Bernard Huyart

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.

Characterization of diode detectors used in six-port reflectometers

A method for characterizing in situ the diodes used as power detectors in six-port network analyzers is presented. The method requires only two unknown loads which are connected at the measurement ports. Measurement results obtained for one-port and two-port devices with a dual six-port realized in the 2-18-GHz frequency range are reported. In order to show the influence of frequency, these results are compared to those obtained using a midband characterization of the diode detectors. >

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.

Two new six-port reflectometers covering very large bandwidths

This paper presents two new structures for six-port reflectometers with very large operating bandwidths of more than three decades, using a combination of lumped reflectors and transmission lines. Circuits working over a range of 2 MHz to 1300 MHz and 2 MHz to 2200 MHz have been built using inexpensive passive surface mount elements and Schottky detector diodes. Comparing results obtained from the new proposed structures with those obtained from a commercial network analyzer showed a worst case absolute value of 0.020 for the complex difference between the measured reflection coefficients. A convenient calibration procedure, for the entire band, is proposed using three standards and four approximately known loads.

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.

A direction-finding antenna system using an integrated six-port circuit

A new method to measure the complex ratio of signals at adjacent elements of an array is presented. The circuit used for the measurement is an integrated six-port junction operated as an homodyne vectorial analyzer. A procedure that uses three known and many unknown incident or radiated fields conditions to calibrate the junction embedded in the antenna feed network is implemented. Experimental results are shown for a basic two-element array used as a receiving antenna. The direction of arrival of an incoming plane wave computed from the six-port measurements can be determined with a good accuracy. The monitoring system presented may find applications in direction-of arrival estimation.

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.

A six-port reflectometer calibration using Schottky diodes operating in AC detection mode

This works presents a six-port reflectometer in W frequency band (75-110 GHz) using Schottky diodes as power detectors. A linearization procedure and an AC detection technique are used to improve the measurement accuracy. In addition, a calibration procedure requiring two standards, a matched waveguide and a short circuit, is described. A comparison between experimental results obtained by the six-port reflectometer and other automatic network analyzers is presented. >

MMIC-calibrated probing by CW electrooptic modulation

This paper describes an electrooptic probing technique using a CW semiconductor-laser beam associated with a fast photodetector. Besides its simplicity, this technique presents some advantages over the sampling one thanks to the presence of a Fabry-Perot effect, namely an enhancement of the electrooptic interaction and a simple solution to the calibration problem. The good validity of the calibration method allows the application of this technique to S-parameter measurements. The S-parameter determination, in modulus and in phase, of an industrial MMIC by the electrooptic method is reported and compared with direct network analyzer measurements. >