JP2001309260A - Channel selection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a channel selection device capable of receiving and selecting a signal of wide frequency band. SOLUTION: In the channel section device selecting a desired channel based on a control signal fluctuating the level in the same level range in a plurality of frequency bands, the selection device comprises a signal controller (68) outputting control signals continuously across the plurality of frequency bands, a filter circuit (431) filtering an input signal responding to the control signals from the controller (68). Therefore the desired channel signal can be selected by treating the signal of the wide frequency band as a single continuous signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a channel selection device,
In particular, the present invention relates to a channel selection device for selecting a desired channel from channels arranged in a wide band.

[0002]

2. Description of the Related Art Conventionally, TV broadcasting using satellites has
Broadcasting Satellite (BS)
llite) and a communication satellite (CS: Com)
and broadcasting using communication satellite.

FIG. 5 is a block diagram showing an example of a conventional satellite broadcast receiving system.

[0004] In FIG. 5, a satellite broadcast receiving system includes:
It comprises an antenna 10, a set box 12, and a television 13.

[0005] The antenna 10 receives the radio wave 9 from the satellite and sends it to the set box 12. The radio wave 9 from the satellite
Radio waves from a broadcasting satellite (BS) and a communication satellite (CS) exist. The radio wave of BS has a frequency of 11.7 to 12.2 GH
At z, the radio wave of CS has a frequency of 12.2-12.75G
Hz. Radio waves from the satellite are received by the antenna 10. The radio wave received by the antenna 10 is converted into an electric signal and supplied to the set box 12. The set box 12 receives a radio wave from the antenna 10, performs video or audio processing on the radio wave, and sends the processed radio wave to the television 13. The set box 12 is provided with a tuner 11, and a desired channel is selected by the tuner 11.

Next, the tuner 11 will be described.

FIG. 6 shows a block diagram of an example of a conventional tuner.

[0008] The tuner 11 includes a distributor 3, an RF (Ra)
Dio Frequency) circuit 15, demodulation circuit 1
6. AGC (Automatic Gain Cont)
(Rol) circuit 18 and a digital demodulation circuit 19.

An antenna 10 is connected to an input terminal 14 of the tuner 11, and a received signal from the antenna 10 is input. The input terminal 14 is connected to the distributor 3. The distributor 3 distributes a signal from the antenna 10 to the RF circuit 15 and the external output terminal 4.

The RF circuit 15 converts the signal from the distributor 3 into A
The signal is amplified according to the AGC signal from the GC circuit 18. RF
The signal amplified by the circuit 15 is supplied to a demodulation circuit 16. The demodulation circuit 16 converts the signal from the RF circuit 15 into I ² C
The I / Q signal of the desired signal is demodulated based on the channel selection signal of the bus 7. The signal demodulated by the demodulation circuit 16 is supplied to a digital demodulation circuit 19.

The digital demodulation circuit 19 demodulates a digital signal from the I / Q signal and outputs the signal to the digital output terminal 8. In addition, the I input to the digital demodulation circuit 19
/ Q from the digital signal 19 in accordance with the strength of the / Q signal.
It is supplied to the C circuit 18.

The AGC circuit 18 outputs an AGC signal for making the amplitude of the I / Q signal constant, and sends it to the RF circuit 15 and the demodulation circuit 16.

FIG. 7 shows a configuration diagram of a conventional example of a distributor, an RF circuit, and a demodulation circuit.

The distributor 3 is connected to the input terminal 14, the external output terminal 4, and the RF input terminal 150. Distributor 3 has R
A signal from the antenna is sent to the F input terminal 150.

The RF circuit 15 has an AMP (Amplify)
er) 30. The AMP 30 amplifies the signal from the RF input terminal 150 with a gain according to the AGC signal from the AGC circuit 18.

The demodulation circuit 16 includes mixers 33, 34, 90
° It comprises a phase shifter 35, an oscillator 36, and a control unit 37.

The control section 37 controls the oscillator 36 with a channel selection signal sent from the I ² C bus 7 via the external terminal 17, and the oscillator 36 outputs an oscillation signal having an oscillation frequency corresponding to the selected signal. The output oscillation signal of the oscillator 36 is supplied to a mixer 34 and a 90 ° phase shifter 35. The 90 ° phase shifter 35 shifts the phase of the signal from the oscillator 36 by 90 °.

The mixer 34 mixes the signal oscillated by the oscillator 36 and the signal from the RF circuit 15. The output of the mixer 34 is output as a Q signal.

The mixer 33 mixes the signal from the 90 ° phase shifter 35 and the signal from the RF circuit 15. The output of the mixer 33 is output as an I signal.

