MEMS Probe Attenuator Circuit for Low-Parasitic High-Bandwidth Switching
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Solution Overview
Problem
Existing test equipment relies on large and power-consuming electromechanical relays and mechanical switches, which introduce parasitic capacitance, limit bandwidth, and require frequent maintenance, making them unsuitable for high-speed switching and accurate signal attenuation.
Innovation Solution
The integration of micromachined switches and attenuators within test equipment probes reduces parasitic capacitance by using MEMS technology, allowing for precise signal attenuation and increased bandwidth, with the option of fabricating or attaching components on a common substrate or printed circuit board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical relays are used to switch attenuators, then signal attenuation can be achieved, but parasitic capacitance increases and bandwidth is limited
Solution Approach 1:
The patent replaces electromechanical relays with solid-state field-effect transistor (FET) switches to eliminate mechanical moving parts. This substitution removes the parasitic capacitance associated with mechanical contact structures while maintaining the signal attenuation function through electronic switching of FET-based attenuator circuits.
Solution Approach 2:
The patent changes the switching mechanism from mechanical/electromechanical to solid-state electronic switching using FETs. This parameter change in the switching technology enables lower parasitic capacitance values and higher bandwidth operation while preserving the attenuator switching capability.
2Adaptability or versatility
If electromechanical relays are used for switching, then attenuator selection is possible, but switching speed is limited
Solution Approach 1:
The patent replaces slow mechanical relay switching with fast solid-state FET switching. The FET-based switches can operate at much higher frequencies and switching speeds compared to electromechanical relays, enabling rapid attenuation level changes while maintaining the ability to select different attenuator values.
3Reliability
If electromechanical relays are used, then circuit switching is achieved, but power consumption increases
Solution Approach 1:
The patent replaces power-hungry electromechanical relays with low-power solid-state FET switches. FETs exhibit very high input impedance and consume minimal power during switching operations, thereby maintaining the circuit switching function while dramatically reducing overall power consumption of the attenuator switching system.
4Adaptability or versatility
If mechanical switches are used, then attenuator selection is possible, but maintenance requirements increase
Solution Approach 1:
The patent replaces mechanical switches requiring contact cleaning and maintenance with solid-state FET switches that have no mechanical contacts. The solid-state nature of FETs eliminates wear, contact degradation, and contamination issues, thereby maintaining attenuator selection capability while eliminating routine maintenance requirements.
Data Source
AI summary
One or more micromachined (MEMS) switches switch attenuators, such as resistors, into or out of a signal path, such as of a test instrument. The MEMS switches can be fabricated on the same substrate as the attenuators, or the switches or attenuators can be mounted on the same substrate as the others are fabricated. An instrument probe includes attenuators and MEMS switches that are controlled by the instrument and/or by a control circuit in the probe. Optionally, the probe includes reactive elements, such as capacitors, and MEMS switches to compensate for electrical characteristics of the probe and/or probe lead, and the probe or a test instrument automatically sets the MEMS switches to connect appropriate ones of the reactive elements to a signal path within the probe.