JP2654546B2 - Alarm detection method for 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 an alarm detection system for a diversity receiver, and more particularly to an alarm detection system for a diversity receiver capable of detecting a failure in a receiver.

[0002]

2. Description of the Related Art One of such alarm detection systems in a conventional diversity receiver is disclosed in JP-A-63-227.
No. 129 (Title of Invention: SD alarm system). The alarm detection method according to this publication relates to a technique for determining whether a reception failure of space diversity is due to fading or a receiver failure. This alarm detection method detects the signal level after combining the two received signals before and after combining them in reverse phase, in addition to the diversity receiver circuit that performs phase compensation on the two received signals and combines the phases. The level after the combination is used to determine whether the reception failure is due to fading or a receiver failure.

[0003]

The disclosed alarm detection method for a diversity receiver uses a 180 ° phase shift for detecting an alarm in addition to a phase compensation circuit and a signal synthesis circuit having substantially the same configuration used in a diversity reception circuit. The disadvantage is that the configuration is complicated because of the necessity of an additional vessel.

[0004]

SUMMARY OF THE INVENTION An alarm detection system for a diversity receiver according to the present invention includes a first receiver for receiving and processing a first received signal to generate a second received signal; A second receiver for receiving and processing a third received signal coherent to a signal to generate a fourth received signal, and combining the second received signal and the fourth received signal. A combiner that generates a synthesized signal; a phase comparator that compares a phase of the second received signal with a phase of the fourth received signal to generate a comparison output; A phase shifter that performs phase compensation so that a phase difference between a received signal and the fourth received signal is minimized, a first level detector that detects a level La of the second received signal, A second level detector for detecting the level Lb of the received signal of
A third level detector for detecting the level Ls of the composite signal, and responding to the detected level La of the second received signal, level Lb of the fourth received signal, and level Ls of the composite signal. An alarm detector for detecting a malfunction of the phase compensation by the phase shifter.

[0005] One of the alarm detection systems of the diversity receiver is that the alarm detector detects the detected levels La, Lb and Ls by the formula Ls <｛(La + Lb).
・ Cos θth) ² + (Lb · sin θth) ² ｝ ^1/2
(However, θth is an allowable phase error for the malfunction judgment of the phase compensation), an alarm signal can be output.

[0006] Another one of the alarm detection methods of the diversity receiver is that the first receiver and the second receiver have substantially the same performance and the same AGC.
It is a receiver that performs AGC operation with a voltage, and may have a configuration in which the phase shifter is inserted between the second receiver and the combiner.

[0007]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In the diversity receiver, the antenna 1a receives a radio signal transmitted from the transmitter via the first propagation path to form a reception signal S1a, and the reception signal S1a is transmitted via the second propagation path. The radio signal is received by the antenna 1b and is set as a reception signal S1a. The radio signal, that is, the reception signal S
1a and S1b are signals of a carrier frequency of 5 GHz band modulated by, for example, 64 QAM (multilevel amplitude modulation),
The first and second propagation paths are subjected to different fadings, respectively, and are subjected to level reduction and waveform distortion. The diversity receiver is a device for performing in-phase synthesis of a signal corresponding to the received signal S1a and a signal corresponding to the received signal S1b to obtain a high-quality received signal in which the above-described level reduction and waveform distortion are reduced. Hereinafter, the reception signal S1a and the components on the side through which the corresponding signal passes and the reference numerals of the signals are denoted by adding a, and the reception signal S1b
In addition, the components on the side through which the corresponding signal passes and the code of the signal are denoted by b.

The reception signal S1a is amplified and frequency-converted by the receiver 2a to become a reception signal S3a which is an intermediate frequency signal of, for example, a 70 MHz band. Similarly, the reception signal S1b is amplified and frequency-converted by the receiver 2b to become a reception signal S2b which is an intermediate frequency signal. This received signal S
2b passes through the phase shifter 3 and becomes a received signal S3b. Here, the receivers 2a and 2b have substantially the same performance and perform AGC operation at the same AGC voltage.
That is, the AG of a receiver having a high received signal level
AGC operation is performed using the C voltage as an AGC control voltage. Since then
A description will be given on the assumption that the level of the reception signal S1a input to the receiver 2a is higher than or the same as the level of the reception signal S1b. In this case, the level of the reception signal S3a is kept at a constant value, and the level of the reception signal S2b is higher than the reception signal S3a (the level of the reception signal S1a minus the level of the reception signal S1b).
Only lower. In this receiver, the level of the received signal S2b is increased by the amount corresponding to the passage loss of the phase shifter 3, and
When the levels of the reception signals S1a and S1b are equal, the levels of the reception signals S3a and S3b are equal. FIG. 1 does not show a circuit relating to AGC.

The received signal S3a is divided by a distributor 4a using a hybrid or the like into a signal S4a for phase comparison and a signal S5a for synthesis.
The received signal S3b is also distributed to the phase comparison signal S4b and the synthesis signal S5b by the same distributor 4a. Here, the level of the reception signal S1a and the synthesis signal S5
It is clear that the level of “a” is proportional to the level of the received signal S1b and the level of the synthesizing signal S5b.

The phase comparison signals S4a and S4b are compared in phase by a phase detector 5, and the phase detector 5 generates a comparison output S5 which is an error output of the phase comparison. Note that the phase comparator 5
For example, a ring-type phase detector as shown in FIG. 3.42 in Document 1 (Digital Microwave Communication, Planning Center, May 1984) can be used.
The phase detector 5 supplies the comparison output S5 to the phase shifter 3, and changes the phase shift amount of the phase shifter 3 so that the phase difference between the phase comparison signals S4a and S4b is minimized. In the phase shifter 3,
For example, a vector combining phase shifter using a diode as shown in FIG.

On the other hand, each of the synthesizing signals S5a and S5b is supplied to a different signal input arm of the synthesizer 6 capable of using a 90 ° hybrid or a 180 ° hybrid, and the synthesized signal S6 is supplied to the synthesizing arm of the synthesizer 6. Occurs. When the combining signals S5a and S5b are in phase, the combiner 6 generates a combined signal S6 obtained by combining the combining signals S5a and S5b in phase. In a state where the phase difference between the phase comparison signals S4a and S4b is zero or minimum,
As long as there is no failure in the diversity receiver, the combining signals S5a and S5b are almost in-phase combined. The synthesized signal S6 is supplied to a signal output terminal 9, and further supplied to a demodulation circuit (not shown) for demodulating the signal.

The diversity receiver is provided with an alarm detection circuit for detecting an erroneous operation of phase compensation, which is one of the serious failures of the receiver, and transmitting an alarm signal S7, as described below.

Level detector 7a and level detector 7b
Extracts a part of the synthesizing signal S5a and a part of the synthesizing signal S5b, and detects the levels of the signals S5a and S5b, respectively. When the level of the signal S5a is La,
The level of the signal S5b is set to Lb. The level detector 7s detects the level of the composite signal S6 and generates a level Ls. Each of these level detectors 7a, 7b and 7s performs envelope detection on the in-band spectrum of signals S5a, S5b and S6 using a diode detector or the like.

The level La of the synthesizing signal S5a described above,
The level Lb of the synthesizing signal S5b and the level La of the synthesizing signal S6 are supplied to the alarm detector 8. The alarm detector 8 determines the level La of the synthesizing signal S5a, the level Lb of the synthesizing signal S5b, and the level Ls of the synthesizing signal S6.
Therefore, in response to the level of the received signal S1a and the level of the received signal S1b, a malfunction of the phase compensation by the phase shifter 3, that is, the synthesizing signals S5a and S5b show a phase difference larger than the allowable phase difference, and the in-phase synthesis causes Detect a state separated by more than the phase difference. When detecting the malfunction of the phase compensation, the alarm detector 8 sends an alarm signal S7 to the alarm signal output terminal 10.

FIG. 2 is a diagram for explaining the diversity combining operation in this embodiment, and FIG. 3 is a diagram showing an example of alarm detection calculation in the alarm detector 8 in this embodiment.

Hereinafter, the operation of detecting the malfunction of the phase compensation will be described in detail with reference to FIGS. 1, 2 and 3.

The synthesizer 6 generates a synthesizing signal S having a constant level La.
5a and S5b of level Lb equal to or less than this are synthesized to generate a synthesized signal S6 of level Ls. Now, level L
When a = Lb = 0.5 and the signals S5a and S5b are in-phase combined, the level Ls becomes 1. At the opposite extreme, L
If a = Lb and reverse phase synthesis, Ls will be 0. FIG. 2 shows these intermediate states, where Lb <La = 0.5, and the phase difference between the signals S5a and S5b is θ. At this time, the level Ls of the composite signal S6 is represented by the equation (1). Ls = {(La + Lb · cos θ) ² + (Lb · sin θ) ² ｝ ^1/2 (1) In FIG. 3, the horizontal axis represents Lb / La when the phase difference θ is 0 ° and 90 °. And a graph with Ls as the vertical axis. The phase difference θ = 0 ° (Ls1) corresponds to the signals S5a and S5a.
5b is in a normally in-phase synthesized state. When the phase difference θ = 0 °, the equation (1) can be expressed by the equation (2).

Ls = La (1 + Lb / La) (2) As can be seen from equation (2) and FIG. 3, the level Ls (Ls1) of the composite signal S6 decreases as Lb / La decreases. When Lb becomes 0, Ls1 becomes 0.5, that is, 6 dB of the in-phase synthesis level of La = Lb.
Decrease.

When the phase difference θ = 90 °,
Equation (1) can be represented by equation (3).

Ls = (La ² + Lb ² ) ^1/2 = La ｛1+ (Lb / La) ² ｝ ^1/2 (3) The level of Ls (Ls2) at θ = 90 ° is (3)
As can be seen from the equation and FIG. 3, 0.7 when La = Lb.
07 (3 dB decrease in in-phase synthesis) to 0.5 when Lb = 0
To change.

The alarm detector 8 performs an alarm detection calculation based on the above-described phase synthesizing operation. It is clear that if there is a malfunction in the phase compensation by the phase shifter 3, the level Ls is lower than that in the in-phase synthesis. The alarm detector 8 calculates the amount of decrease in the level Ls to determine whether or not to send the alarm signal S7. The transmission of the alarm signal S7 is performed when the equation (4) is satisfied. Ls <｛(La + Lb · cos θth) ² + (Lb · sin θth) ² ｝ ^1/2 (4) where θth is the allowable phase error described above. θth is 9
When set to 0 °, Ls (Ls2) in equation (4) becomes (5)
Equation (6) is rewritten.

Ls <(La ² + Lb ² ) ^1/2 = La ｛1+ (Lb / La) ² ｝ ^1/2 (5) Ls ² <(La ² + Lb ² ) (6) Levels La, Lb and Considering the discriminability of Ls,
It is considered appropriate to determine the reduction of the level Ls of the composite signal S6 at about 0.707 (about 3 dB lower) at the time of in-phase synthesis, that is, to determine the malfunction of the phase compensation at a phase difference θ of about 90 °. However, when Lb / La decreases, the difference between the levels Ls1 and Ls2 decreases and the discriminability between the two decreases, so when Lb / La is small, Ls in the equation (5) or (6) is further reduced. It is good to set. The alarm detector 8 calculates the equation (4), the equation (5) or the equation (6), and sends out the alarm signal S7 when the level Ls satisfies these equations (see FIG. 3).

In the case where the equation (6) is used to judge the malfunction of the phase compensation, if the square detector is used for the level detectors 7a, 7b and 7s, the alarm detector 8 can be easily formed by using an operational amplifier and a comparator. Equation (6) can be calculated.

As described above, the present embodiment uses the level detectors 7a, 7b, 7s and the alarm detector 8 which have a simple configuration, and can reduce the phase in phase synthesis which is one of the most serious faults in the diversity receiver. A malfunction of compensation has been detected.

In this embodiment, the reception signals S1a and S1a
Although the detectors 7a and 7b are used for detecting the level of 1b, the AGC voltage of the receivers 2a and 2b may be used for detecting these levels.

Although the receivers 2a and 2b in the present embodiment perform the AGC operation, the receivers 2a and 2b do not have an AGC circuit, and the level La of the synthesizing signal S5a and the level of the synthesizing signal S5b are used. Even when all of Lb and the level Ls of the composite signal S6 change,
As is apparent from the equation (4), it is clear that a malfunction of the phase compensation can be sufficiently detected.

[0029]

As described above, according to the present invention, the alarm detector is shifted in response to the level La of the second received signal, the level Lb of the fourth received signal, and the level Ls of the composite signal of the diversity receiver. Since the malfunction of the phase compensation by the phase shifter is detected, the malfunction of the phase compensation in the phase synthesis, which is one of the most serious failures in the diversity receiver, can be detected using a circuit having a simple configuration. .

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram illustrating a diversity combining operation in the present embodiment.

FIG. 3 is a diagram showing an example of an alarm detection calculation in the alarm detector 8 of the embodiment.

[Explanation of symbols]

 1a, 1b Antenna 2a, 2b Receiver 3 Phase Shifter 4a, 4b Divider 5 Phase Detector 6 Combiner 7a, 7b, 7s Level Detector 8 Alarm Detector 9 Signal Output Terminal 10 Alarm Signal Output Terminal

Claims (3)

(57) [Claims] 1. A first receiver for receiving a first received signal to generate a second received signal, and receiving a third received signal coherent to the first received signal. A second receiver for generating a fourth received signal, a combiner for combining the second received signal and the fourth received signal to generate a combined signal, and a phase of the second received signal. A phase comparator that compares the phase of the fourth received signal with the phase of the fourth received signal to generate a comparison output;
A phase shifter that is controlled by the comparison output to compensate the phase so that the phase difference between the second received signal and the fourth received signal is minimized, and detects a level La of the second received signal. A first level detector, a second level detector for detecting a level Lb of the fourth received signal, a third level detector for detecting a level Ls of the composite signal, And an alarm detector for detecting a malfunction of phase compensation by the phase shifter in response to the level La of the second received signal, the level Lb of the fourth received signal, and the level Ls of the synthesized signal. Diversity receiver alarm detection method. 2. The alarm detector according to claim 1, wherein the detected levels La, Lb and Ls are represented by the formula Ls <｛(La + Lb).
・ Cos θth) ² + (Lb · sin θth) ² ｝ ^1/2
2. The alarm detection system for a diversity receiver according to claim 1, wherein an alarm signal is output when θth is a permissible phase error for determining a malfunction in the phase compensation. 3. The receiver according to claim 2, wherein the first receiver and the second receiver are receivers having substantially the same performance and performing AGC operation at the same AGC voltage, and the phase shifter is configured to receive the second reception signal. 2. The alarm detection system for a diversity receiver according to claim 1, wherein the alarm detection system is inserted between a combiner and the combiner.