KR950006853Y1 - Wide range receiving circuit - Google Patents

Abstract

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Description

Wideband receiver circuit

1 is a block diagram of the present invention.

* Explanation of symbols for main parts of the drawings

1: Attenuator 2, 3, 16, 18: 1st-4th band filter

4, 6, 13: 1st-3rd switching unit 5, 9, 12, 14, 17: 1st-5th amplifier

7: high pass filter 8: varactor filter

10: UHF Oscillator 11: VHF Oscillator

15, 19: first-second mixer 20: oscillator

21: demodulator 22: sound trap

23: low pass filter 24: sound detector

25: AGC 26: PLL

The present invention relates to a television signal tuning and an RF (Radio Frequency) signal processing circuit in a video signal processing system, and in particular, a wide band capable of tuning a broadcast frequency of a desired channel using a dual double conversion method. It relates to a receiving circuit.

In general, in order to select a signal of a desired channel frequency in a video signal processing system such as a TV or VCR, in the conventional case, the following scheme was taken.

That is, the RF TV tuner receives the RF TV signal, tracks the corresponding channel band by driving a PLL (Phase Locked Loop), and then tunes the broadcasting frequency of the desired channel, but the intermediate frequency of the heterodyne method is: Hereinafter referred to as IF) conversion method.

However, the above-described method receives the RF TV signal, tunes the frequency of the desired channel, and performs one frequency conversion to directly down-convert to the 45 MHz IF signal. Accordingly, the rejection of these signals has a disadvantage in that the performance of the tuner has a great effect.

That is, if the output IF signal is referred to as f _IF , the local oscillation frequency is referred to as f _LO , and the input signal is fc, the output IF signal may be expressed as in Equation 1 below.

f _IF = f _LO -f _C ... … (One)

If it is assumed that the frequency f _IM of the image component generated here is represented by an equation, it may be expressed as in Equation 2 below.

f _IM = f _C ± 2f _IF ... … (2)

It is well known that when the component of the f _IF frequency, which is an image component, interferes with the input terminal, it acts as a disturbing signal to the channel tuned signal and degrades TV quality.

Therefore, the need for technology development that does not affect the TV band of these image components has emerged.

Accordingly, an object of the present invention is to provide a wideband receiver circuit employing a dual intermediate frequency conversion method for up-converting a TV RF signal to a frequency higher than the TV band frequency and then converting the TV RF signal to an intermediate frequency.

Hereinafter, with reference to the accompanying drawings of the present invention.

1 is a block diagram of the present invention, in which an attenuator 1 attenuates and outputs an RF TV signal received from an antenna 27 under predetermined control, and only a VHF low pass signal is output from the output signal of the attenuator 1. A first band filter 2 for filtering, a second band filter 3 for filtering only the VHF high-band signal from the attenuator 1 output signal, and an output signal for the first and second band filters 2, 3 A first switching unit 4 for selectively outputting the first signal, a first amplifier 5 for amplifying the output signal of the first switching unit 4, and a channel selection signal to drive a phase-locked loop. A PLL (26) for oscillating a frequency, a high pass filter (7) for filtering only UHF signals from the attenuator (1) output signal, and a UHF signal output from the output of the high pass filter (7) A varactor filter 8 for selecting a desired channel according to the control state of the PLL 26, and the barrel A second amplifier 9 for amplifying the output of the filter 8, a second switching unit 6 for selectively outputting the output signals of the first and second amplifiers 5 and 9, and the PLL unit 26. A UHF oscillator 10 for inputting an output signal to generate a UHF IF signal, a VHF oscillator 11 for inputting an output signal of the PLL unit 26 to generate a VHF IF signal, and an output of the UHF oscillator 10. A third amplifier 12 for selectively amplifying the third amplifier; a third switching unit 13 for selectively outputting the third amplifier 12 output signal and the output of the VHF oscillator 11; and the third switching unit 13; A first mixer for mixing a signal output from the fourth amplifier 14 for amplifying an output signal and the output from the second switching unit 6 and the fourth amplifier 14 to generate a first IF signal ( 15) a third band filter 16 for inputting an output signal of the first mixer 15 to remove adjacent channels and image components, and outputting the third band filter 16; The oscillator 20 outputs the fifth amplifier 17 for amplifying the output, the fourth band filter 18 for re-filtering the output signal of the fifth amplifier 17, and the output of the fourth band filter 18. A second mixer 19 for generating a second IF signal by mixing with a predetermined frequency signal generated, a demodulator 21 for demodulating a second IF signal output from the second mixer 19, and the demodulator (21) a sound trap 22 for removing sound components from an output signal, a low pass filter 23 for inputting an output signal of the sound trap 22 and filtering only low-pass components to output a composite video signal; A sound detector 24 for detecting and outputting a sound signal from the output signal of the demodulator 21, and an AGC 25 for controlling the attenuator 1 by automatically adjusting the gain of the output signal of the demodulator 21. do.

