Liquid Crystals (LCs) are promising dielectric media for a range of mm-wave devices. Their main advantage stems from the fact that their dielectric properties can be externally controlled by an electric or magnetic field. As such, LCs have already found some uses in the design of mm-wave devices such as tunable microstrip line phase shifters [1-2]. In [1-2], the phase shifters are simply made of a length of a microstrip line including a LC substrate. Therefore, the amount of the phase shift is dependent on the length of the microstrip line exposed to the LC. This becomes highly impractical when high values of phase shift are required as long length microstrip lines are needed. For example, in  the 50 mm length of the line achieves a differential phase shift of about 90 degrees at 24 GHz, when the LC mixture is K15.
In this paper, for the first time, a new compact Reflective Type Phase Shifter (RTPS) operating in the 60 GHz band is presented. The active medium for the reactance variation of the reflective loads is an LC mixture, commonly referred to as E7. Control of the reactance is achieved by an external, low frequency voltage, conveniently supplied through the CPW probe pads. The measured differential phase shift of this new RTPS is over 130o, while its figure of merit is 11.4o/dB at 61 GHz. One other distinct characteristic of this phase shifter is its small circuit size (only 3.4 x 6.2 mm2 in its present experimental form). The amount of the phase shift achieved using the new RTPS is equivalent to the phase shift obtained with a 15 mm long microstrip line, using the same LC mixture, E7. The fabricated phase shifter and its response are presented in Fig. 1.
 N. Martin, P. Laurent, G. Prigent, P. Gelin and F. Huret, “ Improvement of an inverted microstrip-line microwave phase-shifter using liquid crystal”, 33rd European Microwave Conference (EuMC 2003), pp. 1417-1420, 2003, Munich, Germany.
 S. Mueller, P. Scheele, C. Weil, M. Wittek, C. Hock and R. Jakoby, “Tunable passive phase shifter for microwave applications using highly anisotropic liquid crystals”, IEEE, MTT-S Int. Microwave Symp.Dig., pp. 1153- 1156, 2004.