Single-Ended Multiband RF Amplifier-Mixer Feedback Without SAW Filters
Find Innovative SolutionsGenerate Solutions
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, while existing solutions for multiband operation are inefficient.
Innovation Solution
A single-ended multiband feedback amplifier and mixer architecture with a feedback loop and programmable resonance tank circuit that suppresses DC-offset and intermodulation distortion without the need for SAW filters, using a configurable resistive and capacitive network to shape the frequency response and minimize second and third-order linearity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SAW filter is used between the LNA and mixer to attenuate TX-leakage, then the receiver performance is improved by reducing intermodulation distortion, but the cost and PCB area increase
Solution Approach 1:
The patent removes the SAW filter from the receiver architecture by implementing a feedback mechanism that actively cancels TX-leakage signals. The feedback loop extracts and suppresses the harmful intermodulation products generated by the LNA and mixer, eliminating the need for the external SAW filter component while maintaining receiver performance.
Solution Approach 2:
The patent implements a feedback path that samples the mixer output and feeds it back to the LNA input through a feedback network. This feedback mechanism actively cancels TX-leakage signals and reduces intermodulation distortion by adjusting the feedback signal to oppose the harmful components, replacing the passive SAW filter with an active cancellation system.
2Adaptability or versatility
If multiple SAW filters are used for multiband operation to handle different frequency bands, then the receiver can support multiple bands, but the PCB area and cost increase significantly
Solution Approach 1:
The feedback network is designed with multiband capability, using switches and capacitors that can be configured for different frequency bands. The same feedback loop structure handles TX-leakage cancellation across multiple bands, eliminating the need for separate SAW filters for each band while maintaining multiband support.
Solution Approach 2:
The patent employs dynamic switching elements (switches and variable capacitors) in the feedback network that can be reconfigured for different frequency bands. This dynamic adjustment allows the single feedback loop to adapt to multiple bands, replacing the static multiple SAW filter approach with a reconfigurable single-loop system.
3Reliability
If a differential LNA and differential mixer are used to reduce TX-leakage effects, then the linearity is improved, but an additional package pin is required increasing the package size
Solution Approach 1:
The patent uses a feedback mechanism to achieve high linearity and reduce TX-leakage effects in a single-ended architecture. The feedback loop actively cancels the intermodulation products that would otherwise require differential signaling, achieving similar linearity performance without the need for differential components and additional package pins.
4Ease of operation
If an on-chip balun is used to create differential RF signal in a single-ended LNA and differential mixer configuration, then the signal conversion is achieved, but the area penalty is increased
Solution Approach 1:
The patent removes the on-chip balun from the architecture by implementing the entire signal path in single-ended topology. The feedback mechanism works directly with single-ended signals, eliminating the need for balun-based differential conversion and the associated area penalty.
Data Source
Figure 1
Figure 2
Figure 3
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.