JPH05167463A - Receiver - Google Patents

Abstract

PURPOSE:To realize the receiver of automatic frequency control (AFC) with high reliability in which stable correction data are obtained in the digital mobile communication employing time division multiplex access(TDMA). CONSTITUTION:The receiver consists of a mixer 1, an IF section 2, a demodulation section 3, an equalizer 5 having a function to detect a frequency error, a data buffer 6, an arithmetic operation section 7 having a function sending data with an external trigger and an integration function, a reference frequency generating section 8 and a local frequency generating section 9. The receiver has an effect of preventing a frequency shift during the reception or transmission and of suppressing large fluctuation due to integral processing of the arithmetic operation section 7 for correction information obtained from data including an error caused by accident.

Description

Detailed Description of the Invention

[0001]

The present invention relates to automatic frequency control (hereinafter referred to as A
The present invention relates to a receiver having an FC function, particularly Time Division Multiple Access (hereinafter T).
The present invention relates to a receiver used for digital mobile communication using a function called "DMA".

[0002]

2. Description of the Related Art In recent years, communication technology has made great progress in both wired and wireless communication, and in particular, wireless communication has become possible to communicate with any region on the earth including the use of satellites. Along with this progress, there are various types of communication usage, and in the field of wireless communication, application to mobile communication such as car phones, pagers, and mobile phones is remarkable. In wireless communication, the ratio of interfering signals to desired signals is large compared to wired communication, and there are many obstacles for radio wave transmission such as terrain, buildings, and objects, and the conditions change from time to time. Frequency control is essential in order to reliably capture the In particular, with the spread of usage patterns in recent years,
The number of frequency bands used will also increase, and in the future, along with the development of new frequency bands, effective use of frequency bands will be inevitable by narrowing the existing frequency bands and making multiple uses. As the number of frequency bands used for communication increases in this way, selection of a higher frequency band is an essential condition for establishing communication on the receiving side. Especially in mobile communication, the condition of space, which is a medium, constantly changes during communication including obstacles such as terrain and buildings. Therefore, it is important to have an AFC function to reliably and stably capture a necessary frequency. ..

Conventionally, a receiver having an AFC function, for example, as shown in FIG. 2, has a reference frequency generator 27 for generating a reference frequency signal and a local frequency generator for generating a local frequency with reference to an output signal of the reference frequency generator 27. The frequency generator 28, the mixer 21 that mixes the received wave input from the input terminal 29 and the output signal from the local frequency generator 28 and outputs an intermediate frequency signal (IF signal), and the output signal of the mixer 21 An intermediate frequency amplification unit (hereinafter referred to as an IF unit) 22 that amplifies and limits a band, and a demodulation unit 23 that demodulates an output signal of the IF unit 22 and outputs the demodulated signal from an output end 30.
And a frequency error detector 24 that detects a frequency error with a part of the output of the demodulator 23 as an input and controls the reference frequency generator 27 based on the detected error data.

The frequency error detector 24 compares an integrator 25 for integrating the output signal of the demodulator 23 with the output signal of the integrator 25 and the reference frequency signal output from the reference frequency generator 27. The phase detector (PD) 26 detects the phase difference and sends it to the reference frequency generator 27.

In the receiver having such a configuration, the frequency is automatically adjusted as follows. That is, the received wave input from the input terminal 29 is supplied to the reference frequency generator 27.
Frequency generator 28 obtained based on the output of
Is mixed in the mixer 21 with the output signal of and input to the IF unit 22. The mixed wave is amplified by the IF unit 22, band-limited, and then input to the demodulation unit 23 and demodulated. The signal demodulated by the demodulator 23 is output from the output terminal 30 and also input to the frequency error detector 24.

The output signal of the demodulator 23 is integrated by the integrator 25 inside the frequency error detector 24, and the integrated signal and the reference frequency output from the reference frequency generator 27 are compared and detected by the phase detector 26. The comparison result is output to the reference frequency generation unit 27 as frequency error data. The reference frequency corrected by this error data is supplied to the local frequency generator 28.

[0007]

In the case of the receiver using the AFC function, the frequency error is detected by extracting the carrier frequency and comparing the phases. Therefore, it is not effective for, for example, a digitally modulated received wave.
Therefore, a carrier extraction method such as Costas method or inverse modulation method is generally used as a method for carrier extraction, which enables the use of a receiver using the AFC function.

