Dual-Conversion Doppler Beamformer for Low-Noise RF Acquisition
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Solution Overview
Problem
Conventional phased array ultrasound systems face challenges in low-noise Doppler data acquisition due to high 1/f noise and limited dynamic range, particularly in CW Doppler mode, which degrades the signal-to-noise ratio (SNR) and increases system noise floor, making it difficult to distinguish between blood flow signals and clutter.
Innovation Solution
A dual-conversion Doppler beamformer system that translates RF signals to an intermediate frequency (IF) above the 1/f corner frequency, aligns phases of IF signals, and coherently sums them, followed by downconversion to baseband, reducing flicker noise and improving SNR by operating above the 1/f noise range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional baseband beamforming is used, then the system is simple to implement, but high 1/f noise degrades the signal-to-noise ratio and increases the noise floor
Solution Approach 1:
The patent introduces an intermediate frequency (IF) stage between the RF input and baseband output. The IF frequency is specifically chosen to be above the 1/f corner frequency, serving as a mediator that avoids the high noise region while still enabling coherent beamforming. This intermediate stage acts as a buffer that separates the RF signal processing from the baseband processing, allowing the system to operate in a lower noise frequency region.
Solution Approach 2:
The patent changes the operating frequency parameter from direct baseband (0 Hz) to an intermediate frequency above the 1/f corner. By adjusting this frequency parameter, the system exploits the noise spectrum characteristics where 1/f noise decreases at higher frequencies, thereby improving the signal-to-noise ratio for Doppler measurements while maintaining coherent beamforming capabilities.
2Measurement precision
If CW Doppler mode is used to detect high velocity blood flow, then the detection capability is improved, but the dynamic range is limited due to clutter interference
Solution Approach 1:
The IF stage serves as an intermediary that enables the system to process CW Doppler signals with extended dynamic range. By operating at an intermediate frequency above the 1/f corner, the system can maintain sensitivity to high-velocity blood flow while reducing the impact of low-velocity clutter, thereby extending the effective dynamic range of the Doppler measurement system.
3Use of energy by moving object
If low-voltage operation is implemented to improve power efficiency, then energy consumption is reduced, but the dynamic range is limited
Solution Approach 1:
The patent changes the frequency operating parameter to an intermediate frequency above the 1/f corner, which allows the system to achieve extended dynamic range even under low-voltage operation. This parameter change enables low-voltage circuits to operate effectively by exploiting the improved signal-to-noise ratio at the intermediate frequency, thereby maintaining power efficiency while overcoming the dynamic range limitation.
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 proposed system achieves a wide dynamic range, lower cost, higher power efficiency, and improved SNR, enabling more effective Doppler data acquisition with reduced noise interference and increased sensitivity to blood flow signals.
Implementation Method 1
each of a plurality of RF signals is translated to an intermediate frequency (IF) by a mixer that modulates the RF input by a local oscillator clock (LO), IF is higher than the corner frequency, fC
Implementation Method 2
The frequency of this oscillation is different from the transmit frequency because of the Doppler shift, which is proportional to the component of the blood velocity along the phase gradient of the combined transmitter and receiver beams
Data Source
AI summary
An ultrasonic low-noise analog beamformer for Doppler acquisition achieves high sensitivity by translating the frequency of the ultrasound echoes to an intermediate frequency, which is well above of the 1/f corner. This is accomplished by beamforming the downconverted RF signals instead of using their baseband representation. The baseband conversion, succeeding the beamformation, also incorporates the steps of clutter filtering and anti-aliasing. The invention is particularly suitable for low-voltage process technologies that support broadband applications.