Methods and systems for programmable digital up-conversion

An apparatus for performing digital up-conversion of a discrete-time baseband signal to a desired frequency, the apparatus comprising:

• a digital-to-analog converter (DAC) having a fixed effective sampling rate that is selected to be Fs;
• a complex tuner configured to tune the discrete-time baseband signal and produce a complex tuned discrete-time signal;
• a digital up-sampler configured to produce an up-sampled discrete-time signal by up-sampling the complex tuned discrete-time signal by N, N is an integer >=2, wherein the up-sampled discrete time signal includes a plurality of equally spaced apart images in the frequency domain;
• an image selection filter configured to select at least one image of the plurality of images and produce a filtered discrete-time baseband signal that is converted by the DAC from the discrete-time baseband signal to a continuous-time signal;
• a post-DAC filter configured to receive the continuous-time signal and select an image located at the desired frequency in the frequency domain;
• wherein an amount of tuning used in the complex tuner, and filter coefficients used in the image selection filter are each determined as a function of the selected fixed effective sampling rate of the DAC and the desired frequency of up-conversion.

A method of reconfiguring a digital up-converter to operate in a different frequency band, the method comprising:

• determining a tuning frequency for use in performing complex tuning of a discrete-time baseband signal to produce a complex-tuned discrete-time signal;
• determining filter coefficients for use in filtering an up-sampled discrete-time signal to isolate at least one image in the frequency domain of a plurality of images of the up-sampled discrete-time signal and produce a filtered discrete-time signal, the up-sampled discrete-time signal resulting from up-sampling the complex tuned time-discrete signal;
• wherein determining the tuning frequency and determining the filter coefficients comprise determining the tuning frequency and the filter coefficients as a function of:
• a fixed effective sampling rate of a digital-to-analog converter (DAC) used in the digital up-converter;
• and
• a desired frequency of up-conversion of the discrete-time baseband signal.