KR20060010346A - Input circuit of tuner for broadcast reciver - Google Patents

Abstract

The present invention relates to an input circuit of an over-the-air broadcast receiver tuner capable of satisfying the circuit simplification and band-stopping characteristics by simply adding a band trap function through a modification of the low pass filter circuit. An input circuit of the tuner is connected to the antenna terminal and the ESD circuit unit for discharging the static electricity introduced into the antenna terminal to the ground; And a first signal connected between an output terminal of the ESD circuit unit and a UHF input tuning terminal to receive only a signal having a predetermined frequency band by receiving the received signal of the antenna terminal through the ESD circuit unit, and having a resonant frequency of the UHF and VHF bands. An LC resonant circuit part, a second LC resonant circuit part connected between the first LC resonant circuit part and the VHF input tuning stage and resonating at the center frequency of the VHF band, and a center of the UFH band connected between the second LC resonant circuit part and the ground terminal. And a low pass filter unit including a third LC resonant circuit unit resonating in frequency.

Tuner, Input Circuit, Input Tuning, Low Pass Filter, Band Trap

Description

Input circuit of tuner for over-the-air broadcast receiver             

1 is a circuit diagram showing an input circuit of a conventional tuner for an airwave broadcasting receiver.

2 is a circuit diagram of an input circuit of a conventional tuner for a simplified over-the-air broadcast receiver.

3 is a circuit diagram of an input circuit of a tuner for an over-the-air broadcast receiver according to the present invention.

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

31: ESD circuit

32: low pass filter

33: band trap part

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuner provided in a receiver for selectively receiving over-the-air broadcast signals transmitted on a wireless carrier, and more particularly, to an input circuit of a tuner connected to an antenna for filtering and receiving only signals in a broadcast band. .

With the development of display apparatuses such as televisions capable of reproducing images and audio through predetermined screens and speakers, various types of services providing video and audio such as over-the-air broadcasting, cable broadcasting and satellite broadcasting have been provided.

In order to receive such a broadcast signal and reproduce it through a television, a separate carrier for receiving a carrier band of the broadcast signal, restoring a video and audio signal from the carrier, and converting it into one channel signal of the reception band of the television is transmitted. A device is required and such a device is generally called a receiver or set-top box, hereinafter referred to as a receiver.

In addition, since each broadcast service has a different frequency band for transmitting a broadcast signal and a processing method for video and audio signals, the receivers have slightly different circuit configurations, but signals in a selected channel band among the broadcast signals are common. It is provided with a tuner (tuner) to extract the frequency conversion of the baseband signal. The tuner is composed of an input circuit part for removing high frequency band noise out of a broadcast band, an input tuning part for tuning a selected channel signal, an amplifier for amplifying the tuned channel signal, and an intermediate portion of the amplified signal. And a frequency converting section for frequency down to the frequency band or baseband, and a filter circuit section for filtering the signal output from the frequency converting section.

1 illustrates an input circuit configuration of a tuner provided in an over-the-air broadcast receiver using a UHF band and a VHF band as a channel band for transmitting a broadcast signal. In general, an input terminal of the tuner is directly connected to an antenna and is provided through an antenna. ESD circuit 11 for discharging the current by static electricity to prevent the inflow of static electricity, low pass filter 12 connected to the antenna through the ESD circuit 11 to remove the high frequency components outside the UHF, VHF band and And a band pass filter 13 for band-passing only the VHF band among the high frequency signals output from the low pass filter 12.

The tuner further comprises a switching circuit for selectively connecting the low pass filter 12 and the band pass filter 13 of the input stage to a UHF input tuning stage or a VHF input tuning stage. The switching circuit may be implemented as switching diodes D11 and D12 that are switched on / off according to an externally applied control voltage Vc.

The low pass filter 12 filters the high frequency region signals out of the band that may cause interference with noise in the broadcasting band (VHF band + UHF band) and applies them to the UHF input tuning stage or the VHF input tuning stage. In addition, the band pass filter 13 band-passes only the VHF band signal between the low pass filter 12 and the VHF input tuning stage in order to prevent the band pass filter 13 from flowing into the VHF input tuning stage of the UHF band signal. To act.

By the way, in recent years, in accordance with the trend of integration and miniaturization between components, a circuit has been simplified for the tuner, and the circuit configuration of the input terminal has been simplified as shown in FIG.

Referring to FIG. 2, the simplified conventional tuner input circuit includes an ESD circuit 21 and an ESD circuit 21 for removing the band pass filter 13 to discharge static electricity flowing through an antenna terminal. It consists of a low pass filter 22 that receives the high frequency signal received by the antenna through the high-frequency components out of the UHF, VHF band of the signal to apply to the UHF input tuning stage or VHF input tuning stage.

The input circuit of the tuner shown in FIG. 2 can simplify the circuit configuration, but has a problem in that the band rejection characteristic is weakened because band pass filtering is not performed for the VHF band. Therefore, there is a need for a new configuration that can simplify and simplify the circuit while satisfying the required band rejection characteristics.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned conventional requirements, and an object thereof is to add a band trap function to a low pass filter circuit, thereby inputting a tuner for an over-the-air broadcast receiver that can satisfy the circuit simplification and band blocking characteristics. To provide a circuit.

As a constituent means for achieving the above object of the present invention, the present invention provides an input circuit of a tuner for a terrestrial broadcast receiver,

An ESD circuit unit connected to the antenna terminal and discharging the electrostatic component introduced into the antenna terminal to ground; And

A first LC connected between an output terminal of the ESD circuit unit and a UHF input tuning stage to receive only a signal having a predetermined frequency band through the received signal of the antenna terminal through the ESD circuit unit, and having a resonant frequency in the UHF and VHF bands; A resonant circuit part, a second LC resonant circuit part connected between the first LC resonant circuit part and the VHF input tuning stage and resonating at the center frequency of the VHF band, and a center frequency of the UFH band connected between the second LC resonant circuit part and the ground terminal; And a low pass filter including a third LC resonant circuit.

Hereinafter, a configuration and an operation of an input circuit of a tuner for an airwave broadcasting receiver according to the present invention will be described with reference to the accompanying drawings.

3 is a circuit diagram of an input circuit of a tuner for an over-the-air broadcast receiver according to the present invention. As illustrated, the tuner input circuit of the present invention is connected to an antenna terminal ANT and is introduced into the antenna terminal ANT. An ESD circuit section 31 for discharging the component to ground and an output terminal of the ESD circuit section 31 to receive only a signal of a predetermined frequency band by receiving a received signal of the antenna terminal ANT through the ESD circuit section 31. And a first LC resonant circuit portion connected between the UHF input tuning stage and the resonant frequency of the UHF and VHF bands, and connected between the first LC resonant circuit portion and the VHF input tuning stage and resonating at the center frequency of the VHF band. And a low pass filter unit 32 including a 2LC resonant circuit unit and a third LC resonant circuit unit connected between the second LC resonant circuit unit and a ground terminal and resonating at the center frequency of the UFH band.

The ESD circuit 31 is implemented with an inductor L31 connected between the ground terminal and the antenna terminal ANT, and two capacitors C31 and C32 connected in series with the antenna terminal ANT. Accordingly, the low frequency electrostatic components introduced along the antenna terminal ANT are bypassed to the ground through the inductor L31, and the high frequency components carrying the broadcast signal are passed to the low pass filter unit 32 through the capacitors C31 and C32. Delivered.

가 되며, 여기서 제1LC공진회로부는 UHF, VHF 대역의 중심주파수에 공진하도록 상기 인덕턴스 L과 캐패시턴스 C가 설정되며, 입력된 고주파 수신 신호에서 UHF, VHF 대역의 고주파신호는 통과시키고, 그 보다 높은 대역의 신호는 저지시킨다.The first LC resonant circuit of the low pass filter 32 includes an inductor L32 and a capacitor C33 connected in parallel between the capacitor C32 and the UHF input tuning stage of the ESD circuit 31. . The inductor L32 and the capacitor C33 resonate in parallel. When the inductance of the inductor L32 is referred to as L and the capacitance of the capacitor C33 is referred to as C, the resonance frequency thereof is

Here, the first LC resonant circuit portion is set to the inductance L and capacitance C so as to resonate with the center frequency of the UHF, VHF band, and pass the high-frequency signal of the UHF, VHF band in the input high-frequency received signal, the higher band Signal is blocked.

