JP2792292B2 - Receiving machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an automatic frequency control (hereinafter referred to as A
The present invention relates to a receiver having a function called “FC”, and particularly to a Time Division Multiple Access (hereinafter, referred to as “T”).
The present invention relates to a receiver for use in digital mobile communication using a function (hereinafter referred to as DMA).

[0002]

2. Description of the Related Art In recent years, communication technology has made remarkable progress in both wired and wireless communication. In particular, wireless communication has become possible to communicate with any region on the earth including the use of satellites. With this progress, the use form of communication is also diverse, and in the field of wireless communication, applications to mobile communication such as car phones, pagers, and mobile phones are remarkable. In wireless communication, the ratio of interfering signals to desired signals is higher than in wired communication, and there are many obstacles to radio transmission, such as terrain, buildings, and objects, and the conditions change from time to time. It is essential to control the frequency in order to reliably capture the time. In particular, with the spread of usage patterns in recent years,
The frequency bands to be used are also increasing, and in the future, with the development of new frequency bands, effective use of frequency bands by narrowing and multiplexing of existing frequency bands is inevitable. As the frequency bands used for communication increase in this way, the selection of a higher frequency band on the receiving side is an essential condition for establishing communication. In particular, in mobile communication, since the conditions of the space, which is a medium during communication, constantly change, including obstacles such as terrain and buildings, the AFC function to reliably and stably capture the required frequency is important. .

Conventionally, a receiver having an AFC function includes, for example, a reference frequency generator 27 for generating a reference frequency signal and a local frequency generator for generating a local frequency based on an output signal of the reference frequency generator 27 as shown in FIG. A frequency generator 28, a mixer 21 for mixing a received wave input from an input terminal 29 and an output signal from a local frequency generator 28 to output an intermediate frequency signal (IF signal), and an output signal of the mixer 21 An intermediate frequency amplifying unit (hereinafter, referred to as an IF unit) 22 for amplifying and band-limiting the signal;
And a frequency error detection unit 24 that detects a frequency error by using a part of the output of the demodulation unit 23 as an input, and controls the reference frequency generation unit 27 based on the detected error data.

A frequency error detector 24 compares an output signal of the integrator 25 with an integrator 25 for integrating an output signal of the demodulator 23 and a reference frequency signal output from a reference frequency generator 27. A phase detector (PD) 26 which detects a phase difference and sends it to a reference frequency generating unit 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
Local frequency generator 28 obtained based on the output of
Are mixed in the mixer 21 and input to the IF unit 22. This mixed wave is amplified by the IF unit 22, band-limited, input to the demodulation unit 23, and demodulated. The signal demodulated by the demodulation unit 23 is output from the output terminal 30 and is also input to the frequency error detector 24.

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

[0007]

In the case of a receiver using the AFC function, detection of a frequency error is performed by extracting a carrier frequency and comparing phases. For this reason, it is not effective, for example, for a digitally modulated reception wave.
Therefore, a carrier extraction method such as the Costas method or the inverse modulation method is generally used as a method for carrier extraction, and this makes it possible to use a receiver using the AFC function.

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 system, reception is performed in bursts. When the burst time is short, high-speed frequency loading characteristics are required to establish synchronization, and there has been a demand for an improved technique for establishing stable synchronization.

Therefore, in the above-mentioned receiver, frequency error data is sequentially given to the reference frequency generator 27 for establishing synchronization. However, if the frequency correction of the reference frequency generation unit 27 is performed during reception or transmission, there has been a problem that the frequency is shifted during reception or transmission. Also, in digital mobile communication using TDMA, the error rate may temporarily and suddenly deteriorate. For this reason, in the conventional method of correcting all received data, even when data with an error rate that happens to be degraded is received, the correction is performed based on that data, and the correction is considerably different from the original frequency deviation. Problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide a highly reliable receiver capable of measuring frequency correction timing and obtaining stable correction data. .

[0011]

SUMMARY OF THE INVENTION A receiver according to the present invention comprises:
A reference frequency generator for outputting a reference frequency signal, a local frequency generator for generating a local frequency signal based on an output signal of the reference frequency generator, a received signal and a local frequency signal output from the local frequency generator And an intermediate frequency amplifier that amplifies the intermediate frequency signal output from the mixer, and outputs the output signal of the intermediate frequency amplifier to the output signal of the reference frequency generator. A demodulator that demodulates in synchronization with a frequency error detected between an output signal of the demodulator and a reference frequency, and a frequency error supplied to the reference frequency generator at a timing when the error signal is not received or transmitted. A detection unit.

Specifically, the frequency error detection section has means for sampling a signal output from the demodulation section in synchronization with an output signal of the reference frequency generation section and equalizing distortion in a propagation path. An equalizer, a data buffer that accumulates an output signal of the equalizer, and an arithmetic unit that integrates the data accumulated in the data buffer and outputs correction data at a timing at which transmission or reception is not performed Is done.

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

With such a configuration, in the receiver of the present invention, the frequency shift is detected by the equalizer of the frequency error detection unit, and the timing of the correction data to be given to the calculation unit is adjusted by the data buffer. This correction data is integrated by the calculation unit. Then, from this arithmetic unit,
The frequency correction data is supplied to the reference frequency generation unit at a timing when reception or transmission is not performed. Therefore, the frequency does not shift during reception or transmission, and there is a large amount of error in some data, and even if a frequency shift is detected based on this, a large variation can be suppressed by the integration processing of the correction data in the calculation unit.

[0015]

Embodiments of the present invention will be described below 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 based on an output signal of the reference frequency generator 8, and an input terminal. Mixer 1 that mixes the reception frequency input from 10 with the local frequency output from local frequency generation unit 9 to generate an intermediate frequency (IF frequency), and I that is output from mixer 1
An intermediate frequency amplifying unit (hereinafter, referred to as an IF unit) 2 for amplifying the F frequency and limiting the band; an output signal of the IF unit 2 is demodulated in synchronization with an output signal of the reference frequency generating unit 8 and output from an output terminal 14 A frequency error detector 4 that detects an error between the output signal of the demodulator 3 and the reference frequency and outputs the error signal to the reference frequency generator 8 at a timing when no reception or transmission is performed. It is composed of

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

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 a local frequency corresponding to the designated channel to the mixer 1 with reference to the output of the reference frequency generator 8. The mixer 1 mixes the local frequency with the received signal input from the input terminal 13 and outputs an IF signal to the IF unit 2. In the IF unit 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 in-phase signal (Q signal). These signals are output from the output terminal 14 and supplied to the frequency error detection unit 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 demodulation unit 3 in synchronization with the signal from the reference frequency generation unit 8, detects a phase difference between symbols separated by at least one or more, and detects an ideal difference known in advance. The difference Δφ [rad] from the phase difference is determined. Here, assuming that the symbol interval is Δt [sec], the frequency difference Δf at this time is
Is the following equation.

[0022]

## EQU1 ## 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 operation unit 7 by the data transmission trigger 10 at the timing when the operation of the operation unit 7 ends. 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 transmission or reception is not performed by the external output trigger 11.
The reference frequency generator 8 changes the output frequency based on the correction data.

As described above, in the receiver according to the present embodiment, the frequency shift is detected by the equalizer 5 and the data buffer 6 is detected.
The timing of the correction data to be given to the calculation unit 7 is adjusted by the above, the correction data is integrated by the calculation unit 7 and accumulated, and the frequency correction data is added to the reference frequency generation unit 8 at the timing of not performing reception or transmission. I have. Therefore, the frequency does not shift during data reception or transmission, and there is a lot of errors in the data that happens to occur. Even if a frequency shift is detected based on this, a larger variation occurs due to integration in the arithmetic unit 7. Is suppressed.

[0025]

As described above, according to the receivers of the first to third aspects, a reference frequency generator for outputting a reference frequency signal and a local frequency signal based on the output signal of the reference frequency generator are used as a reference. A local frequency generator for generating, a mixer for mixing the frequency of the received signal and the frequency of the local frequency signal output from the local frequency generator and outputting an intermediate frequency signal, and amplifying the intermediate frequency signal output by the mixer An intermediate frequency amplifier, a demodulator that demodulates the output signal of the intermediate frequency amplifier in synchronization with the output signal of the reference frequency generator, and detects an error between the output signal of the demodulator and the reference frequency. A frequency error detection unit that outputs the error signal to the reference frequency generation unit at a timing when reception or transmission is not performed. Or frequency during transmission there is an effect that there is no shifting.

Further, according to the receiver of the second and third aspects, there is an effect that a large amount of error is occasionally generated in the data, and even if a frequency shift is detected based on the error, a large variation can be suppressed by integration. is there.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mixer 2 Intermediate frequency amplification part (IF part) 3 Demodulation part 4 Frequency error detection part 5 Equalizer 6 Data buffer 7 Operation part 8 Reference frequency generation part 9 Local frequency generation part

Claims (3)

(57) [Claims] A reference frequency generator for outputting a reference frequency signal; a local frequency generator for generating a local frequency signal based on an output signal of the reference frequency generator; a received signal and an output from the local frequency generator A mixer that mixes the frequencies of the local frequency signals to be output and outputs an intermediate frequency signal; an intermediate frequency amplifying unit that amplifies the intermediate frequency signal output from the mixer; A demodulator that demodulates in synchronization with an output signal of the generator, and detects an error between the output signal of the demodulator and a reference frequency,
A receiver for supplying a frequency error detector to the reference frequency generator at a timing when the error signal is not received or transmitted. 2. An equalizer comprising: means for sampling the signal output from the demodulation section in synchronization with an output signal of the reference frequency generation section, and equalizing distortion in a propagation path. 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 distortion of a propagation path in the equalizer detects a phase difference between symbols separated by at least one or more and outputs a difference from a previously known ideal phase difference. 3. The receiver according to claim 2, wherein: