Explore chapters and articles related to this topic
Passive Filters
Published in Daniel B. Talbot, Practical Analog and RF Electronics, 2020
From Figure 8.1, it is obvious that bandstop filters (top trace bracketing 9 and 11 MHz) pass low and high frequencies while rejecting middle frequencies, according to a shape dictated by the designer. A highpass filter (bottom trace) does the obvious (i.e., it passes high frequencies). A bandpass filter passes a range of signal frequencies and rejects others below and above that range. A simple notch filter can be realized by subtracting the bandpass response from the unfiltered path. That would make a narrow V-shape notch which barely qualifies as a bandstop filter. We will discuss a better way to make a notch filter in Section 8.12. An allpass filter is one that passes all signals equally regardless of frequency. It is a specially tailored type which modifies the phase versus frequency according to a desired curve, thus attempting to correct the varying phase versus frequency of one of the other filter classes. It is sometimes called a group delay compensator.
Analog Signal Conditioning in Instrumentation
Published in Robert B. Northrop, Introduction to Instrumentation and Measurements, 2018
In summary, note that the frequency response magnitude function for the all-pass filter is unity over all frequencies; only the phase varies. When s = jω in Equation 2.87, the phase of the frequency response function is given by () ϕ=−180°−2tan−1(1−ω2R32C2ωCR3R/R2).
Digital Filtering
Published in David C. Swanson, ®, 2011
Nonminimum phase numerator polynomials can be seen to contribute to the system delay. To examine this further, we consider a simple FIR system for real signals with a pair of conjugate-symmetric zeros corresponding to 60 Nepers at 300 Hz. With a digital sample rate of 1000 Hz, the two zeros map to a magnitude of e+0.06, or 1.062, and angles ±0.6π, or ±108°, on the z-plane. Since the zeros are slightly outside the unit circle, the inverse filter (which is an AR IIR filter) is unstable. However, we can minimize the FIR filter’s phase without affecting its magnitude response by adding an all-pass filter Hap [z] in series. As seen in Figure 3.5, the all-pass filter has a pole to cancel each zero outside the unit circle, and a zero in the inverse conjugate position of the pole to maintain a constant frequency response.
Acoustic Features Modelling for Statistical Parametric Speech Synthesis: A Review
Published in IETE Technical Review, 2018
Nagaraj Adiga, S. R. M. Prasanna
The synthesis procedure of STRAIGHT model involves generations of voiced excitation using the F0 and aperiodicity measurements which accounts for harmonic information. The impulse train is weighted by the aperiodicity spectrum and then added with a random phase to scale down the buzziness present in the synthetic speech. The phase is determined using an all-pass filter designed with a fixed group delay. The generated mixed excitation for each frame is then convolved with the minimum phase MLSA filter response. The process of generating synthetic speech y(t) is mathematically represented as and where e(t) represents the excitation. Here, Φ(ω) is an all-pass filter function used to add the random phase. The vocal-tract filter response V(ω, t) is given by where ct(q) and q represent the cepstral coefficients and quefrency, respectively.
Group delay equalisation of discrete Butterworth tan filters in the continuous domain
Published in International Journal of Electronics, 2020
Negovan Stamenković, Nikola Stojanović, Nikola Novaković
In this section, the group delay equalisation of the original filter is carried out with the aid of the all-pass filter (group delay equaliser) which is in cascade connection with the original filter. The frequency response of an all-pass filter exhibits unit magnitude at all frequencies. Let us assume the transfer function of degree with real coefficients of the discrete all-pass causal filter in the form,