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The research presented in this article draws inspiration from previous efforts aimed at replicating the functions of various solid-state memristors using a variety of materials. The memristor circuit emulator serves as a cost-effective tool for circuit designers, enabling them to experiment with the diverse electrical characteristics of corresponding solid-state memristors. This article specifically focuses on the circuit-based emulation of silicon nanowire (SiNW) known for its effectiveness in biosensing applications. First, a fully floating memristor emulator has been presented based on a voltage differencing current conveyor (VDCC) and an operational transconductance amplifier (OTA)-controlled resistor, along with a grounded capacitance. Furthermore, the proposed memristor emulator was realized by employing integrated cells based on the discussed technology, and the simulation/experimental results are presented and analyzed. The experiments also confirmed the nonvolatile behavior of the realized memristor. The results demonstrate that the real-time implementation of the proposed emulator can accurately generate hysteretic behavior in both incremental and decremental memristive mode. Finally, the incremental and decremental pinched hysteresis loop (PHL) responses generated by the proposed emulator have been utilized to replicate the various types of memristive responses offered by SiNW by adding a simple extension to the circuit.

In the evolving landscape of Industry 4.0, the integration of advanced wireless technologies into manufacturing processes holds the promise of unprecedented connectivity and efficiency. In particular, the data transmission in a heavy industry environment needs stable connectivity with mobile operators. This paper deals with the performance study of 4G and 5G mobile signal coverage within a complex factory environment. For this purpose, a cost-effective and portable measurement setup was realized and used to provide long-term measurement campaigns monitoring and recording several key parameter indicators (KPIs) in 4G/5G downlink and upload. To support the reproducibility of the provided study and other research activities, the measured dataset is publicly available for download. Among others findings, the obtained results show how the performance of 4G/5G is influenced by a heavy industry environment and of the time of day on the network load., In the evolving landscape of Industry 4.0, the integration of advanced wireless technologies into manufacturing processes holds the promise of unprecedented connectivity and efficiency. In particular, the data transmission in a heavy industry environment needs stable connectivity with mobile operators. This paper deals with the performance study of 4G and 5G mobile signal coverage within a complex factory environment. For this purpose, a cost-effective and portable measurement setup was realized and used to provide long-term measurement campaigns monitoring and recording several key parameter indicators (KPIs) in 4G/5G downlink and upload. To support the reproducibility of the provided study and other research activities, the measured dataset is publicly available for download. Among others findings, the obtained results show how the performance of 4G/5G is influenced by a heavy industry environment and of the time of day on the network load.

The paper introduces a novel design solution of a reconnection-less reconfigurable filter based on the method of unknown nodal voltages (MUNV). The filter offers all standard 2nd-order transfer functions and the electronic adjustment of the pole frequency and quality factor, which are mutually independent. The introduced design brings following advantages in comparison to other relevant solutions (MUNV-based reconnection-less reconfigurable filters): a) it consists of four independent nodes which brings the advantage of both working capacitors being grounded as floating capacitors can cause unpredictable parasitic behavior, b) the additional adjustment of the quality factor, c) the additional adjustment of the pass-band at lower and higher frequencies. Simulations and experimental measurements were carried out in order to verify the proposed design.

Active root mean square (RMS) diode-less detectors are common analog blocks suitable for various signal processing and communication applications. This brief introduces a new and simple type of this detector suitable for high-speed applications up to several tens of MHz. The circuit was designed with special analog multipliers (MLTs) fabricated in 0.18 mu m CMOS process having power consumption 3.5 mW only at supply voltage 1.8 V. It actually utilizes two MLTs and one external grounded capacitor. The operationability of the RMS detector was verified by a set of experimental measurements and the obtained features were compared with recent solutions including also peak detectors. For this purpose, signals with various waveforms and amplitudes in a range from 5 mV up to 500 mV were used. Good correspondence between theory and real measurements were observed for signals with frequency up to 40 MHz.

