JPH02174327A - Spread spectrum communication equipment - Google Patents

Abstract

PURPOSE:To effectively utilize a frequency band by providing a means obtaining a correlation to a prescribed PN code among plural kinds of PN codes as to the output signal of a reception means. CONSTITUTION:Selection means 11, 13 at the transmitter side Tx select and output a PN code with less inter-code interference corresponding to each state of an input data. Then the transmission signal generated based on the output of the selection means 11, 13 is outputted from a transmission means having a device such as a transmission amplifier 17. The receiver side Rx receives the transmission signal sent in such a manner and uses a correlation device 31 such as a convolver using a surface acoustic wave(SAW) to apply inverse spread spectrum processing to the frequency band of the received signal, thereby demodulating the data. In this case, an image PN code to any of plural kinds of PN codes as the inverse spread spectrum processing PN code inputted to the correlation device 31 is used. Thus, the frequency band is utilized effectively.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a spread spectrum communication device, and particularly to a communication device that performs modulation by switching a plurality of PN (pseudo-noise) codes according to the state value of a transmitted signal. Regarding.

[Prior Art] Conventionally, as a spread spectrum communication system, for example, DS-FSK (Direct 5equen
ce-Frequency 5hlf't Keyln
g) method is known (see Institute of Electronics, Information and Communication Engineers, Spread Spectrum Communication Study Group Materials, April 1-20, 1988, "Asynchronous SSC Transceiver Using rSAW Convolver by Tsubouchi et al."). In such communication systems, input data is transmitted to a voltage controlled oscillator (VCO).
A transmission signal is obtained by manually performing so-called FSK modulation in which the frequency is changed according to the state value of the input data, and then spread-modulating the FSX-modulated signal using a single PN code. Such a system has the advantage of being able to communicate over relatively long distances even using weak radio waves with extremely low field strength.

[Problem to be solved by the invention] However, in the conventional communication system described above, F.
Since a VCO or the like is used for SK modulation, there is an inconvenience that the frequency of the transmitted signal is adversely affected by changes in the surrounding environment, noise, etc., and becomes unstable. Also,
Since at least two types of transmission carrier frequencies are required, there is a problem in terms of effective use of the frequency band.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spread spectrum communication device that has excellent transmission frequency stability and can effectively utilize a frequency band, in view of the problems in the conventional communication systems described above.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the spread spectrum communication device according to the present invention includes a PN code generation means for generating a plurality of types of PN codes as a transmitter, and a PN code generating means for generating a plurality of types of PN codes, and a PN code generation means for generating a plurality of types of PN codes, and a PN code generating means for generating a plurality of types of PN codes as a transmitter. A device is used that includes a selection means for selectively outputting one of the plurality of types of PN codes in response to the selection means, and a transmission means for transmitting a transmission signal generated based on the output of the selection means. Further, the receiver includes a receiving means for receiving the transmission signal, and a correlation detecting means for determining the correlation between the output signal of the receiving means and a predetermined PN code among the plurality of types of PN codes. used.

[Operation] In the apparatus having the above-mentioned configuration, the selection means selects a PN code with less mutual code amount interference corresponding to each state value of the input data, for example, data "1° or "0" on the transmitter side. Then, a transmission signal generated based on the output of this selection means is sent out from a transmission means having, for example, a transmission amplifier.On the receiver side, the transmission signal sent out in this way is received, for example, A correlator such as a convolver using surface acoustic waves (SAW) despreads the frequency band of the received signal and demodulates the data.In this case, the despreading P input to the correlator
As the N code, an image PN code corresponding to any one of the plurality of types of PN codes can be used.

[Example code] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 schematically shows a transmitter in a spread spectrum communication device according to an embodiment of the present invention. The transmitter in the same figure is
For example, an oscillator 1 that generates a 250 MHz signal, a balanced modulator 3, a PN code generator 5 that generates a first type of PN code (PNN code), and a second type of PN code (
a PN code generator 7 for generating a PNN code), a data input circuit 9, a changeover switch 11, 13, such as a data selector/multiplexer schematically shown. Low pass filters 15, 19, transmission amplifier 17, and transmission antenna 2
It is equipped with 1. The data input circuit 9 is constituted by, for example, a microprocessor that provides binary digital data. The changeover switches 11.13 are actually constituted by electronic circuits that selectively output either the PNN code or the PNN code according to the state value of the transmission data from the data input circuit 9.

