JP3252893B2 - Multi-carrier automatic gain controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-carrier automatic gain control device, and more particularly to a multi-carrier automatic gain control device used for a microwave digital radio repeater for a non-regenerative station.

[0002]

2. Description of the Related Art This type of multi-carrier automatic gain control apparatus is a multi-carrier digital microwave radio relay apparatus, particularly a non-intermediate-frequency relay apparatus which relays a received multi-carrier at a carrier frequency without dropping it to baseband using a modem. An AGC device used for a reproducing station, which amplifies each carrier of a received multicarrier signal and stabilizes an output level at the same time.

In general, this kind of multi-carrier automatic gain control device includes a bandpass filter for selecting a predetermined carrier from received multi-carriers, a variable gain type amplifier for amplifying the carrier, and an output level of the amplifier. It comprises an AGC control circuit for detecting and controlling the output level to be constant.

This multi-carrier automatic gain control device has the following problems in transient response when a received carrier is cut off due to some failure and re-input. In the case where the level of the received carrier drops and finally stops, the AG
The C control circuit increases the gain of the amplifier in accordance with the level decrease and controls the gain up to the maximum gain in the control range. However, in a region where the level is further reduced and cut off, the gain is fixed at the maximum gain state. When the receiving carrier is restored and re-input,
Since the amplifier is in the maximum gain state, an excessively high level signal is output to the output side and returns to a normal level by the AGC operation. There is a problem that an excessively high level signal is temporarily output to the output side for the AGC control time, so that the output level overshoots.

[0005] As described above, when the output level of one carrier overshoots, there occurs a problem that the distortion wave of the excessive signal interferes with another carrier on the transmitting side that has become a multicarrier. Therefore, it is necessary to prevent the generation of the excessive signal, and as one of the measures, there is the following technique. That is, when the receiving carrier is disconnected, the AGC
The above-mentioned problem has been solved by storing the control voltage before the circuit was cut off, fixing the gain of the amplifier in this state, and starting control from this stored state at the time of re-input to ensure continuity of control. This is a technique for preventing the occurrence of blemishes.

For example, there is a technique described in Japanese Patent Application Laid-Open No. Hei 5-315978. The technique disclosed in this publication relates to an automatic gain control circuit corresponding to a burst signal used in a satellite communication device or the like. However, similar to this device, a transient response at the time of re-input of a received signal is performed by the following method. Solving the problem.

FIG. 2 is a block diagram showing this conventional circuit. According to this publication, as shown in FIG. 2, the detection switching unit 15 sets the memory 19 to a writable state when an input signal is present, and causes the switching unit 18 to select a signal from the comparison operation unit 20. Perform switching control. Further, when the input signal is interrupted, the writing operation of the memory 19 is stopped, and the switching means 18 is controlled so as to select the output of the memory 19. Thus, when the input signal is interrupted, the variable attenuator (V
ATT) 13 is fixed to the amount of attenuation immediately before the input signal is interrupted based on the signal read from the memory 19. At the time of re-input, the first delay means 16 and the second delay means 21
Thus, in order to recover after controlling the gain of the VATT 13, the generation of an excessive output signal is controlled by the transient response of the VATT 13.

[0008]

As described above, in the prior art, since the gain of the amplifier is fixed at the input level immediately before the input signal is cut off, just before the input level is cut off at the time of re-input. There is no problem if the signal is input at a level higher than this level, but if the signal is input at a level higher than this level, a signal at a level higher by the difference level is output. In particular, the input level may be very high at the time of restoration from a failure, and there is a problem that the above-described problem of the output signal overshoot at the time of re-input is not completely solved. In addition, there is a problem that a circuit is complicated because a memory or the like is used.

[0009]

SUMMARY OF THE INVENTION A multi-carrier automatic gain control device according to the present invention receives a multi-carrier signal of a microwave digital radio and amplifies the selected carrier by a plurality of band filters for selecting a predetermined carrier. A plurality of variable gain type amplifiers, a plurality of control circuits for varying the gain of the amplifier to stabilize the output level, and a first for synthesizing output signals of the respective amplifiers and returning them to multicarrier signals for transmission.
A multi-carrier automatic gain control device having a combiner for monitoring the output level of the amplifier, and when the monitored level falls below a reference value, outputs a phase inversion signal generated from the output signal of the amplifier to the output signal of the amplifier. A plurality of output signal control circuits for canceling the output signal and removing the phase inversion signal when the monitoring level returns to a normal value.

For example, specifically, each of the output signal control circuits includes a branching device that branches the output signal of the amplifier into two, and a switching device that receives one of the branching signals and turns on and off a passage of the input signal by a switching signal. , A phase inverting circuit for inputting the output signal of the switch and rotating the phase by 180 °, and receiving the other branch signal of the splitter and holding a phase difference of 180 ° with the inverted signal of the phase inverting circuit. Circuit that adjusts the phase as described above, a level detection circuit that monitors the level of the output signal of the delay circuit and outputs the switching signal when a level that is equal to or less than a first reference value and equal to or greater than a second reference value is detected. A second combiner for combining output signals of the delay circuit and the phase inverting circuit and inputting the combined signal to the first combiner.

The switching signal may be generated by the control circuit from a control signal that varies the gain of the amplifier.

Further, the phase inversion circuit and the delay circuit may use a delay cable or a pattern having predetermined characteristics.

Further, the switching device may use an FET (field effect transistor) as a switching element for turning on and off a signal passage.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. This figure shows a case where there are two carrier signals for the sake of simplicity, and a microwave digital signal is received by a receiver RX via an input antenna.
This is converted into a multi-carrier signal and input to the multi-carrier automatic gain control device of the present invention.

This apparatus receives a multicarrier signal and splits the signal into two, a bandpass filter 6a, 6b for selecting a predetermined carrier from the multicarrier, and a variable gain type for amplifying the selected carrier. Amplifiers 5a and 5b, and AGC control circuits 9a and 9a that vary the gain of amplifiers 5a and 5b with control signals 102a and 102b to stabilize the output level.
9b, splitters 8a and 8b that split the output signals of the amplifiers 5a and 5b into two, splitters 2a and 2b that input one of the split signals and turn on and off the passage by a switching signal, and splitters 2a and 2b. Phase inverting circuits 3a and 3b for inputting the output signal of (1) and rotating the phase by 180.degree.
Delay circuits 4a and 4b for receiving the other branch signal and adjusting the phase so as to maintain a 180 ° phase difference with the inverted signals of the phase inverting circuits 3a and 3b, and the delay circuits 4a and 4b
The switching signal 10 is monitored when the level of the output signal is monitored to be lower than the first reference value and higher than the second reference value.
Level detection circuits 1a and 1b for outputting 1a and 101b
And combiners 7a, 7b and combiners 7a, 7 for combining output signals of delay circuits 4a, 4b and phase inverters 3a, 3b.
and a combiner 10 for combining the output signal of b and returning to a multicarrier signal.

The multicarrier signal synthesized by the synthesizer 10 is converted into a microwave digital signal by the transmitter TX and transmitted to the next station via the transmitting antenna.

The phase inversion circuit 3 and the delay circuit 4 use a cable or a pattern for delaying the phase. Further, an FET (field effect transistor) is used as a switching element of the switch 2.

Next, the operation of the present apparatus will be described. When the input level of the received carrier is within the preset allowable range, the switching unit 2 opens the passage of the input signal and does not input the signal to the phase inversion circuit 3 because there is no input of the switching signal 101. Therefore, this device operates as a normal AGC device.
When the input level falls below or falls below the lower limit of the allowable variation range, the level detector 1 detects a decrease in the level of the AGC output and outputs a switching signal 101. The switch 2 closes the passage by the switching signal 101 and inputs a signal to the phase inversion circuit 3. The inverted signal whose phase is inverted from the output of the phase inverting circuit 3 is combined with the in-phase signal output from the delay circuit 4 by the combiner 7, and the output is canceled to zero.

When a received carrier is re-input, the level detector 1 detects a constant AGC output level, confirms that the input level is within an allowable fluctuation range, and switches the switching signal 101.
Stop output of Therefore, the switch 2 is in the open state, and the entire operation is restored. If the input level at the time of re-input is higher than the upper limit of the allowable variation range, the level detector 1 does not stop sending the switching signal 101, so that the output level does not overshoot at the time of re-input.

The level detector 1 may generate the switching signal 101 using the gain control signal 102 of the AGC control circuit 8, and in this case, the circuit can be simplified.

[0021]

As described above, the multi-carrier automatic gain control device of the present invention adds the phase inversion signal to the output signal to reduce the output to zero when the input level falls below the allowable operation range or cuts off the output signal. At the time of input, the normal level AGC operation is performed by removing the phase inversion signal after the input level is restored to within the allowable operation range. Therefore, in the transient response at the time of input again, the output level overshoots and other carriers This has the effect of completely preventing the problem of interfering with the data. Further, since no memory or the like is used as in the conventional example, there is also an effect that the circuit is simplified.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

 1a, 1b Level detector 2a, 2b Switch 3a, 3b Phase inversion circuit 6a, 6b Bandpass filter 5a, 5b Amplifier 4a, 4b Delay circuit 7a, 7b Combiner 8a, 8b Branch 9 Branch 10 Synthesizer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03G 3/20-3/34 H04B 7/15

Claims (5)

(57) [Claims] 1. A plurality of bandpass filters for receiving a multicarrier signal of a microwave digital radio and selecting a predetermined carrier, a plurality of variable gain amplifiers for amplifying the selected carrier, and a variable gain of the amplifier. A multi-carrier automatic gain control device having a plurality of control circuits for stabilizing the output level and a first synthesizer for synthesizing the output signals of the respective amplifiers and returning the multi-carrier signals to be transmitted. When the monitored level falls below the reference value, a phase inversion signal generated from the output signal of the amplifier is added to the output signal of the amplifier to cancel the output signal and return the monitored level to a normal value. A multi-carrier automatic gain control device comprising a plurality of output signal control circuits for removing the phase inversion signal. 2. Each of the output signal control circuits includes a branching device that branches the output signal of the amplifier into two, a switching device that receives one of the branching signals, and turns on and off a passage of the input signal by a switching signal. Input the output signal of the switch and set the phase to 18.
A phase inverting circuit for rotating 0 °, and the other branch signal of the branching device is inputted,
A delay circuit that adjusts the phase so as to maintain the phase difference between the two, and monitors the level of the output signal of the delay circuit, and outputs the switching signal when a level that is equal to or less than a first reference value and equal to or greater than a second reference value is detected. 2. The multi-level multiplexing device according to claim 1, further comprising: a level detection circuit that performs the operation, and a second combiner that combines output signals of the delay circuit and the phase inversion circuit and inputs the combined signal to the first combiner. Automatic carrier gain control device. 3. The multi-carrier automatic gain control device according to claim 2, wherein the switching signal is generated by the control circuit from a control signal that varies a gain of the amplifier. 4. The multi-carrier automatic gain control device according to claim 2, wherein the phase inverting circuit and the delay circuit use a delay cable or a pattern having predetermined characteristics. 5. The multi-carrier automatic gain control device according to claim 2, wherein said switching device uses a field effect transistor (FET) as a switching element for turning on and off a signal passage.