Digital to analogue converter implementation
AssigneeNortel Networks Limited
InventorsChristopher John Reed, Simon Gale
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Abstract
Current telecommunications device transmission stages require a significant number of analogue (DAC) components. The present invention provides a digital to analogue converter implementation for coupling to the digital signal processing (DSP) stage of the device and comprises a DAC and means to nullify the output of the DAC over part of the DSP data output period to produce a series of pulses corresponding to this data. The pulses are bandpass filtered to produce an analogue output signal at an intermediate frequency.
Claims11
A digital to analogue converter implementation for coupling to a telecommunications digital signal processing means having a predetermined data output period, the converter implementation comprising:
- a digital to analogue converter (DAC);
- a nullifying circuit arranged to nullify the output of said DAC over a predetermined part of each said data output period to form a first pulse corresponding in amplitude to the data value associated with said period;
- and
- a band pass filter coupled to said output;
- wherein said output is bandpass filtered at a non-fundamental frequency band to produce an analogue output signal in said frequency band.
A telecommunications transmitter comprising:
- a digital signal processing means having a predetermined data output period and comprising:
- an in-phase and a quadrature signal up-converter;
- and an in-phase and quadrature combiner connected to combine said up-converted in-phase and quadrature signals;
- a digital to analogue converter (DAC), having an input coupled to said combiner;
- a nullifying circuit arranged to nullify the output of said DAC over a predetermined part of each said data output period to form a pulse corresponding in amplitude to the data value associated with said period;
- and
- a bandpass filter coupled to said output;
- wherein said output is bandpass filtered at an intermediate or radio transmission frequency to produce an analogue output signal at said frequency.
A method for up-converting and analogue converting digital telecommunications transmission signals having a predetermined data output period for a telecommunications transmitter comprising a digital to analogue converter (DAC) having an output coupled to a bandpass filter, the method comprising the steps of:
- converting said digital signals to analogue signals using said DAC whilst nullifying the output of said DAC over a predetermined part of each said data output period to form a pulse corresponding in amplitude to the data value associated with said period;
- and
- bandpass filtering said output at a non-fundamental frequency band to produce an analogue output signal in said frequency band.
Dependencies are inferred from the claim text.