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Showing papers by "Oliver Ambacher published in 2013"


Journal ArticleDOI
TL;DR: A wireless sub-THz communication system near 237.5 GHz with one to three carriers and up to 100 Gbit/s with state-of-the-art active I/Q-MMIC at the Rx is demonstrated.
Abstract: A wireless communication system with a maximum data rate of 100 Gbit s−1 over 20 m is demonstrated using a carrier frequency of 237.5 GHz. The photonic schemes used to generate the signal carrier and local oscillator are described, as is the fast photodetector used as a mixer for data extraction.

1,037 citations


Proceedings ArticleDOI
17 Mar 2013
TL;DR: A single-input single-output photonic wireless link at 237.5 GHz with record 100 Gbit/s data transmission over 20 m with state-of-the-art active I/Q-MMIC at the receiver is demonstrated.
Abstract: We demonstrate a single-input single-output photonic wireless link at 237.5 GHz with record 100 Gbit/s data transmission over 20 m. We use an optical heterodyne I/Q transmitter and a state-of-the-art active I/Q-MMIC at the receiver.

74 citations


Proceedings ArticleDOI
19 May 2013
TL;DR: In this article, the authors present a very compact 0.28 × 0.55 mm2 six-stage terahertz monolithic integrated circuit (TMIC) using 35 nm gate length metamorphic high electron mobility transistors (mHEMTs).
Abstract: In this paper we present a very compact 0.28 × 0.55 mm2 six-stage terahertz monolithic integrated circuit (TMIC) using 35 nm gate length metamorphic high electron mobility transistors (mHEMTs). A linear gain of 20.3 dB at 610 GHz and more than 18 dB over the bandwidth from 557 to 616 GHz was achieved for a drain voltage Vd of only 0.6 V. The noise performance of the 35 nm mHEMT was investigated on the basis of a packaged H-band amplifier which achieved a small-signal gain of more than 20 dB between 220 and 300 GHz. The averaged measured noise figure was 6.1 dB which is to our knowledge the lowest published value of any MMIC technology in this frequency range. To determine the transistor reliability accelerated lifetime tests in air were done. Based on a 20 % gm_max degradation failure criterion a median time to failure of 1.8 × 105 h at a channel temperature of 75°C and VDS = 0.8 V was extrapolated

58 citations


Journal ArticleDOI
TL;DR: This paper presents a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps.
Abstract: Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (108 cm−2), in the case of hydrogen-treated ND seeding particles, to very high values of 1011 cm−2 for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa.

49 citations


Proceedings ArticleDOI
02 Jun 2013
TL;DR: The transmission of complex modulated data signals with data rates up to 30 Gbit/s is successfully realized using a 240 GHz wireless link based on active MMIC components as well as a characterization of the RF frontend based on S-parameter measurements and back-to-back signal transmission.
Abstract: The transmission of complex modulated data signals with data rates up to 30 Gbit/s is successfully realized using a 240 GHz wireless link based on active MMIC components. The paper presents the transmission of QPSK and 8-PSK modulated signals over a distance of 40 m as well as a characterization of the RF frontend based on S-parameter measurements and back-to-back signal transmission. The link quality is evaluated in terms of error vector magnitude (EVM) measurement. For a symbol rate of 10 GBd, the EVM measurement shows values of 10.3% and 15.2% for the QPSK and 8-PSK signal, respectively.

45 citations


Proceedings ArticleDOI
19 Dec 2013
TL;DR: Based on active millimeter-wave monolithic integrated circuits (MMICs), a pair of receiver and transmitter modules have been developed and used for wireless data transmission experiments at 240 GHz with data rates of up to 40 Gbit/s.
Abstract: Based on active millimeter-wave monolithic integrated circuits (MMICs), a pair of receiver and transmitter modules have been developed and used for wireless data transmission experiments at 240 GHz with data rates of up to 40 Gbit/s Both modules are driven with a subharmonic local oscillator, located at 120 GHz and feature broadband quadrature I/Q IF terminals The receiver module has a maximum conversion gain of 38 dB at 240 GHz The I/Q imbalance stays below 19 dB in the frequency range from 200 to 280 GHz The transmitter achieves a maximum output power of -36 dBm