By the way, in the digital communication system, frequency phase synchronization is required between the transmitting side and the receiving side. However, in digital communication using the TDMA method, reception is performed in bursts. When the burst time is short, high-speed frequency pull-in characteristics are required to establish synchronization, and improvement in stable synchronization establishment technology has been required.

Therefore, in the above-mentioned receiver, the frequency error data is successively given to the reference frequency generator 27 for establishing the synchronization. However, if the frequency of the reference frequency generator 27 is corrected during reception or transmission, there is a problem that the frequency shifts during reception or transmission. In digital mobile communication using TDMA, the error rate may temporarily and rapidly deteriorate. For this reason, in the conventional method that corrects all the received data, even if the error rate happens to be deteriorated, it is corrected based on it, and the correction is quite different from the original frequency deviation. There was a problem that it took a lot of time.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly reliable receiver capable of measuring frequency correction timing and obtaining stable correction data. ..

[0011]

A receiver according to the present invention comprises:
A reference frequency generator that outputs a reference frequency signal, a local frequency generator that generates a local frequency signal with reference to the output signal of the reference frequency generator, a received signal and a local frequency signal output from the local frequency generator. A mixer for mixing the frequencies of the above to output an intermediate frequency signal, an intermediate frequency amplifier for amplifying the intermediate frequency signal output from the mixer, and an output signal of the intermediate frequency amplifier for the output signal of the reference frequency generator. And a frequency error that detects an error between the output signal of the demodulation unit and a reference frequency and supplies the error signal to the reference frequency generation unit at the timing when no reception or transmission is performed. And a detector.

Specifically, the frequency error detector has means for sampling the signal output from the demodulator in synchronization with the output signal of the reference frequency generator to equalize distortion in the propagation path. An equalizer, a data buffer that stores the output signal of the equalizer, and an arithmetic unit that integrates the data stored in the data buffer and outputs correction data at a timing when transmission or reception is not performed To be done.

Further, the means for equalizing the distortion of the propagation path in the equalizer detects the phase difference between the symbols separated by at least one or more and detects the difference from the ideal phase difference known in advance. It is characterized by that.

With such a configuration, in the receiver of the present invention, the equalizer of the frequency error detector detects the frequency shift, and the data buffer adjusts the timing of the correction data to be given to the calculator. This correction data is integrated by the calculation unit. And from this calculation unit,
The frequency correction data is supplied to the reference frequency generation unit at the timing when neither reception nor transmission is performed. Therefore, the frequency does not shift during reception or transmission, and there are many errors in certain data, and even if a frequency shift is detected based on this, a large fluctuation can be suppressed by the integration processing of the correction data in the arithmetic unit.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a circuit configuration of a receiver according to an embodiment of the present invention.

The receiver according to the present embodiment includes a reference frequency generator 8 for generating a reference frequency signal, a local frequency generator 9 for generating a local frequency with reference to the output signal of the reference frequency generator 8, and an input terminal. Mixer 1 that mixes the received frequency input from 10 and the local frequency output from local frequency generator 9 to generate an intermediate frequency (IF frequency), and I output from this mixer 1.
An intermediate frequency amplification unit (hereinafter referred to as an IF unit) 2 that amplifies the F frequency and limits the band, and an output signal of the IF unit 2 is demodulated in synchronization with an output signal of the reference frequency generation unit 8 and output from an output end 14. And a frequency error detection unit 4 that detects an error between the output signal of the demodulation unit 3 and the reference frequency and outputs the error signal to the reference frequency generation unit 8 at a timing when reception or transmission is not performed. It consists of and.

The frequency error detector 4 samples the demodulated signal output from the demodulator 3 in synchronization with the output signal of the reference frequency generator 8 and equalizes the distortion in the propagation path. And a data buffer 6 for accumulating the output signal of the equalizer 5 under the control of a control signal (data transmission trigger) 10, and a control signal (external output trigger) 11 for integrating the data accumulated in the data buffer 6. The calculation unit 7 outputs the result to the reference frequency generation unit 8 under the control of 1.

Next, the operation of the receiver of this embodiment will be described.

When the channel designation data 12 is input, the local frequency generator 8 outputs the local frequency corresponding to the designated channel to the mixer 1 with the output of the reference frequency generator 8 as a reference. The mixer 1 mixes the local frequency and the received signal input from the input end 13 and outputs an IF signal to the IF unit 2. In the IF section 2, this I
The F signal is amplified, band-limited, and output to the demodulation unit 3.
The demodulation unit 3 performs, for example, quadrature demodulation using the output signal of the reference frequency generation unit 8 and outputs an in-phase signal (I signal) and an anti-phase signal (Q signal). These signals are output from the output terminal 14 and are also supplied to the frequency error detector 4.

