JPS6047508A - Television receiver - Google Patents

Abstract

PURPOSE:To improve the ability to exclude the disturbance of an unnecessary signal due to an increase in the number of CAT channels by interposing a filter which is switched to a low or high band between an antenna signal input terminal and an electronic tuner. CONSTITUTION:The filter 4 which is switched in response with the DC driving signal from a low/high band switching circuit is interposed between the antenna terminal plate 1 and electronic tuner 2. The filter 4 is impressed with a positive voltage in lowband reception and a positive voltage in high-band reception, and diodes D1-D5 turn on or off according to those voltages to realize a filter function.

Description

[Detailed Description of the Invention] Concerning the image quality 0 The configuration of the conventional example and its problems With the development and spread of CATV mainly in the United States,
The number of television receivers capable of receiving 0ATV is increasing as well.

Further, in many cases, conventional television receivers also receive television channels using a CATV signal superimposed signal. In such a case, as the number of ATV channels increases, cross-modulation and beat disturbance due to non-linear distortion in the high-frequency amplification and mixing elements of the TV tuner become more problematic than before.

FIG. 1 shows the configuration of an input circuit of a conventional television receiver. A television signal is applied from an antenna input terminal to an electronic tuner 2 via an antenna terminal board 1. The electronic tuning tuner 2 switches the reception frequency between low band and high band according to the frequency of the reception channel, and receives the desired channel using a variable capacitance diode.
The signal is converted to an intermediate frequency and input to the intermediate frequency amplification circuit 3.

In this case, for example, as the number of CATV reception channels increases, the number of signal inputs to the electronic tuner increases, and there is a risk that the above-mentioned cross-modulation and beat disturbance may occur.

OBJECTS OF THE INVENTION The present invention solves these conventional drawbacks, and aims to eliminate cross modulation and beat disturbance due to nonlinear distortion in high frequency amplification and mixing elements.

3.°-mi - Structure of the Invention In order to achieve this object, the present invention provides a switch between the antenna signal input terminal and the electronic tuning tuner in conjunction with the high band/low band switching control voltage of the electronic tuning tuner. An R-wave device is inserted and connected to attenuate signals other than the receiving channel.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows an input circuit section of a television receiver according to an embodiment of the present invention.

In FIG. 2, the antenna terminal board 1 and the electronic tuning tuner 2 are exactly the same as the conventional system, but the antenna terminal board 1
and the electronic tuning tuner 1, there is a stream wave generator 4 which is switched in conjunction with the DC drive signal from the low band and high band switching circuit.
is inserted and connected. An example of this sawnami device 4 is shown in the third example.
As shown in the figure.

C1, C4 are DC blocking capacitors, C2, 03, O
s.

C6 is a capacitor, L1 to L4 are inductances, C7
is a capacitor for high frequency grounding, D1 to D6 are high frequency switch knob diodes, R1-R5 are DC bias resistors for switching diodes, Bs is a terminal for switching the low band and high band of the electronic tuning tuner, and when receiving low band, one voltage, During high band reception, ten power supplies are applied, and the diodes D1 to D5 are turned on or off depending on the respective voltages, forming a filter circuit.

FIGS. 4a and 4b show operational equivalent circuits for low band reception and high band reception, respectively.

During low band reception, the diode D1. D4, Ds
.

D6 is off, diode D2. D3 is turned on, and the inductance L1. L2. A low-pass filter is formed by L3 and capacitors C2 and C5, and the signal can be attenuated in the high frequency range. During high band reception, diodes D+, D4, Ds, and D6 are on, and diodes D2... D3 is turned off and capacitor c5. c6 and inductance L1. A bypass filter consisting of L5 and L4 is formed, and signals are attenuated in the low band frequency region. The above contents are shown in the attenuation characteristics shown in FIG.

Effects of the Invention As described above, according to the present invention, 0ATV channel 6
Even if the number of channels increases, the nonlinear distortion generated in the tuner can be significantly improved. In addition, since the band switch power supply for the tuner is shared, by adding a simple connection terminal to the television receiver, it is possible to install an optional stream wave device, and even with a conventional television receiver, 0ATV It is also possible to improve the ability to eliminate interference from unnecessary signals as channels increase.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of an input circuit section of a conventional television receiver, FIG. 2 is a block circuit diagram of an input circuit section of a television receiver according to an embodiment of the present invention, and FIG. 3 is a block circuit diagram of the input circuit section of a television receiver according to an embodiment of the present invention. Figures 4a and b are equivalent circuit diagrams of the same r-wave transmitter during low-band reception and high-band reception, and Figure 6 is an attenuation characteristic diagram of the same r-wave transmitter. be. 1... Antenna terminal board, 2... Old electronic tuning tuner, 4... R wave device. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (1)

[Claims] A television receiver in which an R-wave device is inserted and connected between an antenna signal input terminal and an electronic tuning tuner to attenuate signals other than the receiving channel by switching in conjunction with the high band/low band switching control voltage of the electronic tuning tuner.