JP2001024601A - Received gain monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a received gain monitor, dispensing with addition of a synthesis circuit to combine a received signal with a pilot signal to the input side of an FET amplifier and capable of preventing degradation of a noise index, when in the case of an outdoor device with the FET amplifier by which the received signal and bias voltage are supplied to the gate of a first stage FET via an input circulator. SOLUTION: A pilot signal Sp to monitor received gain is superposed on a gate bias voltage Vg and inputted in a dummy port of the circulator 25 by a directional coupler 26. The gate bias voltage Vg inputted in the dummy port is supplied to the gate of an initial stage FET of an FET amplifier circuit 22 via the central conductor of the circulator 25. The pilot signal Sp inputted in the dummy port is transmitted from the input port of the circulator 25 to a receiving filter 21, however, since the frequency of the pilot signal Sp exists outside the passing band of the receiving filter 21, the pilot signal Sp is reflected by the receiving filter 21, returned to the input port of the circulator 25, combined with the received signal Sr and supplied to the gate of the initial FET of the FET amplifier circuit 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reception gain monitoring device for monitoring a gain variation of an outdoor device installed near an antenna for amplifying a reception signal.

[0002]

2. Description of the Related Art Generally, in order to enhance reception sensitivity, an outdoor device for amplifying a received signal is separately installed near an antenna.
It is connected to an indoor unit having a receiver via a coaxial cable. Then, in order to monitor the reception amplification state of the outdoor device on the indoor device side, for example, according to Japanese Patent Laid-Open No. 4-82432, as shown in FIG. I have.

That is, a pilot oscillator 1 is provided on the receiver side.
15 is provided, the output pilot signal is input to the circulator 110, and transmitted to the receiving amplifier via the coaxial cable 109. On the receiving amplifier side, the demultiplexing circuit 105
Circulator 106 and pilot filter 10
7, the pilot signal is demultiplexed by the attenuator 108, the received signal and the pilot signal are combined by the combining circuit 103 and input to the receiving amplifier 104, and the signal amplified by the receiving amplifier 104 (the received signal and the (A pilot signal) to the receiver via the circulator 106 and the coaxial cable 109.

On the receiver side, a pilot signal is separated by a separation circuit 111, detected by a pilot detection circuit 113, and the detection level is compared with an output level of a pilot oscillator 115 by a pilot level comparison circuit 114. , The gain of the receiving amplifier 104 installed outdoors is monitored.

[0005]

SUMMARY OF THE INVENTION In the above-mentioned conventional example, the receiving amplifier of an outdoor device is disclosed in Japanese Patent Publication No. 55-44487.
In the case of a configuration including the FET amplifier disclosed in Japanese Patent Application Laid-Open Publication No. H11-27139, that is, in a configuration in which the gate bias voltage of the first-stage FET of the FET amplifier is supplied through a dummy port (terminal resistor connection terminal) of the input circulator, A synthesizing circuit for synthesizing the signal and the pilot signal is represented by F
It needs to be added to the input side of the ET amplifier. For this reason,
There is a problem that the received signal is attenuated by the added combining circuit and the noise figure is degraded.

An object of the present invention is to provide a combining device for combining a received signal and a pilot signal in an outdoor device having an FET amplifier in which a received signal and a bias voltage are supplied to a gate of a first-stage FET via an input circulator. It is an object of the present invention to provide a reception gain monitoring device which does not need to add a circuit to an input side of an FET amplifier and can prevent deterioration of a noise figure.

