Research And Design Of Broadband Circularly Polarized Microstrip And Liquid Antenna

For deploying a transmitter and a receiver without causing a polarization mismatch between them,circular polarization is becoming popular in wireless communications to improve system performance,providing better mobility and resistance to multipath fading.In order to adapt to the rapidly developing communication systems,there is no doubt the dual-frequency and broadband circularly polarized technique for antennas must be constantly developed.In addition.liquid antennas have become increasingly important in various communication systems due to their unique characteristics such as strong plasticity and reconfigurability.In this paper,combined with the requirements of various wireless communication systems,dual-frequency circularly polarized antennas,wideband circularly polarized antennas and liquid circularly polarized antennas have been studied intensively.1.A wideband micro strip open-slot antenna with dual-frequency dual-sense circular polarization(CP)is presented.A bent feeding structure and three radiating slots including a modified cross-shaped,an inverted F-shaped and an inverted L-shaped slots,are designed to excite two orthogonal electric fields with a quadrature phase difference for a radiating right-hand circularly polarized(RHCP)wave at 2.5 GHz and left-hand circularly polarized(LHCP)wave at 3.3 GHz.To improve the axial-ratio(AR),a bent parasitic element is introduced near the microstrip line.The experimental results show that the impedance bandwidth is 104.8%(2.2GHz to 4.79GHz),covering the WLAN,LTE and WiMAX frequency bands.The measured AR bandwidths are 460 MHz(18.4%)at the lower band(2.5 GHz)and 2150 MHz(65.1%)at the upper band(3.3 GHz).2.A novel CPW-Fed planar printed monopole antenna with broadband circular polarization(CP)characteristic is presented.Based on the improvement of the traditional monopole,the top of the rectangular patch is expanded into a circular patch,and an inverted L-shaped gap is etched in the middle of the circular patch,which forms a copper coin-shaped patch(CCSP),and multiple resonance modes can be excited to greatly increase the bandwidth of the antenna.By designing an asymmetric ground plane,the fundamental mode of the antenna can be degenerate into two equal-amplitude orthogonal modes with orthogonal phases,thereby achieving circular polarization at higher frequencies.To achieve a broadband CP wave,a vertical stub is added to the CCSP to produce orthogonal surface currents for right-hand circular polarization(RHCP).The design of the CCSP greatly increases the impedance bandwidth(IBW)of 89.2%which can cover the whole AR bandwidth of 71%completely.3.A novel wideband circularly polarized(CP)water dense dielectric patch antenna(DDPA)with EGaIn is introduced.By designing an asymmetric E-shaped slot with an off-centered microstrip,the single-fed circular polarization is realized,and an embedded structure of EGaIn is introduced to improve the circular polarization performance.Different liquids are injected into the outer layer of the embedded container,and simulations are conducted.The results show that the structure can meet the broadband needs when different liquids are injected.The embedded container structure is fabricated using 3D printing technology.By adjusting the length of the E-shaped groove and the width of the EGaIn channel,a relatively wide axial ratio bandwidth can be achieved.The measurement results show that the impedance bandwidth of this antenna is 20.2%(2.21-2.74 GHz),and the axial ratio bandwidth is 28.7%(2.19-2.85 GHz).