Passive-Mixer Tunable Filters Using LO-Controlled Delay Cells
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Solution Overview
Problem
Current technologies for ultra-wideband tunable filters, cancellers, and duplexers in smartphones are costly, complex, and suffer from distortion issues, failing to meet the need for efficient spectral utilization.
Innovation Solution
The development of tunable filters, cancellers, and duplexers based on passive mixers with a tunable delay cell and reflective-type filters, utilizing a control circuit to adjust local oscillator signals and feedforward paths to minimize distortion and enhance frequency tuning capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MEMS or switched filter banks are used for ultra-wideband tuning, then frequency tuning capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical MEMS systems with an electrical solution based on passive mixers and local oscillator signals. The tuning mechanism uses electrical switching of mixer components rather than mechanical movement, eliminating the complexity of MEMS while achieving ultra-wideband frequency tuning through electrical control of the mixing process
Solution Approach 2:
The passive mixer circuit serves multiple functions: it acts as a frequency translator, a tunable filter, and a signal combiner. By using the same basic mixer architecture with different LO signal configurations, the system can achieve various tuning modes without requiring separate dedicated circuits for each function
2Measurement precision
If traditional tunable filters are used, then frequency selectivity is improved, but distortion increases
Solution Approach 1:
The patent converts the typically harmful image frequencies produced by mixing into useful filtered signals. By using passive mixers with carefully designed LO signals and combining multiple mixer outputs, the system transforms what would be distortion products into desired frequency-selective output, achieving both tuning and filtering without additional distortion
Solution Approach 2:
The passive mixer acts as an intermediary that translates the input signal to intermediate frequencies where filtering occurs, then translates back to the desired output frequency. This indirect path through mixing and intermediate filtering avoids the distortion problems of direct tunable filter approaches while maintaining frequency selectivity
3Measurement precision
If resonance-based filters are used for multi-band tuning, then frequency filtering is improved, but device area and cost increase
Solution Approach 1:
Instead of using multiple physical resonance-based filters for different frequency bands, the patent changes the operating parameters of a single passive mixer circuit by varying the local oscillator frequency and phase. This allows the same hardware to be tuned across multiple bands without requiring additional physical filter components, dramatically reducing device area
Data Source
AI summary
Tunable filters, cancellers, and duplexers based on passive mixers. A tunable delay cell includes passive mixers electrically coupled together for receiving an input signal and outputting a delayed signal, each passive mixer comprising a plurality of mixer switches. The tunable delay includes a control circuit for providing, to each passive mixer, a respective plurality of local oscillator (LO) signals, one to each mixer switch of each passive mixer. The control circuit is configured to vary the LO signals to cause a target frequency band of the input signal to be delayed by a target delay time in propagating through the passive mixers.