Search

This paper picks up the need for a wide range programmable corner frequency for anti-aliasing and antiimaging filters in on-chip impedance spectroscopy and sensor signal readout circuitry with self-X properties (selfdiagnosing/healing) for industry 4.0 applications. A fourthorder wide tunable range MOSFET-C low pass filter is designed by using XFAB 0.35 μm CMOS technology and Cadence design tools. The proposed circuit is based on fully differential Sallen-Key architecture with Butterworth approximation. It covers a frequency range from 30 Hz up to 7 MHz. Tunability is achieved using a potentially high resistance and linearized configurable MOS resistor to control the filter pole frequency. The configurable elements in the circuit serve as tuning knobs to be controlled by machine learning. The physical design area is 0.39mm2.

Multisim is a Windows-based simulation tool launched by National Instruments Inc., which is suitable for the design of analog/digital circuit boards at board level. It includes the graphic input of circuit schematic diagram and the input of circuit hardware description language. It has a rich simulation and analysis ability. Compared with the traditional manual calculation and design circuit, it can be designed and simulated more simply and quickly through Multisim simulation software. Through further analysis and simulation of the improved Sallen-Key filter network of different orders, the Sallen-Key active filter network is designed as the filter forming circuit in the spectrometer amplifier. Through the observation and comparison of the output waveform, the characteristics of the filter forming circuit can be clearly understood and mastered, which provides a reference for the virtual simulation experiment teaching nuclear power electronics.

Background: The original filter including grounded or virtual ground capacitors can be synthesized by using the NAM expansion. However, so far the filters including floating capacitor, such as Sallen-Key filter, have not been synthesized by means of the NAM expansion. This is a problem to be researched further. Methods: By using the adjoint network theory, the Sallen-Key filter including floating capacitor first is turned into a current-mode one, which includes a grounded capacitor and a virtual ground capacitor. Then the node admittance matrix, after derived, is extended by using NAM expansion. Results: At last, one VDTA Sallen-Key filter is received. It employs single compact VDTA and two grounded capacitors. Conclusion: A Butterworth VDTA second-order frequency filter based on Sallen-Key topology with fo = 100kHz, HLP = -HBP=1, is designed.

The local fractional derivative (LFD) has attracted wide attention in the field of engineering application. In this paper, the LFD is used to model the fractional Sallen-Key filter for the first time. The non-differentiable(ND) transfer function is obtained by using the local fractional Laplace transform(LFLT). And the amplitude frequency response is analyzed in detail for different fractional order ς. It is found that the fractional Sallen-Key filter becomes the ordinary one in the special case ς = 1. The obtained results of this paper show the powerful ability of local fractional calculus in the analysis of complex problems arising in engineering fields.

An analog circuit fault diagnosis method based on multi- data correlation kernel is proposed, and the UCI data set is used to verify the effectiveness of the proposed method. Then, a fault diagnosis method structure of tolerance circuit based on SVM is proposed. Taking Sallen key filter circuit as an example, the specific steps of establishing an analog circuit fault diagnosis model, including fault injection, are introduced: circuit simulation, fault feature extraction, and design of SVM fault classifier based on multi-data correlation kernel. Then, the Sallen key filter circuit and leap frog filter circuit are selected as the diagnosis objects. The HSPICE software is used to inject the fault into the circuit under test and establish the fault simulation model, so as to obtain the circuit data under different circuit states, and the circuit samples are used to establish the fault classifier based on SVM. Finally, the effects of SVM + MK, SVM + DK, and SVM + MDK on the fault classifier diagnosis are compared. The experimental results show that the three methods used in this paper are better than the analog circuit fault diagnosis method based on standard SVM, and the proposed analog circuit fault diagnosis method based on multi-data correlation kernel is the best in terms of diagnosis effect. On this basis, the SVM + MDK algorithm is more effective The establishment time and diagnosis efficiency of the model are relatively good.

