Spectral stitching method to increase instantaneous bandwidth in vector signal analyzers

Patent metadata

Field	Value
Publication number	US-9548882-B2
Application number	US-201615072909-A
Country	US
Kind code	B2
Filing date	Mar 17, 2016
Priority date	Oct 15, 2014
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

Various embodiments are described of devices and associated methods for processing a signal using a plurality of vector signal analyzers (VSAs). An input signal may be split and provided to a plurality of VSAs, each of which may process a respective frequency band of the signal, where the respective frequency bands have regions of overlap. Each VSA may adjust the gain and phase of its respective signal such that continuity of phase and magnitude is preserved through the regions of overlap. The correction of gain and phase may be accomplished by a complex multiply with a complex calibration constant. A complex calibration constant may be determined for each VSA by comparing the gain and phase of one or more calibration tones generated with each region of overlap, as measured by each of the VSAs.

First claim

We claim:

1. A method for processing a received signal, the method comprising:
digitizing each of a plurality of component signals, each component signal comprising a respective frequency band of the received signal;
frequency-shifting the component signals such that the respective frequency band of each component signal has a respective region of overlap with the frequency band of at least one other of the component signals;
filtering the component signals, by a digital filter, after said digitizing and before said frequency-shifting, such that the sum of the component signals has a unity frequency response within the regions of overlap;
adjusting the gain and phase of the component signals such that the sum of the component signals has a continuous frequency response over an aggregate frequency band comprising each of the frequency-shifted frequency bands; and
summing the component signals to obtain a composite signal;
wherein said digitizing, frequency-shifting, filtering, and adjusting the gain and phase are performed for each component signal by a respective phase-locked, time-synchronized vector signal analyzer.

2. The method of claim 1 , wherein said digitizing comprises, for each component signal, sampling at least a portion of the component signal corresponding to the respective frequency band.

3. The method of claim 1 , wherein said digitizing comprises, for each component signal, shifting a center frequency of the respective frequency band to baseband; and
wherein said frequency-shifting comprises, for each component signal, frequency-shifting the component signal by a difference between the original center frequency of the respective frequency band and a center frequency of the received signal.

4. The method of claim 1 , further comprising interpolating the component signals after said digitizing and before said frequency-shifting.

5. The method of claim 1 , wherein the digital filter is a half-band filter.

6. The method of claim 1 , further comprising, at each of the vector signal analyzers, correcting a sampling delay of the respective component signal.

7. An apparatus for processing a signal, the apparatus comprising:
a signal splitter configured to receive an analog signal, and output a plurality of copies of the analog signal;
a plurality of parallel signal processing pathways, each of the parallel signal processing pathways configured to receive from the signal splitter a respective copy of the analog signal, and to process a respective component signal of the analog signal, each component signal comprising a respective frequency band of the analog signal, wherein, in processing the respective component signal, each of the parallel signal processing pathways is configured to:
digitize the respective component signal;
interpolate the respective component signal;
frequency-shift the respective component signal, after said interpolating, such that the respective frequency band has a region of overlap with the frequency band of at least one other of the component signals;
adjust the gain and phase of the respective component signal such that a sum of the component signals has a continuous frequency response over an aggregate frequency band comprising each of the frequency-shifted frequency bands;

a summing unit configured to sum outputs of the plurality of parallel signal processing pathways to obtain a composite signal.

8. The apparatus of claim 7 , wherein each of the parallel signal processing pathways is further configured to:
filter the respective digital signal such that the sum of the component signals has a unity frequency response within each region of overlap.

9. The apparatus of claim 8 , wherein said filtering is performed by a digital filter before said frequency-shifting.

10. The apparatus of claim 9 , wherein the digital filter is a half-band filter.

11. The apparatus of claim 7 , wherein said digitizing the respective component signal comprises shifting a center frequency of the respective frequency band to baseband; and wherein said frequency-shifting the respective component signal comprises frequency-shifting the respective component signal by a difference between the original center frequency of the respective frequency band and a center frequency of the analog signal.

12. An apparatus for processing a signal, the apparatus comprising:
a first signal processing pathway configured to:
receive a first component signal comprising a first frequency band of an input signal; and
digitize the first component signal;

a second signal processing pathway, phase-locked and time-synchronized with respect to the first signal processing pathway, the second signal processing pathway configured to:
receive a second component signal comprising a second frequency band of the input signal, the second frequency band having a region of overlap with the first frequency band; and
digitize the second component signal;
wherein, when the second signal processing pathway is in a calibration mode, the second signal processing pathway is further configured to compute a calibration constant useable to correct phase mismatch between the first signal processing pathway and the second signal processing pathway, wherein the calibration constant is computed based on a phase difference between a first digitized version of a calibration tone output by the first signal processing pathway and a second digitized version of the calibration tone output by the second signal processing pathway, wherein the calibration tone is included in the input signal within the region of overlap between the first frequency band and the second frequency band; and

a memory configured to store the calibration constant.

13. The apparatus of claim 12 , wherein, when the second signal processing pathway is not in the calibration mode, the second signal processing pathway is further configured to:
correct phase mismatch between a digitized output of the first signal processing pathway and a digitized output of the second signal processing pathway, using the stored calibration constant.

14. The apparatus of claim 12 , wherein the calibration constant is further useable to correct gain mismatch between the first signal processing pathway and the second signal processing pathway, wherein the calibration constant is computed further based on a ratio of a magnitude of the first digitized version of the calibration tone and a magnitude of the second digitized version of the calibration tone.

15. The apparatus of claim 12 , wherein the first signal processing pathway is further configured to:
filter the first component signal; and
wherein the second signal processing pathway is further configured to:
filter the second component signal;
wherein said filtering of the first and second component signals is configured to cause a sum of the first and second component signals to have a unity frequency response within the region of overlap.

16. The apparatus of claim 15 , wherein said filtering is performed by one or more half-band filters.

17. The apparatus of claim 12 , wherein said digitizing the first component signal comprises shifting the first component signal such that the first frequency band is at baseband, and said digitizing the second component signal comprises shifting the component signal such that the second frequency band is at baseband;
wherein the first signal processing pathway is further configured to:
frequency-shift the digitized first component signal such that the calibration tone occurs at a particular frequency;
wherein the second signal processing pathway

Assignees

• Nat Instr Corp

Inventors

• Dark Stephen L
• Baker Daniel J
• Ammerman Johnathan R W

Classifications

• H04B17/21

  for calibration; for correcting measurements · CPC title

• H04B17/309 Primary

  Measuring or estimating channel quality parameters · CPC title

• H04B17/0085

  using test signal generators · CPC title

• H04B1/12

  Neutralising, balancing, or compensation arrangements · CPC title

• H04W72/044

  based on the type of the allocated resource · CPC title