JPH0429431A - Spread spectrum synchronizing device - Google Patents

Abstract

PURPOSE:To stably perform spread synchronization even when the input level of a reception signal is high by controlling the gain of a variable gain amplifier which amplifies an intermediate frequency signal band-limitation-filtered at an intermediate frequency filter by a control signal in which a signal integrating the detection output of a detector is amplified. CONSTITUTION:When the input level of the reception signal inputted to an input terminal 1 is high and no synchronism is taken, a high noise level is outputted from the detector 6. However, since an AGC loop is comprised of the route of the variable gain amplifier 10 the detector 6 an integration circuit 11 an AGC amplifier 12, the gain of the variable gain amplifier 10 is controlled so that the noise level of the detection output of the detector 6 can be set less than the threshold level of a synchronism decision apparatus 7 by the control signal from the AGC amplifier 12. Therefore, when no synchronism is taken, noise energy inputted to the detector 6 can be kept constant in spite of the size of the input level of the reception signal, and the noise level outputted from the detector 6 can be set less than the threshold level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spread spectrum synchronization device used in a spread spectrum receiver.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional spread spectrum synchronization device disclosed in, for example, Japanese Unexamined Patent Publication No. 1-220542. In the figure, 1 is an input terminal to which a spread spectrum received signal is input, and 2 is a despread code generator that generates a local reference signal for despread modulation. 3
4 is a correlator that multiplies the local reference signal by the received signal to convert it into an intermediate frequency signal, and 4 is an intermediate frequency filter that limits the band of the intermediate frequency signal output from the correlator 3. .

5 is an intermediate frequency amplifier that amplifies the intermediate frequency signal band-limited by this intermediate frequency filter 4, and 6 is a detector that detects the amplified intermediate frequency signal and converts it into a DC signal. be. 7 is a synchronization determiner that detects coincidence of spreading codes based on the DC signal and determines synchronization; 8 generates a clock pulse whose phase can be shifted and supplies it to the despreading code generator 2; This clock generator stops its clock phase shift in response to the spread code coincidence detection signal output from the synchronization determiner 7.

Next, the operation will be explained. The received signal inputted from the input terminal 1 is a spread spectrum signal, and is multiplied by the local reference signal whose phase is slipping from the despreading code generator 2 and is converted into an intermediate frequency signal by the correlator 3. . If the received signal and the local reference signal are synchronized and their spreading codes match, the intermediate frequency signal converted by the correlator 3 will have a sharp spectrum as shown by symbol a in Figure 3. When asynchronous, the spectrum becomes smooth like the spectrum shown by the symbol in the same figure.

The intermediate frequency signal output from the correlator 3 is filtered by an intermediate frequency filter 4 to limit its band, and is sent to an intermediate frequency amplifier 5. The intermediate frequency signal amplified by the intermediate frequency amplifier 5 is further sent to a detector 6 where it is detected and converted into a DC signal. Therefore, during synchronization, the level of the DC signal of the detector 6 increases compared to when non-synchronization occurs.

As shown in FIG. 5(a), the synchronization determination circuit 7 compares the level of the DC signal from the detector 6 with a predetermined threshold level and determines whether the spreading codes of the received signal and the local reference signal match. It detects that the clock is removed and sends a detection signal to the clock generator 8. The detection signal from the clock generator 8 causes the clock phase shift of the clock pulses being generated to be stopped.

This means that the despreading code generator 2 generates a spreading code synchronized with the received signal.

Here, if the input level of the received signal is large, the energy passing through the intermediate frequency filter 4 will also be large, resulting in a saturation region where the linearity of input and output of the intermediate frequency amplifier 5 and the detector 6 cannot be maintained. Therefore, in such a case, the noise level of the output of the detector 6 for detecting the correlation peak may exceed the threshold level of the synchronization determiner 7, as shown in FIG.

[Problem to be solved by the invention]

Since conventional spread spectrum synchronization devices are configured as described above, synchronization detection is performed based on the presence or absence of an intermediate frequency signal, and therefore, the spreading codes of the received signal and local reference signal do not match. Nevertheless, there is a possibility that the noise level of the output of the detector 6 exceeds the threshold level of the synchronization determiner 7, and in such a case, even an asynchronous state may be mistakenly recognized as synchronized. There was the issue of putting it away.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a spread spectrum synchronization device that can stably detect spread synchronization regardless of the input level of a received signal.

[Means to solve the problem]

The spread spectrum synchronization device according to the present invention uses a variable gain amplifier whose gain can be controlled by a control signal as an intermediate frequency amplifier that amplifies the intermediate frequency signal band-limited by the intermediate frequency filter, and detects an automatic gain control (hereinafter referred to as AGC) amplifier that amplifies the integrated output of the integrating circuit and generates a control signal for controlling the gain of the variable gain amplifier. It was established.

[Effect]

The AGC amplifier in this invention amplifies the integrated output of the integrating circuit that integrates the detected output of the wave detector to generate a control signal for adjusting the gain of the variable gain amplifier, and the variable gain amplifier responds to the control signal. Spread spectrum synchronization allows stable spread synchronization even if the input level of the received signal is high, by amplifying the passed intermediate frequency signal, which limits the band with an intermediate frequency filter, and sending it to the detector. Realize the device.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is an input terminal, 2 is a despreading code generator, and 3 is a despreading code generator.
4 is a correlator, 4 is an intermediate frequency filter, 6 is a detector, 7 is a synchronization determiner, and 8 is a clock generator, which are the same or equivalent parts to those of the conventional ones with the same reference numerals in FIG. Therefore, detailed explanation will be omitted.

Further, 10 is used as an intermediate frequency amplifier that amplifies the intermediate frequency signal band-limited by the intermediate frequency filter 4 and outputs it to the detector 6, and its gain is variable and controllable by a control signal. It is a gain amplifier. 11 is an integrating circuit that integrates the detection output of the detector 6, and 12 is a variable gain amplifier 1 that amplifies the integrated output of this integrating circuit 11.
This is an AGC amplifier that generates a control signal for zero gain control.

Next, the operation will be explained. The received signal inputted from the input terminal 1 is a spread spectrum signal, and as in the conventional case, it is multiplied by the local reference signal whose phase is slipping from the despreading code generator 2 and the correlator 3. . The intermediate frequency signal output from the correlator 3 is input to an intermediate frequency filter 4, subjected to a band-limiting wave, and sent to a variable gain amplifier 10.

This variable gain amplifier 10 has a gain equal to that of the AGC amplifier 1.
2, intermediate frequency filter 4
to a predetermined level. The output of the variable gain amplifier 10 is subjected to envelope detection by a wave detector 6, and the detected output is input to an integrating circuit 11 and integrated. The integrated output of the integrating circuit 11 is amplified to an appropriate level by the AGC amplifier 12 and then sent to the variable gain amplifier 10 as a control signal for controlling the gain of the variable gain amplifier 10.

Here, when the input level of the received signal input to the input terminal 1 is high and synchronization is not achieved, the detector 6 outputs a high noise level.

However, since the AGC loop is configured by the variable gain amplifier 1o → the detector 6 → the integrating circuit 11 → the AGC amplifier 12, the gain of the variable gain amplifier 10 is determined by the control signal from the AGC amplifier 12, and the detected output of the detector 6 is The noise level of the synchronization determiner 7 is controlled to be below the threshold level. Therefore, when synchronization is not achieved, the noise energy input to the detector 6 is constant regardless of the input level of the received signal, and the noise level output from the detector 6 is below the threshold. .

Furthermore, when synchronization is achieved, a sharp spectrum as shown by symbol a in FIG. 3 is output from the correlator 3. At this time, the waveform output from the wave detector 6 is a peak waveform with a high level as shown in FIG. Therefore, the gain of the variable gain amplifier 10 is suppressed, and the same energy is input to the detector 6 as in the previous non-synchronization. In this case, as shown in FIG. 3, the output signal vector from the correlator 3 is output from the detector 6 because the spectral density during synchronization, indicated by symbol a, is greater than that during non-synchronization, indicated by symbol a. The level of the output DC signal is higher than the noise level or threshold level, and synchronous detection becomes possible.

〔Effect of the invention〕

As described above, according to the present invention, the variable gain amplifier amplifies the intermediate frequency signal band-limited by the intermediate frequency filter using the control signal obtained by amplifying the signal obtained by integrating the detection output of the detector. Since the gain is controlled, it is possible to obtain a spread spectrum synchronization device that can stably perform spread synchronization even if the input level of the received signal is high.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a spread spectrum synchronization device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the operation of its synchronization determiner, and FIG. 3 is a block diagram showing a spread spectrum synchronization device according to an embodiment of the present invention. FIG. 4 is a block diagram showing a conventional spread spectrum synchronization device, and FIG. 5 is an explanatory diagram showing the operation of the synchronization determiner. 2 is a despreading code generator, 3 is a correlator, 4 is an intermediate frequency filter, 5 is an intermediate frequency amplifier, 6 is a detector, 7 is a synchronization determiner, 8
1 is a clock generator, 10 is a variable gain amplifier, 11 is an integration circuit, and 12 is an AGC amplifier. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent applicant Mitsubishi Electric Co., Ltd. agent Patent attorney 1) Hiroshi Sawa (2 others)

Claims (1)

[Claims] A despreading code generator that generates a local reference signal for despreading modulation, and a correlation that multiplies the spread spectrum received signal by the local reference signal generated by the despreading code generator and converts it into an intermediate frequency signal. an intermediate frequency filter that performs band limiting filtering of the intermediate frequency signal converted by the correlator, and an intermediate frequency filter that amplifies the intermediate frequency signal band limited filtered by the intermediate frequency filter. an amplifier; a detector that detects the intermediate frequency signal amplified by the intermediate frequency amplifier;
a synchronization determiner that detects coincidence of spreading codes based on the detection output of the detector and determines synchronization; A spread spectrum synchronization device comprising a clock generator that stops its clock phase shift in response to a coincidence detection signal of the spread code from a determiner,
As the intermediate frequency amplifier, a variable gain amplifier whose gain can be controlled by a control signal is used. 1. A spread spectrum synchronization device comprising: an automatic gain control amplifier that generates a control signal for controlling gain.