Based on the above-described configuration will be described the present invention in detail.

The RF TV signal input from the antenna 27 is attenuated by the attenuator 1 operating under the control of the AGC 25.

The first and second band filters 2 and 3 which input the output signal of the attenuator 1 select the desired channel by filtering the VHF low pass signal and the VHF high pass signal, respectively, and output the selected channel to the first switching unit 4.

The first switching unit 4 selects one of the outputs of the two filters 2 and 3 as a pin diode switch and outputs the same to the first amplifier 5.

On the other hand, the attenuator 1 output signal is also input to the high pass filter 7 to remove the VHF component.

Therefore, the UHF component outputted from the high pass filter 7 is inputted to the varactor filter 8, which is controlled by the PLL section 26 which inputs the channel selection signal to the desired channel. Select and output to the second amplifier (9).

The VHF RF signal amplified by the first amplifier 5 and the UHF RF signal amplified by the second amplifier 9 are input to the second switching unit 6, and the second switching unit 6 is Optionally output the UHF or VHF RF signal according to the user's choice.

On the other hand, the PLL unit 26 output signal is supplied to the UHF oscillator 10 and the VHF oscillator 11 to control the respective IF component generation operation.

The first IF component output from the UHF oscillator 10 is buffered in the third amplifier 12 and then supplied to the third switching unit 13, and the IF component output from the VHF oscillator 11 is left as it is. The third switching unit 13 is supplied.

In this case, the third switching unit 13 selectively outputs one of the UHF or VHF IF components as a pin diode switch.

The UHF or VHF primary IF component signal output from the third switching unit 13 is input to the fourth amplifier 14, amplified and supplied to the first mixer 15, and then supplied to the second switching unit 6. It is mixed with the VHF or UHF RF signal output from.

When the output signal of the first mixing unit 15 is a primary IF signal, the primary IF signal is input to the third band filter 16 to remove adjacent channels and image components, and then the fifth amplifier 17. A predetermined amplified signal at < RTI ID = 0.0 > 4 < / RTI > then the output signal of the fourth band filter 18 is mixed at the second mixer 19 with the signal generated at the oscillator 20.

When the output signal of the second mixer 19 is a secondary IF signal, the secondary IF signal is demodulated by a demodulator 21 and then passed through a sound trap 22 to a low pass filter 23. By supplying only the low frequency components from which sound components have been removed, a composite video signal is generated.

In addition, the demodulator 21 output signal is supplied to the sound detector 24 to detect and output a sound signal.

In addition, the demodulator 21 output is supplied to the aforementioned AGC 25 to automatically adjust the gain.

As described above, in selecting a broadcasting frequency of a desired channel by receiving a TV RF signal, a dual intermediate frequency conversion method is adopted, so that image components do not affect the TV band, thereby improving image quality.

Claims (1)

In the video signal processing system, an attenuator (1) for attenuating and outputting an RF TV signal received from the antenna (27) under predetermined control, and a VHF low pass signal and a VHF high pass signal from the attenuator (1) output signal. The VHF signal detection unit (A) for filtering and selectively amplifying and selectively amplifying the PH signal, and the PLL (26) for oscillating the frequency of the design by inputting a channel selection signal to drive a phase-locked loop, and the attenuator (1) as an output signal. UHF signal detection unit (B) for filtering a UHF signal only to select and amplify a desired channel according to the control state of the PLL (26), and is output from the VHF signal detection unit (A) and the UHF signal detection unit (B) A switching unit 6 for selectively outputting a VHF or UHF signal, and a UHF IF signal and a VHF IF signal respectively generated according to the oscillation frequency output from the PLL unit 26 to amplify the UHF IF signal. signal An oscillator C for selectively amplifying any one of the VHF IFs and a first mixer for generating a first IF signal by mixing signals output from the switching unit 6 and the oscillator C; 15) and an output signal of the first mixer 15 to remove adjacent channels and image components, and then a predetermined amplifying unit D, a filter unit D for band filtering again, and an output of the filter unit D. Is mixed with a predetermined frequency signal to generate a second IF signal, and the second IF signal output from the second mixer 19 is demodulated and the sound component is extracted from the demodulated signal. After removing, the low frequency component is filtered to output a composite video signal, and the signal detector E detects a sound signal from the demodulated signal, and the gain of the demodulated signal is automatically adjusted by the signal detector E. Characterized by consisting of AGC (25) for controlling (1) Broadband receiving circuit.