JP2705325B2 - Diversity receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for receiving signals transmitted from the same terminal with antennas of a plurality of base stations and performing diversity combining in a fading propagation environment such as a mobile telephone system.

[0002]

2. Description of the Related Art In mobile communication, in order to reduce the probability of deterioration in communication quality, a transmission signal of the same mobile terminal is received by a plurality of base stations at different locations as shown in FIG. There is. Conventionally, when diversity combining is performed with signals on a radio frequency unchanged, the phase is detected by a phase shifter as shown in FIG. 3 so that the signals are not added together in opposite phases and cancel each other. Was controlled to be in phase and then synthesized. This diversity combining reception method is described on pages 164 to 165 of the book "Basics of Mobile Communication" published by the Institute of Electronics, Communication and Communication in 1986.

[0003]

However, in a propagation environment in which wireless communication such as an automobile telephone is used, it is difficult to control a phase shifter due to a drastic phase change due to fading, and it is difficult to control a signal on a radio frequency. If the diversity combining is performed as it is, there is a problem that the mutual signals are added in opposite phases to cancel each other and the communication quality is deteriorated.

[0004]

Diversity receiver of the present invention SUMMARY OF THE INVENTION includes means for splitting the signal antenna of a plurality of systems has received a plurality of branch signals, different the A
The branch signals of the antennas are collected to form a branch signal group,
It said means for providing a phase rotation to each of the branch signals of the serial branch signal group, a branched signals respectively given the phase rotation plurality
Means for obtaining a plurality of synthesized signals by synthesizing each of the branch signal groups, means for comparing the envelopes of the plurality of synthesized signals, and means for selecting and outputting the synthesized signal having the maximum envelope level And characterized in that:

[0005]

When signals on a plurality of radio frequencies are combined, the mutual signals cancel each other out when the phase relationship between the signals becomes opposite. At this time, if a phase rotation is given in advance so that the signals have the same phase, they do not cancel each other when they are added. However, in an environment where severe fading exists, it is difficult to know in advance how much phase rotation should be given to combine signals in phase. Therefore, in the present invention, the signals of the respective antenna systems are branched into a plurality of signals, and when the signals of the different antenna systems are combined, the phase difference between the signals is different for each combiner, so that each signal group is divided. A phase rotation is given to each signal. By doing in this way, a composite signal added almost in phase and a composite signal added almost in phase can always be obtained, so the envelopes of the composite signals are compared, and if the composite signal having the largest envelope is selected. , A signal synthesized almost in phase can be obtained.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 shows an embodiment of the diversity receiving apparatus according to the present invention. Note that, for simplicity of explanation, the exchange 4
Inside 0, the phase rotation of a signal generated in a transmission path other than the phase shifter is negligible.

A signal transmitted from a certain mobile terminal is received by base station 1 (10a) and base station 2 (10b). The received signals are converted into optical signals by the electric / optical converters (12a, 12b) and sent to the exchange (40) through the optical transmission lines (50a, 50b). In the exchange, an optical signal group composed of two systems is converted into an electric signal by an optical / electrical converter (30a, 30b). The two signals thus converted into electric signals are each split into two by the splitters (31a, 31b) to become four split signals. Here, a group of branch signals of different antenna systems is referred to as a branch signal group. That is, two branch signals that are input signals of the phase shifters 32a and 32b are one branch signal group, and two branch signals that are input signals of the phase shifters 32c and 32d are another branch signal group. Each of the branch signals of each of the branch signal groups is converted into a phase shifter 32a (phase shift rotation θ11), a phase shifter 32b (phase shift rotation θ12), a phase shifter 32c (phase shift rotation θ21), and a phase shifter 32d (phase shifter 32d). Phase rotation θ
22) provides a phase rotation. At this time, the initial phase difference in the two branch signal groups before the phase shifter input is the same, but this is θ0, and the phase shift amounts of the phase shifters are, for example, θ11, θ12, θ21 are 0 radians, and θ22 is If it is set to π radians, the phase shifters 32a, 32
The phase difference at the output of b is θ0, and the phase difference at the phase shifters 32c and 32d is θ0−π. Therefore, even if the initial phase difference θ0 in the branch signal group is close to the same phase and near 0 or close to the opposite phase and near π, either of the phase differences of the input signals of the two combiners (33a, 33b) is 0. And near the same phase.

[0009] The two branch signal groups thus given a phase rotation are combined by the combining circuits 33a and 33b together with the branch signals of the same branch signal group to form a combined signal. Then, the envelopes of these combined signals are compared by an envelope comparator 34, and the result is sent to a selection combiner 35, where the signal combined with the maximum envelope, that is, the phase difference closest to the in-phase, is selected and received. Machine 36.

In this embodiment, the number of antenna systems and the number of branch signal groups are both 2. However, the numbers of both need not be the same, and can be similarly realized by an arbitrary number of 2 or more. Further, the transmission path is not limited to the optical transmission path.

[0011]

According to the present invention described in detail above, even in a propagation environment in which severe fading exists, diversity combining can be realized with a radio frequency signal without detecting and controlling a phase. In addition, a good diversity effect can always be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a diversity receiving apparatus according to the present invention.

FIG. 2 is a diagram illustrating a state where a signal of a mobile terminal is received by a plurality of base stations and diversity combining is performed.

FIG. 3 is a configuration diagram of a conventional diversity receiving apparatus.

[Explanation of symbols]

 Reference Signs List 10a base station 10b base station 11a antenna 11b antenna 12a electric-optical converter 12b electric-optical converter 30a optical-electric converter 30b optical-electric converter 31a duplexer 31b duplexer 32a phase shifter 32b phase shifter 32c phase shifter 32d phase shifter 33 combining circuit 34 envelope comparator 35 selection combining circuit 36 receiver 40 switching center 50a optical transmission path 50b optical transmission path 210 base station 220 base station 230 mobile terminal 240 switching center 310a antenna 310b antenna 320a phase detector 320b phase detector 330a phase shifter 330b phase shifter 340 synthesis circuit 350 receiver

Claims (1)

(57) [Claims] 1. A means for branching to a plurality of branch signals plurality of systems of antennas the received signals, respectively, different the
The branch signals of the antennas are collected to form a branch signal group,
Said means for providing a phase rotation to each of the branch signals of the branch signal group, a branched signals respectively given the phase rotation double
Means for obtaining a plurality of synthesized signals by synthesizing each of the plurality of branch signal groups, means for comparing the envelopes of the plurality of synthesized signals, and selecting and outputting the synthesized signal having the maximum envelope level And a diversity receiving device.