Design of hollow patch microstrip reflectarray and measuring phase of reflection coefficient at Ka-band using waveguide simulator

The key issue in the design of a MRA antenna is the technique used to obtain the required phase shift in the field reradiated by different elements. In the past many solutions have been proposed. Stub loaded patches, patches of variable sizes and identical patches with variable rotation angles are the most popular techniques. A technique was introduced at IRCTR (International Research Centre for Telecommunications and Radar) which is based on patches with slot of different sizes. The slot changes the resonant frequency of each element of the array, which in turn gives a change in the phase of the reradiated field. The analysis was first carried out on a 32.5GHz single element and then extended to large arrays of finite dimensions, at the same frequency. Some of these arrays were manufactured and their performance measured. A waveguide simulator exploiting the concept of infinite array is successfully implemented in the characterization of reflected phase. A hollow patch antenna at Ka-band is encapsulated between two air-filled waveguide and its phase-frequency curve is measured. A comparison of the simulations using method of moment and the measurement results show a good agreement. The phase variation is in the range of +160° to -160° for a frequency sweep from 26 to 38GHz.