KR20080024835A - Input Tuning Circuit of Tuner - Google Patents

Abstract

The present invention relates to an input tuning circuit of a tuner.

The present invention includes a first switch unit and a second switch unit for separating a first band and a second band with respect to a high frequency signal input from an antenna to drive only the first band by tuning only the first band when tuning the first band. In addition, when the second band is tuned, only the second switch unit is driven to tune only the second band, thereby preventing reflection signals and interference by adjacent frequencies when the first or second band is tuned, thereby improving reception sensitivity. It will provide an effect.

Description

Tuner Input Tuning Circuit {CIRCUIT FOR INPUT TUNING OF TUNER}

1 is a block diagram of an input tuning circuit of a conventional tuner.

2 is a circuit diagram of an input tuning circuit of a tuner according to an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

21; Booster 22; Balloon

23; A first band input tuning circuit 24; 2nd band input tuning circuit

25; A first switch unit 26; Low pass filter

27; Second switch unit 28; High pass filter

The present invention relates to an input tuning circuit of a tuner.

In general, an input tuning circuit of a tuner is a device for tuning the high frequency signal band by band in order to tune a desired channel frequency from the received high frequency signal.

The tuner's input tuning circuit includes a booster (11) for amplifying a high frequency signal received from an antenna (ANT), as shown in FIG. A loop through (L / T) for outputting a high frequency signal amplified by the booster (11) to an external device and a balun (BALUN) 12 for separating the reception band; A first band input tuning circuit (13) which is a VHF band for receiving bands of several tens of MMz to hundreds of MMz of the high frequency signal separated from the balloon 12; It consists of a second band input tuning circuit 14, which is a UHF band that receives a few hundred GMz bands from several hundred MMz.

The first band input tuning circuit is divided into a high range and a low range.

In the input tuning circuit of the conventional tuner configured as described above, the high frequency signal input from the antenna ANT is amplified through the booster 11, and the amplified high frequency signal is output to the loop through L / T through the balun 12. In addition, it is output to the first band input tuning circuit 13 and the second band input tuning circuit 14 to be tuned respectively.

However, when tuning the first band for the VHF input tuning or tuning the second band for the UHF input tuning, the high frequency signals input through the balun 12 are received by the received electric field strength and the reflected signal in adjacent frequency bands. There is a problem of causing interference and lowering the reception sensitivity of the tuned band.

The present invention prevents interference between adjacent frequency bands of received high frequency signals.

An input tuning circuit of the tuner of the present invention includes: a booster for amplifying a high frequency signal received from an antenna; A balun separating the high frequency signal amplified by the booster into a loop through and a reception band; A first band input tuning circuit for input tuning a reception band separated from the balun into a first band; A first switch section including a second band input tuning circuit for input tuning to a second band, and outputting a high frequency signal to a first band input tuning circuit when the first band is tuned; A low pass filter for filtering only the low band of the high frequency signal output from the first switch unit and outputting the low band filter to the first band input tuning circuit; A second switch unit for outputting a high frequency signal to a second band input tuning circuit when the second band is tuned; And a high pass filter for filtering only the high range of the high frequency signal output from the second switch unit and outputting the filtered high frequency signal to the second band input tuning circuit.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a detailed circuit diagram of an input tuning circuit of a tuner according to an embodiment of the present invention.

The booster 21 amplifies and outputs a high frequency signal received from the antenna ANT. The booster 21 may be implemented as a resistor, a passive element, and a transistor, an active element.

The balloon 22 is separated into a loop through (L / T) for outputting a high frequency signal amplified by the booster 21 to another external device and a reception band.

The first band input tuning circuit 23 is divided into a high band and a low band input tuning circuit, and the high band input tuning circuit is inputted and tuned only by inputting a high band VHF band from a high frequency signal inputted separately through the balun 22. The low pass input tuning circuit is inputted to tune only the low pass VHF band.

The second band input tuning circuit 24 inputs and tunes only the UHF band from the high frequency signal inputted separately through the balun 22.

