Triple-Conversion TV Tuner for Harmonic and Image Rejection
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Solution Overview
Problem
Conventional television tuners are bulky and cost-ineffective due to the use of discrete electronic devices like RF tracking filters, which are difficult to integrate into a single-chip IC, and require high voltage varactors for band tuning, leading to increased circuit complexity and chip size.
Innovation Solution
A triple-conversion television tuner architecture with a first local oscillator generating a fixed frequency reference signal, followed by three mixers - a harmonic rejection mixer for up-conversion, an image rejection mixer for up-conversion, and another image rejection mixer for down-conversion - to achieve frequency translation with reduced device size and cost, utilizing local oscillators and mixers to optimize chip size and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RF tracking filters are used to reduce harmonic power, then signal quality is improved, but device size and complexity increase
Solution Approach 1:
The patent extracts and eliminates the harmful harmonic components through a specific mixing architecture that converts the input signal through multiple stages, separating the desired signal from harmonic distortions. The triple-conversion process extracts the fundamental frequency while rejecting harmonics generated by non-linear mixing elements.
Solution Approach 2:
The patent introduces intermediate frequency stages as mediators between the RF input and baseband output. By using multiple LO signals at different frequencies (f1, f2, f3) and creating intermediate representations of the signal, the system achieves harmonic rejection without requiring bulky RF tracking filters.
2Measurement precision
If discrete electronic devices are incorporated, then filtering performance is improved, but integration difficulty increases
Solution Approach 1:
The patent merges multiple filtering and frequency conversion functions into a unified triple-conversion mixing architecture. By combining the roles of RF tracking filters, image rejection filters, and frequency converters into a single integrated signal path with three mixing stages, the design achieves high filtering performance while enabling single-chip integration.
Solution Approach 2:
The mixing stages serve multiple functions simultaneously: frequency conversion, harmonic rejection, and image frequency suppression. Each mixer stage is designed to perform multiple roles in the signal chain, reducing the need for separate discrete filtering components and enabling compact integration.
3Adaptability or versatility
If high voltage varactors are used for band tuning, then tuning range is improved, but chip size and cost increase
Solution Approach 1:
The patent changes the operating parameters of the mixing stages by using multiple LO frequencies (f1, f2, f3) to achieve broad tuning coverage. Instead of relying on high voltage varactors for wide tuning, the system achieves adaptability through parameter variation in the frequency domain, allowing standard low-voltage varactors to suffice and reducing chip size.
4Measurement precision
If multiple mixers and local oscillators are used, then frequency translation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the frequency translation process into three distinct conversion stages, each handling a specific portion of the frequency mapping. This segmentation allows each mixer-LO pair to be optimized for its specific frequency range, improving overall accuracy while organizing the complexity into manageable modular stages.
Solution Approach 2:
The patent maintains continuous signal flow through the three mixing stages without interruption, ensuring that the useful signal component is continuously processed and transformed. This continuous action preserves signal integrity and accuracy throughout the conversion chain, while the systematic arrangement of stages manages the inherent complexity.
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
The triple-conversion tuner reduces device size and cost while maintaining signal quality by eliminating harmonic effects and achieving a high signal-to-noise ratio through efficient frequency translation, enabling a more compact and cost-effective single-chip television tuner design.
Implementation Method 1
a first local oscillator for generating a first reference signal at a first frequency, a second local oscillator for generating a second reference signal at a second frequency, and a third local oscillator for generating a third reference signal at a third frequency
Implementation Method 2
a first mixer for mixing the television signal with the first reference signal to produce a first harmonic mixture including a first desired channel at a first intermediate frequency, a second mixer for mixing the first intermediate frequency with the second reference signal to produce a second harmonic mixture including a second desired channel at a second intermediate frequency, and a third mixer for mixing the second intermediate frequency with the third reference signal to produce a third harmonic mixture including a third desired channel at a third intermediate frequency
Data Source
AI summary
A television tuner employs a triple-conversion architecture to translate VHF/UHF TV signals to various standard IF frequencies. The television tuner includes a harmonic rejection mixer, a first image rejection mixer and a second image rejection mixer. The television tuner receives a television signal. The harmonic rejection mixer up-converts the television signal into a first IF signal according to a first reference signal with a fixed frequency. The first image rejection mixer further up-converts the first IF signal into a second IF signal according to a second reference signal with a tunable frequency. The second image rejection mixer down-converts the second IF signal into a third IF signal according to a third reference signal with a tunable frequency.