JPS6086936A - Simple space diversity system - Google Patents

Abstract

PURPOSE:To always control a phase difference within 90 deg. and to attain integration of a phase shifter by changing the phase of the 2nd reception wave by a fixed amount when the phase difference exceeds 90 deg. between the 1st and 2nd reception waves received by the 1st and 2nd receivers. CONSTITUTION:A simple space diversity system contains the 1st and 2nd receivers 1 and 2, a 180 deg.-hybrid circuit 30, switch circuits 31 and 32, a synthesizing circuit 5, a comparator 39, etc. The 1st reception wave received by the receiver 1 is applied to the circuit 5; while the 2nd reception wave received by the receiver 2 is supplied to the circuit 30. The phase difference between the 1st and 2nd reception waves is obtained through processes of a rectifying circuit 40, a differential amplifier 33, an absolute value circuit 34, a variable gain amplifier 35, an addition amplifier 36 and the comparator 39. When the phase shift exceeds 90 deg., the circuits 31 and 32 are controlled by the output of a level shift circuit 38. Then the phase of the 2nd reception wave is changed by a fixed amount to always keep the phase difference within 90 deg. to be synthesized by the circuit 5.

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a simplified space diversity method,
In particular, the present invention relates to a simplified space diversity method used in radio systems that utilize frequency modulated waves and small-capacity digital radio systems.

(bl Prior Art and Problems In a microwave band multiplex radio system, transmission characteristics may change due to relay links and communication quality may deteriorate. Therefore, a space diversity method is used to compensate for fluctuations in transmission characteristics due to fading. has been put into practical use.

1 to 3 show block connection diagrams for implementing the conventional space diversity method.

First, FIG. 1 is a diagram for explaining the space diversity method.

In the figure, the combining circuit 5 receives the first signal received by the receiver 1.
, and a second received wave that is received by the receiver 2 and then passed through the infinite phase shifter 3 and given a phase rotation. Then, the synthesized wave synthesized by the synthesis circuit 5 is outputted from the output terminal 6 to the outside.

On the other hand, the control circuit 4 detects the phase difference between the first receiver and the second received wave after passing through the infinite phase shifter, and controls the infinite phase shifter 3 so that this phase difference becomes 0, for example. Adjust the phase of

FIG. 2 shows a more detailed block diagram of the infinite phase shifter 3 of FIG.

In the figure, the second received wave applied to the input terminal 7 is divided by a hybrid circuit 8, further divided into two by hybrid circuits 9 and 1o, and finally divided into four,
The divided second received waves are sent to amplitude modulators 11 to 1, respectively.
Added to 4.

The amplitude modulators 11 to 14 each have a control terminal 16.
The operation is controlled by a control signal applied to ~19,
The phase of the second received wave can be continuously shifted by 36Q degrees.

For example, by combining mutually orthogonal amplitude modulated wave components obtained by amplitude modulators 11 and 12, a 0 to 90 degree phase shifter can be created, and by combining mutually orthogonal amplitude modulated wave components obtained by amplitude modulators 12 and 13. By combining a 90 to 180 degree phase shifter and a 180 to 360 cell phase shifter obtained by using amplitude modulators 13 and 14 and 11 and 14, a total shift of 0 to 360 degrees is obtained. It is possible to configure a phaser.

Therefore, the second received wave, which has been phase-shifted by a predetermined amount by a phase shifter composed of four amplitude modulators, is amplified to the required level by an amplifier 15, and is then sent from a terminal 2o to the above-mentioned combining circuit 5. It will be done.

FIG. 3 shows a more detailed block connection diagram of the control circuit 4 shown in FIG.

In the figure, the first and second received waves applied to input terminals 2 and 22 are phase-compared by a phase comparator circuit 23,
The output voltage corresponding to the phase difference between the two received waves is extracted,
This output voltage is applied to two variable frequency oscillators 25 and 26 after passing through a low pass filter 24. The variable frequency oscillators 25 and 26 are adjusted so that they oscillate at substantially the same frequency when the output voltage is 0, but the frequencies change in opposite directions depending on the magnitude of the applied output voltage. Outputs a deviated output.