The growing population and lack of change in resources of cultivated land have led to the search for more efficient farming solutions. The recovery of soil is facilitated by using chemicals designed for the enrichment of cultivated soil. Fertilisers are made of a combination of various substances that determine not only the chemical but also the shape characteristics of the fertiliser pellets. The effect of the quality of fertilisation on yield size is related to even distribution. Shape and size are closely related to the quality of the fertilisation process. The intense control of the production process would not be possible without automatised and quick measurements within the production line. Constant control is necessary to ensure that the products meet quality standards. The contactless assessment of pellet sizes allows a quick reaction to changes in production quality and reduces the costs arising from the reprocessing of defective pellets. The results of the assessment of pellet volume using their two-dimensional image are presented in this publication. Pellets must be analysed according to their most characteristic position, which can provide valuable information about their properties. The aim is to determine the placement positions of the equipment based on calculations and to compare the results with those of gold-standard equipment. Correctly calibrated equipment ensures that the measurement results match the results of the control equipment of fertiliser producers. Reliable non-contact measurements can reduce the reaction time to production changes.

A design of a low pass frequency filter with the electronic change of the approximation characteristics of resulting responses is presented. The filter also offers the reconnection–less reconfiguration of the order (1st, 2nd, 3rd and 4th order functions are available). Furthermore, the filter offers the electronic control of the cut–off frequency of the output response. The feature of the electronic change of the approximation characteristics has been investigated for Butterworth, Bessel, Cauer, Chebyshev and Inverse Chebyshev approximations. The design is verified by PSpice simulations and experimental measurements. The results are also supported by the transient domain response (response to the square waveform), comparison of group delay, sensitivity analysis and implementation feasibility based on given approximation. The benefit of the proposed electronic change of the approximation characteristics feature (in general signal processing or for sensors in particular) has been presented and discussed for an exemplary scenario.

A special electronically tunable multiphase oscillator with arbitrarily and continuously adjustable phase shifts is introduced. Our design assumes to set the phase around the asymptotical limit of 180.. These features cannot be easily achieved in a standard way, i.e., any simple single-phase oscillator supplemented by a first-order adjustable all-pass (AP) section (shifter). The proposed design uses an electronically linearly tunable quadrature oscillator with a frequency range from 0.98 up to 12.54 kHz. It also offers multiples of 45. as the initial setting of the phase shift tuning region. The example of operation shows the adjustment of the phase shift at a specific frequency (10 kHz) within the range of +/- 45 degrees. and around -180 degrees, -135 degrees, and -90 degrees. This variability is not available in standard cases without the use of several AP sections. The current value of the phase shift of the presented oscillator is electronically controlled and does not influence the oscillation frequency and condition of oscillation. Output levels of produced signals are not influenced by this tuning process and are in the range of several hundreds of mV. Two applications of the oscillator are proposed. The first one focuses on low-bitrate modulation systems [phase shift keying (PSK)] while in the second one, our circuit represents a source of phase-adjustable signals in acoustic experiments. Discrete passive elements and active devices (special multipliers having current output terminals, unity-gain differential voltage buffers) fabricated in 0.35 mu m I3T25 ON Semiconductor 3.3 V CMOS process are used in experimental verification.

Methods for identifying contaminants in liquids (such as wine) typically require laboratory analyses of samples using precision equipment, which is expensive in terms of both time and required resources. Therefore, there is a need to identify alternative measurement approaches to reduce the cost in terms of equipment, personnel, and time. One sensing approach to characterize liquid properties and potentially identify contaminants is electrical impedance spectroscopy (EIS). In this work, the electrical impedance of 25-mL samples of three solutions with alcohol (plum distillate, isopropyl alcohol, and winter windshield solution) and a control sample of distilled water were measured using a Keysight 4294A. The liquids with alcohol content (plum distillate, isopropyl alcohol, and winter windshield solution) have lower impedance magnitude in the frequency band below 100 kHz, with specific values of 139, 76, and 7 k at 40 Hz, compared to the reference distilled water sample (approximately 315 k ). This suggests that solutions with alcohol (and other chemicals) have increased conductivity in comparison to the distilled water and that impedance may be a suitable approach to differentiate liquids with and without contaminants.

