Klaus Hirche

Analysis of the Survivability of GaN Low-Noise Amplifiers

This paper presents a detailed analysis of the stressing mechanisms for highly rugged low-noise GaN monolithic-microwave integrated-circuit amplifiers operated at extremely high input powers. As an example, a low-noise amplifier (LNA) operating in the 3-7-GHz frequency band is used. A noise figure (NF) below 2.3 dB is measured from 3.5 to 7 GHz with NF<1.8 dB between 5-7 GHz. This device survived 33 dBm of available RF input power for 16 h without any change in low-noise performance. The stress mechanisms at high input powers are identified by systematic measurements of an LNA and a single high electron-mobility transistor in the frequency and time domains. It is shown that the gate dc current, which occurs due to self-biasing, is the most critical factor regarding survivability. A series resistance in the gate dc feed can reduce this gate current by feedback, and may be used to improve LNA ruggedness

A Highly Survivable 3-7 GHz GaN Low-Noise Amplifier

A highly rugged low-noise GaN MMIC amplifier is presented that operates in the frequency band 3-7 GHz. A noise figure NF below 2.3 dB is measured from 3.5 to 7 GHz, with NF < 1.8 dB between 5 and 7 GHz. The survivability of the LNA was assessed by several stress-tests, injecting in the input up to 36dBm at 4 GHz for 16 hours. To the authors knowledge, these are the most severe survivability tests for these circuits reported in the literature so far

Optimized flip-chip interconnect for 38 GHz thin-film microstrip multichip modules

Flip-chip interconnects with 80 /spl mu/m bumps are optimized for 38 GHz by means of electromagnetic simulation. Thin-film microstrip is used as transmission-line on the carrier substrate. A compensation structure reduces reflections at the interconnect below -20 dB. Measurements of a passive structure and active chip modules proved the feasibility of this approach.

Highly Rugged 30 GHz GaN Low-Noise Amplifiers

GaN low-noise amplifiers (LNAs) operating at 27-31 GHz are presented in this letter. The monolithically integrated LNAs were fabricated using the process line of the Ferdinand-Braun-Institut. Noise figures of 3.7 to 3.9 dB were measured. The ruggedness of the LNAs was verified by noise measurements after stressing the LNA for up to 2 h with up to 33 dBm of input power. These conditions are among the most severe stress tests reported in literature. To the best of the authors knowledge, this is the first demonstration of a GaN LNA in this frequency region.

A 30-GHz Waveguide-to-Microstrip-Transition

Waveguide-to-microstrip transitions are essential elements for mm-wave transmitters and receivers. This paper presents an optimized transition with a relatively simple geometry and a minimum of compensation structures in order to mitigate sensitivity to fabrication tolerances. Almost 5 GHz bandwidth is achieved around 30 GHz, with an insertion loss of less than 0.25 dB. The transition can be implemented with a hermetic sealing.