Single integrated circuit phase locked loop for synthesizing high-frequency signals for wireless communications and method for operating same

A wireless communication system, comprising:

• a frequency synthesizer for generating an output signal;
• a phase locked loop having an output frequency dependent upon a controllable oscillator circuit within the phase locked loop, the controllable oscillator circuit having connections for an external inductance and having an output frequency dependent upon a capacitance amount within an LC tank resonant structure;
• the controllable oscillator circuit comprising:
• a discretely variable capacitance circuit, the discretely variable capacitance circuit including a plurality of discrete capacitor circuits having capacitances that may be selectably included within an overall capacitance for the discretely variable capacitance circuit;
• a digital control signal coupled to the discretely variable capacitance circuit to control the overall capacitance for the discretely variable capacitance circuit;
• a continuously variable capacitance circuit coupled to the discretely variable capacitance circuit, the continuously variable capacitance circuit including a plurality of continuously variable capacitor circuits having capacitances that are included within an overall capacitance for the continuously variable capacitance circuit;
• and
• a variable control signal coupled to the continuously variable capacitance circuit to control an overall capacitance for the continuously variable capacitance circuit, the variable control signal comprising a plurality of analog control signals coupled to the plurality of continuously variable capacitor circuits;
• wherein the output frequency of the controllable oscillator circuit may be varied by adjusting the capacitance of the discretely variable capacitance and by adjusting the capacitance of the continuously variable capacitance circuit;
• and
• a mixing circuit coupled to mix an input signal with the output signal from the frequency synthesizer;
• wherein the output signal of the frequency synthesizer has a frequency above about 800 MHz and has phase noise of less than about −110 dBc/Hz at 100 kHz from the output frequency;
• and
• wherein the controllable oscillator circuit does not utilize a varactor diode to provide capacitance variations.

A method of operating a frequency synthesizer, comprising:

• providing a phase locked loop having an output frequency dependent upon a controllable oscillator circuit within the phase locked loop, the controllable oscillator circuit having connections for an external inductor and having an output frequency dependent upon a capacitance amount within an LC tank resonant structure, wherein the controllable oscillator circuit does not utilize a varactor diode to provide capacitance variations;
• controlling the output frequency of the controllable oscillator by adjusting a digital control signal to vary the capacitance of a discretely variable capacitance circuit, the discretely variable capacitance circuit including a plurality of discrete capacitor circuits having capacitances that may be selectably included within an overall capacitance for the discretely variable capacitance circuit;
• also controlling the output frequency of the controllable oscillator by adjusting a variable control signal to vary the capacitance of a continuously variable capacitance circuit coupled to the discretely variable capacitance circuit, the continuously variable capacitance circuit including a plurality of continuously variable capacitor circuits having capacitances that are included within an overall capacitance for the continuously variable capacitance circuit;
• the variable control signal comprising a plurality of analog control signals coupled to the plurality of continuously variable capacitor circuits;
• and
• generating an output frequency signal of the frequency synthesizer above about 800 MHz and having phase noise of less than about −110 dBc/Hz at 100 kHz from the output frequency.

A method for operating a wireless communication system, comprising:

• providing a phase locked loop having an output frequency dependent upon a controllable oscillator circuit within the p phase locked loop, the controllable oscillator circuit having connections for an external inductor and having an output frequency dependent upon a capacitance amount within an LC tank resonant structure, wherein the controllable oscillator circuit does not utilize a varactor diode to provide capacitance variations;
• controlling the output frequency of the controllable oscillator by adjusting a digital control signal to vary the capacitance of a discretely variable capacitance circuit, the discretely variable capacitance circuit including a plurality of discrete capacitor circuits having capacitances that may be selectably included within an overall capacitance for the discretely variable capacitance circuit;
• also controlling the output frequency of the controllable oscillator by adjusting a variable control signal to vary the capacitance of a continuously variable capacitance circuit coupled to the discretely variable capacitance circuit, the continuously variable capacitance circuit including a plurality of continuously variable capacitor circuits having capacitances that are included within an overall capacitance for the continuously variable capacitance circuit;
• and
• generating an output frequency signal of the frequency synthesizer above about 800 MHz and having phase noise of less than about −110 dBc/Hz at 100 kHz from the output frequency;
• and
• mixing an input signal with the output signal from the phase locked loop.