JPH05336081A - Diversity reception equipment - Google Patents

Abstract

PURPOSE:To provide a synthetically satisfactory reception characteristic against the variance of propagation circumstances due to fading or the like. CONSTITUTION:The diversity reception equipment for phase modulation system digital communication having plural reception systems is provided with a synchronous detection circuit 1, a delay detection circuit 2, a branch selecting circuit 3, and a switch 4, and the branch selecting circuit 3 always compares output signals of the synchronous detection circuit 1 and the delay detection circuit 2 with each other to control the switch 4 so that one output signal in the better signal state (higher C/N) is selected. Detection circuits different by systems are used in respective branches of the diversity reception equipment, and outputs of these detection circuits are always compared with one another to select and output the output signal in the best state, thereby providing the synthetically satisfactory reception characteristic against the variance of propagation circumstances due to fading or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver which has a plurality of independent receiving systems, receives a phase-modulated signal, detects it, and switches the output signal to output it.

[0002]

2. Description of the Related Art A conventional diversity receiver will be described. As one of the elements that characterize mobile communication,
The poor propagation environment is raised. The incoming wave from the base station undergoes deep fading due to reflection, refraction, scattering, etc., and its amplitude fluctuates greatly. In the diversity reception system, the received signals are selected and combined elements include space, time,
There are various types such as frequency, directivity, transmission path (PATH), and polarization, and the spatial diversity receiving method is known as one of the methods for overcoming the amplitude fluctuation due to fading. This is done by arranging antennas at multiple points where the correlation coefficient of each received signal quality is extremely small, evaluating each received signal quality, and performing optimal weighting and combining, or It is intended to cope with the deterioration of the propagation environment by selecting the received signal.

On the other hand, the phase demodulation circuits for reproducing the phase modulation signal information are roughly classified into a synchronous detection circuit and a delay detection circuit. The synchronous detection circuit removes the modulation component from the received signal, extracts the reference phase carrier wave, and detects the phase difference between this and the signal. The differential detection circuit detects the phase difference between the signal of the next slot and the signal of the next slot, using the signal of the preceding time slot as the reference phase. It is known that the synchronous detection circuit is theoretically superior when comparing the two. Delay detection has a simple device configuration, but when the number of multilevels is increased, it is inferior to the synchronous detection method in C / N (carrier / noise) by about 3db, so it is not used for public communication. Few.

[0004]

However, in order for the synchronous detection circuit to operate, a PLL (phase locked loo) is required.
It is essential that p) follows the received signal and the coherent carrier is reproduced well. Once the PLL is unlocked due to deterioration of the input signal, that is, the synchronization is lost, the synchronous detection cannot reproduce any information until the synchronization is formed again. Therefore, in actual mobile communications, a burst detection-like long bit error occurs in the synchronous detection circuit due to a momentary deep drop in the received signal level due to fading, etc. It may be inferior. When the synchronous detection circuit is used, an attempt is made to improve the above-mentioned deterioration of dynamic characteristics, but the circuit scale becomes very large. Therefore, even in the post-detection switching diversity receiving system, although theoretically the performance is inferior, a delay detection circuit may be used.

In the conventional post-detection switching diversity receiver, if a synchronous detection circuit is used as the detection circuit, a burst-like long bit error occurs due to a momentary deep drop in the received signal level due to fading or the like, resulting in a bit error. There is a problem in that the rate becomes worse, and when the differential detection circuit is adopted, it is inferior to the synchronous detection circuit in the normal reception signal level state.

The present invention has been made in view of the above points, and eliminates the above problems and provides a diver having a generally good reception characteristic with respect to a propagation environment change due to fading or the like.
It is an object to provide a receiver.

[0007]

In order to solve the above problems, the present invention, as shown in FIG. 1, includes a synchronous detection circuit 1 in a diversity receiver in a phase modulation digital communication having a plurality of receiving systems. The delay detection circuit 2, the branch selection circuit 3, and the switch 4 are provided, and the output signals of the synchronous detection circuit 1 and the delay detection circuit 2 are compared by the constant branch selection circuit 3 and the one with the better signal state (the one with the better C / N ratio) The greatest feature is that a means for controlling the switch 4 is provided so as to select).

