BGO Reflective-Array Compressor (RAC) with 125 Microseconds of Dispersion.
Abstract
Linear FM pulse expanders and compressors in the reflective-array configuration have been fabricated on bismuth germanium oxide substrates. The low surface-wave velocity on this material and the folded RAC configuration allow 125 microseconds of dispersion over the 2.5-MHz bandwidth to be obtained in a compact device. The reflective arrays were depth weighted to provide a flat frequency response in the down-chirp expansion lines and a Hamming frequency response in the up-chirp compression lines. Maximum amplitude deviation from ideal was 0.5 dB. Midband (60 MHz) insertion loss was approximately 33 dB in both types of devices. Reflective arrays ion-beam etched with 500-eV argon ions showed no evidence of surface alteration or anomalous acoutic propagation loss. Phase compensation with Au-on-Cr films yielded a typical residual phase error of 2.0 degree and sidelobes below 33 dB were obtained in a subsystem comprising an expander, compressor, and assoicated electronics. Successful development of the devices depended on solving problems of angular accuracy of the reflective arrays and temperature sensitivity. These problems are especially severe in devices with small fractional bandwidth and large dispersion. (author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 22, 1975
- Accession Number
- ADA031713
Entities
People
- Richard C. Williamson
- Victor S. Dolat
Organizations
- Massachusetts Institute of Technology