[0020]

However, when a wide frequency band signal is received by a conventional tuner,
Since the input power increases, there have been problems such as deterioration of characteristics such as intermodulation distortion in the amplifier and the mixer.

Accordingly, it is an object of the present invention to solve the above-mentioned conventional problems and to provide a channel selecting device capable of receiving signals in a wide frequency band and selecting a channel.

[0022]

According to a first aspect of the present invention, there is provided a tuning apparatus for selecting a desired channel based on a control signal whose level changes within the same level range within a plurality of frequency bands. Signal control means (68) for continuously outputting a control signal over a plurality of frequency bands; and a filter circuit (431) for filtering an input signal according to the control signal of the signal control means (68). It is characterized by.

According to the first aspect of the present invention, the signal control means (68) for outputting a control signal in which the voltage of a plurality of frequency bands changes as a continuous voltage, and the signal control means (6).
By having the filter circuit (431) for filtering the input signal in accordance with the control signal from 8), it is possible to select a desired channel signal using a signal in a wide frequency band as one continuous signal.

According to a second aspect of the present invention, the signal control means (68) reduces the control signal by the voltage conversion circuit (66).
And a booster circuit (65) for boosting a control signal output from the voltage conversion circuit (66) according to the frequency band.

According to the second aspect of the present invention, the signal control means (68) includes a voltage conversion circuit (66) for reducing the voltage of the control signal, and boosts the voltage-converted signal according to the frequency band. By having a booster circuit (65)
Even if the reception frequency band is widened, a signal whose voltage changes depending on the frequency can be converted into one continuous signal.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The tuning apparatus of the present invention is different from the conventional tuning apparatus shown in FIG. 5 only in the tuner.

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

The tuner 40 includes a distributor 53, an RF circuit 43, a demodulation circuit 44, a digital demodulation circuit 45, an AGC
The circuit 46 includes a tuning circuit 51.

The antenna 10 is connected to an input terminal 41 of the tuner 40, and a received signal from the antenna 10 is input. The input terminal 41 is connected to the distributor 53.
The distributor 53 converts the signal from the antenna 10 into the RF circuit 43
And the external output terminal 42.

The RF circuit 43 amplifies the signal from the distributor 53 in accordance with the AGC signal from the AGC circuit 46 and the signal from the tuning circuit 51. The signal amplified by the RF circuit 43 is supplied to a demodulation circuit 44.

The demodulation circuit 44 converts a signal from the RF circuit 43 into an I / C signal of a desired signal based on a channel selection signal on the I ² C bus 49.
Demodulate the Q signal. The signal demodulated by the demodulation circuit 44 is
It is supplied to a digital demodulation circuit 45 and a tuning circuit 51.

The digital demodulation circuit 45 demodulates a digital signal from the I / Q signal and outputs it to a digital output terminal 50. The digital demodulation circuit 45 supplies the I / Q signal to the AGC circuit 46 in accordance with the strength of the I / Q signal.

The tuning circuit 51 adjusts the signal of a wide frequency band supplied from the demodulation circuit 44 and supplies the adjusted signal to the RF circuit 43. The AGC circuit 46 has an I / Q
An AGC signal for making the signal amplitude constant is generated and sent to the RF circuit 43 and the demodulation circuit 44. FIG. 2 shows a configuration diagram of a tuning circuit, an RF circuit, and a demodulation circuit according to one embodiment of the present invention.

The RF circuit 43 includes AMPs 430, 432,
A BPF (Band Pass Filter) 431 is provided.

The RF circuit 43 is connected to the RF input terminal 60, and receives a signal from the distributor 53. The signal from the RF input terminal 60 is supplied to the AMP 430.

The AMP 430 receives the signal from the AGC circuit 46
The amplification factor is controlled by the GC signal so that the amplitude of the I / Q signal is constant, and the signal from the RF input terminal 60 is amplified. The output signal of the AGC circuit 46 is
1 is supplied.

The BPF 431 includes capacitors C1, C2,
C3, variable capacitance diodes 434 to 437, resistor R1,
R2 and coils L1 and L2. The capacitance of the variable capacitance diodes 434 to 437 is controlled according to the voltage of the signal B. The BPF 431 includes the variable capacitance diode 43
The pass frequency band changes according to the change in the capacity of 4 to 437. By controlling the pass frequency band of the BPF 431 to the frequency band of the channel to be tuned by the signal B, a desired channel can be tuned. BPF431
Is supplied to the AMP 432. AMP
432 amplifies the signal from the BPF 431. AMP
The output signal of 432 is sent to the demodulation circuit 44.

