Low Cost, Wide Bandwidth Microstrip Signal Switching System for ATE Applications

ATE signal switching systems are subject to ever wider signal switching bandwidths and higher levels of adjecent channel isolation requirements. With the MATE Guidelines, the specified channel-to-channel isolation at the ATE Interface has been set to 50 dB at 300 MHz. Present methods to realize these bandwidth and isolation requirements in ATE station switching systems often include the use of coaxial switches. Coaxial cable connects these coaxial switches to each other, and to the ATE Interface connector pins. The coaxial switches are expensive. In addition, the assembly exgenses associated with building the coaxial cables are also major cost factors when building these ATE signal switching systems. This paper describes how microstrip transmission llnes, connecting mercury wetted reed relays to each other and to the ATE Interface connector pins were used to make a prototype low cost, 350 MHz bandwidth, 50 ohm impedance signal switching system. This prototype microstrip switching system had a measured signal bandwidth equivalent to, or exceeding that for a comparable coaxial relay, signal switching system in present use. In addition, this microstrip signal switchinq system can be assembled using wave soldering fabrication methods to further reduce the labor costs normally incurred to assemble the coaxial cables. This type of mercury-wetted reed relay, microstrip switching system can replace a coaxial-switched signal matrix within a Honeywell H3500 ATE station. Cost reduction of $20,000 per station is anticipated.