Patent ID: 8379760
Filing Date: 2013-02-19
Classification: H03M,H04B

Abstract:
1. A heterodyne transmitter constructed and arranged to receive a discrete time digital baseband input signal and convert it to a continuous time modulated signal at a radio frequency (RF) carrier frequency, the heterodyne transmitter comprising: a first sampling circuit constructed and arranged to receive the discrete time digital baseband input signal and to increase the sampling rate of the discrete time digital baseband input signal so as to produce a first interpolated signal, wherein the discrete time digital baseband input signal comprises digitized in-phase (I) and quadrature (Q) signals; a digital mixer responsive to the first interpolated signal and to a first digital mixing signal at a first mixing frequency, the digital mixer producing a digital signal at an intermediate carrier frequency representative of the discrete time digital baseband input signal; a second sampling circuit constructed and arranged to receive from the digital mixer the digital signal at an intermediate carrier frequency representative of the discrete time digital baseband input signal and to increase the sampling rate of the digitized signal at the intermediate carrier frequency representative of the discrete time digital baseband input signal so as to produce a second interpolated signal at the intermediate carrier frequency; and a sigma-delta modulator (SDM) digital to analog converter (DAC) receiving the second interpolated signal at the intermediate carrier frequency and an RF sampling signal, the SDM DAC constructed and arranged to process the digitized I and Q signals together in a complex noise-shaping filter having cross coupling between the I and Q signal paths and having a transfer function with complex-valued coefficients, so as to provide complex noise shaping of the digitized I and Q signals at the RF carrier frequency and produce a modulated signal at the RF carrier frequency.