JPH04265025A - Receiver for two-station simultaneous transmission diversity wave - Google Patents

Abstract

PURPOSE:To demodulate the FM demodulating signal of an AM detecting system with high accuracy even in the case an amplitude ratio of receiving waves from two transmitting stations is near '1' and also, to prevent the malfunction of a changeover switch, at the time of receiving those receiving waves by the AM detecting system and an FM detecting system. CONSTITUTION:In a receiver, an amplitude ratio of amplitude a(t) and b(t) of receiving waves from two transmitting stations is detected by using an output signal S2(t) of an AM detecting circuit 2, and when an FM demodulating signal S14(t) of the AM detecting system is a final PM demodulating signal, it is suspended to allow a code of the signal S14(t) of the AM detecting system to coincide with a code of an FM demodulating signal S12(t) of an FM detecting system. In such a way, the FM demodulating signal S14(t) of the AM detecting system can be obtained with high accuracy from an output signal of the AM detector without using information of an output signal of the FM system, and also, a malfunction of a changeover switch can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, in the field of wireless communications, relates to a receiver for simultaneous transmission diversity waves that transmits the same information from two transmitting stations at approximately the same radio frequency with a mutual phase shift. .

0002

2. Description of the Related Art In a two-station simultaneous transmission diversity system and its device, the receiver obtains substantially the same FM demodulated signal using different methods from the output signal of an FM detection circuit and the output signal of an AM detection circuit. The FM demodulated signal obtained from the output signal of the FM detection circuit (hereinafter referred to as FM detection system FM
F obtained from the demodulated signal) and the output signal of the AM detection circuit
A final FM demodulated signal is obtained by selecting a signal with a good signal-to-noise power ratio from among the M demodulated signals (hereinafter referred to as FM demodulated signals of AM detection system).

FIG. 7 shows a block circuit diagram of a conventional receiver. The signal S20(t) received by the antenna 20 is given by the following equation [Equation 1].

[Equation 1] However, φ(t) is the transmission signal, a(t), b(t), and u1 (t), u2 (t) are the amplitude and phase of the received waves from the two transmitting stations, f1 , f2 and m1, m
2, is the frequency and modulation index of the tone signal added at the transmitting station, and ω1, ω2 are the angular frequencies of the carrier waves transmitted from each of the two transmitting stations.

[0004] Also, a(t), b(t), u1 (t)
, u2 (t) vary over time due to fading. The output signal S1 (t) of the FM detection circuit 1 is expressed by the following formula [Equation 2]
is given by

[Formula 2] However, Δω=ω2 −ω1 , u(t)=u2 (t
)−u1 (t).

The output signal S2 (t) of the AM detection circuit 2 is given by the following equation.

A method for obtaining an FM demodulated signal from the output signal S1 (t) of the FM detection circuit 1 will be explained. S1 (t) and S2 (t) are applied to the multiplier circuit 9, and S1 (t
) and S2 (t), and a signal S9 (t) is output. S9 (t) is shown in the following equation [Math. 3].

[Math 3]

The output signal S9 (t) of the multiplier circuit 9 is applied to the amplitude ratio detection circuit 21 whose configuration is shown in FIG. The amplitude ratio detection circuit 21 first separates the two different tone signals added at the transmitting station side, and then detects the amplitudes of the two different tone signals in the peak hold circuits 22 and 23, respectively. When the modulation indices of the two tone signals are equal, the output signal S2 of the peak hold circuits 22 and 23
1(t) and S22(t) are shown in the following equations. S21(t)=a2(t)
……………(7
) S22(t)=b2(t)
……………(
8)

Next, S21(t) and S22(t)
is used to obtain a comparator output signal S23(t) and an amplitude ratio output signal S24(t) shown in the following equations.

An interference noise removal circuit 24 whose configuration is shown in FIG.
, the output signal S9 (t) of the multiplier circuit 9, the comparator output signal S23 (t), and the amplitude ratio output signal S24 (t).
) is applied.

In the interference noise removal circuit 24, first, the BPF
At step 25, only the FM demodulated signal is extracted. Next, S23(t)
and S24(t), the sign and amplitude are a(t) and b(t
) to obtain an FM demodulated signal S12(t) that does not depend on the value of The FM demodulated signal S12(t) is expressed by the following equation. S12(t)=φ(t)/2π
……………(11)

[
Next, the output signal S2 (t
) to obtain an FM demodulated signal will be explained. The AM detection FM demodulation circuit 26, the configuration example of which is shown in FIG.
23(t), the amplitude ratio output signal S24(t), and the output signal S25(t) of the switching signal generator 27 are applied.

