JPH0514314A - Receiver for spread spectrum communication - Google Patents

Abstract

PURPOSE:To reduce the effect of interference between antennas by using plural reception antennas in the communication system in which a same spread spectrum modulation signal is sent from plural antennas. CONSTITUTION:A reception signal from reception antennas 4, 8 is directly applied to one input of differential amplifier circuits 10, 12 and the reception signal via attenuators 9, 11 is fed respectively to the other input. A difference component signal from the differential amplifier circuit 10, 12 is respectively fed to an amplitude detection circuit 13, 14 and its detection signal is fed to a comparator circuit 15. A switch 16 is selected in response to the comparison result to select a differential component signal having a larger amplitude level and it is outputted to a post-stage demodulation circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of receiving devices suitable for a spread spectrum communication system in which a plurality of transmitting antennas are arranged and the same spread spectrum modulated signal is transmitted from each antenna in order to enhance a receiving electric field in a wide range. The present invention relates to a spread spectrum communication receiver using an antenna.

[0002]

2. Description of the Related Art The spread spectrum communication system is capable of communicating over a relatively long distance even with weak radio waves, and FA (Factoyy Au)
It is applied to wireless control of mobile vehicles by radio.

FIG. 5 is an explanatory diagram of a conventional fixed (base) station A and mobile station P based on a spread spectrum communication system. In the fixed station A, the spread spectrum modulation signal 1 is amplified by the high frequency amplification stage 2 and transmitted from the transmission antenna 3. In the mobile station P, the spread spectrum signal obtained by amplifying the received signal from the receiving antenna 4 by the high frequency amplifier 5 is added to a demodulation circuit (not shown) in the subsequent stage.

Generally, in a factory to which an FA based on the above-mentioned spread spectrum communication system is applied, the reception electric field area due to the transmission of the fixed station assumes that the reception antenna of the mobile station is omnidirectional, a circle centering on the antenna, or the antenna. It is often rectangular rather than square, which is easy to cover.

However, in order to make the rectangular region have a certain electric field strength or more, the output of the high frequency amplification stage 2 is fed to the two antennas 3 and 7 in the fixed station A as shown in FIG. When the position is close to the antenna 3 like P01, the electric wave from the antenna 3 is used, and when the position is close to the antenna 7 like P02, the electric wave from the antenna 7 is used to obtain the electric field strength. Makes it possible to receive the entire long and narrow electric field region indicated by the diagonal lines.

[0006]

However, in the conventional spread spectrum communication system shown in FIG. 6 as described above, the radio waves from both antennas are strong in the shaded area near the midpoint of the antennas 3 and 7. Cause interference. That is, the polarities of both antennas are reversed in units of wavelength of the frequency of the radio wave used here, and the electric field strength is significantly reduced.Therefore, when the mobile receiving station passes through this area, communication is disabled. Is likely to occur.

An object of the present invention is to reduce the influence of interference between antennas in a spread spectrum communication system in which a plurality of antennas fed with the same spread spectrum modulated signal are used to enhance the received electric field strength in a wide range. Another object of the present invention is to provide a spread spectrum communication receiver improved.

[0008]

In order to achieve the above object, the present invention is directed to a plurality of receiving antennas arranged at a predetermined interval, and a spread spectrum modulated signal transmitted by the above antennas is received by the same antenna as the transmitting side. In a receiver for spread spectrum communication having demodulation means for demodulating with a spread code to obtain a spread spectrum demodulated signal, a signal obtained by attenuating a received signal from one of the antennas by a predetermined level, and a received signal from the other antenna. Difference component signal output means for obtaining a difference component signal, a detection means for amplitude-detecting the difference component signal to obtain a detection signal, and a difference component signal having a higher amplitude level based on the detection signal for demodulation Selecting means for outputting to the means.

[0009]

In the receiving apparatus of the present invention, the received signal from one of the plurality of receiving antennas is attenuated by a predetermined level,
The difference component with the received signal from the other antenna is taken, and the obtained difference component signal is amplitude-detected. The detected signals are compared and the difference component signal having the higher amplitude level is selected and output to the demodulation means.

[0010]

Embodiments of the present invention shown in the drawings will be described below.
FIG. 1 shows an embodiment of a receiver for spread spectrum communication according to the present invention. The present embodiment is a receiving apparatus suitable for a communication system in which a plurality of transmitting antennas are arranged in order to increase the receiving electric field in a wide range and the same spread spectrum modulated wave is radiated from each antenna.

When the above-mentioned modulated wave is received by the omnidirectional antenna, radio waves from each antenna interfere with each other in the vicinity of the midpoint of each antenna, resulting in poor reception. Therefore, in the present invention, a plurality of receiving antennas are used, the received signals from the respective antennas are calculated, and an output having the maximum amplitude level is selected so as to be equivalently a directional antenna and is supplied to the demodulating means to supply information. Restore.

