Abstract:

Microstrip comb antennas typically adopt parallel microstrip arrangements and are well suited for large-scale array designs because of their fixed element spacing and compact size. However, the bandwidth of comb arrays is often constrained by the resonant characteristics of microstrip lines, and the linear arrangement of elements can easily result in high cross-polarization levels. Microstrip grid array antennas, through symmetric element configurations and coupling design, can achieve flatter gain and broader impedance bandwidth. Furthermore, optimization of the element layout and feed network effectively suppresses sidelobes, improves polarization purity, and reduces transmission loss. This paper proposes a K-band array antenna that integrates a series-fed receiving and a series-parallel-fed transmitting antenna, employing Rogers RO5880 substrate with a dielectric constant of ε_r=2.2. A Chebyshev amplitude distribution is employed to realize non-uniform excitation of the elements for sidelobe reduction. Measurement results demonstrate that within the 23.0~24.3 GHz band, the antenna achieves an overall gain of 23.4 dBi, with a 3 dB gain bandwidth covering 23.02~24.08 GHz. The inter-array isolation remains below –46 dB across the operating band. At a center frequency of 23.5 GHz, the E-plane and H-plane sidelobe levels are both below –15 dB, indicating suitability for dense applications such as automotive radar, short-range high-data-rate communications, and 5G base stations.

Key words: K-band, microstrip grid antenna, gain flatness, high isolation, sidelobe reduction