Reduced-size multilayer X-band filters with stacked resonators on a flexible organic substrate

This work presents the design of two four-pole, quasi-elliptic microwave bandpass filters with stacked open-loop resonators on an emerging low-loss organic dielectric material. Both filters are based on a multilayer microstrip structure that uses low-cost and flexible liquid crystal polymer substrates to produce a compact size. The first filter, which has a bandwidth of 17% at 9.3 GHz, was designed to control the high coupling strength between overlapped resonators without sacrificing its compact size. It has a measured 1.7 dB of insertion loss. The second filter uses the same topology, but its measured parameters include a bandwidth of 9% at 10.5 GHz and an insertion loss of 4.5 dB. To achieve the 9% bandwidth, two metallic patches were added between layers to limit the higher coupling between the overlapped resonators. Both bandpass filters have a footprint area reduction of at least 25% when compared to an equivalent single-layer, open-loop resonator filter.     

SAW COM-parameter extraction in AlN/diamond layered structures

Highly c-axis oriented aluminum nitride (AlN) thin piezoelectric films have been grown on polycrystalline diamond substrates by pulsed direct current (DC) magnetron reactive sputter-deposition. The films were deposited at a substrate temperature below 50/spl deg/C (room temperature) and had a typical full width half maximum (FWHM) value of the rocking curve of the AlN-002-peak of 2.1 degrees. A variety of one-port surface acoustic wave (SAW) resonators have been designed and fabricated on top of the AlN films. The measurements indicate that various SAW modes are excited. The SAW phase velocities of up to 11.800 m/s have been measured. These results are in agreement with calculated dispersion curves of the AlN/diamond structure. Finally, the coupling of modes parameters have been extracted from S/sub 11/ measurements using curve fitting for the first SAW mode, which indicate an effective coupling K/sup 2/ of 0.91% and a Q factor of about 600 at a frequency of 1050 MHz.     

Extending the bandwidth of magnetic tunnel junction sensors by abuffer amplifier

A simple buffer amplifier, consisting of a transistor in an emitter-follower configuration, is proposed to extend the bandwidth of magnetic tunnel junction read sensors. To maximize the bandwidth improvement, the buffer should be used on the slider or on the suspension as near to the slider as possible. The channel front-end (sensor, buffer, interconnect, and preamp) bandwidth is still somewhat limited by the RC product of the sensor resistance and shunt capacitance. However, the buffer can reduce the shunt capacitance to subpicofarad levels, allowing for bandwidths near 1 GHz. Merging the buffer with an interconnect and preamp gives a low-frequency signal-to-noise ratio (SNR) reduction at the preamp input of 0.1 dB and an SNR improvement of 5 to 10 dB over a no-buffer configuration for frequencies between 100 MHz and 1 GHz     

Flexible Film Bulk Acoustic Wave Filters toward Radiofrequency Wireless Communication

This paper presents a flexible radiofrequency filter with a central frequency of 2.4 GHz based on film bulk acoustic wave resonators (FBARs). The flexible filter consists of five air‐gap type FBARs, each comprised of an aluminum nitride piezoelectric thin film sandwiched between two thin‐film electrodes. By transfer printing the inorganic film structure from a silicon wafer to an ultrathin polyimide substrate, high electrical performance and mechanical flexibility are achieved. The filter has a peak insertion loss of ?1.14 dB, a 3 dB bandwidth of 107 MHz, and a temperature coefficient of frequency of ?27 ppm °C^?1. The passband and roll‐off characteristics of the flexible filter are comparable with silicon‐based commercial products. No electrical performance degradation and mechanical failure occur under bending tests with a bending radius of 2.5 mm or after 100 bending cycles. The flexible FBAR filters are believed to be promising candidates for future flexible wireless communication systems.     