alternative method for synthesising the sinusoidal oscillator based on series negative resistance capacitance is presented in this paper. The proposed topology is constructed with the series negative resistance-capacitance circuit connected in parallel with a grounded resistor and capacitor. To validate the proposed method, a new grounded series negative resistance-capacitance simulator is also proposed as a subcircuit for synthesising the sinusoidal oscillator. The series negative resistance-capacitance simulator is based on a commercially available integrated circuit (IC), LT1228. The equivalent negative resistance and equivalent negative capacitance can be adjusted electronically using an external DC bias current. The sinusoidal oscillator that is synthesised using the proposed method consists of a single LT1228, two capacitors, and three resistors. The frequency and the condition of the oscillation are orthogonally adjusted. Also, the condition of oscillation is electronically controlled. The amplitude of the sinusoidal waveform is adjustable. In addition, the output voltage node of the proposed oscillator has a low impedance, which allows it to connect to other circuits without using an additional buffer. Both PSPICE simulation and experiment are used to validate the proposed circuits.

This work presents a novel methodology to adjust the inductance of real coils (electronically) and to cancel out serial losses (up to tens or even hundreds of Ohms in practice) electronically. This is important in various fields of electromagnetic sensors (inductive sensors), energy harvesting, measurement and especially in the instrumentation of various devices. State-of-the-art methods do not solve the problem of cancellation of real serial resistance, which is the most important parasitic feature in low- and middle-frequency bands. In this case, the employment of serial negative resistance is not possible due to stability issues. To solve this issue, two solutions allowing the cancellation of serial resistance by the value of the passive element and an electronically adjustable parameter are introduced. The operational ranges are between 0.1 and 1 mH and 0.1 and 10 mH, valid in bandwidths from hundreds of Hz up to hundreds of kHz. The proposed concepts are experimentally tested in two applications: an electronically tunable oscillator of LC type and an electronically tunable band-pass RLC filter. The presented methodology offers significant improvements in the process of circuit design employing inductors and can be beneficially used for on-chip design, where serial resistance issues can be very significant.

Introduction: Infra-red (IR) and visible light (VL) based systems developed for transmission of information about physical quantities (e.g. humidity, temperature) out from closed areas, cannot be effectively employed in case of specific conditions in a targeted environment (because of fog or vapor for example). Objectives: In this work, we introduce a concept of wireless short-range transmitter and receiver to sense physical quantities, for instance temperature, with slow variation. The proposed concept is able to transmit analog-based information from isolated environments (e.g. aquariums or environments for plant growing) with high immunity against vapor and fog that limits standard optical (laser, IR band) methods of communication. Methods: In this work, a new concept of short range radiofrequency (RF) communication device consisting of transmitting and receiving parts build from active devices fabricated in 0.35 m I3T25 3.3 V CMOS process and ferrite antennas is selected. RF part uses medium-wave propagation within 10 mm distance at frequency 700 kHz. Such an approach offers minimal path loss of the radiated energy of a signal and low-gain amplification required for restoration of similar levels as available at the transmitting side. Results: The processing of base-band signals of simple (sine wave) and complex (electrocardiogram) character was verified experimentally through the system. Application example of temperature monitoring in a closed environment, based on a temperature sensor (thermistor), verifies operationability in temperature range from 10 °C up to 50 °C. Conclusion: Compared to state-of-the-art solution, the presented concept has several advantages, for instance: less complexity; using of simpler type of modulation and demodulation; lower power consumption and significantly reduced issues caused by an environment with special transmission conditions (e.g. fog and vapor). The obtained results are in good agreement with expectations. Among others

A detailed analysis of an operational transconductance amplifier based gyrator implementing a fractional-order inductance simulator is presented. The influence of active element non-ideal properties on the gyrator operation is investigated and demonstrated by admittance characteristics and formulas for important values and cut-off frequencies in these characteristics. Recommendations to optimize the performance of the gyrator in terms of operation bandwidth, range of obtainable admittance magnitude, and signal dynamic range are proposed. The theoretical observations are verified by PSpice simulations of the gyrator with LT1228 integrated circuit.

