All-pass Filter Research Articles

MO-CCCII-Based Single-Input Multi-Output (SIMO) Current-Mode Fractional-Order Universal and Shelving Filter

This study introduces an innovative filter topology capable of providing simultaneous positive and negative gain outputs for one-fractional order LP, with high-pass, all-pass, and fractional-order shelving filter responses. The circuit, utilizing multi-output second-generation current-controlled conveyors, stands out as the first to deliver ten outputs, incorporating both integer and fractional-order filter responses, without requiring additional components. Its current-mode design simplifies the process, employing minimal active and grounded passive elements, making it appropriate for low-voltage/low-power applications. The filter utilizes fifth-order Oustaloup approximation and Foster type-I RC networks for fractional-order capacitors, providing enhanced control over the transition slope. PSpice simulations confirmed a 1 kHz cut-off, showcasing low power consumption, minimal noise, and a wide dynamic range, positioning the filter as suitable for sensors, control, and acoustic applications.

Dual-port circularly polarized dielectric resonator–based antenna with reconfigurable integrated multifunctional filter for 5G cognitive radio applications

Abstract In this paper, the design of a circularly polarized (CP) multiple-input–multiple-output (MIMO) antenna system is presented, utilizing a dielectric resonator (DR). This presented antenna system is subsequently integrated with a multifunctional filter, all meticulously structured on a single substrate. The multifunctional filter operates in three modes: reconfigurable band-pass and band-reject filter as well as all-pass filter. The overall structure works as a tunable filtenna. The designed filtenna is expanded into a two-port MIMO system on a unified substrate, providing strong port isolation below −28.5 dB. The overall dimension of proposed radiator is 180 × 180 × 1.6 mm3. The value of peak gain is 5.19 dBic. By switching the states of PIN diodes, the designed filtenna operates as a sensing and communicating antenna for interweave and underlay cognitive radios (CRs). The proposed antenna supports the CP waves within the working band, i.e., 3.6–4.5 GHz. The simulated results are validated by comparing them with the measured results showing less variation among them. MIMO parameters, including the envelope correlation coefficient and diversity gain, have been calculated for the proposed filtenna, representing its suitability for 5G-CR applications.

A Phase Correction Model for Fourier Transform Spectroscopy

In Fourier transform spectroscopy (FTS), the conventional Mertz method is commonly used to correct phase errors of recovered spectra, but it performs poorly in correcting nonlinear phase errors. This paper proposes a phase correlation method–all-pass filter (PCM-APF) model to correct phase errors. In this model, the proposed improved phase correlation method can correct linear phase errors, and all-pass filters are applied to correct the residual nonlinear phase errors. The optimization algorithm for the digital all-pass filters employs an improved algorithm which combines the subtraction-average-based optimizer (SABO) and the golden sine algorithm (Gold-SA). The proposed PCM-APF model demonstrates high correction precision, and the optimization algorithm for the filters converges faster than traditional intelligent optimization algorithms.

Voltage-Mode Multifunction and Universal Biquads with Two CFOAs

In this paper, a new voltage-mode (VM) multifunction filter including only two grounded capacitors, three resistors, and two current feedback operational amplifiers is introduced. This filter with one high input impedance and two low output impedances can simultaneously provide band-pass filter (BPF) and low-pass filter (LPF) responses with an adjustable gain. A universal VM filter topology with three inputs and one output generating high-pass filter (HPF), BPF, LPF, notch filter, and all-pass filter (APF) responses is obtained from the multifunction one. It has the same number of active and passive elements as the multifunction and a low output impedance. Sensitivities of both introduced filters are low enough. However, the APF of the introduced universal filter has a passive element-matching problem. As an example, parasitic impedance effects are considered for the LPF of the universal filter, while non-ideal gain analyses are given for the HPF. To see how the introduced universal filter works, countless simulations are performed through the SPICE (Simulation Program with Integrated Circuit Emphasis) program in which 0.13 [Formula: see text]m IBM CMOS technology parameters are utilized. DC supply voltages are selected as ± 0.9 V. Also, several experiments using commercially available AD844s with ± 10 V supply voltages are carried out to see the performance.

