Abstract: Methods and devices for predistorted 12/4 Quadrature Amplitude Modulation that compensate for distortion from a nonlinear element. Modulator input bits are mapped (40) to a plurality of nonreturn-to-zero (NRZ) modulator control bit (20-30). The mapping is determined by desired points on a 12/4 QAM constellation. At least one phase shift device (4, 6) receives an input signal and at least one of the plurality of modulator control bit. At least two quaternary phase shift keying (QPSK) devices (8, 10) receive phase shifted signals from at least one phase shift device. Each of at least two QPSK devices receives at least one of the plurality of NRZ symbols. An attenuator (32) that attenuates a first QPSK signal outputted from a first QPSK device of the at least two QPSK devices. A summer (34) sums the attenuated first QPSK signal with a second QPSK signal. The second QPSK signal is outputted from a second QPSK device of the two QPSK devices. The summer outputs a predistorted 12/4-QAM signal.

Abstract: A 2N-QAM macrocell for generating constellations with 2N symbols, where N is the number of bits in the digital data word [D0:DN−1] applied to the macrocell. Since the digital data word is applied directly to the macrocell, the need for a digital mapping chip is thus eliminated thus reducing the complexity and power consumption of the circuit. An important aspect of the invention is that the 2N-QAM macrocell is amenable to being fabricated as a single microwave monolithic integrated circuit (MMIC) or integrated circuit (IC). As such, a QAM circuit can be formed from two MMICs; the 2N-QAM macrocell and a quadrature hybrid phase shifting device formed on separate MMIC to form a 2N-QAM circuit or one MMIC containing both the 0/90 degree phase shifter and the 2N-QAM circuit. The phase shifting device is used to provide the in-phase and quadrature phase components of the local oscillator signal.