JPH0897799A - Spread spectrum transmitter-receiver - Google Patents

Abstract

PURPOSE: To realize the spread spectrum communication system adopting the time-division duplex system. CONSTITUTION: The transmitter-receiver is provided with an inverse spread circuit 4 applying inverse spread processing to a received spreading spectrum signal by using a spreading code from a spreading code generator 2, a spread circuit applying spread spectrum processing to a signal subject to information modulation by using a spreading code from the spreading code generator 3, and an antenna switch 10 selecting the transmission of the spreading spectrum signal received by the use of an antenna 1 or the transmission of the spreading spectrum signal generated by the spread circuit 7 to the antenna 1. Then the antenna switch 10 is switched in time division in response to a switching control signal S to attain time division duplex communication and the spreading code outputted from the spreading code generating circuits 2, 3 is initialized synchronously with the switching control signal S to set the spreading code to the same stater for the sender side and the receiver side thereby applying inverse spread processing to the spreading signal immediately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum transmitter / receiver for time division duplexing.

[0002]

2. Description of the Related Art In the wireless communication system, the most proven system is Frequency Division Duplex (FDD) which uses different frequencies for transmission and reception. In this system, station A and station B shown in FIG. 5 have the system configurations shown in FIG. 6, respectively, and two waves of frequency f1 for transmission and frequency f2 for reception are used. Here, in FIG. 6, 1 is an antenna, 2 and 3 are provided for transmission and reception, respectively, and a PN code generator for generating a PN code as a spread code and 4 are PN codes from the PN code generator 2. , A despreading circuit for despreading a spread spectrum signal received by the antenna 1 using 5, an information demodulating circuit for demodulating the despread signal to obtain an information signal, 6 an information modulating circuit for modulating the information signal, Reference numeral 7 is a spreader circuit for performing spread spectrum processing on the information modulation signal using the PN code from the PN code generator 3. The spreader circuit 7 and the despreader circuit 4 are both connected to the antenna 1.

In such an FDD system, a wide band is required to secure a large number of channels, and the effective utilization rate of radio waves is unavoidable. Therefore, recently, in order to make effective use of radio waves, a time division duplexing method (TDD: Time Div
ision Duplex) has been introduced.

[0004]

When the TDD system is introduced into spread spectrum communication, the processing time during despreading becomes a problem. In other words, in the TDD system, switching between transmission and reception is performed at a timing of several ms, so it is necessary to perform despreading within this time. Therefore, a high-speed reception synchronization system is required, and it is difficult to apply the conventional spread spectrum reception system to the TDD system as it is.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a spreading code generator for generating a spreading code, a despreading circuit for despreading a spread spectrum signal received using the spreading code from the spreading code generator, A spread circuit for spread spectrum processing a signal information-modulated using a spread code from the spread code generator, and a spectrum spread signal received by an antenna is sent to the despread circuit or a spectrum generated by the spread circuit. In a spread spectrum transmission / reception device that includes an antenna switch that switches whether to transmit a spread signal to an antenna, and switches the antenna switch to time division according to a switching control signal to perform time division recovery, in synchronization with the switching control signal. An initial setting means for initially setting a spread code output from the spread code generating circuit to a predetermined state is provided, and It is intended to solve the problem.

[0006]

In the present invention, the spreading code is initially set to a predetermined state by the initial setting means in synchronization with the control signal for switching the antenna switch, so that the spreading code is set to the same state on the transmitting side and the receiving side at the same time. Therefore, on the receiving side as in the conventional case, the synchronization time for generating the spreading code on the transmitting side is unnecessary, and the spread spectrum signal received immediately can be despread.

[0007]

1 is a block diagram showing a configuration of an embodiment of the present invention. An antenna 1, a PN code generator 2 for transmitting and receiving, and generating a PN code as a spread code are shown.
And 3, a despreading circuit 4 that despreads the spread spectrum signal received by the antenna 1 using the PN code from the PN code generator 2, an information demodulation circuit 5 that demodulates the despread signal to obtain an information signal. The information modulation circuit 6 that modulates the information signal and the spreading circuit 7 that spreads the information modulation signal using the PN code from the PN code generator 3 have the same configurations as those of the related art shown in FIG.

Here, the despreading circuit 4 and the spreading circuit 7 are provided.
An antenna switch 10 for switching between transmission and reception is provided between the antenna 1 and the antenna 1, and the antenna switch 10 is controlled by a switching control signal S from the CPU 11. Specifically, as shown in FIG. 4, when the control signal S is at the H level, the antenna switch 10 is switched to the T side, and the spread circuit 7 sends the spread spectrum signal to the antenna 1 to perform the transmission operation (TX). When the control signal S is at the L level, the antenna switch 10 becomes R
To the despreading circuit 4, the spread spectrum signal received by the antenna 1 is sent to the despreading circuit 4.
X) is possible. In addition, in the TDD system, station A and station B are designed so that station B is the receiving side when station A is transmitting, and station B is the transmitting side when station A is receiving. As shown in 4A and 4A, the switching control signal S in which H and L are completely opposite to each other is input to each antenna switch 10.