[0007]

SUMMARY OF THE INVENTION A reception gain monitoring apparatus according to the present invention measures the gain fluctuation of an outdoor apparatus installed near an antenna and amplifying a received signal on the indoor apparatus side connected to the outdoor apparatus by a coaxial cable. A reception gain monitoring device for monitoring, wherein the outdoor device includes a reception filter that allows a desired reception signal to pass from among the signals received by the antenna, and a plurality of FETs (field-effect transistors) that are cascade-connected. A FET amplifying circuit for amplifying a signal input to a gate, a bias circuit for generating a bias voltage to be supplied to the FET amplifying circuit, a receiving signal having passed through the receiving filter being received at an input port, and a first stage of the FET amplifier being received from an output port. Output to the gate of the FET and the first stage F
A circulator for receiving a bias voltage supplied to the gate of the ET at a dummy port and supplying the bias voltage to the gate of the first-stage FET from the output port, a pilot oscillator for generating a pilot signal of a constant level outside the frequency band of the received signal, A directional coupler that is connected to a dummy port of a circulator and that superimposes the pilot signal on a bias voltage supplied to the gate of the first-stage FET and outputs the pilot signal to the dummy port, wherein the indoor device is an FET amplifier of the outdoor device. A branch circuit for extracting and branching the pilot signal included in the signal amplified and transmitted through the coaxial cable, and detecting the level of the pilot signal branched by the branch circuit to thereby change the reception gain of the outdoor device. And a reception gain monitoring means for monitoring the reception gain.

[0008] In the above configuration, the outdoor device may divide the pilot signal output by the pilot oscillator and output a divided pilot signal having a frequency sufficiently lower than the frequency of the received signal and the pilot signal. And a combining circuit that combines the frequency-divided pilot signal with the output signal of the FET amplifier and sends the signal to the coaxial cable, wherein the indoor device includes the frequency divider transmitted via the coaxial cable. A level detection circuit of a frequency-divided pilot signal for extracting and detecting a level of a pilot signal, an oscillation output monitoring circuit for monitoring an output level variation of the pilot oscillator based on a detection result of the level detection circuit,
A correction circuit that corrects the reception gain fluctuation detected by the reception gain monitoring means based on the output level fluctuation result of the pilot oscillator detected by the oscillation output monitoring circuit.

The oscillation output monitoring circuit has a function of transmitting an alarm signal when the output level of the pilot signal oscillator fluctuates to a value equal to or greater than a preset value.
The correction circuit is configured to stop the correction processing when receiving the alarm signal.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. An outdoor device 2 installed near the antenna 1 and amplifying a received signal is connected to an indoor device 3 via a coaxial cable 4.

The outdoor apparatus 2 includes a reception filter 21 for passing a desired reception signal Sr from among signals received by the antenna 1, an FET amplification circuit 22, and a bias circuit for generating a bias voltage to be supplied to the FET amplification circuit 22. 23,
A pilot signal oscillator 24 for generating a pilot signal Sp for monitoring a reception gain;
A circulator 2 provided between the ET amplifying circuit 22
5 and a directional coupler 26 for superimposing the pilot signal Sp on the gate bias voltage Vg supplied to the gate of the first-stage FET of the FET amplification circuit 22.

Here, the FET amplifier circuit 22 of the outdoor device 2
Is an amplifier circuit in which a plurality of FETs (field-effect transistors) are cascaded. A gate bias voltage Vg is supplied to the gate of the first-stage FET via the circulator 25 to amplify a signal input to the gate of the first-stage FET. .

The circulator 25 is a triplate type circulator whose center conductor is insulated from the external conductor in a direct current manner, and has three terminals of an input port P1, an output port P2 and a dummy port P3. Then, the reception signal Sr is received by the input port P1, and the gate bias voltage Vg
From the output port P2 to the dummy port P3.
The reception signal Sr and the gate bias voltage Vg are supplied to the gate of the first-stage FET of the amplifier circuit 22.

The pilot signal oscillator 24 outputs a pilot signal Sp of a fixed level whose frequency is set outside the frequency band of the received signal.

The directional coupler 26 has a gate bias voltage Vg via an open dummy resistor 27 at an input end of the two input ends which is directly connected to the output end of the directional coupler 26.
When the pilot signal Sp is received at the other input terminal terminated by the terminating resistor, the pilot signal Sp is superimposed on the gate bias voltage Vg and output to the dummy port P3 of the circulator 25.

