Single-Ended RF Amplifier-Mixer Feedback for DC Offset and IM2 Suppression
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Solution Overview
Problem
Conventional WCDMA receiver architectures with SAW filters between the LNA and mixer suffer from DC-offset and intermodulation distortion due to TX-leakage, requiring additional components and increasing cost and PCB area, especially in multiband solutions.
Innovation Solution
A single-ended multiband feedback amplifier and mixer architecture with a mixer feedback loop circuit that generates a feedback signal to minimize DC-offset and second-order intermodulation products, eliminating the need for an off-chip SAW filter by achieving high enough second and third-order linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SAW filter is used between the LNA and mixer to attenuate TX-leakage, then receiver performance is improved by reducing intermodulation distortion, but device complexity and PCB area increase
Solution Approach 1:
The patent removes the external SAW filter from the receiver architecture and extracts its filtering function by implementing an all-single-ended mixer design with inherent rejection of TX-leakage signals. This eliminates the need for the separate SAW filter component while maintaining the intermodulation distortion rejection capability.
Solution Approach 2:
The patent combines the filtering function previously performed by the SAW filter into the mixer circuit itself. The all-single-ended mixer architecture integrates the interference rejection capability directly into the mixing operation, merging the functions of signal mixing and interference filtering into a single component.
2Object-generated harmful factors
If a SAW filter is used between the LNA and mixer to attenuate TX-leakage, then intermodulation distortion is reduced, but cost and PCB area increase
Solution Approach 1:
The patent removes the external SAW filter component that occupies PCB area and replaces its function with an integrated all-single-ended mixer design. This extraction eliminates the need for additional PCB space dedicated to the SAW filter while maintaining intermodulation distortion rejection.
Solution Approach 2:
The all-single-ended mixer is designed to perform multiple functions: signal mixing, TX-leakage rejection, and intermodulation distortion suppression. This multi-functional design eliminates the need for separate dedicated filter components, reducing overall PCB area requirements.
3Reliability
If a differential mixer is used with single-ended LNA, then mixing performance is improved, but a large on-chip balun is needed increasing area
Solution Approach 1:
The patent employs an all-single-ended mixer architecture that deliberately uses asymmetric, non-differential signaling throughout the mixing path. This asymmetric design eliminates the need for baluns and differential-to-single-ended conversions, reducing on-chip area while maintaining mixing performance through careful circuit design.
Solution Approach 2:
Instead of converting from single-ended to differential signaling (the conventional approach), the patent inverts the approach by maintaining single-ended signaling throughout and achieving performance benefits through the single-ended architecture itself, eliminating the need for area-consuming balun components.
4Adaptability or versatility
If an on-chip balun is used to create differential RF signal, then signal conversion is achieved, but device complexity and area increase
Solution Approach 1:
The patent removes the on-chip balun component entirely and extracts the signal conversion function by designing the entire mixing path in single-ended architecture. This eliminates the need for differential signaling conversion while maintaining adaptability to handle RF signals across different bands.
Solution Approach 2:
The all-single-ended mixer is designed to be universally applicable across multiple frequency bands without requiring additional balun components. The single-ended architecture provides band versatility through its inherent design characteristics, eliminating the need for complex differential signaling infrastructure.
Data Source
AI summary
A receiver arrangement includes a single ended multiband feedback amplifier, at least one single ended input, differential output mixer arrangement including a main mixer and a trim mixer, and a mixer feedback loop circuit configured to receive differential output signals generated by the mixer arrangement. The mixer feedback loop circuit generates a feedback signal based on the received differential output signals and provides the feedback signal to the mixer arrangement to minimize DC-offset and second order intermodulation products. The single ended multiband feedback amplifier may include an input stage and a programmable resonance tank circuit connected to the input stage for suppressing downconverted noise from harmonics of the LO-frequency, and a configurable feedback net that shapes the frequency response of a feedback loop including the feedback net based on a band operation of the single ended multiband feedback amplifier.