Variable frequency crystal oscillator using variable negative inductance or capacitance

This letter refers to one by Capparelli and Verrazzani [1]. Its aim is to present new techniques for building a variable frequency crystal oscillator based on the use of a negative inductor or capacitor. The interval available for the frequency deviation is larger than the one existing between the natural frequencies fpand fsof the crystal. The spurious frequencies uncontrolled by the crystal are absent.