Diode Bridge Filter Circuit for Ultrasonic Imaging Signal Separation
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Solution Overview
Problem
Ultrasonic imaging devices face challenges in efficiently filtering test pulses from reflected signals, leading to power dissipation and noise issues, particularly in portable devices where power conservation is crucial.
Innovation Solution
The use of a diode bridge with diodes having forward transit times greater than a predetermined value ensures the filter circuit has an impedance of substantially zero within a specific frequency range, allowing efficient passage of reflected signals while minimizing power dissipation and noise, by operating in a mode where the ON resistance is independent of the bias current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional filtering methods are used to separate test pulses from reflected signals, then signal separation is achieved, but power dissipation increases and noise is introduced
Solution Approach 1:
The patent changes the impedance parameter of the filter circuit by using a diode bridge configuration that provides substantially zero impedance within a specific frequency range. This parameter change allows the reflected signals to pass through efficiently without power dissipation while still filtering out test pulses through the frequency-dependent impedance characteristics
Solution Approach 2:
The patent replaces conventional active filtering components (such as operational amplifiers and capacitors that consume power) with a passive diode bridge circuit that operates based on the nonlinear characteristics of diodes. This substitution eliminates the need for external inductors and reduces power dissipation while maintaining signal quality
2Reliability
If conventional filter circuits are used, then test pulses are filtered from reflected signals, but external inductors are required and device complexity increases
Solution Approach 1:
The patent merges the filtering function with the existing diode bridge structure used in the ultrasonic imaging system. The diode bridge, which is already present for other purposes, is configured to simultaneously perform signal separation by providing frequency-dependent impedance, thereby eliminating the need for separate external inductor components
Solution Approach 2:
The diode bridge circuit is designed to serve multiple functions: it acts as a rectifier for the ultrasonic signals and simultaneously functions as a filter that separates test pulses from reflected signals based on frequency. This multi-functionality reduces the overall device complexity by eliminating dedicated filtering components
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 reduces power dissipation by up to a factor of 10 and enhances power supply rejection ratio, enabling efficient ultrasonic imaging without the need for external inductors, thus improving the performance and efficiency of portable imaging devices.
Implementation Method 1
Diodes of the diode bridge have forward transit times that are greater than one divided by a product of 2π and a minimum value of a predetermined frequency range. An impedance of the filter circuit is equal to substantially zero when the reflected signal is within the predetermined frequency range
Data Source
AI summary
A filter circuit for an imaging device including a probe configured to propagate an ultrasonic wave through an object includes a diode bridge configured to receive, from a transducer of the probe, a composite signal that includes a test signal and a reflected signal. The reflected signal corresponds to reflected waves sensed by the transducer in response to the ultrasonic wave propagated through the object. The diode bridge is further configured to block the test signal from the composite signal and pass the reflected signal. The filter circuit further includes an output node configured to output the reflected signal and a first node and a second node that connect the diode bridge to a bias voltage. The bias voltage causes a bias current to flow from the first node to the second node through the diode bridge.