A hardware detector for constant envelope quadrature- quadrature phase-shift keying (CEQ2PSK) is proposed. It uses appropriate hard decisions; yet, it achieves optimum probability of bit error performance, unlike the suboptimum detector of Saha and Birdsall. This optimum performance is verified through Monte Carlo computer simulations. Additionally, a more correct expression is given for the probability of bit error performance for CEQ2PSK, which gives the gain over nonconstant Q2PSK as 1.44 dB, rather than the previously published value of 1.76 dB.
K. Cartwright and E. Kaminsky, "An Optimum Hardware Detector for Constant Envelope Quadrature-Quadrature Phase Shift Keying (CEQ2PSK)", in IEEE Globecom 2005 Conf. Proc., St. Louis, MO, 28 Nov-2 Dec. 2005, paper 13_2, vol.1, pp. 393-396.