An economic concept of acoustic shock wave sensing readout system for simple computer processing is introduced in this work. Its application can be found in precise initialization of the stopwatch from the starter sound, handclap or gun in competitive sport races but also in many other places. The proposed device consists of several low-cost commercially available components and it is powered by a 9 V battery. The proposed device reliably reacts on incoming acoustic shock wave by generation of explicit impulse having controllable duration. It significantly overcomes basic implementations using only a microphone and amplifier (generating parasitic burst instead of defined and distinct impulse) or systems allowing a limited number of adjustable features (gain and/or threshold of the comparator-our concept offers the adjustment of gain, cut-off frequency, threshold level and time duration of active state). In comparison with standard methods, the proposed approach simplifies and makes sensing device less expensive and universal for any powder-based starting gun (without necessity to adapt starting gun). The proposed device, among others, has the following features: impulse duration can be controlled from hundreds of mu s up to 2.3 s, the gain range of linear part of processing from 6 to 40 dB and open-collector output compatible with 5 V TTL or 3.3 V CMOS logic. The initialization has been tested in the range from tens of centimeters up to four meters. In order to highlight the important spectral components, the spectral character of the signal can be optimally reduced by a low-pass filter. The quiescent power consumption of the designed simple analog circuit reaches 90 mW. Several use cases, response of the designed system on gunshot signature, talking, hand-clapping and hit on the sensing microphone, are studied and compared to each other. Simulation and experimental results confirm functionality of the realized system.

A simple single parameter adjustable immittance concept designed with modular active devices, fabricated in I3T 25 0.35 um 3.3 V CMOS process of ON Semiconductor, is introduced. The proposed devices employ an integer-order capacitor and specifically designed fractional-order capacitors (sometimes called constant phase elements). The proposed active topology consists of two simple active elements, namely a linearly voltage adjustable operational transconductance amplifier and a voltage differencing unity gain voltage follower/buffer, and only two passive elements, i.e. redundancy is minimized. The designed topology offers generation of an adjustable immittance having both the capacitive and inductive character. The importance of the order as well as the value of the pseudo-capacitance for design and analyzes are shown, including all important parasitic features for estimation of expected operational bandwidth which have to be considered in the design. The operational bandwidth is determined by high values of approximants of fractional-order capacities (225, 56 and 8.8 uF /sec^1- a , where represents the order equal to 0.25, 0.5 and 0.75, respectively). These parameters result into ranges between tens of Hz and units-tens of kHz. The adjustability of the transconductance from 70 to 700 S by the driving voltage between 0.05 and 0.5 V offers approximately one decade change of equivalent capacitance and inductance. Laboratory-based experiments done with a fabricated prototype confirmed the theoretical presumptions.

A design of a fractional-order (FO) integrator is introduced for operation of resulting solution in the current mode (CM). The solution of the integrator is based on the utilization of RC structures, but in comparison to other RC structure based FO designs, the proposed integrator offers the electronic control of the order. Moreover, the control of the proposed integrator does not require multiple specific and accurate values of the control voltages/currents in comparison to the topologies based on the approximation of the FO Laplacian operator. The electronic control of a gain level (gain adjustment) of the proposed integrator is available. The paper offers the results of Cadence IC6 (spectre) simulations and more importantly experimental measurements to support the presented design. The proposed integrator can be used to build various FO circuits as demonstrated by the utilization of the integrator into a structure of a frequency filter in order to provide FO characteristics.

A novel electronically reconfigurable fractional-order filter allowing independent electronic frequency tuning and switchless change of the transfer response by a single parameter between standard band-pass, inverting all-pass response and special type band-reject response is presented in this work. The differences between these special transfer characteristics and standard features consist in magnitude and phase response behavior. Inverting amplification or attenuation is also available. The filter has tested frequency range between 1 Hz and 100 kHz. The proposed fractional-order filter (using two fractional-order element having equivalent capacity 8.7 uF/sec^1/4, =3 /4) tunability yields one-decade range approximately between 10 Hz and 100 Hz by transconductance between 0.19 and 1.1 mS (fractional-order design helps with reduction of driving force less than one decade). The application example in frequency/phase detector (operationability around center frequency 100 Hz - between 50 and 180 Hz) and further signaling frequency detecting system for frequency shift keying demodulator offers maximal detectable voltage (about 300 mV) for alignment (zero phase shift) of the signals of the same frequency (center frequency of the proposed filter in inverting all-pass mode). It also offers an interesting application in frequency shift keying demodulation process (or for identification/signalization purposes of certain frequencies) by usage of a simple additional comparator generating clear output state. Cadence simulations as well as experimental tests using integrated cells of special multipliers fabricated in ON Semiconductor 0.35 m I3T25 CMOS process confirm operationability of the proposed concept as well as simple application of special response of the filter for phase/frequency detection and demodulation purposes.