The first switch unit 25 is a non-current switch transistor Q1 connected between the balloon 22 and the first band input tuning circuit 23 and turned on when the low signal is input and turned off when the high signal is input. The high frequency signal is inputted when the first band is tuned.

The low pass filter 26 is connected between the first switch section 25 and the first band input tuning circuit 23, and connects the capacitor C1 to a pair of coils L1 and L2 connected in series. It is configured in parallel to filter the low-frequency of 430MHz or less from the high-frequency signal output from the first switch unit 25 is input to the first input tuning circuit (23).

The second switch unit 27 is connected between the balun 22 and the second band input tuning circuit 24 and implemented by a switching diode D1 to output a high frequency signal input during the tuning of the second band. do.

The high pass filter 28 is connected between the second switch section 27 and the second band input tuning circuit 24, and the coil L3 is connected to a pair of capacitors C2 and C3 connected in series. The high frequency signal output from the second switch unit 27 is configured in parallel to filter only a high frequency of 430 MHz or more and is input to the second input tuning circuit 24.

According to the present invention configured as described above, the high frequency signal received from the antenna ANT is amplified by the booster 21 and outputted through the balun 22 to the loop through (L / T) as well as the first and second band input copper. It is output to the inquiry paths 23 and 24.

At this time, when the first band is tuned, a low signal is input from the tuner L / H to the gate terminal of the transistor Q1, which is the first switch unit 25, so that the transistor Q1 is driven on, whereas The switching diode D1 of the switch unit 27 is kept off by the low signal, and the high frequency signal output from the balun 22 is applied to the switching diode D1 of the second switch unit 27. On the other hand, only the band of 430 MHz or less is filtered by the low pass filter 26 through the transistor Q1 and input to the first band input tuning circuit 23.

On the other hand, since the high signal is inputted from the tuner L / H to the gate terminal of the transistor Q1, which is the first switch unit 25, when the second band is tuned, the transistor Q1 is turned off, whereas the second Since the switching diode D1 of the switch unit 27 is maintained in the on state by the high signal, the high frequency signal output from the balun 22 is transmitted by the transistor Q1 of the first switch unit 25. On the other hand, only the band of 430 MHz or more is filtered by the high pass filter 28 through the switching diode D1 to be input to the second band input tuning circuit 24.

As described above, the present invention includes a first switch unit and a second switch unit for separating a first band and a second band from a high frequency signal input from an antenna in an input tuning circuit of a tuner. By driving only one switch unit to tune only the first band, and tuning only the second band by tuning only the second switch when tuning the second band, the reflected signal and interference by adjacent frequencies during the first or second band tuning Since it is to be prevented, it is to provide an effect that can improve the reception sensitivity.

Claims (5)

A tuner comprising a first band input tuning circuit for input tuning to a first band for amplifying a high frequency signal received from an antenna and a second band input tuning circuit for input tuning to a second band, wherein the tuner includes: A first switch unit for outputting a high frequency signal to a first band input tuning circuit; A low pass filter for filtering only the low band of the high frequency signal output from the first switch unit and outputting the low band filter to the first band input tuning circuit; A second switch unit for outputting a high frequency signal to a second band input tuning circuit when the second band is tuned; And a high pass filter for filtering only the high band of the high frequency signal output from the second switch unit and outputting the high band filter to the second band input tuning circuit. The tuner's input tuning circuit of claim 1, wherein the first switch unit is a non-current switch transistor that outputs a high frequency signal when a low signal is input. The low pass filter of claim 1, wherein the low pass filter filters only a low frequency of 430 MHz or less by connecting a capacitor in parallel to a pair of coils connected between the first switch unit and the first band input tuning circuit and connected in series with each other. Tuner input tuning circuit. The tuner's input tuning circuit according to claim 1, wherein the second switch unit comprises a switching diode which outputs a high frequency signal when a high signal is input. 2. The high pass filter of claim 1, wherein the high pass filter is connected between the second switch unit and the second band input tuning circuit, and a coil is connected in parallel to a pair of capacitors connected in series to each other so as to filter only a high frequency of 430 MHz or more. An input tuning circuit of a tuner, characterized in that.

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