JPH027540B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a spread spectrum communication system using linear spread modulation, and more particularly to a spread spectrum communication system in which good synchronization is maintained between transmitters and receivers. .

[Conventional technology]

In recent years, the field of industrial machinery has become more systematized. Further, control devices are being distributed or centrally managed. Therefore, the importance of information transmission channels is increasing. One example is a communication system for controlling freely mobile mobile machines.

In this type of communication system, it is not effective to use wired communication when the mobile machine moves over a wide area. In addition, when a mobile machine moves in an area with a plant, using strong radio waves,
There is a concern that it may damage the plant's electronic instruments.

For this reason, the spread spectrum communication method, which allows communication using low energy level radio waves and has excellent noise resistance, is being reconsidered.

This spread spectrum communication method realizes high quality communication by converting an information signal to be transmitted into a signal with a spectrum width wider than the spectrum width specific to this information signal and transmitting the signal. More specifically, on the transmitting side, a carrier wave that is modulated with a specific code called a pseudo-noise code that has a sufficiently wider spectrum width than the information signal is modulated with the information signal and transmitted. On the other hand, on the receiving side, the transmitted information signal is selectively received by demodulating it using the same spreading code of the pseudo-noise code as on the transmitting side.

In this spread spectrum communication system, the condition is that the spreading code on the receiving side and the spreading signal included in the received signal are completely matched in phase. An example of a synchronous circuit for matching the phases is one described in Japanese Patent Application Laid-Open No. 56-31246.

[Problem that the invention seeks to solve]

In the conventional spread spectrum communication system described above, it takes a long time to establish synchronization between the transmission signal from the transmission side and the reception signal at the reception side, resulting in poor communication efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spread spectrum communication system that can shorten signal synchronization establishment time and speed up synchronization establishment.

[Means for solving problems]

The above object of the present invention is that in a spread spectrum communication system, a receiving device that receives a spread spectrum signal from a transmitting device includes a first loop circuit that establishes frequency and phase synchronization of a carrier wave of the spread spectrum signal; and a second loop circuit for detecting synchronization of the data spread spectrum code signal from which the carrier has been removed by the first loop circuit.

[Effect]

A receiving device that receives a spread spectrum signal from a transmitting device uses its first loop circuit to establish frequency and phase synchronization between the received signal and the local oscillation carrier wave on the receiving side, and then uses its second loop circuit to synchronize the frequency and phase of the received signal with the locally oscillated carrier wave on the receiving side. , the first loop circuit synchronizes the data spread spectrum code signal from which the carrier has been removed. This makes it possible to shorten the synchronization establishment time on the receiving side.

〔Example〕

The configuration of the communication system of the present invention will be explained with reference to the drawings.

The communication system of the present invention includes a transmitting device shown in FIG. 1 and a receiving device shown in FIG. 3. The configurations of this transmitting device and receiving device will be sequentially explained below.

The transmitting device shown in FIG. 1 is a communication control device 1 that serves as an interface with a control system (not shown).
connected to the control system through. The communication control device 1 outputs the transmission data signal A to an exclusive OR circuit (EOR) 2, and
Transmission start signal B and destination address signal C,
It is output to the spread spectrum code generator 3. The spread spectrum code generator 3 is configured as shown in FIG. Output to OR circuit 2. More specifically, the spread spectrum code generator 3 can select the spread spectrum code E by inputting the destination address signal C, and starts code generation by inputting the transmission start signal B. Frequency divider 4
divides the frequency of the carrier wave F output from the carrier wave oscillator 5 and outputs the basic clock pulse D described above.
Exclusive OR circuit 2 spreads transmission data signal A by spread spectrum code E. This spread transmission data signal G is multiplied by a carrier wave F from an oscillator 5 in a multiplier 6, subjected to two-phase phase modulation, and transmitted as a transmission signal H from an antenna 8 through a bandpass filter 7.

The detailed configuration of the spread spectrum code generator 3 is shown in FIG. This spread spectrum code generator 3 is composed of an initial value setter 201, a feedback shift register 202, and a shift register 203, and inputs the output of the feedback shift register 202 to the shift register 203 and generates a spread spectrum code. It has a structure that outputs E.

