Study On Garnet Ferrite's Preparation And Application In S/C Band Circulator

The microwave ferrite circulator is a non-reciprocal device,which works under the combined action of the external microwave electromagnetic field and DC stabilized magnetic field,basing on the gyromagnetic effect of microwave ferrite materials.The circulator plays a role of signal shunt isolation,matching and gain enhancement between microwave system receiver and transmitter as well as in the circuit,and is an indispensable key device in the electronic system.In the atmospheric transmission,compared with the X-band,the S and C band electromagnetic waves have the advantages of small propagation loss,long detection distance,etc.Radars work in the S/C band such as meteorological radar,military remote sensing,early-warning radar and so on,and their system components need tens of thousands of S/C-band circulators.With the development of communication technology and military technology,the low insertion loss and wide frequency band for S/C-band microwave circulators are highly valued,and the performance of the circulator depends on the garnet ferrite material.In this paper,based on the above,garnet ferrite materials applied in the S and C band circulators were prepared using a conventional oxidation ceramic process.The effects of ion substitution and key preparation processes on the performance of the garnet ferrite were investigated.Garnet ferrites for S-band circulator research results show that the suitable calcining temperature for Y_1.8Ca_1.2Zr_0.4V_0.4Mn_0.05Fe_4.1O₁₂2 ferrite is 1100?,and its sintering temperature is around 1300?.The substitution of Ti⁴⁺does not affect the crystalline phase of Y_1.8-xCa_1.2+xZr_0.4V_0.4Mn_0.05Fe_4.1-xTi_x O₁₂2 ferrite,and all the samples possess a single garnet ferrite phase.Ti⁴⁺ions is conducive to the grain growth.With the increase of Ti⁴⁺content,the lattice constant of the samples gradually increases,and the apparent density,saturation magnetization?4?M_s?,coercivity?H_c?and temperature coefficient(?_4?Ms)are gradually reduced.The ferromagnetic resonance linewidth??H?rises up slightly and then decreased with the increase in Ti⁴⁺content.The minimum value of?H is 22 Oe when x=0.4.The results also show that the porosity linewidth??H_p?is greater than the magnetocrystalline anisotropy linewidth??H_a?and?H_p is the main contribution of?H.The amount of Sn⁴⁺substitution has no effect on the garnet crystal phase,but Sn⁴⁺substitution restrains grain growth,and the average grain size is around 3?m.With the increase of Sn⁴⁺content,the lattice constant increases,and the apparent density,4?M_s,H_c and?_4?Ms?Ms decrease.?H and?H_p increase gradually,while?H_a decreases gradually.For garnet ferrites designed for the C-band circulator,theresultsshowthatthesuitablecalciningtemperatureof Y_2.3Ca_0.7Zr_0.3V_0.2Mn_0.05Fe_4.4O₁₂2 ferrite is 1100?,and its sintering temperature is near1340?.Al³⁺substitution causes the sample lattice constant to decrease gradually,the apparent density decreases gradually,and the average grain size remains about 7?m.In addition,Al³⁺substitution reduces 4?M_s effectively and also decreases K₁,but it has no effect on H_c which remains about 60 A/m.With increasing Al³⁺content,?H shows a decreasing trend.When the substitution amount x=0.6,?H is 34 Oe,and the relative dielectric constant is 13¹4,and dielectric loss tangent is less than 10^-3.Finally,based on the fabricated garnet ferrite materials,the simulation and design of the S/C-band ferrite microstrip circulator were carried out using HFSS software.According to the optimized structure parameters,the corresponding S/C band microstrip circulators were fabricated via polishing,photolithography and thin film deposition technology.The measurement results show that,for the S-band microstrip circulator,isolation is more than 18 dB,insertion loss is less than 0.9 dB,and voltage standing wave ratio is less than 1.4 at 2.4³.6 GHz.For the C-band microstrip circulator,return loss is more than 18dB,isolation is more than 20 dB,insertion loss is less than 0.8 dB,and voltage standing wave ratio is less than 1.4 at 2.4³.6 GHz.