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10/25/2005 |
Microsemi Introduces MRI Industry\'s First Switching Dual Diodes Module |
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RF & MMWAVE SCHOTTKY DIODES |
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GC9989 (MMPI) |
Microsemi's Schottky Barrier devices are currently available in the eight junction ring quad configuration. Devices are available in monolithic form for hybrid applications as well as in hermetic or non-hermetic packages. Monolithic devices are recommended for highest frequency, broadband designs. The beamlead design eliminates the problems associated with wire bonding very small junction devices thus improving reliability and performance in MIC applications. Our in house epitaxy process capability insures repeatability for lowest conversion loss through Ku Band. A broad range of unique metallization schemes produce Microsemi's complete line of barrier heights. Diodes are available with barrier heights ranging from 600 mV to 1300 mV per leg. By optimizing epitaxy and metallization, these devices achieve lowest Rs-Cj products resulting in exceptional conversion loss performance. "High Rel" screening is available on packaged devices per your requirements.
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SPECIALTY PIN DIODES |
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UM9989 (MMPI) |
The UM9989 diode series was designed to protect MRI receivers from high RF energy fields including long RF pulses and RF spike pulses present in most MRI machines. The UM9989 acts as a passive protector (limiter) for the MRI receiver. No forward bias voltage is required to turn on the diode. It is self-biased by the RF transmitter pulse power. A switch driver is not needed for this receiver protection application. Receiver protector diodes appear directly across the input port of the receiver. They are connected in anti-parallel pairs to limit the RF carrier excursion in both polarities. They must, therefore, exhibit extremely low insertion loss, both in the “on” state (high power present) and the “off” state (receiver power present) so as not to decrease the receiver’s sensitivity. The UM9989 diodes are available in two package configurations for flexibility in design.
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UMX9989AP (MMPI) |
The UMX9989AP is the first MRI switching diode module, designed to optimize performance and reduce assembly labor, cost, and polarity errors. There are two principle applications for which the UMX9989AP modules are intended: 1) MRI receiver protection from high RF energy fields, including long RF pulses and RF spike pulses present in most MRI machines. The UMX9989AP acts as a passive protector (limiter) for the MRI receiver’s LNA. The diode assembly exhibits extremely low insertion loss, both in the “on” state (high power present) and the “off” state (receiver power present) so the Receiver’s Noise Figure is not increased by the protector circuit. 2) Passive switching of surface coil detuning and blocking circuits. In this case, the flow of loop current during transmitter pulse turns on the diodes, without a switch driver.
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