Microwave Engineering Europe - October 2008 - (Page 33)

RF ATE 33 the attenuators or the switching function. In the DSA, for example, it is important to have accurate signal amplitude and phase, so that the rest of the instrument knows the correct signal level. Unfortunately, the transient settling time in GaAs high-performance switches is unpredictable, which makes “designing and manufacturing around” them very challenging for ATE companies. Using an alternative device, such as a silicon switch, eliminates these design issues. To date, only UltraCMOS silicon-on-sapphire technology (SOS) has been able to support these stringent requirements in the switching function.[1] Low frequency performance and linearity Test and measurement equipment beneﬁts from offering broadband performance, making it a more attractive investment to handle multiple communication protocols. As a result, the components inside must also be broadband. Many GaAs switches are speciﬁed to operate from DC and up. GaAs switches have a typical corner frequency of 100 MHz; operating below this corner frequency signiﬁcantly degrades linearity and introduces noise ﬁgure problems. Today, designers can use Figure 4: A switch manufactured using silicon-on-sapphire a single switch that offers UltraCMOS processing demonstrates a ﬁnal settling time of high performance in the 13 µs with no overshoot. kilohertz range all the way up to 7500 MHz. For example, the PE42552 SPDT switch operates from 9 kHz up to 7500 MHz with high linearity performance across the frequency range. Linearity at lower frequencies drives the ability of a switch to be used as a broadband component. Generally speaking, any nonlinearity from components in the test and measurement equipment can cause intermodulation distortion (IMD), which can ESD protection inhibit the equipment’s ability to provide an Typical GaAs MESFET switches have a Class accurate measurement. This is particularly 0 (<250 V) or Class 1A (250 V to 500 V) challenging when the linearity of the IC in HBM ESD rating and can be damaged by even the ATE is as good as (or worse) than that small electrostatic discharge (ESD) events. of the device under test. As a result, ATE This type of damage can be particularly designers demand the very best linearity challenging to detect, so it is best to avoid it. available. Figure 5 shows the PE42552 has In response, ATE designers have traditionally signiﬁcantly better performance than a GaAs added ESD protection to switches. MESFET switch at low frequency. Unfortunately, this external protection can discovr mor dtails mms.structurs.snsors.olds.acclromtrs.nanowirs. e08_MiEnEu210x140_micna_E.indd 1 Microwave Engineering ● October 2008 ● 02.07.2008 10:19:31 Uhr www.mwee.com 032-035_MWEE.indd 33 2/10/08 13:42:56 http://www.mwee.com

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Microwave Engineering Europe - October 2008 Contents Comment News Cover Feature: AWR's AXIEM Software Brings 3D Planar Electromagnetic (EM) Simulation "Up Front" RFID: Augmented Reality: Beyond RFID and QR Codes for Mobile Phone Platforms Filters & Frequency Synthesis ZigBee Goes Green with Support for Smart Energy Simplify Mobile Data Applications and Services Test Enabling the State-of-the-Art in Automatic Test Equipment National Physical Laboratory Test Facility Aids Development of Next-Generation Antennas Selecting the Synthetic Test Environment for Transmit-Receive (T-R) Modules in a Phased Array Radar System Products Calendar

Microwave Engineering Europe - October 2008

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