TV Tuner Amplifier Feedback Circuit for Noise Figure and Return Loss

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Television receiver circuits face challenges in achieving optimal noise figure, return loss, and linearity simultaneously, often requiring trade-offs due to interference between components.

Innovation Solution

The implementation of a low noise amplifier with a loop through output that uses a single amplifier to provide both a good noise figure and return loss without loading the input terminal, utilizing a negative gain amplifier and feedback to decouple noise figure and return loss, and a switch matrix to select appropriate tracking filters for channel tuning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate amplifier is added to provide loop through output, then the noise figure is improved, but the return loss deteriorates due to input terminal loading

Engineering Contradiction:

Improvenoise figureVSAvoidreturn loss

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The main amplifier is designed to perform multiple functions simultaneously: it provides both the primary amplified output and the loop through output. By making the amplifier universal, the patent eliminates the need for a separate amplifier that would load the input terminal and degrade return loss, while still achieving good noise figure performance through proper circuit design

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the loop through function with the main amplification function into a single amplifier circuit. The amplifier is configured to provide both the main output signal and the loop through output signal without requiring separate amplification paths, thereby avoiding input terminal loading and maintaining good return loss

Inventive Principle:

Principle #5Merging (Combining)

2Object-affected harmful factors

If traditional receiver circuits are used, then cable television signals are processed with acceptable return loss, but noise figure and linearity cannot be optimized simultaneously due to component interference

Engineering Contradiction:

Improvereturn lossVSAvoidnoise figure and linearity

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the loop through output is fed back to the input of the amplifier. This feedback allows the circuit to maintain good return loss by compensating for loading effects, while simultaneously enabling optimization of noise figure and linearity through controlled signal regeneration and interference cancellation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The amplifier circuit is segmented into distinct functional sections with separate biasing and control mechanisms. This segmentation allows independent optimization of different parameters (return loss, noise figure, linearity) in different parts of the circuit, reducing interference between components while maintaining overall system performance

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9094634B2Amplifier for television tuner chip and method therefor

Publication Date: 2015.07.28 SILICON LABORATORIES INC

AI summary

An amplifier includes a negative gain amplifier, a load element, and a transconductance device. The negative gain amplifier has an input and an output. The load element has a first terminal coupled to a power supply voltage terminal, and a second terminal. The transconductance device has a first current electrode coupled to the second terminal of the load element, a control electrode coupled to the output of the negative gain amplifier, and a second current electrode coupled to the input of the negative gain amplifier.