JP2806921B2 - Diversity receiver for spread spectrum communication system. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diversity receiver for a spread spectrum communication system.

[0002]

2. Description of the Related Art Diversity technology using a plurality of antennas is used to reduce the influence of multipath on the receiver side of a spread spectrum communication signal. FIG. 5 shows a receiver of this type of spread spectrum communication system. The signal input to the first antenna 1 is demodulated by a first high-frequency demodulator 4, and the signal input to the second antenna 2 is demodulated by a second high-frequency demodulator 5, and each signal is transmitted to a rake receiver 6 Input and composite. An example of a spread spectrum communication system using such a receiver is described in JP-A-7-131395 and the like.

[0003]

In the above-mentioned conventional receiver, since the input signal of each antenna is processed by only one high-frequency demodulator, one of the two high-frequency demodulators fails. However, the diversity effect cannot be obtained, and the deterioration of the communication quality cannot be avoided.

[0004] It is an object of the present invention to prevent a deterioration in speech quality due to a failure of a high-frequency demodulator in a spread spectrum communication system receiver.

[0005]

Means for Solving the Problems] diversity receiver of the spread spectrum communication system of the present invention; either the same source
High frequencies transmitted from each and containing uncorrelated multipath components
A first antenna and a second antenna respectively for receiving signals;
Tena and; perform a combination of the two high-frequency signals received by each of said first antenna and said second antenna, and RF-combining-distributor for 2 distributes the combined signal; the RF-combining and distribution Amplification, frequency conversion, band limitation, baseband signal output from the first output terminal of the device
And a first high-frequency demodulator for performing analog-to-digital signal conversion and amplification and frequency conversion of a signal output from a second output terminal of the high-frequency signal synthesizer / distributor.
Conversion, band limiting, conversion to baseband signals, and
A second high-frequency demodulator for performing log-to-digital signal conversion processing ; and a plurality of finger circuits ;
According to a fault occurrence state of the modulator and the second high-frequency demodulator.
The output signal of the first high-frequency demodulator and the second high-frequency demodulator
Either or both of the high-frequency demodulator output signals
As input, multipath of desired signal from input signal
A rake receiver that extracts components, synchronizes them, and performs addition and synthesis .

[0006]

According to the present invention, since the signal components of the two independent antennas are also input to the other high-frequency demodulator side where no failure has occurred, the rake receiver inputs the signal components from the two antennas. The multipath components can be synchronized and added. As described above, even if a failure occurs in one system of the high-frequency demodulator, the multipath component input from the antenna of the failed system is not lost, so that the multipath characteristic of the spread spectrum communication system (CDMA system) is not lost. Excellent speech quality can be provided without impairing the feature of improving speech quality by adding signals.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a diversity receiver (hereinafter abbreviated as CDMA receiver) 10 of a spread spectrum communication system according to the present invention. FIG. 2 is a diagram showing an example of a delay distribution of a multipath signal input from the antenna 1 system at the input terminal 301 of FIG. FIG. 3 is a diagram showing an example of a delay distribution of a multipath signal input from the antenna 2 system at the input terminal 302 of FIG. FIG. 4 is a diagram showing a delay distribution of a multipath signal appearing at the output terminal 303 and the output terminal 304 of the high frequency signal synthesizer / distributor 3 of FIG.

[0010] A spread spectrum communication signal (C) transmitted wirelessly from an opposite CDMA transmitter (not shown).
DMA signal) passes through a plurality of paths (multi-path)
The antenna reaches the antenna 1 and the antenna 2 of the MA receiver 10. It is assumed that a signal subjected to multipath fading is input from the antenna 1 and the delay of the input multipath signal has a distribution shown in FIG. On the other hand, it is assumed that a signal subjected to multipath fading is also input from the antenna 2, and the delay of the input multipath signal has a distribution shown in FIG. Here, it is assumed that there is no correlation between the antenna 1 and the antenna 2.

The input terminal 30 of the high frequency signal synthesizer / distributor 3
1 and the input terminal 302 of the signal A1 of the antenna 1
, The signal A2 of the antenna 2 is output to the output terminal 303 and the output terminal 304 after the power is divided into two. The high-frequency signal synthesizing / distributing device 3 can be constituted by a well-known appropriate technique, for example, a hybrid ring.
It is published on page 52, etc. of the first print on the 0th). Therefore, as shown in FIG. 4, the signal of antenna 1 and the signal of antenna 2 are combined and output to output terminal 303 (signal B1), and the signal of antenna 1 and the signal of antenna 2 are similarly output terminal 304. Are combined and output (signal B2).

The signals B1 and B2 output from the output terminals 303 and 304 are supplied to the high frequency demodulator 4 and the high frequency demodulator 5
Respectively. Each of the high-frequency demodulators 4 and 5 converts an input signal into a baseband signal, removes an interference signal,
Necessary processing such as a Nyquist filter for eliminating intersymbol interference is performed. Specifically, amplification of a high-frequency signal level, frequency conversion, removal of an interference wave, conversion of an analog signal to a digital signal, conversion to a baseband signal, and Nyquist processing are performed in this order. (Conversion into a baseband signal may be performed before the A / D converter.) The signal C1 output from the high-frequency demodulator 4 and the signal C2 output from the high-frequency demodulator 5 are both transmitted to the rake receiver 6. Is entered. The rake receiver 6 extracts a desired signal component from the input signal, and adds it in synchronization. The rake receiver 6 includes a plurality of finger circuits, and each finger circuit includes a timing tracking loop, a data demodulation circuit, a frequency tracking circuit, and the like. (The configuration and operation of the rake receiver are also introduced in the technical paper (page 169) of Nikkei Electronics 1993. 4.26.) Next, the high frequency demodulator 4 and the CDMA receiver 10 of the present invention are used.
The operation in the case where a failure occurs in any one of the radio receivers 5 and the signal from the failed high-frequency demodulator is no longer input to the rake receiver 6 will be described.

Here, a case where a failure occurs on the high frequency demodulator 4 side will be described. As described above, the output terminal 3 is controlled by the high-frequency signal synthesizer / distributor 3.
04 has a signal A1 of antenna 1 and a signal A2 of antenna 2
Are divided into two and output (signal B2). Therefore,
The signal C2 that has undergone necessary processing by the high-frequency demodulator 5 in which no failure has occurred is input to the rake receiver 6. In a conventional configuration having no high-frequency signal synthesizing / distributing device (FIG. 5), the multipath signal input from the antenna 1 cannot reach the rake receiver 6, so that the signal power of FIG.
Although the combination of keys (a) and (c) is performed, the combination of the signals (a), (b), and (c) in FIG. 2 cannot be performed. According to the CDMA receiver 10 of the present embodiment, the multipath signal input from the antenna 1 can also reach the rake receiver 6, so that the rake receiver 6 has all the signals shown in FIG. Can be synthesized.

In the synthesis of the signal A to the signal G, the effective signals are the signal F, the signal A, and the signal G in the order of higher level. In this example, the effective signals are synthesized without missing. This is the same even when the high-frequency demodulator 5 side fails, not the high-frequency demodulator 4 side.

A decrease in signal level (3 dB) caused by using a hybrid ring as the high-frequency signal synthesizer / distributor 3 directly leads to an increase in the noise figure. It is improved by inserting a low noise amplifier between input terminals.

The output terminal 30 of the hybrid ring
The phase difference (90 ° in this example) between the output signal of the output terminal 3 and the output signal of the output terminal 304 is with respect to the antenna input signal,
Since it does not affect the chip rate of the CDMA signal, there is no particular problem.

[0017]

As described above, the diversity receiver (CDMA) of the spread spectrum communication system according to the present invention.
Receiver) does not lose the input of one of the diversity antennas even if a failure occurs in one of the high-frequency demodulators. Therefore, the CDMA receiver is characterized by the improvement of communication quality by combining multipath signals in a rake receiver. As a result, deterioration of the communication quality can be prevented, and the reliability of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a CDMA receiver according to the present invention.

FIG. 2 is a diagram illustrating an example of a multipath signal delay input from one antenna of FIG. 1;

FIG. 3 is a diagram illustrating an example of a multipath signal delay input from the other antenna of FIG. 1;

FIG. 4 is a diagram illustrating a delay of a multipath signal appearing at an output terminal of the high frequency signal synthesizer / distributor of FIG. 1;

FIG. 5 is a block diagram illustrating an example of a conventional CDMA receiver.

[Explanation of symbols]

 1, 2 Antenna 3 High frequency signal synthesizer / distributor 4, 5 High frequency demodulator 6 Rake receiver

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04J 13/00 H04B 7/08

Claims (1)

(57) [Claims] 1. An uncorrelated signal transmitted from the same source.
The second receiving each of the high-frequency signals including multipath components
A first antenna and a second antenna, receiving in each of said first antenna and said second antenna
Perform a combination of the signals the two high-frequency signals, and the RF-combining-distributor for 2 distributes the combined signal, amplifies the RF-combining-distributor first signal output from the output terminal of the frequency converter , Bandwidth limitation, Base van
To analog signal and analog / digital signal conversion
A first high-frequency demodulator for performing processing, amplification, frequency conversion, band limitation, and baseband of a signal output from a second output terminal of the high-frequency signal synthesizer / distributor.
To analog signal and analog / digital signal conversion
A second high-frequency demodulator for performing processing, and a plurality of finger circuits.
And a failure occurrence state of the second high-frequency demodulator.
An output signal of the first high-frequency demodulator and the second high-frequency demodulator;
Either or both demodulator output signals are
And multipath components of the desired signal from the input signal
A diversity receiver for a spread spectrum communication system, comprising: a rake receiver that performs addition, synchronization, and addition and synthesis .