Direct radio frequency generation using power digital-to-analog conversion
AssigneeLockheed Martin Corporation
InventorLeopold E. Pellon
Life of this patent
Estimating the term…
Abstract
An RF signal source receives wideband digital signals representing the instantaneous amplitude of the desired RF, and ΣΔ converts to ternary ΣΔ signals. The ternary ΣΔ signals are delayed in a transversal filter and the delayed signals are converted to currents for application to a traveling-wave summer for producing the desired RF. The traveling-wave summer may be a transmission line. The currents may be weighted with a filter response in order to limit the bandwidth of the RF signals. The RF may be coupled out through an antialiasing filter. The digital clocks may be delayed to correspond with the delays of the combiner, to impart directionality to the summed signals.
Claims22
An apparatus for generating radio-frequency signals directly from digital signals representing the instantaneous amplitude of the desired radio-frequency signals, said apparatus comprising:
- a sigma-delta encoder coupled to receive said digital signals, for generating sigma-delta encoded digital signals;
- a tapped digital shift register including an input port coupled to receive said sigma-delta encoded digital signals and also including a plurality of output ports at which delayed digital signals appear;
- a set of DAC cells, each cell of said set of DAC cells being coupled for receiving one of said delayed digital signals from said tapped digital shift register, for converting the corresponding tapped digital signal into a current, thereby generating a set of currents;
- a combiner coupled to said set of DAC cells, for combining said set of currents into a combined current representing reconstructed signal, said combiner comprising a first transmission line for receiving said set of currents, and at least a second transmission line having similar phase progression for delaying clock signals applied to said tapped digital shift register;
- and
- a set of static digital drivers and a set of digital control sources are coupled to said set of DAC cells, for weighting the individual currents of said set of currents so that said radio frequency signals are reconstructed within a finite passband.
A method for generating radio-frequency signals from first digital signals which represent the instantaneous amplitude of the desired radio-frequency signals, said method comprising the steps of:
- encoding said first digital signals with Sigma-Delta encoding to thereby produce Sigma-Delta encoded signals;
- delaying the bits of said Sigma-Delta encoded signals to thereby produce a plurality of differently delayed bits;
- converting said plurality of differently delayed bits into a plurality of currents constituting a set of currents;
- providing a combiner comprising a first transmission line for receiving said set of currents, and at least a second transmission line having similar phase progression for delaying clock signals associated with said delaying step;
- summing said currents of said set of currents using said combiner to produce said radio-frequency signals;
- and
- weighting said plurality of currents of said set of currents according to predetermined amplitude and phase representing a coefficient of a filter.
A method for generating radio-frequency electrical signals from digital signals representing the instantaneous amplitude of the desired radio-frequency signals, said method comprising the steps of:
- converting said digital signals representing the instantaneous amplitude of the desired radio-frequency signals into sigma-delta encoded digital signals;
- delaying said sigma-delta encoded digital signals by different amounts to a produce a plurality of variously delayed digital signals;
- converting each of said variously delayed digital signals into corresponding analog signals;
- providing a combiner comprising a first transmission line for receiving said analog signals, and at least a second transmission line having similar phase progression for delaying clock signals associated with said delaying step;
- and
- combining said analog signals with said combiner to produce the desired radio-frequency signals.
Dependencies are inferred from the claim text.