Based on an improved proportion-integral-type (PI-type) memristor emulator and an active Sallen–Key high-pass filter (HPF), a new memristive Chua’s circuit with inductor-free implementation is presented in this paper. The memristive Chua’s circuit possesses a line equilibrium state with unstable and stable region distributions, leading to the emergence of multi-stable patterns, i.e., the coexistence of multiple attractors for different initial values. With the normalized mathematical model, local basins of attraction, bifurcation plots and phase plane plots are numerically simulated, from which the initial values-related bifurcation behaviors are demonstrated and coexisting multiple attractors are obtained in the presented memristive Chua’s circuit. Finally, circuit simulations by PSIM software are performed and the results verify the numerical plots.

Memristor is considered to be the fourth fundamental circuit element, along with resistor, capacitor and inductor. It is assumed to occupy very less chip area, consume low power and provides good manufacturability at low nanometer technologies. In this paper, memristor-based unity-gain Sallen–Key filters have been designed and proposed. These filters provide the flexibility of electronic adjustment of parameters, something that was not possible in conventional Sallen–Key filters. Moreover, the proposed filters provide better performance at low nanometer technologies due to its better characteristics at these technologies. To justify the stated results, simulations of the proposed circuits have been carried out using EldoSpice by Mentor Graphics and using linear ion drift model of memristor. Simulated results depicted that memristor behaves as a simple resistor at frequencies greater than 100 Hz as well as at initial resistance (RINIT) greater than 11 kΩ. The cut-off frequency of simulated filters has been observed to be 14.46863 Hz which is well in agreement with theoretically calculated values. This value and thereby bandwidth and Q-factor can be varied by changing RINIT.

This paper presents a ringing test for 2nd-order Sallen-Key low-pass filters. A comparison measurement is constructed, which takes into account the measurement of a self-loop function in a transfer function. Based on the phase margin at unity of the self-loop function, a general stability criterion for second-order linear systems is proposed in terms of operating regions. In case of under-damping region, the ringing occurs and makes the system unstable. The advantage of the proposed criterion lies in its simplicity than some of the existing results. The new stability criterion is applied to the network based negative feedback issues. Experimental results show that the proposed method is quite effective.

This document presents a low-voltage CMOS electronic system for electromyographic (EMG) signals acquisition. For its development, the system requirements and characteristics were established and simulations were made using Virtuoso Cadence software for 180 nm TSMC technology. The circuits used were implemented in the subthreshold regime for low potential consumption. As result, a two-stage system was obtained, the first stage is an instrumentation amplifier based on a current conveyor, supplied with 0.7V, consuming 55µW and a common-mode rejection ratio (CMRR) of 190dB. Besides, the second stage involves proven Sallen Key filters that were implemented using different design parameters, both high and low pass with a cutoff frequency of 20Hz and 1.3KHz, respectively, with 8dB gain, supplied with ±0.35V and power dissipation of 2.99µW, for each filter.

Pulse shapers are widely used in particle detector applications to reduce the rise and fall times of the pulse signal and to remove noise from the frontend amplifiers. We demonstrate a low-noise, low-power pulse shaper employing an active lowpass Salley-Key biquad filter, passive highpass filter, and input/output buffers. The design process is described to generate the desired transfer characteristic while incorporating tuning knobs to adapt the shaper characteristic to the needs of different applications. Utilizing only a single 1.8-V supply, the shaper consumes 1.5 mW and achieves an input-referred noise of 17 μV rms , both the lowest among state-of-the-art. The power efficiency normalized to bandwidth and noise is nearly 1.7× better than the next best design.

Fractional order filters are the emerging area for design of the filters for producing the best performance in the field of electronic circuits and systems. In this paper, a High-pass fractional order Sallen-Key filter is being studied using two fractional order capacitors FC 1 and FC 2 . Where, the orders of the capacitors $\mathrm{FC}_{1}$ and FC 2 vary as $0.1\leq\alpha\leq 1.0$ and $0.1\leq\beta\leq 1.0$ respectively. The proposed filter circuit is being implemented in MATLAB/Simulink and their mathematical equations are being obtained in s-domain. Thereafter, the magnitude and phase equations are being derived. Here, both frequency and time domain analysis are being resulted and analysed.