36 citations


Journal ArticleDOI
TL;DR: In this paper, the static and dynamic properties of GaN-based high voltage transistors used for power switching applications are determined, and the GaN transistors on SiC and Si substrates are shown to deliver 1000 V breakdown and 95 A output current.
Abstract: We present results from GaN-based high voltage transistors used for power switching applications. The static and dynamic properties of transistors on SiC and Si substrates are determined. Overall, this technology is capable to deliver 1000 V breakdown and 95 A output current as well as a lower product of on-resistance and gate charge than conventional Si-based structures. Areas of further improvement in epitaxial growth and device processing are outlined in order to combine these high currents and high voltages in a single device. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

32 citations


Journal ArticleDOI
TL;DR: In this article, the authors report on recent results from their GaN transistor and circuit technology, which is characterized by state-of-theart performance, good uniformity and high yield as well as excellent long-term stability.
Abstract: We report on recent results from our GaN transistor and circuit technology. Epitaxial growth can be performed on either SiC or Si substrates in order to provide high-quality AlGaN/GaN heterostructures. These heterostructures are then utilized in order to realize transistors and integrated circuits ranging from high-voltage transistors for voltage conversion in efficient power switches, L/S-band power bars and X-band MMICs for next-generation communication systems, and finally W-band MMICs for radar applications. The technology is characterized by state-of-the-art performance, good uniformity and high yield as well as excellent long-term stability. In combination with the space compatibility we believe that this technology is ideal for space. X-band MMICs from Fraunhofer IAF are scheduled to have the first in-orbit demonstration of European GaN within the Proba-V mission which is planned to be launched in spring 2013.

26 citations


Journal ArticleDOI
TL;DR: In this paper, a new concept for the low-frequency dispersion aspect of large-signal modeling of microwave III-V field effect transistors is presented, which circumvents the integrability problem between the small signal transconductance GmRF and the output conductance GdsRF by means of an integral formulation and simultaneously yields a proper description of the drain channel current in the small and large signal regime.
Abstract: A new concept for the low-frequency dispersion aspect of large-signal modeling of microwave III-V field-effect transistors is presented. The approach circumvents the integrability problem between the small-signal transconductance GmRF and the output conductance GdsRF by means of an integral formulation and simultaneously yields a proper description of the drain channel current in the small- and large-signal regime. In the theoretical description of the approach and in an extraction example of an AlGaN/GaN HEMT, it is shown that three independent 2-D nonlinear quantities determine the intrinsic drain channel current (GmRF, GdsRF, and dc current). The concept is transferred to the modeling of the nonlinear charge control, where the integrability problem between the large-signal charge functions and the small-signal intrinsic capacitance matrix (Cgs, Cgd, and Cds) is addressed consistently under consideration of the charge control delays. For the large-signal modeling under pulsed-dc/RF excitation, the dc continuous wave (dc-CW) modeling approach is combined with the state-modeling concept using a superposition formula for drain current and charges, respectively. The new model is implemented in ADS using a 12- and 14-port symbolically defined device for both the dc-CW and pulsed-RF case, respectively. The model has been verified by comparison to measured CW and pulsed-RF load-pull and waveform data at 10-GHz fundamental frequency.

24 citations


Journal ArticleDOI
TL;DR: In this paper, a low-noise amplifier (LNA) module with a small-signal gain of 19.5 dB at 243 GHz and a 3 dB bandwidth of 40 GHz was developed for use in a millimeter-wave direct detection radiometer for earth remote sensing.
Abstract: For use in a millimeter-wave direct detection radiometer for earth remote sensing, we have developed a low-noise amplifier (LNA) module with a small-signal gain of 19.5 dB at 243 GHz and a 3 dB bandwidth of 40 GHz. The implemented three-stage LNA MMIC has been manufactured using a 50 nm gate length metamorphic HEMT (mHEMT) technology on 50 μm thick GaAs substrates. Each of the two on-chip integrated E-plane probe waveguide transitions offers a transmission loss of only 0.5 dB at 243 GHz including a 7.5 mm long WR-3.4 waveguide. Due to the low-loss packaging, the LNA module achieves a low noise figure of only 6.0 dB at room temperature.

23 citations


Journal ArticleDOI
TL;DR: In this paper, the development of AlGaN pin photodetectors sensitive in the UV range with different narrow band active regions is reported, where structures were grown by metalorganic vapor phase epitaxy on (0001) sapphire substrates using three-dimensional GaN as well as high temperature AlN nucleation.
Abstract: The development of AlGaN pin photodetectors sensitive in the UV range with different narrow band active regions is reported in this paper. Structures were grown by metalorganic vapor phase epitaxy on (0001) sapphire substrates using three-dimensional GaN as well as high temperature AlN nucleation. Very high specific detectivities of 1×1014 cm Hz0.5 W-1 can be achieved based on optimized growth conditions of undoped and doped AlGaN layers with an Al-content ranging from 0% up to 100%. The crack-free AlGaN layers have edge dislocation densities in the range of 5×109 cm-2. Based on the two different nucleation types, pin layer structures were grown and fabricated to UV-A (320 to 365 nm) and UV-C (< 280 nm) photodetectors. The electro-optical performance of these photodetectors measured on-wafer will be presented in this paper, supplemented by the data of a single photodetector chip mounted in a TO 18 package.