In the AM detection FM demodulation circuit 26, first, the S
24(t) to obtain a signal S26(t) that does not depend on the values of a(t) and b(t). S26(t) is shown in the following equation. S26(t)=cosθ(t)
(12) Next, S26(t) is converted into a signal S13(t) shown in the following equation. Furthermore, only the FM demodulated signal is detected from S13(t), and an FM demodulated signal S14(t) of the AM detection system is obtained, which is matched in amplitude with the FM demodulated signal S12(t) of the FM detection system. S14(t) is shown in the following equation. S14(t)=φ(t)/2π
……………(14) or S14(t)=-φ(t)/2π
……………(15) Finally, S14(t) is expressed by equation (14) and (15) due to the nature of the detection method.
) equation cannot be distinguished, so the FM demodulated signal S1 of the FM detection system
2(t) and the output signal S2 of the switching signal generator 27
5(t) to obtain an AM detection system FM demodulated signal S15(t) whose sign matches S12(t).

The changeover switch 28 applies both the FM demodulated signal S12(t) of the FM detection system and the FM demodulated signal S15(t) of the AM detection system, and outputs the output signal S25(t) of the switching signal generator 27. As a switching signal, a signal with a good signal-to-noise power ratio is output as a final FM demodulated signal.

[0014] In the switching signal generator 27,
The output signal S24(t) of the amplitude ratio detection circuit is applied, and (
At time t that satisfies equation (16), the FM demodulated signal S15(t) of the AM detection system is output, and at time t that satisfies equation (17), the FM demodulated signal S12(t) of the FM detection system is output. Outputs switching signals. S24(t)>m
…………
...(16) S24(t)≦m

(17) where m is the threshold value of the comparator in the switching signal generator 27 (0<m<1).

[0015]

When the amplitude ratio of a(t) and b(t) is close to 1, an extremely large frequency shift occurs due to two-wave interference. In such a case, the FM detection circuit 2 generally does not operate normally, and as a result, the output signal S9 (t) of the multiplier circuit 9 is no longer output as shown in equation (6). Therefore, in the amplitude ratio detection circuit 21, a2
(t), b2 (t) values are no longer detected accurately, and the comparator output signal S23(t) and amplitude ratio output signal S24(t) are no longer output as shown in equations (9) and (10). .

When the amplitude ratio of a(t) and b(t) is close to 1, the FM demodulated signal S15(t) of the AM detection system is used as the final FM demodulated signal, but the output signal of the AM detection circuit 2 In the step of obtaining an FM demodulated signal from S2 (t), S
23(t) and S24(t), there was a problem that the FM demodulated signal S15(t) of the AM detection system was not demodulated with high precision.

Furthermore, as mentioned earlier, the F of the AM detection system
Since equations (14) and (15) cannot be distinguished from the M demodulated signal S14(t), the FM demodulated signal S of the FM detection system
12(t) to AM detection system FM demodulated signal S14(t)
When switching to FM, it is necessary to match the signs of the FM demodulated signals. However, in conventional receivers, this code matching was always performed, so a(t) and b(t)
When the amplitude ratio of is close to 1, the FM demodulated signal S of the AM detection system
There was a problem that the sign of 15(t) was wrong.

Further, when the amplitude ratio of a(t) and b(t) is close to 1, the amplitude ratio output signal S24(t) is not output accurately, so that the output signal S2 of the switching signal generator 27
There also existed a problem that 5(t) was not output accurately and the changeover switch 28 malfunctioned.

[0019] An object of the present invention is that when receiving waves from two transmitting stations are received by an AM detection system and an FM detection system, even if the amplitude ratio of these received waves is close to 1, the F of the AM detection system is
It is an object of the present invention to provide a receiver in which an M demodulated signal is demodulated with high precision and there is almost no malfunction of a changeover switch for selecting one of the outputs of both detection systems.

[0020]

[Means for Solving the Problems] A two-station simultaneous transmission diversity wave receiver according to the present invention receives angle-modulated radio frequency signals from two transmitting stations using the same transmission signals that differ only in sign, using substantially the same carrier frequency. In order to receive the transmission diversity wave to be sent out, an FM detection circuit that receives the IF signal obtained by receiving the transmission diversity wave and detects its frequency fluctuation, and a signal that receives the IF signal and is proportional to the square of its envelope. an AM detection circuit that detects the FM detection circuit; a multiplication circuit that receives both the FM detection circuit and the output signals of the AM detection circuit and outputs an FM demodulated signal containing almost no interference noise; and reception from each of the two transmitting stations. an amplitude detection circuit that detects the magnitude of the amplitude of the wave; an interference noise removal circuit that makes the amplitude and sign of the output signal of the multiplication circuit constant regardless of the amplitude ratio of the received wave; and an output of the AM detection circuit. a constant amplitude circuit that receives a signal and outputs a signal proportional to the square of an envelope having a signal power independent of the amplitude ratio of the received wave; and a constant amplitude circuit that receives an output signal of the constant amplitude circuit and outputs an FM demodulated signal. A signal with a better signal-to-noise power ratio is selected from among the output signals of the AM detection FM demodulation circuit, the interference noise removal circuit, and the output signal of the AM detection FM demodulation circuit, and is output as a final FM demodulation signal. It has a configuration including a changeover switch.

