Description:
This Quad, 24:1 RF switch
matrix was built for a multi channel biological specimen
impedance meter. The eight layer PCB was designed with
Coplanar waveguide over groundplane and Stripline techniques
for very low crosstalk and low loss performance. One of the
key tasks of this design was to minimize the path loss as
test signals would be "bounced" off the biological specimen
and return to the analyzer. Any path loss tends to reduce
the signal to noise ratio. Other key design tasks were:
Strict adherence to existing system mechanical dimensions
and 144 pin, CPLD design to control the 96 relays and
provide a backwards compatible control of the 8 bit parallel
interface.
- Quad, 24:1, 50 ohm, RF
multiplexer design
- DC to 110 MHz frequency
range.
- Greater than 25 dB port
return loss.
- Less than 1.5 dB path
loss from DC-110 MHz.
- High third order
intercept point (> 70 dBm).
- Mechanical, reed-relay
switch matrix design for very low insertion loss.
- 8 bit parallel, ribbon
cable interface includes proper termination since the
controller is 10 feet away.
- 144 pin, CPLD used to
control the 96 relays and provide a backward compatible
control method to a previous design.
- CPLD coding in Verilog
using Xilinx design tools.
- Also designed a full PC
controlled, GUI driven software and test fixture for
independent test and verification.
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