Questions tagged [linear-phase]

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Time delay vs phase ramp, group delay and phase delay

I need to apply a phase ramp in the frequency domain to a signal in order to apply a delay to it in the time/digital domain. However, I am confused by the fact that if I convert the phase ramp into ...
0 votes
2 answers
55 views

Linear Phase in equiripple filters

How come equiripple filters are symmetric/anti-symmetric in time, but do not posses linear phase, but only piecewise-linearity? Do not all FIR+symmetric/anti-symmetric have Generalized linear phase?
2 votes
1 answer
214 views

Phase response of non-symmetric FIR filters

FIR filters are said to have linear phase when the filter coefficients are symmetric or antisymmetric with respect to time instant n=0. I am trying to design a ...
1 vote
2 answers
86 views

Turning non-symmetric filter into a symmetric filter

I would like to ask if there is a systematic way to turn a non-symmetric filter into a symmetric equivalent with the same frequency response. For example, let's say I have a finite length filter with ...
3 votes
5 answers
497 views

Linear phase with a non-integer delay?

Let's say you are given a frequency domain specification for a filter design. As a simple example, let's use an ideal (brickwall) LPF. Now the impulse response of an ideal LPF is a $\operatorname{sinc}...
0 votes
2 answers
73 views

FFT-Phase variation of a signal

I was studying the phase variation of a signal using sliding window FFT generated using below python code. The phase variation produced for my signal starts from somewhere in middle of the signal ...
0 votes
0 answers
146 views

Derivation of the 4 types of real-valued linear-phase FIR filters

Is there any resource or literature where I can find derivations/proofs for all four linear phase filter types starting from an arbitrary real valued impulse response? I looked at some of the ...
0 votes
1 answer
56 views

Linear phase impulse response causes non linear phase frequency response in GNU Octave/ Matlab

Assume linear phase FIR symteric impulse response like [1 2 3 4 5 5 4 3 2 1],shoud resault in a frequency response with linear phase negative sloped phase. but it ...
0 votes
1 answer
246 views

What is the position of all zeros of a minimum phase, Type 1 Linear Phase FIR Filter?

Let me write down all the facts that I know of. In context of the z plane: Minimum phase system: All zeros and poles of such a system lie inside the unit circle. Linear phase FIR filter: For every ...
13 votes
4 answers
1k views

Minimum Phase - All Pass Decomposition For Large Linear Phase Filters

UPDATE: I am looking for a robust approach to decompose linear phase FIR filters with 100s of coefficients into its minimum phase and all pass components. I originally thought determining all the ...
0 votes
0 answers
93 views

Parallel connected FIR filters type III

I am currently studying dsp and I have a question: Let us assume multiple FIR filters with generalized linear phase of Type III and real IRs $h_1[n], h_2[n], ..., h_k[n],$ interconnected in parallel. ...
0 votes
2 answers
424 views

Why does an FFT-based filter change phase?

I am very new to DSP, and I'm just trying to figure stuff out here. I saw a video which stated that a filter implemented using an FFT would alter the phase of different frequencies differently. The ...
4 votes
2 answers
812 views

Linear phase FIR filter for impulse responses that don't appear symmetric

I would like to clarify some confusion I have about linear phase FIR filters of which do not seem to have symmetric impulse responses. Starting with a simple case, a delay, $ h[n] =\delta(n-n_0) $ ...
8 votes
4 answers
48k views

Group delay of the FIR filter

For an FIR filter, with symmetrical tap values $h[N-1-n]=h[n]$, why is the group delay $\frac{N-1}{2} T$ (where $N$ is the number of taps of the FIR filter and $T$ is the sampling time)? Why is ...
1 vote
0 answers
115 views

Cascading IIR filter with All pass filter (APF) for constant group delay and linear phase over the passband using MATLAB not working?

I've designed an IIR Low pass filter in MATLAB with the following parameters. ...
0 votes
1 answer
269 views

Phase of an FFT after zeropadding

How does zero padding effect phase of an FFT? I thought that symmetric zero padding in the center of an image or signal produces no phase change in the FFT (See Here), but I am getting different ...
1 vote
1 answer
195 views

Slope of phase function

Would appreciate some help understanding if I take the phase function of some transfer function and derivative it in the linear part of it which is around the resonant frequency what does this slope ...
0 votes
0 answers
128 views

Difference between MSK and CPSK

I'm trying to understand the differences between the MSK and CPSK transmission, but I am not understanding some things about it. I understood that they are two signals without discontinuity, but what ...
1 vote
1 answer
557 views

Matlab: How to design digital equivalent for a lowpass Bessel filter (Thiran filter)?

