Eric Bergeault

A new robust method for six-port reflectometer calibration

A new robust method for finding the parameters of Engens six-port-to-four-port reduction algorithm for six-port reflectometer calibration has been developed. Like other previously published methods, it uses a minimum of five loads with an unknown but constant absolute value of the reflection coefficient and unknown but well-distributed phases. However, the quality of the parameter estimates is improved, especially in noisy environments, by efficiently eliminating cases in which these earlier methods may become ill-conditioned. The new method has been used successfully to calibrate a newly developed six-port reflectometer in GaAs MMIC technology working between 1.3 GHz and 3.0 GHz.

Automated characterization of HF power transistors by source-pull and multiharmonic load-pull measurements based on six-port techniques

An original measurement system for nonlinear microwave power-transistor characterization using six-port reflectometers is presented. It allows independent active tuning of the output impedances at f/sub 0/ and 2f/sub 0/ (multiharmonic load-pull) and variation of the source impedance at the input port at f/sub 0/ (source-pull). An appropriate search algorithm enables automatic optimization of the output impedances and leads to fast user-friendly operation of the system. Experimental results are shown for a commercial GaAs MESFET power transistor at f/sub 0/=2 GHz.

New structure for a six-port reflectometer in monolithic microwave integrated-circuit technology

This paper presents a new structure for a six-port reflectometer which due to its simplicity can be implemented very easily in monolithic microwave integrated-circuit (MMIC) technology. It uses nonmatched diode detectors with a high input impedance which are placed around a phase shifter in conjunction with a power divider for the reference detector. The circuit has been fabricated using the F20 GaAs process of the GEC-Marconi foundry and operates between 1.3 GHz and 3.0 GHz.

RF power detector using a silicon MOSFET

This paper presents a novel approach for RF power measurements using a silicon MOSFET. It describes linear and nonlinear models of the RF MOSFET for results prediction. It shows a thorough comparison between predicted and measured results. The detector demonstrates a better sensitivity than biased Schottky diode detectors that we have measured.

Noise and power optimization of a MMIC quasi-circulator

This paper first sums up the power and noise limits of various types of active circulators and quasi-circulators. It then presents the design and measured performances of a narrow-band quasi-circulator module tailored for use in a transmit/receive (T/R) module. Its design implements an active power divider and a combiner, a method to calculate the minimum noise figure is presented for this circuit. At 4 GHz, the device demonstrates a noise figure of 5.5 dB and an output power of 18 dBm with associated gains of 4 and 7.6 dB for the receive and transmit path, respectively. The third-order intercept point (IP3) is equal to 25.6 dBm for the transmit path.

Accuracy analysis for six-port automated network analyzers

One of the assumptions made in six-port automated network analyzer (ANA) theory is that the reflection coefficient of the power detectors does not change with incident power level. This is not generally the case if diode detectors are used. Consequently, uncertainties in the measurement of the reflection coefficient of the unknown load appear because the calibration constants vary due to the variation of the detector reflection coefficients with power. Measurements of the variations of diode input impedance using commercial ANAs are used in a computer simulation to estimate their uncertainties. >

A new calculation approach of transistor noise parameters as a function of gatewidth and bias current

In this paper a new method to calculate the noise parameters of transistors T/sub i/ (MESFET or HEMT) as a function of gatewidth and drain-bias current is presented. This method needs the knowledge of the R, P, and C coefficients. It is based on the measurement of the noise parameters of a reference transistor T,/sub r/ at two bias points (I/sub ds1/ and I/sub ds2/), and the equivalent circuit elements values of all transistors T/sub i/. Using this method, the noise parameters (F/sub min/, /spl Gamma//sub opt/, R/sub n/) for two MESFETs T/sub i/ biased at another current I/sub ds3/ are obtained. Good agreement between the predicted and measured noise parameters values is obtained for a broad frequency range (4-20 GHz).

An active millimeter load-pull measurement system using two six-port reflectometers operating in the W-frequency band

An active load-pull measurement system using two six-port reflectometers operating in the W-frequency band is demonstrated. Ninety loads over the whole Smith chart have been synthesized and measured by both reflectometers. The maximum deviation between both measurement data is 0.02 for the magnitude and 3/spl deg/ for the phase of the reflection coefficient of the 90 loads. The constant power gain circles of a PHEMT operating at 89 GHz are shown and compared with those calculated from its S/sub ij/ scattering parameters. The deviation between the radii of circles is less than 0.03.

Nonlinear Modeling of RF Thermistor: Application to Bolometer Mount Calibration

The radio frequency (RF) bolometer thermistor has been studied over a wide frequency range. A novel equivalent electrical model is presented to show the nonlinear behavior of the bolometer thermistor for different polarization direct currents. This model has been used as the “detecting section” of a bolometer mount (thermistor RF sensor), and its “efficiency η” has been evaluated by the simple and quick “3-Γ, i.e., impedance method.” The experimental results show good agreement with the theoretical model. Using this model, together with the “impedance method,” can reduce the calibration time/cost of the bolometer mount for wide frequency ranges.

An Original Setup for Power Amplifier AM-AM and AM-PM Characterization

An original measurement system for nonlinear RF power amplifier characterization is presented. This new setup enables AM-AM and AM-PM measurements using one six-port reflectometer as a traveling wave ratio calculator. Experimental results of a commercial power amplifier at 2 GHz are presented and compared to those performed using a vector network analyzer.