In this paper, we highlight the optimal design of an active fourth-order band-pass filter for radio frequency identification (RFID) system reader to reject all signals outside the band (10–20) kHz and to amplify the low antenna signal with a center frequency of 15 kHz. The filter is designed to have a Butterworth response, and the topology that will be used to implement this filter is Sallen–Key. The values of the passive components are selected from manufactured series; thus, it is very exhaustive to search on all possible combinations of values from those series for an optimized design. The metaheuristics have proved a capacity to deal with such problem effectively. In this work, the metaheuristic genetic algorithm (GA) is applied for the optimal sizing of the fourth-order band-pass filter. SPICE simulations are used to validate the obtained results/performance.

For fault diagnosis of nonlinear analog circuit, a novel method based on generalized frequency response function (GFRF) and least square support vector machine (LSSVM) classifier fusion is presented. The sinusoidal signal is used as the input of analog circuit, and then, the generalized frequency response functions are estimated directly by the time-domain formulations. The discrete Fourier transform of measurement data is avoided. After obtaining the generalized frequency response functions, the amplitudes of the GFRFs are chosen as the fault feature parameters. A classifier fusion algorithm based on least square support vector machine (LSSVM) is used for fault identification. Two LSSVM multifault classifiers with different kernel functions are constructed as subclassifiers. Fault diagnosis experiments of resistor-capacitance (RC) circuit and Sallen Key filter are carried out, respectively. The results show that the estimated GFRFs of the circuit are accurate, and the fault diagnosis method can get high recognition rate.

This brief presents a programmable second-order bandpass switched-capacitor filter implemented for an Internet-of-Things water management sensor node. The filter circuit, which is based on the Sallen-Key topology, is implemented using a low-gain amplifier ( ${\boldsymbol \mu }\text{W}$ .

An integrated programmable order multiple feedback (MFB) band-pass filter (BPF) implemented in 0.14 um CMOS technology is presented. The modular single ended filter has been used in an FSK transceiver, in both receiver (RX) and transmitter (TX). It is implemented by cascading different types of BP filters with different required bandwidth (BW) of RX and TX. A combination of Bessel and Butterworth filters to maximize stop-band rejection, optimize in-band flatness and minimize group delay variation is used. Each stage of the MFB filter draws 0.3mA of current from a 1.8V supply. A simple and efficient approach to trim center frequency which has minimum impact on area and parasitic components has been used. AC gain change of TX due to mismatches, parasitic and process and trimming has been compensated by a simple gain stage while it is budgeted in RX system SNR. The implemented 23.2MHz center frequency filters have been used in the FSK transceiver of a USB power delivery (PD) system, with a BW of 3.46MHz for RX filter and a BW of 1.3MHz for TX filter. The employed low current and small area architecture with its efficient trimming strategy meets the required performance of the FSK transceiver.

The class-E power amplifier with shunt filter, which is also known as the class-E power amplifier with shunt capacitance and shunt filter, is proposed in this brief for any duty ratio. The basic circuit waveforms and design equations are derived and the design parameters of the circuit elements for some selected duty ratios are numerically solved. Subsequently, the characteristics of the class-E power amplifier with shunt filter are discussed. Also, a simulation example is carried out to verify the presented design method. Compared with the classical class-E power amplifier, the presented class-E power amplifier with shunt filter has a higher achievable maximum frequency and requires less quality factor of the filter. It is a promising candidate to design broadband and high-efficiency power amplifiers.

