Multi-Band TV Tuner With Tri-State Chopper Harmonic Rejection
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Solution Overview
Problem
Direct conversion TV tuners face challenges with harmonic mixing, where undesired signals are converted due to odd-order harmonics of the local oscillators, making it difficult to select specific channels within a wide frequency range without spurious mixing products.
Innovation Solution
A tri-state chopper-based frequency conversion method using periodic control signals with specific timing offsets to generate multi-level transmit waves, which are combined to reject harmonics, effectively eliminating up to the 7th order harmonics and reducing spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct conversion architecture is used to convert RF signals to baseband, then the desired channel can be successfully converted, but harmonic mixing occurs where undesired channels are also converted due to odd-order harmonics of the LO signals
Solution Approach 1:
The patent segments the frequency conversion process into multiple parallel paths (first frequency conversion path, second frequency conversion path, third frequency conversion path) each handling different frequency bands. By dividing the wide frequency range into separate segments and processing them independently, the system avoids harmonic mixing between channels from different bands while maintaining direct conversion benefits within each segment.
Solution Approach 2:
The patent introduces an intermediary frequency conversion stage before the final baseband conversion. Signals are first converted to an intermediate frequency, then subsequently converted to baseband. This intermediary step acts as a mediator that prevents direct harmonic mixing between RF channels and baseband, allowing for better spectral separation and reduced spurious mixing products.
2Adaptability or versatility
If the tuner frequency range is extended to cover a wide bandwidth, then more channels can be received, but the complexity of avoiding harmonic mixing increases
Solution Approach 1:
The patent divides the wide frequency range into multiple discrete frequency bands, each handled by a dedicated frequency conversion path. This segmentation allows the system to cover a broad frequency spectrum while maintaining simple harmonic rejection within each band, as each path can be optimized independently without requiring complex cross-band interference management.
Solution Approach 2:
The patent creates a universal frequency conversion architecture where multiple conversion paths share common components such as the quadrature generator and baseband processing stages. This multi-functional design allows the system to handle multiple frequency bands using a standardized approach, reducing overall system complexity while maintaining broad frequency coverage capability.
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 significantly reduces harmonic mixing, allowing for effective selection of specific channels within a wide frequency range by suppressing unwanted harmonics and improving the purity of the converted signals.
Implementation Method 1
a quadrature frequency converter for receiving one of said processed RF signals and converting the received processed RF signal into a in-phase baseband signal and a quadrature baseband signals
Implementation Method 2
The in-phase path receives the RF signal 122 and converts it into a first digital baseband signal BB_I by mixing the RF signal 122 with an in-phase clock LO_I using mixer 130_I
Implementation Method 3
A tri-state chopper-based frequency conversion method using periodic control signals with specific timing offsets to generate multi-level transmit waves, which are combined to reject harmonics, effectively eliminating up to the 7th order harmonics
Data Source
AI summary
A direct conversion multi-band TV tuner includes: a plurality of RF (radio frequency) paths for processing the RF signal and for generating a plurality of processed RF signals, respectively; and a TSC (tri-state chopper) based quadrature frequency converter for receiving one of said processed RF signals and converting the received processed RF signal into a in-phase baseband signal and a quadrature baseband signals; wherein the TSC based quadrature frequency converter operates in accordance with a first set of periodic three-state control signals and a second set of periodic three-state control signals that are approximately 90 degrees offset from the first set of periodic three-state control signals.