David Kubanek

Fractional-order filters based on low-voltage DDCCs

This paper presents the design and implementation of fractional-order filters based on promising CMOS structure of Differential Difference Current Conveyor (DDCC), which was designed and fabricated using the 0.35µm CMOS AMIS process. The derivation of the filters has been achieved using a second-order approximation of the corresponding fractional-order transfer functions. The filters offer the benefit of low-voltage (?500mV) operation as well as the requirement of grounded passive elements. In addition, a technique for the quick derivation of high-order filters has been introduced. The simulation and experimental results prove the attractive performances of the proposed filters.

High-Precision Differential-Input Buffered and External Transconductance Amplifier for Low-Voltage Low-Power Applications

Recently, the demand for low-voltage low-power integrated circuits design has grown dramatically. For battery-operated devices both the supply voltage and the power consumption have to be lowered in order to prolong the battery life. This paper presents an attractive approach to designing a low-voltage low-power high-precision differential-input buffered and external transconductance amplifier, DBeTA, based on the bulk-driven technique. The proposed DBeTA possesses rail-to-rail voltage swing capability at a low supply voltage of ±400 mV and consumes merely 62 μW. The proposed circuit is a universal active element that offers more freedom during the design of current-, voltage-, or mixed-mode applications. The proposed circuit is particularly interesting for biomedical applications requiring low-voltage low-power operation capability where the processing signal frequency is limited to a few kilohertz. An oscillator circuit employing a minimum number of active and passive components has been described in this paper as one of many possible applications. The circuit contains only a single active element DBeTA, two capacitors, and one resistor, which is very attractive for integrated circuit implementation. PSpice simulation results using the 0.18 μm CMOS technology from TSMC are included to prove the unique results.

Reconfigurable Fractional-Order Filter with Electronically Controllable Slope of Attenuation, Pole Frequency and Type of Approximation

This paper presents design of electronically reconfigurable fractional-order filter that is able to be configured to operate as fractional-order low-pass filter (FLPF) or fractional-order high-pass filter (FHPF). Its slope of attenuation between pass band and stop band, i.e., order of the filter, is electronically adjustable in the range between 1 and 2. Also, pole frequency can be electronically controlled independently with respect to other tuned parameters. Moreover, particular type of approximation can be also controlled electronically. This feature set is available both for FLPF and FHPF-type of response. Presented structure of the filter is based on well-known follow-the-leader feedback (FLF) topology adjusted in our case for utilization with just simple active elements operational transconductance amplifiers (OTAs) and adjustable current amplifiers (ACAs), both providing possibility to control its key parameter electronically. This paper explains how reconfigurable third-order FLF topology is used in order to approximate both FLPF and FHPF in concerned frequency band of interest. Design is supported by PSpice simulations for three particular values of order of the filter (1.25, 1.5, 1.75), for several values of pole frequency and for two particular types of approximation forming the shape of both the magnitude and phase response. Moreover, theoretical presumptions are successfully confirmed by laboratory measurements with prepared prototype based on behavioral modeling.

Passive fractional-order components based on resistive-capacitive circuits with distributed parameters

The paper deals with the analysis and mainly synthesis of passive fractional-order elements (FOEs). Pointing out the disadvantages of the most frequently used solutions, the utilization of resistive-capacitive circuits with distributed parameters for the design of FOEs is further discussed. This approach is based on creation of resistive, capacitive and conductive layers on a substrate. Examples of these devices along with simulation and measurement results are presented. A platform for analysis, synthesis and trimming of these components is also described, which allows to adjust required parameters of the elements after fabrication.

Universal voltage conveyors in fractional-order filter design

In this paper voltage-mode fractional-order low- and high-pass filters using universal voltage conveyors are presented. The assumed order of the filters is (1 + α), where 0 <; α <; 1. The proposed structures use the continued fraction expansion approach and hence the fractional-order transfer functions of the filters are approximated by integer-order functions. The proposed structures are easily cascadable since their output impedance is zero in theory. The performance of the filters has been verified by Spice simulations that show the proper behaviour of the proposed structures.

Classification of Digital Modulations Mainly Used in Mobile Radio Networks by means of Spectrogram Analysis

In this paper a new method of modulation classification is proposed. For the analysis, modulation signals and their spectrograms were obtained in the Matlab program. The classification method is based on spectrogram image recognition and it can discriminate between various digital signal modulations, such as FSK, BPSK, MSK, QPSK and QAM. The new method was tested using modulated signals corrupted by Gaussian noise, and it is well usable with signal-to-noise ratios as low as 10 dB.

Design and properties of fractional-order multifunction filter with DVCCs

Fractional-order filter employing two differential voltage current conveyors, four grounded passive elements, one of which has fractional-order impedance, is presented. The filter provides low-pass and band-pass transfer function simultaneously and its order can be set between one and two. Relations and recommendations for determining the passive element parameters are given. PSpice simulations confirm the theoretical expectations, show very good performance with AD844 amplifier as conveyor replacement, and discover the most critical parasitic properties of conveyors.

Current-Mode VHF high-quality analog filters suitable for spectral network analysis

In modern spectral network analysis a particular spectral component needs to be extracted precisely in order to measure electrical quantities on the physical level of data networks, e.g. IEEE 802.11, 802.16 etc. Due to these facts, high-speed analog filters with satisfactory features are required. A new active device, UCCX, is presented as suitable for VHF current-, voltage-, and mixed-mode applications. This device contains realization structures of one UCC element and one CCII+/- element. Using UCCX device special filters operating in the current mode are derived.

Signal processing for high-speed data communication using pure current mode filters

The paper deals with the novel filtration techniques for analog high-speed data signal preprocessing working on the base of a pure current mode filters. The paper describes a novel structure of the universal multifunction filter working in the pure current mode. Due to better frequency features of the current mode and a tendency to reduce the supply voltage because of the technology used (where in the voltage mode the dynamic range goes down in the voltage domain), we decided to design a universal filter working in exactly the pure current mode. It is a circuit where the active elements are only the current-controlled current sources. The current buffer with one input and one positive and one negative output appears to be the optimum element. The bipolar structure of such a current buffer is designed and the basic simulations are carried out.

Fractional-order low-pass filter with electronically adjustable parameters

This paper presents possible solution of fractional-order low-pass filter (FLPF) with electronically adjustable order between 1 and 2 and with also electronically adjustable pole frequency. It is based on well-known follow-the-leader feedback (FLF) topology adjusted in our case for utilization with operational transconductance amplifiers (OTAs) and adjustable current amplifiers (ACAs). This 3rd-order topology is used in order to approximate FLPF response in particular frequency band of interest. Design is supported by Pspice simulations for three particular values of order of the filter (1.3, 1.5, 1.7) and for several values of pole frequency.