D波段双球镜准光系统测量低耗介质

采用双球镜准光腔、频谱仪和锁相返波管组建了D波段低损耗介质测试系统，该系统通过频谱仪和外置谐波混频器得到腔体谐振测试数据，并用拟合或积分方法从谐振曲线中求解出准光腔的品质因数。测得双球镜开腔的固有品质因数大于8105，使该系统在工作波段可测量损耗角正切为10-5量级的低损耗介质。用该系统测出的石英、人造金刚石和蓝宝石的介电常数和损耗，与报道的结果一致，并测得4H-SiC在132.07 GHz的介电常数实部为9.598，损耗角正切为6.110-5。

Biconcave quasi-optical resonator system for low loss dielectric measurements at millimeter wave D band

For the determination of dielectric properties of low-loss materials in millimeter wave band, this paper describes a biconcave quasi-optical resonator with the Q factor over 0.8 million, which enables the determination of loss tangents down to the 10-5 range. The biconcave resonator system utilizes a phase-locked loop with harmonic mixer to synchronize a backward wave oscillator source and a microwave spectrum analyzer. The spectrum analyzer acquires high-resolution scan of the resonance curve. The Q factor of the cavity is calculated by performing a non-linear least squares fit to a Lorentzian line shape or by the resonance curve area method. The test results of quartz, CVD diamond and sapphire at ambient temperature are close to the data in the literatures, and the permittivity of 4H-SiC at 132.07 GHzare measuredto be 9.598 and the loss tangent to be 6.110-5。