Variable Dielectric Delay Lines in Liquid Crystals for Phased Array Feeds

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In this project we seek to exploit a novel liquid crystal technology, whichallows a controllable true time delay to be applied to an RF signal offrequencies up to tens of Giga-Hertz. The basic technology has already beendemonstrated and has a wide variety of applications. We now intend to use thistechnology to construct a real astronomical demonstration system for delaylines and show that these can be integrated into the beam-forming module of anexisting Phased Array Feed (PAF) instrument, dramatically improving itscapabilities. PAFs are an essential next step for radio astronomy. They offer thepossibility of increasing a telescope's Field-of-View (FoV), ofimproved calibration and of allowing operation up to higherfrequency. PAFs have been implemented in instruments such as PHAROSand can achieve these goals, but over a narrow bandwidth due to theuse of phase shifters in the beam-former hardware. In this project weseek to implement a true time delay beam-former, which will allow thewhole available bandwidth to be used. This will make use of noveltechnology - liquid crystal stripline whose dielectric constant canbe varied by application of an AC voltage. We propose a two yearprogramme during which we will produce a PAF module using a set oftrue-time delay units that will be tested within the PHAROS receiver,which is available for use on this project and will make an idealtest-bed. Our focus is on demonstrating the Technology Readiness Levelof these delay lines in the context of a prototype instrument, therebyaddressing integration issues as well as pure technology development.