This paper presents the design of a voltage-mode three-input single-output multifunction first-order filter employing commercially available LT1228 IC for easy verification of the proposed circuit by laboratory measurements. The proposed filter is very simple, consisting of a single LT1228 as an active device with two resistors and one capacitor. The output voltage node is low impedance, resulting in an easy cascade-ability with other voltage-mode configurations. The proposed filter provides four filter responses: low-pass filter (LP), high-pass filter (HP), inverting all-pass filter (AP-), and non-inverting all-pass filter (AP+) in the same circuit configuration. The selection of output filter responses can be conducted without additional inverting or double gains, which is easy to be controlled by the digital method. The control of pole frequency and phase response can be conducted electronically through the bias current (I-B). The matching condition during tuning the phase response with constant voltage gain is not required. Moreover, the pass-band voltage gain of the LP and HP functions can be controlled by adjusting the value of resistors without affecting the pole frequency and phase response. Additionally, the phase responses of the AP filters can be selected as both lagging or leading phase responses. The parasitic effects on the filtering performances were also analyzed and studied. The performances of the proposed filter were simulated and experimented with a & PLUSMN;5 V voltage supply. For the AP+ experimental result, the leading phase response for 1 kHz to 1 MHz frequency changed from 180 to 0 degrees. For the AP- experimental result, the lagging phase response for 1 kHz to 1 MHz frequency changed from 0 to -180 degrees. The design of the quadrature oscillator based on the proposed first-order filter is also included as an application example.

This work deals with the design of a simple double output voltage phase detector, using a specific type of analog multiplier, and its application in a frequency demodulator. The design of active parts was performed in Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 mu m 1.8 V CMOS technology. The intention is devoted to design the circuitry in such a way to avoid low-frequency signal processing with large values of capacities that are not available in case of on-chip implementation. The idea consists in the processing of significantly faster signal (tens of kHz) carrying modulated low frequency information. Then the coupling capacity may have significantly smaller value. The operation of the demodulator was tested for carrier frequency 50 kHz and for modulation signal with frequency of 10 Hz and 500 Hz. Differences of these frequencies approximately determine the values of capacitors required for AC coupling. Simulations (Cadence Spectre simulator) as well as experimental measurement, using fabricated ASIC prototypes, are provided to verify the proposed circuits in both the time and frequency domain.

The Second Generation Digital Video Broadcasting Terrestrial (DVB-T2) standard and its light version (DVB-T2-Lite) offer very flexible system configurations including multiple-input single-output (MISO) transmission technology to improve the performance of the Single Frequency Networks (SFNs). In this paper, a measurement-based study of the DVB-T2/T2-Lite MISO performance under different mobile and portable transmission scenarios is presented. The outputs of the study, evaluated by both objective and subjective ways, show that the influence of different mobile and portable transmission conditions on the performance of DVB-T2/T2-Lite MISO broadcasting is not negligible.

Growing population and decreasing amount of cultivated land conditions the increase of fertilizer demand. With the advancements of computerized equipment, more complex methods can be used for solving complex mathematical problems. In the fertilizer industry, the granulometric composition of products matters as much as the quality of production of chemical composition products. The shape and size of pellets determines their distribution over cultivated land areas. The effective distance of field spreading is directly related to the size and shape parameters of a pellet. Therefore, the monitoring of production in production lines is essential. The standard direct methods of the monitoring and control of granulometric composition requires too much time and human resources. These factors can be eliminated by using imaging measuring methods that have a variety of benefits, but require additional research in order to assure and determine the compliance of real-time results with results of the control equipment. One of the fastest, most flexible and largest amount of data providing methods is the processing and analysis of digital images. However, then we face the issue of the suitability of 2D images to be used for the evaluation of granulometric compositions, where processing of digital images provides only two dimensions of a pellet: length and width. This study proposes a method of evaluating an irregular pellet. After experimental research we determined < 2% of discrepancy when compared to the real volume of a pellet.

