Design of a Multilayer Microstrip Delay Line on a Water Based Composite Dielectric Medium

The physical dimension of a microstrip delay line is known to depend upon the effective dielectric constant of the substrate. A higher dielectric constant is always advantageous for ensuring compact microstrip design while realizing large time delays such as those required for the phasing of antenna arrays at low radio frequencies. In this paper, we describe the design and development of a water-based composite dielectric medium optimized for achieving a higher effective dielectric constant in the frequency range of 30 - 360 MHz. Our tests of a prototype delay line (20 cm long) indicate an effective dielectric constant of a little over 26 with an insertion loss in the range of 0.1 dB to 0.9 dB.