The handset market now represents the largest global market for RF semiconductors and components. This has attracted large-scale investments and development efforts focused on optimizing the RF architectures in the front-end of a cell phone.The handset is no longer simply a device for voice communications, but a complex portable multimedia communications center that among other things can play music, videos, download e-mail, or assist in navigation in unfamiliar locations.The enabling technology for this unprecedented growth has been integration. Using innovative design and packaging techniques, RF engineers have been able to drive down the size and cost of the critical front-end functions, while simultaneously, significantly improving performance.The discrete RF component count in the cell phone front-end has decreased rapidly as equipment manufacturers have continued to demand ever higher levels of modular solutions. The ultimate objective is an all encompassing "radio module". This paper examines the architectural changes that have already occurred and the likely development path for the future.

In this paper we present experimental results of the different reflection and transduction characteristics for transducers that have sampling rates of 1/3/spl lambda/, 3/8/spl lambda/, 2/5/spl lambda/, 3/7/spl lambda/, 5/12/spl lambda/, and 5/14/spl lambda/. Directivity tests on the different structures built on quartz and LiTaO/sub 3/ were performed and compared. Wide band measurements of all transducers were taken as well. These measurements suggest the possibility of implementing a DSPUDT filter with mixed sampling rates in order to suppress unwanted spurious modes like group and bulk wave modes. As a result, a table with the best combinations of sampling rates for high frequency (above 550 MHz) and low frequency (below 550 MHz) DSPUDT filters on ST-quartz and Y112-LiTaO3 was generated. This table was used to implement a 916.5 MHz filter in ST-QUARTZ, and a 960 MHz and 350 MHz filter on Y112-LiTaO/sub 3/.

The carboxylic acid groups of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were derivatized in the solid state using a procedure resulting in esterification by trifluoroethanol vapour. X-ray photoelectron spectroscopy analyses indicate that stoichiometric reaction with PAA was reached after 10 h. However, PMAA did not attain a yield greater than 60%, an effect rationalized in terms of steric hindrance. It is postulated that steric restraints are imposed by conformational inflexibility related to the pendant methyl group within isotactic portions of the chain.

A Reactive Ion Etch (RIE) process selected to fabricate high-frequency SAW devices is presented in this paper. RIE is commonly used in semiconductor IC fabrication to achieve very large scale integration because of its control of metal line width and profile as well as high yield. In this work, BCl3/Cl-2 chemistry is used to pattern aluminum electrodes on quartz substrates. Various process parameters such as rf power, system pressure, etch time and gas flow are investigated. Finally, an optimized etch process is established for certain critical submicron geometries down to 0.5 mu m. The RIE process produces SAW devices having electrodes with steep sidewalls. This increases sidewall reflectivity. The SAW devices are plasma etched to achieve desired center frequency, bandwidth (BW), and insertion loss (IL) with high production yield. An aluminum etch rate of 1000-2000 Angstrom/min. is observed. A controlled etch rate is accomplished at low rf powers (< 150 Watts). Higher rf power settings lead to resist damage and reflow. This paper also details a wet etch vs. RIE etch process comparison.

This paper presents a method of precise frequency trimming of Surface Acoustic Wave (SAW) devices using Reactive Ion Etching (RIE). The SAW devices are fabricated on quartz wafers and trimmed down in frequency by removing part of the quartz substrate between the electrodes, thus achieving the specified center frequency. A controlled frequency shift in the range of 10 kHz to 400 kHz is demonstrated. It has been observed that quartz etch rates of <100 /spl Aring//min. can be controlled, resulting in very low frequency shifts. Also, presealed hybrid and surface mount parts have been successfully trimmed to achieve a desired center frequency. Various parameters and test results are presented with no significant change in insertion loss or bandwidth observed. This method is simple and cost effective in high-volume SAW device production. Finally, a viable low-cost, high-volume production method of SAW device fabrication using this trimming process is demonstrated.

Recent negotiations between the United States and the former Soviet Union have resulted in agreements to aggressively reduce our respective nuclear weapon stockpiles. This is a very long-term activity that involves dismantlement, interim storage, and processing of a variety of components and materials. In addition, the end of the Cold War followed by the abrupt shutdown of a significant portion of the weapons complex in the United States has left tons of excess plutonium in various forms in storage for extended periods of time with resulting serious safety concerns. While long-term storage of plutonium in any form requires monitoring to mitigate safety, security, and nonproliferation concerns, the weapon dismantlement phase also requires monitoring for identification and verification without revealing design information. Clearly, the need for sensitive, noninvasive, and rapid monitoring techniques is highly desirable. Acoustic resonance spectroscopy (ARS) may emerge as one such technique; indeed, ARS has already been proven in a number of applications to date including Chemical Weapons Treaty verification and determination of waste drum pressurization and it is being investigated as a method to detect changes in sealed weapon component containers.

