Design of 40-W AlGaN/GaN MMIC High Power Amplifiers for C-Band SAR Applications

Two C-band monolithic high power amplifiers (HPAs) have been designed and implemented exploiting a 0.25-\u3bcm AlGaN/GaN HEMT process on an SiC substrate. The circuits have been designed for use in transmit/recevie modules of satellite synthetic aperture radar antennas for Earth observation. The design was accurately focused on the HEMTs' electrical and thermal working conditions in order to guarantee the reliable operation required by space applications. The HPAs operate in pulsed conditions with typical pulsewidth of 50 \u3bcs and 10% duty cycle: in that regime, the circuits deliver about 40 W with more than 21-dB associated gain and 40% to 45% power-added efficiency in the 5-5.8-GHz band. The achieved performance clearly demonstrates the very high potentiality of this technology for the replacement of GaAs-based HPAs in new generations of this type of systems

Low phase noise oscillator topologies: Theory and application to MMIC VCOs

In 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

Characterization of the Nonlinear Thermal Resistance and Pulsed Thermal Dynamic Behavior of AlGaN–GaN HEMTs on SiC

A laboratory setup, along with a set of measurement and identification procedures, have been developed expressly for the characterization of the thermal behavior of AlGaN/GaN HEMTs, suitable for microwave high power amplifier (HPA) design. The setup allows the measurement of the drain current time-domain dynamic response to positive drain bias pulses, performed at different temperatures and different dissipated power densities. The proposed measurement conditions discriminate thermal phenomena from electrical dispersive effects for this particular technology. Both the thermal resistance and the 'transient thermal resistance' are identified for a single-cell 1-mm device and for a 4-mm power-bar composed of four devices, designed to be used as the final stage of a monolithic $C$-band HPA for pulsed radar application. Transient data allow to compute the device operative channel temperature as a function of the pulsewidth and duty cycle, which is a crucial feature for pulsed HPA applications, typical for the GaN technology. The measured thermal data point out the nonlinearity of the thermal resistance versus dissipated power and base-plate temperature and the consequent critical thermal issue inherent in physically packing together such devices

Global modeling of GaN HEMT resistive current including charge trapping and self-heating for multi-bias multi-class PA performance prediction

An empirical Gallium Nitride (GaN) HEMT model, suitable for multi-bias and multi-class power amplifier (PA) performance prediction, is formulated. In addition to the fast dynamically-nonlinear capture mechanisms normally considered for local modeling, dynamically-linear charge trapping is taken into account here. A straightforward empirical identification procedure based on tailored double-pulsed IV measurements is described. Validation experiments carried out on a 8 7125 pm (gate length: 0.25 pm) GaN-on-SiC HEMT show good model prediction capabilities under different drain bias conditions and class AB, B, and C large-signal PA operation at both low-frequency (f = 4 MHz) and RF (f = 2.5 GHz)

A 40 watt C-band MMIC high power amplifier for space radar application exploiting a 0.25 um AlGaN/GaN on SiC process

This paper describes a C-band monolithic high power amplifier implemented with a 0.25 \u3bcm AlGaN/GaN HEMT process. The circuit has been designed for use in synthetic aperture radar antenna modules in space applications. The amplifier is made up of two stages: the final stage consists of eight devices for 9.6 mm of total periphery that are merged together to form a single power-bar. A quasi-inverse class-F regime for the HEMTs is implemented by harmonic tuning in order to achieve the best tradeoff between maximum output power and efficiency. When operating in pulsed mode with 50 \u3bcs pulse width and 10% duty cycle, the amplifier delivers about 40 watt with 21 dB of associated gain and 40% PAE over a 15% bandwidth centered at 5.4 GHz. The proposed MMIC HPA is a very valuable replacement for lower output power MMIC GaAs HPAs or hybrid HPAs, which are currently exploited at C-band for these applications. \ua9 2013 IEEE

A Q/Ku-K band MMIC double-balanced subharmonic diode ring mixer for satellite communications in GaAs pHEMT technology

A MMIC double-balanced subharmonic diode ring mixer was designed for broadband satellite communications exploiting a GaAs pHEMT process. The circuit implements the frequency conversion from Q (43.5-50 GHz) to Ku-K band (17-21.5 GHz). Besides the RF, LO, and IF baluns, the MMIC integrates a buffer amplifier for the local oscillator signal, which is designed between X and Ku bands (11-16.5 GHz), due to the subharmonic operation. The mixer measured conversion loss is between 8 and 12 dB along the bandwidth, with an LO power of 9 dBm. The input p1 dB and IP3 are 2 and 15 dBm, respectively. The balanced structure ensures an LO and 2 7 LO leakages at the IF port lower than -25 and -35 dBm, respectively. Other spurious remain below -67 dBc. The chip dimensions are 2.4 7 2.4 mm2

New pulsed measurement setup for GaN and GaAs FETs characterization

A new setup is proposed for the measurement of current-voltage pulsed characteristics of electron devices. The main advantages of the system consist in: shorter pulse widths through generation in a 50-\u3a9 environment, simple average current monitoring through separation of the direct and alternate current paths, setting of average voltage values independently of pulse amplitudes and duty cycle, and stability of the setup guaranteed by wide-band dissipative terminations. The system is used for the characterization of dispersive effects due to carrier energy traps and thermal phenomena in GaAs and GaN on SiC field effect transistors. The basic differences between the two technologies are highlighted in the paper. \ua9 2012 Cambridge University Press and the European Microwave Association

Iso-thermal and iso-dynamic direct charge function characterization of GaN FET with single large-signal measurement

A fast and simple method for the direct characterization of nonlinear charge functions of electron devices is presented. The input and output transistor ports are simultaneously excited through single-tone sources at different frequencies and calibrated large signal waveforms are measured by means of an advanced NVNA-based setup. Proper choice of the two frequencies guarantees an almost complete coverage of the voltages domain in a single and very fast measurement set and allows the extraction of the charge functions by direct integration of currents in the frequency domain, since, contrary to other methods, the measured waveforms are both iso-thermal and iso-dynamic (i.e. at fixed charge trapping status). The method is validated by characterizing the gate charge function of a 5W 8 7125\u3bcm GaN FET and implementing a simple table-based model of the transistor input port. Very good results are achieved by comparison with large-signal measurements under conditions different than the ones used for the characterization