JPS5870649A - Diversity reception system - Google Patents

Abstract

PURPOSE:To obtain antenna outputs with less number of antennas having same effect as the provision of a lot of antennas with different directivity, by connecting a plurality of phase shifters synthesizing outputs of a plurality of antennas each having a different phase between a plurality of antennas and antenna switching devices to make each phase difference different. CONSTITUTION:Phase shifters 3-5 are provided between antennas 1, 2 and an antenna switching device 6. The phase shifters 3-5 are constituted with cables of different length; l for terminals (b), (c) and (d) at the antenna 2, and l+lambda/2, l+lambda/4 at the antenna 1, respectively. A drive circuit 15 drives the antenna switching device 6 based on the output of an electric field level detector 11 and a multi-path distortion detector 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diversity reception system, and is intended to obtain antenna outputs having a wide variety of directivity from a small number of antennas.

Usually, a car radio equipped with a diversity reception system has two fixed antennas such as a ball antenna, pillar antenna, or windshield antenna, and the reception circuit is switched appropriately to the antenna with the stronger electric field strength among these two antennas. It was structured like this.

However, since the antenna is fixed, the directivity of the antenna cannot be changed in response to the movement of the vehicle, making it difficult to maintain good reception conditions.

In addition, if a large number of antennas with different directivity are installed, even if the car moves, it is possible to always receive good reception by switching the antennas, but in a limited space like a car, many antennas can be used. It is practically difficult from an aesthetic point of view.

The present invention eliminates such drawbacks, and provides a diversity receiving system in which antenna outputs with a wide variety of directivity can be obtained using a small number of antennas, similar to when a large number of antennas with different directivity are provided. This is what I am trying to do.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a receiver equipped with a diversity reception system which is an embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of a main part showing a specific example of the system.

In the figure, 1 and 2 are antennas installed at different positions,
3, 4.5 are phase shifters for combining the outputs of the antennas 1 and 2 with a phase difference and supplying the combined output to the antenna switching device 6.

The phase shifters 3, 4.5 each have λ as shown in FIG.
λ consists of a cable of length 2β 1 + 221 + 7.2μ, where λ is the length of the position and λ is the wavelength of the signal to be received.

Antenna switcher 60 three input terminals b, c, d
id is connected to 20 points in length from the antenna 2 side of the phase shifters 3, 4, and 5, respectively.

λ In other words, the sum of the output of antenna 1 passing through a cable of length n + 2 by three phase shifters and the output of antenna 2 passing through a cable of length 2 is sent to antenna switching device 6. The output of antenna 1 lags behind the output of λ antenna 2 by the relative beam length i, resulting in a phase difference of 18o0. Similarly, for the phase shifter 4.5, both antenna outputs have a phase difference of 900°, are added together, and sent to the antenna switching device 6. 7 is a front end section, 8 is an intermediate frequency amplification/detection section, 9
10 is a low frequency amplifier, 10 is a speaker, 11 is an electric field level detector, 12 is a multipath distortion detector, 13.14 is an amplifier, 15 is an antenna based on the outputs of the electric field level detector 11 and the multipath distortion detector 12. This is a drive circuit that drives the switch 6.

Next, the operation of this diversity receiving system will be explained.

Now the directional gain of the two antennas 1 and 2 is A (θ) = α
sinθ・・・・・・・・・・・・・・・(1)A
2(θ)=βCO8θ・・・・・・・・・・・・・・・
...(2), then in the conventional model A1(θ) and A2
(The size of the antenna was automatically compared with that of the larger one, and the antenna was switched to the larger one. However, in this embodiment, from each phase shifter 3, 4, 5 connected between the feeding points of antennas 1 and 2, B1 (=
a sin θ−βCogθ −−−−6−(
3) B2(=(zsin θ + jβCO8θ
−−−−−・(4) B3(θ)=(zsinθ+βc
osθ -------(5) is obtained, and these outputs are sent to the input terminals S, C, and D of the antenna switching device 6 via each transmission line, and the driving circuit 15 drives the antenna switching device 6. , select these outputs. The output of the antenna switching device is sent to the speaker 1o via the front end section 7, the intermediate frequency amplification/detection section 8, and the low frequency amplification section 9. As in the case where three antennas with different characteristics are provided, three types of antenna outputs can be obtained, and the one with the highest output level among these three outputs can be automatically switched and obtained.

In addition, in the FM radio receiver, the electric field level detector 1
1 and as a detection signal to the multipath distortion detector 12,
It is also possible to use a 19 KHz pilot signal included in the intermediate frequency signal or the detection output signal that has not passed through the limiter circuit.

Furthermore, when using the diversity receiving system of this embodiment in an FM receiver, the length λ of the cable of each phase shifter, especially the length of the portion corresponding to i and ^, is changed in accordance with changes in the reception frequency. Since it is difficult to do so, it is preferable to set the wavelength of the approximately central frequency of the FM broadcast reception frequency band to λ. In this case, since the frequency and bandwidth of FM broadcasting are about 10 degrees lower than the reception frequency of FM broadcasting, there is no problem even if a broadcasting station near the upper and lower limits of the frequency band is received.

In the above embodiment, the phase difference between the outputs of both antennas generated by the three phase shifters 3°4.5 is +1800. +
Although the examples shown are 9oo and oo, the example is not limited to this, and by connecting more phase shifters between two antennas to vary the phase difference, it is possible to create many antennas with different directivity. You can get the output.

As described above, according to the present invention, antenna outputs having many types of directivity can be obtained with a small number of antennas, and these antenna outputs can be selectively extracted. Therefore, the diversity receiving system of the present invention has the number of antennas 1 like a car radio.
This is particularly effective when there are restrictions on

[Brief explanation of drawings]

FIG. 1 is a block diagram of a D/C reception system according to an embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of the main part of the DIP reception system. 1.2...Antenna, 3,4.5...Phase shifter, 6...Antenna switcher, 7...
Front end section, 8...Intermediate frequency amplification/detection section, 9...Low frequency amplification section, 10...
Speaker, 11...Exposure...Electric field level detector, 12...
...Multipath distortion detector, 13.14...
- Amplifier, 15... Drive circuit. Agent Yoshihiro Morimoto'J 4 Open nU 58-70649 (3) No. 1 Figure 30

Claims (1)

[Claims] (D. A plurality of phase shifters are connected between a plurality of antennas installed at different positions for combining the outputs of the plurality of antennas with a phase difference and supplying the synthesized signal to an antenna switching device, A diversity receiving system in which the phase differences are different from each other. (2) The diversity receiving system according to claim 1, wherein the phase shifter is constituted by cables of different lengths.