In the process of applying a lowpass Bessel filter to my signal, I realized that besself function does not support the design of digital Bessel filters and the bilinear function can be used to convert ...
2 votes
1 answer
99 views

subquestion 2 : original Q "Difference between MSK and GMSK?"

if we talk about a modulation, we mention a linear and nonlinear modulation. GMSK is nonlinear modulation, but it can be derived from a linear modulation as MSK, PAM and we talk about a linear ...
0 votes
1 answer
62 views

Why can't quantum phase noise in radio astronomy amplifiers just be filtered out after down conversion, instead of down-converting first?

In the related Astronomy SE questions below and their answers, it has become apparent that radio telescope arrays down convert their highest frequency bands before the first stage of amplification. ...
0 votes
2 answers
715 views

Issue Understanding Time Delay of a Digital Filter

I am new to the world of digital filters and am educating myself with the book Introduction to Digital Filters by J.O Smith III,. The author derives the frequency response of a very simplistic filter: ...
1 vote
2 answers
151 views

Frequency Sampling Filters (FSFs) NOT the Frequency Sampling Method

A class of digital filters called Frequency Sampling Filters (FSF) has been mentioned in a side note by Richard Lyons in another related question comparing IIR digital filter design using mapping ...
2 votes
1 answer
135 views

Combination of type I FIR linear-phase systems

Let $h_1[n]$ and $h_2[n]$ be impulse responses of type I FIR linear-phase systems with lengths $M$ and $N$. What can be said about the phase response of the following filters? $h_3[n] = h_1[n] + h_2[...
2 votes
0 answers
118 views

Equivalence between the linear phase of FIR filters and the (anti)symmetry of the coefficients

According to the Matt L.'s answer to this question, real-valued and causal FIR filters have a (generalized) linear phase response if and only if their coefficients satisfy (anti)symmetry condition. ...
9 votes
3 answers
4k views

Why do linear phase filters have symmetric impulse responses?

It was given as a fact that linear phase filters have symmetric impulse responses, but I don't see why that has to be true. Can somebody please explain or prove this?
0 votes
1 answer
118 views

Arbitrary phase FIR filter design

I would like to design an FIR filter using the frequency sampling method with nonlinear phase specifications. For example, between $0$ and $\frac{f_s}{4}$ a phase of $180^\circ$ and between $\frac{f_s}...
0 votes
2 answers
284 views

How do I show an impulse response leads to a zero-phase frequency response?

I'm trying to understand how to show that with real coefficients, the phase response of a filter is 0. Here is the impulse response $h[n] = b_1d[n+1] + b_0d[n] + b_1d[n-1]$ How should I approach ...
1 vote
1 answer
729 views

FMCW radar: Linear phase change determination with sinusoidal decomposition

I am struggling to understand how linear phase shift can be determined with a transform whose main purpose is to determine frequencies rather than rate of change of a function. In FMCW radar, ...
0 votes
1 answer
185 views

Design FIR with linear phase response

What is the best way to design a FIR filter with a given linear phase response, such that each frequency inside the passband is phase shifted according to: $$H(f)=e^{i2\pi f k}$$ where $k$ is factor ...
0 votes
1 answer
821 views

Determine group delay from the frequency response of FIR filter

I have a issue to find out, is there any way that one can determine a group delay from frequency response of the FIR filter. Let's say I have I type FIR filter with order of 51. Frequency response ...
1 vote
1 answer
487 views

What is the significance of the linear phase in the phase response of an M-point moving average filter?

I have plotted the magnitude and the phase responses of an M-point moving average filter, the following are the plots when M = 10: We can observe that corresponding to every lobe in the magnitude ...
6 votes
3 answers
1k views

Delay a signal in time vs in frequency

I have a signal h that I want to delay for a time t. I know that I could use two possible approaches: $h_{\text{delay}}[k] = \...
2 votes
1 answer
897 views

What is the reason behind complex conjugate pairs in Linear Phase FIR filter analysis from the Pole Zero plot

When we say that a Generalized Linear Phase System must satisfy the pole zero plot with the condition that a complex zero not on the unit circle exist's in a pair of 4. Then I understand that I need ...
0 votes
3 answers
408 views

Does converting an FIR filter from causal to non-causal remove phase delay?

