Agilent Measurement Journal - Issue 5 - 2008 - (Page 66)

Operating life of an EM switch The operating life of an EM switch is deﬁned as the number of cycles the switch will complete while meeting all RF and repeatability speciﬁcations. Operating life also refers to the electrical life of the switch, as opposed to the mechanical life, which is signiﬁcantly longer. One life cycle is deﬁned as one closing and opening of the jumper contact — sometimes referred to as switch blade — or one on/off triggering of the electromagnetic coils in the switch. The operating life is very dependent on the jumper contact mechanism, contact resistance, and the material and plating used in all the key RF components. See Figure 3 Push rod Jumper contact Center conductor Center conductor Figure 2. RF line closed Examining the conventional switchcontact mechanism Conventional switches function by moving the jumper contact — a thick rectangular element — inside the RF housing. The jumper contact is joined by a push rod, generally made of a dielectric material such as polystyrene (PS), which moves inside an access hole in the RF housing. The tip of the jumper contact is pressed directly onto the ﬂat surface on the tip of the connector’s center conductors by a mechanical spring force from the actuator. Figure 1 depicts an open RF line with the jumper contact retracted. Figure 2 illustrates a closed RF line in which the jumper contact forms a bridge between the input and output ports, thereby allowing propagation of the RF signal between these ports. The jumper contact is usually thick and inﬂexible, as illustrated in Figure 3. The vertical motion of the jumper contact and push rod during the opening and closing sequences results in what is sometimes called “frictionless switching” because there is no friction produced between the jumper contact and the center conductor. Contact pressure Inﬂexible tip Flat surface Jumper contact Center conductor Push rod Jumper contact Figure 3. Conventional EM switch mating architecture Center conductor Center conductor Although this design allows mechanical actuations on the order of tens of millions of cycles, there are some signiﬁcant drawbacks. The continuous impact between the jumper contact and center conductor will gradually result in increasing wear and tear, producing some debris. This debris, along with dirt and contamination accumulated over time, remains on the tip. As a result, contact resistance increases over time, leading to increased insertion loss. This may or may not result in the switch Figure 1. RF line opened 66 Agilent Measurement Journal

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 5 - 2008

Agilent Measurement Journal Issue 5 Finding a New Path when Assumptions Break Down Contents Testing MIPI D-PHY Protocols Oscilloscope Firmware Update DNA Replication Joining the LTE/SAE Trial Initiative Testing Proteins Praise for DC Power Analyzer Scripting Features for AMDS Testing Hybrid PCBA Systems Improving the Gene Expression System Workflow Turning a “Good Enough” Test Strategy into One That’s Reliable, Repeatable and Traceable Understanding the Effects of Limited-Bandwidth Channels on Digital Data Signals Introducing the 3GPP LTE Downlink Validating the 26 Validating the Physical and Protocol Layers in DDR Memory Interfaces Understanding Total Jitter Measurements of Low Probabilities Using Behavioral-Model Simulation to Accurately Predict First-Order PLL Performance Creating Synchronous High-Frequency Sampling across Multiple Digitizers Overcoming the Challenges of Testing FlexRay Networks Understanding Operating Life and Repeatability of Electromechanical Switches and their Effect on Total Cost of Ownership Implementing Micro and Nano LC/MS Techniques for High Sensitivity Lipidomics Analysis

Agilent Measurement Journal - Issue 5 - 2008

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