JPH1051344A - High frequency signal receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the reception performance of both terrestrial broadcast signals and CATV signals by automatically judging whether signals supplied to an antenna terminal are the terrestrial broadcast signals or the CATV signals and controlling an AGC circuit corresponding to the result. SOLUTION: By the control of a microcomputer 7, when the microcomputer 7 recognizes terrestrial broadcast, an AGC voltage from a VIF circuit 4 is connected to the AGC circuit 2 by the switch 8 of a first set and the DC voltage of a video signal circuit 9 is connected to a tuner 3 by the switch 8 of a second set. Also, at the time of recognizing CATV, the DC voltage of the video signal circuit 9 is supplied to the AGC circuit 2 by the switch 8 of the first set and the AGC voltage is supplied from the VIF circuit 4 to the tuner 3 by the switch 8 of the second set. In such a manner, whether this device is connected to the terrestrial broadcast signals or connected to the CATV signals is automatically judged and the AGC circuit 2 inserted between the antenna terminal 1 and the tuner 3 is controlled corresponding to the result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency signal receiver used for both terrestrial broadcast reception and CATV reception.

[0002]

2. Description of the Related Art A conventional high-frequency receiving apparatus is intended to secure the receiving performance for both terrestrial broadcasting reception and CATV reception. For example, by controlling the AGC voltage of an AGC circuit inserted between a single superheterodiner tuner and an antenna terminal depending on whether it is a terrestrial broadcast or a CATV, its image receiving performance is ensured.

[0003]

However, in the conventional system, the input of the high-frequency receiver is either a terrestrial broadcast signal or a CATV signal.
The only way to determine and switch to a signal is for the user to know the input signal and do it manually, but this cannot be done automatically.

[0004] It is an object of the present invention to automatically determine whether a high-frequency receiver is connected to a terrestrial broadcast signal or a CATV signal.

[0005]

According to the present invention, there is provided an antenna terminal to which a high-frequency signal is inputted;
A having an AGC control terminal connected to this antenna terminal
A GC circuit, a tuner having a second AGC circuit to which the output of the AGC circuit is connected, a VIF unit to which the output of the tuner is supplied, and an A output from the VIF unit
The AGC circuit and the DC voltage source for maximizing the gain of the tuner and the AGC circuit are switched between the AGC circuit and the AGC circuit.
A switch connected to the circuit and the tuner, a synchronization signal detection circuit to which the output of the VIF is connected, a microcomputer supplied with the synchronization signal detection signal and the AFT voltage from the VIF, and a memory connected to the microcomputer. Configuration. Thereby, it is automatically determined whether the high-frequency receiver is connected to the terrestrial broadcast signal or the CATV signal, and the AGC circuit inserted between the antenna terminal and the tuner is controlled according to the result. The reception performance can be secured at the time of CATV reception.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides an antenna terminal to which a high-frequency signal is input, an AGC circuit having an AGC control terminal connected to the antenna terminal, and an output of the AGC circuit. Is connected to the second AGC
A tuner having a circuit, a VIF section to which the output of the tuner is supplied, an AGC voltage output from the VIF section, and a DC voltage source for maximizing the gain of the AGC circuit and the tuner. A switch to be added to the AGC circuit and the tuner, a synchronization signal detection circuit to which the output of the VIF is connected, a microcomputer supplied with the synchronization signal detection signal and the AFT voltage from the VIF, and a memory connected to the microcomputer Thus, it is determined whether the signal from the antenna terminal is a terrestrial broadcast signal or a CATV signal, and the switch is switched according to the result. Connected to the signal or CATV
It is automatically determined whether the signal is connected to the signal, and the AGC inserted between the antenna terminal and the tuner is automatically determined according to the result.
By controlling the circuit, the reception performance can be ensured at the time of CATV reception.

