Rotating Harmonic Rejection Mixer for Mismatch-Tolerant RF Mixing
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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 and weighted gain stages to combine outputs, reducing harmonic rejection issues while minimizing power and area consumption by shifting device matching problems to lower frequency passive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple mixer stages are used with device matching to achieve harmonic rejection, then harmonic rejection performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The mixer is divided into multiple stages, each handling a specific frequency component. By segmenting the mixing function across stages with different LO frequencies, the system achieves harmonic rejection without requiring all stages to be perfectly matched, thus reducing overall device complexity while maintaining performance.
Solution Approach 2:
The invention changes the operating parameters of each mixer stage by using different local oscillator frequencies and phases. This parameter differentiation allows each stage to process specific spectral components, achieving harmonic rejection through parameter diversity rather than through complex device matching.
2Manufacturing precision
If device sizes are increased to reduce random mismatches, then manufacturing precision is improved, but area and power consumption increase by a factor of 4
Solution Approach 1:
Instead of using one large device, the function is segmented across multiple smaller devices operating at different parameters. This segmentation allows each device to be small while the collective system achieves the required precision through parameter diversity and signal processing.
Solution Approach 2:
The patent introduces intermediate processing stages that compensate for device mismatches through signal manipulation rather than requiring perfectly matched devices. This intermediary processing allows smaller devices to achieve the same effective precision as larger devices would provide alone.
3Reliability
If LO signals are made exactly 180 degrees out of phase for harmonic rejection, then harmonic rejection is improved, but additional well-matched components are required increasing device complexity
Solution Approach 1:
Rather than relying on precise 180-degree phase relationships between components, the invention changes the approach by using multiple LO frequencies and phases in a time-division manner. This parameter change eliminates the need for precisely matched phase relationships while achieving the same harmonic rejection goal.
Solution Approach 2:
The system uses periodic switching between different mixer stages, each operating with different LO parameters. This periodic action in the time domain replaces the need for continuous precise phase relationships, reducing component matching requirements while maintaining harmonic rejection performance.
4Reliability
If operation is performed at higher frequencies to achieve desired performance, then harmonic rejection is improved, but power consumption increases
Solution Approach 1:
The system performs mixing operations periodically at lower frequencies by switching between multiple stages. This periodic operation at reduced frequencies achieves the same spectral processing as continuous high-frequency operation would provide, but with lower instantaneous and average power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves improved harmonic rejection with reduced power and area consumption, allowing for dynamic control of harmonic rejection based on incoming signal frequency and preventing flicker noise, while maintaining noise immunity and image rejection.
Implementation Method 1
the mixer typically multiplies the incoming wireless signal with a local oscillator signal to produce a signal that has spectral energy that is distributed at sums and differences of the local oscillator and incoming signal's frequencies
Implementation Method 2
a rotating switch to cyclically switch the mixed signal to a plurality of individual gain stages
Implementation Method 3
individual gain stages to weight the mixed signal for a respective time interval
Implementation Method 4
a combiner to combine outputs of the individual gain stages to provide a mixed signal
Data Source
AI summary
In one embodiment, the present invention includes a mixer circuit to receive and generate a mixed signal from a radio frequency (RF) signal and a master clock signal, a switch stage coupled to an output of the mixer circuit to rotatingly switch the mixed signal to multiple gain stages coupled to the switch stage, and a combiner to combine an output of the gain stages.