Passive Mixer Receiver for Odd-Harmonic Rejection Without SAW or LNA
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Solution Overview
Problem
Existing radio frequency (RF) receiver architectures for portable communication devices rely on SAW filters and LNAs, which increase complexity and power consumption, and fail to effectively reject odd harmonics of RF signals, leading to interference issues.
Innovation Solution
A low noise receiver architecture that eliminates SAW filters and LNAs by using a passive mixer with a switching configuration and a summation filter to generate gain-added output phases, effectively reducing odd harmonics through careful design and phase combination of local oscillator signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SAW filters and LNAs are used in the receiver architecture, then receive signal protection and amplification are improved, but device complexity and power consumption increase
Solution Approach 1:
The patent removes SAW filters and LNAs from the traditional receiver architecture, extracting these components that cause complexity and power consumption issues while maintaining their protective and amplification functions through alternative means (direct connection to passive mixer and harmonic rejection techniques)
Solution Approach 2:
The patent combines the functions of filtering and amplification into the passive mixer architecture itself, where the switching action of the passive mixer provides both signal processing and inherent filtering of odd harmonics, eliminating the need for separate SAW filter and LNA stages
2Reliability
If SAW filters and LNAs are used in the receiver architecture, then receive signal protection and amplification are improved, but power consumption increases
Solution Approach 1:
The patent removes power-hungry LNAs from the architecture and replaces them with a passive mixer that operates without requiring high power consumption, while still achieving signal amplification through the mixing process and subsequent baseband processing
Solution Approach 2:
The patent uses a passive mixer architecture that consumes minimal power compared to active LNA stages, accepting that the passive mixer has limitations (such as gain) that are compensated through other low-power means in the baseband domain
3Productivity
If traditional mixer architecture is used, then signal downconversion is achieved, but odd harmonic interference is not effectively rejected
Solution Approach 1:
The patent employs asymmetric switching ratios in the passive mixer (using switching ratios other than the traditional 50:50) to create frequency response characteristics that inherently reject odd harmonics while maintaining efficient signal downconversion, exploiting the asymmetric switching behavior to filter unwanted frequency components
Solution Approach 2:
The patent changes the switching ratio parameter of the passive mixer from the conventional 50% duty cycle to non-standard values, which fundamentally alters the frequency response to provide odd harmonic rejection while maintaining downconversion functionality
Data Source
AI summary
A low noise receiver includes a downconverter configured to receive a radio frequency (RF) signal, the downconverter comprising a switching architecture configured to generate a plurality of output phases based on a respective plurality of local oscillator (LO) signals, a differencing circuit configured to combine the plurality of output phases such that an nth output phase is differenced with an (n+K)th output phase, resulting in gain-added output phases, and a summation filter configured to receive the gain-added output phases and configured to combine the gain-added output phases such that a response of the receiver effectively reduces odd harmonics of the RF signal.