Modem/radio IC architectures for ISM band wireless applications

π/4-DQPSK (differential quadrature phase shift keying) and F-QPSK modem/radio IC architectures are presented for unlicensed consumer electronics applications in the industrial, scientific, and medical (ISM) bands under FCC Part 15. An all-digital π/4-DQPSK modulator design, which is the new US digital cellular standard, provides significant size and current drain reduction over conventional DSP-based techniques. The low-cost F-QPSK modem/radio architecture offers higher power efficiency as well as higher spectral efficiency. Detailed circuits and design aspects are presented. The performance of each scheme employed in an intelligent frequency-hopping system is evaluated for a Rayleigh-fading/AWGN environment. Experimental results and computer simulations demonstrate that the proposed modem/radio architectures have both power and spectral advantages for the ISM band wireless applications. With the intelligent frequency-hopping scheme, the BER (bit error rate) performance can be improved by 5-10 dB as compared to conventional QPSK systems