Digital Tuner with Non-Tracking Filter Paths for Zero-IF Conversion
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Solution Overview
Problem
Existing digital terrestrial tuners face challenges in miniaturization and integration due to the need for tracking filters, which occupy significant space and require alignment, and double conversion tuners struggle with achieving the required dynamic range and image filtering.
Innovation Solution
A tuner design that eliminates the need for tracking filters by using a filter arrangement with non-tracking, fixed-frequency response signal paths and an automatic gain controller, allowing for integration in multi-chip modules and reduced manufacturing complexity, while maintaining performance through elliptic filters and a commutating signal generator for zero intermediate frequency conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tracking filters are used in single conversion tuners to achieve adequate selectivity, then signal selectivity is improved, but device area and manufacturing complexity increase due to alignment requirements
Solution Approach 1:
The patent extracts the tracking filter function from the front-end of the tuner and relocates filtering operations to the baseband stage. By using a zero-IF architecture with digital signal processing, the selective filtering function is separated from the RF front-end, eliminating the need for large-area tracking filters while maintaining signal selectivity through baseband filtering operations.
Solution Approach 2:
The patent replaces mechanical/physical tracking filters with electronic/digital filtering methods. Instead of using physical filter components that require alignment and occupy significant area, the invention uses digital signal processing techniques at baseband to achieve the same selectivity function, thereby eliminating alignment procedures and reducing device area.
2Reliability
If tracking filters are used to provide signal selectivity, then reception performance is improved, but ease of manufacture deteriorates due to alignment requirements
Solution Approach 1:
The patent extracts the selective filtering function from the RF front-end tracking filters and implements it at the baseband stage using digital signal processing. This separation eliminates the need for mechanical alignment procedures during manufacturing, as the filtering is performed electronically after frequency conversion, thereby improving ease of manufacture while maintaining reception performance.
Solution Approach 2:
The patent inverts the traditional filtering approach by performing selective filtering at baseband rather than at RF frequencies. Instead of filtering signals before frequency conversion, the invention converts all signals to baseband first and then applies selective filtering, which eliminates alignment requirements and simplifies manufacturing.
3Adaptability or versatility
If double conversion technique is used to achieve broadband reception, then frequency range is improved, but dynamic range and image filtering become more difficult
Solution Approach 1:
The patent extracts the image rejection function from separate image filters and integrates it into the baseband signal processing path. By using a zero-IF architecture where all signals are converted to baseband, the image frequency problem is eliminated at the source, and selective filtering at baseband naturally rejects image components without requiring additional high-Q image filters.
Solution Approach 2:
The patent introduces baseband signal processing as an intermediary stage between RF frequency conversion and final signal output. This baseband intermediary performs both the frequency translation and the selective filtering functions, thereby simplifying the overall architecture and eliminating the need for complex image filters while maintaining broadband reception capability.
4Adaptability or versatility
If broadband front-end is used in double conversion tuners, then frequency coverage is improved, but achieving required dynamic range becomes more difficult
Solution Approach 1:
The patent segments the signal processing function into distinct stages: broadband RF front-end for frequency coverage, zero-IF frequency conversion to baseband, and then selective filtering at baseband. This segmentation allows the front-end to focus on wide frequency coverage while the baseband processing stage handles dynamic range requirements through selective filtering, thereby resolving the contradiction between broadband coverage and dynamic range.
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 design enables a compact, flexible tuner with reduced manufacturing costs, capable of accommodating different frequency ranges without alignment procedures, and achieves acceptable performance by minimizing noise and intermodulation interference.
Implementation Method 1
a zero or near-zero intermediate frequency frequency changer for selecting any one of at least some of the channels and comprising at least one mixer and commutating signal generator
Implementation Method 2
a filter arrangement disposed between the frequency changer and the tuner input and comprising a plurality of signal paths of different frequency responses selectable one at a time
Data Source
AI summary
A digital terrestrial tuner has an RF input connected to a filter arrangement, whose output signal is supplied to a zero intermediate frequency frequency changer. The filter arrangement comprises a plurality of signal paths of different frequency responses. The signal paths are selectable one at a time for insertion between the tuner input and the frequency changer. At least one of the signal paths comprises a non-tracking filter which provides attenuation of out-of-band signals so as to reduce harmonic mixing caused by harmonics of the frequency changer commutating signal or by harmonics of spurious signals at lower frequencies.