Saw Quadrature Binary Modulation System Applications

SAW filters have been applied to finite impulse response (FIR) modulation systems such as quadrature phase shift keying (QPSK) and minimum shift key (MSK) because they offer precise time-domain symbol shaping which allows many different types of systems to be implemented with varying spectral confinement, time-domain envelope uniformity, and intersymbol interference. By using the combination of a digital message sequence, an impulse driver, and different SAW modulator filters, a SAW modulation system has been designed for experimental testing of a wide variety of quadrature binary modulation schemes. The RF test bed is characterized for system distortion, dynamic range, and spurious responses. 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. This paper presents results of the designed SAW quadrature binary modulation system. Excellent agreement between time- and frequency-domain measurements and theoretical predictions using the SAW modulation system are shown. In addition, the hardware test bed design is described and system optimization is discussed