JPS60257634A - Spread spectrum communication equipment - Google Patents

Abstract

PURPOSE:To improve the S/N by comparing a carrier component of a reception signal and a local oscillation carrier of a voltage controlled oscillator, controlling the voltage controlled oscillator from the result of comparison and multiplying the local oscillation carrier with the reception signal. CONSTITUTION:A carrier extracting circuit 11 at the reception side extracts a carrier component from a reception signal and the carrier component extracted at a phase comparator is compared with the local oscillating carrier from the voltage controlled oscillator, and the voltage controlled oscillator 13 is controlled so as to make the phase identical. A multiplier 10 multiplies the reception signal with the local oscillation carrier from the voltage controlled oscillator 13 so as to attain synchronizing demodulation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a spread spectrum communication device, and particularly to a spread spectrum communication device that has good noise resistance and is capable of speeding up synchronization detection.

[Background of the invention]

In a spread spectrum communication device, the transmitting side spreads the transmission information using a spread spectrum code such as a pseudo-noise code that has a sufficiently wider frequency band, then phase-modulates the carrier wave with that signal, transmits it, and then transmits it on the receiving side. Create a signal synchronized with the same spread spectrum code and ML transmission wave as the side,
It performs synchronous demodulation and spectrum despreading to reproduce transmitted information.

In this type of spread spectrum communication device, if the carrier wave on the spread spectrum code is not synchronized between transmitting and receiving,
Transmitted information cannot be reproduced correctly. This synchronization is the biggest challenge for spread spectrum communication devices.

As one measure for this synchronization, for example, Japanese Patent Laid-Open No. 56-3124
There is Publication No. 6. Another issue with this spread spectrum communication device is the signal-to-noise ratio (S/N) on the receiving side.
There is a problem in Japan, and there is an urgent need to solve this problem.

[Purpose of the invention]

The present invention has been made based on the above-mentioned matters, and an object of the present invention is to provide a spread spectrum communication device that has good noise resistance and is capable of high-speed synchronization.

[Summary of the invention]

In order to achieve the above object, the present invention includes a transmitter that spreads transmitted information using a spreading code having a wide bandwidth, further phase-modulates the transmitted information, and transmits the transmitted information, and a transmitter that despreads transmitted information using the same spreading code as the transmitter. In a spread spectrum communication device, the receiver is provided with a carrier wave extraction circuit that extracts a carrier wave component from a received signal, and the carrier wave extraction circuit receives the carrier wave component from this circuit and local oscillation from a voltage controlled oscillator. A phase comparator that compares the phase with a carrier wave and controls the voltage controlled oscillator so that the phases are the same is connected, and the locally oscillated carrier wave from the voltage controlled oscillator is multiplied by the received signal by a multiplier to receive the signal. The signal is synchronously demodulated.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the spread spectrum communication device of the present invention, and in this figure, A is the transmitting side and B is the receiving side. First, the configuration of the transmitting side A will be explained. A carrier wave from a carrier wave oscillator 1 is output to a frequency divider 2 and a multiplier 3. The carrier wave applied to the divider 2 is converted by the divider 2 into a clock pulse for generating a spread spectrum code.

This clock pulse is output to the spread spectrum code generator 4. The spread spectrum code generator 4 outputs a spread spectrum code synchronized with the carrier wave to the FOR circuit 5 in response to input of a clock pulse.

The FOR circuit 5 spreads the transmitted information using a spread spectrum code. This spread transmission information is multiplied by a carrier wave in a multiplier 3, modulated, and transmitted through a narrowband bandpass filter 6 and an antenna 7.

Next, the configuration of the receiving side will be described. A received signal from the antenna 8 is amplified by an amplifier 9 and output to a multiplier 10 and a carrier extraction circuit 11. A carrier wave extraction circuit 11 extracts a carrier wave component from the received signal and outputs it to a phase comparator 12. The phase comparator 12 compares the phases of the locally oscillated carrier wave from the voltage controlled oscillator 13 and the carrier wave extracted from the received signal, and outputs a control signal to the voltage controlled oscillator 13 so that they are in the same phase. The locally oscillated carrier wave from the voltage controlled oscillator 13 is output to the phase comparator 12, multiplier 10 and frequency divider 14 as described above. The multiplier 10 multiplies the received signal by the local oscillation carrier wave from the voltage controlled oscillator 13 and performs synchronous demodulation thereof. The synchronously demodulated received signal from the multiplier 10 is output to a spread spectrum code synchronous detector 15 and a pFOR circuit 16. On the other hand, the divider 14 divides the frequency of the locally oscillated carrier wave from the voltage controlled oscillator 13 and outputs a clock pulse for the spread spectrum code on the receiving side to the spread spectrum code synchronization detector 15 and the spread spectrum code generator 17. . The spread spectrum code synchronization detector 15 receives the synchronously demodulated received signal and the frequency divider 1.
The synchronization is detected using four clock pulses, and the detection signal is output to the spread spectrum code generator 17. The spread spectrum code generator 17 uses the detection signal from the spread spectrum code synchronization detector 15 and the clock pulse from the frequency divider 14 to generate a spread spectrum code that is synchronized with the spread spectrum code on the transmitting side.
Output to 6. The FOR circuit 16 despreads the received signal using this spread spectrum code and reproduces the transmitted information from the transmitting side.

