Current-Controlled Current-Mode Universal Biquad Employing Multi-Output Transconductors

This paper deals with RC active biquad working in the so-called current mode (CM). The design approach uses only three transconductors (OTA) with the minimum necessary number of outputs and with only three passive grounded elements. The proposed filter has simple circuit configuration providing all standard transfer functions such as high-pass (HP), band-pass (BP), low-pass (LP), band-reject (BR) and all-pass (AP). Electronic tuning and independent adjusting of the quality factor and bandwidth of BP filter is possible. The presented circuits are verified by PSpice simulations utilizing OTAs on transistor level of abstraction. The linear parasitic effects of the real active elements in each suggested circuit are briefly discussed. Experimental verification is also given. Designed networks can be used in many applications such as antialiasing filters, in high-speed data telecommunication systems, for signal processing in the cable modems, in regulation and measurement techniques etc

Study of Adjustable Gains for Control of Oscillation Frequency and Oscillation Condition in 3R-2C Oscillator

An idea of adjustable gain in order to obtain controllable features is very useful for design of tuneable oscillators. Several active elements with adjustable properties (current and voltage gain) are discussed in this paper. Three modified oscillator conceptions that are quite simple, directly electronically adjustable, providing independent control of oscillation condition and frequency were designed. Positive and negative aspects of presented method of control are discussed. Expected assumptions of adjustability are verified experimentally on one of the presented solution

Current Gain Controlled CCTA and its Application in Quadrature Oscillator and Direct Frequency Modulator

A modified conception of adjustable current conveyor transconductance amplifier (CCTA) and its interesting application in simple quadrature oscillator expandable for direct frequency modulation purposes, employing only four grounded passive elements is presented in this paper. It is quite simple solution for modern communication subsystem components. An electronic adjusting of the oscillation frequency is easily possible and control of condition of the oscillation is realized via only one grounded resistor. The characteristic equation, condition of oscillation and major parasitic influences of real active part are discussed. The verification includes PSpice simulation and measurement with the CCTA block formed by commercially available active elements

High input impedance voltage-mode universal filter and its modification as quadrature oscillator using VDDDAs

The second order universal voltage-mode filter using voltage differencing differential difference amplifiers (VDDDAs) has been proposed. It has high input impedance voltage-mode biquad filter with orthogonal tune of natural frequency and quality factor. The proposed filter simultaneously provides five filter responses: low-pass (LP), high-pass (HP), band-reject (BR), all-pass (AP) and band-pass (BP) in the same circuit topology. The natural frequency and quality factor can be tuned electronically and orthogonally dc bias current. The output impedance at output nodes HP, AP and BR has low impedance which can connect to other circuit without the use of voltage buffers. The proposed filter consists of three VDDDAs, one grounded resistor and two grounded capacitors. This makes the proposed filter suitable for integrated circuit development. With slightly modifying the proposed filter, the voltage-mode qudrature sinusoidal oscillator with low output impedance and independent control of condition of oscillation (CO) and frequency of oscillation (FO) has been achieved. The results shown in this paper are from PSPICE simulation and experiment to validate the proposed circuits

Communication Subsystems for Emerging Wireless Technologies

The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels

A wideband linear tunable CDTA and its application in field programmable analogue array

This document is the Accepted Manuscript version of the following article: Hu, Z., Wang, C., Sun, J. et al. ‘A wideband linear tunable CDTA and its application in field programmable analogue array’, Analog Integrated Circuits and Signal Processing, Vol. 88 (3): 465-483, September 2016. Under embargo. Embargo end date: 6 June 2017. The final publication is available at Springer via https://link.springer.com/article/10.1007%2Fs10470-016-0772-7 © Springer Science+Business Media New York 2016In this paper, a NMOS-based wideband low power and linear tunable transconductance current differencing transconductance amplifier (CDTA) is presented. Based on the NMOS CDTA, a novel simple and easily reconfigurable configurable analogue block (CAB) is designed. Moreover, using the novel CAB, a simple and versatile butterfly-shaped FPAA structure is introduced. The FPAA consists of six identical CABs, and it could realize six order current-mode low pass filter, second order current-mode universal filter, current-mode quadrature oscillator, current-mode multi-phase oscillator and current-mode multiplier for analog signal processing. The Cadence IC Design Tools 5.1.41 post-layout simulation and measurement results are included to confirm the theory.Peer reviewedFinal Accepted Versio

Switched-current filter structure for synthesizing arbitrary characteristics based on follow-the-leader feedback configuration

This document is the Accepted Manuscript version of the following article: Wenshan Zhao, Yigang He, and Yichuang Sun, ‘Switched-current filter structure for synthesizing arbitrary characteristics based on follow-the-leader feedback configuration’, Analog Integrated Circuits and Signal Processing, (2015), Vol. 82 (2): 479-486. The version of record is available online at doi: 10.1007/s10470-014-0477-8 © Springer Science+Business Media New York 2015Peer reviewedFinal Accepted Versio