In the frequency error detector 4, the signal from the demodulator 3 is first input to the equalizer 5. The equalizer 5 samples the output signal of the demodulator 3 in synchronism with the signal from the reference frequency generator 8 and detects the phase difference of at least one symbol away from the output signal, and an ideal signal known in advance The difference Δφ [rad] with the phase difference is calculated. Here, when the symbol interval is Δt [sec], the frequency difference Δf at this time is Δf.
Is the following equation.

[0022]

[Formula 1] Δf = Δφ / 2πΔt [Hz]

The equalizer 5 outputs this frequency difference as an error signal and supplies it to the data buffer 6. The data buffer 6 outputs data to the arithmetic unit 7 by the data transmission trigger 10 at the timing when the arithmetic unit 7 completes the arithmetic operation. The calculation unit 7 integrates and stores the input data, and outputs the correction data to the reference frequency generation unit 8 at the timing when the external output trigger 11 does not transmit or receive.
The reference frequency generator 8 changes the output frequency based on this correction data.

As described above, in the receiver according to the present embodiment, the equalizer 5 detects the frequency shift, and the data buffer 6
Adjusts the timing of the correction data to be given to the calculation unit 7, integrates and accumulates the correction data in the calculation unit 7, and adds the frequency correction data to the reference frequency generation unit 8 at the timing when no reception or transmission is performed. There is. Therefore, the frequency does not shift during reception or transmission of data, and it happens that there are many errors in certain data, and even if a frequency shift is detected based on this, the calculation unit 7 integrates to cause a larger fluctuation. Can be suppressed.

[0025]

As described above, according to the receiver of the first to third aspects, the reference frequency generating section for outputting the reference frequency signal, and the local frequency signal with the output signal of the reference frequency generating section as the reference. A local frequency generating section for generating, a mixer for mixing the frequencies of the received signal and the local frequency signal output from the local frequency generating section to output an intermediate frequency signal, and amplifying the intermediate frequency signal output by this mixer. An intermediate frequency amplifier, a demodulator for demodulating the output signal of the intermediate frequency amplifier in synchronization with the output signal of the reference frequency generator, and an error between the output signal of the demodulator and the reference frequency is detected. Since the frequency error detection section that outputs the error signal to the reference frequency generation section at the timing when the error signal is not received or transmitted is provided, Or frequency during transmission there is an effect that there is no shifting.

Further, according to the receivers of claims 2 and 3, there is an effect that a large amount of data happens to be erroneous, and even if a frequency shift is detected based on this, a large fluctuation can be suppressed by integration. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a conventional receiver.

[Explanation of symbols]

 1 mixer 2 intermediate frequency amplification unit (IF unit) 3 demodulation unit 4 frequency error detection unit 5 equalizer 6 data buffer 7 arithmetic unit 8 reference frequency generation unit 9 local frequency generation unit

Claims (3)

[Claims] 1. A reference frequency generating section for outputting a reference frequency signal, a local frequency generating section for generating a local frequency signal based on the output signal of the reference frequency generating section, a received signal and output from the local frequency generating section. A mixer for mixing the frequencies of the local frequency signals to output an intermediate frequency signal, an intermediate frequency amplifier for amplifying the intermediate frequency signal output from the mixer, and an output signal of the intermediate frequency amplifier for the reference frequency A demodulator that demodulates in synchronization with the output signal of the generator and an error between the output signal of this demodulator and the reference frequency is detected,
A receiver comprising: a frequency error detector that supplies the error signal to the reference frequency generator at a timing when the error signal is not received or transmitted. 2. An equalizer having means for equalizing distortion in a propagation path by the frequency error detecting section sampling the signal output from the demodulating section in synchronization with the output signal of the reference frequency generating section. And a data buffer for accumulating the output signal of the equalizer, and an arithmetic unit for integrating the data accumulated in the data buffer and outputting correction data at a timing when transmission or reception is not performed. The receiver according to claim 1, wherein: 3. A means for equalizing the distortion of a propagation path in the equalizer detects a phase difference between symbols that are at least one or more apart and outputs a difference from an ideal phase difference known in advance. The receiver according to claim 2, wherein: