JPH098697A - Spread spectrum communication equipment - Google Patents

Abstract

PURPOSE: To provide the spread spectrum communication equipment which excludes the malfunction due to reception of undesired signal. CONSTITUTION: A correlation detection part 102 which detects correlations between a reception signal and a local spreading code and a reception discrimination part 103 are provided, and this part 103 is provided with a window generation part 202 which periodically generates a time window, a signal detection part 201 which detects the correlation output existing in the window period, and a discrimination part 203 which discriminates the presence of the reception signal at the time of detecting this correlation output a prescribed number of or more times. When an undesired signal is received, the presence of the reception signal is not discriminated because the correlation output is not periodical, this preventing the malfunction of a code synchronizing part 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device in a spread spectrum communication system.

[0002]

2. Description of the Related Art A transmission signal in a spread spectrum communication system is a baseband information signal spread over a wide frequency band by a spreading code such as a pseudo random code. At the time of demodulation, this spread spectrum signal is despread with the same code as the above spread code to obtain a baseband information signal. At this time, if the code synchronization is not established, the information is not demodulated correctly.

As shown in FIG. 3, a conventional basic spread spectrum communication device has a high frequency section 301 and a correlation detecting section 3.
02, a code synchronization unit 303, and an information demodulation unit 304.

The operation of the receiving section of the conventional spread spectrum communication apparatus will be described below with reference to FIG.

The received signal S301 which has been subjected to filtering and other processing by the high frequency section 301 is a correlation detection section 30.
2 and the information demodulation unit 304. Then, correlation detection section 302 detects the correlation between received signal S301 and the local spreading code used for despreading it. Next, the code synchronization unit 303 adjusts the frequency and phase of the code generation clock S304 so that the correlation output S302 obtained as a result and the local reference code timing signal S303 are synchronized. Further, the information demodulation unit 304 despreads the spread spectrum received signal with the local spread code generated from the code generation clock to obtain a baseband information signal.

[0006]

However, in the above-described conventional spread spectrum communication device, the code synchronization unit and the information demodulation unit start operating when the correlation detection unit detects a correlation above a certain threshold level. , Even if the received signal is not desired, if the correlation output is above a certain level,
There is a problem in that a malfunction such as starting synchronization pull-in occurs.

An object of the present invention is to provide a spread spectrum communication device capable of eliminating malfunction due to unwanted signal reception.

[0008]

A spread spectrum communication apparatus according to the present invention has a correlation detecting means for detecting a correlation between a received signal and a local spread code, and window generating means for periodically generating a time window, It is characterized in that it has a reception determination section provided with a signal detection means for detecting a correlation output existing in the window period and a determination means for determining that a reception signal is present when the correlation output is detected a predetermined number of times.

[0009]

With the above construction, even if an undesired signal is received, the correlation output thereof is not periodic, so that the judgment of the presence of the received signal is not outputted, and the malfunction of the code synchronizing section can be prevented.

[0010]

FIG. 1 is a block diagram showing a first embodiment according to the present invention. The receiving unit of the spread spectrum communication apparatus in this embodiment includes a high frequency unit 101 for amplifying and filtering a received signal, a correlation detection unit 102 for detecting a correlation between the received signal and a local spread code, and a received signal for a desired signal. A reception determination unit 103 for determining whether or not the code output unit 104, and a code synchronization unit 104 for synchronizing the correlation output with the local reference code.
And an information demodulation unit 105 that despreads the received signal with a local spreading code.

The operation of the spread spectrum communication apparatus according to this embodiment will be described below with reference to FIG.

The received signal S101 processed by the high frequency section 101 is input to the correlation detecting section 102 and the information demodulating section 105. Further, in the correlation detection unit 102, the received signal S
The correlation between 101 and the local spreading code is detected. Further, the reception determination unit 103 outputs the correlation output S102 obtained as a result.
The presence / absence of a desired received signal is further determined, and the code synchronization unit 10
4 to control the operation.

Further, the code synchronization unit 104 receives the reception determination signal S103 and adjusts the frequency and phase of the code generation clock S105 so as to synchronize the correlation output S102 and the local reference code timing signal S104.

FIG. 2 is a block diagram showing the configuration of the reception determination unit 103.

The reception judging section 103 in this embodiment comprises a signal detecting means 201, a window generating means 202 and a judging means 2.
And 03.

Upon obtaining the correlation output S102, the window generating means 202 periodically generates a window signal from the timing. This cycle is, for example, the cycle of correlation output between the desired received signal and the local spreading code.

The signal detecting means 201 detects the correlation output existing in this window period, and the judging means 203 judges that there is a reception signal when the detection signal S202 is detected a predetermined number of times, and the reception judgment signal S103. Is output.

The predetermined number of times in this case is set to an appropriate value according to the threshold level of correlation output detection, the condition of the communication path, etc., and usually about 3 to 5 times is appropriate.
In addition, the determination method may determine that there is a received signal when there is a continuous correlation output for a predetermined number of times, or when the correlation output appears for a predetermined number of window periods or more among a certain number of set window periods. Alternatively, it may be determined that there is a received signal.

Therefore, even if an undesired signal is received, the correlation output thereof is not periodic, so that the judgment of the presence of the received signal is not output, and the malfunction of the code synchronization unit can be prevented.

FIG. 4 is a block diagram showing the configuration of the second embodiment according to the present invention.

As shown in the figure, this embodiment uses a convolver such as a SAW convolver as the correlation detecting section.

The convolver is an element / circuit for performing a convolution operation of two input signals,
By inputting the time-reversed signal of the desired reception signal as the reference code, correlation with the reception signal can be obtained.

That is, in the second embodiment shown in FIG.
By inputting the local reference code S406 from the information demodulation unit 405 to the convolver 402, the correlation calculation between the received signal S401 and the local reference code S406 is performed.

Regarding other parts, the above first
The description is omitted because it is the same as the embodiment.

[0025]

As described above, according to the present invention, the window generating means for periodically generating the time window, the signal detecting means for detecting the correlation output existing in the window period, and the correlation output for a predetermined number of times are provided. Since the correlation output is not periodic even if an undesired signal is received, the determination of the presence of the received signal is output even if an undesired signal is received. Therefore, there is an effect that a malfunction of the code synchronization unit can be prevented.

As a result, not only erroneous information demodulation can be prevented, but also the problem that the synchronization pull-in time for the next correctly received signal becomes long can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a reception determination unit of the first embodiment.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 101 ... High frequency part, 102 ... Correlation detection part, 103 ... Reception determination part, 104 ... Code synchronization part, 105 ... Information demodulation part.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Akira Torizawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A communication device for use in a spread spectrum communication system, comprising correlation detection means for detecting a correlation between a received signal and a local spread code, and window generation means for periodically generating a time window, and a window. A spread spectrum characterized by having a reception determination section including a signal detection means for detecting a correlation output existing in a period and a determination means for determining a reception signal when the correlation output is detected a predetermined number of times. Communication device. 2. The spread spectrum communication device according to claim 1, wherein a SAW convolver is used as the correlation detecting means.