JP3153671B2 - Mobile radio - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for digital mobile radio communication using angle modulation. In particular, the present invention relates to a mobile wireless device suitable for a communication system in which carrier drift needs to be kept small. The present invention is suitable for use in digital mobile radio communication in the UHF band.

[0002]

2. Description of the Related Art When communication is performed by angle modulation, transmission quality is significantly degraded if there is a carrier drift. As for the transmission characteristics in the pass band, characteristic degradation such as distortion of transmission signals, degradation of frequency characteristics, and degradation of error rate occurs. Further, in the out-of-band transmission characteristics, the leakage power to adjacent channels increases. In order to prevent this, (1) the channel arrangement should be of a sufficiently wide interval compared to the transmission bandwidth,
Either (2) increasing the stability of a local oscillator or a modulator causing carrier drift, or (3) detecting carrier drift and automatically adjusting to a desired carrier frequency.

[0003] However, in the method (1), considering that the effective radio frequency is increasingly limited with the increase in the traffic volume in the future, a communication method for allocating one radio frequency to one communication channel in particular. Then, it is difficult to arrange the channels at wide intervals. Also in multiplex communication and other communication systems that require a wide transmission band, narrowing of the transmission bandwidth by multi-level modulation and other technologies has been promoted due to the recent tightness of radio frequency, and margin of carrier wave drift has been realized. It is difficult to widen the radio channel interval to achieve this.

The method (2) does not pose a problem when a highly stable oscillator can be used as in a fixed wireless communication system. However, a problem arises when a small and simple mobile radio is required as in a mobile communication system. In general, mobile radios use a crystal oscillator that stably oscillates at a relatively low frequency as a reference oscillator and apply phase synchronization to a voltage-controlled oscillator to obtain a signal at a carrier band frequency, or
One or a plurality of local oscillation signals are generated by directly oscillating a carrier wave whose phase is synchronized by a direct digital synthesizer. 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)
ure Compensated Crystal Oscillator) is known. However, in consideration of mass production under the constraint of equipping the mobile communication device, the practical stability is considered to be about 1.5 to 2 ppm as a limit. In addition, a change in temperature of the oscillation frequency of the crystal is stored in a memory, and a crystal oscillator (DTCXO: Digitall) that performs frequency control by controlling a capacitance array based on temperature information from a temperature detection element.
y Temperature Compensated Crystal Oscillator) has also been put to practical use, and it has become possible to reduce the compensation accuracy for temperature changes to 0.5 ppm or less. However, none of the oscillators can compensate the oscillation frequency for aging. As the method (3), a method of synchronizing a local oscillator with a received wave having high frequency accuracy is generally used. In the case of mobile communication using the analog angle modulation method, the carrier frequency error is detected by measuring the frequency of the intermediate frequency signal with a frequency counter, and the local oscillation frequency is controlled so that the error becomes a predetermined value or less. I do.
However, in the case of the digital angle modulation method, the carrier frequency is shifted due to the phase shift of each symbol depending on the pattern of data to be transmitted, and an error may occur in the measurement by the counter. As a technique for solving this, Japanese Patent Application No. 5-63762 (not disclosed at the time of filing of the present application) discloses that the frequency of a carrier reproduced by a demodulator is counted by a frequency counter to accurately measure the frequency drift of an intermediate frequency signal. Techniques are shown. This technique is described below.

FIG. 11 is a block diagram showing a conventional example of a mobile wireless device provided with a frequency stabilizing function for use in mobile communication using digital angle modulation.

A base station transmission wave having a stable frequency is transmitted to an antenna 1
The frequency is converted into an intermediate frequency signal by the receiving circuit 2 and the intermediate frequency signal is demodulated by the demodulator 3 of the synchronous detection waveform or the adaptive synchronization detection waveform. At this time, the reproduced carrier of the demodulator 3 follows the frequency of the intermediate frequency signal on which the frequency error is superimposed. Therefore, the reproduced carrier frequency of the demodulator 3 is measured by the frequency counter 4. The carrier recovery circuit in the demodulator 3 follows the frequency drift of the intermediate frequency signal and functions as a kind of narrow band filter, averaging the instantaneous frequency fluctuation due to the modulation component. Therefore, the frequency drift of the intermediate frequency signal can be accurately measured from the count value of the frequency counter 4.

As an operation clock of the frequency counter 4, for example, an output of a fixed oscillator provided in the demodulator 3 is used. This fixed oscillator is for reproducing a carrier wave in the demodulator 3 and for generating a signal serving as a phase reference for demodulation whose phase is substantially synchronized with the carrier wave. Since the frequency is not so high, even a relatively inexpensive one is used. Sufficient accuracy and stability are obtained.

