The present application claims priority to PCT Application No. PCT/EP2007/003453, filed on Apr. 19, 2007, and to German Patent Application No. 10 2006 021 075.1, filed on May 5, 2006, the entire contents of which are herein incorporated by reference.
1. Field of the Invention
The invention relates to a method and a device for digital triggering of a recording of a reference signal having a superimposed noise signal.
2. Discussion of the Background
A phase-corrected and time-corrected presentation of a measurement signal on a recording device, such as a digital oscilloscope, requires a triggering, which identifies the signal portion of the measurement signal to be presented on the recording device, for example, via a threshold triggering value, and initiates the recording of the measurement signal on the recording device at the triggering time via a triggering signal derived from the latter.
If a noise signal, which corresponds to a mean-free, white noise with the variance σn2 is superimposed on the measurement signal, there is no fixed triggering time ttrigger as in the case of a noise-free measurement signal, but rather, as shown in
Starting from
If a noise signal n with the variance σn2 is superimposed on the measurement signal, starting from the triggering equation (3) with a triggering threshold value ur of ½ and an edge steepness m of the measurement signal, a jittering triggering time ttrigger is obtained according to equation (4) with a mean value of and a variance
and a variance σt2 according to equation (5).
It is evident from equation (5) that the variance σt2 in the jitter of the triggering time for a measurement signal with a superimposed noise signal increases with an increasingly flatter leading edge m of the measurement signal. While the variance σt2 in the jitter of the triggering time in the case of a high-frequency measurement signal with a high edge steepness m according to
It is evident from Table 1 in
Document DE 34 18 500 A1 describes a device and a method, in which the disadvantage of jitter in the triggering time and the associated triggering inaccuracy resulting from a noise superimposed on the measurement signal is overcome by converting the level triggering into a time triggering proportional to the latter so that an appropriate threshold value for the time triggering can be set dependent upon the bandwidth of the measurement signal and the bandwidth of the noise signal.
The disadvantage of a realization of this kind is the comparatively high cost in circuit technology (detection of the zero crossing, generation of the sweep voltage, initialization of the sweep voltage and detection of the set-value pass).
The object of the present invention is therefore to develop a method and a device for a digital triggering, with which the triggering inaccuracy in the case of a measurement signal having a superimposed noise signal, especially a low-frequency measurement signal, is minimized at low-cost.
According to the invention, a low-pass filter, which reduces the bandwidth of the measurement signal having a superimposed noise signal, is connected upstream of the digital triggering. This reduces the variance σn2 of the noise signal, which leads to a minimization of the triggering error.
The method according to the invention and the device according to the invention for digital triggering of a recording of a measurement signal having a superimposed noise signal is described in detail below with reference to the drawings. The drawings are as follows:
The device according to the invention for digital triggering is presented in
The analog measurement signal with superimposed noise is converted in an analog/digital converter 1 into its corresponding digital data format. The digitized measurement signal distorted in a linear or respectively non-linear manner is equalized in a subsequent filter-type equalizer 2.
The signal at the output of the filter-type equalizer 2 is compressed in a decimation unit 3 by re-routing to the recording unit 4 only every n-th sampled value of the signal at the output of the filter-type equalizer 2. In parallel with this, the signal at the output of the filter-type equalizer 2 is supplied to a low-pass filter 5. In particular, the relatively high-frequency noise signal by comparison with the measurement signal is band-limited according to the invention in the low-pass filter 5. In this manner, the variance σn2 of the noise signal is reduced. In a digital triggering unit 6 downstream of the low-pass filter 5, the band-limited measurement signal with superimposed noise signal is compared with adjustable threshold values in order to generate a triggering signal.
The digital triggering signal is supplied to a recording-control unit 7 within the recording unit 4. In the recording-control unit 7, the decimated sampled values of the measurement signal with superimposed noise signal buffered in a cyclical manner in a ring buffer 10, are selected for the recording with regard to the triggering signal. The sampled values of the measurement signal with superimposed noise signal selected by the recording-control unit 7 are stored in a subsequent acquisition memory 8 of the recording unit 4 and then presented on a visualization unit 9, for example, a display of the recording unit 4. Finally, in the concluding procedural stage S60, the recording of the compressed, equalized, digitized measurement signal with superimposed noise signal is implemented dependent upon the digital triggering signal. For this purpose, the measurement signal with superimposed noise signal, which is buffered, for example, in a ring buffer, is selected dependent upon the triggering signal with regard to its digitized signal components to be stored in a subsequent acquisition memory 8 and displayed on a subsequent visualization unit 9.
