Timeline for Phase Locked Loop Gain Design- FM Demodulation
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Jun 11, 2018 at 5:14 | history | edited | Zearia | CC BY-SA 4.0 |
added 629 characters in body
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| Jun 10, 2018 at 21:36 | history | edited | Zearia | CC BY-SA 4.0 |
deleted 765 characters in body
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| Jun 10, 2018 at 20:42 | history | edited | Zearia | CC BY-SA 4.0 |
better explained exact confusion
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| Jun 10, 2018 at 20:29 | comment | added | Zearia | First, tf() generates a continuous-time transfer taking a numerator and denominator as an input. It works predictably with general LPF, HPF, bandpass, etc, transfer functions. My issue is that it seems that unless I can freely control the Kvco constant, I can never achieve unity gain at the desired frequency as the rest of the constants effect both the numerator and denominator. I'm not sure how to set Kvco, as I thought it was an intrinsic part of the VCO which I cannot directly control, and I am not sure how to measure it. Most derivations I find treat it different than the VCO amplitude. | |
| Jun 10, 2018 at 12:16 | comment | added | Andy aka | You just want unity gain for 25 kHz and not 50 kHz and if there is a slight tail-off such as 3 dB then that's fine because when bandwidths are specified there is an assumption of 3 dB reduction at the end points. I don't understand what your problem is really. | |
| Jun 10, 2018 at 9:41 | comment | added | Neil_UK | Have you used tf() before? Does it do what you expect with simpler arguments. Have you plotted the open loop Bode plot yet to see what's going on properly? | |
| Jun 10, 2018 at 9:20 | comment | added | Andy aka | @Zearia - I think you need to take the tour and note the section near the top marked "Ask questions, get answers, no distractions". | |
| Jun 10, 2018 at 7:41 | comment | added | Sven B | @Neil_UK I am fairly sure the author is talking about tf() - I have used it before myself. The transfer function he inputted seems to be: $$H(s) = \frac{A_uK_dA_cA_v\cdot s}{0.5\cdot s + A_uK_dA_cA_vK_{vco}}$$ | |
| Jun 10, 2018 at 6:05 | comment | added | Neil_UK | What does the function tf() do? Is it something you've written, or is it from a Matlab library? What is much more useful at this stage of the process is a Bode plot of the loop gain, that is Loop_Num * Loop_Den, dB against log(frequency), as it gives you the closed loop bandwidth, allows you to see whether it's stable or not, and gives you the fidelity factors for how well it tracks in band and rejects out of band. | |
| Jun 10, 2018 at 2:05 | history | asked | Zearia | CC BY-SA 4.0 |