A new family of Dithered Single-Phase Unidirectional Transducer (DSPUDT) configurations is described. These structures are comprised of uniform width single-level electrodes on a non-uniform grid. They are an extension of the uniformly-sampled 3λ/8 and 5λ/8 double-level SPUDT configurations introduced in 1992. Instead of employing a double-level metalization, unidirectionality is achieved in these new structures by dithering the position of the electrodes. This technique is very powerful as it allows the reflectivity function in the transducer to be implemented in a near analogue fashion, rather than a discrete approximation. In addition to mean sampling rates of 3λ/8 and 5λ/8, other sampling rates are considered of the general form mλ/n and (1-m/n)λ, where m and n are integers and m⩽n/2. These additional sampling rates provide additional flexibility for making design tradeoffs in the minimum critical geometry, implemented coupling and reflection coefficients, and undesired out-of-band responses in the transducer. Using combinations of these sampling rates, filters with excellent rejection characteristics can be constructed. The large critical geometry's possible with these new transducers permits low-loss filters to be easily fabricated at frequencies in excess of 1 GHz with very linear group-delay and high out-of-band rejection

Conducting polymer materials have the potential for replacing metals in many electromagnetic shielding applications where the special properties of plastics and their composites are preferred to those of metals and other inorganic conductors such as carbon. There is also the whole field of radar signature management where there is a requirement for surfaces or layers with specified impedances. The authors presented results of preparing and characterising the conducting polymer polypyrrole (PP) grown on a cellulose (paper) substrate with prescribed impedance loadings. However, the use of textile materials as substrates is widely used in industrial processes and these materials offer more possibilities for control of a composite material. They report the fabrication and characterisation of PP-loaded fabrics, and their application in microwave absorbing structures. Unlike some other conducting polymers (such as polyacetylene) PP in its oxidised state has good stability in air and is robust with respect to the temperatures normally required for embedding in resin, for example. A brief summary is included of its formation and electronic properties. >

The results of a research and development effort designed to extend the bandwidth limitation of quartz-coupled resonator filters beyond a half percent are reported. The theoretical operation and design of coupled resonator filters are discussed from both a time-domain and frequency-domain point of view, with special attention devoted to the requirements for maximizing the filter bandwidth. Several devices extending over a range of frequencies are analyzed with a coupling of modes model, and then fabricated on rotated Y-cut quartz utilizing the X-propagating surface acoustic wave. Experimental and theoretical results are presented in both the time and frequency domain for filters with bandwidths up to 0.6%

The results of a wide bandwidth natural single phase unidirectional transducer (NSPUDT) quartz coupled resonator filter design effort are discussed. The resulting 850-MHz filter yields a symmetric frequency response, a bandwidth in excess of 0.4%, an ultimate rejection in excess of 50 dB and a turnover temperature of 5 degrees C which can be selectively placed between -25 degrees C and 75 degrees C depending on the rotated Y-cut angle of the quartz substrate. The transducers utilize asymmetric crystal orientations to achieve the unidirectionality with a simple single-level uniform two-electrodes-per-wavelength fabrication. Both theoretical model predictions and experimental results, along with a discussion of the effects of package parasitics, and measured turnover temperature data for several rotated Y-cut angles, are presented. Design considerations and several methods for increasing filter performance are discussed.<>

This paper presents an analysis of linguistic data that stems from a task-oriented dialogue. We demonstrate that certain referring expressions used in this setting are potentially ambiguous and indeterminate but do not lead to referential errors such as under– or over–population of the discourse representation. Three studies are reported which show that it is the skilled use of non-linguistic constraints, present in the task which facilitates successful reference. When these non-linguistic constraints are removed, skilled speakers are able to make a compensatory adjustment in the precision of their referring expressions. The ability of people to make this compensatory adjustment is an aspect of referential skill not revealed by more traditional task–oriented assessments.

British Polymer JournalVolume 19, Issue 3-4 p. 419-420 Book Review Metal-containing polymeric systems: Edited by J. E. Sheats, C. E. Carraher Jr and C. U. Pittman Jr, Plenum Press, New York, 1985. pp. x + 523, price $79.50. ISBN 0-306-41891-6 P. V. Wright, P. V. WrightSearch for more papers by this author P. V. Wright, P. V. WrightSearch for more papers by this author First published: May ‐ July 1987 https://doi.org/10.1002/pi.4980190346AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue3-4May ‐ July 1987Pages 419-420 RelatedInformation

This paper describes a completely new design approach for low-loss SAW transducers and components. This new approach utilizes special unconventional asymmetric crystal orientations. On these new orientations, which exist on conventional piezoelectric cryslals, simple single-level uniform twoelectrodes-per-wavelength transducers can exhibit a unidirectional response. In contrast to low-loss three-phase transducers, air-gap crossovers are not required and all electrode and gap widths are A/4. These new low-loss SAW transducers can thus be easily fabricated at high frequencies. The principle of operation of these new Natural Single-phase Unidirectional Transducers (NSPU DTs) is described. Experimental results for test structures are presented which confirm the existence of NSPUDT orientations on both quartz and LiNbO These results are compared with theoretical predic?fons of a newly developed Coupling-Of-Modes (COM) analysis for these devices. Agreement between experiment and theory is shown to be excellent.

Concepts for realizing superconductive convolvers capable of processing analog signals having bandwidths up to 10 GHz have been developed and are being implemented. A preliminary convolver structure with 19 taps and a 14-ns interaction length has recently been demonstrated. This device employs a superconductive transmission line as a low-loss delay element and superconductive tunnel junctions as n...

Superconducting niobium patterned to form strip transmission lines on sapphire and silicon dielectric substrates has been used to make passive delay lines, capacitively coupled resonators, and linear-FM chirp filters. Chirp filters with a 37.5-ns dispersion and 2.3-GHz bandwidth were implemented by nonuniformly tapping nondispersive delay lines using proximity directional couplers. Pulse compression tests using two complementary filters agree well with theory. The results demonstrate a technology which promises to provide analog signal processing with about an order of magnitude bandwidth increase over surface-acoustic-wave and acousto-optic devices.

A new technology for making analog signal-processing devices such as linear-FM chirp filters with time-bandwidth products up to 1000 is being developed using niobium stripline on sapphire. Preliminary results of delay lines, resonators, and a 25-ns, 2-GHz chirp filter will be presented.