Optimization of attenuation estimation in reflection for in vivo human dermis characterization at 20 MHz

In vivo skin attenuation estimators must be applicable to backscattered radio frequency signals obtained in a pulse-echo configuration. This work compares three such estimators: short-time Fourier multinarrowband (MNB), short-time Fourier centroid shift (FC), and autoregressive centroid shift (ARC). All provide estimations of the attenuation slope (/spl beta/, dB.cm/sup -1/.MHz/sup -1/); MNB also provides an independent estimation of the mean attenuation level (IA, dB.cm/sup -1/). Practical approaches are proposed for data windowing, spectral variance characterization, and bandwidth selection. Then, based on simulated data, FC and ARC were selected as the best (compromise between bias and variance) attenuation slope estimators. The FC, ARC, and MNB were applied to in vivo human skin data acquired at 20 MHz to estimate /spl beta//sub FC/, /spl beta//sub ARC/, and IA/sub MNB/, respectively (without diffraction correction, between 11 and 27 MHz). Lateral heterogeneity had less effect and day-today reproducibility was smaller for IA than for /spl beta/. The IA and /spl beta//sub ARC/ were dependent on pressure applied to skin during acquisition and IA on room and skin-surface temperatures. Negative values of IA imply that IA and /spl beta/ may be influenced not only by skin's attenuation but also by structural heterogeneity across dermal depth. Even so, IA was correlated to subject age and IA, /spl beta//sub FC/, and /spl beta//sub ARC/ were dependent on subject gender. Thus, in vivo attenuation measurements reveal interesting variations with subject age and gender and thus appeared promising to detect skin structure modifications.     

Measurements of the bulk, C-axis electromechanical coupling constant as a function of AlN film quality

Piezoelectric thin film AlN has great potential for on-chip devices such as thin-film resonator (TFR)-based bandpass filters. The AlN electromechanical coupling constant, K(2), is an important material parameter that determines the maximum possible bandwidth for bandpass filters. Using a previously published extraction technique, the bulk c-axis electromechanical coupling constant was measured as a function of the AlN X-ray diffraction rocking curve [full width at half maximum (FWHM)]. For FWHM values of less than approximately 4 degrees , K (2) saturates at approximately 6.5%, equivalent to the value for epitaxial AlN. For FWHM values >4 degrees , K(2) gradually decreases to approximately 2.5% at a FWHM of 7.5 degrees . These results indicate that the maximum possible bandwidth for TFR-based bandpass filters using polycrystalline AlN is approximately 80 MHz and that, for 60-MHz bandwidth PCS applications, an AlN film quality of >5.5 degrees FWHM is required.     

Bulk acoustic wave filters synthesis and optimization for multi-standard communication terminals

This article presents a design methodology for bulk acoustic wave (BAW) filters. First, an overview of BAW physical principles, BAW filter synthesis, and the modified Butterworth-van Dyke model are addressed. Next, design and optimization methodology is presented and applied to a mixed ladder-lattice BAW bandpass filter for the Universal Mobile Telecommunications System (UMTS) TX-band at 1.95 GHz and to ladder and lattice BAW bandpass filters for the DCS1800 TX-band at 1.75 GHz. In each case, BAW filters are based on AlN resonators. UMTS filter is designed with conventional molybdenum electrodes whereas DCS filters electrodes are made with innovative iridium.     

Microwave-absorbing properties of de-aggregated flake-shaped carbonyl-iron particle composites at 2-18 GHz

We have investigated the microwave-absorbing properties for different shapes and aggregated states of carbonyl-iron particles dispersed in epoxy resin matrix at various volume concentrations. Here, we discuss the requirements of lower reflection coefficient for the microwave permittivity /spl epsiv//sub r/=/spl epsiv/'-j/spl epsiv/' and permeability /spl mu//sub r/=/spl mu/'-j/spl mu/'. Compared to the aggregated sphere-shaped particles (SS), the de-aggregated flake-shaped carbonyl iron particles (FS) have higher permeability, lower permittivity, better filling characteristics in epoxy resin, and better absorbing properties in the frequency range of 2-18 GHz. For the FS composite with volume fraction of 0.60 at single-layer thickness of 1 mm, the calculated reflection loss at 2 GHz reaches -4.04 dB and the minimum reflection loss is -12.2 dB at 4.4 GHz, which indicates that the FS composite can be applied as a thinner microwave absorber in the S-band than if SS particles are used. The results also show that different volume concentrations can have high absorption at different wave bands, a fact on which the design of absorbing material can be based.     

