Single-Channel I/Q Demodulation with Discrete Phase Rotation
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Solution Overview
Problem
Current Doppler measurement systems are non-directional, unable to distinguish between motion towards and away from the transducer, and require complex and costly demodulation techniques and hardware, such as multiplexer arrays and delay line circuits, which are cumbersome and power-intensive.
Innovation Solution
Implementing a phase shift in a single channel I/Q demodulator using discrete phase rotation, achieved through mixers and summing circuits, and optionally utilizing quadrant select circuits to simplify the system, allowing for efficient phase rotation in discrete steps rather than continuous phases, reducing the complexity and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrature demodulation with I/Q mixers is used to determine direction of motion, then directional measurement capability is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent segments the continuous phase rotation function into discrete phase steps (e.g., 0°, 45°, 90°, 135°, etc.). Instead of using complex continuous phase shifters, the system divides the phase rotation into a finite number of discrete levels that can be selected via simple switching mechanisms, thereby reducing demodulator complexity while maintaining directional measurement capability.
Solution Approach 2:
The patent changes the parameter of phase rotation from continuous to discrete values. By quantizing the phase shift into specific discrete steps, the system achieves directional information extraction with simpler hardware components, reducing both device complexity and power consumption while preserving the essential quadrature demodulation functionality.
2Adaptability or versatility
If multiplexer arrays and delay line circuits are used for beamforming, then beamforming capability is improved, but power consumption and device complexity increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex multiplexer arrays and delay line circuits from the beamforming system. By removing these power-intensive components and replacing them with discrete phase rotation in a single-channel demodulator, the system maintains beamforming capability through simplified architecture, significantly reducing power consumption.
Solution Approach 2:
The patent merges the functions of multiple elements (multiplexers, delay lines, phase shifters) into a single integrated discrete phase rotation mechanism. This consolidation eliminates redundant components and their associated power consumption while achieving the same beamforming objectives through unified signal processing.
3Adaptability or versatility
If multiplexer arrays and delay line circuits are used for beamforming, then beamforming capability is improved, but device complexity increases
Solution Approach 1:
The patent segments the beamforming function into discrete phase steps that can be selected through simple switching, eliminating the need for complex multiplexer arrays and delay line circuits. This segmentation approach maintains beamforming versatility while dramatically reducing hardware complexity.
Solution Approach 2:
Instead of using the conventional approach of complex multiplexer arrays and delay lines to achieve beamforming, the patent inverts the approach by using discrete phase rotation in a single-channel demodulator. This inverted architecture achieves the same beamforming capability with significantly reduced complexity.
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
This approach enables directional Doppler measurements with reduced system complexity and power consumption, improving beamforming capabilities while maintaining effective signal processing for continuous wave Doppler signals, particularly in ultrasound and radar applications.
Implementation Method 1
the demodulator includes two mixers 22 and 26 which mix the Rx signal with an in-phase ('I') clock signal from the master oscillator, and a quadrature ('Q') clock signal that is phase shifted (90 degrees) from the I clock signal
Implementation Method 2
a first phase rotator 66 generates a first pair of phase rotated components by multiplying each of the I' and Q' signals by a first pair of weighting scalars, respectively, wherein the first pair of weighting scalars corresponds to a selected amount of phase rotation
Implementation Method 3
a first summing circuit 62 generates an I(t) output signal by summing the in-phase components of the first pair of phase rotated components, and a second summing circuit 64 generates a Q(t) output signal by summing the quadrature components of the first pair of phase rotated components
Implementation Method 4
The Doppler effect causes the frequency of a wave reflected from a moving object to shift relative to the frequency of the wave directed at the object. The amount of frequency shift is determined by the speed of the object.
Data Source
AI summary
A quadrature demodulator preweights an input signal prior to mixing with in-phase and quadrature clock signals. In an implementation with discrete phase rotation, a series of weighting circuits may be arranged before or after a select circuit to select the amount of phase rotation. Various implementations may include ratioed current mirrors to perform the weighting function, a stacked arrangement of mixers, an H-bridge input stage, integrated mixers and select circuits, and/or selectable gain stages such as gm cells to perform the weighting function.