This brief presents a filter-integrated high-efficiency class-F power amplifier (PA). The hybrid cavity–microstrip filtering circuit is employed not only to realize output impedance matching and the third-harmonic manipulation but also to provide high-selectivity bandpass responses. To fulfill the requirements of high-efficiency class-F PAs, cavity resonators and microstrip feeding structures are involved, and their benefits are fully exploited. The metal cavity resonator features a high $Q$ value and, thus, low loss in the passband, resulting in high efficiency. Moreover, metal walls of cavities act as heat sink for the transistor. The microstrip feeding structures are used to improve the skirt selectivity and manipulate the third harmonic. Moreover, it features easy integration with the transistor, and thus, the transition between cavity and microstrip lines is eliminated. The hybrid filter is characterized based on filter synthesis theory. Complex impedance conversion analysis is carried out to guide the impedance transformation from 50 $\Omega$ to a complex one desired by the transistor. For demonstration, a filtering PA operating at 2.4 GHz is designed and measured. It exhibits both high-selectivity bandpass responses and good PA performance with maximum power-added efficiency of 70.9% at 40.8-dBm output power.

This paper presents second order band-pass filter with high quality factor. Its high quality factor is provided by feedback circuit. The used second order filter is modified so that filters outputs through capacitor can be obtained to high impedance output. Thereby, there is no need the extra active element to obtain filter outputs. Also, the output stage of current differencing transconductance amplifier have only X− terminals instead of X+ and X− terminals. Furthermore, the quality factor of the band-pass filter with feedback circuit is increased by feedback gain consisting of only four transistors. Besides, to examine effects of parasitic elements, non-ideal and sensitivity, the overall structure is investigated deeply. Working conditions and boundaries of the overall structure is also defined. The simulation demonstrates good agreement between the theoretical expectations and simulation results.

In this paper, a variation-aware and reliable design of a fully integrated radio frequency (RF) bandpass filter realized using a voltage differencing transconductance amplifier is presented. The filter is characterized by its high frequency operation, low power consumption, high quality factor, and it is insensitive to process, voltage, and temperature variations. Sensitivity analysis has been performed to analyze the circuit performance in the presence of parasitics. The inductor-less approach finds its application in integrated building blocks of RF front ends, thus eliminating the requirement of off-chip filters in transceivers. Centered at 2.511 GHz and operating within the 36.21 MHz 3-dB bandwidth, the filter draws 0.168 mA from a ±1 V power supply, attains a voltage gain of 72.6 dB, a quality factor of 69.34 and noise figure of ~29.6 dB. In addition, it has a dynamic range of 125.84 dB-Hz and a 1-dB compression of −1.5 dBm which translates into a figure of merit as high as 94 dB.

The design of analog filter using active building block has been gained significant attention and has become an interesting research topic. A five-inputs single −output voltage-mode universal biquadratic filter using active building block, namely voltage differencing differential difference amplifier (VDDDA) is presented in this paper. The proposed filter consists of two VDDDAs and two grounded capacitors. The presented circuit has high impedance for all input voltage nodes and low impedance for output voltage node which is ideal for cascade in voltage-mode circuit without the use of buffer circuits. It can provide five output voltage functions which are band-pass (BP), low-pass (LP), band-reject (BR), high-pass (HP) and all-pass (AP) responses. For high-pass and band-pass functions, the inverting and non-inverting response can be achieved. The matching condition, the inverting and double gain amplifier are not required which is easy to select the output response by digital method. The natural frequency and quality factor can be electronically tuned that is attractive for microcomputer or microcontroller controllability. To verify the validity of proposed filter, the PSPICE simulation and experimental results using VDDDA constructed from commercially available IC are included. The measured results agree well with theoretical expect.

This paper presents a new lumped-element absorptive bandstop filter topology. It exhibits infinite attenuation at the center frequency and no reflection regardless of the quality factor ( $Q$ -factor) of the resonators. The new topology exhibits the absorptive characteristic with extremely low- $Q$ resonators, whereas an absorptive bandstop filter topology in the literature cannot be used for such resonators. This superiority of the new filter topology is verified by comparing it with the topology in the literature. The filter designed using the new topology can change its center frequency by tuning only the capacitor values of the resonators. A 1.6:1 frequency tuning range maintaining the absorptive characteristic has been obtained by measurement.