Shear mode coupling and tilted grain growth of AlN thin films in BAW resonators

Polycrystalline AlN thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40/spl deg/ to 70/spl deg/ with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain AlN films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k/sub eff//sup 2/, of the fundamental thickness shear mode (TSO) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6/spl deg/.     

Inkjet Printed Metamaterial Loaded Antenna for WLAN/WiMAX Applications

In this paper, the design and performance analysis of an Inkjet-printed metamaterial loaded monopole antenna is presented for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed metamaterial structure consists of two layers, one is rectangular tuning fork-shaped antenna, and another layer is an inkjet-printed metamaterial superstate. The metamaterial layer is designed using four split-ring resonators (SRR) with an H-shaped inner structure to achieve negative-index metamaterial properties. The metamaterial structure is fabricated on low-cost photo paper substrate material using a conductive ink-based inkjet printing technique, which achieved dual negative refractive index bands of 2.25–4.25 GHz and 4.3–4.6 GHz. The antenna is designed using a rectangular tuning fork structure to operate at WLAN and WiMAX bands. The antenna is printed on 30 × 39 × 1.27 mm3 Rogers RO3010 substrate, which shows wide impedance bandwidth of 0.75 GHz (2.2 to 2.95 GHz) with 2 dB realized gain at 2.4 GHz. After integrating metamaterial structure, the impedance bandwidth becomes 1.25 GHz (2.33 to 3.58 GHz) with 2.6 dB realized gain at 2.4 GHz. The antenna bandwidth and gain have been increased using developed quad SRR based metasurface by 500 MHz and 0.6 dBi respectively. Moreover, the proposed quad SRR loaded antenna can be used for 2.4 GHz WLAN bands and 2.5 GHz WiMAX applications. The contribution of this work is to develop a cost-effective inject printed metamaterial to enhance the impedance bandwidth and realized the gain of a WLAN/WiMAX antenna.     

Optimization of single-phase,unidirectional transducers using three fingers per period

Electrode width controlled (EWC) single-phase, unidirectional transducers (SPUDT) is widely used for low loss surface acoustic wave (SAW) filters. The insertion loss and fractional bandwidth of the filters are strongly related to the reflectivity of EWC cells. In order to achieve wide band and low loss simultaneously, it is necessary to obtain higher reflectivity. The relationship between geometrical configuration of EWC cells and reflection coefficient, (and transduction coefficient as well) is studied. Simulation results indicate that the reflectivity of the EWC SPUDT cell could exceed 5% on a 128/spl deg/ Y-X lithium niobate (LiNbO/sub 3/) substrate. Using such structure, low loss SPUDT test filters without weighting are fabricated. The measured 3 dB bandwidth is 3.9% and the insertion loss is 2.9 dB. The theoretical calculation is verified by the experiment.     

Notch filters with novel microstrip, triangle-type resonators

A novel notch filter is designed and fabricated using novel microstrip, triangle-type resonators. The main advantage of the new notch filter is superior microwave characteristics in increasing the frequency of the third harmonic response, as demonstrated in simulations using fullwave electromagnetic (EM) simulators. The novel notch filter is demonstrated using the following frequency characteristics: central frequency f/sub 0/ = 1.975 GHz, a 3 dB bandwidth of 39.5%, and an insertion loss S/sub 21/ of -54.273 dB. The experimental and simulation results closely correspond to each other. The superior features of the proposed filter make it suitable for use in microwave communication systems and other applications.     

Development of an L-Band HTS Duplexer Sub-system with Novel Stepped Impedance Resonators

This paper presents the design, fabrication, and performance of a high-temperature superconductor (HTS) duplexer sub-system at L-band. The HTS duplexer sub-system contains a low noise amplifier (LNA) and an HTS duplexer. The HTS duplexer consists of a T-junction and two eight-pole filters with a bandwidth of 40 MHz centered at 1245 MHz and 1305 MHz, respectively. A novel, compact, and low radiation stepped impedance resonator was developed to reduce the parasitical coupling of the filters. The HTS duplexer was fabricated on a LaAlO₃ substrate. The insertion loss of the duplexer is 0.2 dB, and the 60/3 dB shape factor is better than 1.4:1. The out-of-band rejection and the isolation between the two channels of the duplexer are better than 60 dB. The noise figure of the HTS duplexer sub-system is 0.3 dB at 80 K.     

