ARFTG - RF & Microwave Measurements

Presented by

Abstract: In this contribution, we present the performances of an IQ mixer-based RF-interferometer module, called the HΓ- VNA , designed to be used as an add-on to VNAs to improve the measurement sensitivity and accuracy of DUTs presenting extreme impedances (|Γ| greater than 0.8). The calibration procedure used to obtain accuracy improvement is presented, and allows to set both reference and system impedance to any selected one. The procedure is benchmarked by comparing it to a conventional 50 Ω short-open-load calibration performed on a 50-Ohm VNA. For this purpose, a custom on-wafer calibration kit has been realized, using a fused silica substrate, featuring calibration loads with very high impedances (between 3.5 kΩ and 7 kΩ). Experimental results show accuracy improvements when applying the proposed calibration technique to the measurement of high impedance resistors, for frequencies below 4 GHz.

Presented by Jon Martens

Full Paper Title: Differential noise measurements: sensitivities and uncertainties with direct correlation- and balun-based methods

Abstract: Differential amplifiers and converters are ubiquitous and explicit differential noise measurements of these are of increasing importance. Among the possible techniques are those performing direct correlation of the DUT noise waveforms and those using a characterized balun to make it into one or more single-ended measurements. Both measurement classes have variations that can lead to differences in uncertainties and sensitivities. Several versions will be examined, through measurement and simulation, as a function of DUT configuration (different phasing and levels of correlation) and receiver/balun characteristics (mismatch, imbalance) versus perturbations including calibration errors and external noise ingress. In these experiments, a directly-measured calibration approach and a comprehensive balun model can have similar sensitivities (but with different levels of effort) which can be up to an order of magnitude lower than those for a partially implemented balun model.

presented by: Linli Xie, University of Virginia

Full paper title: Electronic Calibration of One-Port Networks at Submillimeter Wavelengths using Schottky Diodes as On-Wafer Standards

Abstract: An approach for one port on-wafer electronic calibration at submillimeter wavelengths is described. Quasi-vertical GaAs Shottky diodes integrated onto silicon serve as the electronic calibration standard. The S-parameters of the diode standards are characterized of the WM-570 (325-500 GHz) band as a function of bias and subsequently used as the coefficients derived using the diode standard are shown to be in good agreement with those obtained from a conventional set of standards consisting of coplanar short circuits.

presented by Carmine De Martino, TU Delft

Abstract: In this paper we present a method to alleviate the errors introduced by the bias dependency of the electrostatic discharge or antenna-effect protection diodes when a direct metal-one TRL calibration is employed. The proposed method shows that the two error-boxes produced by the TRL algorithm can be split and combined without introducing mathematical errors as long as the perturbation can be assumed to be a reciprocal network. A mathematical analysis is provided and initially bench marked against a circuit level simulation employing only s-parameter defined error boxes and ideal lumped components and after verified using 3D EM simulations of the test fixtures. The circuit level simulator confirms the mathematical analysis while the 3D EM simulator validates the applicability in a more realistic setting. Finally, the proposed method is used in a real measurement where the test fixture are implemented in a 28nm CMOS technology and characterized at frequencies between 140 GHz to 200 GHz. The measurement using the proposed method clearly shows reduced deviation from known reference when compared to the non-split approach.

presented by Tibault Reveyrand, XLIM

Abstract: The increasing need for measurement setups includ- ing several vector signal generators is associated with the creation of multiple input amplifiers such as digital Doherty, outphasing techniques or amplifier with a RF load matching control such as Load Modulated Balanced Amplifiers (LMBA). Therefore, an absolute calibration, in amplitude and phase of the sources has to be performed. A complete and automated calibration method for multiport generation is presented here. It introduces, as a new standard, a multiport passive device previously characterized in S-parameters. This method is detailed analytically and validated experimentally. Calibrated measurements of dual input power amplifiers are also presented.

presented by Sattam F. Alshali, Cardiff University

Abstract: This paper investigates the concurrent operation of a commercially available, modulated impedance synthesis and measurement system with digital pre-distortion (DPD) for industry standard modulated signals. The system was used to characterize a 10W GaN HEMT device, and provide impedance control over signal and distortion bandwidths, in response to a 10 MHz LTE signal centred at 2 GHz, and was able to rapidly achieve target reflection coefficients with an error less than -40dB (1%). A National Instruments (NI) PXi based characterisation system was used to apply a commercially available memory-based DPD algorithm. The transistor was biased in class-AB and was successfully linearised to better than -47.95 dBc ACPR when delivering at 2.5W average output power into an optimum load. Interestingly, the analysis showed that the DPD corrected ACPR contours aligned closely with the P1dB contours, confirming the relevance of targeting peak-power for DPD, rather than raw ACPR. Also, and importantly, a level of linearity performance was achieved that meets for example, the 3GPP linearity specifications (45dBc) for commercial deployment, and demonstrates how this modulated load-pull system and DPD can be combined to de-risk an amplifier design at a very early stage in the design process.

Presented by Chihyun Cho, from KRISS

This paper describes in detail how to characterize the response of a commercial real-time digital oscilloscope (RTDO) with traceability. The commercial RTDO usually employs a time interleaving ADC (TIADC) structure. Thus, aliasing is produced when the measurement is separated according to each ADC. As a result, it is difficult to obtain an accurate frequency response for each ADC. In this paper, we propose a method to avoid under- sampling issue, and it can achieve high sampling rate because it is similar to the equivalent sampling method.

Presented by Haris Votsi

This paper presents the experimental verification, imaging and animation of the radiation and coupling generated due to a coaxial-to-microstrip transition using electro-optic based measurements. The measured and simulated scattering parameters of a 50-⌦ microstrip transmission line accessed with two SMA microwave end launch connectors are presented. An electro-optic based system and a vector

network analyzer are integrated to measure the normal electric field component of the device at multiple frequencies up to 10 GHz. The measurements capture the radiation due to the coaxial-to-microstrip transition. Finite-element-method (FEM) based electric field simulations show a very good agreement with the measured results.

Keynote talk to open the 93rd ARFTG Conference

Presented by: Dylan Williams, NIST