JPH07105745B2 - Spread spectrum receiver - Google Patents

Description

The present invention relates to a receiver used in spread spectrum communication (hereinafter abbreviated as SSC in the present specification).

[Summary of the Invention] A received signal composed of an SSC signal and an interfering wave in the SCC signal band is separated into an upper band and a lower band, and by comparing the powers of the upper band and the lower band signals, the above interfering wave does not exist An SSC receiver that uses the SSC signal in the upper band or the lower band as the output signal.

[Prior Art] Generally, when a strong other signal (interfering wave) is mixed in a frequency band (desired wave) used for transmission and reception in wireless communication, waveform distortion occurs in a receiver due to saturation of an amplifier or the like. The same can be said for AGC (Automatic Gain Control) amplifiers as long as the input level exceeds the dynamic range.

As a result, in analog communication, for example, sound quality deteriorates, and in digital communication, for example, data bit errors increase.

Therefore, it is necessary to remove the interfering wave, and FIG. 3 shows an example of the conventional method. In the figure, 9 is a received signal, 10 is an output signal, 11 is a variable notch filter, and 12 is an interference wave detection circuit.

The interfering wave (its frequency) in the received signal 9 (desired wave frequency band) is detected by the interfering wave detection circuit 12, and the notch frequency of the variable notch filter 11 is adjusted to the interfering wave frequency based on the detected signal to obtain the received signal. The interfering wave in 9 is removed and only the desired wave is used as the output signal 10.

The SSC method is a communication method in which the spectrum of the information signal is spread and transmitted over a wide frequency band, and the receiving side despreads the spread spectrum to restore the information signal (direct spreading method: SS -See DS Fig. 4)
And the interfering wave 14 in the spread signal 13 as shown in FIG.
It is known that even if the interference occurs, the de-spreading can eliminate the interference with the processing gain as shown in FIG. 4 (b). In FIG. 4 (b), 15 indicates a desired wave (information signal) and 16 indicates an interference wave (interfering wave).

A correlator is used for despreading, and for example, a sliding correlator, a matched filter, a convolver, or the like is used.

However, if it is a strong interfering wave that exceeds the processing gain, it will affect the data demodulation as in a general wireless communication system. Therefore, it is necessary to remove the interfering wave, and there are conventional methods similar to those shown in FIG.

[Problem to be Solved by the Invention] In this case, it is not easy for the interference wave detection circuit to detect only the interference wave from the spectrum signal spread over a wide frequency band.

As one method, in the case of a circuit that searches for an interference wave using a frequency sweeper, it is necessary to search a wide frequency range, and the real-time property is lacking. Furthermore, the frequency sweeper and its peripheral circuits are large in scale and complicated in structure,
There are drawbacks such as downsizing and cost reduction.

In addition, the variable notch filter is similar to the interfering wave detection circuit,
The notch must be able to be changed over a wide frequency band, which is not easy in terms of circuit configuration. Therefore, there is a problem that the circuit scale becomes complicated, and the size and cost cannot be reduced.

[Object of the Invention] An object of the present invention is to provide a simple SSC receiver capable of obtaining a good reception signal even at the time of interference of interference waves.

[Means for Solving the Problems] In order to achieve the above object, an SSC receiver according to the present invention includes a band separation means for separating a spread spectrum received signal into a signal component of a lower band and an upper band, and the lower band. Comparing means for comparing the power of the signal components of the upper band, and switching means for extracting and outputting the signal component of the lower band or the upper band of the smaller power from the output of the band separating means according to the output of the comparing means. The main point is to include.

[Operation] The power spectrum of the SSC signal has a symmetrical relationship (upper band and lower band) about the carrier frequency (f ₀ ), and the baseband information spread by the pseudo noise code is also upper band and lower band. Exists in each of. Therefore, each bandpass filter (hereinafter, abbreviated as BPF in this specification).
In the comparison of energy passed through, for SSC signal,
Since the upper band and the lower band have the same energy, the detection of the interfering wave can be easily understood by using the method of comparing the respective energies, and according to the present invention, only the one which is not disturbed by the upper band and the lower band is taken. However, there is no missing baseband information.

Also, the SSC signal that passes only the upper band or the lower band has half the energy (3 dB down) of the original SSC signal, but since the phase in the SSC signal is retained, there is no problem in data demodulation. Absent.

[Examples] Hereinafter, the present invention will be described in more detail using examples with reference to the drawings. However, these are merely examples, and various modifications and improvements can be made without departing from the scope of the present invention. Of course it is possible.

FIG. 1 is a block diagram showing the configuration of an SSC receiver according to the present invention. In the figure, 1 and 2 are BPFs, 3 and 4 are detection circuits, 5 and 6 are integration circuits, 7 is a comparator, and 8 is a switch circuit. , 9 is the received signal, 10
Is the output signal.

The operation of the above embodiment will be described below (see FIG. 2 (a)).

The reception signal 9 in which the interfering wave 14 is mixed with the SSC signal 13 is input to BPF1 and BPF2.

The passbands of BPF1 and BPF2 have the characteristics shown in FIG. 2 (b).

Each filter output of BPF1 and BPF2 is detected by each detection circuit 3 and 4, and each detection output is integrated circuit 5
And 6 are integrated and input to the comparator 7.

If there is an interfering wave, for example, the integrated voltage value of the output of the integrating circuit 6 that has passed through BPF2 is larger than the output of the integrating circuit 5.
This is because the energy of the interfering wave is added.

As a result, in the comparator 7, the integrating circuits 5 and 6
The outputs of are compared and a signal is output.

The output of the comparator 7 is used as a control signal to control the switch circuit 8.

Now, the output of the integrating circuit 5 <the output of the integrating circuit 6, and the output of the comparator 7 outputs a negative voltage signal.

As a result, the switch circuit 8 is turned on (connected) to the side a and outputs the SSC signal that passes through the BPF1 in which no interference wave exists (see FIG. 2 (c)).

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a good reception signal even at the time of interference with a simple SSC.
You can get a receiver.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an SSC receiver according to the present invention, FIG. 2 is a frequency distribution diagram for explaining the operation of the apparatus shown in FIG. 1, and FIG. 3 is a conventional interference wave canceling circuit block. FIG. 4 and FIG. 4 are frequency distribution diagrams in the data demodulation process of SSC. 1,2 …… BPF, 3,4 …… Detection circuit, 5,6 …… Integration circuit, 7 ...
... comparator, 8 ... switch circuit, 9 ... received signal, 10 ...
… Output signal.

Claims (1)

[Claims] 1. A band separation means for separating a spread spectrum received signal into signal components of a lower side band and an upper side band, a comparison means for comparing electric powers of signal components of the lower side band and an upper side band, and an output of the comparison means. Accordingly, a spread spectrum receiver comprising: switching means for extracting and outputting a lower band or upper band signal component having a smaller power from the output of the band separation means.