Further, according to the present invention, an antenna terminal to which a high-frequency signal is input, a tuner to which the antenna terminal is connected, a VIF unit to which an output of the tuner is supplied, and a VIF unit , A microcomputer for inputting the output of the synchronization detection circuit and the AFT voltage from the VIF unit, a memory connected to the microcomputer, and a configuration in which the tuner is controlled by the microcomputer. , A high-frequency signal is a terrestrial signal or a CATV signal. The high-frequency signal is automatically determined whether the high-frequency signal is connected to a terrestrial broadcast signal or a CATV signal. The AGC circuit inserted between the antenna terminal and the tuner is controlled according to the result, and the reception performance can be ensured at the time of CATV reception.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a high-frequency receiving apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an antenna terminal to which a terrestrial broadcast signal or a CATV signal is connected, and the signal is supplied to an AGC circuit 2. A tuner 3 is supplied with a signal from an antenna terminal which is AGC-controlled by the AGC circuit 2, is tuned by a control line connected from a microcomputer 7, is converted into an IF signal, and is supplied to a VIF circuit 4. You. In the VIF circuit 4, the VIF signal is amplified and detected to be a video signal, which is supplied to 9 video signal circuits. The output from the video signal circuit 9 is supplied to and drives 17 CTRs.

The AFT voltage is supplied from the VIF circuit 4 to the microcomputer 7 via the voltage comparators 5 and 6. When a synchronization signal is present from the video signal circuit 9 "
The synchronization signal detection signal which becomes H "is supplied to the microcomputer 7.

On the other hand, the AGC voltage is output from the four VIF circuits and supplied to one terminal of the input of two sets of eight interlocked switches. The other terminals of the inputs of the two switches 8 are supplied with the DC voltage of the video signal circuit 9.

Under the control of the microcomputer 7, when the microcomputer 7 recognizes a terrestrial broadcast, the AGC voltage from the VIF 4 is supplied to the AGC circuit 2 by the first set of switches, and the video signal is supplied to the tuner 3 by the second set of switches. The DC voltage of the circuit 9 is connected.

When the signal is recognized as CATV, the DC voltage of the video signal circuit 9 is supplied to the AGC circuit 2 by the first set of switches and the VIF is supplied to the tuner 3 by the second set of switches.
4 supplies the AGC voltage.

The operation of the high-frequency receiving apparatus configured as described above will be described with reference to the block diagram of FIG. 1, the frequency characteristic of the AFT voltage in FIG. 2, and the flowchart of the program of the microcomputer 7 in FIG.

Now, either a terrestrial broadcast signal or a CATV signal is connected to the antenna terminal 1. When the power of the high-frequency receiving device is turned on, the microcomputer 7 is started from the process-1 in the flowchart of FIG.

First, in process-2, the microcomputer 7 reads from the memory 16 the result of determination as to whether the signal is a terrestrial broadcast signal or a CTAV signal. This memory is either a terrestrial broadcast signal or CTA
There are three possible states of the determination as to whether the signal is a V signal: “not implemented”, “implemented and the result is a terrestrial broadcast signal”, and “implemented and the result is a CATV signal”.

This is determined in processing-3, and if the processing has been completed, the processing goes to processing-19 without any processing and ends. If not performed, the determination process after process-4 is performed.

In addition, even if it has already been implemented,
When the determination process is performed again for reasons such as joining the ATV, the process can be executed from the forced execution of the process -20 when the user instructs the determination process.

In the process-4, among the CATV exclusive channels existing only in the CATV, the 14 (A) channel having the smallest number and having a high probability of having a signal is set as an initial value. In the process-5, channel selection data is sent to the tuner 7 in order to select a channel set so far. In the process-6, when the tuning is completed, the VIF circuit 4
The AFT voltage is supplied to the microcomputer 7 through the signals via the voltage comparators 5 and 6 and the synchronization signal detection signal, and the microcomputer inputs these signals.

Here, the AFT voltage will be described. VI
The frequency characteristic of the AFT voltage from the F circuit 4 is as follows: when the frequency is at the center frequency, the voltage value is the median value E2, as shown in FIG. Deviates from a low value, the voltage value increases. When the frequency further deviates significantly, the voltage value approaches the median value E2.

