Abstract-A system has been developed for measuring the complex permittivity of low loss materials at frequencies from 500 MHz to 7 GHz and over a temperature range up to 1500 • C using stripline resonator cavity method. Details of the design and fabrication of the cavity were discussed. Particular features related to high-temperature operation were described. An improved resonance method at high temperature for determining complex dielectric properties of low-loss materials was developed. The calculation process was given by a physical model of the stripline resonator cavity at high temperature. The paper brought forward the method of segmentation calculation according to the temperature changes over the cavity, which matched the actual situation of high temperature measurements. We have verified the proposed method from measurements of some typical samples with the available reference data in the literature.

We describe here a system for accurate measurement of the dielectric properties of very low-loss materials in the 130 to 170 GHz frequency range. This system utilizes an open resonator with a quality factor ∼1×10 6 . Resonance curves for this resonator are acquired with a commercial spectrum analyzer equipped with an external millimeter-wave harmonic mixer. The excitation source is a backward-wave oscillator locked to the spectrum analyzer local oscillator via a digital phase-locked loop. This system permits rapid and accurate measurement of resonance curve line widths, permitting determination of loss tangents down to the 10 -6 range. Results are reported for silicon carbide (SiC), CVD diamond, sapphire, and quartz.

The combination of a D-Band phase-locked backward-wave oscillator (BWO) with a spectrum analyzer for measurement of permittivity and low loss-tangent is presented. For measuring low loss tangent material, such as CVD diamond and high purity semi-insulating ( ) 4SiC, at millimeter wave ranges, it is necessary to precisely measure an increase of a few kHz in a line-width of 200 kHz. We describe a phase-locked loop with frequency conversion that combines a BWO source and a microwave spectrum analyzer to obtain line-width measurements with less than 2 kHz (less than 1%) standard deviation in D-Band millimeter wave.Index Terms-Backward-wave oscillators (BWOs), frequency conversion, millimeter wave, phase-locked loop (PLL).

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A long loop phase locked backward-wave oscillator (BWO) for a high quality factor resonator system operating at D-band frequencies (130-170GHz) was described, the phase noise of the phased locked BWO was analyzed and measured at typical frequencies.When it used with a high quality factor open resonator for measuring the quality factor of simple harmonic resonators based on the magnitude transfer characteristic, this system has proven to be capable of accurate measuring the quality factor as high as 0.8 million with an uncertainty of less than 1.3% (Lorentzian fitting) at typical frequencies in the range of 130GHz-170GHz.

The processing of analysis, design and phase noise measurement of the Backward-wave oscillator(BWO) based on a 3rd order PLL is presented in this paper. The design utilizes a Charge-pump Phase-locked loop IC and a harmonic mixer in conjunction with a spectrum analyzer locking the BWO to a Tek2782 spectrum analyzer. We adopt a GPIB cable connecting the spectrum analyzer to a computer and created a virtual instrument by Labview program on the screen. The SSB phase-noise of this Phase locked BWO was measured and the typical value in the frequency range 135GHz to 160GHz is better than 63dBc/Hz at offset frequencie 1 kHz.

A Fabry-Perot open resonator excited through a coupling film and loaded with a plane-parallel dielectric plate is analyzed. The eigen equation of the field in the resonator is obtained. The quality factors of the resonator with and without a coupling film are compared. The quality factors of the resonator loaded with a plate that is in resonance and off resonance are also compared. It is shown that the difference in coupling losses between a loaded resonator and an unloaded resonator may strongly affect the accuracy in measuring ultra-low loss dielectric material. Some ways to reduce the influence of coupling loss are discussed. Our experiment results are consistent with the numerical analysis.