FIG. 2 schematically shows a receiver for use with the transmitter of FIG. The receiver in the figure is, for example, 250 MHz
an oscillator 23 that generates a signal, and a PN code generator 25 that generates a PN code A' that has an image relationship with the PNN code generated from the PN coco generator 5 of FIG.
It has a balanced modulator 27, a low-pass filter 29, and a correlator 31, such as a SAW convolver, to which the output of the low-pass filter 29 is applied to one input. The receiver of FIG. 2 also includes a receiving antenna 33 and a bandpass filter 35.
, a receiving amplifier 37 , a logarithmic amplifier 39 , and a low-pass filter 41 , and the output of the receiving circuit constituted by these is connected to the other input of the correlator 31 . Further, the output of the correlator 31 includes an amplifier 43 for amplifying a signal with a frequency of, for example, 500 MHz, a high-pass filter 45, a detection circuit 47, an amplifier 49, and a comparator for comparing the output of the amplifier 49 with a predetermined signal. 51 and data output circuit 53
are connected.

The operation of the spread spectrum communication device having the above configuration will be explained with reference to FIG. In the transmitter shown in FIG. 1, from the data input circuit 9 to the transmitter shown in FIG.
) is assumed to output the data human input signal. In this data input signal, digital data "1" corresponds to a high level, and data "0°" corresponds to a low level.The changeover switches 11 and 13 are switched according to the data value of such data input signal. It will be done.

When the data input signal is at a high level, that is, data "1", each switch 11 and 13 is connected to the side of the PN code generator 5, and the first type of PNN code is output from the PN code generator 5. and is input to the balanced modulator 3. On the other hand, when the data input signal is at a low level, that is, data "0", each switch 11.13 is set to PN.
A second type of PNN code is connected to the code generator 7 side and inputted to the balanced modulator 3 . Note that it is desirable that the PN code generators 5 and 7 are capable of generating PN codes with little interference in code amount with each other, for example. In this way, one input of the balanced modulator 3 has different types of PNs depending on the state value of the data input as shown in FIG. 3(d).
The code is manually written.

・250 from oscillator 1 to the other manual power of 1 and equilibrium modulator 3
A MHz signal is generated manually, and this signal and the composite PN code output are mixed to generate a transmission signal. This transmission signal passes through a low-pass filter 15, a transmission power amplifier 17, and one low-pass filter at the final stage, where it is amplified and unnecessary band components are removed before being transmitted from the antenna 21.

The transmission radio waves transmitted from the transmitter in this manner are received by the antenna 33 of the receiver shown in FIG. After that, it is applied to one input of the correlator 31. Further, the PN code A', which has an image relationship with the PNN code output from the PN code generator 5 on the transmitter side, is output from the PN code generator 25.
and is applied to one side of the balanced modulator 27. A 250 MHz signal is applied from the oscillator 23 to the other input of the balanced modulator 27, and a PN code whose frequency has been converted to a center frequency of 250 MHz is applied to the other input of the correlator 31 via the low-pass filter 29. be done. Therefore, a signal as shown in FIG. 3(e) is obtained at the output of the correlator 31, for example, a SAW convolver. That is, the correlator 31 outputs a convolution waveform in a portion corresponding to data "1", that is, the PNN code. By detecting such a signal by the detector 47 via the amplifier 43 and the high-pass filter 45, the detected output shown in FIG. 3(f) is obtained. This detected output is compared with a predetermined threshold value in a comparator 51, and further amplified, pulse width expanded, waveform shaped, etc. are performed in a data output circuit 53, thereby obtaining a data output as shown in FIG. 3(g). It will be done.

In the above-mentioned configuration, the transmitter is provided with two PN code generators 5 and 7, and the two PN code generators 5 and 7 are configured to be switched and outputted by switching means 11 and 13 such as a data selector/multiplexer. A Gold code generator can also be used as a means for obtaining different PN codes depending on the state value of the data input.

[Effects of the Invention] As described above, according to the present invention, for example, weak radio A spread spectrum communication device suitable for equipment can be realized.

Furthermore, since the carrier frequency is a single frequency, it is possible to effectively utilize the frequency band.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram schematically showing a transmitter in a spread spectrum communication device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a receiver used in combination with the transmitter shown in FIG. The circuit diagram and FIG. 3 are waveform diagrams for explaining the operation of the apparatus shown in FIGS. 1 and 2. 1; Oscillator; 3; Balanced modulator; 5.7. PN code generator, 9; data input circuit, 11.13. switching circuit, 15
, 19. Low-pass filter, 17; Transmission amplifier, 21; Transmission antenna, 23; Oscillator, 25, PN Coco-generator, 27; Balanced modulator, 29.41; Low-pass filter, 31; Correlator, 33; Reception antenna, 35; bandpass filter, 37 43 49
; Amplifier, 3 logarithmic amplifiers, 45: High-pass filter, 47; Detector, 51; Comparator, 53; Data output circuit. Patent applicant Mitsui Metal Mining Co., Ltd.

Claims (1)

[Claims] PN code generation means for generating a plurality of types of PN codes;
a selection means for selectively outputting one of the codes; a transmission means for transmitting a transmission signal generated based on the output of the selection means; a reception means for receiving the transmission signal; 1. A spread spectrum communication device comprising: correlation detection means for determining correlation with a predetermined PN code among a plurality of types of PN codes.