As described above, on the receiving side, the carrier wave extraction circuit 11 extracts the carrier wave component from the received signal, and the phase comparator 12 extracts the carrier wave component from the local oscillation carrier wave from the voltage controlled oscillator 13. The voltage controlled oscillator 13 is controlled so that these phases are the same. As a result, the carrier wave of the received signal is transferred to the voltage controlled oscillator 1.
It is synchronously demodulated by the local oscillation carrier wave from 3. As a result, the signal-to-noise ratio (S/N ratio) regarding the received signal can be improved. Further, since the frequency and phase synchronization of the carrier wave and the synchronization detection of the spread spectrum code are separated, the time required to establish synchronization is shortened, and high-speed transmission of transmission information is possible.

A specific embodiment of the carrier extraction circuit 11 described above will be described with reference to FIGS. 2 and 3.

In order to extract a carrier wave from a two-phase modulated wave, the carrier wave extraction circuit 11 shown in FIG.
It is composed of a narrowband bandpass filter 112 that extracts a double component and a splitter 113 that outputs a carrier wave component.

The carrier extraction circuit 11 shown in FIG.
3, the multiplier 115 and the oscillator 114 convert the frequency into an easily handled intermediate frequency, the intermediate frequency band-pass filter 112 extracts components related to the carrier wave, and the multiplier 116 returns the frequency to the original frequency. This is what I did. According to this embodiment, the bandpass filter 1
12 can be constructed from a general-purpose material.

FIG. 4 shows another embodiment of the apparatus of the present invention, in which parts with the same reference numerals as in FIGS. 1 and 2 are the same. In this embodiment, a bandpass filter is provided before the amplifier 9, and the received signal is filtered to the bandwidth BW of the spread spectrum code, and then amplified by the amplifier 9, and received by the limiter 19 provided before the carrier extraction circuit 11. The amplitude of the noise component in the signal is limited, and the received signal is output to the carrier extraction circuit 1.

According to this embodiment, if the bandwidth of the bandpass filter 112 constituting the carrier extraction circuit 11 is BW2, the output of the carrier extraction circuit 11 is BW2 than the S/N ratio of the received signal.
, /BW can improve the S/N ratio by twice.

As a result, S/
Improvement in the N ratio can also be achieved in the extraction of carrier burning waves.

Furthermore, it is possible to achieve faster synchronization.

〔Effect of the invention〕

As described above, according to the present invention, a carrier wave is extracted from a received signal and the received signal is synchronously demodulated using the extracted carrier wave, so that the S/N ratio can be improved and high-speed synchronization can also be realized. can.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a carrier extraction circuit used in the spread spectrum communication device of the present invention;
FIG. 4 is a block diagram showing another embodiment of the receiving side of the apparatus of the present invention.

Claims (1)

[Claims] 1. A transmitting unit that spreads transmitted information with a spreading code having a wide bandwidth, further phase-modulates it, and transmits it, and a receiving unit that despreads the transmitted information with the same spreading code as the transmitting unit and reproduces the transmitted information. In the spread spectrum communication device, the receiver is provided with a carrier wave extraction circuit for extracting a carrier wave component from the received signal, and the carrier wave extraction circuit extracts the carrier wave component from the circuit and the local oscillation carrier wave from the voltage controlled oscillator. A phase comparator that compares the phases and controls the voltage controlled oscillator so that the phases are the same is connected, and the received signal is multiplied by a local oscillation carrier wave from the voltage controlled oscillator by a multiplier to obtain the received signal. A spread spectrum communication device characterized by synchronous demodulation. 2. In the spread spectrum communication device according to claim 1, the carrier wave extraction circuit includes a squaring circuit that generates a frequency component twice that of the carrier wave, a narrow band band-by filter that extracts a frequency component twice that of the carrier wave, and a carrier wave. A spread spectrum communication device comprising: a branching unit that outputs a component. 3. In the spread spectrum communication device according to claim 1, the carrier wave extraction circuit includes a squaring circuit that generates a frequency component twice that of the carrier wave, and a frequency conversion of the carrier wave from this circuit to an easy-to-handle intermediate frequency. Spread spectrum characterized by comprising a first multiplier and an oscillator, an intermediate frequency bandpass filter that extracts a component related to a carrier wave, a multiplier that returns to the original frequency, and a splitter that outputs a carrier wave component. Communication device.