The count value of the frequency counter 4 is input to a frequency error detection circuit 5. The frequency error detection circuit 5
This count value is compared with a preset intermediate frequency signal frequency to detect a frequency error. The detected frequency error is input to the reference oscillator control circuit 6. The reference oscillator control circuit 6 generates a frequency error compensation signal for compensating the frequency error, inputs the signal to the reference oscillator 7, and outputs the oscillation frequency of the reference oscillator 7 until the frequency error becomes equal to or less than a predetermined value. Control.

The reference oscillator 7 thus stabilized
Are supplied to one or a plurality of frequency synthesizers 8 provided. The output of the frequency synthesizer 8 is used as a local oscillation signal for converting the frequency of a received wave in the receiving circuit 2 and also as a local oscillation signal for converting the frequency of a transmission signal into a radio frequency in the modulation circuit 9. . The output of the modulation circuit 9 is
The signal is transmitted to the wireless section via the power amplifier 10. By sharing the frequency synthesizer 8 as the local oscillator of the modulation circuit 9, the transmission frequency of the mobile radio can be stabilized to the same degree as the stable base station transmission frequency accuracy.

FIG. 12 shows a configuration example of the modulation circuit 9. A baseband digital signal is input to the modulation input terminal 91, and the angle modulator 92 generates an angle modulation signal based on this signal. A local oscillation signal from the frequency synthesizer 8 is input to a local oscillation signal input terminal 93, and the
4 converts the frequency of the output of the angle modulator 92 to a desired carrier frequency and outputs it to a modulation output terminal 95. Here, the case where the local oscillation signal input terminal 93, the mixer 94, and the frequency synthesizer 8 have a single-stage configuration has been described, but these may be configured in a multi-stage configuration, and a desired carrier frequency may be obtained by sequentially performing frequency conversion. In addition, a local oscillation signal having a desired carrier frequency can be directly modulated.

[0012]

In the above-mentioned conventional example,
By counting the number of reproduced carriers output from the demodulator by the frequency counter, it was possible to stabilize the frequency with high accuracy for a limited range of frequency error. However, TCXOs that can be installed in mobile radios are subject to significant restrictions on parts cost, size, and other factors, and there is a limit to improving frequency stability. The frequency synthesizer as a local oscillator
Since oscillation occurs in synchronization with TCXO, the frequency error increases as the carrier frequency increases. Therefore, if the phase rotation of the received modulated wave reaches a level indistinguishable from the original modulation phase transition, it exceeds the range of the frequency drift that the demodulator can follow, and the data cannot be demodulated normally. Would. For this reason, the conventional reference oscillator control has a problem that a predetermined frequency stability cannot be obtained as the carrier frequency increases.

For example, in the case of QPSK modulation with a bit rate f _b , phase inversion within one symbol time cannot follow a frequency drift exceeding ± π / 4 radians, ie, f _b / 16 [Hz]. This value is f _b is 40kbi
About 2.5k for QPSK transmission system of about t / sec
Hz. This is equivalent to 1.7 ppm in terms of frequency stability required for a reference oscillator of a mobile radio device used in a relatively high carrier frequency, for example, a 1.5 GHz band.

Considering temperature characteristics, power supply voltage characteristics, and long-term stability due to aging, the TCXO used for the reference oscillator secures a frequency stability of 1.7 ppm or less while maintaining a low frequency required for a mobile radio. It is difficult to satisfy all characteristics such as cost, small size and light weight, and low power consumption. For this reason, it has been desired to expand the frequency error compensation range so that the allowable value of the frequency stability with respect to the reference oscillator can be relaxed.

For example, if a plurality of demodulators and fixed oscillators are used, each demodulator is operated at a different phase reference signal frequency, and a frequency stabilizing function is added to each, a frequency error detection range can be expanded over a wide range as a whole. .
However, considering operation to a mobile wireless device, it is difficult to realize the circuit size and power consumption.

The present invention solves the above problems and provides a mobile radio capable of expanding the error correction range of the reference oscillator and performing stable transmission and reception even when the oscillation frequency error of the reference oscillator is not so small. The purpose is to:

[0017]

SUMMARY OF THE INVENTION A mobile radio according to the present invention comprises:
A receiving circuit that receives an angle-modulated digital radio signal and outputs an intermediate frequency signal, a frequency synthesizer that supplies a local oscillation frequency to the receiving circuit, and a reference oscillator that generates a signal that is a frequency reference of the frequency synthesizer. A demodulator that reproduces a carrier from the intermediate frequency signal output from the receiving circuit and demodulates the received signal using a signal whose phase is substantially synchronized with the carrier as a phase reference signal; In a mobile radio having means for detecting the frequency error of the reference oscillator from the information and means for controlling the oscillation frequency of the reference oscillator based on the output of the means for detecting, the reliability of demodulated data output from the demodulator is reduced. Data monitoring means for monitoring the demodulation data, and a phase reference signal when the data monitoring means detects a decrease in the reliability of the demodulated data. Characterized by comprising a means for adding an offset to the frequency.

The data monitoring means preferably includes means for detecting a synchronization word of the received data frame and monitoring the detection rate.

As information on the frequency of the reproduced carrier, not only the frequency is counted and used, but also control data for carrier recovery in the demodulator may be used, and the symbol phase data of the received modulated wave may be used. You may.

A plurality of demodulators are provided, the data monitoring means monitors demodulated data for at least a part of the plurality of demodulators, and the means for adding an offset includes a frequency of a phase reference signal in at least a part of the plurality of demodulators. May be configured to add offsets different from each other. Briefly, two demodulators are provided, with one of the demodulators having an offset of zero and monitoring the reliability of the demodulated data, and adding a fixed offset to the phase reference signal frequency of the other demodulator. When the reliability of demodulated data from a demodulator having an offset of zero is high, the demodulator can be selected, and when the reliability decreases, the other demodulator can be selected.

Instead of adding an offset to the phase reference signal frequency of the demodulator, an offset can be added to the frequency reference of the frequency synthesizer.

[0022]

The frequency error detection range is changed by adding an offset to the frequency of the phase reference signal of the demodulator. Therefore, one demodulator equivalently operates as a plurality of demodulators having different frequency error detection ranges. Further, the offset amount is switched in time series based on the reliability of the demodulated data, and when an appropriate frequency offset is added,
The frequency of the reproduced carrier signal output from the demodulator is measured to detect an oscillating frequency error of the reference oscillator, and the oscillating frequency is controlled so as to reduce the oscillating frequency error. As a result, the frequency error detection range and the frequency compensation range can be expanded without increasing the circuit scale and power consumption, and a mobile radio having high-precision frequency stability can be realized.

When a plurality of demodulators are provided and an offset is added to the phase reference signal frequency of at least one of the demodulators, the plurality of demodulators can be operated in parallel in mutually different frequency error detection ranges. An appropriate demodulator is selected based on the reliability of demodulated data output from one or more of the plurality of demodulators, and the oscillation frequency of the reference oscillator is controlled by the reproduction carrier signal frequency of the selected demodulator. I do. As a result, the frequency error detection range and the frequency compensation range can be expanded, and a mobile radio having high-precision frequency stability can be realized.

When an offset is added to the frequency of the reference oscillator, which is the frequency reference of the frequency synthesizer, the intermediate frequency signal frequency of the received wave can be changed. This offset amount is switched in time series based on the reliability of the demodulated data, and when an appropriate frequency offset is added, the oscillation frequency error of the reference oscillator is detected from the output of the demodulator, and this oscillation frequency error decreases. The oscillation frequency of the reference oscillator is controlled as described above. As a result, the frequency error detection range and the frequency compensation range can be expanded without increasing the circuit scale and power consumption, and a mobile radio having high-precision frequency stability can be realized.

[0025]

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

The mobile radio device includes a receiving circuit 2 for receiving an angle-modulated digital radio signal by an antenna 1 and outputting an intermediate frequency signal, a frequency synthesizer 8 for supplying a local oscillation frequency to the receiving circuit 2, A carrier is reproduced from a reference oscillator 7 for generating a signal serving as a frequency reference of the frequency synthesizer 8 and an intermediate frequency signal output from the receiving circuit 2, and a signal whose phase is substantially synchronized with the carrier is used as a phase reference signal to generate a received signal. A frequency counter 4 and a frequency error detection circuit 5 as means for detecting a frequency error of the reference oscillator from information on the frequency of the carrier reproduced by the demodulator 3; A reference oscillator control circuit 6 is provided as means for controlling the oscillation frequency of the reference oscillator based on the output of the reference oscillator. The mobile wireless device further includes a modulation circuit 9 for performing modulation using an output of the frequency synthesizer 8 as a carrier, and a power amplifier 10 for amplifying the power of the modulated wave.

The feature of the present embodiment is that a demodulation data monitoring circuit 11 for monitoring the reliability of demodulation data output from the demodulator 3 is provided.
Detects that the demodulated data has decreased in reliability.
The reference signal control circuit 12 is provided as a means for adding an offset to the frequency of the phase reference signal within the reference signal.