This paper compares several ways of electronic resistance control for tunable applications (filters, oscillators, amplifiers, etc.). Simulation (PSpice) and experimental tests of basic J-FET transistor-based adjustable resistor, optocoupler as well as more advanced active solutions using active devices (variable gain amplifiers, voltage-mode multiplier) are performed in order to see available linear range, readjustability range and expected frequency features.

This paper aims to show an easy way how to design a reconnection-less reconfigurable filter based on the modification of an existing MISO filter. The proposed filter offers the same transfer functions as the structure before the modification and additionally offers function of the direct transfer and high-pass function with transfer zero. In comparison with the structure before the modification, the proposed filter provides the electronic control of its pole frequency and quality factor. The design is supported by simulations in Cadence IC6 (spectre).

This paper targets on the design and analysis of specific types of transfer functions obtained by the summing operation of integer-order and fractional-order two-port responses. Various operations provided by fractional-order, two-terminal devices have been studied recently. However, this topic needs to be further studied, and the topologies need to be analyzed in order to extend the state of the art. The studied topology utilizes the passive solution of a constant-phase element (with order equal to 0.5) implemented by parallel resistor-capacitor circuit (RC) sections operating as a fractional-order two-port. The integer-order part is implemented by operational amplifier-based lossless integrators and differentiators in branches with electronically adjustable gain, useful for time constant tuning. Four possible cases of the fractional-order and integer-order two-port interconnections are analyzed analytically, by PSpice simulations and also experimentally in the frequency range between 10 Hz and 1 MHz. Standard discrete active components are used in this design for laboratory verification. Practical recommendations for construction and also particular solutions overcoming possible issues with instability and DC offsets are also given. Experimental and simulated results are in good agreement with theory.

This paper introduces a novel electronic system for simplex low-bitrate infra-red (IR) communication applications. The transmitter is implemented completely by analog building blocks, formed with the help of a recently fabricated chip that includes active elements allowing various modular interconnections. For the design of this chip, the ON Semiconductor C035 0.35 mu m I3T25 technology was chosen due to the trade-off between cost, efficiency and obtainable parameters. The designed transmitter operates as a voltage-to-duty cycle converter, using pulse width modulation that causes ON/OFF keying of the carrier signal for infra-red (IR) diode. The duty cycle variable between 7% and 83% is modulated by the input voltage (in the range of +/- 0.8 V) of the transmitter. The use case of the proposed concept in the measurement of illuminance within the range of 30 lx and 550 lx is also presented. The quality of the transmission was evaluated as the error between the transmitted and received values of the duty cycle (kept mostly below 10 %). The maximal power consumption of the transmitter reaches 180 mW.

This paper introduces design of the linearly tunable quadrature voltage-controlled oscillator (VCO) using modern off-the-shelf active elements suitable for the design of electronically adjustable applications. The simplified topology was achieved using non-inertial stabilization of amplitude. It allows targeting adjustability of the oscillation frequency only into lossless integrator part of the topology. This arrangement simplifies the design and the tenability also. Derived symbolical expressions indicate that gain adjustment of used amplifiers (that are still in single path) does not influence amplitude and phase shift ratio of generated waveforms, which is a beneficial feature. The performances of the circuit are tested experimentally in band of units of MHz and results confirmed expected behavior. Initial study of the oscillator with fractional-order capacitors is presented and discussed. Results are supported by laboratory measurements.

This contribution presents a design of a current–mode fractional–order electronically controllable integrator which can be used as a building block for a design of fractional–order (FO) circuits. The design is based on a 2nd–order Follow–the–Leader–Feedback topology which is suitably approximated to operate as an integrator of a fractional order. The topology is based on Operational Transconductance Amplifiers (OTAs), Adjustable Current Amplifiers (ACAs) and Current Follower (CF). The proposed structure offers the ability of the electronic control of its fractional order and also the electronic control of the frequency band. Simulations in Cadence IC6 (spectre) and more importantly experimental measurements were carried out to support the proposal. If wider bandwidth where the approximation is valid is required, a higher order structure must be used as also shown in this paper by utilization of a 4th–order FLF topology.

