Abstract：A novel miniaturized circularly polarized antenna used in Beidou navigation system is designed in this paper. The antenna adopts multi-layer laminated structure to design the radiation elements and feed network, and integrates B3 band, B1 band, L band and S band into one unit. Antenna placed on the top layer adopts the form of angle cutting to realize the right-handed circular polarization of the S band, the middle layer adopts 3 dB directional coupler to realize the right-handed and left-handed circular polarization of B1 band and L band respectively, and the bottom layer adopts Wilkinson power divider to realize the circular polarization of B3 band. The size of the antenna is only 60 mm×60 mm×21.6 mm. The indicators of the simulation and measured results are suitable for the requirements of Beidou system.

Abstract：A 6G millimeter wave ultra-wideband resonant metamaterial circular polarizer is presented in this paper. The polarizer is a single-layer structure with 10 μm ultra-thin polyimide film as the substrate, which effectively reduces the profile thickness of the polarizer and reduces the substrate loss to a certain extent. The circular polarization polarizer uses a low-Q design to mirror the symmetrical T-shaped metal surface, and the metal thickness is 0.6 μm, which is less than the skin depth of the metal in this frequency band. To some extent, the gold properties of the metal metasurface structure are reduced. The low-gold properties and low-Q metasurface design effectively improve the operating bandwidth of the metasurface. The resonator adopts a double resonant metamaterial design method to modulate the phase of orthogonal polarization wave with the same amplitude and phase, so as to achieve a 90° phase difference to form a circularly polarized wave. When the center frequency is 140 GHz, the 3 dB axial ratio can reach the bandwidth of 54 GHz, the center bandwidth can reach 39%, and the insertion loss is less than 5 dB.

Abstract：In this paper, according to the needs of L-band multi-function RF integration of CNI, the integrated design of the L-band receiver RF front-end circuit is carried out.By analyzing the performance requirements of L-band functions such as ATC,TACAN and DMEP on the receiver, combined with the main working principle and technical indicators of the receiver, the structure of the dual-conversion superheterodyne receiver is selected as the implementation scheme.The RF front-end down-conversion circuit and IF circuit of the receiver are designed, and the integrated design of the RF front-end is realized by multiplexing the down-conversion circuit and dividing the functions in the IF circuit.The gain, noise figure and other indicators of the devices at all levels under the two amplification modes are calculated. The conclusion shows that the indicators meet the design requirements of the functions,and the RF front-end integrated design scheme in this paper can meet the RF integration requirements of the CNI system L-band receiver.