Apparatus and methods for digital-to-analog conversion

A method for converting a digit input signal to an analog signal for transmission, wherein the input signal can include more than one carrier signal, the method comprising the steps of:

• reducing a digital word length of the input signal to an intermediate word length, said step performed using a delta-signal loop;
• reducing the intermediate word length to produce a digital signal having a reduced word length, said step performed using another delta-sigma loop, wherein the step of reducing the intermediate word-length is performed at a frequency higher than a frequency at which the step of reducing a digital word length of the input signal is performed;
• adjusting a frequency of the digital signal to a transmitting frequency;
• and
• converting the frequency-adjusted digital signal to an analog signal.

A method for configuring a signal conversion apparatus for use in a radiofrequency transmitter, the method comprising the steps of:

• implementing a delta-sigma loop for operation at a given frequency to reduce a word length of a digital input signal to an intermediate-length;
• implementing another delta-sigma loop for operation at a higher frequency than the given frequency to reduce the intermediate length to a reduced word length;
• and
• implementing a digital tuner for up-converting the signal to a transmission radiofrequency.