A critical study is made of a canonic second-order bandpass realization using a single-operational amplifier in low-gain (unity or two) connection. The circuit is suitable for low- and medium Q applications and features good stability, wide frequency range of operation and versatility of conversion to a high-pass filter. An all-grounded-capacitor version of the filter is also given; which is a desirable feature for integrated circuit (IC) implementation. The unity gain configuration presents component minimization over other similar circuits.

The Sallen–Key filter (S–K) is widely used in nuclear pulse signal processing because of its simple working principle and good performance. Related research has only reviewed the recursive numerical model of digital S–K using idealized parameters. The use of digital S–K thus has limitations under these circumstances. This paper comprehensively deduces a recursive numerical model of digital S–K and discusses the effects of resistance and capacitance on the filter quality factor, cutoff frequency and amplitude–frequency response. The numerical recursive function, transfer function and amplitude–frequency response are analyzed using different parameters. From a comparative analysis of the shaper in a simulation and an actual nuclear signal, an optimal parameter selection principle is obtained. Using different forming parameters, the energy resolution and pulse counting rate of the $$^{55}$$ Fe energy spectrum are compared and analyzed based on a Si-PIN detector. Capacitance has a stronger influence on the Gaussian shape, whereas the influence of resistance is stronger on the shaping amplitude.

Considering the difficulties in fault diagnosis for analog circuit, a combination method based on Wavelet Neural Network (WNN) method and Unscented Kalman Filter (UKF) algorithm is proposed for improvement of diagnosis accuracy. In the method, UKF algorithm is used to optimize the network parameters of WNN, which can train WNN fault diagnosis model for analog circuit. The experiment result shows that, compared with traditional WNN, the proposed method has better diagnosis accuracy for the fault in analog circuit.

In this work, we are going to implement the fractional calculus to design and analyse fractional order Sallen-Key type filter going through the concepts of differential integrals, use of Laplacian operator (sα) and design of a conventional RC filter with a reactance device. The motive behind this paper is to design the integer order Sallen-Key filters into fractional order domain. The elements of a conventional filter circuit are replaced by fractional order element such as capacitor or inductor. The feature of interest in fractional elements is their ability to control the impedance in frequency and time domain. The two fractional capacitors taken here are of equal order ‘α’ (0 < α < 1). The frequency response of the filters is obtained from transfer function simulated using MATLAB and then compared with the integer order filter response. Performance analysis of the fractional filters is made by comparing design parameters like cut-off frequency and peak–frequency only changing the order of filter without disturbing the energy storage elements.

To improve the performance and to reduce the errors caused by limited bandwidth in Phase locked loop, we proposed a method for modeling and simulation by usingSallen-key low pass filter with compensation methodology. The noise transfer functionis estimated, and simulation is performed for two different filter sections as a loop filter in the phase locked loop, namely: (i) idealSallen-key low pass filter, and (ii) compensated Sallen-key low pass filter. The complete simulation program for the proposed model is implemented in MATLABfor analysis. The characteristics of the system namely: (a) phase margin, (b) damping factor, (c) delay margin, and (d) stability, are studied with the help of Bode and Root locus plots. The propose model is found to be stable. The damping factor, phase margin and delay margin of the model is found to be 1, 86° and $0.524\boldsymbol{\mu}\mathbf{s}$ respectively.

This article presents a new topology for implementing an electronically tunable bandpass filter using the current-feedback operational amplifier. The electronic tuning of the center frequency of the proposed circuit is achieved using an externally connected voltage amplifier in the feedback path without disturbing the constituents of the filter itself, that is a shadow filter. The proposed circuit can be used for developing an undergraduate experiment which illustrates the operation of bandpass filter and the electronic control of its center frequency using the concept of shadow filter. Experimental results obtained using the AD844 current-feedback operational amplifier are included.

