Giorgio Leuzzi

Physical/electromagnetic pHEMT modeling

An effective technique, which is based only on geometrical and physical data, is presented for the analysis of high-frequency FETs. The intrinsic part of this electron device is described by a quasi-two-dimensional hydrodynamic transport model, coupled to a numerical electromagnetic field time domain solver in three dimensions that analyzes the passive part of the FET. Such an analysis is entirely performed in the time domain, thus allowing linear and nonlinear operations. The obtained data give insights to some parameters affecting the signal distribution through the entire device structure; a comprehensive discussion of these is given for a test device. In order to prove the validity of the approach, the bias-dependent small-signal analysis is compared with the corresponding measurements up to 50 GHz for two 0.3-/spl mu/m gate-length AlGaAs-InGaAs-GaAs pseudomorphic high electron-mobility transistors, each having two gate fingers of 25-/spl mu/m and 100-/spl mu/m width, at bias points ranging from Idss to the pinchoff regime. The accuracy and the efficiency of the approach make it suitable for device optimization.

A Tuneable Active Inductor With High Dynamic Range for Band-Pass Filter Applications

An approach for the design of high-Q active inductor (AI) with high dynamic range is presented. The proposed AI includes a passive variable phase- and amplitude-compensating network and a highly linear inverting amplifier, forming a gyrator-C architecture. The equivalent inductance and resistance values are tunable in a wide frequency range; outside the operating frequency band, the inductor equivalent resistance increases, improving signal rejection for band-pass filter applications. As a feasibility demonstration, a first-order active band-pass filter using the high-Q active inductance has been fabricated and tested. The filter has a center frequency of 600 MHz and a measured noise figure of 11 dB with a 5-dBm 1-dB compression point and an 82-dB dynamic range.

RF and microwave high‐Q floating active inductor design and implementation

Summary In this paper, a high-Q floating active inductor (FAI), suitable for RF and microwave applications, is presented. The proposed FAI is based on two cascaded pairs of highly linear capacitance gyrators, which provide a symmetric and reciprocal structure. The proposed FAI shows fully symmetrical two-port characteristics, high quality factor and high linearity. As a feasibility demonstration, a prototype of the designed FAI has been fabricated, together with an LC series band-pass filter. At the operating frequency, the real part of the impedance of the equivalent FAI is very low (Req = 0.0039 Ω), providing a very high quality factor. The filter has a central frequency of 430 MHz and a −3 dB bandwidth of about 9 MHz. Copyright

Single transistor high linearity and wide dynamic range active inductor

In this paper, an active inductor AI with high linearity and high dynamic range, including a minimum number of components, is presented. The AI is composed by a single transistor, and by a passive compensation network; the latter allows the control of the values of both the inductance and the series resistance.

Complete and Systematic Simulation Tools for Frequency Divider Design

In this study, a two-stage simulation method is presented for the efficient design of frequency dividers using harmonic balance. The first stage uses a modified conversion matrix approach to select the subharmonic loads of the active element enabling the frequency division by a given order N. The second stage makes use of an auxiliary generator to obtain and modify the sub-harmonic-power curve versus the input power or input frequency. Systematic simulation tools are used to eliminate common hysteresis phenomena, which require additional constraints to minimize the disturbance of the original frequency-division bands and output power. A harmonic-balance technique to distinguish between subcritical flip bifurcations, associated with hystereses, and supercritical ones is presented, to our knowledge, for the first time. A technique is also derived to transform subcritical bifurcations into supercritical ones. The techniques have been successfully applied to a frequency divider by 2 at 630 MHz.

TUNABLE ACTIVE FILTERS FOR RF AND MICROWAVE APPLICATIONS

In this paper, we present a low-voltage tunable active filter for microwave applications. The proposed filter is based on a single-transistor active inductor (AI), that allows the reduction of circuit area and power consumption. The three active-cell bandpass filter has a 1950 MHz center frequency with a -1 dB flat bandwidth of 10 MHz (Q ≈ 200), a shape factor (30–3 dB) of 2.5, and can be tuned in the range 1800–2050 MHz, with constant insertion loss. A dynamic range of about 75 dB is obtained, with a P1dB compression point of -5 dBm. The prototype board, fabricated on a TLX-8 substrate, has a 4 mW power consumption with a 1.2 V power supply voltage.

Variable-load constant efficiency power amplifier for mobile communications applications

A SiGe HBT Class-B power amplifier has been developed with a voltage-controlled variable load, for constant efficiency also at low power levels. The output matching network includes varactor diodes that can change the load impedance at the collector of the transistor. The load line can therefore be adjusted to provide a variable output power saturation level, shifting the peak of the efficiency to the desired power level. Constant efficiency over a wide output power range is obtained. This amplifier minimises power consumption for variable output power applications, as required in mobile communications systems.

HIGH QUALITY FACTOR L-BAND ACTIVE INDUCTOR-BASED BAND-PASS FILTERS

In this letter, a tunable high-Q active inductor with high dynamic range is presented. The equivalent inductance and resistance values can be tunable in a wide frequency range by changing the compe...

A tunable 0.5-1.3 GHz CMOS 2nd order bandpass filter with 50/spl Omega/ input-output impedance matching

In this paper, a high Q tunable 2nd order band-pass filter, working in the RF frequency range and designed in a standard AMS 0.35mum CMOS technology, is proposed. The filter is based on three different stages that perform the input and output impedance matching, the bandpass function and prevent instabilities; therefore, it is suitable for integrated front-end RF applications. Simulation results have shown a tunable range between 500 MHz and 1.3 GHz with good input and output impedance matching and a low noise figure. Moreover, this circuit presents a compression-point level higher than -22dBm and a quality factor Q higher than 60

High-efficiency low-IM microwave PA design

Harmonic terminations effects in microwave power amplifiers on its power and linearity performances are discussed. By a simplified theoretical approach, useful guidelines are inferred to obtain both high efficiency and low intermodulation. The concepts discussed are experimentally validated showing the performances of four hybrid amplifiers, designed using different harmonic manipulation strategies. In particular, using a proper input second harmonic output termination, an improvement both in power added efficiency and intermodulation can be obtained.