Proceedings ArticleDOI
02 Jun 2013
TL;DR: In this paper, two millimeter-wave monolithic integrated circuit (MMIC) low-noise amplifiers (LNA), operating in the frequency range between 58 and 110 GHz and 74 and 110GHz, respectively, are presented.
Abstract: Two millimeter-wave monolithic integrated circuit (MMIC) low-noise amplifiers (LNA), operating in the frequency range between 58 and 110 GHz and 74 and 110 GHz, respectively, are presented. The W-band amplifiers employ a three-stage design in a 50nm InGaAs mHEMT technology and were optimized for minimum DC power consumption, using 2×10 and 2×5 μm transistors. For optimum bias conditions the first amplifier achieved a linear gain of more than 16.4dB and a noise figure of less than 2.8 dB over the whole W-band, whereas the second amplifier operates in the frequency range between 80 to 110 GHz with a linear gain of over 14.5 dB and a noise figure of less than 3.3 dB. The best achieved noise figure is 2.1dB and the maximum gain is about 23dB. LNA 1 yields a noise figure of 3 dB and a gain of 8.9dB at an operation frequency of 106 GHz, whilst only consuming 0.9mW of DC power.

Journal ArticleDOI
TL;DR: In this article, single and doubly clamped unimorph NCD-on-AlN micro-resonators were fabricated and then characterized by laser vibrometry towards their flexural resonant frequencies in the range of 0.1-20 MHz to deduce their mechanical properties.
Abstract: Micro electromechanical systems are a matter of intense research pursuing to replace silicon and III–V semiconductor-based components in prospective radio frequency communication devices. Due to their unique material properties, microstructures combining doped nano-crystalline diamond (NCD) and AlN thin films are promising for piezo-actuated microsystems in order to increase operating frequencies. In this work, single and doubly clamped unimorph NCD-on-AlN micro-resonators were fabricated and then characterized by laser vibrometry towards their flexural resonant frequencies in the range of 0.1–20 MHz to deduce their mechanical properties. Enhancements in the structural properties of an AlN piezo-actuator united with an advanced elasticity of nano-diamond electrode lead to superior mechanical parameters of the resulting unimorphs. These allow for the fabrication of flexural resonant microsystems with a potential to extend the operating frequencies well above 1 GHz.

Journal ArticleDOI
TL;DR: In this paper, the fabrication and performance of common-source (CS) and common-gate transistors for operation at millimeter-wave frequencies are presented, and the advantages of the dual-gate (DG) devices in power gain over the CS high electron mobility transistors are discussed.
Abstract: In this paper, the fabrication and performance of common-source (CS) and common-gate transistors for operation at millimeter-wave frequencies are presented. The AlGaN/GaN devices have a gate length of 100 nm and yield a high maximum transconductance of above 550 mS/mm with a very low contact resistance of less than 0.12 Ω·mm. The baseline technology with its optimized epitaxial structures and their transition frequency of more than 80 GHz allows reproducible designs for monolithic microwave integrated circuits up to the W-band frequency range (75-110 GHz). In addition, GaN dual-gate (DG) devices were developed for substantial improvement of the bandwidth of the devices and of the gain per stage on circuit level. This paper discusses the advantages of the DG devices in power gain over the CS high electron mobility transistors for millimeter-wave applications.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the thermal and plasma-assisted atomic layer deposition (ALD) and thermal ALD on two substrates, GaAs and Si, of different thermal expansion coefficients.
Abstract: Mechanical and electrical properties of Al2O3 films are compared for plasma-assisted atomic layer deposition (ALD) and thermal ALD on two substrates, GaAs and Si, of different thermal expansion coefficient. Films with stable chemical structure and mechanical residual stress could be produced by both techniques without inducing any damage to sensitive multiquantum-well structures. However, the as-deposited residual stress in the plasma ALD Al2O3 films is lower and decreases, while that in the thermal ALD films increases with the deposition temperature. Moreover, the stress hysteresis observed upon thermal cycles is much lower for the plasma ALD films compared to that for the thermal ALD films. The biaxial elastic modulus (BEM or stiffness parameter) increases with the deposition temperature for both ALD films, being higher for the plasma ALD than that for the thermal ALD at a given temperature. The higher BEM is reflected in better electrical properties of the films. Thus, the leakage current of metal–oxide–semiconductor capacitors with the plasma ALD-Al2O3 film is three orders of magnitude lower and the breakdown voltage 20% higher than that of the capacitors with the thermal ALD film.

