Microsemi

Page 9

Copyright

 2005

Rev. 0, 2006-01-17

UM9601 – UM9608

FOR MICROSTRIP 900 MHz ANTENNNA SWITCHES

CO S

OS

AND MICROWAVE APPLICATIONS

Microwave Characterization

The UM9601-UM9608 series has been designed and

characterized as shunt switch elements at frequencies to 4 GHz

in microstrip circuits. Performance curves are given which

demonstrate switch performance in 0.025” (.635mm) alumina

microstrip.

The performance data were derived by evaluating externally

biased microstrip circuits in which a UM9601 diode was

installed. Each circuit consisted of a 1 inch length of 50 Ohm

nominal impedance 0.025” (.635mm) thick alumina microstrip

and two SMA connectors. The data shown include the board

and connector loss. Measurements performed using 00.050”

(1.27mm) alumina substrates show similar performance at

frequencies to1.5 GHz

These circuits simulate SPST switches. Many designs

require multi-throw switches. It is important to recognize that a

multi-throw switch will have 6dB higher isolation than

indicated for SPST switches. Also, a multi-throw switch using

shunt mounted PIN diodes require the diodes be placed a

quarter-wavelength from the common port.

A further improvement in switch performance may be

achieved by using 2 shunt PIN diodes in each arm spaced a

quarter-wavelength from each other. In this case the isolation of

each section will be twice the dB value of the switch. The

insertion loss due to the diodes should be less than twice the

insertion loss of an SPST section due to the transforming effect

of the quarter-wave line on the capacitance of a single diode.