AWG having arbitrary factor interpolator and fixed frequency DAC sampling clock
View Patent ↗An AWG includes a waveform memory providing a digital waveform signal at a sample rate and an arbitrary factor interpolator (AFI) coupled to receive the digital waveform signal or a processed digital waveform signal. A complex mixer for carrier modulation is coupled to the AFI which outputs a complex band pass signal. A DAC is coupled to an output of the complex mixer for receiving the complex band pass signal to provide an analog output signal. A fixed frequency sample clock clocks the DAC to provide a fixed DAC sample rate. The DAC provides a data clock signal to a sample request controller that generates a sample request signal that is coupled to the waveform memory for requesting the digital waveform signal from the waveform memory. The interpolated digital signal is sampled at the fixed DAC sample rate independent of the sample rate of digital waveform signal.
1. An arbitrary waveform generator (AWG), comprising:
a waveform memory for providing a digital waveform signal at a sample rate;
an arbitrary factor interpolator (AFI) coupled to receive said digital waveform signal or a processed digital waveform signal to provide an interpolated digital signal;
a complex mixer for carrier modulation coupled to said AFI, said complex mixer receiving said interpolated digital signal and outputting a complex band pass signal;
a digital to analog converter (DAC) coupled to an output of said complex mixer for receiving said complex band pass signal to provide an analog output signal;
a fixed frequency sample clock for clocking said DAC to provide a fixed DAC sample rate, wherein said DAC provides a data clock signal, and
a sample request controller for receiving said data clock signal and generating a sample request signal, said sample request signal coupled to said waveform memory, wherein said sample request signal controls times for requesting said digital waveform signal from said waveform memory;
wherein said interpolated digital signal provided by said AFI is sampled at said fixed DAC sample rate independent of said sample rate of said digital waveform signal.
2. The AWG of claim 1 , further comprising a digital pulse shaping filter coupled between an output of said waveform memory and an input of said AFI for generating said processed digital waveform signal comprising a shaped digital signal and providing said shaped digital signal to said AFI.
3. The AWG of claim 1 , wherein said AFI comprises a polynomial based filter (PBF).
4. The AWG of claim 3 , wherein said PBF comprises a Farrow Structure.
5. The AWG of claim 2 , wherein said digital pulse shaping filter comprises a polyphase FIR.
6. The AWG of claim 1 , wherein said AFI is implemented on a FPGA.
7. The AWG of claim 1 , wherein said DAC comprises an interpolating and frequency shifting DAC.
8. The AWG of claim 1 , wherein said sample request controller comprises a μ generator and a series connected overflow detector that generates said sample request signal.
9. The AWG of claim 8 , wherein said overflow detector comprises an overflow accumulator.
10. The AWG of claim 9 , wherein said μ generator is operable to calculate and output a parameter μl that is coupled to said overflow accumulator using the following calculation:
μ
l
+
1
=
μ
l
+
T
DAC
T
in
-
⌊
μ
l
+
T
DAC
T
in
⌋
;
where l is the output sample index, T DAC /T IN is a floor operator and said calculation is performed at the said fixed DAC sample rate.
11. The AWG of claim 1 , further comprising a fixed analog smoothing filter coupled to an output of DAC.
12. A method for signal synthesis, comprising:
receiving a digital waveform signal at a sample rate;
arbitrary factor interpolating said digital waveform signal or a processed digital waveform signal to provide an interpolated digital signal at a first sample rate;
processing said interpolated digital signal to generate a complex band pass signal, and
digital to analog (D/A) converting said complex band pass signal to provide an analog output signal, wherein a single fixed frequency sample clock is used for said D/A converting to provide a fixed DAC sample rate that is equal to said first sample rate.
13. The method of claim 12 , further comprising shaping said digital waveform signal to provide said processed digital waveform signal comprising a shaped digital signal, and coupling shaped digital signal for said arbitrary factor interpolating.
14. The method of claim 12 , further comprising:
generating a data clock signal from said fixed DAC sample rate;
receiving said data clock signal and generating a sample request signal;
coupling said sample request signal to a waveform memory that provides said digital waveform signal, wherein said sample request signal controls times for requesting said digital waveform signal from said waveform memory.
15. The method of claim 12 , further comprising smoothing said analog output signal with a fixed analog filter.
16. The method of claim 12 , wherein said analog output signal comprises a vector modulated signal.
17. The method of claim 16 , wherein said vector modulated signal comprises an I/Q signal.
18. A method of programming a field programmable gate array (FPGA) to provide an arbitrary waveform generator (AWG) by realizing AWG functionality that couples between a waveform memory that provides a digital waveform signal at a sample rate and a digital to analog converter (DAC) having a fixed frequency sample clock for clocking said DAC to provide a fixed DAC sample rate, said realizing AWG functionality comprising:
applying a preconfigured, non-modifiable FPGA netlist to said FPGA to implement said AWG functionality, said AWG functionality comprising:
an arbitrary factor interpolator (AFI) coupled to receive a digital waveform signal or a processed digital waveform signal originating from said waveform memory to provide an interpolated digital signal;
a complex mixer for carrier modulation coupled to said AFI, said complex mixer receiving said interpolated digital signal and outputting a complex band pass signal;
wherein said DAC is coupled to an output of said complex mixer for receiving said complex band pass signal to provide an analog output signal and wherein said DAC provides a data clock signal, and
a sample request controller for receiving said data clock signal and generating a sample request signal, wherein said sample request signal is coupled to said waveform memory, and wherein said sample request signal controls times for requesting said digital waveform signal from said waveform memory;
wherein said interpolated digital signal provided by said AFI is sampled at said fixed DAC sample rate independent of said sample rate of said digital waveform signal.
19. The method of claim 18 , further comprising generating said FPGA netlist, wherein said applying a preconfigured, non-modifiable FPGA netlist comprises using a software package that provides a graphical user interface (GUI) with a plurality of menu of options for customizing said configuring said AWG functionality before said generating said FPGA netlist.
20. An electronic test system for testing a device under test (DUT), comprising:
a work station for controlling said system;
an arbitrary waveform generator (AWG) for providing analog test signals to test said DUT, comprising:
a waveform memory for generating a digital waveform signal at a sample rate;
a digital pulse shaping filter coupled to an output of said waveform memory for shaping said digital waveform signal to provide a shaped digital signal;
an arbitrary factor interpolator (AFI) coupled to said digital pulse shaping filter for receiving said shaped digital signal and providing an interpolated digital signal;
a complex mixer for carrier modulation coupled to said AFI, said complex mixer receiving said interpolated digital signal and outputting a complex band pass signal;
a digital to analog converter (DAC) coupled to an output of said complex mixer for receiving said complex band pass signal to provide said analog test signals;
a fixed frequency sample clock for clocking said DAC to provide a fixed DAC sample rate, wherein said DAC provides a data clock signal, and
a sample request controller for receiving said data clock signal and generating a sample request signal, said sample request signal coupled to said waveform memory, wherein said sample request signal controls times for requesting said digital waveform signal from said waveform memory;
wherein said interpolated digital signal provided by said AFI is sampled at said fixed DAC sample rate independent of said sample rate of said digital waveform signal,
and pin electronics coupled to an output of said AWG for applying signals including said analog test signals to said DUT.