A New Two-Three-Phase Voltage-Controlled Oscillator

The initial aim of the work has been the development of an inexpensive quadrature oscillator which can operate as a rapidly responding voltage-controlled oscillator (VCO) in two phases. Such rapid operation in quadrature is needed in association with quickly operating phase-locked loops for frequency synthesizers and similar applications. Other applications, where the relatively large speed is not essential, but where the phase shifts between various outputs should be precise, are mentioned in concluding this section. The electronic realization is made relatively cheap by proposing a replacement of the instantaneous amplitude measuring operation of square and sum (x2 + y2) (associated in the process of amplitude stabilization) by an operation of three-phase rectification. This leads to the construction of a versatile instrument which generates three-phase signals as well as two-phase signals (the two-phase signals are both sinewaves in quadrature and also square waves in quadrature). All these waveforms are capable of participating in the system performance as a VCO at a relatively large rate of frequency changes. A reversal in the order of phases when the frequency-control voltage crosses zero is also exhibited. This is needed in applications in industrial and power electronics. Our main aim now is to use the instrument in association with a precisely stabilized quickly responding cyclo-converter. Other possible applications of the instrument are in the field of precise measurements (for example, in the detection of signals by lock-in amplification there exists a frequent need for quadrature operation) and in telecommunication. The quadrature operation assists in double-channel lock-in amplifier systems in avoiding the need for a reference phase adjustment.