| In recent years,millimeter-wave technology and terahertz technology have developed rapidly,and circularly polarized antennas have also been widely studied and applied,which are operating in the millimeter-wave band and terahertz band.When all kinds of circularly polarized antennas are designed and processed,the performance of the antennas needs to be tested.In the millimeter wave and terahertz bands,the traditional far-field measurement and near-field measurement have their own limitations,so the compact antenna test range has become the main method of antenna measurement in the millimeter wave and terahertz bands.So far,almost all of the compact antenna test ranges that have been developed are linearly polarized systems,while the circularly polarized compact antenna test ranges that can be used to direct measurement of the circularly polarized antennas are relatively rare.In this paper,through the design of the circularly polarized horn antennas,the linearly polarized three-mirror compact antenna test ranges are transformed into circularly polarized threemirror compact antenna test ranges,and it is verified that the compact antenna test ranges realizes the circularly polarized plane wave quiet zone,and it is can be used for the measurement of circularly polarized antennas in the millimeterwave band and terahertz band.The circularly polarized compact antenna test range will provide a simple and effective test method for circularly polarized antennas in the millimeter-wave band and terahertz band,and has great practical value for the development of high-frequency circularly polarized antennas.In this letter,two circularly polarized horn antennas are designed.The structure and principle of the antenna are introduced in detail,and the influence of various important parameters of the horn antennas is analyzed.The doublesegment rectangular-aperture circularly polarized horn antenna achieves an impedance bandwidth of 37.8%and an axial ratio bandwidth of 24.6%.At the same time,it achieves gain up to 20.5 dBi in the frequency band of 75 GHz-100 GHz;The variable angle multi-mode circularly polarized horn antenna achieves the impedance matching effect of S11 less than-21 dB and VSWR less than 1.2 in the frequency band of 85 GHz-98 GHz,and also can radiate circularly polarized wave in the frequency band of 88 GHz-100 GHz.Finally,the two circularly polarized horn antennas are used as feed for two three-mirror compact antenna test ranges with different apertures,the characteristics of the quiet zone within the aperture range are analyzed,and the axial ratio of all positions are calculated.When the double-segment rectangular aperture circularly polarized horn antenna is used as the feed in the frequency band of 75 GHz-95 GHz,the amplitude ripple is less than 1.5 dB and the phase ripple is close to 20° under 50%quiet zone usage efficiency;When the variable angle multi-mode circularly polarized horn antenna is used as the feed in the frequency band of 89 GHz-96 GHz,the amplitude ripple is less than 2 dB and the phase ripple is less than 15° under 50%quiet zone usage efficiency.The axial ratio is about 0.5 dB,which achieves a better effect of circularly polarized plane waves. |
