High bandwidth real-time oscilloscope
View Patent ↗A method and apparatus for digitizing a data signal. An input analog data signal, is received and split into a plurality of split signals. At least one of the split signals is mixed with a predetermined periodic function with a predetermined frequency. The split signals are then digitized and combined mathematically to form a single output data stream that is a substantially correct representation of the original input signal.
1. A method for digitizing a data signal, comprising the steps of:
receiving an input analog data signal spanning a frequency range;
splitting the received input analog data signal into a plurality of split signals, each spanning a frequency range smaller than the original frequency range;
mixing at least one of said split signals with a predetermined periodic function with a predetermined frequency, thereby translating the frequency range of the at least one split signal;
digitizing each of said split signals;
converting the frequency range of the at least one split signal back to its original frequency range; and
combining said digitized split signals mathematically to form a single output data stream that is a substantially correct representation of the received input signal over the original frequency range.
2. The method of claim 1 , wherein the input analog data signal is split by a 50 Ohm splitter.
3. The method of claim 1 , further comprising the step of band limiting each of the split signals to a corresponding one of a plurality of predetermined band ranges before mixing.
4. The method of claim 3 , wherein a frequency of said predetermined periodic function is at a low side of said band of said at least one split signal that is mixed.
5. The method of claim 3 , wherein a frequency of said predetermined periodic function is at a high side of said band of said at least one split signal that is mixed.
6. The method of claim 1 , further comprising the step of passing the mixed split signal through an image reject filter, having a second predetermined frequency.
7. The method of claim 6 , wherein said image reject filter comprises an intrinsic bandwidth of a digitized channel used for digitizing said mixed split signal.
8. The method of claim 1 , wherein said mixing is accomplished by a sampling action of a digitizer used for digitizing said at least one split signal.
9. The method of claim 1 , wherein said predetermined periodic function is a low-distortion sinusoid.
10. A method for digitizing a data signal, comprising the steps of:
receiving an input analog data signal;
splitting the received input analog data signal into channels having a low frequency split signal and a high frequency split signal respectively;
mixing at least one of said low frequency and said high frequency split signals with a predetermined periodic function with a predetermined frequency;
digitizing said split signals;
band limiting each of the split signals to a predetermined band range;
upsampling each digitized split signal to a predetermined sample rate;
mixing said at least one of said low frequency and said high frequency split signals with a predetermined periodic function with said predetermined frequency, resulting in two images of said at least one split signal;
passing said at least one of said high frequency and said low frequency split signals through an image reject filter, having a second predetermined frequency, to remove an unwanted one of the two images; and
combining said digitized split signals mathematically to form a single output data stream that is a substantially correct representation of the received input signal.
11. The method of claim 10 , further comprising the step of passing at least one of said low frequency and high frequency split signals through a band limiting filter.
12. The method of claim 10 , further comprising the step of equalizing the low frequency and the high frequency split signals separately to compensate for non-ideal magnitude and phase characteristics of front-end and digitizing systems for each channel.
13. The method of claim 10 , wherein the input analog data signal is split by a 50 Ohm splitter.
14. The method of claim 10 , wherein said predetermined periodic functions are low-distortion sinusoids.
15. An apparatus for digitizing a data signal, comprising:
an input for receiving an input analog data signal spanning a frequency range;
a splitter for splitting the received input analog data signal into a plurality of split signals, each spanning a frequency range smaller than the original frequency range;
a mixer for mixing at least one of said split signals with a predetermined periodic function with a predetermined frequency, thereby translating the frequency range of the at least one split signal;
a digitizer for digitizing each of said split signals;
a converter for converting the frequency range of the at least one split signal back to its original frequency range; and
a combining unit for combining said digitized split signals mathematically to form a single output data stream that is a substantially correct representation of the original input signal over the original frequency range.
16. The apparatus of claim 15 , wherein said splitter is a 50 Ohm splitter.
17. The apparatus of claim 15 , further comprising a band limiter for band limiting each of the split signals to a corresponding one of a plurality of predetermined band ranges before mixing.
18. The apparatus of claim 17 , wherein a frequency of said predetermined periodic function is at a low side of said band of said at least one split signal that is mixed.
19. The apparatus of claim 17 , wherein a frequency of said periodic predetermined function is at a high side of said band of said at least one split signal that is mixed.
20. The apparatus of claim 15 , further comprising an image reject filter having a second predetermined frequency for receiving and passing the mixed split signal.
21. The apparatus of claim 20 , wherein said image reject filter comprises an intrinsic bandwidth of a digitized channel used for digitizing said mixed split signal.
22. The apparatus of claim 15 , wherein said mixing is accomplished by a sampling action of a digitizer used for digitizing said at least one split signal.
23. The apparatus of claim 15 , wherein said predetermined periodic function is a low-distortion sinusoid.
24. An apparatus for digitizing a data signal, comprising:
an input for receiving an input analog data signal;
a splitter for splitting the received input analog data signal into channels having a low frequency split signal and a high frequency split signal respectively;
a first mixer for mixing at least one of said high frequency and said low frequency split signals with a predetermined periodic function with a predetermined frequency;
a digitizer for digitizing said split signals;
a band limiter for band limiting each of the split signals to a predetermined band range;
an upsampler for upsampling each digitized split signal to a predetermined sample rate;
a second mixer for mixing said at least one of said high frequency and said low frequency split signals with a predetermined periodic function with said predetermined frequency, resulting in two images of said at least one split signal;
an image reject filter, having a second predetermined frequency for receiving and passing said at least one of said high frequency and said low frequency split signals to remove an unwanted one of the two images; and
a combining unit for combining said digitized split signals mathematically to form a single output data stream that is a substantially correct representation of the received input signal.
25. The apparatus of claim 24 , further comprising a band limiting filter for receiving and passing at least one of said high frequency and low frequency split signals.
26. The apparatus of claim 24 , further comprising an equalizer for equalizing the high frequency and the low frequency split signals separately to compensate for non-ideal magnitude and phase characteristics of front-end and digitizing systems for each channel.
27. The apparatus of claim 24 , wherein said splitter is a 50 Ohm splitter.
28. The apparatus of claim 24 , wherein said predetermined periodic functions are low-distortion sinusoids.