Design of Electronically Controllable Quadrature Sinusoidal Oscillator with Linear Control of Frequency

In this paper, the design of sinusoidal oscillator which generates two output voltages with 90° degree phase difference is presented. The design procedure is started from the function block diagram to proposed oscillator using commercially available ICs. The proposed oscillator is constructed from three OTAs, one voltage summing circuit, one grounded resistor and two grounded capacitors. The frequency of the generated sinusoidal waveform is electronically and linearly controlled without disturbing the condition for oscillating of the system. With this feature, the proposed oscillator is used to generates the frequency modulation (FM) signal. The magnitude of the quadrature voltage waveform is equal during adjusting the generated frequency. A Pspice simulation and experiment are done to verify the performance of the proposed circuit. The macro models of available ICs, LM13700 and AD830 are employed for simulation. The simulation and experimental results confirm theory well as expected.