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:10.1109/4.628734

Cited by 20 publications

(11 citation statements)

References 8 publications

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“…The mismatched conditions may be due to an antenna circuit with input impedance different from 50 Ω or be the result of reflections in objects in the neighborhood [1]- [7]. In power amplifiers (PAs), the mismatch effects can give rise to significant degradation in output power, efficiency and linearity [1]- [3].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Output Loading Effects in Autonomous Circuits

Suárez

Pontón

Sancho

et al. 2017

IEEE Trans. Microwave Theory Techn.

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Abstract-A methodology is presented to analyze the impact of the termination load on the oscillation frequency and output power of autonomous circuits. Variations of this load can also lead to an extinction of the oscillation signal, due to their effect on the impedance seen by the active device(s). The new methodology enables an efficient analysis and mitigation of the pulling effects, in the case of undesired output mismatch, as well as an efficient oscillator synthesis in large-signal conditions, for specified values of oscillation frequency and output power. The method is based on the calculation of constant-amplitude and constant-frequency contours, traced in the Smith chart. Oscillation extinctions and some forms of hysteresis can be predicted through the inspection of these contours. However, the stability properties will generally depend on the frequency characteristic of the termination impedance. In an oscillator synthesis, the selected impedance, providing the specified values of oscillation frequency and output power, must be implemented in order to guarantee a stable solution. The dependence of the phase-noise spectral density on the particular implementation is predicted combining an analysis based on the variance of the phase deviation with the conversionmatrix approach.

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Section: Introductionmentioning

confidence: 99%

Analysis of Output Loading Effects in Autonomous Circuits

Suárez

Pontón

Sancho

et al. 2017

IEEE Trans. Microwave Theory Techn.

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“…Note that the negative real part and positive-slope resonance of Y T do not constitute a general instability condition. However, the limit steady-state oscillation condition in (2) and (3) is rigorous and should be fulfilled at any circuit node at the stability boundary.…”

Section: B) Frequency Division Bymentioning

confidence: 99%

“…The instability of power amplifiers (PAs) under termination conditions other than 50 V, 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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“…Characterization of antenna mismatch may provide a maximum VSWR, such that the antenna will never exceed certain  max under mismatch effects [1][2][3][4][5][6][7][8]. If this value can be estimated, the two factors  and µ' [39] (instead of k LS and  LS ) may be especially useful to predict the possible instability under a particular  max .…”

Section: Potential Instability Analysis Under Mismatch Effectsmentioning

confidence: 99%

“…Power amplifier (PA) designs, which are stable under ideal 50  terminations, may become unstable [1][2][3][4][5] under antenna mismatch conditions in realistic wireless environments, such as where the antenna input impedance is affected by objects in its vicinity [1][2][3][4][5][6][7][8]. Therefore, evaluation of the stability robustness against load mismatches is essential for reliable operation.…”

Section: Introductionmentioning

confidence: 99%

Stability Analysis of Power Amplifiers Under Output Mismatch Effects

Suárez

Ramírez

Sancho

2014

IEEE Trans. Microwave Theory Techn.

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1 Abstract -Novel criteria are presented for small-and large-signal stability analysis of microwave circuits under output mismatch effects. They are based on concepts from bifurcation theory, which enable the derivation of general equations for the stability boundaries that depend on the termination load. The boundary calculation does not require any optimization of the circuit parameters. Instead, it is based on the direct calculation of an admittance function obtained through circuit linearization about either the dc solution, in the small-signal stability analysis, or the periodic solution, in the large-signal one, with low computational cost. As will be demonstrated both with homotopy and bifurcation concepts, the Hopf locus obtained in this way delimits a stable region and a potentially unstable one. In a large-signal stability analysis, the sidebands that influence the stability properties are identified, which depend on the particular amplifier topology and its filtering effects. The stability boundaries are then calculated with the conversion matrix approach for all load impedance values at the relevant harmonic and sideband frequencies. For the derivation of absolute stability conditions, a new scattering type matrix is proposed describing the circuit response from the output reference plane with respect to the two sidebands about the input carrier. The new methodologies and formulations have been validated by independent simulations using pole-zero identification, and by measurements.

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

Cited by 20 publications

References 8 publications

Analysis of Output Loading Effects in Autonomous Circuits

Analysis of Output Loading Effects in Autonomous Circuits

Prediction of odd-mode instabilities under output mismatch effects

Stability Analysis of Power Amplifiers Under Output Mismatch Effects

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