TV Tuner Front-End Circuit With Band Splitting and Interference Rejection

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Solution Overview

Problem

Television receiver front-end circuits lack frequency selectivity, leading to large power differences between channels, and struggle to maintain dynamic range and interference rejection, especially in terrestrial TV reception, while also requiring compatibility with multiple tuners and cable TV signals.

Innovation Solution

The design incorporates a tuner front-end circuit with frequency selective terminating and resonant circuits that split RF signals into separate bands, using low-noise amplifiers with automatic gain control and tracking filters to ensure even power levels and minimize interference, allowing for multiple tuners to operate without degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If frequency selective circuits are added to provide channel selectivity, then interference rejection is improved, but device complexity increases

Engineering Contradiction:

Improveinterference rejectionVSAvoidcircuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The front-end circuit is segmented into multiple frequency bands using parallel resonant circuits, each tuned to a specific channel frequency. This segmentation allows selective amplification of desired channels while rejecting others, improving interference rejection without requiring a single complex filter system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Resonant circuits act as intermediary elements between the broadband amplifier and the output, selectively passing desired frequencies while blocking others. These intermediary circuits provide the necessary frequency selectivity with relatively simple components.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If high gain amplification is used to improve signal strength, then dynamic range is improved, but distortion from strong interfering signals increases

Engineering Contradiction:

Improvedynamic rangeVSAvoidsignal distortion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The amplification function is segmented into multiple parallel amplifier circuits, each dedicated to a specific frequency band. This allows each amplifier to operate at optimal gain levels for its assigned band without being overloaded by strong signals in other bands, maintaining dynamic range while reducing distortion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The circuit converts potentially harmful strong interfering signals into benefit by using resonant circuits to selectively attenuate them before they reach the amplifiers. Strong signals on unwanted channels are naturally rejected by the frequency-selective resonant circuits, preventing overload and distortion.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If discrete components and varactor diodes are used for tuning, then frequency selectivity is improved, but integration level decreases

Engineering Contradiction:

Improvefrequency selectivityVSAvoidintegration level

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The resonant circuits serve multiple functions: they provide frequency selection, impedance transformation, and signal coupling simultaneously. This multi-functionality reduces the need for separate discrete components and enables better integration compared to traditional varactor-based tuning circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach provides high dynamic range and selectivity, maintaining signal quality across a wide range of power levels and frequencies, enabling efficient operation with both terrestrial and cable TV signals without compromising performance or requiring additional buffers.

Implementation Method 1

resonant circuits that split RF signals into separate bands

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

low-noise amplifiers with automatic gain control

Methodology Applied

Scientific EffectSignal amplification:

Implementation Method 3

tracking filters to ensure even power levels and minimize interference

Methodology Applied

Scientific EffectFrequency selective filtering: Resonance

Data Source

PatentUS8457574B2Front-end integrated circuit for television receivers

Publication Date: 2013.06.04 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

A tuner front-end circuit for processing a radio frequency (RF) signal includes a first filter block that terminates the RF signal for unwanted frequency bands; a second filter block that provides selectivity within the unterminated signal by separating the unterminated signal into a plurality of separate signals, each of a different desired frequency band; and an amplifier block that amplifies each of the separate signals. One or more of the amplified separate signals can be provided to a tuner. The circuit can also include a daisy chain output block that provides the amplified separate signals to one or more additional tuners. One or more tracking filter blocks can also be included to provide further selectivity to the amplified separate signals and to reject signals at specific harmonics to prevent degradation of a signal-to-noise ratio. A method of processing an RF signal is also presented.