The demodulation circuit 44 includes mixers 440, 441,
It comprises a 90 ° phase shifter 442, oscillators 443 and 444, a switch 445, and a control unit 446.

The oscillators 443 and 444 output oscillation signals having an oscillation frequency corresponding to signals from the tank circuits 75 and 77 of the tuning circuit 51. Output oscillation signals from these oscillators are supplied to a switch 445. Switch 445
Are mixers 440 and 441 according to a signal from the control unit 446.
Are switched. Oscillators 443, 44
4 from the mixer 441 or the 90 ° phase shifter 4
42.

The 90 ° phase shifter 442 is connected to the oscillator 44
3 or the phase of the signal from the oscillator 444 is shifted by 90 °.

The mixer 441 includes an oscillator 443 or 444
And a signal from the RF circuit 43 are mixed. The output of the mixer 441 is output as a Q signal. The output signal of the mixer 441 is supplied to the AGC circuit 46.

The mixer 440 includes the 90 ° phase shifter 44
2 and the signal from the RF circuit 43 are mixed. Mixer 440 outputs an I signal.

The control section 446 sends a switch signal to the switch 445 based on a signal from the I ² C bus 49 sent via the external terminal 447. The signal from the control unit 446 is supplied to the input terminal 61. The control unit 446 sends a signal to the control circuit 68.

The tuning circuit 51 includes a control circuit 68 and a resistor R
9, R10, a power supply terminal 73, and tank circuits 75 and 77.

The power supply terminal 73 is connected to the resistor R10,
Power is supplied. The resistor 9 is connected to the resistors R8 and R10 and the tank circuits 75 and 77. Tank circuits 75, 77
Are variable capacitance diodes 76 and 78, a capacitor C4,
C5. The tank circuits 75 and 77 are connected to oscillators 443 and 444 of the demodulation circuit 44. In the tank circuits 75 and 77, the capacitance of the variable capacitance diodes 76 and 78 is varied according to the voltage of the signal A. Oscillation frequencies of the oscillators 443 and 444 of the demodulation circuit 44 change due to changes in the capacitance of the variable capacitance diodes 76 and 78.

The control circuit 68 includes a voltage dividing circuit 66, an output circuit 69, and a boosting circuit 65.

The voltage dividing circuit 66 includes resistors R6 and R7 and a Zener diode 67. Transistor Tr3
The signal A is supplied to the base via the resistor R8, the collector is connected to the power supply terminal 72, and the emitter is connected to the voltage dividing circuit 66. The emitter current of the transistor Tr3 is controlled according to the A signal from the demodulation circuit 44.

The resistors R6 and R7 are connected to the transistor T
It is connected in series between the emitter of r3 and ground. Zener
The diode 67 has an anode connected to the connection point between the resistors R6 and R7, and a cathode connected to the output circuit 69.

The voltage dividing circuit 66 lowers the level of the signal A. The voltage reduced by the voltage dividing circuit 66 is supplied to an output circuit 69 via a Zener diode 67. Zener
The diode 67 is connected to prevent a backflow of the current from the output circuit 69.

The output circuit 69 comprises a resistor R5. The resistor R5 is connected between the control terminal 433 and the ground. The resistor R5 converts the current from the voltage dividing circuit 66 into a voltage and outputs it as a signal B to the control terminal 433. At this time, the voltage of the signal A is reduced to approximately に よ り by the voltage dividing circuit 66 and the output circuit 69.

The booster circuit 65 includes transistors Tr1 and T
r2, resistors R3 and R4, and power supply terminals 70 and 71.

The base of the transistor Tr1 is connected to the input terminal 6
1 and the collector is connected to the power supply terminal 7 via the resistor R3.
0 and the emitter is grounded. Transistor T
The base of r2 is connected to the collector of the transistor Tr1, the collector is connected to the power supply terminal 70, and the emitter is connected to the resistor R4.

The transistor Tr1 turns on when the input terminal 61 goes high. When the transistor Tr1 is turned on, a current flows between the collector and the emitter via the resistor R3. At this time, the transistor Tr2 receives a current from the base and is turned off. When the transistor Tr2 is off, the output circuit 69 is supplied with current from the voltage dividing circuit 66. The output circuit 69 applies to the control terminal 433 a voltage obtained by reducing the signal A to approximately １ ／.

The transistor Tr1 is connected to the input terminal 6
It turns off when 1 goes low. Transistor Tr1
Is turned off, the base of the transistor Tr2 becomes high level, and the transistor Tr2 is turned on. When the transistor Tr2 is turned on, a current is supplied to the output circuit 69 via the resistor R4, and the voltage of the control terminal 433 is boosted. The booster circuit 65 boosts the voltage of the control terminal 433 approximately twice.