Versatile All-pass Filter Circuits

Three single OA circuits for all-pass filter are suggested. They are economical due to a smaller number of components. They can easily be converted into band reject filter, and also band pass filter on complementary transformation.

Single‐differential difference current conveyor‐based first‐order VM/TAM universal filter and its applications

AbstractA new first‐order universal filter structure is presented in this article using a single differential difference current conveyor (DDCC). The proposed circuit can provide three first‐order filter functions namely, high‐pass filter (HPF), low‐pass filter (LPF), and all‐pass filter (APF) in voltage mode (VM) and transadmittance mode (TAM) both. A voltage amplifier with a gain of 2 is required for the realization of the APF functions in both the modes while for LPF and HPF, no condition is required. The pole frequency and gain of the proposed circuit can be controlled separately. The effect of the parasitic impedances of the DDCC has been modeled in the nonideal equivalent circuit from which nonideal parameters have been evaluated and compared with their ideal ones. Application examples of the proposed circuits configured as amplitude equalizer (in both modes) and in the realization of a simple wideband band‐pass filter are also discussed. The functionality of the proposed circuit as well as its mentioned application circuits is verified using complementry metal oxide semiconductor DDCC to support the theoretical propositions. Some experimentally observed frequency responses and transient responses of the various VM filters have also been corroborated using DDCC implemented using AD844 ICs.

Design of IIR full-band differentiators with improved nearly linear phase

Linear, or almost linear phase in the design of digital differentiators depends both on the method of calculation of the filter coefficients and the adopted structural design. Acknowledging the importance of this design objective, we developed a method to derive infinite impulse response differentiators which tackles it from both perspectives and yields improved characteristics compared to our previous design. We have replaced the differentiator structure comprising an all-pass filter and a delay line with a configuration of two infinite impulse response all-pass filters. Furthermore, we provide a procedure for determining an improved initial solution to the optimization of filter coefficients, as well as a procedure for improving the differentiator's magnitude response. The final solution exhibits considerably lower error at low frequencies and is thus suitable for the common scenario where the relevant spectral content decreases with frequency. The proposed filters of third and fifth order outperform many existing solutions in literature, especially in terms of the phase characteristic and time-domain performance.

Active RC Realization of a First-Order All-Pass Filter with a Difference Amplifier

In this tutorial article, we present an active RC realization of a first-order all-pass filter using a difference amplifier. It has the desirable feature of equal resistors, which eases its fabrication, particularly in the IC form. A detailed analysis is followed by design considerations.

Short‐critical‐path algorithm for allpass transform

AbstractAllpass transform is a key element of the discrete systems which produces signal processing in warped frequency domain. The paper presents a new short‐critical path algorithm for allpass transform, which essentially consists of calculating the outputs of allpass filters chain. The algorithm is based on the proposed dual allpass filter structure, which computes the outputs of a cascade of two allpass filters in one computational pass. The dual allpass filter structure is obtained using the state variable representation of the allpass filter. The efficiency of the proposed algorithm is analyzed in the context of allpass transform implementation using a general purpose CPU. The results of the experiment show that the use of the proposed algorithm accelerates the calculation of the allpass transform by 1.81 times.

Novel Second-Order Fully Differential All-Pass Filter Using CNTFETs.

In this paper, a new carbon nanotube field effect transistor (CNTFET)-based second-order fully differential all-pass filter circuit is presented. The realized filter uses CNTFET-based transconductors and grounded capacitors. An active-only second-order fully differential all-pass filter circuit topology is also presented by replacing the grounded capacitance with a CNTFET-based varactor to achieve filter tunability. By controlling the varactor capacitance, active-only second-order fully differential all-pass filter tunability in the range of 15 GHz to 27.5 GHz is achieved. The proposed active-only circuit works on -oltage, low-power dissipation and high tunable pole frequency. The realized circuit operations are verified through the HPSPICE simulation tool. Deng's CNTFET model is utilized to verify the filter performances at the 16 nm technology node. It is seen that the proposed filter simulation justifies the theoretical predictions and works efficiently in the deep-submicron technology.