Next, a circuit configuration of an example of a receiving device in the communication system of the present invention will be explained with reference to FIG. Third
In the figure, a spread spectrum data signal H sent from a transmitter is received by an antenna 301, amplified by a high frequency amplifier 302, and then
Input to multiplier 303. In the multiplier 303, a voltage controlled oscillator (VCO) 30, which is a local oscillator, is applied to the data signal H.
4 is multiplied by the local oscillation carrier wave I. The output signal J from the multiplier 303 passes through a bandpass filter 305 and becomes a data spread spectrum code modulation code K from which the carrier component is removed.
This signal K is applied to the controller 30 of the voltage controlled oscillator 304.
6, output to spread spectrum code synchronization detector 307 and exclusive OR circuit 308. Local oscillation carrier wave I, which is the output of voltage controlled oscillator 304, is frequency-divided by frequency divider 309 and output as basic clock pulse L. This basic clock pulse L is output to the controller 306 of the voltage controlled oscillator 304, the spread spectrum code synchronization detector 307 and the spread spectrum code generator 310. A controller 306 of the voltage controlled oscillator 304 adjusts the voltage supplied to the voltage controlled oscillator 304 and outputs a control signal to the voltage controlled oscillator 304 to keep the phase stable. As shown in FIG. 4, the controller 306 of this voltage controlled oscillator 304 includes a filter 401, an A/D converter 402, a determination circuit 403, and a D/A converter 404.
The signal K, which is the product of the received signal H and the local oscillation wave I, is converted into a DC component signal through a filter 401, and this DC component signal is sampled at high speed by an A/D converter 402. Digitize. This is input into the judgment circuit 403, and the voltage supplied to the voltage controlled oscillator 304 through the D/A converter 404 is adjusted so that the value is always the maximum by comparing it with the value sampled before one point, thereby keeping the phase stable. control. This voltage controlled oscillator 30
The loop circuit of the controller 306 including 4 synchronizes the frequency and phase of the local oscillation carrier I and the received carrier.

The spread spectrum code synchronization detector 307 shown in FIG. 3 is connected to the shift register 50 as shown in FIG.
1. Spread spectrum code synchronization setting bit string 50
2. An exclusive OR NOT circuit (EOR) 503 and a AND NOT circuit 504 are provided, and the received code strings are sequentially sent to the input section and stored in the shift register 501. This shift register 5
The exclusive OR negation circuit 503 detects a match between the code string entered in 01 and a specific bit string of the spread spectrum code string preset in the setting bit string 502, and then a logical product negation circuit (NAND)
504, a match of all bits is detected.

The synchronization detection signal from the spread spectrum code synchronization detector 307 is output to the spread spectrum code generator 310 shown in FIG. As a result, the spread spectrum code generator 310 outputs the spread spectrum code to the exclusive OR circuit 308 using the basic clock pulse L. This exclusive OR circuit 308 despreads the received signal by inputting the spread spectrum code and outputs it. This output signal is passed through a low-pass filter 311 and reproduced as a received data signal. This received data signal is provided as a control signal for a control system connected to the receiving device side.

According to the embodiment described above, on the receiver side, the frequency and phase of the carrier wave can be synchronized by the loop circuit of the controller 306 including the voltage controlled oscillator 304, regardless of the correlation of the spread spectrum code. Therefore, the time required to establish carrier wave synchronization can be shortened. Further, after the carrier synchronization is established, the spread spectrum code synchronization detector can detect the start point of the spread spectrum code, so that the received signal can be accurately despread.

In addition, in this embodiment, in order to synchronize the frequency and phase, a high-speed PLL (Phase Locked
The synchronization establishment time can be similarly shortened by using a phase-locked loop (LOUP).

〔Effect of the invention〕

As described above, according to the present invention, the synchronization establishment of the frequency and phase of the carrier wave and the synchronization detection of the spread spectrum code are performed separately on the receiving side, so that the synchronization establishment transition from the asynchronous state to the synchronous state is carried out separately. Can be shortened. As a result, communication efficiency can be improved when performing random access communication between multiple stations.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an example of a transmitting device that constitutes the communication system of the present invention, FIG. 2 is a configuration circuit diagram of a spread spectrum code generator that constitutes the transmitting device shown in FIG. 1, and FIG. FIG. 4 is a circuit diagram of an example of a receiving device constituting the communication system of the invention, FIG. 4 is a circuit diagram of a controller of a voltage controlled oscillator constituting the receiving device shown in FIG. 3, and FIG. 5 is the circuit diagram shown in FIG. 3. FIG. 2 is a circuit configuration diagram of a spread spectrum code synchronization detector that constitutes a receiving device. 301... Antenna, 302... High frequency amplifier, 303... Multiplier, 304... Voltage controlled oscillator, 305... Bandpass filter, 306...
Controller, 307... Spread spectrum code synchronization detector, 308... Exclusive OR circuit, 309...
Frequency divider, 310...spread spectrum code generator.

Claims (1)

[Claims] 1. Transmitting means that spreads data to be transmitted using a spread spectrum code, modulates the spread transmission data signal with a carrier wave, and transmits it into the air;
A spread spectrum communication system comprising a receiving means for receiving a signal sent out by the transmitting means, despreading the received signal using a spread spectrum code, and extracting the data, the receiving means comprising: a locally oscillated carrier wave; oscillates, multiplies the locally oscillated carrier wave and the received signal to output a data spread spectrum code modulated signal from which the carrier has been removed, and adjusts the locally oscillated carrier wave so that the data spread spectrum code modulated signal is maximized. The first thing to adjust
a frequency divider that divides the frequency of the local oscillation carrier wave to generate a basic clock; detects the period of the spread spectrum code based on the data spread spectrum code modulation signal and the basic clock; a second loop circuit that generates a spread spectrum code based on a signal, despreads the data spread spectrum code modulated signal using the spread spectrum code, and extracts the data. Communication method.