The demodulator 3 demodulates the intermediate frequency signal on the basis of the phase of the phase reference signal and compensates for the frequency error of the phase reference signal with respect to the intermediate frequency signal based on the detected phase data, as in the conventional example. It has a feedback loop that performs This phase reference signal contains a reproduced carrier signal component, which is output to the outside.

Hereinafter, the operation of the mobile radio device of the present embodiment will be described.

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 7 is superimposed. If this frequency error is within the tracking range of the demodulator 3, the frequency of the reproduced carrier follows the intermediate frequency signal on which the frequency error is superimposed.

The reference signal control circuit 12 inputs the reference signal control data to the demodulator 3 and sets, as an initial state, the phase reference signal in the demodulator 3 so as to correspond to a predetermined frequency of the intermediate frequency signal. . The demodulated data output from the demodulator 3 is input to the demodulated data monitoring circuit 11.

As the demodulated data monitoring circuit 11, for example, a synchronization word detection circuit for detecting the synchronization timing of a data frame generally provided in a digital communication radio can be used. When the frequency error of the reference oscillator 7 is so large that the carrier recovery circuit in the demodulator 3 cannot follow, a remarkable error occurs in the demodulated data.
The detection rate of the synchronization word is extremely reduced. Therefore, the reliability of the demodulated data can be determined by using the synchronization word detection circuit.

After the synchronization word detection confirms that the demodulated data is reliable and that carrier recovery is being performed within the tracking range of the demodulator 3, the frequency of the reproduced carrier output from the demodulator 3 is determined. Is measured by the frequency counter 4. If no sync word is detected, the demodulator 3
In order to offset the phase reference signal frequency, the reference signal control circuit 12 inputs the reference signal control data to the demodulator 3, and detects the synchronization word again.

Here, the data output from the reference signal control circuit 12 for offsetting the phase reference signal frequency includes the frequency error tracking range in the demodulator 3 when the initial value is input and the frequency error tracking after the offset. It is preferable to set a value obtained by overlapping a part of the range. That is, by offsetting the frequencies so that the frequency error detection ranges of the two are continuous, the instability of the carrier wave recovery operation at the limit frequency of the tracking range of the demodulator 3 can be removed.

The frequency error detection circuit 5 compares the output of the frequency counter 4 with a predetermined intermediate frequency signal frequency to detect a frequency error. The detection output is supplied to the reference oscillator control circuit 6. The reference oscillator control circuit 6 generates a frequency error compensation signal for compensating the frequency error, inputs the signal to the reference oscillator 7, and adjusts the oscillation frequency of the frequency reference signal until the frequency error becomes equal to or less than a predetermined value. Control and perform stabilization operation.

TC generally used as reference oscillator 7
The tendency of the oscillating frequency of the XO over time and the tendency of the oscillating frequency error in the environment where the mobile radio is actually used can be known in advance from the TCXO characteristic table and the like. Therefore, the time required for frequency stabilization is reduced by setting the frequency offset amount by the reference signal control circuit 12 and controlling whether the oscillation frequency is increased or decreased from the initial value. Can be. Furthermore, the compensation signal for the oscillation frequency error given to the reference oscillator 7 can be stored and used as an initial value in the next frequency stabilization operation. In order to further reduce the time required for frequency stabilization, the reference oscillator 7 is used in the past frequency stabilization operation.
May be stored, and their average value or the most frequent value may be used as an initial value or a set value of the offset amount during the frequency stabilization 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 output from the demodulator 3 is not affected by the modulated data sequence.
By offsetting the phase reference signal frequency for demodulation to a different frequency, the phase reference for demodulation of one demodulator 3 is changed in time series, and a plurality of demodulators having different frequency detection ranges are equivalently changed. Has been realized. For this reason,
It is possible to detect and compensate for a frequency error over a wider frequency range than before.

The demodulator 3 and the frequency counter 4 for stabilizing the frequency, the frequency error detection circuit 5, the reference oscillator control circuit 6, the demodulation data monitoring circuit 11 and the reference signal control circuit 12 can all be constituted by logic circuits. LSI integration is easy. Therefore, miniaturization, low power consumption, and no adjustment are possible, which is suitable for a mobile wireless device.

FIG. 2 shows a configuration example of the demodulator 3. This configuration example is disclosed in JP-A-2-205940 and JP-A-2-2-2.
No. 19747, which discloses a direct phase quantization circuit 31, an adaptive carrier synchronization data generation circuit 32,
Frequency drift detection circuit 33, digital oscillator 34,
A fixed oscillator 35, an identification circuit 36 and a clock recovery circuit 37 are provided. The output of the reference oscillator 7 can be used as the fixed oscillator 35.

