Voltage controlled oscillator with gain control
View Patent ↗A VCO circuit including a VCO, a voltage supply and a control circuit. The VCO has a supply voltage input and a gain that changes with its supply voltage. The voltage supply has an adjust input and an output coupled to the supply voltage input of the VCO. The voltage supply adjusts the voltage level of its output in response to changes of the adjust input. The control circuit has a first adjust output coupled to the adjust input of the voltage supply to adjust the gain of the VCO. The VCO may include a frequency range adjust input controlled by the control circuit so that the gain of the VCO is adjusted when the frequency range is changed. For a multi-band VCO, the gain is adjusted for different frequency bands to maintain a relatively constant gain for each frequency band.
1. A voltage controlled oscillator (VCO) circuit, comprising:
a VCO having a supply voltage input and a frequency range adjust input, wherein said VCO has a gain that changes with voltage level of said supply voltage input;
a voltage supply having an adjust input and a supply voltage output coupled to said supply voltage input of said VCO, wherein said voltage supply adjusts voltage level of said supply voltage output in response to changes of said adjust input; and
a control circuit having a at least one adjust output coupled to said adjust input of said voltage supply and to said frequency range adjust input of said VCO, wherein said control circuit controls said at least one adjust output to adjust frequency range and said gain of said VCO during operation of the VCO circuit.
2. The VCO circuit of claim 1 , wherein:
said at least one adjust output of said control circuit comprises a single adjust output which is coupled to said frequency range adjust input of said VCO and to said adjust input of said voltage supply; and
wherein said control circuit controls said single adjust output to adjust frequency range and gain of said VCO.
3. The VCO circuit of claim 2 , wherein said VCO comprises a multi-band VCO wherein said control circuit switches between multiple frequency bands of said VCO.
4. The VCO circuit of claim 2 , wherein said single adjust output of said control circuit, said adjust input of said voltage supply and said frequency range adjust input of said VCO each comprise a digital interface, and wherein said control circuit changes said single adjust output to select from among a plurality of discrete frequency bands and a corresponding plurality of gain factors of said VCO.
5. The VCO circuit of claim 1 , wherein said voltage supply comprises a super filter, which further comprises:
a voltage source;
a resistor string coupled to said voltage source and having a plurality of selectable voltage nodes;
select logic having a plurality of inputs coupled to said plurality of selectable voltage nodes and an output;
a driver having an input coupled to said output of said select logic and an output coupled to said supply voltage input of said VCO; and
a decoder having an input coupled to said at least one adjust output of said control circuit and a plurality of outputs coupled to said select logic for selecting one of said plurality of selectable voltage nodes.
6. The VCO circuit of claim 1 , wherein:
said control circuit has a first adjust output coupled to said adjust input of said voltage supply and a second adjust output coupled to said frequency range adjust input of said VCO; and
wherein said control circuit controls said first adjust output to adjust gain and controls said second adjust output to adjust frequency range of said VCO.
7. The VCO circuit of claim 6 , wherein said first and second adjust outputs of said control circuit, said adjust input of said voltage supply and said frequency range adjust input of said VCO each comprise a digital interface, and wherein said control circuit changes said first and second adjust outputs to select from among a plurality of discrete frequency bands and a corresponding plurality of gain factors of said VCO.
8. A phase lock loop (PLL) circuit, comprising:
a VCO having a supply voltage input, a frequency band adjust input, a frequency tune input and an output providing a clock, wherein said VCO has a gain that changes with voltage level of said supply voltage input;
a PLL control circuit having a first input receiving said clock, a second input receiving a reference clock, and an output providing a tune voltage to said frequency tune input of said VCO;
a voltage supply, having a voltage control input and having a supply voltage output coupled to said supply voltage input of said VCO, that adjusts voltage level of said supply voltage output based on said voltage control input; and
a controller having at least one adjust output coupled to said voltage control input of said voltage supply and to said frequency band adjust input of said VCO, wherein said controller controls said at least one adjust output to control gain and frequency band of said VCO during operation of the PLL circuit.
9. The PLL circuit of claim 8 , wherein said voltage supply comprises a super filter, which further comprises:
a plurality of voltage nodes;
select logic having a plurality of inputs coupled to said plurality of voltage nodes and an output;
a driver having an input coupled to said output of said select logic and an output coupled to said supply voltage input of said VCO; and
a decoder having an input coupled to said at least one adjust output of said controller and a plurality of outputs coupled to said select logic for selecting one of said plurality of voltage nodes.
10. The PLL circuit of claim 8 , wherein:
said at least one adjust output of said controller comprises a single adjust output which is coupled to said frequency band adjust input of said VCO; and
wherein said controller controls said single adjust output to adjust frequency band and gain of said VCO.
11. The PLL circuit of claim 10 , wherein said single adjust output of said controller, said voltage control input of said voltage supply and said frequency band adjust input of said VCO each comprise a digital interface, and wherein said controller updates said single adjust output to switch between a plurality of discrete frequency bands and a corresponding plurality of gain factors.
12. The PLL circuit of claim 8 , wherein said at least one adjust output of said controller comprises a first adjust output coupled to said voltage control input of said voltage supply for adjusting said gain and a second adjust output coupled to said frequency band adjust input of said VCO for controlling frequency band of operation.
13. The PLL circuit of claim 12 , wherein said first and second adjust outputs of said controller, said voltage control input of said voltage supply and said frequency band adjust input of said VCO each comprise a digital interface, wherein said controller updates said first adjust output to select from among a plurality of gain factors of said VCO, and wherein said controller updates said second adjust output to select from among a plurality of discrete frequency bands of said VCO.
14. The PLL circuit of claim 13 , wherein said plurality of discrete frequency bands comprises the Universal Mobile Telecommunications System band and the Personal Communications Services (PCS) band.
15. A method of controlling a voltage controlled oscillator (VCO), having a supply voltage input and a gain which varies with voltage level of the supply voltage input, said method comprising:
operating the VCO within a first frequency range;
providing a first voltage level to the supply voltage input of the VCO to achieve a first gain level;
changing to a second frequency range and operating the VCO in the second frequency range; and
adjusting the supply voltage input of the VCO from the first voltage level to a second voltage level to achieve a second gain level for the second frequency range.
16. The method of claim 15 , wherein said providing a first voltage level and said adjusting the supply voltage input each comprises providing a select value to a programmable voltage supply which provides a corresponding supply voltage to the supply voltage input of the VCO.
17. The method of claim 15 , wherein the VCO includes a frequency band select input, further comprising:
said operating the VCO within a first frequency range comprising providing the frequency band select input to operate the VCO at a first frequency band; and
said changing to a second frequency range comprising changing the frequency band select input to operate the VCO at a second frequency band.
18. The method of claim 17 , wherein said providing the frequency band select input and said providing a first voltage level comprises providing a select value to the frequency band select input of the VCO and to a programmable voltage supply which provides a corresponding supply voltage to the supply voltage input of the VCO.
19. The method of claim 17 , wherein said providing the frequency band select input and said changing the frequency band select input comprise providing first select values to the frequency band select input of the VCO and wherein said providing a first voltage level and said adjusting the supply voltage input comprise providing second select values to a programmable voltage supply which provides corresponding supply voltages to the supply voltage input of the VCO.