J. Obregon

High efficiency free running class F oscillator

A free running 1.6 GHz oscillator yielding 67% power efficiency with 24 dBm output power is proposed. It is based on the use of a transistor working in the an high efficiency class F associated to an appropriate feedback network. The transistor is a 2 mm gate periphery, 0.7 /spl mu/m gate length MESFET built by the Thomson foundry. The main impact of the characteristics of the constitutive components on the overall oscillator performance is also discussed.<<ETX>>

Optimum design of distributed power-FET amplifiers. Application to a 2-18 GHz MMIC module exhibiting improved power performances

A suitable and effective design method of distributed power amplifiers, based on the optimum FET load requirement for power operation, is proposed in this paper. An analytical determination of the gate and drain line characteristic admittances provides both the initial values and right directions for an optimum design. The best trade-offs between wide band and high power operation have been investigated. To validate the method, a FET amplifier demonstrator with a gate periphery of 1.2 mm has been manufactured at the Texas Instruments foundry. The MMIC amplifier demonstrated state of the art power density performance of 340 mW/mm over the 2-18 GHz band associated with 14.2% power added efficiency, 26.5% drain efficiency and 26.1 dBm output power at 1 dB compression in CW operation.<<ETX>>

Large signal design method of distributed power amplifiers applied to a 2–18-GHz GaAs chip exhibiting high power density performances

A suitable large signal design method of distributed power amplifiers, based on the optimum FET load requirement for high power operation, is proposed in this article. The gate and drain line characteristic admittances are determined, providing both the initial values and right directions for an optimum design. To validate the proposed design method, a FET amplifier demonstrator with a gate periphery of 1.2 mm has been manufactured at the Texas Instruments foundry. The MMIC distributed amplifier demonstrated an improved power density performance of 340 mW/mm over the 2-18-GHz frequency band associated with a minimum of 13% power-added efficiency and 24% drain efficiency at 1-dB compression in CW operation

A unified approach of PM noise calculation in large RF multitone autonomous circuits

This paper presents a simulation method to compute noise in autonomous and forced circuits using the harmonic balance (HB) formulation. Thanks to iterative linear solvers and multi-dimension conversion matrices, it can handle large multi-tone circuits to calculate phase noise spectra near and far from the carrier frequency. Its efficiency is illustrated with two real circuits.

First demonstration of a 0.5 W, 2 to 8 GHz MMIC HBT distributed power amplifier based on a large signal design approach

In this paper we report the results of the first demonstration of a 0.5 Watt, 2 to 8 GHz MMIC HBT distributed power amplifier optimised with a new design methodology. Initially developed for MESFET transistors, this new design methodology has been applied to HBT devices to obtain simultaneously both high power and high efficiency operation. Thus, a power density performance greater than 1 W/mm has been demonstrated compared to the MESFET where a typical value of 0.35 W/mm can be observed. Moreover, an average value of 20% power added efficiency between 2 and 8 GHZ has been measured with a peak efficiency of 30% at 3 GHz.

Efficient algorithm for steady-state stability analysis of large analog/RF circuits

This paper presents a method for the investigation of AC and large signal steady-state stability of electrical (analog/RF) circuits. In both cases stability/instability are detected through fast calculation and analysis of circuit poles. Thanks to iterative algorithms (Krylov-subspace methods) applied to modified nodal formulation of conversion matrices, a selection of poles is computed, allowing the method to be applied to large size circuits of any type of topology.

Impact of self-heating in LF noise measurements with voltage amplifiers

Voltage Amplifiers have been used to characterize the low-frequency noise of Heterojunction Bipolar Transistors (HBTs). They generally feature not only a lower noise floor, but also have less impact on simultaneous (two-port) measurements than Transimpedance Amplifiers, when moderate to high DC current regimes are considered. However, when the Device Under Test (DUT) is characterized under these regimes, common concepts such as unilateralism and frequency-independent small-signal parameters are no longer valid due to the frequency-dependent thermal response of the DUT (self-heating). It will be shown that depending on the conditions under which the measurements are carried out, the experimental data may vary for some orders of magnitude, leading to an incorrect characterization if the effect is disregarded.

New system-level simulation of noise spectra distortion in FM-CW autonomous cruise control radar

The design of complex MMICs such as ACC car radar involves the development of efficient and fast simulation techniques to predict the characteristics of the circuits. Their noise behavior simulation is one of the main drawback due to its complexity and large computation time. We propose in this paper, a new method based on a circuit envelope to simulate the noise spectra conversion of a signal passing through a MMIC. The efficiency of the proposed method is shown with the comparison between simulation and measures of the AM/PM conversion of a millimeter wave transmitter.

Experimental characterization of the cyclostationary low-frequency noise of microwave semiconductor devices under large signal operation

his paper presents a detailed experimental analysis of the cyclostationary properties of low-frequency (LF) noise sources of microwave bipolar devices, in order to improve the LF noise description in compact models. Such models are used to help designers on predicting circuit performances such as phase and amplitude noise in oscillators. We start by reviewing the most relevant experimental and simulation results on the subject, and then investigate the model of conductance fluctuations proposed to explain the 1/f noise of carbon resistors. This simple linear case serves as a basis for understanding the complex case of a non-linear device under large-signal periodic operation. We then present the large-signal small-signal analysis of a pumped junction, focusing on the process of converting the fundamental LF noise process, a current fluctuation, into voltage fluctuations. We show why a stationary noise model would lead to an increase of the voltage noise observed around DC when the device is pumped, while the voltage noise would decrease if a cyclostationary model was used. A great amount of experimental data is presented not only to support our analysis, but also as a mean to distinguish between the two noise processes under consideration: stationary or cyclostationary. The goal of our noise measurement technique was to maximize the difference between those two concepts. Throughout the paper, we revisit some known concepts and show how some experimental results may lead to misinterpretations.

A new experimental method to characterize cyclostationary noise models of bipolar devices

This paper presents an experimental method that can be used to determine the cyclostationary properties of the low-frequency noise of bipolar transistors and diodes. The noise is measured while the device works in nonlinear regime, pumped by a low-noise signal source. To measure the noise around carrier (as close as 1 Hz offset from the carrier), bridge circuits are used to balance the pump out. By applying the proposed method to evaluate the low-frequency noise of a SiGe transistor in open collector configuration, it is shown that the 1/f like noise of the device is entirely attributed to fluctuations of its conductance.