24-GHz Bandwidth-Enhanced Microstrip Array Printed on a Single-Layer Electrically-Thin Substrate for Automotive Applications

A 24-GHz microstrip array antenna is developed on a single-layer electrically-thin substrate to provide a cost-effective solution for automotive applications. By etching two straight slots close to and parallel with the non-radiating edges, the impedance bandwidth of a conventional rectangular microstrip patch is enhanced without affecting its radiation characteristics. To demonstrate the effectiveness of the proposed technique, an 8 * 8 planar array with a specified sidelobe level of 25 dB in both the E -plane and H -plane is studied and prototyped on the commercial substrate RT/duroid 5880 with a thickness of 0.25 mm. The measured impedance bandwidth for VSWR less than 2 is about 1.8 GHz, which corresponds to a relative bandwidth of 7.5%. In addition, the measured gain is 22.5 dBi at the center frequency while it is higher than 21 dBi over a frequency band of 1 GHz. Finally, the measured sidelobe level is 20 dB in the E -plane and 18 dB in the H -plane.