Rotating Harmonic Rejection Mixer With Cyclic Gain-Stage Weighting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional harmonic rejection mixers face challenges in effectively rejecting harmonic frequencies introduced by non-sinusoidal local oscillator signals due to device mismatches and phase deviations, leading to performance degradation and increased power consumption.
Innovation Solution
A rotating harmonic rejection mixer design that cyclically rotates the mixed signal through multiple gain stages, using a master clock signal to weight and combine outputs, thereby reducing harmonic rejection issues while minimizing power and area consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple mixer stages with precise device matching are used to achieve harmonic rejection, then harmonic rejection performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The mixer is divided into multiple parallel mixer stages, each receiving the RF input signal and local oscillator signal. The outputs of these stages are then combined through a summation network. This segmentation allows each individual mixer stage to be simpler while achieving overall harmonic rejection through the coordinated operation of multiple stages with different phase relationships.
Solution Approach 2:
The mixer stages are configured with asymmetric phase relationships relative to the local oscillator signal. Specifically, the stages operate at different phases (e.g., 0°, 90°, 180°, 270°) to create an asymmetric phase distribution pattern. This asymmetric configuration, when combined with appropriate weighting, enables selective cancellation of harmonic frequencies while maintaining the desired fundamental frequency.
2Manufacturing precision
If device sizes are increased to reduce random mismatches, then manufacturing precision is improved, but area and power consumption increase
Solution Approach 1:
Instead of using a single large mixer with highly matched devices, the system segments the mixing function across multiple smaller mixer stages. Each stage uses smaller, less precisely matched devices, but the collective output through proper phase and weight combination achieves the desired harmonic rejection performance.
Solution Approach 2:
The system changes the operating parameters of each mixer stage, specifically the phase relationship with the local oscillator signal. By operating stages at different phases and applying appropriate weighting factors, the system achieves harmonic rejection through parameter diversity rather than relying solely on precise device matching.
3Reliability
If LO phase accuracy is increased to maintain 180-degree phase difference, then harmonic rejection is improved, but device complexity and power consumption increase
Solution Approach 1:
The system employs periodic phase relationships among the mixer stages, where each stage operates at a specific phase angle that is a multiple of 90 degrees. This periodic phase configuration creates a predictable pattern of harmonic cancellation that is easier to implement and control compared to requiring precise continuous phase adjustment.
Solution Approach 2:
Multiple mixer stage outputs are merged through a summation network that combines the signals with appropriate weighting. This merging process integrates the outputs from stages operating at different phases, achieving harmonic rejection through constructive and destructive interference patterns rather than relying on a single precise phase relationship.
4Reliability
If stricter tolerances are applied to mixer components, then harmonic rejection performance is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The system achieves harmonic rejection by controlling operational parameters (phase angles and weighting factors) rather than relying solely on tight manufacturing tolerances of physical components. This approach allows for more relaxed manufacturing tolerances while maintaining performance through software or circuit-level parameter adjustment.
Solution Approach 2:
The system uses dynamic phase and weight adjustment in the mixer stages to compensate for component variations. Rather than requiring all components to be statically precise, the system dynamically adjusts the phase relationships and weighting factors to achieve the desired harmonic rejection, making the system more tolerant of manufacturing variations.
Data Source
AI summary
In one embodiment, the present invention includes a method for receiving a radio frequency (RF) signal and mixing the RF signal with a master clock to obtain a mixed signal, cyclically rotating the mixed signal to each of N gain stages for at least one cycle of the master clock, and summing the outputs of the N gain stages to provide an output signal.