The development of a fully balanced current-tunable active-RC all-pass filter

This research paper presents a symmetrical current-tunable active-RC all-pass filter that uses an active BJT coupled with R and C. The circuit's symmetrical structure ensures that the differential signals are treated equally, resulting in improved performance. Furthermore, the filter's ability to adjust the frequency by bias current makes it suitable for a wide range of applications, such as improving phase properties and creating other types of filters. The simulation results obtained through the Pspice program show that the value of the operating frequency can be adjusted by bias current, which is the highlight of this research. The transfer function of the circuit shows a response of about 0 dB and –90° respectively, indicating that the circuit can change the phase of the input signal without changing its magnitude. This feature is particularly useful in signal processing applications where phase changes are required. In addition, the paper discusses how the operating frequency can be increased by decreasing the capacitor. The transfer function of the circuit analyzed shows that the operating frequency (f0) is inversely proportional to the product of the capacitors. Therefore, decreasing the value of C increases the operating frequency of the circuit. Monte Carlo analysis results are also presented for resistors, capacitors, and transistors with error values. This analysis helps determine the effect of errors on the output signal of the circuit. The results show that the output signal is sensitive to changes in the resistor values, which can affect the accuracy of the filter. Therefore, it is important to select high-quality resistors to ensure that the filter operates accurately

Three inputs and one output voltage-mode universal biquadratic filter using one CCII and one CCIII

A voltage-mode universal biquadratic filter using one second-generation current conveyor (CCII), one third-generation current conveyor (CCIII), two capacitors and two resistors is presented. The proposed voltage-mode biquadratic circuit has three input terminals and one output terminal and can realize all the standard filter functions that are highpass, bandpass, lowpass, notch and allpass filters without changing the circuit topology. Both its active and passive sensitivities are small. The proposed circuit does not need one more active component for the unity-gain inverting of the input signal in each filter realization.

An all-pass based internal model principle controller for galvanometer mirror steering

Galvanometer is a critical component for beam steering in additive manufacturing, profilometry, and medical imaging. In these applications, the quality of the process relies on the precision motion control of the galvanometer to either track or reject narrow-band signals. From the internal model principle, this can be accomplished by incorporating the dynamic model of the reference or disturbance signal in the feedback loop. This paper proposes an innovative internal model principle controller based on numerically robust all-pass filters. The main concept revolves around converting the controller design into a phase response design problem with all-pass filters. For the proposed approach, the targeted frequencies of the internal model can be arbitrarily placed without sacrificing the performance. Further, it produces lower-order controller and is robust against quantization effect. When combining with frequency estimation algorithm and adaptive filter, it can be readily applied to unknown and time-varying disturbance rejection. The advantages of the proposed method are demonstrated by comparing with conventional approaches through analysis, simulation, and experimentation.

A Concept for Myocardial Current Density Estimation with Magnetoelectric Sensors

Abstract In this paper we present a novel noninvasive approach to estimate current densities in the heart from magnetocardiography. The proposed algorithm uses nested optimization to model current densities in equally-sized voxels of myocardial tissue. First-order Thiran all-pass filters are used to describe the propagation between voxels.We demonstrate feasibility of the algorithm for a noise-free single-layer simulation. However, challenges remain, such as addressing measurement noise and optimizing propagation velocity. Overall, this approach has the potential to complement or replace invasive catheter-based electrophysiological studies for localization of arrhythmogenic tissue.

An Alternative Circuit for an RC Active All-Pass Filter

Presented here is an alternative to an RC circuit for active all-pass filter which was published more than half a century ago. The alternative circuit has some advantages over the original one.