Contribution to the electromechanical and nonlinear properties of GaPO4 crystals

In the last decade, much attention has been given to piezoelectric crystals with large electromechanical coupling coefficient. The quartz homeotypes berlinite and gallium orthophosphate (GaPO/sub 4/), along with the calcium gallo-germanates such as langasite are representative of these crystals. The coupling coefficient k/sub 26/ associated with thickness-shear mode resonators is two times greater than that of quartz, increasing the spacing between the series and parallel resonance frequencies of resonators suitable for the frequency range from 1 to 100 MHz. This is important for some types of crystal oscillators and monolithic filters. The large electromechanical coupling coefficient also increases the difference between the temperature dependencies of the fundamental resonance frequency and its harmonics. In this paper, measured resonance frequency-temperature characteristics of the fundamental and third harmonics of selected rotated Y-cut GaPO/sub 4/ resonators vibrating in the thickness-shear mode are presented. Further attention is given to the measurement of some nonlinear properties of rotated Y-cut GaPO/sub 4/ resonators. Knowledge of such nonlinear interactions is important for the analysis of intermodulation phenomena in resonators, and for the application of GaPO/sub 4/ resonators in crystal oscillators, filters and other electronic devices.     

Micromachined 38 GHz cavity resonator and filter with rectangular-coaxial feed-lines

Micromachined, multilayer cavity resonators and filters at 38 GHz are demonstrated. Each layer is made of gold-coated silicon, structured by deep reactive etching. Two external coupling structures by coaxial feed lines are proposed to suit the fabrication process. The measured resonator gives an unloaded Q-value of 343 at 38 GHz. Methods to further improve the resonator quality-factors are discussed. The measured insertion loss of the filter is 1.01 dB, the 3 dB bandwidth is from 36.53 to 39.13 GHz, and the return loss is better than 215 dB over the frequency range from 37.0 to 38.6 GHz.     

Single crystal PMN-0.33PT/epoxy 1-3 composites for ultrasonic transducer applications

Lead magnesium niobate-lead titanate 0.67Pb (Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.33PbTiO/sub 3/ (PMN-0.33PT, abbreviated as PMN-PT) single crystals were used to fabricate PMN-PT/epoxy 1-3 composites with different volume fractions of PMN-PT ranging from 0.4 to 0.8. The electromechanical properties of the 1-3 composites were determined by the resonance technique. Theoretical modeling of the 1-3 composites matched quite well with the measured material properties. It was demonstrated that the thickness electromechanical coupling coefficients of the composites could reach as high as 0.8. A 2.4 MHz plane ultrasonic transducer was fabricated using a PMN-PT/epoxy 1-3 composite with 0.37 volume fraction of PMN-PT. It shows a -6 dB bandwidth of /spl sim/61% and an insertion loss of -14 dB.     

Determination of ZnO temperature coefficients using thin film bulk acoustic wave resonators

Thin film bulk acoustic wave (BAW) resonators have been the subject of research in RF microelectronics for some time. Much of the interest lay in utilizing the resonators to design filters for wireless applications. Some of the major advantages BAW devices present over other filter technologies in use today include size reduction and the possibility of on-chip integration. As the technology matures, the necessity to more fully characterize the performance of the devices and to develop more accurate models describing their behavior is apparent. In this investigation, the effects that temperature variations have on 1.8-2.0 GHz zinc oxide (ZnO)-based solidly mounted BAW resonators (SMRs) are studied. The average temperature coefficients of the series and parallel resonant frequencies of the fabricated devices are found to be -31.5 ppm//spl deg/C and -35.3 ppm//spl deg/C, respectively. The slight decrease in separation between the two resonant frequencies with temperature implies there is slightly less effective coupling with increased temperature. No definite trend is found describing the behavior of the quality factor (Q) of the resonator with temperature variations. With little temperature coefficient data for thin film ZnO available in the literature, the importance of an accurate model is evident. The resonator device performance is simulated using Ballato's electronic circuit model for acoustic devices on a SPICE-based platform. By virtue of the comparison between the predicted and measured device response, various material parameters are extracted.     

