Design, Development and Analysis of High-Frequency Dual-Band 4 × 1 Monopole Array Antenna

A circular ring structure monopolar printed antenna for Doppler and automotive radar systems (24 GHz) is designed with a size of 1.4λ₀ × 1.4λ₀ × 0.095λ₀ mm³ observing |S₁₁|> −20 dB, B.W. of 1.8 GHz and a peak gain of 5.1 dBi. This antenna upgraded initially into 2 × 1 and finally 4 × 1 array, having resonant frequencies at 24 GHz and 28 GHz, respectively. A peak gain of 7.12 and 7.16 dBi through 2 × 1 and 9 and 8.65 dBi through 4 × 1 array is observed at respective operating frequencies. Finally, the 4 × 1 array antenna with the tapered feed of size 4.4λ₀ × 2.2λ₀ × 0.095λ₀ mm³ having |S₁₁|≤ 40 dB at ISM-III (24 GHz) and |S₁₁|≤ −30 dB at 5G (28 GHz) with B.W. of 0.77 GHz and 5.1 GHz, respectively, is proposed, qualifying the obtained measured results. Isolation between each antenna element for the 4 × 1 array is ≤ −20 dB with a maximum value of −65 dB. The ECC observed between antenna elements is less than 0.045 and DG is 10. An equivalent circuit is also evaluated for the proposed antenna. The quantification results present that the developed array antenna has excellent performance over the dual band.