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steps.doc
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1987-01-03
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159 lines
The Phaselock programs are really general purpose feedback ì
control programs. I have included a data file of a -9db/Octave ì
loop filter, normalized to unity gain at 1 rad/sec.
For a sample run, follow the steps below.
1) Engage CAPS LOCK.
2) Type PHASLOK.
3) When the menu appears type A.
4) At the prompt, type OPNLOOP.DAT. These are the frequency ì
variables of a -9db/Octave loop filter normalized to unity gain ì
at 1 rad/sec.
5) When the menu reappears, type C. You will see the system ì
poles and zeroes.
6) Type N to edit prompts.
7) Type E.
8) Type .1# at the loop gain prompt.
9) Type N at the plot prompt.
10) Type .1# at the start frequency prompt.
11) Type 2.0# at the number of decades prompt.
12) Type .1# at the decade increment prompt.
13) A tabulation of the open and closed loop gain and phase ì
will appear. This display is usefull to adjust the loop gain for ì
minimum open loop phase at the unity gain crossover frequency.
14) Make a note of the closed loop ,-3dB frequency. A ì
frequency that gives anything more than -3dB is adequate.
15) Type N to the new gain prompt.
16) When the menu reappears, type F.
17) Type .1# at the loop gain prompt.
18) Type the appropriate -3dB frequency earlier noted.
19) The loop noise bandwidth will appear. This is useful for ì
determining total carrier phase deviation.
20) Type N at the new gain prompt.
21) When the menu reappears, type G.è
22) Type .1# at the loop gain prompt.
23) The transfer function, F(s) will be displayed as the ì
ratio of two polynomials.
24) Press any key.
25) When the main menu reappears, type C.
26) You will now see the closed loop frequency variable. ì
Note that the closed loop zeroes are the same as the open ì
loop zeroes.
27) Type N at the edit prompt.
28) When the menu reappears type H.
29) The impulse response h (t) will be tabulated.
30) Press any key.
31) Type 0 for start time.
32) Type 25 for stop time.
33) When the annotation prompt appears type N.
34) When the line type prompt appears type 1.
34) Type N at the min/max prompts.
36) Type 0 at the screen oplot prompt.
37) The loop impulse response will be displayed.
38) Press any key.
39) When the menu reappears, type C.
40) Type N at the edit zeroes prompt.
41) Type Y at the edit poles prompt.
42) Type A at the edit options prompt.
43) Type 1 at the how many? Prompt.
44) Type 0 for the real part prompt.
Type 0 for the imaginary part prompt.
The frequency variable list now contains the step ì
response spectral function, namely, a pole at the
origin.
è 45) When the menu reappears, type C to inspect the new ì
frequency variable list.
46) Type N at the edit prompt.
47) Type H.
48) The step response, h(t), will be tabulated.
49) Press any key.
50) Type 0 at the start time prompt.
51) Type 25 at the stop time prompt.
52) Type N at the annotation prompt.
53) Type 1 at the line type prompt.
54) Type N at the min/max prompts.
55) Type 0 for the screen plot.
56) The loop step response will be displayed.
This completes a simplified "run through" of the program.
The programs IFTLOOP, and SMPLOOP, are similar in operation, ì
but very different in the transient response algorithm. The ì
first thing you will notice is that the time response takes ì
longer to compute. This is because they compute 1024 open loop ì
gain and phase points, subsequently 1024 closed loop gain and ì
phase points, and then performs a 1024 point inverse Fourier ì
transform.
The step response is the numerical integration of the ì
impulse response.
You will notice there is a zero response delay prior to the ì
beginning of the time response. This delay is generated by a ì
linear phase generator used for normalization purpose.
In using these programs you should always run the impulse ì
response first, making sure it has settled completely to zero at ì
the end of the time base chosen. This ensures the correct ì
calculation of the step response.
SMPLOOP includes the sinc x characteristics of a sampling ì
phase detector, and also includes the excess loop pole generated ì
by non-ideal sampling. HP has an excellent application note on ì
sampling phase detectors.