixed oscillator 34 Variable frequency divider 81 Modulation input terminal 82 Angle modulator 83 Local oscillation signal input terminal 84 Mixer 85 Modulation output terminal

Claims (5)

[Claims] 1. A receiver circuit for receiving an angle-modulated digital radio signal and outputting an intermediate frequency signal, a demodulator for demodulating the received signal from the intermediate frequency signal, and a local oscillation frequency for the receiver circuit. A frequency synthesizer, a reference oscillator that generates a signal that serves as a frequency reference for this frequency synthesizer, and a frequency error that detects the frequency error superimposed on the intermediate frequency signal via the frequency synthesizer due to the oscillation frequency error of this reference oscillator. The demodulator comprises a detection means and a reference frequency control means for controlling the oscillation frequency of the reference oscillator based on the output of the frequency error detection means, and the demodulator includes a carrier recovery circuit for reproducing the carrier of the intermediate frequency signal. In the wireless device, the frequency error detecting means is a control unit for reproducing a carrier wave in the carrier wave reproducing circuit. Mobile radio, characterized in that it comprises means for determining a frequency error from the data. 2. A receiving circuit that receives an angle-modulated digital radio signal and outputs an intermediate frequency signal, a demodulator that demodulates the received signal from the intermediate frequency signal, and a local oscillation frequency is supplied to the receiving circuit. A frequency synthesizer, a reference oscillator that generates a signal that serves as a frequency reference for this frequency synthesizer, and a frequency error that detects the frequency error superimposed on the intermediate frequency signal via the frequency synthesizer due to the oscillation frequency error of this reference oscillator. The demodulator includes detection means and reference frequency control means for controlling the oscillation frequency of the reference oscillator based on the output of the frequency error detection means. The demodulator detects the intermediate frequency signal and outputs symbol phase data. In the mobile radio device including a detector, the frequency error detection means is a symbol phase detector output by the detector. Mobile radio, characterized in that it comprises means for determining a frequency error from the data. 3. A receiver circuit for receiving an angle-modulated digital radio signal and outputting an intermediate frequency signal, a demodulator for demodulating the received signal from the intermediate frequency signal, and a local oscillation frequency for the receiver circuit. A frequency synthesizer, a reference oscillator that generates a signal that serves as a frequency reference for this frequency synthesizer, and a frequency error that detects the frequency error superimposed on the intermediate frequency signal via the frequency synthesizer due to the oscillation frequency error of this reference oscillator. The demodulator comprises a detection means and a reference frequency control means for controlling the oscillation frequency of the reference oscillator based on the output of the frequency error detection means, and the demodulator includes a carrier recovery circuit for reproducing the carrier of the intermediate frequency signal. In the wireless device, the demodulator is control data for carrier recovery in the carrier recovery circuit. Includes means for outputting frequency data obtained from the control data, and the frequency error detecting means includes a frequency counter for measuring the frequency of the intermediate frequency signal, and count value data output by the frequency counter and the means for outputting. And a means for selecting a frequency error from the selected data. 4. A receiving circuit that receives an angle-modulated digital radio signal and outputs an intermediate frequency signal, a demodulator that demodulates the received signal from the intermediate frequency signal, and a local oscillation frequency is supplied to the receiving circuit. A frequency synthesizer, a reference oscillator that generates a signal that serves as a frequency reference for this frequency synthesizer, and a frequency error that detects the frequency error superimposed on the intermediate frequency signal via the frequency synthesizer due to the oscillation frequency error of this reference oscillator. The demodulator includes detection means and reference frequency control means for controlling the oscillation frequency of the reference oscillator based on the output of the frequency error detection means. The demodulator detects the intermediate frequency signal and outputs symbol phase data. In the mobile radio device including the demodulator, the demodulator is the symbol phase data or the symbol phase thereof. The frequency error detecting means includes a frequency counter for measuring the frequency of the intermediate frequency signal, the count value data output by the frequency counter, and the data from the outputting means. And a means for determining a frequency error from the data by selecting one of the two. 5. A receiver circuit for receiving an angle-modulated digital radio signal and outputting an intermediate frequency signal, a demodulator for demodulating the received signal from the intermediate frequency signal, and a local oscillation frequency for the receiver circuit. A frequency synthesizer, a reference oscillator that generates a signal that serves as a frequency reference for this frequency synthesizer, and a frequency error that detects the frequency error superimposed on the intermediate frequency signal via the frequency synthesizer due to the oscillation frequency error of this reference oscillator. The demodulator comprises a detection means and a reference frequency control means for controlling the oscillation frequency of the reference oscillator based on the output of the frequency error detection means, and the demodulator includes a carrier recovery circuit for reproducing the carrier of the intermediate frequency signal. In the wireless device, the frequency error detecting means is configured to detect the intermediate frequency signal output from the receiving circuit and the carrier. And a means for selecting one of the reproduced carrier wave signals output from the reproducing circuit, a frequency counter for measuring the selected signal frequency, and means for obtaining the oscillation frequency error of the reference oscillator from the count value of the frequency counter. Mobile radio characterized by.