LiZn Ferrite And The Application For Ka-band Phase Shifter

Phase shifter is a microwave device which can adjust the phase of the electromagnetic wave. It is widely applied in radar system, microwave communication system, measurement system and other military and civil engineering systems. Ferrite phase shifter is very advantageous in many ways such as low insertion loss, high power capacity, mature process technology and low cost, which make ferrite phase shifter extensive use. In this paper, the LiZn ferrite applied in Ka-band ferrite phase shifter and nonreciprocal latching phase shifter with LiZn magnetic core and back-ridged waveguide structure were investigated.Firstly, LiZn ferrite with high Br, high Bs, high Br/Bs and low Hc was prepared. The influence of Bi2O3 and sintering temperature on properties of LiZn ferrite were mainly investigated. The results manifest that, the requirement for Bs, Br and Hc can be accomplished when dopped 1wt% Bi2O3 and sintered at 980℃. The properties of LiZn ferrite are given below, Bs>420mT, Br>370mT and Hc<120A·m-1.Secondly, stimulation design of phase shifter was carried out by electromagnetic stimulation software Ansoft HFSS 12.0 in the band of 33.5~34.5GHz. The influence of phase shifter structure on the performance of phase shifter was investigated. The results show that the phase shift increases with increasing the thickness of ferrite wall, the dielectric constant of filling medium and decreasing the width of toroid hole. Besides, the phase shift increases with increasing the back ridge height of back-ridged waveguide. But high back ridge result in poor frequency response of phase shift. The stimulation structure of phase shifter with the length of 20 mm magnetic core was optimized and the stimulation results manifest that phase shift is 276°at 34 GHz, the absolute value of insert loss is less than 0.91 dB and VSWR is less than 1.08 in the band of 33.5~34.5GHz.Finally, the assembling technology and the driver of the ferrite phase shifter were studied. At room temperature, the phase shifter was measured by vector network analyzer in the band of 33.5~34.5GHz and the results are as follows. Phase shift of No.1 phase shifter with length of 20 mm is 149°at 34 GHz, the absolute value of insert loss is less than 1.05 dB and VSWR is less than 1.4. Phase shift of No.2 phase shifter with length of 20 mm is 146°at 34 GHz, the absolute value of insert loss is less than 1.6dB and VSWR is less than 1.4. No.3 phase shifter combined by No.1 and No.2 phase shifter possesses the phase shift about 293°at 34 GHz, the absolute value of insert loss is less than 2.3dB and VSWR is less than 1.5. Then the reasons for differences between stimulation and measurement results were discussed.