JPS594350A - Spread spectrum communication device - Google Patents

Abstract

PURPOSE:To decrease the level difference of receiving power at a receiver from each transmitter, by setting inversely the transmission power of a transmitter to a channel in response to high or low receiving power level. CONSTITUTION:The 1st and the 2nd local signal generator frequencies fl and fs are applied with frequency conversion at a frequency converter 20 in a receiver, and a signal having a frequency apart from fi (center frequency of receiving spread spectrum signal)+mfcl (clock frequency for pseudo noise code driving) is transmitted normally from an antenna. This signal is received at the antenna in the receiver, and a control signal vc is obtained through a band pass filter 11, and a detector and control circuit 10. The control signal vc from the circuit 10 and a receiving power vtf are almost in the proportional relation, the vc is increased when the vtf is increased, and the vc is decreased when the vtf is decreased. Further, a transmission signal power vto is controlled by the vc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spread spectrum communication device, and more specifically, a transmitter/receiver that modulates a carrier wave with a signal obtained by adding pseudo noise code to information to be transmitted, and performs communication using a signal whose spectrum is spread. Regarding the configuration of

The application of the spread spectrum method to personal communication systems such as simple radio and citizen radio, and data communication for data transmission between mobile subscribers and bases is most anticipated. The problem in this case is that when a remote mobile transmitter (for example, A) is communicating with a receiver (base station), another mobile transmitter (B, for example) communicates with the receiver (base station). ) is near the receiver, a problem arises in that the signal of B interferes with the signal of A, making it difficult to separate the desired channel.

Therefore, it had the disadvantage that it was not possible to increase the number of channels to allow simultaneous calls. Conventionally, in order to solve this problem, a method has been considered in which the reception side reproduces the signals of all the channels communicating simultaneously and uses the signals to remove the inter-channel interference. However, when the number of channels is large, the device becomes extremely complex.

Therefore, it is an object of the present invention to provide a simple spread spectrum communication device that does not cause inter-channel interference as much as possible, which does not cause a large difference in reception levels between channels. There is a particular thing.

In order to achieve the above object, the present invention focuses on the fact that the cause of inter-channel interference in a receiver that communicates with multiple transmitters simultaneously is the difference in signal power level from each channel. The total transmit power of the transmitter is lowered for channels, and the transmit power of the transmitter is increased for channels with low received power levels to reduce the difference in received power levels from each transmitter at the receiver. This is what I did. In other words, a signal of a specific frequency is sent from the receiver to each transmitter, and each transmitter controls the transmission power level of the spread spectrum signal, which is the transmission signal, according to the received power level of the signal of the specific frequency. The communication device is configured to do this. Note that the clock frequency mfc for pseudo noise code driving is changed from the center frequency ft of the received spread spectrum signal so that the signal of the specific frequency does not affect the spread spectrum signal.
Let the frequency t+Ll-mfet or fI-mfc, t be separated by t (m=1, 2, 3, ="·).

Hereinafter, the present invention will be explained in detail with reference to Examples. 1st
The figure is a diagram showing the configuration of an embodiment of a spread spectrum communication device according to the present invention. In the figure, (a) shows the configuration of a mobile transmitter, and (b) shows the configuration of a receiver.

In reality, there are a plurality of transmitters, but since the configuration of each transmitter is the same, only one transmitter is illustrated for ease of explanation.

1 is a carrier wave oscillator (frequency fl), 2 is a clock oscillator (frequency mfe t), 3 is a balanced modulator, 4 is a modulo 2 adder, 5 is a frequency divider, 6 is information converted from an analog signal to a digital signal Signal source, 7 is a pseudo-noise generator (e.g. PN code generator, Gold code generator, etc.), 8
9 is a band-pass filter, 9 is an amplifier and a voltage-controlled attenuator, and a control signal ve from 10 controls the output signal power vt.

1o is a circuit that includes a detector and a control circuit, and Me changes according to the received power vtt. 11 is a bandpass filter for passing the signal from the receiver (if necessary, an amplifier is installed after that). ),
12, 13, 14, and 15 are all antennas, 16 is a band pass filter that passes the spread spectrum signal sent from the antenna 12, and 17 is fI+mfct (
1) or fI-mfct); 18 is a frequency converter; 19 is a first
local signal generator (frequency ft); 20 is a frequency converter;
21 is a demodulation section for information signal reproduction (including a despreading section, an intermediate frequency section, a code period section, a carrier wave reproduction section, a demodulation section, etc.);
22 is a second local signal generator (frequency f=), fI
is selected so that the VrO(7) frequency is f10m1Ct (or fl-mfct). That is, as shown in FIG. 2, the frequency of VrO is fI+fet*
f++uct+...l fI -fat l
Select one of the frequencies fI-2f"1....., etc. Next, the operation shown in FIG. are added modulo 2 by 4, and the carrier signal is modulated by 3) to obtain a spread spectrum signal. and this signal is transmitted to the receiver's antenna 1.
4, the signal passes through the bandpass filter 16 and is input to the frequency converter 18. The frequency is converted by the frequency converter 18 to the oscillation frequency from the first local signal generator 19, and the information signal is obtained by the demodulator for information signal reproduction. The above is the same as the conventional spread spectrum communication device, but in the present invention, the transmission power of the transmitter is controlled depending on the communication state between the transmitter and the receiver. The method is performed as follows. In the receiver, the frequency of ftLf-' is converted by the frequency converter 20, and the pf amount is 10 m from the antenna 15.
A signal with a frequency of fct (or mfcz) is always transmitted. Then, in the transmitter, this signal is received by the antenna 13, and passed through the band pass filter 11, the detector, and the control circuit 10 to obtain the control signal Va. Vt
There is a nearly proportional relationship between f and va; as vtr increases, Vc increases, and as Vtf decreases, Ve decreases. This VC then controls the VTO. That is, as shown in FIG. 3(b), when vc increases, VtO decreases, and when Ve decreases, vto increases.