Therefore, each of these outputs is divided into two, and one of them is
By shifting the phase of the two outputs by 90 degrees and then adding the outputs of the separate oscillators to the ring modulator 28, 29 and extracting their beat frequencies, we can obtain four low-frequency signals that are always orthogonal to each other. This signal can be sent to the control terminal 16 in FIG.
, 17, 18, and as explained above, the high performance is comparable to that of conventional space dynamometers, so there are problems in that the circuit configuration is complex and the cost of the device is high.

(C) Purpose of the Invention The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a space-diaperity method that has an easy circuit configuration and is inexpensive.

(d) Structure of the Invention The object of the above invention is to achieve a phase difference of 90 degrees or more between the first received wave received by the first receiver and the second received wave received by the second receiver. A simple space diversity method characterized in that the phase of the second received wave is changed by a certain amount only when the two received waves are controlled so that the phase difference is always within 90 degrees, and the two received waves are combined. 0 (e) Embodiment of the Invention FIG. 4 shows an example of a block diagram for implementing the invention.

In the figure, 1 and 2 indicate the first and second receivers, and 30 indicates 18
0 degree hybrid circuit, 31 and 32 are switch circuits, 5 is a combination circuit, 33 is a differential amplifier, 34 is an absolute value circuit, 35 is a variable gain amplifier, 36 is a summing amplifier, 37 is a flip・Flop circuit, 38 is level・
Shift circuit wo, 39 is a comparison circuit, 40 is a rectifier circuit.
1tvixi-i terminal f〆 and 6 indicate output terminals, respectively.

Note that the same symbols as in FIG. 1 indicate the same parts.

These blocks are connected as follows.

The terminal (1) of the synthesis circuit 5 is connected to the first receiver 1 and the terminal (2
) is connected to the second receiver 2 through the hybrid circuit 30 via switch circuits 31 and 32, and the terminal (3) is connected to the output terminal 6, respectively.

Further, the terminal (3) of the control circuit 39 is connected to the output terminal 6 via the variable gain amplifier 35 and the rectifier circuit 40, and the terminal (2) is connected to the terminal (1) of the synthesizer 5 via the summing amplifier 36 and the rectifier circuit 40. and (2), and terminal (1) are connected to the level shift circuit 38. Flip◆Connected to other terminals of switch circuits 31 and 32 via a flop circuit 37, respectively. Furthermore, another terminal of the variable gain amplifier 35 is connected to the absolute value circuit 34 . The terminals (1) and (2) of the combining circuit 5 are connected via the differential amplifier 33.
) are connected to each other.

The operation of each block connected in this way is as follows.

The received wave of amplitude lll1iA received by the first receiver 1 is directly received, and the received wave of amplitude B received by the second receiver and passed through the 180 degree hybrid circuit 30 and the switch circuit 31 or 32 is is added to the synthesis circuit 5, where 2
The two received waves are combined and a combined wave with an amplitude C is outputted to the output terminal 6.

Here, when the phase difference between the first and second received waves is 90 degrees, the amplitude of the composite wave is as follows.

C,=(A+B)XD However, when A=0 and B=1 or B20 and A=1, D-1
0, when A=B=1, D21641, A〆B.

A>0. When B>o, D takes a value between 1.0 and 1.41, so 10≦D≦141.

A part of the composite wave taken out to the output terminal 6 is rectified by a rectifier circuit 40, and the obtained DC voltage is amplified by a variable gain amplifier 35 and then applied to a comparison circuit 39 as a reference voltage.

On the other hand, the first and second received waves are each rectified by a rectifier circuit 40 and then applied to a differential amplifier 33, where the amplitude A
The absolute value circuit 34 extracts the absolute value of the DC difference voltage corresponding to and B.