Journal ArticleDOI
TL;DR: In this article, the authors describe the design and the realization of a fixed-frequency oscillator and voltage-controlled oscillator MMIC realized in an AlGaN/GaN HEMT technology with 100 nm gate length.
Abstract: This letter describes the design and the realization of a fixed-frequency oscillator and voltage-controlled oscillator (VCO) MMIC realized in an AlGaN/GaN HEMT technology with 100 nm gate length. Both oscillators achieve output power levels of almost 20 dBm without post-amplification. The oscillation frequency of the fixed-frequency oscillator is 65.6 GHz, while the VCO can be tuned from 65.6 to 68.8 GHz, which leads to a relative bandwidth of 5%. The phase noise of the VCO is -83 dBc/Hz at 1 MHz frequency offset.

Journal ArticleDOI
TL;DR: In this paper, an enhancement mode metal insulator semiconductor heterostructure field effect transistor on Si substrate with record on-current of 1.35 A/mm and threshold voltage of +0.82 V is demonstrated.
Abstract: GaN-on-Si transistors are regarded as a candidate for future power-switching applications. Beside the necessity to achieve enhancement mode behavior, on-resistance and maximum gate voltage are still limited for GaN-based transistors on Si substrate. Here, an enhancement mode metal insulator semiconductor heterostructure field effect transistor on Si substrate with record on-current of 1.35 A/mm and threshold voltage of +0.82 V is demonstrated. The corresponding gate current is still well below 1 mA/mm at 6.5 V gate voltage. By comparison of measured and simulated CV curves, the density of interface states introduced by the insulator is shown to be quasi-independent on etch damage and/or barrier material.

Proceedings ArticleDOI
19 Dec 2013
TL;DR: In this article, three power amplifier MMICs at Ka-band frequencies are reported, and they are realized using AlGaN/GaN HEMTs with a gate length of 100 nm.
Abstract: Three power amplifier MMICs at Ka-band frequencies are reported in this paper. The MMICs are realized using AlGaN/GaN HEMTs with a gate length of 100 nm. Two single-stage amplifiers are presented to highlight the potential of this GaN technology. A dual-stage amplifier is designed to reach high power performances. In continuous-wave (CW) operation, MMICs have provided up to 1.4 W, 2.4 W and 4.7 W of output power associated with (in this order) 41%, 33%, and 28% of PAE, respectively. The dual-stage MMIC delivered an output power higher than 4 W, associated with 27% of PAE and 9.8 dB of power gain from 29 GHz to 31 GHz.

Journal ArticleDOI
TL;DR: In this article, the dynamics of photoexcited carriers in GaInN/GaN quantum wells (QWs) grown on ammonothermal GaN, especially thermalization and recombination rates were measured by time-resolved photoluminescence (PL) and electroluminecence spectroscopy.
Abstract: In this work, we present measurements of the dynamics of photoexcited carriers in GaInN/GaN quantum wells (QWs) grown on ammonothermal GaN, especially thermalization and recombination rates Emission properties were measured by time-resolved photoluminescence (PL) and electroluminescence spectroscopy Due to the use of high quality homoepitaxial material, we were able to obtain very valuable data on carrier thermalization The temperature dependence of the QW energy observed in PL shows characteristic S-shape with a step of about 10 meV Such a behavior (related to thermalization and localization at potential fluctuations) is often reported for QWs; but in our samples, the effect is smaller than in heteroepitaxial InGaN/GaN QWs due to lower potential fluctuation in our material Absorption properties were studied by photocurrent spectroscopy measurements A comparison of emission and absorption spectra revealed a shift in energy of about 60 meV Contrary to PL, the QW energy observed in absorption decreas

Journal ArticleDOI
14 May 2013-Langmuir
TL;DR: A thermally induced functionalization process for gallium nitride surfaces with 1-alkenes shows very promising characteristics as functionalization for GaN based biosensors.
Abstract: A thermally induced functionalization process for gallium nitride surfaces with 1-alkenes is introduced. The resulting functionalization layers are characterized with atomic force microscopy and X-ray photoelectron spectroscopy and compared to reference samples without and with a photochemically generated functionalization layer. The resulting layers show very promising characteristics as functionalization for GaN based biosensors. On the basis of the experimental results, important characteristics of the functionalization layers are estimated and a possible chemical reaction scheme is proposed.

