Gate Mixer Research Articles

Design procedure of a 30‐GHz HEMT hybrid gate mixer

AbstractThis article reports on a hybrid HEMT gate mixer exhibiting 4 dB of conversion gain and a 15‐dBm third‐order intermodulation intercept point at 28.5 GHz. These excellent performances have been made possible by a special design procedure that allows us overcome the problems inherent in the realization of hybrid circuits in millimeter‐wave ranges particularly the parasitic effects of bonding. © 1994 John Wiley & Sons, Inc.

Large signal model for analysis and design of HEMT gate mixer

This paper examines the problem of modeling HEMT's for calculations of conversion gain and intermodulation. An accurate and simple large signal model of discrete HEMT's has been developed. The nonlinear elements of the model are assumed to depend exclusively on the gate-source voltage. The interpolation of the measured data, using polynomial expressions, provides a description of the HEMT's nonlinearities in a CAD software. Based on the model, a hybrid HEMT gate mixer has been built. The accuracy of the model has been verified, and we obtained good agreement between the measured and simulated results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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

A new experimental technique using six-port reflectometers, operated in reverse configuration, suitable for source-pull 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 six-port 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 LF 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. >

Optimum design of mesfet mixers using a quasianalytical technique

A quasianalytical MESFET mixer design method based on a two-dimensional Fourier transform and appropriate simplifying assumptions concerning the MESFET model used is described. As an example the amplitude contents of mixing products together with optimum bias conditions and LO level for maximum conversion gain are derived for a gate mixer and compare well with the results given by a commercial harmonic balance simulator. © 1992 John Wiley & Sons, Inc.

Equal-gain loci and stability of a microwave GaAs MESFET gate mixer

The performance of a microwave GaAs MESFET gate mixer is theoretically investigated to clarify the existence of a conditionally stable RF frequency range as well as an unconditionally stable frequency range in which maximum available conversion gain (MACG) can be defined. For the unconditionally stable range, the MACG and load and source impedances are calculated as functions of RF frequency. For the conditionally stable range, the stability circle and equal gain loci are shown for source RF and load IF impedances. The conditionally stable region of the GaAs MESFET mixer appears around F/sub T/ of the MESFET. Higher conversion gain is easily obtained by choosing a MESFET for which the F/sub T/ is close to the RF frequency. >

Design technique for MESFET mixers for maximum conversion gain

A design technique for MESFET mixers is described. This technique is based on a mixer analysis program (MIXAN) designed to obtain the value of conversion gain and evaluate the influence of the embedding impedances for any local oscillator power and DC bias, in order to optimized the mixer performance. The MIXAN program, which uses SPICE as a subroutine to determine large-signal current and voltage waveforms, is able to obtain the operating conditions for maximum conversion gain. The good agreement between experimental and simulation results for X-band drain and gate mixers proves the validity of the design technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis and Design of MESFET Gate Mixers

A general and efficient nonlinear/linear analysis of MESFET gate mixers is presented. In the nonlinear analysis, the Newton-Raphson algorithm is used in conjunction with a novel approach for computing partial derivatives required by the Jacobian.The study of conversion gain and stability characteristics of the mixer is based on S-parameter matrix theory. As a result of the analysis, the possibility of improving the conversion gain of X-band MESFET gate mixers by an appropriate choice of the RF drain termination has been theoretically and experimentally demonstrated.

Volterra series analysis of MESFET mixers

Conversion gain in a MESFET gate mixer is analysed using a Volterra series representation. The transistor model includes the input gate capacitance non-linearity and the output, bi-dimensional non-linearity. Guidelines for optimum primary terminations on the RF and IF sides of the transistor are obtained, and analysis results are compared to an experimental mixer with 12 dB conversion gain.