Let's say I have a causal 3-tap FIR filter: $$y[n] = ax[n] + bx[n-1] + cx[n-2]$$ Assuming I have access to all the data prior to filtering and generate a similar non-causal filter: $$y[n] = ax[n+1] + ...
1 vote
1 answer
641 views

Resampling FIR coefficients

I have received from a client a 32-coefficient FIR filter running at 1 kHz. I would like to adapt the filter to a 24-coefficient FIR filter running at 750 Hz while preserving the 0-375 Hz frequency ...
1 vote
1 answer
86 views

What is the phase response of SRRC/NRZ/RZ pulse shapping filters and does it matter?

So I would like to know if filters usually used for pulse shaping (like SRRC) have a linear phase response, and if not, what this response looks like and does it matters in any circumstances?
5 votes
1 answer
1k views

Why can't realisable IIR filters have linear phase?

I am studying IIR Filter Design and came across this arbitrary statement in my textbook which says that 'physically realisable and stable IIR filters can not have linear phase'. Would really ...
2 votes
1 answer
736 views

How should we read FIR filter phase response graph?

What should we see from the FIR phase response graph, as an example for a linear phase? And what does this straight line at $0.5\pi$ mean?
3 votes
1 answer
428 views

Applications for the Maximum Phase Filter

A maximum phase digital filter has all zeros outside the unit circle, and has the maximum phase and therefore longest delay for a given magnitude response. Besides the possibility of needing a ...
0 votes
1 answer
102 views

Constraints for Type 3 Linear Phase Filter

This might be a strange question - but most of the Type 3 LPF I'm seeing are having this in common for $h[n]$, assuming $h[n]$ is real: We cannot have outermost element of h[n] lower than middle ...
1 vote
2 answers
1k views

How to properly smooth the phase of a spectrum (or any unit-complex function)

I want to smooth the phase of a measured (transfer) spectrum without destroying unit-complexity of the phase factor. Suppose $$f:\mathbb{R}\to \mathbb{C}\qquad , \qquad f(\omega)=r(\omega)\cdot {\rm e}...
7 votes
4 answers
2k views

Examples where non-linear phase filters are used

I stumbled apon this old question: Why is a linear phase important? There the explanation of why linear-phase processing (filtering) is important is very clear. Also the effects on waveforms due to ...
0 votes
2 answers
1k views

How does one make a Zero Latency, Linear Phase, or Natural Phase filter?

Looking at FabFilter's ProQ3 plug-in, they have an option at the bottom of the window to switch between Zero Latency and Linear Phase modes (and I think a Natural Phase option too). I'm familiar with ...
15 votes
4 answers
21k views

could anybody explains me why IIR filters do not have linear phase?

Please tell me. Also I dont know why phase is linear with FIR filters. I would like quantitative analysis. And why linear phase is not achieved by IIR filters ?
0 votes
1 answer
706 views

Is this phase response linear phase?

Would the following frequency response be considered linear phase? I know that linear phase is when the phase response is a linear function of frequency. However, the phase response is only linear ...
0 votes
1 answer
596 views

FIR Linear Phase Condition

This is the linear phase condition for FIR filters as expressed by my prof: I don't understand why $G(f)$ can be negative. Isn't the Fourier transform expressed in polar form ? So the magnitude is ...
0 votes
2 answers
2k views

linear phase and generalised linear phase filters

I know that for linear phase filters, all frequency components have equal delay times. That is, there is no distortion of signal due to the time delay of frequencies relative to one another. However,...
5 votes
1 answer
455 views

Group Delay for Hilbert Transformer and Resulting Dispersion

An ideal Hilbert Transformer shifts the phase for all positive frequencies by $-\pi/2$ and all negative frequencies by $+\pi/2$ while maintaining constant magnitude everywhere. Group Delay is the ...
0 votes
1 answer
1k views

How to Determine if FIR has a Linear_Phase Response w/o Matlab

Given the FIR transfer function: h(z) = $ .36 + .384z^{-1} + .1608z^{-2} +.9712z^{-3} + .352z^{-4} + .18z^{-5} - .2z^{-6} $ How do you determine if this transfer function has a linear - phase ...