# Tag Info

Accepted

### Which order to perform downsampling and filtering?

You need to filter first and then downsample. Otherwise, you will run into aliasing problems. I.e. frequencies that are above 30 Hz will create images within your frequencies of interest. You can ...
• 6,098
Accepted

### Is there an adjective describing a filter with kernel that has zero mean?

"Zero-Mean" is the word that's commonly used to describe signals and signals with a zero average. "This is a zero-mean filter." If you really mean a filter that is specifically ...
• 26.9k
Accepted

### SOS-matrices' order does not correspond to given parameter when designing bandpass with scipy.signal.butter

Your expectations are reasonable. However, the definition of order in the design routine is confusing. It's the same in Matlab/Octave. For lowpass or highpass ...
• 81k
Accepted

### How is the lowpass to bandpass transformation derived?

In the $s$-domain, the LPF-to-BPF transformation doubles the order of the filter. that is because the LPF has one transition from passband to stopband, but the BPF has two such transitions. Remember ...

### Frequency Domain Filtering

This is just "faking" the magnitude response of an IIR filter. The output's magnitude spectrum looks just like it has been filtered by the IIR filter with the given frequency response. Although it may ...
• 4,125
Accepted

### Real and complex low pass equivalent of band-pass signal

It's not true that any real-valued band pass signal can be written as shown in your first equation: $$s(t)=A(t)\cos(\omega_c t)\tag{1}$$ The most general representation of a real-valued band pass ...
• 81k

• 27.1k
Accepted

### Passband vs Baseband Bandwidth

You can unify the definitions for baseband and passband bandwidths by saying that bandwidth is only measured at positive frequencies. So for low pass signals, the lower frequency is zero and the upper ...
• 81k
Accepted

### Quadrature component - condition on equivalent lowpass signal

Your idea with the Hilbert transform doesn't work. The only signal (apart from $x(t)=0$) for which the Hilbert transform is zero, is a constant signal. A band pass signal $x(t)$ can be written in ...
• 81k

### Filter odd or even harmonics with notch or inverse notch filter

If the OP is actually interested in selecting only one individual frequency from the even or odd harmonics, then a moving average filter (MAF) would be ideal since this can provide a null at every ...
• 38.4k
Accepted

### What is the relationship among digital filter cutoff frequency, signal frequency and filter settling time?

With "Settling Time" we can consider the overall time delay of the filter, and the rise/fall time of a transient change going through the filter. The rise/fall time will inversely related to ...
• 38.4k
Accepted

### Tradeoff between Filter Order and Sections

Large order single stage filters are inherently problematic. Calculating the numerators and denominator from the poles and zeros is an ill defined problem and numerically unstable. Furthermore Direct ...
• 34.2k