Astrophysics Group

Cavendish Laboratory

Variable Dielectric Delay Lines in Liquid Crystals for Phased Array Feeds

In this project we seek to exploit a novel liquid crystal technology, which allows a controllable true time delay to be applied to an RF signal of frequencies up to tens of GHz. The basic technology has already been demonstrated and has a wide variety of applications. We now intend to use this technology to construct a real astronomical demonstration system for delay lines and show that these can be integrated into the beamforming module of an existing Phased Array Feed (PAF) instrument, dramatically improving its capabilities.

PAFs are an essential next step for radio astronomy instrumentation.  They offer the possibility of increasing a telescope’s Field-of-View as well as improving calibration capability and allowing operation up to high frequencies.  PAFs have been implemented in instruments such as PHAROS and can achieve these goals, but over a narrow bandwidth due to the use of phase shifters in the beamformer hardware.  In this project we seek to implement a true time delay beamformer, which will allow the whole available bandwidth to be used. This will make use of novel technology: liquid crystal stripline whose dielectric constant can be varied by application of an AC voltage.

Within a two year programme, we will produce a PAF module using a set of true-time delay units that will be tested within the PHAROS receiver, which is available for use on this project and will make an ideal test-bed. Our focus is on demonstrating the Technology Readiness Level of these delay lines in the context of a prototype instrument, thereby addressing integration issues as well as pure technology development.

VDL