Research And Design Of Millimeter Wave Circularly Polarized Antenna Array Based On Sequential Rotating Feed Technology

With the continuous development of wireless communication technology,the performance requirements for new antennas in wireless systems continue to increase.Due to the characteristics of fast transmission speed,millimeter wave antennas can effectively improve the performance of the system,and have a broad application prospect in the 5G era.Thus,millimeter wave antennas are worth well studying due to its academic and application significance.In this paper,the sequential rotation technique is adopted,and the circularly polarized antenna array in millimeter wave band is designed based on the feed structure of the substrate integrated cavity.The paper work includes the following three parts:A circularly polarized antenna array based on a two-stage sequential rotation feed network is proposed.Based on the idea of substrate integrated cavity feeding with a quarter power divider,a cross cavity is designed to feed a radiation structure loaded with a circular/rectangular back cavity.The cross cavity is formed by sequential rotation,and the output phases of each port are sequentially 0°,90°,180°,and 270°.Circular polarization is formed through a 45 degree angle formed between the patch and the gap,forming 2 × And sequentially rotating the units,using the aforementioned substrate integrated sequential rotation feed network to form a 2 × 2.Sub array,rotating the above subarray sequentially,and forming a miniaturization with a two-layer sequential rotating feed network ×4 Lefthanded circularly polarized antenna array.The test results of the antenna indicate that its 4 × The-10-dB impedance matching bandwidth of the 4array is 22%and can cover 57-71 GHz.Its 3-dB axis specific bandwidth is 30.3%,covering 54.3-73.7 GHz.At 64.5 GHz,a maximum gain of 20.4 dBic can be obtained,with a gain bandwidth of 22.2%for 3-dB.A low-profile 2×2 double circularly polarized antenna array operating at 60 GHz has been designed based on two forms of sequential rotation.The first design is the unit,whose radiation structure is mainly a high-order cavity with air as the medium.Four sequentially rotating slots are etched on the metal plate above it.Through these four slots,radiation is introduced into the high-order cavity,introducing a dual-mode structure that can rotate sequentially.The operating modes are TE230/TE320 at low frequencies and TE410/TE140 at high frequencies,The self sequential rotation of mode 1 is formed by feeding two coaxial probes close to the center of the cavity.The feeding phases of the two coaxial probes are 0° and 90°,respectively.At this time,left-handed circular polarization(LHCP)is achieved.When the phase of the probe becomes 90° and 0°,the unit exhibits right-handed circular polarization(RHCP)performance.The feed structure of the unit is composed of a 3dB coupler composed of SIW and a transition structure from SIW to the coaxial line.The feed network of the antenna array is mainly composed of two layers of power splitters and a connection structure between the upper and lower layers.The power splitter feed network of the array also achieves a sequential rotation of the feed phase of 0°,90°,180°,and 270°.After simulation,the impedance bandwidth of the antenna with a coincidence of-1OdB is 24.08%,the axial specific bandwidth of the antenna with a coincidence of 3dB is 24.3%,and the maximum gains of left and right circular polarization are 12.7 and 12.67 dBic,respectively.The impedance bandwidth(|S11|)of-10dB for antenna testing is 27.2%,covering 54.6-71.8GHz;The tested impedance bandwidth of-10dB(|S22|)is 24.3%,covering 56.2-72GHz,and the isolation degree of 15dB can reach at least 40%,covering 50-75GHz.Based on the muti-high-order mode cavity feed network,a dual circularly polarized antenna array operating at 60GHz is designed.The sub array also adopts a dual circularly polarized structure.This array considers the use of a layer of sequential rotary feed network to realize the dual circularly polarized function.The sequential rotary feed network of the sub array is a substrate integrated cavity.The 90 degree phase shift between ports is achieved by the difference between the distance between the center of the cavity and the adjacent ports,By feeding unequal lengths of cavities in different directions through two intersecting gaps,the left/right circular polarization of the subarray cavity is achieved.The radiation unit is a linear polarization unit,and the array’s feed network utilizes a higher-order cavity with a working mode of TE6n0/TEn60(n=1,3).A double-layer dual circular polarization feed structure is adopted at the bottom of the cavity.The central operating frequency of the antenna is 60GHz,and the-10dB impedance matching bandwidth of the final antenna can cover 57-64GHz.The 3-dB axis overlap bandwidth of left-handed circular polarization and right-handed circular polarization is 56.55-65.8GHz,which is lower.The gain of left-handed circular polarization can reach up to 17.15dBic in the 5 7-71 GHz frequency band.The gain of right-handed circular polarization can reach up to 17dBic in the 57-71 GHz frequency band,and the antenna has achieved a radiation efficiency of over 90%throughout the entire operating frequency band,reaching the highest radiation efficiency of 94.3%at 62GHz.