Methods for Extended Tunability in Quadrature Oscillators Based on Enhanced Electronic Control of Time Constants

Methods for Extended Tunability in Quadrature Oscillators Based on Enhanced Electronic Control of Time Constants

Článek WoS

New methods for extending the tunability range in second-order voltage controlled oscillators (VCOs) with quadrature outputs are presented and compared in this paper. Linear dependence is the most common type of relation between frequency of oscillations (FO) and control voltage (or current) in communication subsystems (VCOs). However, there are other non-linear types of dependencies that are advantageous (quadratic, cubic, …) and should be further studied. Positions of controllable blocks within the structure of the oscillator (providing parameters influencing time constants of integrators) in two scenarios are studied together. The impact of controllable parameters of these additional elements on FO as well as on produced output signal levels is evaluated. Simulation and experimental results are shown to confirm expected behavior of solutions in the case of the quadratic type of control of FO. Nowadays, standard linear control offers a tunability ratio 10:1 (for the same ratio of parameters that control the FO) only. However, in this paper the experimental tests yield a tunability ratio 80:1 (50 kHz – 4 MHz) for DC control voltage within the range 0.175 V to 1.75 V (10:1). The presented approach is very beneficial for low supply voltage systems requiring a wide range of tunability and also for utilizing active devices having limited range of adjustability of their controllable parameters while still requiring wide tunability.

New methods for extending the tunability range in second-order voltage controlled oscillators (VCOs) with quadrature outputs are presented and compared in this paper. Linear dependence is the most common type of relation between frequency of oscillations (FO) and control voltage (or current) in communication subsystems (VCOs). However, there are other non-linear types of dependencies that are advantageous (quadratic, cubic, …) and should be further studied. Positions of controllable blocks within the structure of the oscillator (providing parameters influencing time constants of integrators) in two scenarios are studied together. The impact of controllable parameters of these additional elements on FO as well as on produced output signal levels is evaluated. Simulation and experimental results are shown to confirm expected behavior of solutions in the case of the quadratic type of control of FO. Nowadays, standard linear control offers a tunability ratio 10:1 (for the same ratio of parameters that control the FO) only. However, in this paper the experimental tests yield a tunability ratio 80:1 (50 kHz – 4 MHz) for DC control voltage within the range 0.175 V to 1.75 V (10:1). The presented approach is very beneficial for low supply voltage systems requiring a wide range of tunability and also for utilizing active devices having limited range of adjustability of their controllable parameters while still requiring wide tunability.

adjustable current gain; adjustable voltage gain; current conveyor; electronic control; extended tunability range; quadrature oscillator; voltage controlled oscillator.

adjustable current gain; adjustable voltage gain; current conveyor; electronic control; extended tunability range; quadrature oscillator; voltage controlled oscillator.

ŠOTNER, R.; JEŘÁBEK, J.; HERENCSÁR, N.; PETRŽELA, J.

2019

20.02.2018

IEEE

IEEE, 445 Hoes Lane, Piscataway, NJ 08854-4141 USA

0018-9456

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT

67

6

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