Journal ArticleDOI
TL;DR: The CIP stability of pH sensitive ion-sensitive field-effect transistors based on AlGaN/GaN heterostructures was investigated and stable sensitivity over several CIP cycles were achieved for optimized sensor structures.

Proceedings ArticleDOI
07 Mar 2013
TL;DR: In this article, a coalescent free-standing ultra-thin (as thin as 5.5 nm) platinum thermistors were used as an uncooled infrared detector, achieving a responsivity as high as 2 · 107 V/WA, an estimated noise equivalent temperature difference of 163 mK and thermal time constants on the order of 1 ms.
Abstract: We report the realization of coalescent free-standing ultra-thin (as thin as 5.5 nm) platinum layers deposited via plasma-enhanced atomic layer deposition and their characterization as an uncooled infrared detector. Such thin platinum thermistors enable a responsivity as high as 2 · 107 V/WA, an estimated noise equivalent temperature difference of 163 mK and thermal time constants on the order of 1 ms.

Proceedings ArticleDOI
02 Jun 2013
TL;DR: In this paper, a semi-reactively matched amplifier (SRAM) was proposed for wide bandwidth applications such as electronic warfare systems, which achieved small-signal gain of (18 ± 4)dB over the entire frequency range.
Abstract: This paper reports on a novel broadband amplifier architecture suitable for wide bandwidth applications such as electronic warfare systems. The proposed topology comprises a distributed active power splitter to function as a driver stage for a reactively-matched power amplifier. As a result, a purely resistive interstage impedance is obtained and therefore the proposed architecture allows wider bandwidth operation as compared to the conventional reactively-matched multistage topology. Due to the traveling wave amplifier character of the driver stage, the presented novel amplifier topology is named semi-reactively-matched amplifier. A 6GHz to 20GHz dualstage high power amplifier MMIC is designed and realized in order to demonstrate the capabilities of the new concept. The MMIC is based on a 0.25μm gate length AlGaN/GaN HEMT microstrip transmission line technology. It shows a measured small-signal gain of (18 ± 4)dB over the entire frequency range. The saturated output power is higher than 4.5W at 20GHz in continuous wave operation.

Proceedings ArticleDOI
11 Nov 2013
TL;DR: In this paper, a millimeter-wave monolithic integrated circuit (MMIC) was developed for use in a high-resolution radar system operating at 300 GHz, which achieved an instantaneous bandwidth of 40 GHz together with an outstanding range resolution of 3.7 mm.
Abstract: In this paper, we present the development of a millimeter-wave monolithic integrated circuit (MMIC) chipset for use in a high-resolution radar system operating at 300 GHz. The chipset consists of a frequency multiplier by twelve, a medium power amplifier, a high power amplifier and a fully integrated 300 GHz heterodyne receiver MMIC. The frequency multiplier and the two amplifier circuits have been realized using a 100 nm InAlAs/InGaAs based depletion-type metamorphic high electron mobility transistor (mHEMT) technology and achieve a saturated output power of approximately 20 dBm between 90 and 105 GHz. The 300 GHz receiver S-MMIC was fabricated using a more advanced 35 nm mHEMT technology and demonstrates a conversion gain of more than 7 dB between 270 and 325 GHz. All circuits were successfully packaged into millimeter-wave waveguide modules and used to realize a compact 300 GHz radar demonstrator, which delivers an instantaneous bandwidth of 40 GHz together with an outstanding range resolution of 3.7 mm.

Proceedings Article
19 Dec 2013
TL;DR: In this paper, the authors present a fully-scalable compact small-signal equivalent circuit model for AlGaN/GaN HEMTs with a gate length of 100 nm.
Abstract: In this paper, we present a fully-scalable compact small-signal equivalent circuit model for AlGaN/GaN HEMTs with a gate length of 100 nm. The compact model yields a parasitic shell topology and is scalable from two up to eight transistor-fingers and is valid for finger lengths from 15 μm to 100 μm. It accurately covers the frequency range from 100 MHz up to at least 110 GHz and a wide range of bias utilized for typical class-AB operation points of this technology. Both, direct parameter extractions as well as optimization-based techniques were applied for the determination of the model parameters.