On the other hand, the indoor unit 3 includes a branch circuit 31 for extracting and branching a pilot signal Sp 'included in a signal transmitted from the outdoor unit 2 via the coaxial cable 4, and a reception signal Sr passing through the branch circuit 31. 'Demodulator 3
2 and the pilot signal S branched by the branch circuit 31
a level detection circuit 33 for detecting the level of p ', a reference detection level generation circuit 34 for outputting a reference detection level of a pilot signal when the outdoor device 2 is operating normally, and a comparison between the detected pilot signal level and the reference detection level And a reception gain monitoring circuit 35 for monitoring the fluctuation of the reception gain of the outdoor apparatus 2.

Next, the operation will be described.

The reception signal Sr received by the antenna 1 and passing through the reception filter 21 is input to the input port P1 of the circulator 25, is input from the output port P2 of the circulator 25 to the FET amplification circuit 22, and is amplified.
The data is transmitted to the indoor device 3 via the coaxial cable 4. The received signal Sr input to the indoor device 3 passes through the branch circuit 8 and is input to the receiver 32, where it is demodulated into a baseband signal So.

The pilot signal Sp for monitoring the reception gain is supplied to the gate bias voltage V by the directional coupler 26.
g and the dummy port P of the circulator 25
3 is input. The gate bias voltage Vg is supplied from the output port P2 to the FE through the center conductor of the circulator 25.
It is supplied to the gate of the first stage FET of the T amplifier circuit 22.

The pilot signal Sp input to the dummy port P3 is sent from the input port P1 of the circulator 25 to the reception filter 21, but the pilot signal Sp
Is outside the pass band of the reception filter 21,
The pilot signal Sp is reflected by the reception filter 21 and returns to the input port P1 of the circulator 25. Then, it is combined with the reception signal Sr, and is output from the output port P2 of the circulator 25 to the first stage F of the FET amplification circuit 22.
The signal is supplied to the gate of the ET, amplified with the received signal Sr, and transmitted to the indoor unit 3 via the coaxial cable 4.

The pilot signal S sent to the indoor unit 3
p ′ is extracted and branched by the branch circuit 31 and input to the level detection circuit 33, where the signal level is detected. The reception gain monitoring circuit 35 monitors the reception gain fluctuation of the outdoor device 2 by comparing the detected pilot signal level with the reference detection level, and outputs a monitoring result.

In this way, the reception signal and the pilot signal are added to the gate of the first stage FET of the FET amplification circuit without adding a synthesis circuit for synthesizing the reception signal and the pilot signal to the input side of the FET amplifier. And a gate bias voltage.

FIG. 2 is a block diagram showing another embodiment of the present invention.

The same components as those shown in FIG. 1 are denoted by the same reference numerals. The difference from the embodiment shown in FIG. 1 is that even if the output level of the pilot signal oscillator 24 fluctuates, the reception gain fluctuation can be correctly monitored.

In the embodiment shown in FIG. 1, fluctuations in the reception gain are monitored on the assumption that the output level of the pilot signal oscillator 24 is constant. If the output level of the pilot signal oscillator 24 fluctuates, Since the level of the pilot signal detected by the indoor device 3 fluctuates in spite of the fact that the reception gain of the outdoor device does not fluctuate, the fluctuation of the reception gain cannot be correctly monitored. In the embodiment shown in FIG.
By generating a signal that varies in accordance with the output level of the pilot signal, synthesizing the signal with the output signal of the FET amplification circuit 22 and sending the signal to the indoor unit, even if the output level of the pilot signal oscillator 24 fluctuates, the reception gain fluctuation can be correctly corrected. They are being monitored.