[0008]

According to the present invention, in the diversity receiver of the post-detection switching system, the detection circuits of different systems are used for each branch, and the outputs of the respective detection circuits are constantly compared to select and output the output signal in the best state. It is possible to provide comprehensively good reception characteristics with respect to changes in the propagation environment due to fading or the like.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a diversity receiver of the present invention. As shown in the figure, the diversity receiver of the present invention comprises a synchronous detection circuit 1, a differential detection circuit 2, a branch selector 3 and a switch 4. The synchronous detection circuit 1 includes a mixer 1-1, a low-pass filter 1-2, and 90 °.
Phase shifter 1-3, mixer 1-4, low-pass filter 1
-5, a mixer 1-6, and a voltage controlled oscillator 1-7, and the differential detection circuit 2 includes a bandpass filter 2-1, a mixer 2-2, a delay circuit 2-3, and a lowpass filter 2-4. To be done.

FIG. 1 shows an example of a diversity receiver for receiving an input signal which is BPSK modulated (phase modulated). In the coherent detection circuit 1, a coherent carrier is reproduced in the voltage controlled oscillator 1-7 by the Costas loop, and the modulated signal input to the branch 5 is multiplied by the carrier in the mixer 1-1 and the low-pass filter 1-. It is detected through 2

In the delay detection circuit 2, the current modulation signal input to the branch 6 and passed through the bandpass filter 2-1 and the modulation signal delayed by one symbol time in the delay circuit 2-3 are multiplied by the mixer 2-2. Then, it is detected through the low-pass filter 2-4.

The output signals of the synchronous detection circuit 1 and the delay detection circuit 2 are compared in quality by the branch selector 3, and the output signals of both detection circuits at that time are higher in quality (higher in C / N ratio). The signal is selected by the switch 4 and output to the next data processing system.

FIG. 2 is a diagram showing an example of the input signal waveform and the output waveform of each detection circuit. It is the figure which showed the example of the output waveform which inputs the same input signal from the branch 5 and the branch 6 into the synchronous detection circuit 1 and the differential detection circuit 2, and is output from each detection circuit. In the figure, the broken line shows the original form of the input modulation signal. In the state A in the figure, each output of the synchronous detection circuit 1 and the differential detection circuit 2 is as shown by the solid line in the figure. That is, in principle, the signal quality of the synchronous detection circuit 1 is excellent, and the signal quality of both output signals fluctuates due to fading or the like, but statistically the output of the synchronous detection circuit 1 is the branch selector 3. The frequency of being selected and switched by the switch 4 is high.

However, if a sharp and deep drop occurs in the input signal even in an extremely short time as in the state B, the synchronous detection circuit 1 is out of synchronization, and it is random as shown in state C in FIG. Output signal. On the other hand, the delay detection circuit 2
Since the output of always outputs according to the quality of the input signal,
During the state C in the figure, the output of the differential detection circuit 2 is selected by the branch selector 3 and switched by the switch 4 so that correct data is reproduced and output.

In the above example, two detection circuits, that is, the synchronous detection circuit 1 and the delay detection circuit 2 have been described as an example. It is possible to provide excellent reception characteristics.

[0016]

As described in detail above, according to the present invention, the following effects are expected. Each branch of the diversity receiver is equipped with a detection circuit with a different method of a synchronous detection circuit and a differential detection circuit, and each output signal is constantly compared by the branch selector, and the better signal is switched and output by the switch. Due to this, even when the input signal has a sharp and deep drop and the synchronous detection circuit loses synchronization and causes a long burst-like bit error, it is automatically switched to the output signal of the delay detection circuit and the received signal quality is improved. You can secure it. Therefore, while the circuit scale is equivalent to that of the conventional post-detection switching diversity receiver, a better received signal quality can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an example of a diversity receiver of the present invention.

FIG. 2 is a diagram showing an example of an input signal waveform and an output waveform of each detection circuit.

[Explanation of symbols]

 1 Synchronous detection circuit 1-1 Mixer 1-2 Low-pass filter 1-3 90 ° phase shifter 1-4 Mixer 1-5 Low-pass filter 1-6 Mixer 1-7 Voltage controlled oscillator 2 Delay detection circuit 2-1 Band pass filter 2-2 mixer 2-3 mixer 2-4 low-pass filter 3 branch selector 4 switch

Claims (1)

[Claims] 1. A diversity receiver having a plurality of independent receiving systems, comprising means for receiving, detecting and reproducing a phase-modulated signal, wherein the plurality of independent receiving systems receive the received signals. Each receiving branch is provided with a detecting means of a different system, and a selecting means for comparing the output signal levels of each branch and selecting the signal in the best state and a switching means for switching and outputting the output signal are provided. A diversity receiver, which receives a reception signal, compares the output signal levels of the respective detection means, selects the output signal in the best state by the selection means, and outputs the output signal from the switching means.