R. Leberer

Bio: R. Leberer is an academic researcher. The author has contributed to research in topics: Amplifier & High-electron-mobility transistor. The author has an hindex of 6, co-authored 8 publications receiving 147 citations.

GaN MMIC based T/R-Module Front-End for X-Band Applications

Abstract: Amplifiers for a next generation of T/R-modules in future active array antennas are realized as monolithically integrated circuits (MMIC) on the bases of novel AlGaN/GaN HEMT structures. Both, low noise and power amplifiers are designed for X-band frequencies. The MMICs are designed, simulated and fabricated using a novel via-hole microstrip technology. Output power levels of 6.8 W (38 dBm) for the driver amplifier (DA) and 20 W (43 dBm) for the high power amplifier (HPA) are measured. The measured noise figure of the low noise amplifier (LNA) is in the range of 1.5 dB. A T/R-module front-end with mounted GaN MMICs is designed based on a multilayer LTCC technology.

An AlGaN/GaN class-S amplifier for RF-communication signals

Abstract: A Gallium-Nitride (GaN) current switched class-S amplifier for 450 MHz RF-signals is presented. A FPGA board is used to generate a band-pass delta sigma sequence with 1800 Mbit/s. This quasi digital signal is amplified to the required gate voltage swing for the HEMTs using a commercial available preamplifier. The AlGaN/GaN-HEMTs are driven in a high efficient switch mode. Linearity is preserved using the class-S architecture. Limits of this classical amplifier architecture are shown and discussed. Simulation results are presented and the realized class-S demonstrator is shown.

20W GaN HPAs for Next Generation X-Band T/R-Modules

Abstract: High power amplifiers for a next generation of T/R-modules for future X-band active array antennas are realized on the bases of novel AlGaN/GaN HEMT structures, which are epitaxially grown on SiC wafer substrates. Both, hybrid and monolithically integrated circuits are designed and realized as key elements for transmit chains. Based on hybrid designs excellent peak power levels of 23 W (43.6 dBm) with an associated power added efficiency (PAE) of 29% are realized. Over a bandwidth of 2 GHz (X-band) the output power levels are above 20 W. In a more sophisticated approach first monolithically integrated circuits (MMICs) are designed, simulated and fabricated using a novel via-hole microstrip technology. Output power levels of 20 W (43 dBm) with an associated PAE of 30% are measured on small size 12 mm2 chips. Highest ever reported maximum power added efficiency values of up to 36.5% are achieved

X-band T/R-module front-end based on GaN MMICs

Abstract: Amplifiers for the next generation of T/R modules in future active array antennas are realized as monolithically integrated circuits (MMIC) on the basis of novel AlGaN/GaN (is a chemical material description) high electron mobility transistor (HEMT) structures. Both low-noise and power amplifiers are designed for X-band frequencies. The MMICs are designed, simulated, and fabricated using a novel via-hole microstrip technology. Output power levels of 6.8 W (38 dBm) for the driver amplifier (DA) and 20 W (43 dBm) for the high-power amplifier (HPA) are measured. The measured noise figure of the low-noise amplifier (LNA) is in the range of 1.5 dB. A T/R-module front-end with mounted GaN MMICs is designed based on a multi-layer low-temperature cofired ceramic technology (LTCC).

Advanced High Power Amplifier Chain for X-Band T/R-Modules based on GaN MMICs

Abstract: Power amplifiers for a next generation of T/R-modules in future active array antennas are realized as monolithically integrated circuits on the bases of novel AlGaN/GaN HEMT structures. Both, driver and high power amplifiers are designed for X-band frequencies. The monolithically integrated circuits (MMICs) are designed, simulated and fabricated using a novel via-hole microstrip technology. Output power levels of 1.6 W (32 dBm) for the driver amplifier (DA) and 20 W (43 dBm) for the high power amplifier (HPA) are measured. An amplifier chain circuitry, with mounted GaN DA and HPA MMICs, is designed based on a multi-layer LTCC technology

A Compact X-Band Bi-Directional Phased-Array T/R Chipset in 0.13 $\mu{\hbox {m}}$ CMOS Technology

Abstract: This paper presents an X-band bi-directional T/R chipset in 0.13 m CMOS. The T/R chipset consists of a bi-directional gain amplifier (BDGA), a 5-bit digital step attenuator with two BDGAs for compensating the switch losses, and a 6-bit phase shifter using DPDT switches. The phase and attenuation coverage is 360 with the LSB of 5.625°, and 31 dB with the LSB of 1 dB, respectively. The circuit has a reference state gain of >;3.5 db, and the return losses of >;11 db at 8.5-10.5 GHz. The T/R chipset has a phase shift accuracy with the RMS phase error of ;6.5 dBm and the noise figure is <;7.5 db at 8.5-10 GHz. The chip size is 2.06 × 0.58 mm2 including pads, and the DC power consumption is 154 mW only in the BDGAs. To authors' knowledge, this is the X-band CMOS T/R chipset with the competitive RF performance compared to other device technologies, which has the smallest size and the lowest power consumption to-date.

An AlGaN/GaN HEMT-Based Microstrip MMIC Process for Advanced Transceiver Design

Abstract: A MMIC process in AlGaN/GaN technology for advanced transceiver design has been developed. The process is based on microstrip technology with a complete model library of passive elements and AlGaN/GaN HEMTs. The transistor technology in this process is suitable for both power and low noise design, demonstrated with a power density of 5 W/mm, and an NFmin of 1.4 dB at X-band. Process stability of subcircuits, complementary to power amplifiers and LNAs, in a transceiver system have been investigated. The results indicate that an all AlGaN/GaN MMIC transceiver is realizable using this technology.

RF class-S power amplifiers: State-of-the-art results and potential

Abstract: This paper reports recent results on a current-mode class-S power amplifier for the 450 MHz band, based on GaN-HEMT MMICs. We achieve a peak output power of 8.7 W for a single tone at 420 MHz, encoded in standard band-pass delta-sigma modulation with 1.68 Gbps sampling frequency. The respective efficiency is 34%. We find that these values strongly vary with coding efficiency of the modulation and reach 19 W with 59% for square-wave excitation. In order to clarify the potential of the PA in more detail, the S-class characteristics at power back-off and with varying oversampling ratio are presented as well.

Thermal Study of the High-Frequency Noise in GaN HEMTs

Abstract: The high-frequency noise performance of the GaN HEMT is studied for temperatures between 297-398 K. The access resistances RS and RD have a limiting effect on the noise performance, and in this paper, their temperature dependence is studied in detail for a 2 times 100 mum GaN HEMT. RS and RD show an increase of 0.71 and 0.86 %/K, respectively. The self-heating effect due to dissipated power is also studied to allow accurate intrinsic small-signal and noise parameter extraction. The thermal resistance is measured by infrared microscopy. Based on these results, a temperature dependent noise model including self-heating and temperature-dependent access resistances is derived and verified with measurements.

An X-Band AlGaN/GaN MMIC Receiver Front-End

Abstract: This letter presents an integrated AlGaN/GaN X-band receiver front-end. This is to the authors knowledge the first published results of an integrated AlGaN/GaN MMIC receiver front-end. The receiver uses an integrated SPDT switch to reduce size, weight and cost compared to circulator based transceiver front-ends. The integrated front-end has more than 13 dB of gain and a noise figure of 3.5 dB at 11 GHz.