In FIG. 2, the outdoor apparatus 2 further includes a frequency divider 28 and a combining circuit 29 in addition to the components shown in FIG. The frequency divider 28 divides the frequency of the pilot signal Sp1 (hereinafter referred to as an output pilot signal) output from the pilot signal oscillator 24, and outputs a pilot signal Sp2 (of which frequency is sufficiently lower than the frequencies of the reception signal Sr and the pilot signal Sp1. This signal is hereinafter referred to as a frequency-divided pilot signal). The combining circuit 29 combines the frequency-divided pilot signal Sp <b> 2 with the output signal of the FET amplifier circuit 22 and sends out the signal to the coaxial cable 4.

The indoor unit 3 further includes, in addition to the components shown in FIG. 1, a branch circuit 36 for extracting and branching a frequency-divided pilot signal Sp2 'included in a signal transmitted via the coaxial cable 4. Divided frequency division pilot signal Sp
A level detection circuit 37 for detecting the level of 2 '; an oscillation output monitoring circuit 38 for comparing the detection level of the frequency-divided pilot signal Sp2' with the reference detection level to monitor the level fluctuation of the output pilot signal Sp1; A correction circuit 39 is provided for correcting the monitoring result (reception gain fluctuation) of the reception gain monitoring circuit 35 based on the pilot oscillation output level fluctuation detected by the output monitoring circuit 38. Note that the synthesis circuit 2
9 and the branch circuit 36 can each be configured using a low-pass filter and a high-pass filter.

If the level of the output pilot signal Sp1 fluctuates while the FET amplifying circuit 22 is operating normally, the level of the frequency-divided pilot signal Sp2 also fluctuates at the same rate. The circuit 38 can detect the level fluctuation rate of the output pilot signal Sp1 by detecting the level fluctuation rate of the frequency-divided pilot signal Sp2 '. Since the level of the pilot signal Sp1 input to the FET amplifier circuit 22 also changes at the same rate, the level of the output pilot signal Sp1 'detected by the level detection circuit 33 of the indoor device 3 also changes at the same rate. Therefore, a correction circuit 39 is provided, and the reception gain fluctuation result detected by the reception gain monitoring circuit 35 is transmitted to the oscillation output monitoring circuit 3.
By correcting with the level fluctuation rate of the frequency-divided pilot signal Sp2 'detected by the step 8, even if the output level of the pilot signal oscillator 24 fluctuates, the fluctuation of the reception gain can be correctly monitored.

When the output level of pilot signal oscillator 24 fluctuates above a preset value, that is, oscillation output monitoring circuit 38 outputs frequency-divided pilot signal Sp.
An alarm signal is transmitted when it is detected that the level fluctuation of 2 'has fluctuated beyond a preset value, and the correction circuit 39 stops the correction processing when receiving the alarm signal. With this configuration, it is possible to prevent erroneous correction of the reception gain fluctuation.

[0031]

As described above, according to the present invention, a received signal and a pilot signal are synthesized by superimposing a pilot signal on a gate bias voltage by a directional coupler and supplying the pilot signal to a dummy port of a circulator. Without adding a combining circuit to the input side of the FET amplifier, the received signal, pilot signal and gate bias voltage can be supplied to the gate of the first stage FET of the FET amplifier circuit, thereby preventing noise figure degradation. it can.

Also, a frequency-divided pilot signal that changes according to the output level of the pilot signal oscillator is generated and sent to the indoor unit, and the reception gain fluctuation detected by the indoor unit is calculated based on the level fluctuation of the frequency-divided pilot signal. By performing the correction, it is possible to correctly monitor the reception gain fluctuation of the outdoor device. Furthermore, by stopping the correction process when the level fluctuation of the frequency-divided pilot signal fluctuates beyond a preset value, it is possible to prevent the erroneous correction of the reception gain fluctuation.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 2 Outdoor device 3 Indoor device 21 Reception filter 22 FET amplification circuit 23 Bias circuit 24 Pilot signal oscillator 25 Circulator 26 Directional coupler 28 Divider 29 Synthesis circuit 31, 36 Branch circuit 33, 37 Level detection circuit 35 Reception gain monitoring circuit 38 Oscillation output monitoring circuit 39 Correction circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J100 AA02 AA09 BA01 BB01 BB21 CA01 CA31 CA33 DA07 EA02 FA02 SA02 5K042 BA11 BA14 CA02 CA05 CA12 CA16 CA17 CA19 DA16 EA02 EA03 EA06 EA15 FA06 FA13 FA21 FA22 GA02 HA13 5K06 AB00 AD08 AE00 AE03 AE04 AF00 AF04 AG03 BC03 BD02 BF04

