| 1 | command SPECTRUM <trc-list> <n> [<lo-t> <hi-t>] <lo-f> <hi-f> <f-steps> |
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| 2 | ================ |
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| 3 | |
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| 4 | key: MEM power spectrum |
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| 5 | |
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| 6 | Computes power spectrum of traces given by <trc-list>. <n> specifies |
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| 7 | the number of poles used for the approximation. <lo-t>,<hi-t> |
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| 8 | selects a time window on the input traces. If omitted the trace |
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| 9 | window on the current display is used. <lo-f>,<hi-f> specifies |
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| 10 | the frequency range (in Hz) for the resulting output traces. |
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| 11 | <f-steps> is the number of samples on the output traces. For the |
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| 12 | output trace the horizontal axis gives the frequency in Hz, unless |
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| 13 | the "/log" qualifier is specified. |
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| 14 | |
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| 15 | |
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| 16 | parameters |
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| 17 | ---------- |
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| 18 | |
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| 19 | <trc-list> --- parameter type: trace list |
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| 20 | List of traces to compute power spectrum. |
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| 21 | |
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| 22 | <n> --- parameter type: integer |
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| 23 | Number of poles (order of approximation). |
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| 24 | |
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| 25 | <lo-t>, <hi-t> --- parameter type: real |
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| 26 | Time window on input traces. If not specified the current |
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| 27 | display window is used. If <lo-t> is an astrisk ("*") |
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| 28 | you can select the window by graphic cursor. |
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| 29 | |
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| 30 | <lo-f>, <hi-f> --- parameter type: real |
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| 31 | Frequency range to compute the output traces (in Hz). |
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| 32 | |
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| 33 | <f-steps> --- parameter type: integer |
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| 34 | Number of samples on output traces. The output traces range |
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| 35 | from <lo-f> Hz to <hi-f> Hz using <f-steps> equidistant |
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| 36 | sample values. |
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| 37 | |
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| 38 | |
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| 39 | qualifiers |
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| 40 | ---------- |
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| 41 | |
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| 42 | /log |
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| 43 | The spectrum is computed in logarithmic steps. Be sure that |
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| 44 | in this case <lo-t> is not zero. For the output trace the |
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| 45 | horizontal axis gives the logarithm of the frequency (in Hz). |
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| 46 | |
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| 47 | |
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| 48 | examples |
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| 49 | -------- |
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| 50 | |
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| 51 | spectrum all 50 0. 50. .05 3. 200 |
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| 52 | ! computes power spectrum of all traces on display in the |
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| 53 | ! time window between 0 and 50 seconds. The output traces |
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| 54 | ! range from .05 Hz (20 sec) to 3 Hz using 200 samples. |
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| 55 | |
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| 56 | spectrum 1 30 *;; .1 4. 300 |
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| 57 | ! computes power spectrum of first trace on display from |
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| 58 | ! 10 sec to 4 Hz using 300 samples. The time window on the |
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| 59 | ! input trace must be selected by graphic cursor. |
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| 60 | |
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| 61 | spectrum/log 1 30 *;; .1 100. 300 |
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| 62 | ! Similar to above command except the frequency window and |
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| 63 | ! the logarithmic frequency steps. |
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| 64 | |
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