Compact Tetracyclic Nested AMC-Backed Multiband Antenna With High OoB Rejection and Enhanced Gain Radiation for IIoV-Based Sensing and Communication

An innovative artificial magnetic conductor (AMC)-backed quad-band antenna is proposed with gain enhancement, high Out-of-Band (OoB) rejection, forward radiation improvement, and backward radiation reduction for Intelligent Internet of Vehicle (IIoV)-based sensing and communication. It includes a quad-band microstrip radiator and a tetracyclic nested AMC as a reflector. The radiator has a radiating pattern of slotted octagonal patch connected to a rectangular resonant loop, and a meshed defected ground structure (MDGS). The mechanism of resonant frequency generation is derived and analyzed. Then, an AMC reflector with four zero-phases in the reflection coefficient is designed and its equivalent circuit model is established. The AMC unit cell consists of four nested rings and two lumped capacitors. It generates four in-phase reflection bands, which are coincident with the four frequency bands of the radiator. The quad-band antenna gains are enhanced while its profile maintains low due to the in-phase reflection characteristics of the multiband AMC reflector. To verify the design concept, a prototype with a total size of 95 mm
$\times101$
mm
$\times21.2$
mm is fabricated and measured. The measured 10-dB impedance bandwidths are 2.19–2.54 (14.8%), 3.06–5.25 (52.7%), 6.43–6.96 (7.9%), and 7.71–8.29 (7.3%) GHz, respectively. High OoB rejections between each band reduce electromagnetic interference to feed into radiofrequency circuits. The measured gains and radiation efficiencies range from 3.6 to 8 dBi and from 57.8% to 92%, respectively.