Voltage controlled oscillator with controlled capacitance ratio in positive feedback loop to broaden bandwidth

A voltage controlled oscillator comprising:

• resonant circuit means having at least a coil and a first variable capacitance diode, and for resonating within predetermined variable frequency ranges;
• active circuit means having an input, an output, and an active element connected between said output and said input, said input being connected to said resonant circuit means in order to receive a resonant output therefrom;
• coupling control means having a first capacitor for connecting at least said resonant circuit means to said active circuit means as a capacitance coupling, and a second variable capacitance diode for adjusting the strength of said capacitance coupling in accordance with a resonant frequency of said resonant circuit means;
• variable capacitance ratio means having at least a third variable capacitance diode and a second capacitor connected in a positive feedback manner between said input and said output of said active circuit means in order to oscillate said active element of said active circuit means at a resonant frequency of said resonant circuit means;
• and
• variable control means for changing a resonant frequency of said resonant circuit means to thereby apply a control voltage to said first, second and variable capacitance diodes and for controlling a capacitance ratio between said first capacitor and said second variable capacitance diode of said variable capacitance ratio means, so that an oscillator frequency of said active element can be changed substantially linearly over a wide bandwidth of no less than one octachord in accordance with a variation in said control voltage, to thereby retain the strength of the capacitance coupling between said resonant circuit means and said active circuit means substantially at a predetermined level in accordance with a resonant frequency of said resonant circuit means and to retain an amount of positive feedback at a predetermined value against the oscillator frequency of said active element.