JPH05167559A - Spectrum diffusion communication receiver - Google Patents

Abstract

PURPOSE:To save power consumption by taking the only signal from an inverse diffusion processing circuit and stopping the operation of the circuit when the reception intensity is powerful enough. CONSTITUTION:The inverse diffusion processing using a first pseudo noise PN1 is performed on spectrum diffusion reception signals supplied to an input terminal 10 by an inverse diffusion processing circuit 11 to send a terminal (a) to be selected of a changeover switch 15. An inverse diffusion processing circuit 12 sends the output with signals after the inverse diffusion processing using a first pseudo noise PN2 and signals from the inverse diffusion processing circuit 11 added by an adder 13 to a terminal (b) to be selected of the changeover switch 15. A signal intensity detection control circuit 14 detects the intensity of the receiving signal of the input terminal 10 to stop the switching control of the changeover switch 15 and the operation of the inverse diffusion processing circuit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication receiver, and more particularly to a spread spectrum communication receiver suitable for receiving a signal of a balanced QPSK (4 phase phase modulation) system.

[0002]

2. Description of the Related Art In recent years, the bandwidth of information is several hundred
A spread spectrum communication system, in which a modulated wave is spread over a spectrum band that is several thousand times wider, to perform communication is drawing attention. In this spread spectrum communication system, the frequency spectrum is spread by the carrier side being modulated by a PN code (pseudo noise code sequence) on the transmitter side. In the receiver, after undergoing a despreading (correlation) process using a PN code generated by a code generator having the same structure as the transmitter, baseband demodulation is performed to obtain data.

In the case of mobile communication using the spread spectrum communication system, a two-phase phase modulation system, so-called BPS
The K method is often used. This BPSK is one of the methods of transmitting a signal by changing the phase of a carrier wave. For example, by replacing 1 or -1 of data with 0 or π (180 °) of the phase of the carrier wave. To communicate. However, in actuality, the data is BPS for the purpose of making it more resistant to jamming signal interference.
There are cases where a four-phase phase modulation method, so-called QPSK method, is apparently adopted although the binary value is equivalent to K. As one form of such a QPSK method, a balanced QPSK modulation method is known.

[0004]

By the way, when such a balanced QPSK modulation method is used, the despreading process (correlation) between two types of PN codes generated by a code generator having the same structure as the transmitter is performed on the receiving side. However, there is a problem in that the circuit scale and power consumption increase.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a spread spectrum communication receiver capable of suppressing the circuit scale and reducing the power consumption.

[0006]

In a spread spectrum communication receiver according to the present invention, a carrier signal modulated by a first pseudo noise signal and a carrier signal modulated by a second pseudo noise signal are combined. In a spread spectrum communication receiver for receiving a signal transmitted by the first despreading processing means for despreading the received signal with the first pseudo noise signal, and the received signal. On the other hand, a second despreading process using the second pseudo noise signal is performed.
Despreading processing means, adding means for adding the respective outputs from the first and second despreading processing means, signal strength detecting means for detecting the strength of the received signal, and signal strength detection In accordance with the output from the means, the switching selection for selecting the output signal from the first despreading processing means when the signal strength is large, and selecting and outputting the addition output signal from the adding means when the signal strength is small. By having a means, the above-mentioned subject is solved.

[0007]

When the signal strength is high, the operation of the second diffusion processing means can be stopped, and power saving can be achieved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block circuit diagram showing a schematic structure of a demodulation unit as a main part of an embodiment of a spread spectrum communication receiver according to the present invention. In FIG. 1, a spread spectrum signal S _in is supplied to an input terminal 10. The spread spectrum input signal S _in is
For example, on the transmitter side, the carrier signal modulated by the first pseudo noise signal PN ₁ and the second pseudo noise signal PN 1
_This is a signal obtained by receiving a signal transmitted by combining the carrier wave signal modulated by ₂ .

