JPH0348702B2 - - Google Patents

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to an automatic gain control device for television relay broadcasting equipment having parallel operating power amplifiers, and in particular, when one of the power amplifiers fails, the failure signal is This invention relates to an automatic gain control device that changes a reference voltage by.

(2) Prior art and problems Television relay broadcasting equipment generally receives a weak signal, amplifies it, and in order to prevent interference, it uses a basic device that converts the frequency to a frequency that is suitable for the relay station, and amplifies this output. Consists of multiple power amplifiers,
If the power amplifier is required to have a large output, it has a configuration in which N individual power amplifiers are connected in parallel.

For example, FIG. 1 shows the configuration of a device of this type according to the prior art, in which a plurality of power amplifiers 4 _-1 , 4 are connected in parallel between a distributor 2 and a combiner 3 on the output side of a basic device 1. _-2 , . . . 4 _-4 are provided, and the output of the combiner 3 is connected to the antenna 5. The configuration is such that an automatic gain unit (AGC) 6 is connected from the output side of the basic device 1 to control the gain of the basic device _. Each of the four amplifiers ₁ to _4-4 had an amplification capacity of 30W, and the final output from synthesizer 3 was amplified to about 100W.

In such a conventional device, the input to the AGC 6 was connected from the output side of the basic device 1, so although the AGC acts on the output fluctuations of the basic device 1, the power amplifiers 4 _-1 to 4 _-4 AGC does not operate in response to output fluctuations. Therefore, the power amplifier 4
Since the gain fluctuations of _-1 to _4-4 directly lead to output fluctuations, it was necessary to severely suppress the gain fluctuations of each power amplifier _4-1 to _4-4 .

This has become a problem, especially in the recent times when high precision in suppressing fluctuations is required.

(3) Purpose of the Invention The present invention solves the above-mentioned problems in conventional devices, and when each power amplifier is normal, the output is maintained constant by AGC even if their gains vary slightly, and any one of the power amplifiers is Power amplifier 4 _- i (i= ₁ , ₂
.

(4) Structure of the Invention In order to achieve this object, the automatic gain control device for television relay broadcasting equipment having parallel operation power amplifiers of the present invention includes a basic device that receives a signal and performs frequency conversion according to the received signal. In an automatic gain control device for a television relay broadcasting device having a parallel operation power amplifier consisting of a plurality of amplifiers each amplifying signals branched from the output of the basic device and a combiner combining the outputs of the amplifiers, An AGC amplifier whose input side is connected to the output side of the parallel operation power amplifier and whose output side is connected to the input side of the basic device, and a failure signal indicating a failure state of each of the amplifiers is detected, and the amplifier is normal. Sometimes a predetermined level signal is used, and when an abnormality occurs, a level signal lower than the predetermined level signal is used.
A control device that changes the AGC control state by inputting it as a basic voltage to the other input side of the AGC amplifier;
It is characterized by having the following.

(5) Embodiments of the invention Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows a first embodiment of an automatic gain control device for television relay broadcasting equipment having a parallel operating power amplifier according to the present invention, FIG. 3 shows a second embodiment of the present invention, and FIG. 4 shows the present invention. A third embodiment of the invention will be shown.

In FIG. 2, 11 is a basic device, 12 is a distributor, 13 is a combiner, and 14 _-1 , 14 _-2 , . . . , 14 _-4 are individual power amplifiers connected in parallel.
15 is an antenna, and 16 is an AGC amplifier. In the present invention, one of the inputs of the AGC amplifier 16 is taken from the output side of the combiner 13. 17 is a reference voltage control device which sets the basic voltage to be applied to the AGC amplifier 16 to an arbitrary value. Note that 18 indicates a diode.

The operation of the device configured in this manner will be described next.

In the present invention, as can be seen from FIG. 2, the output of the synthesizer 13 is applied to one input of the AGC amplifier 16 via the diode 18, and the other input of the AGC amplifier 16 is connected to the reference A reference voltage from a voltage control device 17 is provided. The reference voltage is applied to each power amplifier 14 _-1 ,
When a failure signal from _14-2 ... _14-4 is input, a predetermined value is determined according to the failure signal. Furthermore, a power amplifier 14 _- i (i= ₁ , ₂
), the output power will generally change by (n-t/n) ² (where n is the number of power amplifiers, t is the number of failed power amplifiers, and t<n ) The reference voltage at the time of failure detection is changed.

That is, for example, if the power amplifier 14 _-4 has failed now, a failure signal is given to the reference voltage control device 17 via L ₄ of the failure detection lines L ₁ to L ₄ , so that the reference voltage is used as the failure signal. At the same time, the output of the synthesizer 13 changes to (3/4) ² = 9/16, and the change is sent to the AGC
The voltage is applied to the amplifier 16 and compared with a reference voltage, and the error voltage is negatively fed back to the basic device 11 to control the gain. Therefore, each power amplifier 1
4 _- The output of i (i = 1, 2...n) is P/n (P is the output of the combiner during normal operation), as in normal conditions.
AGC is applied, and the composite output is P[(n-
1)/n] ² . If the voltage is extracted from the output side of the synthesizer 13 without a reference voltage control device,
Power amplifier 14 _-1 as when applying AGC,
_14-2 and _14-3 (in the case of the illustrated embodiment), no excessive drive is applied, so deterioration of the characteristics of these power amplifiers or damage to them is prevented. , the output level is significantly stabilized and the accuracy of the fluctuation rate is improved. For failure detection, for example, a part of the output signal of each power amplifier is taken out, diode detection is performed to obtain a DC voltage, and this is input to a comparator to obtain a voltage that is less than 1/2 or more than twice the normal detected voltage. Appropriate means can be used, such as determining a failure, or determining a failure when a considerable difference occurs when the detected voltages of the outputs of the respective power amplifiers are compared.

