Parallel processing for programmable wideband digital modulation
View Patent ↗A circuit 30 for upsampling and upconverting a high rate signal that is divided into M in phase (I) symbols and M quadrature (Q) symbols. A Nyquist filter 32 upsamples by a factor of k each of the 2M symbols in parallel during one system clock period (CP). The filter 32 has a plurality of 2kM filter components 40, 42 , that each provides a continuous output. A plurality of multipliers 50, 52 each upconverts a filter component output with a carrier wave signal 46, 48 that is output from a numerically controlled oscillator 44 . A plurality of adders 54 each adds the output of two multipliers 50 to recombine corresponding I and Q samples to output kM samples during a CP. For continuous phase modulation, N parallel bits are input into the filter 32 , upsampled in one CP, and accumulated and modulated 82 in parallel in one CP. For analog processing, M (I) and M (Q) symbols are input into an FIR filter 77 a, 77 b for upsampling, and decimated at a MUX/DAC block 78 for subsequent analog upconversion.
1. A circuit for up-sampling a digital data stream comprising:
a system clock defining a clock period;
a polyphase Nyquist filter, having as parallel inputs during one clock period, M in-phase symbols and M quadrature symbols derived from a data stream, and outputting in parallel during one system clock period, k samples from each symbol, wherein k is an integer greater than one and M is an integer greater than or equal to one;
an oscillator defining Mk first carrier wave outputs and Mk second carrier wave outputs, wherein each first carrier wave output is in quadrature relation to a corresponding second carrier wave output;
a plurality of Mk in-phase multipliers, each in-phase multiplier having an input coupled to a first carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to an in-phase symbol;
a plurality of Mk quadrature multipliers, each quadrature multiplier having an input coupled to a second carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to a quadrature symbol;
a plurality of adders, each adder coupled to an output of an in-phase multiplier and an input coupled to an output of a quadrature multiplier; and
a plurality of filter adders each having an input coupled to an output of at least two polyphase filter components that are defined by the Nyquist filter.
2. A circuit for up-sampling a digital data stream comprising:
a system clock defining a clock period;
a filter, having as parallel inputs during one clock period, M in-phase symbols and M quadrature symbols derived from a data stream, and outputting in parallel during one system clock period, k samples from each symbol, wherein k is an integer greater than one and M is an integer greater than or equal to one;
an oscillator defining Mk first carrier wave outputs and Mk second carrier wave outputs, wherein each first carrier wave output is in quadrature relation to a corresponding second carrier wave output;
a plurality of Mk in-phase multipliers, each in-phase multiplier having an input coupled to a first carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to an in-phase symbol;
a plurality of Mk quadrature multipliers, each quadrature multiplier having an input coupled to a second carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to a quadrature symbol; and
a plurality of adders, each adder coupled to an output of an in-phase multiplier and an input coupled to an output of a quadrature multiplier;
wherein the oscillator is a numerically controlled oscillator (NCO) that generates the first and second carrier wave outputs from at least one of a lookup table and a coordinate rotation digital computer (CORDIC) algorithm.
3. A circuit for up-sampling a digital data stream comprising:
a system clock defining a clock period;
a filter, having as parallel inputs during one clock period, M in-phase symbols and M quadrature symbols derived from a data stream, and outputting in parallel during one system clock period, k samples from each symbol, wherein k is an integer greater than one and M is an integer greater than or equal to one;
an oscillator defining Mk first carrier wave outputs and Mk second carrier wave outputs, wherein each first carrier wave output is in quadrature relation to a corresponding second carrier wave output;
a plurality of Mk in-phase multipliers, each in-phase multiplier having an input coupled to a first carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to an in-phase symbol;
a plurality of Mk quadrature multipliers, each quadrature multiplier having an input coupled to a second carrier wave output of the oscillator and an input coupled to an output of the filter corresponding to a quadrature symbol; and
a plurality of adders, each adder coupled to an output of an in-phase multiplier and an input coupled to an output of a quadrature multiplier;
wherein the oscillator comprises M shift registers arranged in parallel, each shift register having an input coupled to an upconverting frequency signal f IF and an output coupled to at least one of a carrier wave lookup table and a coordinate rotation digital computer (CORDIC) algorithm.
4. The circuit of claim 3 wherein the oscillator further comprises a scaling multiplier having an input coupled to the f IF and an output coupled to each shift register in parallel, wherein the scaling multiplier scales f IF by a factor of 2 N /f s , and wherein N is a number of bits stored in one shift register and f s is the sampling frequency.
5. The circuit of claim 4 wherein the oscillator further comprises a feedback loop, said feedback loop comprising a plurality of register adders each having an output coupled to the input of a shift register, an input coupled to an output of the scaling multiplier, and an input coupled to one of an output of a shift register or an output of a separate register adder.