CMOS single variable frequency circuit

Abstract

This invention discloses a CMOS mono-conversion circuit specially used in digital TV tuner chip composed of a three-band frequency-mixer, a three-band voltage-controlled oscillator, a filter drive circuit and an IF variable gain amplifier characterizing that oscillators of low, middle and high bands all apply the voltage-controlled oscillation basic circuits in the same circuit structure which is composed of a voltage-controlled oscillator, an amplitude detection circuit and a first comparator, two output ends of the oscillator are connected with two inputs of the amplitude detection circuit, the out put of which is linked with the negative input end of the first comparator which positive input is linked to vrefh, a second comparator and a charge pump are set between the detection circuit and the oscillator, the negative input of second is linked to output of the detection circuit, its positive is linked to the vreth.

Description

technical field [0001] The invention relates to a front-end tuning and receiving part circuit of a digital cable TV tuner, in particular to a CMOS single frequency conversion circuit specially used for a digital TV tuner chip. Background technique [0002] Due to practical technological breakthroughs in microelectronics technology, VLSI design technology, digital signal processing technology, computer technology, etc., digital television (DTV) technology is becoming more and more mature. Digital TV tuner, commonly known as high-frequency head, is a pre-stage component of digital TV receivers. It occupies a very important position in digital TV technology. Its function is to convert the modulated radio frequency signal carrying digital TV information to (Multi-channel signals) perform functions such as radio frequency reception, amplification, frequency conversion, filtering, analog-to-digital conversion, demodulation, error correction decoding...

AI Technical Summary

Problems solved by technology

[0006] It can be seen from Table 1 that although the double-conversion structure has high integration and does not require adjustment, it consumes a lot of power and costs high. This structure is more suitable for Cable Modem, but not suitable for cost-critical digital TV tuners. Therefore, comparing the tuning circuits of the three structures, the three-band single frequency conversion structure is the best circuit structure. At present, most of the domestic digital TV tuner dedicated chips use this kind of chip products.

At present, the three-band single-conversion structure integrated circuit mainly adopts the Bipolar process, which is expensive to manufacture and is not conducive to the integration of more functional circuits.

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