Design of planar microstrip array in ku band for analog-digital beamforming

For some radar applications it is desired to design a phased array with fixed shaped beam in the elevation plane and scanning capability in the azimuth plane using digital beamforming. Depending on the azimuth scan range, the element spacing is limited by the grating lobe condition. When other design requirements such as narrow beamwidth. low beam squint, low elevation side lobe level (SLL). and high radiation efficiency are desired, the design of the antenna array and passive beamforming network becomes challenging. Microstrip technology is a desired option due to the compact size and low cost. To meet size requirements and avoid undesired radiation, the antenna array and the passive feed network need to be on different layers, with a thick substrate for antenna array and a thin substrate for feed network. In addition, when low beam squint is required, corporate feed is the optimum option but it takes a large space for a large array.