Closed-form solutions are presented for calculating the reflection coefficient with corresponding uncertainty of metrology-grade 3.5 mm air-dielectric coaxial transmission lines for use as reference standards in S-parameter measurements up to 33 GHz. The closed-form solutions allow the calculation of the sensitivity coefficients required for calculating the propagation of uncertainties from the material and mechanical parameters of the transmission line toward its reflection coefficient uncertainties. The presented uncertainty framework evaluates every uncertainty source’s contribution, with uncertainties in reflection coefficient ranging from 1 · 10⁻³ up to 6 · 10⁻³. The approach is validated up to 33 GHz via a comprehensive measurement comparison of the reflection coefficient parameter for three 3.5 mm transmission lines with 16, 60, and 150 mm lengths. The values obtained by the proposed model agree well within the measurement uncertainties with known traceable calibration results of the transmission lines.

This paper analyzes and accurately models the complex noise behavior of vector network analyzers (VNAs) when measuring large-mismatch devices and subsequently shows how the VNA measurement noise performance is enhanced through implementation of a high-speed, broadband, active RF interferometer module. The presented VNA noise model provides a solid framework, benchmarked by measurement data, to analyze existing RF interferometer approaches. The performance improvement of the proposed interferometer implementation is then benchmarked in terms of magnitude and phase stability of the renormalized impedance level. A test bench employing the novel add-on RF interferometer module is presented and demonstrated to achieve high-speed cancellation of the scattered wave over a broad frequency band. The first experiment shows ultralow noise in a 1-18 GHz broadband measurement of co-planar waveguide 0.5-Ω and 5-k Ω impedance standards. Employing the proposed hardware setup improves the noise uncertainty for the 5-k Ω impedance standard by a factor of 8 and 20 at 1 and 18 GHz, respectively. In the second experiment, a factor of 2 height-resolution enhancement is achieved in a scanning microwave microscope when the RF interferometer module is added to the instrument.

In this paper, we present a technique to extract the complex permittivity of the different layers (i.e., pulp and skin) of a biological sample (i.e., mangoes) in broadband dielectric spectroscopy measurements. The proposed approach is based on a newly developed accurate and rapid electromagnetic lumped capacitance equivalent network model for the open-ended coaxial cable, capable of accounting for stratified layered media. Combining broadband dielectric measurement with the model predictions allows to derive the permittivity of the internal layers of the biological sample. The proposed approach is applied to evaluate fruit quality, i.e., staging of the effective fruit ripening and identification of internal fruit defects (not visible externally). Broadband permittivity measurements (0.5GHz to 5GHz) are presented and combined with the EM model to demonstrate the effectiveness of the technique for evaluation of the internal (i.e., pulp) staging and structure disorders in Mangoes.