ABSTRACT
The emerging technology of acoustic charge transport (ACT), which has enabled the implementation of powerful signal processors capable of handling high-speed RF and microwave signals in their natural analog domain, is reviewed. The development of ACT technology has led to the implementation of fully programmable analog signal processors capable of performing over 45 billion multiply-and-accumulate operations per second. These processors are finding application as adaptive filters and equalizers in a variety of commercial and military systems. The operation and performance capabilities of the ACT device are described, and seven applications now under development are discussed.
ABSTRACT
A surface acoustic wave (SAW) modulation system has been built, using a combination of a digital message sequence, an impulse driver, and different SAW modulator filters, for experimental testing of a wide variety of quadrature binary modulation schemes. The RF testbed is described and characterized for system distortion, dynamic range, and spurious responses, and system optimization is discussed. Nine different SAW modulator filters having different time- and frequency-domain responses were designed and fabricated for use in the system. Several of the designs are representative of new modulation schemes which offer better spectral confinement; and time-domain envelope uniformity than MSK. The results obtained with the designed SAW quadrature binary modulation system are presented. Excellent agreement between time- and frequency-domain measurements and theoretical predictions using the SAW modulation system are shown.
ABSTRACT
Approaches for designing surface acoustic wave (SAW) filters used in pulsed quadrature binary modulation (QBM) systems are presented. Several previously defined pulse shapes were implemented by a SAW filter and showed good QBM system performance with respect to modulation envelope nonuniformity (AM) and intersymbol interference (ISI). A new approach to QBM pulse shape definition using both frequency- and time-domain design criteria is described. This approach allows families of new pulse shapes having various levels of AM and spectral confinement to be designed. The approaches to the design equations are presented, and examples of specific pulse shapes and their implementation using SAW filters are given. Time- and frequency-domain results of iteratively designed pulse shapes for application to QBM systems are also presented, showing good performance.