The input signal S _in is composed of a first despreading processing circuit 11 for carrying out a spectrum despreading process with the first pseudo noise signal PN ₁ and the second pseudo noise signal PN ₂
Are sent to the second despreading processing circuit 12 which performs the spectrum despreading processing. The respective outputs from the first and second despreading processing circuits 11 and 12 are added by the adder 13
Sent to and added. The output signal from the first despreading processing circuit 11 is input to the selected terminal a of the changeover selection switch 15,
The output signal from the adder 13 is sent to each selected terminal a of the changeover selection switch 15. The input signal S _in is sent to the signal strength detection control circuit 14.
The signal strength detection control circuit 14 controls the changeover selection switch 15 according to whether the signal strength (reception strength) of the input signal S _in is above or below a certain threshold. That is,
When the signal strength is sufficiently strong, the changeover selection switch 15 is changed over and connected to the selected terminal a side to connect the first despreading processing circuit 1
1 is sent to the output terminal 16, and when the signal strength is less than or equal to the threshold value, the changeover selection switch 15 is connected to the selected terminal b side and the addition output signal from the adder 13 is sent to the output terminal 16. ing.

Further, when the received signal strength is sufficiently strong and the signal strength detection control circuit 14 controls the switching to the selected terminal a side of the switch selection switch 15, the despreading circuit 12 receives an operation stop signal (for example, power off). By sending a control signal or the like), the operation of the despreading circuit 12 can be stopped and unnecessary power consumption can be suppressed.

By the way, as a concrete configuration on the transmitter side for transmitting a signal to such a spread spectrum communication receiver, there is, for example, one as shown in FIG. FIG. 2 shows a specific example of a so-called balanced QPSK type spread spectrum communication transmitter, and it is assumed that ± 1 data x (t) is input to the input terminal 20. This input data x (t) is distributed in two, and the exclusive OR (E
x-OR) circuits 23 and 24. Ex-OR
In the circuit 23, the PN code PN ₁ (t) from the first PN code (pseudo noise code sequence) generator 21 is supplied,
The exclusive OR with the input data x (t) is taken, and Ex
In the OR circuit 24, the second PN code generator 22
The PN code PN ₂ (t) is supplied and the exclusive OR of the PN code PN ₂ (t) and the input data x (t) is taken to perform diffusion processing. These Ex-OR circuits 23, 2
The outputs from 4 are sent to multipliers 27 and 28, respectively. In the multiplier 27, the oscillation output signal ω _C from the oscillator 25 is directly supplied and multiplied by the signal spread by the PN code PN ₁ (t), and in the multiplier 28, the oscillator 25
A signal obtained by delaying the oscillation output signal ω _C from π / 2 by the π / 2 phase shifter 26 is multiplied by the signal spread by the PN code PN ₁ (t). The multiplication output signals from the multipliers 27 and 28 are sent to the adder 29 to be added and taken out via the output terminal 30.

When the above processing is expressed by a mathematical expression, the transmission output S _TR (t) is as follows. S _TR (t) = (PN ₁ (t) cos (ω _C (t)) + PN ₂ (t) sin (ω _C (t))) (1) Further, the balanced QPSK signal extracted from the output terminal 30. Is transmitted after being subjected to appropriate processing required for transmission.

Next, FIG. 3 shows a more specific structure of the embodiment shown in FIG. 1, and parts corresponding to those in FIG. 1 are designated by the same reference numerals. In the configuration shown in FIG. 3, a part of the received signal input from the input terminal 10 is sent to the signal strength detection circuit 59 of the signal strength detection control circuit 14. The oscillator 41 is set to oscillate at a frequency ω _L substantially the same as the oscillation frequency ω _C of the oscillator 25 on the transmitter side. The output signal from the oscillator 41 is divided into two, one is sent to the multiplier 43 as it is and multiplied by the input signal, and the other is delayed by π / 2 phase by the π / 2 phase shifter 42 and is then multiplied by the multiplier 44. It is sent and multiplied by the input signal. By these multiplication processes, it is considered that each signal becomes an IF (intermediate frequency) signal of approximately 0 Hz, so that it is possible to perform subsequent signal processing digitally. Such a method is called a quasi-synchronous detection method.

