Single Down-Conversion TV Tuner with Harmonic Rejection Mixer
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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 complex circuitry with multiple voltage-controlled oscillators for frequency tuning.
Innovation Solution
A miniaturized single-conversion television tuner architecture that employs low and high pass filters, a local oscillator with a tunable reference signal, harmonic rejection and quadrature mixers, and digital signal processing to generate in-phase and quadrature-phase signals, eliminating harmonic and image frequency components, and allowing for integration into a single-chip IC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional CAN tuner with discrete RF tracking filters is used, then harmonic rejection is achieved, but device size becomes bulky and integration into single-chip IC is difficult
Solution Approach 1:
The patent combines multiple discrete components (RF tracking filters, mixers, oscillators) into a single integrated circuit chip. The harmonic rejection function is integrated directly into the mixer circuitry through digital signal processing, eliminating the need for separate discrete RF tracking filters and reducing overall device volume.
Solution Approach 2:
The patent replaces traditional analog RF tracking filters with digital signal processing techniques implemented in the integrated circuit. The harmonic rejection is achieved through digital filtering and processing of the mixed signals, substituting mechanical/analog filter components with digital logic and algorithms.
2Reliability
If multiple RF tracking filters are used for harmonic rejection, then signal quality is maintained, but circuit complexity and manufacturing cost increase
Solution Approach 1:
The integrated mixer circuit performs multiple functions simultaneously: frequency mixing, harmonic rejection, and signal filtering. The digital signal processing unit handles both image rejection and harmonic filtering, eliminating the need for separate dedicated circuits for each function and reducing overall circuit complexity.
Solution Approach 2:
The patent changes the approach from analog filter parameter tuning to digital signal processing parameter control. The harmonic rejection and filtering characteristics are controlled through digital algorithms and software, allowing for flexible adjustment without changing physical circuit parameters or adding complex analog filter stages.
3Volume of moving object
If up-down dual conversion tuner with two mixers is used, then single-chip integration is achieved, but image frequency interference and circuit complexity remain
Solution Approach 1:
The patent introduces a digital signal processing intermediary between the mixing stage and the output stage. This digital processor acts as a mediator that selectively filters out image frequency components while preserving the desired signal, enabling effective image rejection without requiring complex additional mixing stages.
4Object-affected harmful factors
If conventional tuner architecture with multiple discrete devices is used, then harmonic rejection is achieved, but manufacturing cost and integration difficulty increase
Solution Approach 1:
The patent merges all necessary functions (RF amplification, mixing, filtering, harmonic rejection, and demodulation) into a single integrated circuit chip. This consolidation eliminates the need for assembling multiple discrete devices, significantly improving ease of manufacture and enabling standard IC fabrication processes.
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 solution reduces device size and cost, simplifies circuit complexity, and enables efficient frequency translation and demodulation of television signals while maintaining desirable signal quality and rejecting harmonic and image interference.
Implementation Method 1
a low pass filter for extracting a first-band signal from the television signal; a high pass filter disposed in parallel to the low pass filter for extracting a second-band signal from the television signal
Implementation Method 2
a local oscillator generating a reference signal having a frequency tunable depending on a desired channel
Implementation Method 3
a harmonic rejection and quadrature mixer coupled to the low pass filter for processing the first-band signal with the reference signal to output a first pair of in-phase and quadrature-phase signals with a harmonic-frequency component eliminated
Implementation Method 4
a quadrature mixer coupled to the high pass filter for processing the second-band signal with the reference signal to output a second pair of in-phase and quadrature-phase signals
Data Source
AI summary
A television tuner employs a single down-conversion architecture to translate VHF/UHF TV signals to various standard IF frequencies. The television tuner includes a harmonic rejection and quadrature mixer and a quadrature mixer. The harmonic rejection and quadrature mixer mixes a first-band signal with a reference signal to output a first pair of in-phase and quadrature-phase signals with a harmonic-frequency component eliminated from the resulting signals. A quadrature mixer mixes a second-band signal with the reference signal to output a second pair of in-phase and quadrature-phase signals. A digital signal processing circuit coupled to both the harmonic rejection and quadrature mixer and the quadrature mixer for selectively processing either the first pair of in-phase and quadrature-phase signals or the second pair of in-phase and quadrature-phase signals to generate an output signal corresponding to a desired channel.