Single-mode rib optical waveguides on SOG/SU-8 polymer and integrated Mach-Zehnder for designing thermal sensors

This paper presents a successful design, realization,and characterization of single-mode rib optical waveguides on SOG/SU-8 polymers in order to highlight a new approach to designing heat sensors. The basic principle of this new thermal-sensing method relies on the differential thermal behavior regarding both acting arms of a micro Mach-Zehnder Interferometer(MZI). First, two families of single-mode straight rib waveguides composed of SOG/SU-8 polymers are analyzed. Hence, optical losses for TE/sub 00/ and TM/sub 00/ optical modes for structures on Si/SiO/sub 2//SU-8 have been estimated respectively as 1,36 /spl plusmn/ 0,02 and 2,01/spl plusmn/0,02 dB/spl middot/cm/sup -1/, while the second one composed of Si/SiO/sub 2//SOG/SU-8 presented losses of 2,33 /spl plusmn/ 0,02 and 2,95/spl plusmn/0,02 dB/spl middot/cm/sup -1/. Then, owing to modeling results, an experimental sensor is realized as an integrated device made up of SU-8 polymer mounted on a standard silicon wafer. When subjected to a radiant source, as a laser light (980 nm) is injected across the cleaved input face of the MZI, the significant change of output signal allows us to consider a new approach to measuring radiant heat flowrate. Experimental results are given regarding the obtained phase shift against the subjected thermal power. According to the modeling results, one can expect new highly sensitive devices to be developed in the next coming years, with advantageous prospective industrial applications.     

Longitudinal leaky SAW resonators and filters on YZ-LiNbO/sub 3/

The high-phase velocity (above 6100 m/s in and aluminum (Al) grating on lithium niobate (LiNbO/sub 3/)) of the longitudinal leaky surface acoustic wave (SAW) (LLSAW) mode makes it attractive for application in high-frequency SAW ladder filters in the 2-5 GHz range. We investigate the dependence of one-port synchronous LLSAW resonator performance or YZ-LiNbO/sub 3/ on the metallization thickness and metallization ratio, both experimentally and theoretically. Our results indicate a strong dependence of the Q factor and resonance frequency on the aluminum thickness, with the optimal thickness that produces the highest Q values being about 8%. The optimal thickness increases with the metallization ratio. The observed behavior is interpreted with the help of simulations using a combined finite element method (FEM)/boundary element method (BEM) technique. As an application, bandpass filters have been fabricated in the 2.8 GHz frequency regime, based on LL-SAWs. The synchronous resonators constituting the ladder filters operate in the fundamental mode. The filters feature low insertion losses below 3 dB and wide relative passbands of 4.5-5%.     

A simple dual-band microstrip-fed printed antenna for WLAN applications

A novel microstrip-fed dual-band printed antenna for wireless local area network (WLAN) is presented. The antenna comprises a rectangular and a circular radiating element, which generate two resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. The design was experimentally verified by constructing the antenna on a FR4 (ϵr = 4.4) dielectric substrate (47 mm x 26 mm x 0.76 mm) and measuring its impedance and radiation characteristics at both the bands. The measured 10 dB return loss (VSWR 2:1) bandwidth in the 2.4G Hz band is 550 MHz (2.1?2.65 GHz) and it covers the bandwidth required for 2.4 GHz WLAN. The 5.2/5.8 GHz resonant mode has a bandwidth of 950 MHz (5.15?6.1 GHz) covering 5.2/5.8 GHz WLAN bands. A rigorous experimental evaluation confirmed that the dual-band printed antenna maintained good radiation characteristics with minimum cross-polarisation levels.