Output signals from the multipliers 43 and 44 are respectively divided into two after passing through LPFs (low-pass filters) 45 and 46, respectively. That is, when the output signal from the LPF 45 is S _A and the output signal from the LPF 46 is S _B , these signals S _A and S _B are each divided into two, and the first despreading (correlation) processing circuit 11 And the second
Is sent to the despreading processing circuit 12. In the first despreading circuit 11, the signal S _A is sent to the Ex-OR (exclusive OR) 47 and the signal S _B is sent to the Ex-OR circuit 48, and the first signal on the transmitting side is sent. PN code generator 5 having the same structure as PN code (pseudo noise code sequence) generator 21
The exclusive OR with the PN code PN ₁ (t) generated by ₁ is taken respectively, and then the LPFs 49 and 50 are respectively passed. Thereby, the first PN code PN ₁
This means that despreading by (t) was performed. Similarly, in the second despreading circuit 12, the signal S _A is Ex-OR
The circuit 52 and the signal S _B are respectively sent to the Ex-OR circuit 48, and the PN code PN ₂ (t) from the PN code generator 56 having the same structure as that of the second PN code generator 22 on the transmission side.
And the exclusive OR with the LPFs 49 and 50, respectively.
To pass the second PN code P
Despreading with N ₂ (t) is performed.

The input signal of the LPF 49 is x (t) (PN ₁ (t) cos (φ (t)) + PN ₂ (t) sin (φ (t))) PN ₁ (t) = x (t) (PN ₁ (t) PN ₁ (t) cos (φ (t)) + PN ₁ (t) PN ₂ (t) sin (φ (t))) (2) where φ (t) = ω _C (t) − ω _L (t). Passing this through LPF49, PN ₁ (t) PN ₁
Since (t) = 1, the first term in parentheses in the above equation (2) remains, but since PN ₁ (t) and PN ₂ (t) are completely different PN code sequences, The second term will be cut. Therefore, the output signal from the LPF 49 becomes x (t) cos (φ (t)) (3).

Similarly, the input signal of the LPF 50 is x (t) (PN ₁ (t) cos (φ (t) + π / 2) + PN ₂ (t) sin (φ (t) + π / 2) ) PN ₁ (t) = x (t) (− PN ₁ (t) PN ₁ (t) sin (φ (t)) + PN ₁ (t) PN ₂ (t) cos (φ (t)))… ( 4), and like the above, only the first term in the parentheses of the equation (4) remains, so the output signal from this LPF 50 is -x (t) sin (φ (t)) (5) Become.

The LPF 54 is calculated in the same manner as above.
Output signal is x (t) sin (φ (t)) (6), and the output signal of the LPF 55 is x (t) cos (φ (t)) (7).

The respective output signals from the LPF 49 and the LPF 54 are added by the adder 57, and the respective output signals from the LPF 50 and the LPF 55 are added by the adder 58 to one sign (for example, LPF).
The sign of the output signal from 55) is inverted and added.
The normal balanced QPSK signal reception method is to send this signal to, for example, a BPSK demodulation unit to demodulate the data.

However, as is clear from the pair of equations (3) and (5) and the pair of equations (6) and (7), equations (3) and (6) are the same. Since the information is information and the equations (5) and (7) are the same information, the first PN code PN ₁ (t) or the second PN code PN _{2 is used.}
Although despreading with any one of the PN codes in (t) reduces the signal strength by half, it shows that the subsequent BPSK demodulation is possible. In other words, this means that the energy of the received signal is lowered by 3 dB and is sent to the BPSK demodulator.

In the embodiment of the present invention, attention is paid to this point, and when the received signal strength is sufficiently strong, despreading is performed by the PN code of only _one of PN ₁ (t) or PN ₂ (t), and the signal strength is the above. When it is less than the threshold value, the same despreading method as the conventional one using both PN codes of PN ₁ (t) and PN ₂ (t) is adopted. For this reason, the signal strength detection circuit 59 detects the strength of the received signal and sends it to the control circuit 60. The control circuit 60 sufficiently demodulates the reception strength above a certain threshold, that is, even if the signal strength drops by 3 dB. If it is determined that it is possible, the control signal stops the operation of the generator 56 of one PN code, for example, the second PN code PN ₂ (t), and the other PN code, for example, the first PN code PN. ₁ (t)
Therefore, only the signal subjected to the despreading process is taken out and sent to the next demodulation section.