FIG. 3 is a diagram showing the relationship between voltage and frequency in the control circuit according to one embodiment of the present invention.

In FIG. 3, (I) shows the A signal from the demodulation circuit 44, (II) shows the relationship between the voltage and frequency in the voltage dividing circuit 66, and (III) shows the B signal supplied to the BPF 431. The relationship between voltage and frequency is shown.

In (I), the voltage of the A signal input from the demodulation circuit 44 changes in the same manner between the lower frequency band between the frequencies f0 and f1 and the upper frequency band between the frequencies f1 and f2. . At the frequency f0 in the lower frequency band, the voltage is 3V, and at the frequency f1, the voltage is 20V. Similarly, at the frequency f1 in the upper frequency band, the voltage is 3 V,
At the frequency f2, the voltage becomes 20V.

In (II), the voltage is divided by the voltage dividing circuit 66. At the frequency f0 in the lower frequency band, the voltage becomes 1.5V, and at the frequency f1, the voltage becomes 10V. At the frequency f1 in the upper frequency band, the voltage becomes 1.5V, and at the frequency f2, the voltage becomes 10V.

In (III), the B signal supplied to the BPF 431 is output from the output circuit 69 at frequencies f1 to f2.
Is boosted. Thereby, the voltage at the frequencies f1 and f2 is boosted to 10V to 20V. Therefore, the frequency f0
The voltage can be continuously varied between f1 and f1 and f2 and f2.

FIG. 4 is a diagram showing frequency characteristics according to one embodiment of the present invention.

In FIG. 4, the BP shown in FIG.
The B signal supplied to F431 has a frequency f at a voltage of 2V.
0 shows the characteristics of a frequency f1 at a voltage of 10V and a frequency f2 at a voltage of 20V. The frequency f1 at a voltage of 10 V is set by a transistor switch in the control circuit 68.
Is switched to the characteristic of the frequency f2 at the voltage of 20V. Thus, the voltages f0 to f2 can be covered with a voltage of 1.5 V to 20 V, and the BPF 431 can be tracked in a wide frequency range.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

[0063]

According to the tuning apparatus of the present invention, a signal control means for outputting a control signal in which voltages in a plurality of frequency bands change as a continuous voltage, and an input according to a control signal from the signal control means. By having a filter circuit for filtering a signal, a desired channel signal can be selected as a signal in a wide frequency band as one continuous signal.

According to the tuning apparatus of the present invention, the signal control means includes a voltage conversion circuit for reducing the voltage of the control signal;
By including the booster circuit that boosts the signal whose voltage has been converted in accordance with the frequency band, a signal whose voltage changes depending on the frequency can be converted into one continuous signal even when the reception frequency band is widened.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of a tuning circuit, an RF circuit, and a demodulation circuit according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between voltage and frequency in a control circuit according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating frequency characteristics according to an embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a conventional satellite broadcast receiving system.

FIG. 6 shows a block diagram of an example of a conventional tuner.

FIG. 7 shows a configuration diagram of a conventional example of an RF circuit and a demodulation circuit.

[Explanation of symbols]

14, 41 input terminal 4, 42 output terminal 5, 52 power supply 7, 49 I ² C bus 9 radio wave 10 antenna 11, 40 tuner 12 set box 13 television 15, 43 RF circuit 16, 44 demodulation circuit 18, 46 AGC circuit 19 , 45 Digital demodulation circuit 431 BPF 430, 432 AMP 51 Tuning circuit 68 Control circuit 66 Voltage divider circuit 69 Output circuit 75, 77 Tank circuit 446 Control unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Noboru Sadai 1601 Sakai, Atsugi-shi, Kanagawa Prefecture F-term in Atsugi Works, Mitsumi Electric Co., Ltd. 5C025 AA23 AA25 DA04 5C064 DA05 5K061 AA10 AA11 BB10 CC08 CC11 CC14 CC52 JJ12 JJ24

Claims (2)

[Claims] 1. A tuning device for selecting a desired channel based on a control signal whose level changes within the same level range within a plurality of frequency bands, wherein the control signal is continuously transmitted over the plurality of frequency bands. And a filter circuit for filtering an input signal in accordance with the control signal of the signal control means. 2. The apparatus according to claim 1, wherein the signal control unit includes a voltage conversion circuit for reducing the control signal, and a boosting circuit for boosting a control signal output from the voltage conversion circuit in accordance with the frequency band. The channel selection device according to claim 1.