A switching diode D31 is provided between the first LC resonant circuit parts L32 and C33 and the UHF input tuning stage, and the switching diode D31 is turned on when a channel of the UHF band is selected, and the first resonant circuit part The high frequency signal of the UHF band passing through L32 and C33 is applied to the UHF input tuning stage, and is turned off when the channel of the VHF band is selected to block the inflow of the high frequency signal to the UHF tuning stage.

The second LC resonant circuit of the low pass filter 32 includes an inductor L33 and a capacitor C34 connected in parallel between the contacts of the parallel inductor L32 and the capacitor C33 and the VHF input tuning stage. Is implemented.

The inductor L33 and the capacitor C34 of the second LC resonant circuit part are set to resonate at the center frequency of the VHF band, and the signal of the VHF band of the signals passed through the inductor L32 and the capacitor C33 of the first LC resonant circuit part. To VHF input tuning stage.

In addition, the third LC resonant circuit part of the low pass filter 32 is connected to the contact point of the inductor L33 and the capacitor C34 of the second LC resonant circuit part and the inductor L34 and the capacitor C35 and the inductor L34 ) And a capacitor C36 which connect the capacitor C35 to a ground terminal in common.

The inductor L34 and the capacitor C35 of the third LC resonant circuit part tune to a high frequency adjacent frequency of the UHF band to attenuate the frequency signal.

The combination of the first, second, and three LC resonant circuit parts implements a low pass filter characteristic, and band-stops a high frequency signal higher than the UHF band, while the UHF band signal is the UHF input tuning stage, and the VHF band signal is the VHF input tuning. Deliver to stage. In addition, the second and third resonant circuit part regions 33 included in the low pass filter part 32 serve as a band trap for the VHF out-of-band signal.

As described above, the input circuit of the tuner according to the present invention is further connected in parallel to the inductors L23 and L24 of the low pass filter 22 in the conventional simplified circuit configuration shown in FIG. In this case, the IF trap and the band trap function can be realized through a simple circuit modification of the existing low pass filter without a separate band trap circuit configuration. Therefore, the tuner's input circuit according to the present invention makes it possible to simplify the circuit while satisfying the bandstop characteristic.

FIG. 4 compares the frequency characteristics of the tuner input circuit according to the present invention with a conventional tuner input circuit, and the conventional tuner input circuit is according to the configuration shown in FIG. 2.

The signal measurement of FIG. 4 was made at the output side of the VHF tuning stage.

Referring to the graph of FIG. 4, the marker marked as ◇ 1 indicates attenuation (dB) characteristic of 455 MHz, and it can be seen that the attenuation characteristic is further improved by 10 dB or more on the high frequency band side of 500 MHz or more. .

As described above, the present invention exhibits an excellent effect of maintaining the band blocking characteristic at the input terminal of the tuner at a predetermined level or more while satisfying the requirements for simplifying the circuit.

Claims (4)

An ESD circuit unit connected to the antenna terminal and discharging the electrostatic component introduced into the antenna terminal to ground; And A first LC connected between an output terminal of the ESD circuit unit and a UHF input tuning stage to receive only a signal having a predetermined frequency band through the received signal of the antenna terminal through the ESD circuit unit, and having a resonant frequency in the UHF and VHF bands; A resonant circuit part, a second LC resonant circuit part connected between the first LC resonant circuit part and the VHF input tuning stage and resonating to the center frequency of the VHF band, and a center frequency of the UFH band connected between the second LC resonant circuit part and the ground terminal; An input circuit of a tuner for an over-the-air broadcast receiver, comprising: a low pass filter unit comprising a third LC resonant circuit unit resonating with the second LC resonance circuit unit. The method of claim 1, And the first LC resonant circuit part comprises an inductor (L32) and a capacitor (C33) provided in parallel between the signal output terminal and the UHF input tuning terminal of the ESD circuit unit. The method of claim 1, And the second LC resonant circuit part comprises an inductor (L33) and a capacitor (C34) configured to be connected in parallel between the output side of the first LC resonant circuit part and the VHF input tuning stage. The method of claim 1, The third LC resonant circuit part includes an inductor L34 and a capacitor C35 connected to the second LC resonant circuit part at the same time in parallel, and a capacitor C36 provided between the contact point of the inductor L34 and the capacitor C35 and the ground. An input circuit of a tuner for an over-the-air broadcast receiver, comprising: a tuner;

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