[0021]

[Operation] In the two-station simultaneous transmission diversity wave receiver of the present invention, a(t) and b
When the amplitude ratio of (t) is detected and the FM demodulated signal of the AM detection system is used as the final FM demodulated signal, the sign of the FM demodulated signal of the AM detection system is made to match the sign of the FM demodulated signal of the FM detection system. Try to stop something. Thereby, the FM demodulated signal of the AM detection system can be obtained with high accuracy from the output signal of the AM detector without using the information of the output signal of the FM detection system, and malfunction of the changeover switch can be prevented.

[0022]

[Example] An example of the present invention will be explained using drawings and mathematical formulas. Also in the receiver according to the embodiment of the present invention shown in FIG. The final FM demodulated signal is obtained by selecting a signal with a good signal-to-noise power ratio from the FM demodulated signal of the FM detection system and the FM demodulated signal of the AM detection system.

In FIG. 1, the constant amplitude circuit 3 includes an AM
The output signal S2 (t) of the detection circuit is applied, and a(t)
A signal S8 (t) that does not depend on the amplitude ratio of and b(t) is output. An example of the configuration of the constant amplitude circuit 3 is shown in FIG.

In the constant amplitude circuit 3, the output signal S3 (t) of the peak hold circuit 4, the output signal S3 (t) of the peak hold circuit 5
output signal S4 (t), output signal S5 of division circuit 6
(t), the output signal S6 (t) of the subtraction circuit 7, the output signal S7 (t) of the subtraction circuit 8, and the output signal S8 (t) of the constant amplitude circuit 3 are shown in the following equation. S3 (t)=1
…………
...(18) S8 (t)=(1+cosθ(t
))/2 ……………(23)

A method for obtaining an FM demodulated signal from the output signal S1 (t) of the FM detection circuit will be explained. In the multiplication circuit 9,
S1 (t) and S2 (t) are applied, and S1 (t)
A signal S9 (t) obtained by multiplying S2 (t) by S2 (t) is output. S9 (t) is shown in the following equation.

S9(t) is branched into two, one of which is applied to the amplitude detection circuit 10 shown in FIG. 3, and the other to the sign and amplitude constant circuit 11 shown in FIG.

In the amplitude detection circuit 10, first, after separating two different tone signals added at the transmitting station side, a
The magnitude of the amplitude of (t) and b(t) is determined. The output signal S10(t) of the amplitude detection circuit 10 is given by the following equation when the modulation indices of the two tone signals are equal.

The constant sign and amplitude circuit 11 receives the output signal S9 (t) of the multiplication circuit 9, the output signal S10 (t) of the amplitude detection circuit 10, and the output signal S6 (t) of the subtraction circuit 7 of the constant amplitude circuit 3. is applied. In the sign and amplitude constant circuit 11, the BPF 12 extracts only the FM demodulated signal from S9 (t), and uses S10 (t) and S6 (t) to adjust the sign and amplitude to the values of a(t) and b(t). An independent signal S11(t) is output.

The output signal S11(t) of the constant sign and amplitude circuit 11 is applied to the delay circuit 13, and the delay time with the FM demodulated signal of the AM detection system is corrected to obtain an FM demodulated signal. The FM demodulated signal S12(t) of the FM detection system is given by the following equation. S12(t)=φ(t)/2
……………(11)

Next, the output signal S2 of the AM detection circuit 2 (
A method for obtaining an FM demodulated signal from t) will be explained. The value of the output signal S2 (t) of the AM detection circuit 2 is a(t) and b(
Since it depends on the amplitude ratio of a(t), in the constant amplitude circuit 3, a(
The signal S8 (t) does not depend on the amplitude ratio of t) and b(t)
After converting into , the signal is applied to the AM detection FM demodulation circuit 14 shown in FIG.

In the AM detection FM demodulation circuit 14 shown in FIG. 5, first, from S8 (t), the signal S13 (t
) is converted to Next, from S13(t), only the FM demodulated signal is detected,
The FM demodulated signal S14(t) of the AM detection system is obtained by matching the amplitude with the FM demodulated signal S12(t) of the FM detection system. S14(t) is shown in the following equation. S14(t)=φ(t)/2π
……………(14) or S14(t)=-φ(t)/2π
……………(15)

0
The switching circuit 15 shown in FIG.
An output signal S4 (t) of is applied.

In the switching circuit 15, the AM detection system FM
Since the demodulated signal S14(t) cannot distinguish between equations (14) and (15) due to the nature of the detection method, the initial conditions are determined from the FM demodulated signal S12(t) of the FM detection system. However, a(
When the amplitude ratio of t) and b(t) is close to 1, S12(t)
Since the signal-to-noise power ratio of S14(t) deteriorates significantly, at time t that satisfies equation (26), the sign of S14(t) is changed to F
Match the sign of the demodulated signal S12(t) of the M detection system, and (
At time t when formula 25) is satisfied, it is decided to stop matching the sign of S14(t) with the sign of demodulated signal S12(t) of the FM detection system. In this way, the demodulated signal S15(t) of the AM detection system whose sign has been determined is obtained. Then, at time t that satisfies equation (25), FM demodulated signal S15(t) of the AM detection system is output, and at time t that satisfies equation (26), FM demodulated signal S12 of the FM detection system.
(t) is output. S4 (t)>n
…………
...(25) S4 (t)≦n

……………(26) n is the comparator threshold (0
<n<1).

[0034]

Effects of the Invention In the present invention, by providing a constant amplitude circuit, AM detection can be performed without using the information of the FM detection system signal.
It becomes possible to accurately demodulate the detection system signal. Furthermore, at time t that satisfies equation (25), the AM Inversion of the sign of the FM demodulated signal S14(t) of the detection system can be prevented. Further, even when the amplitude ratio of a(t) and b(t) is close to 1, malfunction of the switching circuit 15 is prevented because the output signal S4(t) of the peak hold circuit 5 of the constant amplitude circuit 3 is used as the switching signal. be able to. Therefore, there is an advantage that the FM demodulated signal can be demodulated with high accuracy. The present invention has such effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a receiver according to the present invention.

FIG. 2 is a block diagram showing an example of an amplitude constant circuit used in the configuration of FIG. 1;

FIG. 3 is a block diagram showing an example of an amplitude detection circuit used in the configuration of FIG. 1;

FIG. 4 is a block diagram showing an example of a code and amplitude constant circuit used in the configuration of FIG. 1;

FIG. 5 is a block diagram showing an example of an AM detection FM demodulation circuit used in the configuration of FIG. 1;

FIG. 6 is a block diagram showing an example of a switching circuit used in the configuration of FIG. 1;

FIG. 7 is a block diagram showing an example of the basic configuration of a conventional receiver.

8 is a block diagram showing an example of an amplitude ratio detection circuit used in the configuration example of FIG. 7. FIG.

9 is a block diagram showing an example of an interference noise removal circuit used in the configuration example of FIG. 7. FIG.

[Figure 10] AM detection FM used in the configuration example in Figure 7
FIG. 2 is a block diagram showing an example of a demodulation circuit.

[Explanation of symbols]

1 FM detection circuit 2 AM detection circuit 3 Constant amplitude circuit 4, 5, 22, 23 Peak hold circuit 6 Multiplication circuit 7, 8 Subtraction circuit 9 Multiplication circuit 10 Amplitude detection circuit 11 Sign and constant amplitude circuit 12, 25 BPF 13 Delay circuit 14, 26 AM detection FM demodulation circuit 15 Switching circuit 21 Amplitude ratio detection circuit 24 Interference noise removal circuit 27 Switching signal generator 28 Changeover switch

Claims (1)

[Claims] Claim 1: In order to receive a transmission diversity wave in which two transmitting stations transmit angle-modulated radio frequency signals using the same transmission signal that differs only in sign at substantially the same carrier frequency, the transmission diversity wave is received. an FM detection circuit that receives the IF signal obtained by the IF signal and detects its frequency fluctuation; an AM detection circuit that receives the IF signal and detects a signal proportional to the square of its envelope;
a multiplier circuit that receives both of the output signals of the detection circuit and outputs an FM demodulated signal containing almost no interference noise; an amplitude detection circuit that detects the magnitude of the amplitude of the received waves from each of the two transmitting stations; and the receiver. an interference noise removal circuit that makes the amplitude and sign of the output signal of the multiplication circuit constant without depending on the amplitude ratio of the received waves; and a signal power that receives the output signal of the AM detection circuit and does not depend on the amplitude ratio of the received waves. an AM detection FM demodulation circuit that receives an output signal of the constant amplitude circuit and outputs an FM demodulated signal, and an output of the noise interference removal circuit. A signal with a better signal-to-noise power ratio is selected from among the signals and the output signal of the AM detection FM demodulation circuit, and the final F.
A two-station simultaneous transmission diversity wave receiver equipped with a changeover switch that outputs an M demodulated signal.