In FIG. 1, 4 and 8 are receiving antennas arranged at intervals d, 9 and 11 are attenuators that attenuate received signals from the antennas 8 and 4, respectively, to a predetermined level, and 10 and 12 are attenuated by the attenuators. A differential amplifier (or transformer) for obtaining a difference component signal between the signal from the one antenna and the signal from the other antenna, and 13 and 14 are amplitude detection circuits for detecting the amplitude level of the difference component signal,
Reference numeral 15 is a comparison circuit for comparing the difference component signals, and 16 is an electronic switch for selecting the difference component signal having a higher amplitude level according to the comparison result and outputting the difference component signal to a demodulation means (not shown).

If the receiving antennas 4 and 8 are, for example, simple rod-shaped antennas, the directivity of each is a circle as described above, and is non-directional. Assuming that the distance d between the antennas is the wavelength λ of the reception band (λ is widened), λ /
The number of received signals from the antennas 8 and 4 (spread spectrum modulated signal) is 4 or less, and is directly applied to one input of the differential amplifiers 10 and 12, respectively, and to the other input via attenuators 9 and 11. By thus attenuating the amplitude level of the received signal by the attenuators 9 and 10 to a predetermined level, for example, the equivalent antenna directivity of the output of the differential amplifier 10 becomes the solid line a in FIG. The shape of this directivity is determined by the distance d between the antennas 4 and 8 and the amount of attenuation by the attenuator 9.

On the other hand, the equivalent directivity of the output of the differential amplifier 12 is the broken line b in FIG. The difference component signals output from the differential amplifiers 10 and 12 are sent to the amplitude detection circuits 13 and 14 to detect the amplitude levels thereof, and the detection signals are added to the comparison circuit 15. The comparison circuit 15 compares the amplitude levels of the difference component signals and, in accordance with the result, the differential amplifier 10,
In order to select the one having a larger amplitude level among the difference component signals output from 12, the switch 16 is switched by the pulse P0, and the selected difference component signal is output to the demodulation means (not shown) in the subsequent stage.

It should be noted that, for example, in a rectangular room, when the moving vehicle (station) moves only in the longitudinal direction with respect to two transmitting antennas, the configuration of the embodiment of FIG. 1 is sufficient. When an antenna is installed or the moving vehicle takes various directions, it is not sufficient to use the directivities of a and b in FIG.

FIG. 3 shows another embodiment of the present invention suitable for such a case. This embodiment is a pair of antennas P1 and P2 shown in FIG.
In addition to this, there is another pair of antennas P3 and P4 arranged in a direction orthogonal to this, and the difference component signals generated from the received signals from the respective antennas are switched to the switches 16 and 17.
The output selected as described above by the input terminals I1, I
Add to 2. In FIG. 3, 18 and 19 are amplitude detection circuits, 20 is a comparison circuit, and 21 is an electronic switch.

The difference component signals from the respective antenna systems selected by the switches 16 and 17 are amplitude detection circuits 18 and 1.
At 9, the amplitude level is further detected, the respective detection signals are given to the comparison circuit 20, the amplitude levels are compared, and the switch 21 is switched according to the result, and the difference component signal having the larger amplitude level. Is selected and output to the demodulation means.

FIG. 4 illustrates the directivity of the combination of the antenna systems P1 and P2 and the combination of P3 and P4. This drawing is a conceptual one, and it is sufficient that another set of patterns a and b in FIG. 2 is provided orthogonal to these.

[0019]

As described above, according to the receiving apparatus of the present invention, when a mobile station having a plurality of receiving antennas receives in the area where the same spread spectrum modulated signal is radiated by a plurality of transmitting antennas. The high electric field of the transmitting antenna can be automatically received, the reception in the state where the electric fields of the respective antennas are equal is eliminated, and the mobile station can always be receivable.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a receiving apparatus of the present invention.

FIG. 2 is a diagram showing equivalent antenna directivities of difference component signals in the embodiment of FIG.

FIG. 3 is a block diagram showing another embodiment of the receiving apparatus of the present invention.

FIG. 4 is a diagram showing a directivity pattern of an antenna in the embodiment of FIG.

FIG. 5 is an explanatory diagram of a conventional transmission / reception system by a fixed station and a mobile station.

FIG. 6 is an explanatory diagram of expansion of a reception area by adding an antenna in FIG.

[Explanation of symbols]

 4,8 Reception antenna 9,11 Attenuator 10,12 Differential amplifier 13,14 Amplitude detection circuit 15 Comparison circuit 16 switch

Claims (1)

Claim: What is claimed is: 1. A plurality of receiving antennas arranged at predetermined intervals, and a spread spectrum modulation signal transmitted by the antenna is received by the antenna and demodulated by the same pseudo spread code as the transmitting side. In a spread spectrum communication receiver including a demodulation unit for obtaining a signal, a difference component for obtaining a difference component between a signal obtained by a predetermined level attenuation of a reception signal from one of the antennas and a reception signal from the other antenna. A signal output means, a detection means for amplitude-detecting the difference component signal to obtain a detection signal, and a selection means for selecting a difference component signal having a higher amplitude level based on the detection signal and outputting the selected difference component signal to the demodulation means, A spread spectrum communication receiver comprising: