Research On Microstrip Planar Transmitarray Antennas

Microstrip transmitarray antennas,which consists of a feeding horn and a planar transmission array with many periodic elements,possess the advantages of reflector antennas and microstrip array antenna.The transmitarray is able to transform the quasi-spherical incident wave emitted from the feeder into the quasi-planar wave,which would form a pencil beam in the designated direction,by adjusting the phase of each unit on the surface of the transmitarray.Microstrip transmitarray antennas,which are of low profile,strong directivity,light weight and ease to manufacture,etc.,and have wide applications in antenna research field,the aerospace and the radar,is becoming a hot research topic of the current antenna research.In this paper,broadband,low profile microstrip transmitarray antennas and polarization converters are in-depth studied.A transmitarray antenna which consists of elements of multi-layer stack structure is proposed in this paper.The effects of the initial phase angle,focus diameter ratio and the beamwidth of the feeder on the transmitarray antenna are analyzed and demonstrated.A novel planar microstrip slot-fed patch antenna feeder instead of a horn has been successfully proposed.The comparison of the measured results of the transmitarray with a planar feeder with that with a horn feeder is conducted.Experimental results show that the transmitarray with a planar source feed achieves a peak gain of 25.1 dBi,a 1-dB gain bandwidth of about 7.3% and a half-power beamwidth of about 5.8°;the transmitarray with a horn feeder achieves a peak gain of 28.4 dBi,a 1-dB gain bandwidth of about 7.4%,and a half-power beamwidth of about 5.1°at the center frequency.The wideband and high-gain performance of both transmitarray antennas are demonstrated.Secondly,a transmitarray antenna which consists of a single dielectric layer with resonant structure is proposed based on an phase compensation element.Fed by a standard horn and a planar slot-fed patch antenna,respectively,simulations and measurements validate the wideband and high-gain performance.Experimental results show that the transmitarray with a planar source feed achieves a peak gain of25.82 dBi,1-dB gain bandwidth of about 6.8% and a half-power beamwidth of about5.4°;the transmitarray with a horn feeder achieves a peak gain of 27.45 dBi,a 1-dB gain bandwidth of about 9.5%,and a half-power beamwidth of about 5.2 ° at the center frequency.Finally,based on the theory of polarization of electromagnetic wave,a crossed-polarization converter is proposed.Simulations and experiments show that the near-unity crossed polarization transmission can be obtained at the resonant frequency.