Gain-Controllable Transadmittance-Mode First-Order Allpass Filters with Electronic Tune Using Single Active Element

First-order allpass filters are analog filters with a unit magnitude response, but they change the phase shift between input and output signals at various frequencies. This paper presents the transadmittance-mode first-order allpass filters based on the modified current-controlled current differencing transconductance amplifier (M-CCCDTA). The proposed filters utilize a single M-CCCDTA and a grounded capacitor with no external resistors, making them well suited for implementation in an integrated circuit. The gain and phase response of the proposed filters can be adjusted electronically and separately. Also, the high output impedance of the proposed filters at both the input voltage node and the output current node makes cascading easy without the need for buffer devices. A quadrature sinusoidal oscillator based on the proposed first-order allpass filter has been designed as an example of an application. The PSpice simulation and actual experiments are utilized to validate the functionality of the proposed filters. The simulation and experimental results are consistent with the idea of anticipation.

Convertible Bandstop to Allpass Filter using Defected Ground Structure with Ideal Switch for Millimeter-Wave Band in 5G Application

According to this study, a defective ground structure (DGS) with an ideal switch can be used to create a bandstop to allpass filter for 5G applications. The redesigned Hairpin DGS's bandstop and allpass responses are mathematically investigated in this paper. Utilising an ideal switch via open circuit and short circuit conditions on DGS, the convertible filter is operated. Therefore, the filter's performance in terms of return loss, attenuation, and insertion loss is simulated. As a result, the filter operates at 25.875 GHz in open circuit condition with a narrowband (2.16 GHz) bandstop response at 10 dB and a maximum attenuation of 29.5 dB, and at 26 GHz with a wideband allpass response and return loss greater than 10 dB. As a result, the filter is appropriate for 5G applications that use millimeter-wave RF front-end systems.

DESIGN OF FIRST ORDER DIFFERENTIATOR WITH PARALLEL ALL-PASS STRUCTURE

In this paper a new method for design of the first order differentiator is presented. The proposed differentiator consists of two parallel branches, i.e. direct path and IIR all-pass filter. The described design method allows one to obtain solution with minimum mean relative error at the desired region by controlling the ratio of phase response extremes. A small relative magnitude error, as well as a low phase error, at low frequencies is condition for good time domain behaviour. The obtained differentiator can be realized by means of only two multipliers, hence being a good choice for real time applications. The proposed solution provides a lower magnitude error than several known differentiators with similar phase error.

A fully balanced first order high-pass filter

The topic of this article is the design of a fully balanced first-order high-pass filter and its two circuits. The first circuit is a fully balanced current-tunability first-order high-pass filter consisting of four NPN transistors and a single capacitor, which is a simple design and quite compact. The pole frequency can be adjusted with a bias current. The results of the first circuit shows the phase and gain responses, the phase and gain responses when adjusted with a bias current, the time-domain response, and the harmonic spectrum. However, this circuit found a flaw in the temperature that affects the pole frequency, and total harmonic distortion is relatively high. Therefore, the second circuit improves defects by the CAPRIO technique to reduce the total harmonic distortion, and the resistors in the circuit are added to the design to replace the resistance and the effect of temperature on the properties of the transistor. This circuit consists of four NPN transistors, four resistors, and a single capacitor. The resistors in this circuit can be adjusted to change the pole frequency and voltage gain. The results of the second circuit show the gain and phase responses of the proposed circuits, the phase and gain responses when adjusted to the value of the resistor, the phase and gain responses at various temperatures, as well as their time-domain responses and total harmonic signal distortion. The all-pass filter is also made using the filter introduced in the second circuit because of its voltage gain-adjustable property. So, if the suggested circuit is constructed in combination with a buffer circuit to make it feasible to function as an all-pass filter, the result will be an all-pass filter. In accordance with the results of this study, we have introduced a design for a high-pass filter to reduce total harmonic distortion and the effect of temperature

The Versatile All-pass Filter

It is shown that two other types of filters, viz., band-pass and band-reject, can be derived from a given all-pass filter. For illustration, we consider RC active all-pass filters, and show how starting from such a given circuit, one can obain band-pass or band-reject filters, simply by subtraction from, or addition to, unity, to the all-pass one. The corresponding circuit diagrams for implementations are also shown, and simulation plots have been drawn to illustrate the validity of the above facts.