Spyridon Pavlidis

High resolution aerosol jet printing of D- band printed transmission lines on flexible LCP substrate

In this paper, aerosol jet printing technology is assessed for D-band RF applications for the first time. It describes the fabrication process, the technology assessment and the characterization of coplanar waveguides (CPW) lines and CPW to microstrip transitions on liquid crystal polymer (LCP) in the D band using silver nanoparticle aerosol jet printing process. Feature sizes with a resolution of 10 μm, which is the finest resolution among all of the digital printing technologies, were realized successfully. The conductivity of the sintered silver structures was half to that of bulk silver after sintering at temperatures up to 200 °C. Printed transmission lines demonstrated losses of 0.35 dB/mm at 110 GHz and 0.51 dB/mm at 170 GHz that are less than that of the insertion loss of the inkjet printing lines by an order of magnitude.

An X-band GaN HEMT hybrid power amplifier with low-loss Wilkinson division on AlN substrate

The high-power operation of a modular and compact power amplifier (PA) is demonstrated using gallium nitride (GaN) transistors and power-combining networks implemented on an aluminum nitride (AlN) substrate. The power-combining network, tuned for X-Band operation, includes matching circuits and Wilkinson power dividers (WPDs) with tantalum nitride (TaN) thin-film resistors. PA efficiency is increased by minimizing network thermal loss with the AlN substrate, which is an excellent thermal conductor. All system components were mounted on a metal carrier, and were interconnected through gold wire bonds. Large-signal measurements showed power added efficiency (PAE) of 44% and a peak output power of 6.5 W at 9.5 GHz with a 3 dB fractional bandwidth of 14%.

Integrated microfluidic cooling for GaN devices on multilayer organic LCP substrate

This paper presents, for the first time, an integrated microfluidic cooling scheme on multilayer organic liquid crystal polymer (LCP) substrate for high power X-band gallium nitride (GaN) devices and amplifiers. The channel is micromachined on LCP and a mixture of water and ethylene glycol is used as a coolant. A 3D electro-thermal model of the microfluidic channel has been created, which illustrates the advantage of having a micro-channel beneath LCP in the case of a static and moving fluid. Measurements were done at 10.5 GHz on a GaN power amplifier (PDC = 1.68 W, PAE = 15 %) that was placed both on LCP and on a microfluidic channel with a static fluid.

A feasibility study of flip-chip packaged gallium nitride HEMTs on organic substrates for wideband RF amplifier applications

Gallium nitride (GaN) technology has emerged as a frontrunner for high power electronics applications. By performing a survey of wire-bond and flip-chip-packaged GaN HEMTs on either AlN (a ceramic with high thermal conductivity) or LCP (an organic polymer with low thermal conductivity), the thermal and electrical limits of each package are established. Flip-chip packaging has the benefit of improving the bandwidth of a hybrid PA. Dies that were wire-bonded on AlN showed best performance, and were able to dissipate more than 6 W of power while remaining below the maximum operating junction temperature. On the other hand, flip-chipped devices on LCP were severely limited by thermal effects, even at a 10% duty cycle. This study motivates the need for advanced packaging techniques, such as integrated microfluidics or backside heat-sinking, in order to make LCP a viable material for high-power applications.

A hybrid GaN/organic X-band transmitter module

The design and implementation of a compact, flexible and lightweight X-band transmitter (Tx) module based on high-power gallium nitride (GaN) transistor technology and a low-cost organic package made from liquid crystal polymer (LCP) is presented. In-package measurements of the power amplifier (PA) at 8 GHz show a P.A.E.max of >31%, P1dB of 20 dBm and gain of 11.42 dB. A 4×1 patch antenna array was also fabricated on the same platform. Though no thermal management was used, an effective isotropically radiated power (EIRP) in excess of 20 dBm at 10 GHz was measured for the transmitter module, consisting of only a single-stage PA and antenna array, thus demonstrating that even greater performance can be achieved in the future.

A low-cost, encapsulated flip-chip package on organic substrate for wideband gallium nitride (GaN) hybrid amplifiers

In this paper, the authors present an embedded, low-cost packaging technique for high power gallium nitride devices. The package is based on flip-chip bonding to achieve a reduced parasitic inductance, easing the design for wideband amplifiers. The backside of the gallium nitride devices is connected to a heat sink by a second flip-chip process to improve thermal management. When realized on a low-cost organic substrate material with poor thermal characteristics, measurement results show that the proposed packaging technique can still achieve performance levels comparable to devices packaged on expensive, high thermal conductivity substrate materials, such as aluminum nitride. These results demonstrate a low-cost, high-performance and near-hermetically sealed packaging solution for gallium nitride devices.

Selectivity enhancement strategy for cantilever-based gas-phase VOC sensors through use of peptide-functionalized carbon nanotubes

A major challenge in the development of chemical sensors for volatile organic compounds (VOC) has been finding sensitive films, which selectively partition different volatile organics. This work presents a selectivity enhancement strategy using carefully chosen peptides to preferentially interact with different VOCs based on the polarity of the analytes. Carbon nanotubes (CNT) grown at low-temperature are used as a scaffold for the peptides. The CNTs are grown on top of mass-sensitive cantilever-based sensors and provide a large surface area for peptide binding, thus helping to increase the sensitivity of the sensors. Tests show that the peptides do in fact interact differently with VOCs based on the polarity of the compound. Achieved detection limits are in the low parts-per-million range.

Investigation of surface roughness effects for D-band SIW transmission lines on LCP substrate

This paper studies the influence of surface roughness on the performance of substrate integrated waveguide (SIW) structures in D-band (110–170 GHz). SIW structures are fabricated in a flexible low-cost/loss organic substrate, liquid crystal polymer (LCP), after polishing the material surface. The fabrication realizes a minimum feature size of 20 μm. The average insertion loss of the polished SIWs in D-band is measured to be 0.33dB/mm, showing an average 0.35 dB/mm improvement compared with SIWs in the raw substrate, without affecting the quality of the impedance match. Based on the modeling result, simulation is able to predict the loss under different surface roughness conditions, which is verified with measurements. Therefore, both fabrication and modeling solutions are provided to facilitate future high-frequency designs of SIW-based devices. This is the first paper that demonstrates the loss of SIW to be comparable to that of microstrip in the D-Band.

Encapsulated Organic Package Technology for Wideband Integration of Heterogeneous MMICs

The heterogeneous integration of silicon germanium (SiGe) and gallium arsenide (GaAs) technologies is presented using a novel encapsulated packaging approach with organic laminates. The combination of unique and optimally matched interconnects for each die, and the low-loss nature of the organic substrates, provides wideband performance and system design flexibility. A hybrid receiver front-end is realized on multilayer Rogers RO3003 to demonstrate this concept, incorporating a flip-chip bonded SiGe low-noise amplifier and a ribbon-bonded GaAs mixer. The simulated 3-dB bandwidth of the receiver is 4.5–14.5 GHz with a maximum conversion gain of 1.2 dB. Measured results for the packaged module show a 4–14-GHz 3-dB bandwidth and 0.9-dB maximum conversion gain. These results validate that the package is indeed low loss and preserves system performance over the entire bandwidth. The receiver also exhibits a double side band NFmin of 4 dB and a maximum

Direct correlation between potentiometric and impedance biosensing of antibody-antigen interactions using an integrated system

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