Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [nyquist-plot]

For questions about Nyquist plots, often used to assess the stability of an electrical circuit which includes feedback. Consider also using the "frequency-response" tag, and "stability" tag if your question is about the stability of an electrical circuit.

A type of plot of the frequency response of an electrical circuit, often used to assess the stability of an electrical circuit which includes feedback.

52 questions
16
votes
5 answers

Is the book wrong about the Nyquist Sampling Criterion?

Is the following statement from a book wrong? I thought sampling with twice the signal's highest frequency component would be adequate to completely recover the signal. But above it says sampling twice creates a saw-tooth like wave. Is the book…
user1245
  • 3,955
  • 4
  • 37
  • 87
15
votes
9 answers

When is it required or permitted to sample below Nyquist rate

I have searched past questions and answers on this platform but none answers this question. A prof said it is possible to sample below Nyquist rate under certain conditions. I will like to know, first, if it is possible to do this, if so, when?
Mikky Mikky
  • 151
  • 1
  • 3
5
votes
1 answer

What would a polar plot or a Nyquist plot of an undamped second order system look like?

I'm relatively new to control systems. I got to know how critically damped system looks like in Nyquist plot (same gain and phase cross over frequencies. PS. correct me if I'm wrong) and Bode plot thanks to the Octave online simulator, but I'm…
yogesh
  • 53
  • 5
4
votes
2 answers

Why isn't Nyquist taught like this?

When I learnt how to do a Nyquist plot I was taught a really long-winded method that I don't understand to this day. I realised by myself that if you are given a system like below where \$s=j\omega\$ $$\frac{s+1}{s+10}$$ you can just replace \$s\$…
CoderEH
  • 143
  • 5
4
votes
3 answers

Sampling rate understanding for ADC requirement

So I have this voltage plot. These are voltages corresponding to a current changes on a wire. I am trying to understand the rate of transmission for choosing a ADC to read these analog values. The peak to peak time is 3-4us. I need to sample them…
Newbee
  • 41
  • 1
  • 5
4
votes
4 answers

Is the Nyquist plot useful in actual electrical engineering?

I am currently doing a course on linear control theory, and we are covering Nyquist Plot to study phase and gain margin. I find myself unable to appreciate this concept. One, the proof of the Nyquist criterion is very non-intuitive to me, something…
Coco Jambo
  • 141
  • 2
4
votes
2 answers

How to plot Nyquist plots?

By using the open loop transfer function for a control system, how would you then sketch the Nyquist plot by hand? I'm aware you'd substitute any \$s\$ term for \$j\omega\$ and then rationalise the denominator by moving the \$j\$ terms to the…
jackthompson
  • 41
  • 1
  • 5
3
votes
2 answers

Recording aliased tones on purpose

For research purposes, I am trying to transmit a tone and record it using sub-Nyquist sampling. Via the PC microphone, for instance, I would expect to see the aliasing effect somewhere in the spectrum plot, but no matter what I try it is absent. I…
Dannynis
  • 31
  • 3
3
votes
2 answers

Why is this system stable?

I was given the system defined by the open-loop transfer function: \$L(s)=\frac{5(s^2+1.4s+1)}{(s-1)^2}\$ I was told to use the Nyquist criterion to determine stability. Examining the Nyquist plot shows one CCW encirclement of the (-1,0) point. The…
j15
  • 39
  • 3
2
votes
2 answers

How to draw a Nyquist plot by hand using standard plotting strategies?

I want to draw by hand the Nyquist plot of an RC filter's transfer function. I do not want to use the "tricks" that help with building it faster (evaluating just some limits points) - I want to draw it using the usual plotting strategies. …
fjohn
  • 67
  • 6
2
votes
2 answers

Nyquist theory - Control system - Stability

I am trying to understand the Nyquist theory for knowing if a system is stable. Here is what I know : A system is unstable when the open loop transfer function + 1 of the system has one or more right half plane zeroes in the s-plane. The Nyquist…
Jess
  • 2,694
  • 1
  • 18
  • 46
2
votes
1 answer

According to the Nyquist criterion this system is stable but when I apply an impulse I get an unstable response, why?

I have this open loop transfer function and I have to study the stability of the closed loop transfer function using the Nyquist criterion. What I got is that the characteristic equation 1+GH(s)=0 has two roots inside the Nyquist contour, the GH(s)…
Pedro
  • 197
  • 2
  • 13
2
votes
3 answers

What are the connection between bandwidth, Nyquist criteria and quantization?

I am trying to solve the below problem and I was not able to find the relation between bandwidth, Nyquist criteria and quantization. Can you please provide some hint? Imagine that the possible transmissible symbols are 64. Whenever the transmitter…
The Voyager
  • 121
  • 2
1
vote
2 answers

Deriving a transfer function from Nyquist plot

I am given a half Nyquist plot and exercise as below I know how to plot a Nyquist curve for a given transfer function but I have trouble doing it the other way. I stumbled upon this post Deriving transfer function from nyquist plot and it seems…
insertRandomName
  • 11
  • 3
1
vote
1 answer

Instability as seen in time domain

It is my understanding that an unstable closed loop in a minimum-phase system occurs when the loop gain (A*B of the characteristic equation) encircles the -1 point on the Nyquist chart. In…
Hyp
  • 671
  • 2
  • 13
1
2 3 4