New insight into subharmonic oscillation mode of GaAs power amplifiers under severe output mismatch condition

Imbornone, J.; Murphy, Michael T.; Donahue, R.S.; Heaney, E.

doi:10.1109/gaas.1996.567896

Cited by 7 publications

(7 citation statements)

References 7 publications

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“…Driving the transistor in the nonlinear region can cause parametric sub‐harmonic oscillations due to the nonlinear characteristic of the transistor capacitors . This instability issue strongly depends on the input power level, bias condition, operating frequency and load termination .…”

Section: Simulation and Measurement Resultsmentioning

confidence: 99%

Efficiency enhancement by employing the transistor nonlinear capacitors effects in a 6W hybrid X-band Class-J power amplifier

Forouzanfar

Joodaki

2017

Int J RF Microw Comput Aided Eng

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This article presents the design and fabrication of a 6 W X‐band hybrid Class‐J power amplifier (PA) based on a bare die GaN on SiC HEMT by accurate implementing the transistor nonlinear capacitor effects. The transistor input capacitor is precisely modelled and its nonlinearity effects on Class‐J performance is studied for the first time. It is shown that the harmonic generation property of the nonlinear input capacitor, especially at the second harmonic, can be of benefit to shape the transistor gate voltage as a quasi‐half wave sinusoidal waveform and consequently, it can improve the power added efficiency (PAE). A complete 3D thermal model of the power transistor is developed using ANSYS software and it is calibrated based on the thermal measured data. The PA achieves 13 dB average power gain over the frequency range of 8.8‐9.6 GHz. The drain efficiency and PAE are about 67% and 58% at 9.2 GHz, respectively.

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Section: Simulation and Measurement Resultsmentioning

confidence: 99%

Efficiency enhancement by employing the transistor nonlinear capacitors effects in a 6W hybrid X-band Class-J power amplifier

Forouzanfar

Joodaki

2017

Int J RF Microw Comput Aided Eng

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“…Thus, the thorough evaluation of  LS will be done through a sequence of two-stage analyses: a HB analysis and a perturbation analysis based on the conversionmatrix approach. A double sweep is carried out in the magnitude and phase of  o , (0 to 1 in magnitude and 0 to 360º in phase), performing a HB analysis for each  o , followed by a circuit linearization with the conversion-matrix approach to calculate (1) and (2). In this conversion-matrix analysis, the perturbation frequency f is swept from 0 to f in , which provides the double-dependence factor  LS (f,  o ).…”

Section: Termination Impedance At Fundamental Frequencymentioning

confidence: 99%

“…Power amplifiers (PAs) that are stable under ideal 50  terminations may become unstable under antenna mismatch conditions in realistic wireless environments where the antenna input impedance is affected by objects in its vicinity [1]. In many cases, the application imposes circuit stability for any possible load condition, including highly reflective loads [2]. These widely reported problems constitute a serious concern for PA manufacturers and several simulation procedures have been proposed for their prediction at the design stage.…”

Section: Introductionmentioning

confidence: 99%

Stability criteria for power amplifiers under mismatch effects

Suárez

Ramírez

Sancho

2015

2015 IEEE MTT-S International Microwave Symposium

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Potential instability of power amplifiers (PAs) under mismatch effects is analyzed, with emphasis on the impact of the PA termination at the fundamental frequency. A largesignal version of the µ factor is derived, considering the lower and upper sideband of the fundamental frequency as virtual observation ports. This requires the application of the conversion matrix approach to each steady-state solution obtained with harmonic balance when varying the fundamental termination. To evaluate the impact of the fundamental output load, a contour technique is used to assemble loads giving the same µ value. A stabilization procedure is provided, based on the mapping of the mismatched load onto the stable region of the fundamental termination Smith chart. The analysis is extended to consider the baseband frequency, using three virtual observation ports.

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“…The instability of power amplifiers (PAs) under termination conditions other than 50 Ω, usually due to antenna mismatch [1, 2], can lead to serious malfunctioning, involving the observation of incommensurable oscillations and frequency divisions by two [2]. To guarantee a reliable operation in a variety of conditions, some applications impose stable operation even under highly reflective loads [3].…”

Section: Introductionmentioning

confidence: 99%

Prediction of odd-mode instabilities under output mismatch effects

Rodríguez

Terán

Lucio

2017

Int. J. Microw. Wireless Technol.

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Prediction of odd-mode instabilities under output mismatch effects almudena sua ' rez, franco rami 'rez and sergio sancho A methodology is presented to predict odd-mode instability in power amplifiers under output mismatch effects, as in the case of amplifiers connected to an antenna. This kind of instability is often observed in multi-device configurations, due to their symmetry properties. Unlike the single-ended situation, there is a cancellation of odd multiples of the oscillation frequency at the circuit output, so there is no impact of the load-impedance values at the sideband frequencies. The odd-mode instability only depends on the impedance terminations at the fundamental frequency and its harmonic terms, and can only be detected within the circuit unstable loop, instead of the antenna-connection terminals. The possible unstable modes are related with the eigenvectors of an outer tier conversion matrix accounting for the symmetry properties of the circuit topology. Under sufficient low-pass filtering of the amplifier output network, the analysis parameters can be limited to the magnitude and phase of the reflection coefficient at the fundamental frequency. This analysis involves a computationally efficient graphical technique to detect potential instabilities and a bifurcation-detection method to determine the instability boundaries in the Smith chart. The two main types of instability from periodic regime are considered, respectively associated with incommensurable and subharmonic oscillations. Results have been validated through pole-zero identification and experimental measurements.

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New insight into subharmonic oscillation mode of GaAs power amplifiers under severe output mismatch condition

Cited by 7 publications

References 7 publications

Efficiency enhancement by employing the transistor nonlinear capacitors effects in a 6W hybrid X-band Class-J power amplifier

Efficiency enhancement by employing the transistor nonlinear capacitors effects in a 6W hybrid X-band Class-J power amplifier

Stability criteria for power amplifiers under mismatch effects

Prediction of odd-mode instabilities under output mismatch effects

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