This means that when the transmitter gets close to the receiver, the VTR will stop moving.
Thereby, VTO is controlled to be reduced. Conversely, as the transmitter moves farther away from the receiver, control is performed so that vtf decreases and vto increases.

In this way, the power transmitted from the transmitter is controlled according to the reception state of the power transmitted from the receiver. The above explanation was for the case where there is only one transmitter, but even if multiple transmitters exist at arbitrary positions relative to the receiver and each transmits power, the transmit power of each is controlled according to the communication status. Therefore, the reception level difference between channels can be suppressed.

Next, FIG. 3 will be explained. (a) is 9 and 1 in Figure 1.
This figure shows the detailed circuit of 0. 23 is an amplifier, 24
25 is a voltage-controlled attenuator, 25 is a detector, and 26 is a control circuit. Figure (b) is an example of the experimental results for the circuit in (a),
It shows the relationship between Ve and the attenuation amount of the voltage-controlled attenuator.

FIGS. 4(a) and 4(b) show the configuration of another embodiment of the spread spectrum communication device according to the present invention.

This is a simple type of transmitter (a) in which the transmitter does not have a carrier wave oscillator. That is, the power V transmitted from the receiver
The rO signal is received by the transmitter (a) and frequency-converted with the signal from the clock oscillator 2 to generate a carrier wave for the transmitter. The power of this carrier wave is then controlled according to the reception state of the power transmitted from the receiver.

Components that are the same as those of the apparatus in the embodiment shown in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

26 is a frequency converter, which performs frequency conversion between the signal sent from the receiver (frequency: mfeb, 6, or f+-mfct) and the signal from the clock oscillator 2 (frequency: mfcL). 27 is a pass band filter for extracting a signal component of frequency ft.

With this configuration, (1) the transmitter does not require a carrier wave oscillator, so the transmitter can be simplified; (2)
) Since there is no need for a circuit to control reception frequency fluctuations in the receiver, effects such as easier carrier wave regeneration in the receiver can be expected. Note that in FIG. 4(a), an amplifier may be connected after the bandpass filter 11 to amplify the received power.

In FIGS. 1 and 4, if a device for monitoring vtI is added, the communication status between the transmitter and receiver can be grasped. For example, since it is possible to predict cases where the received power is attenuated significantly due to multipath fading, it is possible to reduce multipath fading by slightly moving the transmitter or shifting the antenna, ensuring good communication at all times. This effect can also be expected.

According to the present invention, (1) it is possible to obtain a simple spread spectrum transmitter and a receiver that cause as little inter-channel interference as possible by controlling the power of the transmitter;

(2) It is possible to realize a configuration in which the transmitter does not require a carrier wave oscillator, so the transmitter can be simplified.

(3) With the configuration as in (2), a circuit for controlling reception frequency fluctuations of the receiver is not required, so carrier wave regeneration of the receiver becomes easy.

(4) Communication status between transmitter and receiver? Since it is also possible to monitor, it is possible to reduce the attenuation of the reception level due to multipath fading by moving the antenna on the transmitter side and the transmitter itself.

There is an effect like this.

A block diagram showing the configuration of an embodiment of a spread spectrum communication device, FIG. 2 shows a spread spectrum waveform, and FIG. 3 shows an example of the configuration and experimental results of a transmission power control section used in the above embodiment.

Claims (1)

[Claims] 1. In a spread spectrum communication device consisting of a transmitter that transmits a spread spectrum signal and a receiver that receives the spread spectrum signal, the receiver has a reception carrier frequency (fl) and a clock frequency for driving a pseudo-noise code ( mfC4) (m is an integer) and the sum or difference frequency (f
The transmitter has a means for transmitting the sum or difference frequency signal (I±mfCt) signal, and the transmitter has a means for transmitting the sum or difference frequency signal (mfct) signal, and the received power of the sum or difference frequency signal is determined by the output of the receiving means. A spread spectrum communication device comprising: control means for controlling transmission power of the spread spectrum signal in accordance with the above.