| Nowadays, the integration of microwave load and devices used in the field of satellite, missile carrying system has been the main direction of development. Through photolithography process and the deposited film technology by the ferrite substrate to achieve the integration of microwave devices becomes a hot research topic in the application of traction. Based on this background, this paper studied the properties of tantalum nitride thin film and integrated devices prepared on the nickel-zinc ferrite substrate through the study of parameters, design theory and device production. To improve the power density of the film load, experiments designed Ca O-Al2O3-Si O2 glass glaze and then coated it on the surface of the Ni-Zn ferrite substrate. Finally, experiments designed and prepared microwave integrated isolator. Specific research process is as follows.Firstly, Ta N thin film was prepared on Ni-Zn ferrite substrate by DC reactive magnetron sputtering technique. By changing the conditions such as sputtering time and nitrogen partial pressure, experiments studied the phase structure, sheet resistance, temperature coefficient of resistance(TCR) and other parameters of Ta N thin film, and then determined the optimum parameters. The backing vacuum degree was 7.8×10-5-8.85×10-5 Pa, the sputtering pressure was 0.6-0.8 Pa, the sputtering argon flow was 50 sccm, the Nitrogen flow was 2 sccm, the sputtering power was 45-50 W, the sputtering time was 1000 s. The Ta N thin film prepared by this condition had the sheet resistance of 42-50 Ω/□, the temperature coefficient of resistance of 50-61 ppm/℃, and the thickness of about 350 nm.Secondly, the presence of many air holes on the surface of nickel-zinc ferrite substrate affects the thermal properties of the film load, which is not conducive to the improvement of the power density. The experiment designed the Ca O-Al2O3-Si O2(CAS) glass glaze and then coated it on the substrate by the way of screen printing to effectively improve the substrate surface flatness and thermal performance, which could usefully increase the power density of microwave load.Thirdly, the experiment designed the model of Ta N thin film microwave load with the size of 10 mm × 10 mm × 0.5 mm by HFSS software. The voltage standing wave ratio(VSWR) of the load was less than 1.2 in the frequency range from DC to 20 GHz, and that was in line with the project design requirements. Then the Ta N thin film load was prepared on the nickel-zinc ferrite substrate. After then, the thin film load was tested in the microwave frequency range from DC to 20 GHz. The results were showed as below: The VSWR was less than 1.5, the return loss S11 was less than –10 d B, the resistance changed from 42 Ω to 58 Ω, the power density was only about 1W/mm2. To improve the power density of microwave load, the Ta N thin film microwave load was made on the ferrite substrate which was coated with the CAS glass glaze. Tests showed that the power density was 2.5 W/mm2, and the load had realized the basic project research requirements.Finally, designing and simulating microwave integrated isolators on the basis of the Ta N thin film microwave load by HFSS software. The return loss and isolation of the isolators were less than-20 d B in the frequency of 8 GHz-12 GHz and the insertion loss was between-0.8 d B and 0 d B at the same time. The produced isolators were tested, tests showed that the return loss and isolation were less than –14 d B in the frequency of 8 GHz-12 GHz, and the insertion loss was between –4 d B and 0 d B. As a result, the isolators basically realized the goals of isolation performance and integration. |
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