JP3089486B2 - Tuner for BS / UV, CS / UV - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a BS and a BS / BS provided with a circuit for blocking a local oscillation signal leaking from the signal input terminals of the BS and CS tuners to the antenna side. It relates to a tuner for both UV and CS / UV.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional BS / UV shared tuner. In the figure, A is a PLL (pulse loc
ked loop) circuit, B is VCO (voltage controlledoscila)
tor) circuit, C is a switch, D is UHF, VHF (hereinafter U
1st mixer, E is RF amplifier, F is UV
Input filter, G is UV input terminal, H is BS mixer,
I is FM demodulation circuit, J is BS1st IF amplifier, K is B
S is an S input filter, L is a BS input terminal, M is a UV2nd mixer, and N is a UV2nd IF amplifier. The UV signal input from the UV input terminal G is amplified by the RF amplifier E only through the channel signal received by the UV input filter F, and then is amplified by the UV1st mixer D to fLO1-fUV1.
= FUV2. Then, the frequency is converted to fUV3 by the UV2nd mixer M, amplified by the UV2nd IF amplifier N, and output as an IF signal. Also B
The S signal passes only through the BS frequency band by the BS input filter K, is amplified by the BS1st IF amplifier J, is frequency-converted by the BS mixer H to fLO1−fBS1 = fBS2, and becomes a detection output through the FM demodulation circuit I. Where f
LO1 is controlled by the PLL circuit A and the VCO circuit B so that fUV2 is always constant in each channel, and fLO1 is switched by a switch so that fUV1 is mixed with UV when receiving UV and fBS1 when BS is received. .

[0003]

When receiving a UV channel, a UV signal is input to a UV mixer D, and when receiving a BS channel, a BS signal is input to a BS mixer H. However, with a conventional BS / UV shared tuner, fUV2
Since 965.25MHz is set, the local oscillation frequency fLO
1 is about 1.0 to 1.7GHz when receiving UV channel.
Since the signal enters the band of about 1.0 to 1.4 GHz of the first IF frequency of S, the leakage signal of the local oscillation frequency fLO1
Mixer H, 1st IF amplifier J, BS input filter K
, Is output from the BS input terminal L as a disturbing signal. Generally, the level of the signal of the local oscillation frequency fLO1 before inputting to the BS mixer H is as high as about 10 dBm or more. Even if switching is performed by a diode or a transistor, the local oscillation signal at the time of UV reception is transmitted through the internal capacitance of the diode or the transistor.
It is detected from the S input terminal L. Therefore, in the case where the BS is jointly received by multiple households, when one household is receiving the UV channel, the BS input terminal L of the tuner is used.
The local oscillation signal leaking out of the home will interfere with other households receiving the BS channel.

[0004] It is an object of the present invention to overcome the disadvantages of the prior art.
An object of the present invention is to provide a BS / UV and CS / UV shared tuner that reduces a leakage level of a local oscillation signal output from an S input terminal L.

[0005]

SUMMARY OF THE INVENTION A BS / UV shared tuner according to the present invention has a terminal for inputting a signal received by a BS (Satellite Broadcasting) antenna and a terminal for inputting UHF and VHF signals in the same housing. A switching diode is provided between the BS input filter and the BS1st IF amplifier to prevent a leakage signal from a local oscillator in the housing when receiving VHF or UHF.

Further, a terminal for inputting a signal received by a CS (communication satellite) antenna and a terminal for inputting UHF and VHF signals are provided in the same housing, and a CS input filter and a CS1s are provided.
A switching diode is provided between the tIF amplifiers and V
It is configured to prevent a leakage signal from a local oscillator in the housing when receiving HF or UHF.

[0007]

According to the circuit of the present invention, as shown in FIG.
Switch C between input filter K and 1st IF amplifier J
, When receiving the UV channel, the internal capacitance of the diode of the switch 1, the BS mixer H, the 1st
The leakage of the local oscillation signal is dropped to the ground via the IF amplifier J. When receiving a BS channel, the BS input terminal L
The switch C is changed so that the signal from the receiver can be input to the BS mixer H through the BS input filter K and the first IF amplifier J. By doing so, it is possible to reduce the level of leakage of the local oscillation signal from the BS input terminal L that occurs during UV reception without affecting BS reception.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of a BS / UV and CS / UV shared tuner of the present invention (FIG. 1 shows only BS / UV, but the same applies to CS / UV). In this figure, the same parts as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, BS input filters K and 1s
By putting switch C between tIF amplifier J, UV
At the time of channel reception, leakage of the local oscillation signal is grounded via the internal capacitance 1 of the diode of the switch, the BS mixer H, and the first IF amplifier J.

