Electrically Controllable Liquid Artificial

New work is reported on eltic field cmrtrofied fiqoid dielectrics demonstrating theff application in control devices at 35 and 95 CX-fz. Liquid artMciai dielectric design approaches and performance pre- diction are afso dfseuss@ with empfnmis on electronic beam steering of mfltimeter-wave antemas. References are included listing much of the prior work done in this ares. L lNTRODUCTION T' HERE HAS BEEN a continuing awareness for several decades that many military radar and seeker systems would benefit greatly in performance if fast, sim- ple electronic scanning antennas were available. It has proven quite difficult and costly, especially in the millime- ter-wave region, to implement inertialess-scanning anten- nas. In the late 1960's, two classes of microwave liquid artificial dielectrics were invented in the hope of overcom- ing the problems inherent in conventional approaches to antenna beamsteering (1 )-(6). The liquids were designed to change permittivity in response to an applied electric control field. This property allowed analog delay-type phase shifters and dielectric prisms with electrically controllable refrac- tion to be built at high microwave frequencies. Extremely high-power handling capacities and short response times were achieved under laboratory conditions with some liquids in 360° phase shifter configurations. A typical liquid might require 750-V/cm control field to produce a 30° phase shift per wavelength of path. Control current is negligible. This paper reports new work on controllable liquid artificial dielectric (CLAD) media, with emphasis on millimeter-wave device applications. Basic principles of operation and liquid dielectric composition are discussed in Section H. Experimental data on new liquid dielectrics useful in the millimeter-wave region are presented in Section HI, and device designs based on CLAD media are treated in Section IV.