Abstract: A novel apparatus and method for a fully digital quadrature architecture for a complex modulator. The complex modulator can substitute for existing prior art analog quadrature modulator structures and those based on a digital polar architecture (r, ?). The modulator effectively operates as a complex digital-to-analog converter where the digital inputs are given in Cartesian form, namely I and Q representing the complex number I+jQ, while the output is a modulated RF signal having a corresponding amplitude and phase shift. The phase shift being with respect to a reference phase dictated by the local oscillator, which is also input to the converter/modulator. Several embodiments are provided including modulators incorporating dual I and Q transistor arrays, a single shared I/Q transistor array, modulators with single ended and differential outputs and modulators with single and dual polarity clock and I/Q data signals.

Abstract: A novel apparatus for a low noise, high isolation, all digital transmit buffer gain control mechanism. The gain control scheme is presented in the context of an all digital direct digital-to-RF amplitude converter (DRAC), which efficiently combines the traditional transmit chain functions of upconversion, I and Q combining, D/A conversion, filtering, buffering and RF output amplitude control into a single circuit. The transmit buffer is constructed as an array of NMOS switches. The control logic for each NMOS switch comprises a pass-gate type AND gate whose inputs are the phase modulated output of an all digital PLL and the amplitude control word from a digital control block. Power control is accomplished by recognizing the impairments suffered by a pseudo class E pre-power amplifier (PPA) when implemented in a CMOS process. Firstly, the NMOS switches of the array have significant on resistance and thus can only draw a limited current from the an RF choke when the input waveform is high.