# Questions tagged [feedback]

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### Connection between positive feedback at DC and real-axis right-half-plane pole(s)

(Context provided here, question summarized at the end.) Suppose I have an open-loop transfer function with two coincident left half plane poles like $$H(j\omega)=\frac{-H_0}{(1+j\omega RC)^2}$$ ...
1 vote
83 views

### Zero crossing count vs zero crossing rate: does it make any difference?

I am trying to make a feedback howling detection program for an audio DSP chip I made a very crude one by counting zero crossings, doing something like this: ...
4k views

### What is the Reference in Control Theory?

I've started studying Control and I've come across some concepts that I'm finding a bit difficult to understand. For example, in the system showed here, there is a signal called "reference" as well ...
29 views

### How to accomodate feedback bits from Base Station to devices in LTE or 5g?

I am trying to think of a way in which the base station (BS) can send say 100 bits of feedback to devices in my cell. My confusion is what is a good way to send this feedback bits. This is during the ...
214 views

### How do I reduce a block diagram with just a line as a feedback loop, I dont get how it adds K to the denominator

How do I reduce a block diagram with just a line as a feedback loop, I dont get how it adds K to the denominator. The bottom equation is supposed to be the answer.
81 views

### What does the frequency of oscillating microphone feedback depend on?

Pointing a microphone to a connected loudspeaker creates a feedback path and usually results in acoustic resonance, which manifests in a sustained oscillation: https://youtu.be/_XTtjZ8aZbc. A similar ...
1 vote
74 views

### Feedback stabilizes unstable systems?

Can feedback stabilize a unstable system?I guess so since we may get rid of any poles in the positive complex plane by feedback but I am not sure.
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### To create feedback, does the peak to peak amplitude of a signal loop have to have an amplification factor (gain) that reaches zero?

In technical terms, feedback occurs when the gain in the signal loop reaches "unity" (0dB gain). How to Eliminate Feedback Peak-to-peak amplitude (abbreviated p–p) is the change between ...
243 views

### Getting a single feedback peak from a basic 4 stages phaser

I try to set a very basic 4 stages phaser (two 2-pole all-pass filters), with a particular feedback path where only one peak is raised at center frequency when the feedback is above 0. The following ...
230 views

### Introducing Feedback to Miller Puckette's Time-Domain Pitch Shifting Algorithm without Discontinuities

I've implemented Miller Puckette's time-domain pitch shifting algorithm (http://msp.ucsd.edu/techniques/v0.11/book-html/node125.html) in PureData's help files in C++ (my code here: https://github.com/...
1 vote
52 views

### Did Dialup Modem use closed or open loop power/volume control? How did they determine Tx level?

I have been reading about dialup modems, but one thing I cannot seem to find out about is how implementers determined optimal transmit power/volume. Is this part of the echo cancelation framework? The ...
1 vote
238 views

### How can you see from the transfer function of a system that it has feed forward/feedback elements?

Furthermore, how can you see from the pole/zero plot if the system has feed forward/feedback elements?
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### Is there an existing feedback elimination algorithm that can be implemented in iOS?

The project I'm working on allows a user to speak through a PA system with their iphone as the microphone. Unfortunately, the existing audio units in iOS don't eliminate the feedback between the PA ...
1k views

### Phase Locked Loop Basics

I am trying to better understand discrete-time PLLs. I drew a picture of a simple feedback system here: I want to be able to describe and understand the system at v(t) and y(t). I found a fairly good ...
232 views

### Frequency range of acoustic feedback

What is the frequency range in which acoustic feedback can be found? Most importantly, is there some lowest frequency below which one can expect not to find any feedback? My conclusion from the ...
1 vote
242 views

### Resample with unknown rate change

I am doing digital signal processing for a software defined radio. I have a signal coming in packets of data (several samples) at an average sample rate of approximately some known value FSin. I am ...
1 vote
2k views

### Allpass filter feedforward/feedback design and code

I want to design/implement a simple feedforward/feedback all-pass filter, and I am having some troubles and questions with it. From Shroeder design (based on J. Smith article here): I came up ...
215 views

### Digital implementation of type I compensation network

I'm looking for advice or references on how to implement a "type I" compensation network of digitally. An analog example is shown in the following diagram: I am familiar with the basics of digital ...