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ABSTRACT: Oscillators that operate at 720 and 940 MHz and characterized over a temperature range of 25°C to 200°C and 250°C, respectively, are presented. The oscillators are designed on alumina substrates with typical integrated circuit fabrication techniques. Cree SiC MESFETs, thin film metal-insulator-metal capacitors and spiral inductors, and Johanson miniature chip antennas make-up the circuits. The output power and phase noise are presented as a function of temperature and frequency.
Wireless Sensors and Sensor Networks (WiSNet), 2011 IEEE Topical Conference on; 02/2011
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ABSTRACT: In this investigation sputtered silicon carbide annealed at 300°C for one hour is used as a conformal thin film package. A RF magnetron sputterer was used to deposit 500 nm silicon carbide films on gold metal structures on alumina wafers. To determine the reliability and resistance to immersion in harsh environments, samples were submerged in gold etchant for 24 hours, in BOE for 24 hours, and in an O<sub>2</sub> plasma etch for one hour. The adhesion strength of the thin film was measured by a pull test before and after the chemical immersion, which indicated that the film has an adhesion strength better than 10<sup>8</sup> N/m<sup>2</sup>; this is similar to the adhesion of the gold layer to the alumina wafer. MIM capacitors are used to determine the dielectric constant, which is dependent on the SiC anneal temperature. Finally, to demonstrate that the SiC, conformal, thin film may be used to package RF circuits and sensors, an LC resonator circuit was fabricated and tested with and without the conformal SiC thin film packaging. The results indicate that the SiC coating adds no appreciable degradation to the circuits RF performance.
Wireless Sensors and Sensor Networks (WiSNet), 2011 IEEE Topical Conference on; 02/2011
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ABSTRACT: This paper presents the first demonstration of oscillators operating above 400°C. The oscillators are fabricated with Cree SiC MESFETs and thin film, MIM capacitors and inductors on an alumina substrate. The tank circuit inductor is used to magnetically couple the oscillator signal to a coil placed 1 m from the circuit. The first oscillator is designed at 30 MHz, it operated at 27.8 MHz, and the second is designed to operate at 100 MHz, it operated at 90 MHz. The 30 MHz oscillator operated through 450°C and the 100 MHz oscillator operated through 470°C. The received power, frequency, and phase noise as a function of temperature is presented. In addition, the failure mechanism of the oscillator is discussed.
Microwave Conference Proceedings (APMC), 2010 Asia-Pacific; 01/2011
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ABSTRACT: A tunable folded slot antenna that utilizes varactor diodes is presented. The antenna is fabricated on Rogers 6006 Duriod with a dielectric constant and thickness of 6.15 and 635 ¿m, respectively. A copper cladding layer of 17 ¿m defines the antenna on the top side (no ground on backside). The antenna is fed with a CPW 50 ¿ feed line, has a center frequency of 3 GHz, and incorporates Micrometrics microwave hyper-abrupt 500 MHV varactors to tune the resonant frequency. The varactors have a capacitance range of 2.52 pF at 0 V to 0.4 pF at 20 V; they are placed across the radiating slot of the antenna. The tunable 10 dB bandwidth of the 3 GHz antenna is 150 MHz. The varactors also reduce the size of the antenna by 30% by capacitively loading the resonating slot line. At the center frequency, 3 GHz, the antenna has a measured return loss of 44 dB and a gain of 1.6 dBi. Full-wave electromagnetic simulations using HFSS are presented that validate the measured data.
Radio and Wireless Symposium (RWS), 2010 IEEE; 02/2010
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ABSTRACT: This paper describes an effort to develop a thin film packaging technology for microfabricated planar antennas on polymeric substrates based on silicon carbide (SiC) films deposited by physical vapor deposition (PVD). The antennas are coplanar waveguide fed dual frequency folded slot antennas fabricated on liquid crystal polymer (LCP) substrates. The PVD SiC thin films were deposited directly onto the antennas by RF sputtering at room temperature at a chamber pressure of 30 mTorr and a power level of 300 W. The SiC film thickness is 450 nm. The return loss and radiation patterns were measured before and after the SiC-coated antennas were submerged into perchloric acid for 1 hour. No degradation in RF performance or physical integrity of the antenna was observed.
