48 research outputs found
A bias network for small duty-cycle fast-pulsed measurement of RF power transistors
No full textRadio-frequency power transistors affected by dispersive phenomena such as thermal and charge trapping effects can be effectively characterized and modeled by means of pulsed current-voltage measurements. This work presents the design of a passive bias network made out of off-the-shelf components and tailored for the application of fast pulses through its capacitive path, yet extending the bandwidth down to a few kHz. This custom component enables small duty-cycle (e.g., 0.1 %) fast-pulsed excitations of several tens of V of ac voltage in the presence of bias voltages up to 50 V and bias currents up to 2 A
Low phase noise oscillator topologies: Theory and application to MMIC VCOs
No full textIn the paper the advantages of the push-push oscillator topology in terms of phase noise performance are discussed and experimentally verified by means of measurements on X-band and C-band GaInP-GaAs MMIC VCOs. In particular an analytical approach, based on the frequency sensitivity pushing factor parameter, is used to demonstrate the phase noise improvement of at least 9 dB inherently offered by push-push topology, with respect to a fundamental frequency oscillator. This theoretical analysis is for the first time experimentally validated trough the design and characterization of three different MMIC VCOs, specifically developed for this purpose. © 2011 IEEE
VCO Behavioral Model Based on the Nonlinear-Discrete Convolution Approach
No full textA purely mathematical,behavioral model for Voltage Controlled Oscillators (VCO)is derived.It is based on a Non-Linear Discrete Convolution approach [1 ] whichllows a time-domain formulation compatible with commercial system-level simulators.The approach enables the VCO nonlinear dynamics to be described with great accuracy and computational efficiency,and its influence on the performance of an entire subsystem to be investigated. Model validation,implementation in commercial system- level simulation tools as well as application examples are provided in the paper
X-Band Power Amplifier for future generation SAR T/R Modules in HBT technology
No full textThis paper deals with the design of X-band T/R modules to be employed on a future generation Synthetic Aperture Radar (SAR) for space application. Since the final High Power Amplifier (HPA) stage of the transmitting chain directly affects the overall module performances (mainly efficiency and maximum output power), HPA topic has been deeply investigated. In particular, an HBT process has been extensively explored, because of its attractive features; however potential advantages can be really achieved only if thermal management is consistently addressed. In SAR applications the RF carrier phase control is of great concern and major causes of module output phase shifts have been identified: temperature variations of active devices, non-linear modulating phenomena (AM/PM conversion) and supply voltage dropping off. The designed HPA will successfully handle all of them without disregard efficiency. Expected improvements will be shown for the future generation T/R module employing the designed PA and future architecture solutions
Comparison between equivalent-circuit and black-box non-linear models for microwave electron devices
No full textBlack-box and Equivalent-circuit electron device models present different advantages. The first ones are independent from process and device technology (i.e, GaAs, InP, GaN). In the other side the black-box model extraction procedure could not be changed and modified, thus a “post-tune” procedure is not possible. On the contrary, equivalent circuits are strongly technology dependent, though they are more flexible in the identification procedure. In fact an “optimization” of the extracted model parameters is possible following a trade-off with measured data over a large set of bias conditions and frequencies. In this paper two device models, which represent the two categories, will be compared pointing out the differences in the extraction procedures and in the achievable accuracy under small-signal and large-signal operating conditions
A Ku band monolithic power amplifier for TT&C applications
No full textThe paper describes the design of a 38 dBm
monolithic power amplifier at Ku band. The amplifier has
to be used as the final stage of the downlink transmitter of a
TT&C system. A commercial power p-HEMT process
capable of handling a power density higher than 1 W/mm of
active area has been selected for the amplifier design. The
power capability of this process makes it possible to
integrate in a monolithic chip the functionality up today
supplied by hybrid modules. Since the circuit is a space
product, the attention is focused on reliability issues;
therefore performances have to be matched imposing the
devices to work at de-rated conditions respect to the process
maximum ratings. In this perspective, the device channel
temperature becomes a very tight design objective and has
to be carefully controlled by means of a thermal simulator.
The paper describes the three dimensional thermal model
built to predict the devices thermal behavior in the
environment of a finite difference thermal simulator. The
design of the circuit is also described from the specifications
to the final layout
Behavioral Model for Voltage Controlled Oscillators
No full textBehavioral Model for Voltage Controlled Oscillator
HB Analysis of Injection Locked Oscillators using commercial CAD tools
No full textIn this paper a new technique is proposed for the
analysis of Injection Locked Oscillators on the basis of
commercially available HB-based CAD tools for communication
circuits. The proposed methodology does not require either
direct access to the HB simulation engine or application of
auxiliary components to the circuit topology. The HB
convergence in the presence of a particular injected signal,
having assigned frequency and power characteristics, is simply
obtained by suitably providing the simulator with a proper initial
guess of the unknown circuit solution through the standard HB
user interface in the Agilent ADS software.
Accurate prediction of the output phase shift for each injected
frequency and estimation of the locking range are easily
achieved. The proposed technique is validated through accurate
comparisons with simulations carried out in the time domain
Implementation of non-conventional nonlinear models for electron devices in commercial CAD tools
No full textIn nowadays CAD environments for
integrated microwave circuit design, dedicated tools for the
implementation of user defined component models are
becoming more and more important. These tools are mainly
oriented to the definition of equivalent circuit models.
However, the need for more accurate prediction of nonlinear electron device performance pushes the modelling community towards the research of new, often nonconventional, modelling approaches (e.g., frequencydomain, behavioural, integral models, look-up-table based, state-space based, etc.). In such a context, the model implementation tools usually available may result not sufficiently flexible. The paper provides useful hints and points out the main limitations which can be encountered in the implementation of non-conventional electron device models. As an example, the implementation of a Nonlinear Discrete Convolution model will be considered by using three different advanced tools: the Model Wizard of AWR Microwave Office, the Model Development Kit and Verilog- A Language of Agilent ADS