The digital oscillator 34 divides the frequency of the output signal of the fixed oscillator 35 and supplies it directly to the phase quantization circuit 31 as a phase reference signal. The phase reference signal contains a reproduced carrier component. The direct phase quantization circuit 31 converts the received angle-modulated signal input to the demodulator 3 into a digital oscillator 3
4 is quantized by the phase reference signal. Identification circuit 36
Performs demodulation of received data from the quantized phase data.

This demodulator also includes two feedback loops to obtain a highly accurate phase reference signal. The first feedback loop includes a direct phase quantization circuit 31, a frequency drift detection circuit 33, and a digital oscillator. The second feedback loop includes a direct phase quantization circuit 31, an adaptive carrier synchronization data generation circuit 32, and a digital oscillator.

The first feedback loop is a system that functions when a frequency error occurs between the carrier frequency of the angle-modulated wave and the frequency of the phase reference signal. The operation will be described with reference to FIGS. 3 to 6 taking the case of QPSK modulation as an example. A signal obtained by directly phase-quantizing an intermediate frequency signal obtained by frequency-converting a received wave is indicated by four phase points as shown in FIG. 3 in a signal space at the identification timing. When there is a frequency error between the phase reference signal and the carrier of the angle-modulated wave, as shown in FIG. 4, the phase of the angle-modulated wave is always rotated in one direction and detected. This rotation angle θ
Is proportional to the frequency error, so the direct phase quantization circuit 31
Is converted into a numerical value, and the frequency drift detection circuit 33 and the digital oscillator 34 integrate the obtained θ value for a certain period of time and control the frequency of the phase reference signal by the average amount. The carrier recovery circuit including the frequency drift detection circuit 33 and the digital oscillator 34 follows the frequency drift of the intermediate frequency signal and functions as a kind of narrow band filter to average the instantaneous frequency fluctuation due to the modulation component. Therefore, if the reproduction carrier frequency is measured, the frequency drift of the intermediate frequency signal with respect to the predetermined frequency can be accurately detected.

However, when the rotation angle θ caused by the frequency error exceeds π / 4 [rad], as shown in FIG. 5, it is recognized that the rotation angle θ ^* is added to the phases of the different quadrants. Therefore, correct frequency error detection becomes impossible.

The second feedback loop is a loop for instantly controlling the phase of the phase reference signal in the digital oscillator 34 when the carrier phase of the intermediate frequency signal fluctuates instantaneously due to fading or the like. As shown in FIG. 6, the operation is such that relative phase data detected at each identification timing is degenerated into the first quadrant, and the instantaneous phase variation angle φ is detected depending on which area the transmitted modulation signal is located in. Is done. An operation of shifting the phase of the phase reference signal from the detected instantaneous phase variation angle φ by the variation angle φ is realized by the direct phase quantization circuit 31, the adaptive carrier synchronization data generation circuit 32, and the digital oscillator. Thereby, the phase of the phase reference signal can be made to follow the random instantaneous phase fluctuation of the received carrier wave due to fading.

In this embodiment, an example in which an adaptive synchronous detection waveform demodulator is used as the demodulator 3 has been described. However, the present invention can be similarly implemented using a synchronous detection waveform demodulator.

FIG. 7 is a block diagram showing a mobile radio device according to a second embodiment of the present invention. This embodiment differs from the first embodiment in that control data for carrier recovery is used as information on the frequency of the recovered carrier.

That is, in the carrier recovery circuit in the demodulator 3, when the reproduction carrier frequency is changed by changing the frequency division ratio of the variable frequency divider constituted by the logic circuit, the frequency division ratio is set. Since the output frequency is uniquely determined for the control data to be performed, the control data can be extracted as frequency data, and the frequency drift of the intermediate frequency signal with respect to a predetermined frequency can be detected. Specifically, the frequency data input to the digital oscillator 34 of the demodulator shown in FIG. 2, that is, the output of the adaptive carrier synchronization data generation circuit 32 and the output of the frequency drift detection circuit 33 are used.

In this case, the frequency counter 4 in the first embodiment becomes unnecessary, and the frequency data output from the demodulator 3 is directly supplied to the frequency error detection circuit 5. The frequency error detection circuit 5 detects a frequency error with respect to a predetermined intermediate frequency signal frequency based on the frequency data. The frequency error detected by the frequency error detection circuit 5 is input to the reference oscillator control circuit 6. The reference oscillator control circuit 6 generates a frequency error signal for compensating for the frequency error, inputs the signal to the reference oscillator 7, and controls the oscillation frequency of the reference oscillator 7 until the frequency error becomes equal to or less than a predetermined value. Stabilize.