Minaei, Shahram (Dogus Author) In this paper, a new method is presented to increase the quality factor of bandpass filters employing active elements. Using the proposed method the values of the externally capacitors in filter structure are reduced. In this way chip area which is an important parameter in the integrated circuits can be minimized. Moreover, bandpass filters are investigated from the point of view of stability conditions and effects of the parasitic and non-ideal elements. Considering these effects, operating conditions and boundaries of the bandpass filter are calculated. To validate the feasibility of the method, an application example of bandpass filter used in intermediate frequency (IF) stage of AM receivers is given and the performance of the circuit is demonstrated by comparing the theory and simulation.

In this paper, a new voltage-mode all-pass filter topology based on single current operational amplifier (COA) and the implementation of COA by using current conveyors are presented. The proposed topology employs three admittances and single active circuit element. COA implementation by using current conveyor blocks as sub-circuit contributes to workability of the COA employing circuits by using commercially available integrated circuits that can be employed as current conveyor. The validity of the proposed filter is verified by PSPICE simulation programme by using the MOSIS 0.35 micron CMOS process parameters. The simulation results agree well with the theoretical analysis and the circuit achieve a good total harmonic distortion (THD) performance.

This present study reports a new type of inductor-free simplified Chua's circuit only using two-op-amps-based realisation, which is implemented by cascading a Sallen–Key low-pass filter with a simplified Chua's diode. With mathematical model-based numerical simulations and hardware circuit-based experimental measurements, it is demonstrated that the reported circuit exhibits the similar dynamical behaviours of the classical Chua's circuit such as point attractor, limit cycles, period doubling route, chaotic spiral attractors, double-scroll chaotic attractor, boundary crisis, coexisting bifurcation modes, and so on. Furthermore, the proposed circuit enriches the realisation forms of Chua's circuit family.

A compact dual-mode dual-band bandpass filter is proposed based on the inside–outside–reversed dual-ring topology. Different from the traditional design, the total size of the filter is limited by the second passband with shorter wavelength at higher frequency, instead of the first passband with longer wavelength at lower frequency. By loading four square patches in the inner ring, the degenerate modes of the inner ring move down and form the first passband, whereas the second passband is constructed by the outer ring. By utilising the coplanar-waveguide feeding at ground plane, a prototype of the dual-band filter with two operating frequencies at 0.92 and 1.47 GHz is designed and verified experimentally.

Multi-GHz lowpass filters are key components for many RF applications and are required for the implementation of integrated high-speed analog-to-digital and digital-to-analog converters and optical communication systems. In the last two decades, integrated filters in the Multi-GHz range have been implemented using III-V or SiGe technologies. In all cases in which the size of passive components is a concern, inductorless designs are preferred. Furthermore, due to the recent development of high-speed and high-resolution data converters, highly linear multi-GHz filters are required more and more. Classical open loop topologies are not able to achieve high linearity, and closed loop filters are preferred in all applications where linearity is a key requirement. In this work, we present a fully differential BiCMOS implementation of the classical Sallen Key filter, which is able to operate up to about 10 GHz by exploiting both the bipolar and MOS transistors of a commercial 55-nm BiCMOS technology. The layout of the biquad filter has been implemented, and the results of post-layout simulations are reported. The biquad stage exhibits excellent SFDR (64 dB) and dynamic range (about 50 dB) due to the closed loop operation, and good power efficiency (0.94 pW/Hz/pole) with respect to comparable active inductorless lowpass filters reported in the literature. Moreover, unlike other filters, it exploits the different active devices offered by commercial SiGe BiCMOS technologies. Parametric and Monte Carlo simulations are also included to assess the robustness of the proposed biquad filter against PVT and mismatch variations.

