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Design of Constant Phase Elements for Adjustable Pseudocapacitance by a Single Driving Voltage Using Integrated Unipolar Transistor Fields
(2026-01-01)
Sotner, Roman
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Litovska, Anna
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Polak, Ladislav
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Jerabek, Jan
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Kledrowetz, Vilem
This paper presents the design of a passive fractional-order element with tunable pseudocapacitance, enabling adaptable circuit behavior without additional power consumption. This is an important feature for modelling and characterization in natural systems, as well as in the field of electrical and electronic engineering, particularly for the design of instrumentation and sensing systems. The proposed topologies are based on integrated unipolar transistor arrays. Two implementations are demonstrated, with fractional orders of 0.22 and 0.5, offering pseudocapacitance adjustment ranges from 65 to 1 670 mikroF/s^0.78 and from 6.7 to 51 mikroF/s^0.5, respectively. Tuning is achieved through a DC bias voltage ranging from 0.8 to 10 V. The devices operate across nearly two decades of frequency, from approximately 100 Hz to 200 kHz, and support signal amplitudes in the hundreds of millivolts. Two application examples highlight their potential: electronic tuning of the center frequency in a fractional-order band-pass filter, and adjustment of the oscillation frequency in a fractional-order oscillator with a fixed 22.5 degrees phase shift between output waves. All concepts and results are experimentally validated in the laboratory.
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Compact active analog device for novel applications useful for sensing and measurement
(2024-08-01)
Sotner, Roman
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Jerabek, Jan
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Polak, Ladislav
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Jaikla, Winai
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Andriukaitis, Darius
The presented research introduces a novel approach to modern modular active device and provides various practical application examples tailored for industrial sensing readouts. Straightforward implementation of single active device-based topologies in frequency bands from kHz up to MHz is presented. These applications include: an electronically linearly tunable special band-pass filter that can be easily modified into a voltage-controlled oscillator, a two-port quadratic transformer, an amplitude modulator, and an equalization circuit (which serves as a fractional-order differentiator and integrator). These circuits benefit from high-impedance voltage input and low-impedance output (easily matched to 50 Ω), high processed signal levels (often reaching hundreds of mV), and simplified topologies without redundant passive elements. These features are especially valuable in tunable and configurable solutions for modern communication, sensing, audio, and consumer electronic systems, as well as in modeling various physical and biological systems. The experiments have been provided by simulations and measurements using device VCA824.
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Special Transfer Section for Selective Rejecting and Amplification of Bands in Equalization
(2024-01-01)
Sotner, Roman
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Svoboda, Marek
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Semenov, Dmitrii
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Polak, Ladislav
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Jerabek, Jan
This paper introduces a novel and simple filtering topology for band-reject (notch) and inverse band-reject applications, utilizing two voltage-adjustable operational transconductance amplifiers. The utilization of these active devices enables the implementation of identical topologies for both band-reject and inverse band-reject transfer functions. The resulting responses are harnessed for the cascade synthesis of a specialized comb filter, capable of amplification or attenuating/rejecting specific bands shown on three sub-bands. Both the design of individual sections and the entire cascade have been experimentally verified using active devices manufactured in the TSMC 180 nm CMOS process. Measurements conducted over a range from 10 Hz to 100 kHz demonstrate the importance of the selective filtering, which is significant for various applications, particularly in acoustic, vibration, and magnetic sensing readouts. The example of peaking suppression in magnitude response of emulated environment (acoustic coupling of piezo and microphone) is shown.
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Design of Phase-Locked Loop Using Special Analog Multipliers and Voltage Buffers: Demodulation of Transposed Signals from Sensors
(2024-01-01)
Svoboda, Marek
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Sotner, Roman
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Polak, Ladislav
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Jerabek, Jan
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Jaikla, Winai
Phase-locked loops (PLLs) are versatile electronic circuits that, among others, are used in various sensor applications (e.g., medical) for their ability to generate stable and precise clock signals. This article introduces a novel PLL-based frequency demodulation system designed for processing of very slow signals, ranging from a few Hz to several hundreds of Hz, with amplitudes in the order of several hundreds of millivolts. The system incorporates specialized analog multipliers tailored for essential PLL components, including the voltage-controlled oscillator, phase detector, loop filter with variable DC offset, and baseband filter, all optimized for the purpose of frequency demodulation. These multipliers were fabricated using the TSMC 0.18~μ m, 1.8 V CMOS process. The primary design objectives are simplicity, reduced complexity, low power consumption (merely 15 mW), and versatility for applications in sensing engineering. To validate the functionality of the proposed PLL system under practical conditions, we present an example of electrocardiogram and photoplethysmogram signal demodulation, demonstrating its operational performance.
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Arbitrarily Tunable Phase Shift in Low-Frequency Multiphase Oscillator
(2023-01-01)
Sotner, Roman
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Polak, Ladislav
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Jerabek, Jan
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Jaikla, Winai
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° and around -180°, -135°, and -90°. 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 ~μ m I3T25 ON Semiconductor 3.3 V CMOS process are used in experimental verification.
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Short range electromagnetic interface using 0.35 μm CMOS blocks for temperature monitoring in isolated areas
(2022-11-01)
Sotner, Roman
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Jerabek, Jan
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Polak, Ladislav
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Prokop, Roman
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Ayten, Umut Engin
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 μm 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, the presented system brings beneficial performances for similar applications targeting on monitoring of low-frequency or slowly varying signals.
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Readout for simple and precise analog acoustic impact initialization
(2021-12-01)
Sotner, Roman
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Polak, Ladislav
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Jerabek, Jan
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Lahiri, Abhirup
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Jaikla, Winai
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 μs 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.
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A Single Parameter Voltage Adjustable Immittance Topology for Integer- And Fractional-Order Design Using Modular Active CMOS Devices
(2021-01-01)
Sotner, Roman
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Jerabek, Jan
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Polak, Ladislav
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Prokop, Roman
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Jaikla, Winai
A simple single parameter adjustable immittance concept designed with modular active devices, fabricated in I3T $25~0.35~\mu \text{m}$ 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 $8.8~\mu \text{F}$ /seĉ1- $\alpha $ , where $\alpha $ 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 $700~\mu \text{S}$ 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.
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Integer- And fractional-order VCO using non-inertial amplitude stabilization and modern active elements
(2020-04-28)
Sotner, Roman
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Petrzela, Jiri
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Jerabek, Jan
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Langhammer, Lukas
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Polak, Josef
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.
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Illuminance sensing in agriculture applications based on infra-red short-range compact transmitter using 0.35 μm CMOS active device
(2020-01-01)
Sotner, Roman
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Jerabek, Jan
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Polak, Ladislav
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Petrzela, Jiri
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Jaikla, Winai
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 C035~0.35μm 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.

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