In this embodiment, there is no need to measure the reproduced carrier frequency using a frequency counter, so that a high-speed frequency stabilizing operation can be performed. Furthermore, since a frequency counter is not required, there is an advantage that the circuit scale can be reduced.

FIG. 8 is a block diagram showing a mobile radio device according to a third embodiment of the present invention. This embodiment differs from the first and second embodiments in that the symbol phase data of the received modulated wave is used as the information on the frequency of the reproduced carrier.

That is, the symbol phase data obtained by detecting the reception modulation wave from the demodulator 3 is taken out and inputted to the frequency error detection circuit 5, and the frequency error with respect to the predetermined intermediate frequency signal frequency is detected from the phase rotation amount.
The demodulator 3 may be any demodulator capable of outputting symbol phase data at the time of detection, and may be any of a synchronous detection waveform, an adaptive synchronization detection waveform, and a delay detection waveform. For example, when the adaptive synchronous detection demodulator shown in FIG.
Get the output of

The following frequency stabilizing operation is the same as in the first and second embodiments. The frequency error detected by the frequency error detecting circuit 5 is input to the reference oscillator control circuit 6,
The reference oscillator control circuit 6 generates a frequency error signal for compensating for the frequency error, inputs the frequency error signal to the reference oscillator 7, and controls the oscillation frequency of the reference oscillator 7 until the frequency error becomes equal to or less than a predetermined value.

In this embodiment, as in the second embodiment, it is not necessary to measure the reproduced carrier frequency using a frequency counter, so that a high-speed frequency stabilizing operation can be performed. There is an advantage that can be reduced.

FIG. 9 is a block diagram showing a mobile radio device according to a fourth embodiment of the present invention. This embodiment includes a plurality of demodulators 3-1 and 3-2.
2, a demodulation data monitoring circuit 11 is provided as means for monitoring the demodulation data of the demodulator 3-1 in this example, and the frequency of the phase reference signal of each of the demodulators 3-1 and 3-2 is provided. The difference from the first embodiment is that the reference signal control circuit 13 is connected to the demodulator 3-2 as a means for adding different offsets to the signal. Demodulator 3-1;
3-2 uses a common fixed oscillator, and the reference signal control circuit 13 controls the phase of the demodulator 3-2 so that the detectable frequency ranges of the demodulators 3-1 and 3-2 are continuous. Give a constant frequency offset to the reference signal.

The reception wave received by the antenna 1 is frequency-converted into an intermediate frequency signal by the reception circuit 2 and is demodulated.
1, 3-2. The demodulator 3-2 sets the same intermediate frequency signal to a different phase reference signal frequency from the demodulator 3-1 under the control of the reference signal control circuit 13. The reproduced carrier signals output from the demodulators 3-1 and 3-2 are supplied to the frequency counter 4 via the signal selection circuit 14. In an initial state, the signal selection circuit 14 connects the demodulator 3-1 using the correct phase reference signal frequency to the frequency counter 4.

The demodulated data monitoring circuit 11 includes a demodulator 3-1
, A synchronization word is detected from the demodulated data output, and it is determined whether or not the demodulator 3-1 is performing a normal carrier wave reproducing operation. When the synchronization word is detected, the signal selection circuit 14 is controlled to select the output of the demodulator 3-1.
The frequency counter 4 measures the frequency of the reproduced carrier output from the demodulator 3-1. If the demodulated data monitoring circuit 11 does not detect a synchronization word, the signal selection circuit 1
4, the demodulator 3-2 is selected, and the reproduced carrier signal of the demodulator 3-2 is measured by the frequency counter 4.

The output of the frequency counter 4 is supplied to a frequency error detection circuit 5, which detects a frequency error by comparing with a predetermined intermediate frequency signal frequency. The output signal of the frequency error detection circuit 5 is supplied to a reference oscillator control circuit 6. The reference oscillator control circuit 6 generates a frequency error compensation signal for compensating the frequency error, inputs the signal to the reference oscillator 7, and adjusts the oscillation frequency of the reference oscillator 7 until the frequency error becomes equal to or less than a predetermined value. Control and stabilize.

Here, the case where only one of the two demodulators is monitored and a fixed frequency offset is added to the other has been described. However, both the two demodulators are monitored, and each of them is monitored according to the monitoring result. The frequency offset can be changed in time series. Also, three or more demodulators can be provided. It is also possible to adopt a configuration in which an error of the reproduced carrier frequency of each of the plurality of demodulators is detected. Further, similarly to the second embodiment or the third embodiment, a configuration may be adopted in which a frequency error is detected based on control data or symbol phase data for carrier recovery.

