Single Conversion Tuner for High Image Rejection and Flat Pass Band
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Summary
Problems
Existing television tuners face challenges in achieving high image rejection and pass band flatness for both off-air and cable reception, leading to suboptimal reception quality due to the different modulation schemes used in these scenarios, and current solutions either require complex dual-conversion architectures or separate tuners optimized for each type of reception.
Innovation solutions
A single conversion tuner incorporating a pre-select filter, amplifier, and image reject mixer that down-converts RF signals directly to an IF frequency, utilizing a tuneable bandpass filter for channel selection and providing high linearity and pass band flatness, allowing for efficient channel selection and improved image rejection.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If a single conversion tuner is used for both off-air and cable reception, then device complexity is reduced, but it cannot simultaneously achieve high image rejection for off-air reception and high pass band flatness for cable reception
Why choose this principle:
The patent employs a dynamically reconfigurable filter structure that can switch between different operational modes. The filter's characteristics (bandwidth, center frequency, order) are dynamically adjusted based on the detected signal type (8VSB or QAM), allowing the same hardware to optimize performance for both off-air and cable reception without requiring separate dedicated tuners
Principle concept:
If a single conversion tuner is used for both off-air and cable reception, then device complexity is reduced, but it cannot simultaneously achieve high image rejection for off-air reception and high pass band flatness for cable reception
Why choose this principle:
The invention changes the filter parameters (bandwidth, order, center frequency) based on the modulation scheme being received. For 8VSB off-air signals, the filter operates with higher order and narrower bandwidth to maximize image rejection, while for QAM cable signals, it transitions to lower order and wider bandwidth to ensure pass band flatness and linearity
Application Domain
Data Source
AI summary:
A single conversion tuner incorporating a pre-select filter, amplifier, and image reject mixer that down-converts RF signals directly to an IF frequency, utilizing a tuneable bandpass filter for channel selection and providing high linearity and pass band flatness, allowing for efficient channel selection and improved image rejection.
Abstract
A single conversion tuner suitable for receiving RF signals having different requirements as to selectivity, linearity and image rejection is presented. Tuners of this kind are particularly useful for digital terrestrial as well as cable reception, where different modulation schemes require very high image rejection ratios on one hand and high linearity or pass band flatness on the other hand. The inventive tuner features a double-tuned tuneable filter in combination with an image reject mixer. The double-tuned filter provides excellent pass band flatness, while the image reject mixer provides a high intrinsic image rejection. The image rejection ratio of the combination of image reject mixer and tuneable filter is very high and fulfils the requirements of commonly used modulation schemes such as 8VSB, while the pass band flatness is compliant with the requirements for modulation schemes such as QAM.