This paper introduces a third-order reconnection-less electronically reconfigurable filter constructed of operational transconductance amplifiers (OTAs) and a current amplifier with individual gain control of its outputs. All capacitors in the filter structure are grounded. The filter offers thirteen transfer functions based on the configuration of current gains without a necessity of any manual reconnection or modification. The design is verified by PSpice simulations alongside with experimental measurements using available active elements.

This contribution introduces a new simple electronically adjustable resonator for implementation in design of the fractional-order multiphase oscillator created with parallel connection of this resonator and negative resistor. The circuit may operate in single-ended or differential/pseudo-differential mode using integer and fractional-order capacitor. Design example is provided for generation of signals with ideal phase shifts equal to 22.5, 157.5 and 180 degrees in the operating frequency band of 47 kHz – 275 kHz with simple tuning of a single parameter. The features of the circuit were verified by PSpice simulations using suitable models and building blocks. Results confirmed expected behavior

This paper presents a compact and simple design of adjustable triangular and square wave functional generators employing fundamental cells fabricated on a single integrated circuit (IC) package. Two solutions have electronically tunable repeating frequency. The linear adjustability of repeating frequency was verified in the range between 17 and 264 kHz. The main benefits of the proposed generator are the follows: A simple adjustment of the repeating frequency by DC bias current, Schmitt trigger (threshold voltages) setting by DC driving voltage, and output levels in hundreds of mV when the complementary metal-oxide semiconductor (CMOS) process with limited supply voltage levels is used. These generators are suitable to provide a simple conversion of illuminance to frequency of oscillation that can be employed for illuminance measurement and sensing in the agriculture applications. Experimental measurements proved that the proposed concept is usable for sensing of illuminance in the range from 1 up to 500 lx. The change of illuminance within this range causes driving of bias current between 21 and 52 mu A that adjusts repeating frequency between 70 and 154 kHz with an error up to 10% between the expected and real cases.

This paper presents a new concept of a capacitance multiplier using the topology of differential voltage buffer and current conveyor, where the capacitor is connected to the current input terminal. The presented topology overcomes the typical issue known from similar solutions, i.e. creation of an undesired lossy character of the impedance plot. The added feedback path in the structure serves for minimization of the serial parasitic resistance of the current input terminal as well as the output resistance of differential voltage buffer. The electronic driving of the current and voltage internal gains of the active elements allows the adjustment of the capacitance multiplication factor as well as readjustment of the overall capacitance structure between the lossy and lossless modes of operation. The adjustment of the multiplication factor intentionally targets low ranges of gains. Despite that the multiplication factor equals or is less than 1, the range of adjustability is very wide. Simple modifications of the proposed concept leading to the differential-mode operation and enhancement of the multiplication factor are shown and explored. They were experimentally tested in more than 2 decades, from 0.03 to 5.8 nF, and controlled by single DC voltage from 0.1 to 1.0 V. The outputs of experimental measurements meet with the PSpice simulations and confirm the design validity.

This paper introduces new promising applications of VCA822 active device in the fractional-order design of two-ports including very simple and compact solutions of integrator, differentiator, low-pass and high-pass filter. Key feature of the designed circuits is their tunability controlled by current gain of VCA822 not available in case of solution with standard op-amps. Block (principal) structure of the device is explained in detail. PSpice simulation results of the designed circuits indicate usability of these ideas and also simple tunability of the application verified with a fractional-order constant phase element with the order alpha = 1/4.

A novel solution of a reconnection-less reconfigurable filter is being presented. The filter works in the current mode, voltage mode and mixed mode (voltage to current) offering sixteen transfer functions in total. The structure utilizes a voltage differencing transconductance amplifier, current follower and voltage and current amplifiers. The designed structure offers the control of the pole frequency and quality factor and the adjustment of the band-stop/band-pass area of available functions. The proposed design is supported by the PSpice simulations using available simulation models.

This paper brings new approach for the design and construction of electronically adjustable immittance functions using single compact commercially available active device (VCAS22). Some of parameters of designed circuits can be controlled electronically thanks to type of used active device. Presented design uses RC approximants of fractionalorder element (order 1/4) in three application examples (fractional-order adjustable capacitance, inductance and frequency dependent negative resistor). PSpice simulations confirm expected behavior and tunability described by theoretical expressions (in wide band up to 10 MHz).