A Gigahertz Test Fixture for Two Port Passive Devices

Since it is not possible to obtain exact standards for many types of filters, resonators and discrete components, it is necessary to qualify procedures for extraction of device parameters. In addition, the package adds additional parasitics to equivalent circuit models which increases the difficulty of parameter extraction. A procedure has been developed using scattering parameters for extraction of equivalent circuit elements for bulk acoustic wave (BAW) and surface acoustic wave (SAW) crystal filters, and package equivalent circuits from a few megahertz to approximately 1 GHz. This has led to an extension of the EIA-512 standard. In addition, SAW filter parameters may also be extracted using similar S-parameter techniques. In order to accommodate the many differing BAW and SAW package types, a test fixture has been developed for measuring a broad range of packaged devices with varying pin configurations. The test fixture requires simple and easy hardware modifications to accommodate any pin spacings of 100 mils or greater. The test fixture is also able to be accurately calibrated via the twelve term S-parameter error correction model at the insertion point. Scattering parameter data is then taken on 2-port devices and computer programs accurately extract the device parameters. The test fixture will be described and the results of several applications of parameter extraction to various SAW and BAW devices will be shown. A comparison of theoretical and measured SAW filter performance will be presented.