Further, in the present embodiment, an initial setting circuit 12 for initializing the PN code generated from the PN code generation circuits 2 and 3 to a predetermined state in synchronization with the switching control signal S from the CPU 11 is provided. . That is, as shown in FIG. 2, the PN code generation circuits 2 and 3 receive the shift register 15 including three D flip-flops and the outputs of the first stage and the third stage of the shift register to output one stage of output. It is composed of an exclusive OR gate 16 which returns to the input of the eye and outputs the output of the third stage as a PN code. Therefore, the seven states shown in FIG. 3 form a code sequence having one cycle.

Each D flip-flop of the shift register 15 is provided with preset terminals PR1, PR2, PR3 for initial setting, and the initial setting circuit 12 synchronizes with the switching control signal S from the CPU 11. To the preset terminal of each D flip-flop,
It is configured to supply a preset signal for setting the PN code to a predetermined state.

In the TDD system, when initial synchronization is established,
As described above, since the transmission and reception timings are alternately switched in synchronization with the switching control signal S between the A station and the B station of the communication partner, the initial setting circuit 11 synchronizes with the switching control signal S and the PN code is transmitted. When the preset signal is supplied to the shift register 15 of the generation circuits 2 and 3, the A station and the B station are
At the same time, the PN code is set to a predetermined state, here state 1.

Therefore, in the A station on the transmitting side, the timing of the PN code is "1110100", and the information modulation signal is subjected to spread spectrum processing in the spreading circuit 7 in this time series and transmitted from the antenna 1 via the antenna switch 10. It The transmitted spread signal reaches the receiving side B station with almost no delay, and the received spread signal is input to the despreading circuit 4 via the antenna switch 10 at the B station. Similarly to the station A, the station B on the receiving side sets the PN code to the state 1 by the initial setting circuit 12 in synchronization with the switching control signal S, so that the timing of the PN code is "11101".
00 ", which is the same as on the transmitting side, and the PN code and the received spread signal are despread by the despreading circuit 4. Therefore, the receiving side can surely obtain the PN code at the timing that matches the transmitting side without providing any special synchronizing means, and the high-speed despreading process can be executed by this PN code.

Of course, it is not necessary to limit the state of initial setting to state 1, and the timing of initial setting may be shifted between transmission and reception in consideration of transmission delay. For example, transmission may be initially set to state 1 and reception may be initially set to state 2. In order to establish the initial synchronization,
For example, a burst frame signal for establishing initial synchronization may be transmitted before synchronization is established, and synchronization may be established by the same burst signal being returned from the other party.

[0014]

According to the present invention, the synchronization of the spreading codes on the transmitting side and the receiving side is established almost instantaneously, and therefore, high-speed despreading processing is possible and a TDD spread spectrum communication system can be realized. become.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a PN code generator in the embodiment.

FIG. 3 is a diagram showing a state of a PN code output from the PN code generator of the embodiment.

FIG. 4 is a timing chart showing switching between transmission and reception in the TDD system.

FIG. 5 is a block diagram showing a wireless station that implements the TDD scheme.

FIG. 6 is a block diagram showing a conventional TDD spread spectrum transmitting / receiving apparatus.

[Explanation of symbols]

 1 Antenna 2, 3 PN Code Generator 4 Despreading Circuit 5 Information Demodulation Circuit 6 Information Modulation Circuit 7 Spreading Circuit 10 Antenna Switch 11 CPU 12 Initial Setting Circuit 15 Shift Register

Claims (1)

[Claims] 1. A spread code generator for generating a spread code,
A despreading circuit that despreads a spread spectrum signal received using a spreading code from the spreading code generator, and a spreading circuit that performs spread spectrum processing on a signal information-modulated using the spreading code from the spreading code generator. And an antenna switch for switching between transmitting the spread spectrum signal received by the antenna to the despreading circuit or transmitting the spread spectrum signal generated by the spreading circuit to the antenna,
In a spread spectrum transmission / reception apparatus for performing time division recovery by switching the antenna switch to time division according to a switching control signal, a spreading code output from the spreading code generation circuit in a predetermined state is synchronized with the switching control signal. A spread spectrum transmission / reception device characterized by comprising initial setting means for making an initial setting.