Radio and Wireless Symposium (RWS), 2010 IEEE; 02/2010
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ABSTRACT: A system to measure the return loss, radiation patterns and gain of planar antennas with GSG or GS probe connects at high temperatures has been presented. Antennas can be heated to 600degC and a radiation sweep of 360deg is possible. The return loss, radiation patterns and gain of a FSA have been presented on Styrofoam and ceramic heater/shuttle tile chucks at RT and 250degC. The antenna was measured on a Styrofoam chuck to show the effect the ceramic heater has on the measured data. The heater/shuttle tile chuck shifts the resonant frequency from its design frequency of 5 GHz to 4 GHz but its effect is minimal on the magnitude of Sn. The magnitudes of the gain at 90 and -90deg are not the same, which is due to the ceramic heater acting as a lens and focusing more radiation downward from the antenna through the ceramic heater. The phenomenon is also present on Styrofoam but not as predominant. The FSA and other omnidirectional antennas are the hardest to measure on this system and therefore this is a worst case test. Directional antennas such as patches would not be as impacted by the surrounding system.
Antennas and Propagation Society International Symposium, 2009. APSURSI '09. IEEE; 07/2009
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ABSTRACT: Reported is the first demonstration of an active antenna operating at 1 GHz and at temperatures above 200degC. A Clapp oscillator integrated with a slot-ring antenna generated and transmitted a 1 GHz signal from 25 to 270degC. The oscillation frequency varied by less than 4 over the temperature range.
Electronics Letters 05/2009; · 0.96 Impact Factor
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ABSTRACT: This paper presents the characteristics of coplanar waveguide transmission lines on R-plane sapphire and alumina over the temperature range of 25degC-400degC and the frequency range of 45 MHz-50 GHz. A thru-reflect-line calibration technique and open circuited terminated stubs are used to extract the attenuation and effective permittivity. It is shown that the effective permittivity of the transmission lines and, therefore, the relative dielectric constant of the two substrates increase linearly with temperature. The attenuation of the coplanar waveguide varies linearly with temperature through 200degC, and increases at a greater rate above 200degC.
IEEE Transactions on Advanced Packaging 03/2009; · 1.12 Impact Factor
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ABSTRACT: Folded slot antennas utilizing capacitive loading to reduce the physical size of the antenna while maintaining the original resonant frequency have been presented. Simulations illustrate that to decrease the size of the antenna the width of the radiating slot must also decrease, which limits the ability to fabricate this type of antenna. Also, as the size of the antenna decreases, the value of capacitor needed increases. Size reductions of 33 and 44% at 3 and 5 GHz, respectively, are demonstrated. The 10 dB BW and gain decrease as the size of the antennas increase.
Antennas and Propagation Society International Symposium, 2008. AP-S 2008. IEEE; 08/2008
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ABSTRACT: This paper presents an electrically small, coplanar waveguide fed, folded slot antenna that uses capacitive loading. Several antennas are fabricated with and without capacitive loading to demonstrate the ability of this design approach to reduce the resonant frequency of the antenna, which is analogous to reducing the antenna size. The antennas are fabricated on Cu-clad Rogers Duriod<sup>TM</sup> 6006 with multilayer chip capacitors to load the antennas. Simulated and measured results show close agreement, thus, validating the approach. The electrically small antennas have a measured return loss greater than 15 dB and a gain of 5.4, 5.6, and 2.7 dBi at 4.3, 3.95, and 3.65 GHz, respectively.