When receiving a BS channel, a signal from the BS input terminal L is converted to a BS input filter K, 1st IF
The switch C is changed so that the signal can be input to the BS mixer H through the amplifier J. As a result, there is no influence upon receiving the BS.

FIG. 2 is a circuit diagram of a BS / UV shared tuner showing an embodiment of the present invention. In FIG.
8, 15, 16, 19, 20 are resistors, 2, 6, 9 are capacitors, 12, 13 are coils, 3, 7, 17, 18 are switching diodes, 10, 11 are mixer diodes, and 14 is a balun. . At the time of UV reception, the switching diodes 7 and 18 are turned on by applying the voltage VC to the terminals 22 and 23, and
The leakage of the local oscillation signal of V is caused by the internal capacitance of the diode 1, B
Via the S mixer H, it falls to ground via the first IF amplifier J, the capacitor 9, the switching diode 7, and the capacitor 6. On the other hand, at the time of BS reception, the switching diodes 3 and 17 are turned on by applying the voltage VC to the terminals 21 and 24, and the input signal from the BS input terminal L is passed through the capacitor 2, the switching diode 3, the capacitor 9, and the first IF amplifier J. Then, the frequency of the local oscillation signal passed through the switching diode 17 is converted by the BS mixer H and then input to the FM demodulation circuit. CS / U
The same applies to the case of the V shared tuner, so that the description is omitted.

[0013]

According to the present invention, BS / UV, CS / UV
In the shared tuner, since the local oscillation signal of the UV channel falls within the band of the BS channel, other receivers
If an S channel is being received, it will interfere there. However, according to the present invention, it is possible to input the BS signal with almost no attenuation when receiving the BS without disturbing other receivers even when receiving the UV channel. Becomes

As described above, the double super system in which frequency conversion is performed twice by UV and the single super system in which frequency conversion is performed once are adopted in the BS / UV shared tuner. By changing the BS to CS in the description, the present invention can be applied to a CS / UV shared tuner, and its practical effect is great.

[Brief description of the drawings]

FIG. 1 shows BS / UV, CS /
It is a block diagram of a UV common tuner.

FIG. 2 is a circuit diagram of a BS / UV and CS / UV shared tuner of the present invention.

FIG. 3 is a block diagram of a conventional BS / UV shared tuner.

[Explanation of symbols]

1: Internal capacitance of diode, 2, 6, 9: Capacitor, 3, 7, 17, 18: Switching diode,
4, 5, 8, 15, 16, 19, 20 ... resistor, 10, 11 ... mixer diode, 12, 13 ... coil, 14 ... balun,
21, 22, 23, 24 ... terminals.

Claims (3)

(57) [Claims] 1. A terminal for inputting a signal received by a BS (Satellite Broadcasting) antenna and a terminal for inputting UHF and VHF signals in the same housing, a BS input filter and a BS1stI.
A switching diode is provided between the F amplifiers and VHF
A BS / UV shared tuner characterized in that a leakage signal from a local oscillator in a housing is blocked when UHF is received. 2. A terminal for inputting a signal received by a CS (communication satellite) antenna and a terminal for inputting UHF and VHF signals in the same housing, and a CS input filter and a CS1stI.
A switching diode is provided between the F amplifiers and VHF
Alternatively, a CS / UV shared tuner characterized in that a leakage signal from a local oscillator in a housing is blocked when UHF is received. 3. A switch circuit between a BS or CS input filter and a BS or CS 1st IF amplifier, comprising:
As a circuit for passing the S or CS signal using a switching diode, the output of the BS input filter or CS input filter circuit is connected to one terminal of a capacitor, and the other terminal of the capacitor is connected to the other terminal of the capacitor when receiving BS or CS.
While the anode side of the switching diode to be connected to N is connected, the anode side is connected to one terminal of a resistor, and the other terminal of the resistor is supplied with a voltage when receiving BS or CS, and when receiving UHF or VHF. Mixer, 1
As a circuit for dropping the local oscillation signal leaking through the stIF amplifier, one terminal of a resistor and one terminal of a capacitor are connected to the anode side of the switching diode, and the other terminal of the resistor is used when receiving UHF and VHF. The voltage is applied, the other terminal of the capacitor is grounded, and the cathode side of the switching diode that turns on when receiving a BS or CS signal is connected to the cathode side of the switching diode that turns on when receiving UHF or VHF. 1stI through the capacitor
3. The tuner for BS / UV and CS / UV according to claim 1, wherein the tuner is connected to an F amplifier.