The AFT voltage, 1a in FIG. 2, is supplied to the minus input terminal of the voltage comparator 5 and the plus input terminal of the voltage comparator 6. Here, +
The power supply voltage E0 is connected to the input terminals by resistors 11, 12, 13
Is applied. Accordingly, the voltage comparator 5 sets “H” when the input voltage is lower than E1, and “H” when the input voltage is higher than E1.
L ”is output.

That is, when the input of 1a in FIG. 2 is applied, the output voltage becomes like 2a in FIG.

Further, a voltage E3 obtained by dividing the power supply voltage E0 by resistors 11, 12, and 13 is applied to a minus input terminal of the voltage comparator 6. Therefore, when the input voltage is higher than E1, "L" is output when the input voltage is lower than "H". That is, when the input of 1a in FIG. 2 is applied, the output voltage is as shown in 3a of FIG.

However, the output of this voltage comparator is an open collector, and the voltage comparator 5
6 are connected to one another, and one load resistor 15 is connected to the 5V power supply 14 from the connection point. That is,
The connected outputs of the voltage comparators 5 and 6 form an AND circuit, and the output of 2a in FIG. 2 and the output of 3a in FIG.
As a result of the logical AND of the outputs of FIG.
It is supplied to the microcomputer 7 as a voltage condition possible signal.

As described above, a signal whose center frequency is "H" is obtained. This width can be changed by changing the constant ratio of the resistors 11, 12, and 13 and changing the voltages of E1 and E3. Choose a width of -50 KHZ.

As described above, the AFT voltage condition enable signal and the synchronization signal detection signal are input in the process-6. Processing-7
Then, the microcomputer 7 determines that the CATV signal is present when both the AFT voltage condition enabling signal and the synchronization signal detection signal are “H”, that is, when the signal frequency is within + -50 KHz and the synchronization signal is present. I do.

If there is a CATV signal, the process proceeds to processing -16, and the memory 16 stores the result “the execution has been completed and the result is the CATV signal”.
Go to the writing 19 and end.

If neither the AFT voltage condition enabling signal nor the synchronizing signal detection signal is present, there is no signal in this channel, it is determined, and the processing shifts to processing -8, where the current channel is the last channel to be determined. Check if there is.

If NO, the process proceeds to a process-9, where 1 is added to the channel number, the 15 (B) channel is set as the next channel to be determined, and the process returns to the process-5.

Thereafter, the same discrimination processing as described above for the 14 (A) channel is performed on the 15 (B) channel.

In this way, if there is a signal on the dedicated channel of CATV, the process of determining CATV is performed up to the last channel if no signal is found.

If no signal is found even when the last channel is reached, the process goes to processing-10, where the terrestrial broadcast signal determination process is performed in a similar manner.

At this time, 14 (UHF) channels, which are the only channels dedicated to terrestrial broadcasting that exist only in terrestrial broadcasting and have the smallest number and high signal probability, are set as initial values.

In this way, it is determined whether the signal is a CATV or terrestrial broadcast signal. If a signal is found in the process-13, the process 16 writes "executed terrestrial broadcast" to the memory 16, and the process goes to the process-19.

Depending on the case, there is a case where it is not possible to make a determination in either case, but in that case, the process goes to the process -17, and a message “Unable to determine” is issued in the process -17, and the memory 1
6 is not rewritten. However, such cases are considered very rare.

It is determined whether the signal connected to the antenna terminal as described above is a terrestrial broadcast signal or a CATV signal. The microcomputer 7 controls the switch 8 according to the result, and when the determination result is the terrestrial broadcast signal, the AGC circuit 2
The AGC voltage from the VIF 4 is connected to the tuner 3 by the first set of switches, and the DC voltage of the video processing circuit 9 is connected to the tuner 3 by the second set of switches.

When the judgment result is a CATV signal, A
An image processing circuit 9 is provided to the GC circuit 2 by a first set of switches.
And the AGC voltage is supplied to the tuner 3 from the VIF 4 by the second set of switches.

In this way, it is automatically determined whether the signal supplied to the antenna terminal is a terrestrial broadcast signal or a CATV signal.