In this embodiment, a plurality of demodulators are operated in different continuous frequency ranges, and an appropriate demodulator is selected based on the reliability of demodulated data output from at least one of the demodulators. Thus, a frequency error can be detected over a wider frequency range than before.

FIG. 10 is a block diagram showing a mobile radio device according to a fifth embodiment of the present invention. This embodiment does not add an offset to the phase reference signal frequency in the demodulator,
The difference from the above embodiment is that an offset is added to the frequency reference of the frequency synthesizer. That is, the reference oscillator control circuit 15 changes the intermediate frequency signal frequency of the received wave by adding an offset to the oscillation frequency of the reference oscillator 7, and the offset amount is used for the reliability of the demodulated data obtained by the demodulated data monitoring circuit 11. The time is switched based on the time series.

The reference oscillator control circuit 15 inputs a reference oscillator control signal corresponding to a predetermined intermediate frequency signal frequency to the reference oscillator 7 as an initial value. The demodulated data output from the demodulator 3 is transmitted to the demodulated data monitoring circuit 1
1 is input.

The detection of the synchronization word in the demodulated data monitoring circuit 11 confirms that the demodulated data has high reliability and that carrier recovery is being performed within the tracking range of the demodulator 3, and then the demodulator 3 outputs The frequency of the reproduced carrier wave is measured by the frequency counter 4. If the synchronization word is not detected, the reference oscillator control circuit 15 outputs a signal for adding an offset to the oscillation frequency to the reference oscillator 7, offsets the intermediate frequency signal frequency input to the demodulator 3, and monitors the demodulated data. The synchronization word is detected again in the circuit 11.

Here, the frequency offset amount by the reference oscillator control circuit 15 is set to be smaller than the frequency error detection range of the demodulator 3 so that a part of the frequency error detection range before and after the offset is overlapped. Is good. That is, by making the frequency error detection ranges of both of them continuous, the instability of the carrier wave recovery operation at the limit value of the tracking range of the demodulator 3 can be eliminated.

The frequency error detection circuit 5 compares the output of the frequency counter 4 with a predetermined intermediate frequency signal frequency to detect a frequency error. The output signal is input to the reference oscillator control circuit 15. The reference oscillator control circuit 15 generates a frequency error compensation signal corresponding to the sum of the offset frequency and the frequency error, and inputs the frequency error compensation signal to the reference oscillator 7 to compensate for the frequency error. The oscillation frequency is controlled until the oscillation frequency falls below the set value.

TC generally used as reference oscillator 7
The tendency of the oscillating frequency of the XO over time and the tendency of the oscillating frequency error in an environment where the mobile radio is actually used can be known in advance from a TCXO characteristic table or the like. Accordingly, in accordance with this, the reference oscillator control circuit 15 controls whether to increase or decrease the oscillation frequency of the frequency offset amount with respect to the initial value.
As a result, the time required for frequency stabilization can be reduced. Furthermore, the compensation signal for the oscillation frequency error given to the reference oscillator 7 can be stored and used as an initial value in the next frequency stabilization operation. Furthermore, in order to shorten the time required for frequency stabilization, the error compensation signals given to the reference oscillator 7 in the past frequency stabilization operation are stored, and the average value or the most frequent value is stored in the frequency stabilization operation. It can also be used as an initial value at the time of the conversion operation or as a set value of the offset amount.

When the appropriate frequency offset is applied to the reference oscillator 7 in this way, the signal output from the demodulator 3 is input to the frequency counter 4 and the frequency error is detected by the frequency error detection circuit 5 based on the count value. And the reference oscillator control circuit 15 controls the oscillation frequency so as to reduce the frequency error. As a result, detection and compensation of a frequency error over a wider frequency range than before can be performed.

In the above description, the configuration in which the reproduced carrier is measured and the frequency error is detected has been described. However, as in the second or third embodiment, the control data for carrier recovery is used as the information on the carrier frequency. Alternatively, symbol phase data can be used.

Further, the demodulator and the frequency counter for realizing the frequency stabilizing function, the frequency error detection circuit 5 and the reference oscillator control circuit 15 can all be constituted by logic circuits, so that it is easy to implement an LSI. Therefore, miniaturization, low power consumption, and no adjustment are possible, which is suitable for a mobile wireless device.

[0069]

As described above, the mobile radio of the present invention is used in a digital mobile communication system using angle modulation, and in the configuration for stabilizing the frequency based on the base station transmission wave, the mobile radio of the present invention is used as a reference. Thus, the oscillation frequency error detection range and the compensation range of the reference oscillator that generates the signal can be expanded. Therefore, even if the oscillation frequency error of the reference oscillator is large, the frequency can be stabilized.

In the present invention, when the frequency of the phase reference signal serving as the phase reference for detection in the demodulator is offset, one demodulator is effectively operated as a plurality of demodulators having different phase reference signal frequencies. be able to. Therefore, the frequency error detection range and the frequency compensation range can be expanded without increasing the circuit scale and the power consumption, and highly accurate frequency stabilization can be realized.

When control data or symbol phase data for carrier recovery in the demodulator is used as information on the frequency of the recovered carrier, a frequency counter is not required. Both the control data and the symbol phase data are data originally generated in the demodulator. The circuit scale can be reduced, and high-speed and high-accuracy frequency stabilization can be realized.

When an offset is added to the phase reference signal frequency of at least a part of the demodulators by using a plurality of demodulators, the plurality of demodulators can be operated in parallel with the phase references of different frequencies, so that high-speed operation is possible. And high-precision frequency stabilization can be realized.

When an offset is added to the frequency of a signal serving as a reference for the transmission / reception frequency, the frequency error detection range and the frequency compensation range can be expanded without increasing the circuit scale and power consumption, thereby achieving high-precision frequency stabilization. realizable.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing an example of a demodulator.

FIG. 3 is a diagram showing a symbol phase at an identification timing.

FIG. 4 is a diagram showing phase rotation when a frequency error exists between a phase reference signal and a carrier of an angle-modulated wave.

FIG. 5 shows that the rotation angle θ caused by the frequency error is π / 4
FIG.

FIG. 6 is a diagram showing a state in which relative phase data detected for each identification timing is degenerated into a first quadrant.

FIG. 7 is a block diagram showing a mobile radio device according to a second embodiment of the present invention.

FIG. 8 is a block diagram showing a mobile radio device according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing a mobile radio device according to a fourth embodiment of the present invention.

FIG. 10 is a block diagram showing a mobile radio device according to a fifth embodiment of the present invention.

FIG. 11 is a block diagram showing a conventional mobile radio device.

FIG. 12 illustrates a configuration example of a modulation circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 reception circuit 3, 3-1, 3-2 demodulator 4 frequency counter 5 frequency error detection circuit 6, 15 reference oscillator control circuit 7 reference oscillator 8 frequency synthesizer 9 modulation circuit 10 power amplifier 11 demodulation data monitoring circuit 12, 13 Reference Signal Control Circuit 14 Signal Selection Circuit 31 Direct Phase Quantization Circuit 32 Adaptive Carrier Synchronization Data Generation Circuit 33 Frequency Drift Detection Circuit 34 Digital Oscillator 35 Fixed Oscillator 36 Identification Circuit 37 Clock Regeneration Circuit 91 Modulation Input Terminal 92 Angle Modulator 93 Local Oscillation signal input terminal 94 Mixer 95 Modulation output terminal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-244247 (JP, A) JP-A-64-49355 (JP, A) JP-A-63-286043 (JP, A) 291787 (JP, A) JP-A-5-244209 (JP, A) JP-A-5-37578 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 27/22 H04B 1 /Ten

Claims (5)

(57) [Claims] 1. A receiving circuit that receives an angle-modulated digital radio signal and outputs an intermediate frequency signal, a frequency synthesizer that supplies a local oscillation frequency to the receiving circuit, and a signal that is a frequency reference of the frequency synthesizer. By generating a reference oscillator and reproducing a carrier from the intermediate frequency signal output from the receiving circuit, and quantizing the phase of the intermediate frequency signal using a signal whose phase is substantially synchronized with the carrier as a phase reference signal .
Ri and demodulator for demodulating the received signal, means for detecting a frequency error of the reference oscillator from the information on the frequency of the carrier wave reproduced by the demodulator, the oscillation frequency of the reference oscillator on the basis of the output of the means for the detection A data monitoring means for monitoring the reliability of demodulated data output from the demodulator, and the data monitoring means detects a decrease in the reliability of the demodulated data when the data monitoring means detects a decrease in the reliability of the demodulated data. Means for adding an offset to the frequency of the phase reference signal. 2. The mobile radio according to claim 1, wherein said data monitoring means includes means for detecting a synchronization word of a received data frame and monitoring the detection rate. 3. The mobile radio according to claim 1, wherein the information on the frequency of the reproduced carrier is control data for carrier recovery in the demodulator. 4. The information on the frequency of the reproduced carrier wave is symbol phase data of a received modulated wave.
Or the mobile wireless device according to 2. 5. A data processing apparatus comprising: a plurality of demodulators; wherein the data monitoring means monitors demodulated data of at least a part of the plurality of demodulators; 5. The mobile radio according to claim 1, further comprising means for adding different offsets to the frequency of the phase reference signal in at least a part thereof.