Frequency-Translatable Impedance Filters for RF Blocker Attenuation
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Solution Overview
Problem
Current communication systems face challenges in minimizing unwanted intermodulation components generated by non-linear circuit blocks in RF transceivers, particularly due to the high power levels of residual signals from duplexers, which require highly linear mixers that are impractical and costly to implement, and existing filters like SAW and LC tank filters have limitations in attenuating blockers effectively.
Innovation Solution
The implementation of frequency translatable impedance (FTI) filters, which attenuate blockers relative to the wanted channel, allowing for the use of mixers with relaxed linearity requirements by translating impedance frequencies and providing tunable center frequencies and Q-factors, thereby reducing the need for external high-Q filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If highly linear mixers are used to minimize intermodulation components, then receiver performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by placing filters before the mixer to attenuate blockers and reduce the power level of unwanted signals. This preprocessing step reduces the linearity requirements of the subsequent mixer, allowing the use of less complex and more cost-effective mixer designs while maintaining receiver performance.
Solution Approach 2:
The patent introduces filters as intermediary components between the antenna/duplexer and the mixer. These filters serve as mediators that condition the input signals by attenuating blockers before they reach the mixer, thereby reducing the intermodulation components generated by the mixer without requiring the mixer itself to have high linearity.
2Reliability
If external high-Q filters are used to attenuate blockers, then signal filtering performance is improved, but device complexity and integration difficulty increase
Solution Approach 1:
The patent merges the filter function with the mixer by integrating filtering components directly into the mixer circuit. This combination eliminates the need for separate external high-Q filters, reducing device complexity and facilitating integration into ICs while maintaining effective blocker attenuation performance.
Solution Approach 2:
The patent creates a multi-functional mixer that combines both mixing and filtering operations in a single component. This universal component performs multiple functions (signal mixing and blocker attenuation) simultaneously, eliminating the need for separate filter components and simplifying the overall receiver architecture.
3Reliability
If SAW filters are used to attenuate blockers, then filtering effectiveness is improved, but ease of manufacture and integration into ICs deteriorates
Solution Approach 1:
The patent replaces mechanical SAW (Surface Acoustic Wave) filter structures with electrical circuit implementations that can be manufactured using standard IC fabrication processes. This substitution maintains the blocker attenuation functionality while enabling direct integration into integrated circuits, significantly improving ease of manufacture.
Data Source
AI summary
A system including a filter and a downconverter. The filter is configured to receive, from a node, (i) a first signal and (ii) a second signal, and filter the second signal. The filter includes a first input impedance. The filter comprises a first plurality of switches and a first circuit. The first plurality of switches is configured to communicate with the node. The first plurality of switches is clocked at a first frequency. The first frequency is based on a frequency of the first signal. The first circuit is configured to communicate with an output of the plurality of switches. The first circuit includes a second input impedance. The second input impedance is different than the first input impedance. The downconverter is configured to (i) receive the first signal and (ii) downconvert the first signal. The filter and the downconverter are connected in parallel to the node.