Design of an Interface Layer Using CPW between an Array Antenna and TRM in X-Band Radar Systems to Minimize Leakage Fields and Improve Transmission Characteristics

In this paper, we propose an interface layer using the coplanar waveguide (CPW) between an array antenna and transmitting receiver modules (TRMs) for X-band military ship radar systems. To improve transmission characteristics, the interface layer with the CPW has three transition parts: Transition part A is between the sub miniature push-on (SMP) connector and the interface layer. Transition part B is the CPW in which the thickness gradually increases. Transition part C is for connecting the interface layer and the antenna. The measured reflection and transmission coefficients of the fabricated interface layer are −22.4 dB and −0.82 dB, respectively. To verify the proposed interface layer, we then apply the layer to a 2 × 2 X-band array antenna and measure the array antenna characteristics, such as reflection coefficients, array antenna gain, and half-power beam widths (HPBWs). The measured reflection coefficient is under −10 dB from 8.6 GHz to 10.2 GHz, and the bore-sight array gain of the 2 × 2 array antenna is 10.5 dBi at 9.5 GHz. In addition, the measured HPBWs under the same conditions are 47.8° and 39.1° in the zx- and zy-planes, respectively. The results demonstrate that the proposed interface layer using the CPW is suitable for X-band radar systems.