Four-phase Oscillator Research Articles

A new first-order universal filter consisting of two ICCII + s and a grounded capacitor

In this paper, a new inverting second-generation current conveyor-based first-order current-mode universal filter is proposed. The main features of the proposed filter are described as follows: the use of a grounded capacitor that is attractive for integration, electronically tunable, no passive element matching condition, resistor-less, having the feature of both low input and high output impedances as well as providing all the first-order universal filter responses such as low-pass, high-pass and all-pass ones. As application examples, a sinusoidal oscillator and a four-phase oscillator are given. Many simulations through SPICE program and some experiments are achieved in order to exhibit the performance of the proposed filter.

New Compact VM Four-Phase Oscillator Employing Only Single Z-Copy VDTA and All Grounded Passive Elements

In this paper, a new compact voltage-mode four-phase oscillator employing single z-copy voltage differencing transconductance amplifier (ZC-VDTA) and only grounded passive elements is introduced. The use of only grounded capacitors and resistors makes the proposed circuit ideal for integrated circuit implementation. The condition of oscillation and the frequency of oscillation are independently adjustable. The passive and active sensitivities of the proposed circuit configuration are low. Experimental measurement results using readily available Maxim Integrated ICs MAX435 are given to prove the theory. DOI: http://dx.doi.org/10.5755/j01.eee.19.10.5900

Analysis and Design of a Double-Quadrature CMOS VCO for Subharmonic Mixing at $Ka$-Band

In this paper, we analyze the potentials of a four-phase 14-GHz CMOS voltage-controlled oscillator, tailored to a sub-harmonic receiver, for signal processing at Ka-band. When mild phase accuracies between in-phase and quadrature down-converted signals are required, the four-phase oscillator displays roughly the same phase noise figure-of-merit as quadrature oscillator counterparts. However, the operation at half-frequency leads to an improved performance due to a higher quality factor of the tuning varactors, and because the local oscillator circuitry and signal path run at different frequencies, relaxing coupling issues. A detailed time-variant analysis of phase noise in multiphase oscillators is introduced and validated by both simulations and experiments. Prototypes realized in a 65-nm technology occupy an active area of 0.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and show the following performances: a 26% frequency tuning range (from 12.2 to 15.9 GHz), maximum phase error from pi/4 of 2deg, and a phase noise of -110 dBc/Hz at 1 MHz from 14 GHz, while consuming 18 mA from 0.8-V supply.

Advanced antenna system for Alfvén wave plasma heating and current drive in TCABR tokamak

An advanced antenna system that has been developed for investigation of Alfvén wave plasma heating and current drive in the TCABR tokamak is described. The main goal was the development of such a system that could insure the excitation of travelling single helicity modes with predefined wave mode numbers M and N. The system consists of four similar modules with poloidal windings. The required spatial spectrum is formed by proper phasing of the RF feeding currents. The impedance matching of the antenna with the four-phase oscillator is accomplished by resonant circuits which form one assembly unit with the RF feeders. The characteristics of the antenna system design with respect to the antenna-plasma coupling and plasma wave excitation, for different phasing of the feeding currents, are summarised. The antenna complex impedance Z= Z R+ Z I is calculated taking into account both the plasma response to resonant excitation of fast Alfvén waves and the nonresonant excitation of vacuum magnetic fields in conducting shell. The matching of the RF generator with the antenna system during plasma heating is simulated numerically, modelling the plasma response with mutually coupled effective inductances with corresponding active Z R and reactive Z I impedances. The results of the numerical simulation of the RF system performance, including both the RF magnetic field spectrum analysis and the modelling of the RF generator operation with plasma load, are presented.