While the table in
The method for digital triggering according to the invention is illustrated in
In a first procedural stage S10, the analog measurement signal with superimposed noise signal is converted in an analog/digital converter 1 into its corresponding digital data format.
In the next procedural stage S20, an equalization of the digitized measurement signal, which may be distorted in a linear or respectively non-linear manner with a superimposed noise signal, is implemented.
In the subsequent procedural stage S30, the digitized, equalized measurement signal with superimposed noise signal is filtered in a low-pass filter.
In procedural stage S40 the triggering signal is generated by threshold-value comparison of the low-pass-filtered, equalized, digitized measurement signal having the superimposed noise signal with reference to a threshold value predetermined in a digital triggering unit.
The equalized, digitized measurement signal with superimposed noise signal is compressed in the next procedural stage S50 in a decimation unit by processing further only every n-th sampled value of the equalized, digitized measurement signal with superimposed noise signal.
Finally, in the concluding procedural stage S60, the recording of the compressed, equalized, digitized measurement signal with superimposed noise signal is implemented dependent upon the digital triggering signal. For this purpose, the measurement signal with superimposed noise signal, which is buffered, for example, in the ring buffer 10, is selected dependent upon the triggering signal with regard to its digitized signal components to be stored in a subsequent acquisition memory 8 and displayed on a subsequent visualization unit 9.
The invention is not restricted to the exemplary embodiment presented. In particular, instead of a low-pass filtering, a band-pass filtering with the effect of reducing the bandwidth of the measurement signal having a superimposed noise signal can also be used.
Number | Date | Country | Kind |
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10 2006 021 075 | May 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/003453 | 4/19/2007 | WO | 00 | 10/15/2009 |
Publishing Document | Publishing Date | Country | Kind |
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WO2007/128392 | 11/15/2007 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3704416 | Elliott et al. | Nov 1972 | A |
4209843 | Hyatt | Jun 1980 | A |
4553221 | Hyatt | Nov 1985 | A |
5053983 | Hyatt | Oct 1991 | A |
5272439 | Mashikian et al. | Dec 1993 | A |
20030128021 | Tan et al. | Jul 2003 | A1 |
20060074607 | Weller | Apr 2006 | A1 |
Number | Date | Country |
---|---|---|
3418500 | Nov 1985 | DE |
693 33 936 | Jun 2006 | DE |
07 234250 | Sep 1995 | JP |
7234250 | Sep 1995 | JP |
WO 2007128392 | Nov 2007 | WO |
Entry |
---|
JP 07-234250A—1995, JPO Machine Translation, including drawings, p. 1-5. |
Lehmann, DE 3418500A1, PTO Translation (PTO 11-6240), without drawings, p. 1-20. |
Anonymous, Application Note: HFAN-3.3.0, Jitter Specifications Made Easy, website, Feb. 6, 2001, pp. 1-6, XP-002461833, URL: http://pdfserv.maxim-ic.com/en/an/AN377.pdf. |
Roger L. Jungerman and Parmijit Samra, Switched-radar scenario generation with Femtosecond jitter, website, Aug. 1, 2005, pp. 18-22, XP-002461834, URL: http://rfdesign.com/mag/508RFDSF2.pdf. |
Eric Desrochers, Lowpass filter discriminates step input from noise, website, Sep. 18, 2003, pp. 92 and 96, URL: http://www.edn.com/contents/images/91803di.pdf. |
“Switched-radar scenario generation with Femtosecond jitter,” DefenseElectronics, Aug. 2005, pp. 1-5. |
“Jitter Specifications Made Easy: A Heuristic Discussion of Fibre Channel and Gigabit Ethernet Methods,” Maxim Integrated Projects, Feb. 6, 2001, pp. 1-6. |
Eric Desrochers, “Lowpass filter discriminates step input from noise,” Internet webpage (http://www.edn.com/index.asp?layout=articlePrint&articleID=CA321803), Sep. 18, 2003, pp. 1-2. |
International Search Report, PCT/EP2007/003453, Jan. 22, 2009, pp. 1-13. |
Number | Date | Country | |
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20100045260 A1 | Feb 2010 | US |