# Tag Info

Accepted

### What is zero-phase filtering and forward-backward filtering?

Zero-phase filtering is a non-causal procedure, so it cannot be done in real time, only offline for IIR filters or pseudo real-time, i.e., with a sufficient delay for FIR filters. A zero-phase filter ...
• 90.3k
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### Does Higher Sampling Rate Increase SNR?

Sampling at a higher rate will distribute the quantization noise over a wider frequency, thus reducing the noise spectral density due to quantization noise specifically, with a lot of caveats. For ...
• 51.9k

### Amplifier Placement in a Wireless Receiver

Placing the amplifier first will result in a lower noise figure for the receiver and hence more sensitivity but the amplifier will be exposed to all of the ingested signals, including undesired ...
• 1,175

### Simple software low pass filter

A first order lowpass filter is usually implemented like this: $$p[n] = \alpha p[n-1] + (1-\alpha) pi[n]$$ Where $p[n]$ is your filtered power estimation, $p[n-1]$ is the previous result, $pi[n]$ is ...
• 5,026
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### Interpolating/Decimating CIC Filter Group Delay

Consider an $D$-tap FIR filter with liner phase, the group delay (measured in samples) is $$g=\frac{D-1}{2}\tag{1}$$ and therefore, if it is measured in seconds it will be $$g=T_s\frac{D-1}{2}\tag{2}$$...
• 4,285
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### preprocessing raw ECG data

I need to preprocess raw ecg data in R, here is a sample already standardized. I'm not an expert in signal processing nor experienced in working with medical data,... Not being an expert on how the ...
• 10.7k

### Adaptive filtering: Optimum filter length and delay

In order to be able to choose an optimal value for the delay $\Delta$ it's important to understand how the system works. The purpose of the delay is to decorrelate the desired signal $s(n)$ and the ...
• 90.3k

### Filtering without using any transforms

You can achieve this result by using two combs filters : https://en.wikipedia.org/wiki/Comb_filter Put simply, the comb filter consists of adding a delayed version of the signal to itself, causing ...
• 316
Accepted

### Filter before or after multiplication of two signals?

A personal rule: in general, it can be better to perform non-linear operations before linear ones. One reason behind that is that a lot of practical concerns are related to outliers or suspect ...
• 31.9k
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### How determine the delay in my signal practically

The Least Mean Square solution to find the "channel" or response of the filter is provided by the following MATLAB/Octave Code using the input to the filter as tx and the output of the filter as rx. ...
• 51.9k
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### Derivation of the lowpass to bandpass transformation

You're right that the multiplication of a low pass and a high pass filter results in a band pass filter, as long as the cut-off frequency of the low pass is higher than the cut-off frequency of the ...
• 90.3k

### How to estimate the local trend in a signal?

Start simple: just use a 1-D median filter of an appropriate length. If I do that with a length of 100 samples, I get the following for your first signal. The top plot shows the original signal (blue)...
• 25.8k
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### Smoothing a staircase

Looks like your data is virtually free of noise. That, combined with a very high sampling frequency would mean that at the jumps the data is exactly at the threshold between two quantized values. Set ...
• 13.5k
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### Undoing a filter operation in MATLAB

In general it's only possible to implement causal and stable filters. There are exceptions where marginally stable filters are used, but this doesn't apply here. So if you want to invert a given ...
• 90.3k

• 28.3k

### Filter before or after multiplication of two signals?

In general you will need to multiply first and then low pass filter. You also have to make sure that your sample rate is high enough so the multiply doesn't create aliasing. Let's look at a simple ...
• 45.3k
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### Filter: IIR Filter

There are many ways to arrive at filter coefficients, depending on your specs. But from your question I assume that you're talking about basic second-order building blocks (biquads). Also here there ...
• 90.3k
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### A Simple Algorithm to Filter / Smooth / Denoise a Noisy Staircase Graph

Assuming you meant to produce something similar to the green line: What about $$\text{output}[n] = \max\{\text{input}[n-k], \text{input}[n-k+1], \ldots ,\text{input}[n]\}$$ i.e. you just find the ...
• 31.1k
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### Using oversampling to increase resolution of a DC-signal as input

My input signal is a dc signal (sensor output) and im getting kind of a headache to understand why oversampling can increase the resolution of dc signals. The ADC puts out integers. So, let $x$ be ...
• 12.8k
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### How to implement the recursive FIR filtering of a signal with zero boundary condition?

New Answer I think there is a much easier and more general way to tackle this. Let's assume we have a sequence of $h[n]$ that has finite support on $[K,L]$ where $K$ is the index of the first non-zero ...
• 45.3k
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### Amplifier Placement in a Wireless Receiver

GrapefruitIsAwesome's answer is right in mentioning that Friis noise formula says to put the most amplification possible as far up front as possible to minimize overall noise figure, but I'd like to ...
• 31.1k
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### Autocorrelation function of a filtered periodic signal

(Note to others: Please donâ€™t edit this yet as OP and I are still working through certain details to make this clearerâ€¦ once this not is gone, feel free to make updates ) This was a (advanced) ...
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### Why does convolution give the output of a passing a signal through a filter?

You can describe the system with an operator acting over an input $x(t)$ transforming it into $z(t)$. If $L$ is the operator, $z(t)=L[x(t)]$. Remember that the system and the operator are linear and ...
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### What's the point of differential beamforming?

Introduction To my (rather limited) knowledge, the main advantage that made Differential Microphone Arrays (DMA) popular is their ability to have a frequency invariant beampattern (up to some certain ...
• 1,314
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### Understanding the Farrow Filter

I like this diagram a little better (it's equivalent) Now, while most of the time the Farrow structure is associated with Lagrange interpolation, it need not be Lagrange. It can be any decent ...

### Optimal Level of Wavelet Decomposition for Denoising

Best denoising should be related to certain quality measures, often requiring the clean signal reference, which you do not have in general. Or you could rely on some reference-free measures. To the ...
• 31.9k

### preprocessing raw ECG data

I do not have a lot of experience in analysing ECG data. However, it does not look, to me, like any ECG I have seen, or the patient is stone dead. I would at least expect a "regular" baseline, and ...
• 31.9k