Patent ID: 8913702

Claim:
A low noise block (LNB) frequency down conversion integrated circuit comprising: a pre-amplifier, to receive output of a mid-stage high frequency (HF) amplifier of a front-end circuit and improve the noise factor of a chip, so that the noise of the whole LNB system will not worsen; to transform a single-ended signal sent from the mid-stage HF amplifier into two differential signals to improve the suppression function of common mode noise in the chip; wherein the said two differential signals are a first differential signal with the phase of 0 degree and a second differential signal with the phase of 180 degree, respectively; a quadrature voltage-controlled oscillator, to output four local oscillation (LO) signals with phase difference of 90 degrees between with each other, wherein the four LO signals are a first LO signal with the phase of 90 degree, a second LO signal with the phase of 0 degree, a third LO signal with the phase of 270 degree and a fourth LO signal with the phase of 180 degree, respectively; a quadrature frequency mixer, to receive the four LO signals sent from the said Quadrature voltage-controlled oscillator and the two differential signals sent from the said pre-amplifier, wherein the quadrature mixer mixes the first LO signal with the first differential signal to produce a first intermediate frequency (IF) signal with the phase of 90 degree, mixes the second LO signal with the first differential signal to produce a second IF signal with the phase of 0 degree, mixes the third LO signal with the second differential signal to produce a third IF signal with the phase of 270 degree, and mixes the fourth LO signal with the second differential signal to produce a fourth IF signal with the phase of 180 degree; an In-phase/Quadrature (IQ) intermediate frequency (IF) amplifier, to receive the four IF signals sent by the said quadrature frequency mixer, to improve the driving capability of the said quadrature frequency mixer and to prevent the signals from attenuation; and a polyphase filter, to receive the output of the on-chip IQ intermediate frequency amplifier, and to filter the four IF signals, which eliminates minor image signal and realizes the minor image suppression function of the chip; and then to add the first IF signal with the second IF signal, to add the third IF signal with the fourth IF signal, which are of the four IF signals, thus generating two signal outputs.