Radio and Wireless Symposium, 2008 IEEE; 02/2008
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ABSTRACT: The dependency of planar folded slot antenna characteristics fabricated on alumina substrates over the temperature range of 25 to 400 C are presented. The 3.575 GHz antenna is fed by a 20 mm long, 50 CPW line (S = 130 and W = 60 μm), and there is no ground plane on the back side of the substrate. An on-wafer TRL calibration was used to deembed the CPW feed line for return loss measurements and to measure the increase in the effective dielectric constant and attenuation of the CPW lines as a function of temperature. The measured antenna characteristics show that the resonant frequency varies by less than 1%, the minimum return loss increases from 11 to 16 dB, the quality factor increases from 25.5 to 44.75, and the gain decreases by 1 dBi as temperature is increased from 25 C to 400 C. Finally, the effect of the measurement test setup on the measured radiation patterns is discussed.
IEEE Antennas and Wireless Propagation Letters 02/2008; · 1.37 Impact Factor
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ABSTRACT: The characterization of 99.6% poly crystalline alumina substrates and folded slot antennas has been presented. TRL calibrations were performed at temperatures of 25 to 400 degC over a frequency range from 0.5 to 50 GHz. The effective dielectric constant of the CPW on alumina substrates was determined to be relatively constant at 5.4 from 25 to 200 degC and then increased steadily to approximately 6 at 400 degC. The loss of the CPW lines increased as temperature and frequency increased as well noting that the increase in loss is even more profound as both the temperature and frequency increased simultaneously.
Antennas and Propagation Society International Symposium, 2007 IEEE; 07/2007
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ABSTRACT: This paper describes an effort to develop microfabricated planar antennas that utilize a plasma enhanced chemical vapor deposition (PECVD) based silicon carbide (SiC) thin film packaging technology to provide chemical resistance. The antennas are coplanar waveguide fed dual frequency folded slot antennas fabricated on alumina substrates that utilize a self matching impedance technique. The PEVCD SiC thin film was deposited at 300degC at a chamber pressure of 900 mTorr and a power level of 100 W. The SiC film thickness was 450 nm. The antennas exhibit a return loss better than -15 dB at 5 and 7 GHz before and after SiC deposition. The gain of the antennas is 3 dB at 5 and 7 GHz before and after SiC deposition. The SiC-coated antennas were submerged into Au etchant for over a 24 hr period with no degradation in RF performance or physical integrity
Wireless and Microwave Technology Conference, 2006. WAMICON '06. IEEE Annual; 01/2007
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Wireless and Microwave Technology, 2005. WAMICON 2005. The 2005 IEEE Annual Conference; 02/2005
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Wireless and Microwave Technology, 2005. WAMICON 2005. The 2005 IEEE Annual Conference; 02/2005
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ABSTRACT: The authors report the miniaturization of a planar Wilkinson power divider by capacitive loading of the quarter wave transmission lines employed in conventional Wilkinson power dividers. Reduction of the transmission line segments from /spl lambda//4 to between /spl lambda//5 and /spl lambda//12 are reported here. The input and output lines at the three ports and the lines comprising the divider itself are coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS), respectively. The 10 GHz power dividers are fabricated on high resistivity silicon (HRS) and alumina wafers. These miniaturized dividers are 74% smaller than conventional Wilkinson power dividers, and have a return loss better than +30 dB and an insertion loss less than 0.55 dB. Design equations and a discussion about the effect of parasitic reactance on the isolation are presented for the first time.
IEEE Microwave and Wireless Components Letters 02/2002; · 1.72 Impact Factor
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ABSTRACT: Ka-band MEMS doubly anchored cantilever beam capacitive shunt devices are used to demonstrate a MEMS SPDT switch fabricated on high resistivity silicon (HRS) utilizing finite ground coplanar waveguide (FGC) transmission lines. The SPDT switch has an insertion loss (IL), return loss (RL), and isolation of 0.3 dB, 40 dB, and 30 dB, respectively, at Ka-band.
Antennas and Propagation Society International Symposium, 2002. IEEE; 02/2002
