P Longhi

An ultra-broadband robust LNA for defence applications in AlGaN/GaN technology

The design, fabrication and test of a 2–18 GHz monolithic Low Noise Amplifier utilizing 0.25 µm AlGaN/GaN HEMT technology is reported. The measured noise figure of the amplifier is less than 4.7dB over the 2 – 18 GHz frequency range, exhibiting a minimum of 3.3 dB at 3 GHz. The LNA gain is 23dB. Even being a low-noise amplifier, the MMIC can withstand 10W input CW RF power, demonstrating no apparent degradation: to the authors knowledge this is the best RF LNA survivability reported to date in this frequency range using GaN technology.

Full W-Band High-Gain LNA in mHEMT MMIC Technology

In this contribution the possible applications, technology, design and measurements of a W-Band high gain LNA are given. The main features of the four stage LNA can be summarised as following: a 25 dB average gain with plusmn2 dB ripple from 70 to 105 GHz, where gain is higher than 21 dB on the entire 70-110 GHz range. LNA predicted noise figure is 2.7 dB between 80 and 95GHz and less than 3.2 dB up to 108 GHz while the chips power consumption is 35 mW. The technology used is a 70 nm GaAs mHEMT process from OMMIC.

Constant Mismatch Circles and Application to Low-Noise Microwave Amplifier Design

Constant input and output mismatch circles in the output load plane are introduced as the basis for low-noise amplifier design methodology. Optimum tradeoff between input and output matching levels results as the application of a design chart providing, at the same time, the corresponding stage transducer gain. The role of degenerative series feedback is studied and systematically embedded in the design procedure, thus providing a direct way to evaluate its optimum level.

Noise measure-based design methodology for simultaneously matched multi-stage low-noise amplifiers

A novel narrow-band design methodology for multi-stage low-noise amplifiers (LNAs) is presented which is based on noise measure and on appropriately designed reactive inter-stage networks. Design formulae are given, in particular, concerning the realisation of the latter networks in T and II configurations, so as to make possible a partially automated design algorithm. As a test vehicle of the presented procedure, the design and realisation of a three-stage K-band LNA is discussed and the corresponding measured results are shown.

Analysis, Design and Measurement of Active Low-Noise Terminations

Active terminations are helpful when dealing with planar antenna arrays. In fact, some antenna elements may be used as dummy ones to prevent electromagnetic field asymmetries. Such antennas should be terminated on loads that are as low noise as possible so as not to disturb the neighbouring active antennas. By using the proposed methodology, an active 50 Omega, low noise termination with an equivalent noise temperature of about 100 K at room temperature has been designed in the full C-Band frequency range. Measurements on the fabricated MMIC are given demonstrating a good agreement between the predicted 80-100 K minimum equivalent noise temperature and the measured one.

Determining optimum load impedance for a noisy active 2-port network.

The role of the impedance load when dealing with noisy two port networks is investigated. Its value acts directly on input and output return losses (IRL and ORL) that can be simultaneously achieved once input load has been fixed to an arbitrary value. A novel design chart, obtained after examining constant mismatch circles, is introduced, where optimum trade-off between IRL and ORL is promptly identified. The role of degenerative source feedback is highlighted to improve IRL/ORL trade-off.

Harmonic matching design for triplers

In this paper a new approach to design frequency triplers is introduced. The technique is based on the closed-form synthesis of distributed matching networks which synthesize the desired load values at fundamental, second and third harmonic frequencies. Then to validate the introduced approach an active frequency tripler is designed and the resulting performances are reported.

Compensating Digital Attenuator Differential Phase Shift

Controlled attenuators are key elements in a phased arrays beam forming network and generally in all those systems requiring accurate control of the RF signals amplitude and phase. Therefore the realisation of constant- phase digital attenuators is essential to obtain advanced system performance. A reactive element has been inserted in the traditional T topology digital attenuator to obtain equiphase condition and design equations have been inferred for optimum design. A MMIC X-Band 5-BIT constant-phase attenuator system has been designed and realised as a test vehicle for the proposed methodology.

Freitag method application to PA stability test

The multi-device Power Amplifier even and odd-mode stability is being tested using the Freitag approach. Results are verified by means of the time domain response of a sample circuit. Limitations are discussed and a possible extension of the method is proposed.

A new test bench to measure dynamic output I/V characteristics of FETs

In this paper a new test bench for the measurement of FETs dynamic output I/V characteristics is presented. The characterization is carried out generating asymmetrical voltage signals at the gate of the device while the load at the drain terminal is varied. The experimental results obtained performing on-wafer measurements of a 1 mm GaAs PHEMT using the proposed test bench, successfully compare with those carried out utilizing a conventional pulsed system.