This absolute value voltage is used to change the gain of the variable gain amplifier 35 between (10 to 1.41) This voltage corresponds to the amplitude of the composite wave that would be obtained if the angle was 90 degrees. Note that n is the basic gain of the variable gain amplifier 350. Next, the DC component obtained from the two received waves with amplitudes A and B before being combined is sent to the summing amplifier 36.
The signals are summed and amplified to become (A+B)xm, which is added to the comparator circuit 39. Here, m indicates the gain of the summing amplifier 36. The comparison circuit 39 compares the two input voltages and calculates the input voltage V ad d2 (A+B
) xm is the variable gain amplifier 350 input voltage Vag =
= (C/D) When it is larger than xn, it is determined that the phase difference between the two received waves is 90 degrees or more, and the level of 11'' is set. The input signal is applied to the flip-flop circuit 37 via the input signal.

Therefore, the switch circuits 31 and 32 are driven by the two outputs of the flip-flop circuit 370, so for example, the switch circuit 31 is turned on and the other circuit 32 is turned off.
A second received wave phase-shifted is extracted. Therefore, the phase difference between the first and second received waves, which was initially more than 90 degrees, is 9
It will be within 0 degrees.

FIG. 5 is a more detailed circuit example of the 180 degree hybrid circuit 30 and the switch circuits 31 and 32.

In the figure, the 180 degree hybrid circuit 30 utilizes the fact that the phase differs by 180 degrees between the collector and emitter of the transistor 45. The received tear gold is taken out from the collector or emitter,
The received Il@ waves with a phase difference of 180 degrees are obtained.

FIG. 6 is a more detailed circuit example of the portion surrounded by the dashed line in FIG. 4, and the same symbols as in FIG. 4 indicate the same parts.

In the figure, a rectifier circuit 40 rectifies the intermediate frequency signals input thereto to extract DC components corresponding to the respective amplitudes.

The variable gain amplifier 35 controls the gain by varying the bias of the 15 feedback circuit of the operational amplifier i:i+51 used here.

ff) As described in detail, according to the present invention, only when the phase difference between two received waves is 90 degrees v above, the phase 't- of one received wave is
Two switch circuits connected to the 180 degree hybrid circuit are controlled in order to shift the phase by 180 degrees and bring the phase difference within 90 degrees.

As a result, the configuration of the control circuit and phase shifter becomes much simpler than the conventional configuration, and in particular, the phase shifter can be integrated into an integrated circuit. Therefore, the cost of the device is also reduced.

[Brief explanation of the drawing]

Fig. 1 shows an example of a block connection diagram for implementing the conventional space Φ diversity method, Figs. 2 and 3 show more detailed circuit diagrams of Fig. 1, and Fig. 4 shows an example of the circuit diagram of the present invention. An example of a block connection diagram for implementing the space diversity method is shown in FIGS. 5 and 6, and FIGS. 5 and 6 show examples of more detailed circuit diagrams in FIG. 4, respectively. In the figure, 1 and 2 are receivers, 30 is a 180 degree hybrid circuit, 31 and 32 are switch circuits, 5 is a synthesis circuit, 33 is a difference amplifier, 34 is an absolute value circuit, and 35 is a switch circuit. A variable gain amplifier is shown, 36 is a summing amplifier, 39 is a comparison circuit, and 37 is a flip-flop circuit. Agent Patent Attorney Hiroshi Matsuoka 4th Department 1 Inmine 2 Figure ￥ - 3 Ku Haya 4 Kunihoki 5 Eyes α Hand Aim

Claims (1)

[Claims] The phase of the second received wave is changed only when the phase difference between the first received wave received by the first receiver and the second received wave received by the second receiver becomes 90 degrees or more. A simple space diversity method characterized by combining two received waves controlled so that the phase difference is always within 90 degrees by changing a certain amount.