Further, according to this result, the AGC voltage can be connected to the AGC circuit in the case of the terrestrial broadcast signal, and can be connected to the tuner in the case of the CATV signal, so that the receiving performance of both the terrestrial broadcast signal and the CATV signal is ensured. it can.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing a high-frequency receiving apparatus according to one embodiment of the present invention.

In FIG. 4, reference numeral 31 denotes an antenna terminal to which a terrestrial broadcast signal or a CATV signal is connected.
Reference numeral 2 denotes a tuner. A signal supplied with a signal from an antenna terminal is selected by a control line connected from a microcomputer 37, converted into an IF signal, and supplied to a VIF circuit 33.

The VIF circuit 33 amplifies and detects the VIF signal to produce a video signal, which is supplied to a video processing circuit 34. The output from the video processing circuit 34 is supplied to the CRT 45 and drives it.

The AFT voltage from the VIF circuit 33 is
The voltage is supplied to the microcomputer 37 via the voltage comparators 35 and 36. A synchronization signal detection signal which becomes “H” when a synchronization signal is present is supplied from the video processing circuit 34 to the microcomputer 37.

The operation of the high-frequency receiving apparatus configured as described above is easier than the first embodiment based on the configuration diagram of FIG. 4, the frequency characteristic of the AFT voltage of FIG. 2, and the program flowchart of the microcomputer 7 of FIG. So that you can understand
It is possible to automatically determine whether the signal is a terrestrial broadcast signal or a CATV signal.

[0046]

According to the present invention, the above structure automatically determines whether the high-frequency receiving device is connected to a terrestrial broadcast signal or a CATV signal, and determines between the antenna terminal and the tuner according to the result. And controls the AGC circuit inserted therein to ensure the reception performance during CATV reception.

[Brief description of the drawings]

FIG. 1 is a block diagram of a high-frequency receiver according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of FIG.

FIG. 3 is a flowchart of FIG. 1;

FIG. 4 is a block diagram of a high-frequency receiver according to a second embodiment of the present invention;

[Explanation of symbols]

 1, 31 Antenna terminal 2 AGC circuit 3, 32 Single superheterodyne tuner 4, 33 VIF circuit 5, 6, 35, 36 Voltage comparator 7, 37 Microcomputer 8 Switch 9, 34 Video processing circuit 10 Power supply voltage E0 11, 12, 13 , 39, 40, 41 Voltage dividing resistor 14, 425V Power supply voltage 15, 43 Load resistor 16, 44 Memory 17, 45 CRT 38 DC power supply E0 1a AFT voltage vs. frequency characteristic 2a AFT output voltage 1 3a AFT output voltage 24a AFT voltage condition possible signal

Claims (2)

[Claims] An AGC circuit having an antenna terminal to which a high-frequency signal is input, an AGC control terminal connected to the antenna terminal, and an output of the AGC circuit are connected.
A tuner having a second AGC circuit, a VIF unit to which the output of the tuner is supplied, an AGC voltage output from the VIF unit, and a DC voltage source that maximizes the AGC circuit and the tuner. Switch to each of the above A
A GC circuit and a switch to be added to the tuner;
The signal from the antenna terminal is transmitted to the terrestrial broadcast by the synchronization signal detection circuit to which the output of the F is connected, the microcomputer supplied with the synchronization signal detection signal and the AFT voltage from the VIF, and the memory connected to the microcomputer. Signal or CAT
A high-frequency signal receiving apparatus which determines whether the signal is a V signal, and switches the switch according to the result. 2. An antenna terminal to which a high-frequency signal is input, a tuner to which the antenna terminal is connected, a VIF unit to which an output of the tuner is supplied, a synchronization detection circuit connected to the VIF unit, A microcomputer that inputs the output of the synchronization detection circuit and the AFT voltage from the VIF unit, a memory connected to the microcomputer, and a configuration in which the tuner is controlled by the microcomputer. A high-frequency signal receiving device that determines whether the signal is a CATV signal.