Specifically, the output signal from the LPF 49 of the first despreading processing circuit 11 is to the selected terminal a of the changeover switch 61 of the changeover switch circuit 15, and the output signal from the LPF 50 is the selection of the changeover switch 62. The output signal from the adder 57 of the adder circuit 13 is sent to each terminal a and the selected terminal b of the changeover switch 61 of the changeover switch circuit 15 is output.
Further, the output signal from the adder 58 is sent to each of the selected terminals b of the changeover switch 62. The output signals from the changeover switches 61 and 62 of the changeover switch circuit 15 are taken out through output terminals 63 and 64, respectively. The output signal from the signal strength detection circuit 59 is sent to the control circuit 60. From the control circuit 60, the switch changeover control signal is sent to the changeover switches 61 and 62 of the changeover switch circuit 15, and the operation stop signal is sent. It is sent to each of the second PN code generators 56. Output terminal 6
The output signals from 3, 64 are sent to, for example, a so-called BPSK demodulation circuit and subjected to data demodulation processing.

In the control circuit 60, the signal strength detected by the signal detection circuit 59 is equal to or more than the threshold value which can be effectively demodulated by the demodulation unit in the subsequent stage even if the despread output signal is reduced by 3 dB as described above. When it is determined that the operation of the second PN code generator 56 is stopped,
1 and 62 are switched and connected to the selected terminal a side, respectively. At this time, only the signal despread by the first PN code PN ₁ (t) is taken out from the output terminals 63 and 64.
On the other hand, if the signal strength detected by the signal detection circuit 59 is low and the despread output signal is reduced by 3 dB, there is a possibility that effective demodulation cannot be performed.
While controlling the second PN code generator 56 to the operating state, the addition output of each signal despread by both PN codes PN ₁ (t) and PN ₂ (t) is taken out from the output terminal 64. Switch control to.

Therefore, under the condition that the reception intensity is sufficiently strong, the operation of one PN code generator is stopped to perform the data demodulation, whereby a large power saving can be achieved. By the way, in consideration of the difference in reception performance between the case of using such two types of PN codes and the case of using one type of PN code, it is possible to rank the receivers or reception services. is there. That is, although a receiver is normally owned by a general user, a receiver that performs despreading processing with two types of PN codes and a receiver that performs despreading processing with only one type of PN code are created, A service that teaches two types of PN codes and one type of P depending on what is called a high-end model and a popular model, and a broadcast reception contract.
Differentiation can be achieved with a service that teaches only N codes.

The present invention is not limited to the above embodiment, but the first and second PN code generators may be replaced with each other.

[0025]

As is apparent from the above description, according to the spread spectrum communication receiver of the present invention, the received signal is subjected to despreading processing by the first and second pseudo noise signals. The output obtained by adding each signal obtained and the output obtained by despreading with one pseudo-noise signal are switched and controlled according to the intensity detection output of the received signal and taken out and sent to the demodulator. Therefore, when the signal strength is sufficiently high, power consumption can be saved by stopping the despreading processing operation due to the other pseudo noise.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a main part of an embodiment of a spread spectrum communication receiver according to the present invention.

FIG. 2 is a block circuit diagram showing a schematic configuration of a main part of a transmitter that sends a signal to the receiver of the embodiment.

FIG. 3 is a block circuit diagram showing an example of a more specific configuration of the embodiment.

[Explanation of symbols]

 11 ... 1st despreading processing circuit 12 ... 2nd despreading processing circuit 13 ... Adder 14 ... Signal strength detection control circuit 15 ...・ Changeover switch

Claims (1)

[Claims] 1. A spread spectrum communication receiver for receiving a signal that is transmitted by combining a carrier signal modulated by a first pseudo noise signal and a carrier signal modulated by a second pseudo noise signal, First despreading processing means for despreading the received signal with the first pseudo noise signal, and despreading processing with the second pseudo noise signal for the received signal. Second despreading processing means, adding means for adding the respective outputs from the first and second despreading processing means, a signal strength detecting means for detecting the strength of the received signal, and this signal According to the output from the intensity detecting means, the output signal from the first despreading processing means is selected when the signal strength is high, and the addition output signal from the adding means is selected and output when the signal strength is low. Spread spectrum communication receiver; and a switching selection means for.