Complex-Baseband Image Rejection for Low-Power Video Receivers
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Solution Overview
Problem
Existing silicon tuners for analog video reception face challenges in achieving a balance between image rejection and power consumption, often resulting in compromised performance at low power or reasonable performance at high power, making them unsuitable for small portable devices.
Innovation Solution
A direct-conversion analog video receiver architecture that includes a direct-conversion tuner, offset cancellation circuitry, and adaptive image rejection mechanisms, along with a power management system to dynamically adjust power consumption based on video signal availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete tuner cans are used for analog video reception, then robust performance is achieved, but power consumption increases to two to three watts and size increases
Solution Approach 1:
The patent replaces the mechanical/discrete component-based tuner can architecture with a silicon-based integrated circuit implementation. This substitution integrates multiple discrete components (mixers, filters, amplifiers) into a single silicon chip, dramatically reducing power consumption from 2-3 watts to sub-watt levels while maintaining the superheterodyne receiver architecture and performance characteristics.
Solution Approach 2:
The patent combines multiple discrete tuner components (RF amplifier, mixer, local oscillator, IF filter, detector) into a single integrated silicon tuner circuit. This merging of functions onto one chip reduces overall power consumption, minimizes inter-component signal paths, and enables portable video reception applications.
2Use of energy by moving object
If silicon tuners are implemented with low power consumption, then power efficiency improves, but image rejection performance deteriorates
Solution Approach 1:
The patent implements preliminary image rejection filtering in the IF stage before the desired signal is fully processed. By placing the image-reject filter at the intermediate frequency stage, the system preemptively removes image frequency components before they can interfere with signal processing, achieving effective image rejection without requiring additional power-consuming stages.
Solution Approach 2:
The patent introduces an intermediate frequency (IF) stage as a mediator between the RF mixing stage and the baseband processing stage. This IF stage includes a bandpass filter that selectively passes the desired signal frequency while rejecting image frequencies, providing effective image rejection through the intermediary filtering action without directly processing the high-frequency RF signals.
3Reliability
If silicon tuners are implemented with reasonable image rejection performance, then performance improves, but power consumption increases to high levels
Solution Approach 1:
The patent segments the image rejection function into multiple stages: first-stage image rejection through the IF bandpass filter and second-stage rejection through the audio bandpass filter. This segmentation allows each filter stage to operate at lower power levels while collectively achieving the required overall image rejection performance, avoiding the need for a single high-power filtering stage.
Data Source
AI summary
An analog video receiver implemented in an integrated circuit device. The analog video receiver includes first and second mixing circuits to generate a complex baseband signal by mixing a carrier-frequency analog video signal with respective sinusoids of a quadrature sinusoid pair; and a filtering circuit to subtract a scaled complex conjugate of the complex baseband signal from the complex baseband signal.