The design of active filters ( $e$ . g. Sallen-Key filter, voltage-controlled voltage-source (VCVS) topology or multiple feedbacks filter) is well known, but the resulted filter parameters: corner frequency, damping coefficient, gain, etc., depend on 4 or 5 component parametric dispersion. This paper presents a case study: the tuning method of a 4th order Butterworth band pass filter build with two VCVS active filters. This filter is used in the measuring chain of the signal conditioner of the linear inductive position sensor (LIPS).

This work introduces a Sallen key third order Lowpass filter in the fractional domain. The impact of fractional order capacitor (FOC) on the frequency response is presented. Present work uses three FOCs of same order. MATLAB and PSPICE simulations of the fractional lowpass filter of order 1.8, 2.4 and 3 are presented. For PSPICE simulations the FOCs are realized by Fourth-order approximation ladder network using continued fraction expansion method. Presented simulation results prove that the fractional order filter performs better as compared to integer order due to extra degree of freedom.

Early heart disease detection could be vital and some other diagnostic ways are being developed. In this paper, a lowcost tool for a diagnostic that analyzes the digitized heartbeat sound is given. This can be used to detect heart anomalies. The instrument shows the heart sound and also keeps a patient's long-term record for future use. The signal from the heart provides a lot of knowledge about the heart and offers an initial diagnosis recommendation. The electronic stethoscope uses the condenser microphone, preamplifier circuit, and filter circuit. The optimum filter is Butterworth with a fourth-order Sallen key low pass filter topology with a gain of 0.707 volts, -3.01 dB, and a fourth-order high pass filter with a gain of 0.782 volts, -2.137 dB. The frequency of the heart sound is about 20 Hz – 120 Hz in general. Therefore, the lower cutoff frequency of the filter is set to 20 Hz, while the higher cutoff frequency set to 120 Hz. The evaluation used to measure the performance of an electronic stethoscope is to compare with a conventional stethoscope, the recorded sound is the same.

The paper describes a method of azimuth acoustic correction of an inclinometer for oil and gas wells in high-latitude areas where usual gyroscopic and ferromagnetic sensors are inefficient because of significant errors. An embodiment of the method and options for units are presented. The focus is on a scheme of acoustic receiver unit of the system and it main functions such as downhole acoustic signal recording and data transmitting from downhole to wellhead. A comparison of analog and digital variants for data transmission is presented and justification for selecting the analog variant as preferable is given. The electronic scheme of the receiver unit as the preferable variant is described and estimates of operability of the unit are given.

This paper presents active low pass RC and switched capacitor filters with only N-type transistors. Two different high-gain OpAmp configurations with positive feedback are explored in this paper: One circuit based on cascaded inverters and the other based on capacitor bootstrapping. While the cascaded inverter configuration gives a gain of more than 50 dB and bandwidth of 48 MHz with 210 μw of power consumption, OpAmp with capacitor bootstrapping gives a gain around 40 dB and bandwidth of 2 MHz consuming 70 μw power. Circuit simulations were carried out in standard 180 nm technology. With these OpAmps, RC and SC filter implementations are presented. SC filter using OpAmp with cascaded inverter gives a THD of 5.36 % with 946.6 μw of power consumption, while SC filter with capacitive bootstrapped OpAmp give THD of 7.47 % with 351.7 μw of power consumption

A novel reconfigurable lowpass-polyphase biquad filter based on MFB structure is proposed in this paper. In this biquad, only one op-amp is adopted which improves the matching and reduces the power consumption. And its transmission function is synthesized by the complex signal flow graph. Then a 3rd order filter used in Zigbee transceiver is implemented to illustrate the technique, which is realized in 0.13 μm CMOS technology. To avoid the variation of resistance and capacitance, an on-chip tuning scheme is integrated. The test results show that when in polyphase mode, it is centered at 2 MHz with 3 MHz bandwidth and the image rejection is about 23 dB with the voltage gain of 12 dB. When in lowpass mode, the cut-off frequency is 1.5 MHz, and the DC gain is 12 dB. The in-band 3rd order input intercept point (IIP3) is 9 dBm in polyphase mode and 13 dBm in lowpass mode. Attractively, the filter only consumes 2.3 mA with a 1.2 V power supply, and occupies an area of 0.26 mm2.