Claims (6)

[Claims] 1. A reception gain monitoring device for monitoring a gain variation of an outdoor device installed near an antenna and amplifying a reception signal on an indoor device side connected to the outdoor device with a coaxial cable, wherein the outdoor device includes: Is a reception filter for passing a desired reception signal from signals received by the antenna;
ET (Field Effect Transistor) connected in cascade and the first stage FE
A FET amplifying circuit for amplifying a signal input to the gate of T; a bias circuit for generating a bias voltage to be supplied to the FET amplifying circuit; a receiving signal passed through the receiving filter to an input port; To the gate of the first-stage FET and the first-stage FE
A circulator for receiving a bias voltage supplied to the gate of T at a dummy port and supplying the bias voltage to the gate of the first-stage FET from the output port, a pilot oscillator for generating a pilot signal having a constant level outside the frequency band of the reception signal, Superimposing means for superimposing the pilot signal on a bias voltage supplied to a gate of the first-stage FET and connected to a dummy port of a circulator and outputting the pilot signal to the dummy port, wherein the indoor device is amplified by an FET amplifier of the outdoor device. A branch circuit for extracting and branching the pilot signal included in the signal transmitted through the coaxial cable, and detecting a level of the pilot signal branched by the branch circuit to monitor a reception gain variation of the outdoor device. Reception gain monitoring means for monitoring the reception gain Visual device. 2. The superimposing means of the outdoor device, wherein:
2. The reception gain monitoring device according to claim 1, wherein the directional coupler receives a bias voltage and the pilot signal supplied to the gate of the ET, respectively, and superimposes the pilot signal on the bias voltage and outputs the resultant signal. 3. The outdoor device generates a signal that changes according to the output level of a pilot signal output by the pilot oscillator, combines the signal with an output signal of the FET amplifier, and sends the signal to the coaxial cable. Means, wherein the indoor device detects a signal that changes in accordance with the output level sent out via the coaxial cable, and monitors output level variation of the pilot oscillator; and 2. The reception gain monitoring device according to claim 1, further comprising: means for correcting a reception gain fluctuation detected by said reception gain monitoring means based on an output level fluctuation monitoring result. 4. A frequency divider which divides a pilot signal output by the pilot oscillator and outputs a frequency-divided pilot signal having a frequency sufficiently lower than the frequencies of the reception signal and the pilot signal. A combining circuit for combining the frequency-divided pilot signal with the output signal of the FET amplifier and transmitting the signal to the coaxial cable, wherein the indoor device includes the frequency-divided pilot signal transmitted via the coaxial cable. A level detection circuit of a frequency-divided pilot signal for extracting and detecting a level, and an oscillation output monitoring circuit for monitoring an output level variation of the pilot oscillator based on a detection result of the level detection circuit. 3. The reception gain monitoring device according to 2. 5. A correction circuit for correcting a reception gain fluctuation detected by said reception gain monitoring means based on an output level fluctuation result of said pilot oscillator detected by said oscillation output monitoring circuit. Receiving gain monitoring device. 6. The oscillation output monitoring circuit has a function of transmitting an alarm signal when an output level of the pilot signal oscillator fluctuates above a preset value, and the correction circuit receives the alarm signal. 6. The reception gain monitoring device according to claim 5, wherein the correction process is stopped when the error occurs.