FIG. 3 shows another embodiment of the invention, in this case two basic devices 11 and 11'
is used, and the second point is that a branching device 19 and a switch device 20 for switching the basic device 11 and the basic device 11' are provided.
This differs from the device shown in the figure, and all other components are the same and are given the same reference numerals.
In operation, as in the case of the device of Fig. 2,
The failure signal of the failed one of the power amplifiers 14 _-1 to 14 _-4 is detected and the reference voltage of the reference voltage control device 17 is changed, and the error signal output from the AGC amplifier 16 is used to control the switching device 20. The gain of the basic device 11 or 11' connected thereto is controlled.

FIG. 4 shows the configuration of a device according to yet another embodiment of the present invention. In this device, a second AGC amplifier 16' is provided outside the first AGC amplifier 16,
The basic device 11 inputs the input to the first AGC amplifier.
At the same time, the input to the second AGC amplifier 16' is taken from the output side of the combiner 13, and the outputs of the two AGC amplifiers 16 and 16' are supplied to the changeover switch 21. _-1 ~
The configuration is such that the basic device 11 is controlled via the changeover switch 21 in response to a failure signal from _14-4 . That is, the embodiment shown in FIG. 4 differs in that a failure signal from each power amplifier is used to switch the changeover switch 21 instead of the reference voltage control device 17 shown in FIG. 3, and other components are the same. all have the same reference number.

The functions of the apparatus shown in FIG. 4 are as follows. In other words, each power amplifier 4 _- i (i = ₁ , ₂ ,...n) is generally adjusted so that each characteristic is optimized at a certain operating point, so if any one power amplifier fails, each power amplifier 4-i (i = 1, 2,...n) The output from the power amplifier is, if the output of all normal power amplifiers is P, then for example, if only the AGC from the combiner 13 side is used, each power amplifier 14 _-1 to 14
The output of _-4 is P/n _-1 (w), and the final output is constant, but the characteristics of each power amplifier 4 _- i (i = ₁ , ₂ ...) tend to deteriorate.

Therefore, in the case of the embodiment shown in FIG.
By switching the _first AGC amplifier 16 and ^the second AGC amplifier 16' on their output sides, each This is to maintain the power amplifier in its normal state without deteriorating its characteristics. In other words, during normal operation, fluctuations due to temperature fluctuations in the amplifier are absorbed by the AGC loop of the AGC amplifier 16', but if a failure occurs in the amplifier, the device becomes the same as the conventional example, so stability during normal operation is reduced. The purpose is to

(6) Effects of the Invention In the device of the present invention, the input of the feedback circuit is always taken from at least the output side of the combiner in all embodiments, so stable and highly accurate power amplification control can be performed. Since no unreasonable input is applied to each power amplifier in parallel, their deterioration and destruction are prevented.

[Brief explanation of drawings]

FIG. 1 shows an AGC device for a television relay broadcasting device according to the prior art, FIG. 2 shows a first embodiment of the AGC device according to the present invention, FIG. 3 shows a second embodiment of the device according to the present invention, and FIG. The figure shows a third embodiment according to the invention. In the figure, 11 is a basic device, 12 is a distributor, 13 is a combiner, 14 _- i (i = ₁ , ₂ ... ₄ ) is a power amplifier, 15
16 is an antenna, 16 is an AGC amplifier, 17 is a reference voltage control device, 18 is a diode, 19 is a branching device, 20 is a switch device, and 21 is a changeover switch.

Claims (1)

[Claims] 1. A basic device that receives a signal and performs frequency conversion according to the received signal, a plurality of amplifiers that amplify the signals branched from the output of the basic device, and the outputs of the amplifiers are combined. In an automatic gain control device for a television relay broadcasting device having a parallel operation power amplifier consisting of a combiner, one of the input sides is connected to the output side of the parallel operation power amplifier, and the output side is connected to the input side of the basic device. detects a failure signal representing a failure state of the AGC amplifier and each of the amplifiers, and outputs a predetermined level signal when the amplifier is normal;
An automatic gain for a television relay broadcasting device, comprising: a control device that changes the AGC control state by inputting a level signal lower than the predetermined level signal to the other input side of the AGC amplifier as a basic voltage in the event of an abnormality. Control device. 2. A plurality of the basic devices are connected in parallel, and the output of the AGC amplifier is connected to the input of each of the plurality of basic devices, and a switch means is provided for switching the output from one of the basic devices. An automatic gain control device for a television relay broadcasting device having a parallel operation power amplifier according to claim 1. 3 Parallel operation consisting of a basic device that receives a signal and performs frequency conversion according to the received signal, multiple amplifiers that amplify each signal branched from the output of the basic device, and a synthesizer that combines the outputs of the amplifiers. In an automatic gain control device for a television relay broadcasting device having a power amplifier, a first AGC provided for the basic device;
an amplifier, and a second amplifier whose input is connected to the output side of the parallel operating power amplifier and whose output is connected to the input side of the basic device.
an AGC amplifier; and a control device that detects a failure signal representing a failure state of each of the amplifiers and controls the second AGC amplifier to operate when the amplifier is normal and the first AGC amplifier to operate when the amplifier is abnormal. An automatic gain control device for a television relay broadcasting device, characterized in that: