Embedded voltage controlled oscillator with minimum sensitivity to process and supply

A voltage controlled oscillator, for the creation of an output signal having a frequency that is proportional to a current biasing voltage and an amplitude that is proportional to an impedance control voltage comprising:

• a) a differential ring oscillator, to produce a differential oscillating signal having the frequency and an amplitude, comprising:
• a current bias port to modify said frequency with a magnitude of a current biasing voltage applied to said current bias port, whereby said current biasing voltage has a minimum level to prevent instability in said differential ring oscillator and has a compensation component to compensate for fluctuations due to variations in manufacturing process, power supply voltage source, and operating temperature,
• a impedance control port to adjust the amplitude with an impedance control voltage applied to said impedance control port,
• a differential output port consisting of a positive output terminal and a negative output terminal wherein said differential oscillating signal is placed on said differential output port, and
• a plurality of serially connected differential delay elements, wherein each differential delay element has a positive input terminal, a negative input terminal, a positive output terminal, a negative output terminal, a current bias input terminal connected to the current bias port, and an impedance control terminal connected to the impedance control port, wherein said differential delay element will create a differential output delay signal between the positive and negative output terminals that is a version of a differential input signal that is delayed in time, and wherein the positive and negative output terminals of a last differential delay element of the plurality of serially connected differential delay elements are cross connected to the positive and negative input terminals of a first differential delay element of the plurality of serially connected differential delay elements;
• and
• b) a voltage to current bias converter to convert the input voltage level to the current bias voltage, comprising:
• a voltage control terminal to receive the input voltage level,
• a current bias output terminal connected to the current bias port to transfer to transfer the current bias voltage to said current bias port,
• a first field effect transistor of the first conductivity type to establish the current bias voltage having a source connected to the power supply voltage source, and a gate connected to a drain which is connected to the current bias voltage output terminal,
• a fourth field effect transistor of a second conductivity type to act as a source follower, having a drain connected to the drain of the first field effect transistor of the conductivity type, a gate connected to the voltage control terminal, and a source,
• a resistor coupled between the source of the fourth field effect transistor of the second conductivity type and the ground reference point, such that a voltage is developed at the source of the fourth field effect transistor of the second conductivity type that is equal to the input voltage level less a magnitude of a threshold voltage of the fourth field effect transistor of the second conductivity type,
• a second field effect transistor of the first conductivity type to establish the minimum level of the current bias voltage, having a source connected to the drain of the first field effect transistor of the first conductivity type, a gate connected to a biasing voltage source to establish a constant current through the first field effect transistor of the first conductivity type to establish the minimum for the frequency, and a drain connected to the source of the fourth field effect transistor of the second conductivity type, and
• a current subtraction means to perform a subtraction from the constant current to vary the current bias voltage and to create the compensation component, comprising:
• a third field effect transistor of the first conductivity type having a source connected to the power supply voltage source, a gate connected to a second biasing voltage source, and a drain,
• a fourth field effect transistor of the first conductivity type having a source connected to the drain of the third field effect transistor of the first conductivity type, a gate connected to the voltage control terminal, and a drain, and
• a fifth field effect transistor of the second conductivity type having a drain connected to the drain of the fourth field effect transistor of the first conductivity type, a gate connected to the voltage control terminal, and a source connected to the fourth field effect transistor of the second conductivity type.