Proceedings ArticleDOI
01 Oct 2013
TL;DR: In this paper, the development and fabrication of large area AlGaN/GaN-on-Si HFETs for the use in highly efficient fast-switching power converters is reported.
Abstract: This work reports the development and fabrication of large area AlGaN/GaN-on-Si HFETs for the use in highly-efficient fast-switching power converters. High performance is demonstrated by full characterization of static- and dynamic-parameters and a direct comparison to two commercial state-of-the-art silicon power devices. Compared to their silicon counterparts the GaN-device achieves by a factor of 3 lower static area specific on-state resistance RON×A, and by a factor of 3 lower static on-state resistance times gate charge product RON×Q. In switching tests the device achieves a low dynamic dispersion and low switching losses. Furthermore in this work a sophisticated measurement setup for characterization of dynamic parameters is developed and demonstrated. Characterization and test conditions are adapted for the use in fast-switching power converter applications.

Proceedings Article
19 Dec 2013
TL;DR: In this article, a low-noise amplifier based on a grounded coplanar waveguide (GCPW) technology utilizing 50 nm metamorphic high electron mobility transistors (mHEMTs) was developed.
Abstract: A compact H-band (220-325 GHz) low-noise amplifier circuit has been developed, based on a grounded coplanar waveguide (GCPW) technology utilizing 50 nm metamorphic high electron mobility transistors (mHEMTs). The realized four-stage cascode LNA achieved a small-signal gain of 31 dB at 243 GHz and more than 28 dB in the frequency range from 218 to 280 GHz. Coplanar topology in combination with cascode transistors resulted in a very compact die size of only 0.5 × 1.5 mm2. For low-loss packaging of the circuit, a set of waveguide-to-microstrip transitions has been realized on 50 μm thick GaAs substrates demonstrating an insertion loss of less than 0.5 dB at 243 GHz. The realized LNA module achieved a small-signal gain of 30.6 dB and a room temperature (T = 293 K) noise figure of 5.6 dB at the frequency of operation.

Journal ArticleDOI
TL;DR: In this paper, non-resonant piezoelectric micro-energy-harvesters based on corrugated membranes made from aluminium nitride were designed to respond efficiently to aperiodic mechanical impact at low repetition rates.
Abstract: In this work we report on non-resonant piezoelectric micro-energy-harvesters based on corrugated membranes made from aluminium nitride. These harvesters were designed to respond efficiently to aperiodic mechanical impact at low repetition rates. The piezogeneration efficiency of non-resonant systems was compared to conventional resonant devices like tensile stressed membranes and cantilevers. Special attention was paid to system properties that allow an operation at low frequencies in viscous media with high damping. Classical analytical modelling was employed to describe the corrugated microsystems with the aim to calculate the feasible energy outcome and to optimise electro-mechanical coupling.

Proceedings Article
19 Jun 2013
TL;DR: In this article, an active millimeter wave imaging system based on an ultra wide band FMCW radar with two frequency multipliers from 8 GHz to 96 GHz and an I/Q heterodyne receiver operating at W-band is presented.
Abstract: In this paper we demonstrate an active millimeter wave imaging system which is able to analyze the multilayer structure of dielectric materials with respect to defects such as voids or delamination. The system is based on an ultra wide band FMCW radar with two frequency multipliers from 8 GHz to 96 GHz and an I/Q heterodyne receiver operating at W-band. These circuits have been fabricated in-house using our 100 nm InGaAs mHEMT process [1].

Proceedings ArticleDOI
23 Dec 2013
TL;DR: In this paper, a two-tone intermodulation distortion behavior for the class-BJ power amplifier mode is studied, where the right phase combination of fundamental and second harmonic terminations leads to new output solutions where the power-efficiency is maintained optimum.
Abstract: For the first time a two-tone intermodulation distortion behavior for the class-BJ power amplifier mode is studied. The right phase combination of fundamental and second harmonic terminations lead to new output solutions where the power-efficiency is maintained optimum. However, no IMD behavior has so far been investigated for such terminations on a power transistor through load-pull investigation. In this paper, the class-BJ IMD analysis is investigated theoretically and experimentally through measurement activity on a 1.2 mm AlGaN/GaN power transistor under a two-tone excitation. The measurement results show that the standard class-B and reactive class-BJ solutions deliver same power-efficiency as well as same IM3 performance when driving the device into compression. However, when driving the device at 6 dB input power back-off, despite power and efficiency are similar with varying the terminations, the standard class-B state reveals better IM3 values of -40.5 dBc compared with the class-BJ solution of -31.8 dBc.