In this paper, we provide a new third-order bandstop filter (BSF) topology with attenuation control capability. The proposed BSF topology contains inter-resonator coupling structures and it can duplicate the frequency responses of the conventional BSF topology, which does not have inter-resonator couplings. In addition, the proposed topology can control the attenuation level by adjusting the resonant frequency of each resonator, and this characteristic cannot be obtained from the conventional one. Two BSFs utilizing the conventional and proposed topologies are designed, fabricated, and measured to support the presented theory. Two filters have been designed and fabricated employing frequency tunable substrate integrated cavity resonators. The measurement verifies that the BSF utilizing the presented topology is capable of adjusting the attenuation level as well as reproducing the conventional bandstop responses.

This paper presents the analysis for allocating the system poles and hence controlling the system stability for KHN and Sallen---Key fractional order filters. The stability analysis and stability contours for two different fractional order transfer functions with two different fractional order elements are presented. The effect of the transfer function parameters on the singularities of the system is demonstrated where the number of poles becomes dependent on the transfer function parameters as well as the fractional orders. Numerical, circuit simulation, and experimental work are used in the design to test the proposed stability contours.

A quasi-elliptic function bandpass filter (BPF) based on parallel feed topology is presented. The parallel feed topology is realised by splitting the input/output port of the filter into two paths through a T-junction to excite a pair of resonators simultaneously. This configuration contributes to further improving the selectivity of the filter by introducing more transmission zeros (TZs) near the passband. In addition, a defected microstrip structure is utilised to enhance the out-band attenuation and spur suppression. In order to verify the proposed topology, a fourth order BPF with cross-coupling is designed, fabricated and measured. The measured frequency responses agree well with simulated ones. Four TZs can be obtained with two TZs on each side of the passband.

In this letter, a novel direct coupling matrix synthesis approach is proposed for the narrowband mixed topology filter (i.e., the filter structure part with extracted-pole and part with cross-coupled configurations). First, canonical coupling matrix for the filter is constructed based on a set of new characteristic polynomials with complex coefficients to generate extracted-pole sections at the source and load directly. Then, a specific matrix rotation sequence is introduced to reduce the filter to a more practical N-tuplets & extracted-pole mixed topology. For validation purposes, two illustrative examples are given. As the synthesis is done by a simpler coupling matrix process, the presented approach provides a more convenient solution for synthesizing mixed topology filters with terminal extracted-pole sections.

Electrical Impedance Tomography (EIT) is an imaging technique for mapping the conductivity distribution of an object. One of the most significant circuit blocks in the EIT system is Voltage Controlled Current Source (VCCS) circuit. The VCCS should be able to supply a current ranging from 0.5 to 5 mA at 10 kHz–1 MHz and should be adequate to support the load at the range of 100 Ohm–10 kOhm. The main purpose of this study is to design the VCCS with a constant current of 1 mA at 20 kHz. We designed four types of VCCS by using two types of voltage-controlled oscillator (VCO) circuits, two types of voltage to current converter (VCC) circuits, and a fourth order Butterworth Bandpass Filter (BPF) circuit (Sallen-Key topology). The VCO circuit was designed with two types of Integrated Circuits (IC) which are XR2206 (VCO 1) and AD9850 (VCO 2), whereas the VCC circuit was fabricated based on Enhanced Howland (EH) circuit (VCC 1) and Triple Op-Amp circuit (TOA) (VCC 2). The results show that VCCS 4 which was designed with the combination of VCO 2, VCC 2, and BPF gave the best performance compared to the three other types of VCCS circuit. The VCCS 4 is capable of delivering a constant current for 1 mA at 20 kHz with a load value of up to 3.72 kOhm. However, the four VCCS types that have been designed could be used as a current source in the EIT system for a single frequency.