Mixer-First Receiver Front-End Blocker Tolerance
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Solution Overview
Problem
RF receiver front-ends face challenges with noise factor and gain compression due to the use of narrow-band off-chip SAW filters, which are not compatible with software-defined radios and add cost and complexity, especially in multi-band applications.
Innovation Solution
A mixer-first receiver front-end design with two separate down-conversion paths that minimize added noise and voltage gain prior to baseband filtering, using passive mixers and transimpedance amplifiers to cancel thermal noise and reinforce the RF signal, eliminating the need for narrow-band off-chip RF filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If narrow-band off-chip SAW filters are used to attenuate large out-of-band interferers, then the linearity of the LNA is improved, but the noise factor increases and sensitivity degrades
Solution Approach 1:
The invention extracts and removes the narrow-band SAW filter from the receiver front-end architecture, eliminating its harmful effects (insertion loss, noise factor increase) while maintaining blocker attenuation through alternative means (digital signal processing in SDR)
Solution Approach 2:
The invention replaces the specialized narrow-band SAW filter with a universal wide-band filter that can handle multiple frequency bands, combined with software-defined radio processing that provides adaptive filtering and interferer rejection across different operating conditions
2Object-affected harmful factors
If narrow-band off-chip SAW filters are used, then out-of-band interferer attenuation is improved, but device complexity and cost increase
Solution Approach 1:
The invention merges the filtering function with the software-defined radio architecture, combining wide-band RF front-end components with digital signal processing to achieve both interferer attenuation and flexibility in a unified system
Solution Approach 2:
The invention uses software-based filter characteristics that can be copied and adjusted digitally for different frequency bands and operating conditions, replacing the need for multiple physical narrow-band filters
3Object-affected harmful factors
If narrow-band off-chip SAW filters are used, then interferer attenuation is improved, but adaptability to software-defined radios is reduced
Solution Approach 1:
The invention introduces dynamic adaptability by replacing fixed narrow-band filters with wide-band components and software-controlled filtering, allowing the system to dynamically adjust its frequency response and filtering characteristics based on operating conditions
Solution Approach 2:
The invention enables parameter changes in filter characteristics (center frequency, bandwidth, Q-factor) through software control rather than fixed hardware, allowing the same physical components to adapt to different frequency bands and signaling standards
Data Source
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AI summary
Because of associated disadvantages of narrow-band off-chip radio-frequency (RF) filtering, a mixer-first receiver front-end designed to tolerate blockers with minimal gain compression and noise factor degradation is disclosed. The mixer-first receiver front-end includes two separate downconversion paths that help to minimize added noise and voltage gain prior to baseband filtering, which are critical factors in eliminating narrow-band off-chip RF filtering.