Source-pull measurements using reverse six-port reflectometers with application to MESFET mixer design

Abstract

A new experimental technique using six-port reflectometers, operated in reverse configuration, suitable for sourcepull device characterization is reported. Analytical analysis and experimental verification show that using the six-port in reverse configuration allows the impedance of the test port of the sixport junction to be measured. This measurement technique is suitable for the design of low noise amplifiers and of active nonlinear circuits such as FET mixers and power amplifiers. This measurement technique has been used for the first time to study: 1) The effect of the LO and RF impedances of the input matching circuit of a MESFET gate mixer on the IF output power and conversion gain. 2) The effect of the phase of a LO offset short circuit presented to the MESFET output on the DC power efficiency and the conversion gain of the gate mixer.Experimental results of a NE-72084 GaAs MESFET gate mixer demonstrate that by presenting to the MESFET the optimum input RF and LO impedances and the right phase for the LO offset short-circuit at the output, 2.5 dB conversion gain can be achieved with a 2.5 times reduction of DC power consumption as compared to conventional design approaches.

Six-port-based active source-pull measurement technique

“…It has been shown that a six-port reflectometer (see the appendix) used in reverse configuration can measure its own test port impedance [10]. A mechanical stub tuner connected at the input of the reverse six-port junction allows variation of the source impedance seen by the device under excitation (see figure 1).…”

“…A similar approach, called source-pulling for the evaluation of linear/nonlinear device performance as a function of the source impedance, has also been proposed [8][9][10]. However, these source-pull measurement techniques suffer from several shortcomings such as the risk of oscillation of the active source-pull loop and the permanent need of a supplement vector network analyser (VNA) in the test set [8], or the need to calibrate the automated tuner [9].…”

“…However, these source-pull measurement techniques suffer from several shortcomings such as the risk of oscillation of the active source-pull loop and the permanent need of a supplement vector network analyser (VNA) in the test set [8], or the need to calibrate the automated tuner [9]. Moreover, it still is impossible to control the variation of the source impedance independently at each input frequency [9,10], since passive mechanical tuners are used. This paper proposes an active sourcepull measurement (ASPM) technique using a reverse sixport reflectometer.…”