Patent ID: 6311050
Filing Date: 2001-10-30
Classification: H03J,H03L

Abstract:
A frequency synthesizer on a single integrated circuit, comprising: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; anda 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;wherein the output frequency signal of the frequency synthesizer is above about 800 MHz and has phase noise of less than about -110 dBc/Hz at 100 kHz from the output frequency; andwherein the controllable oscillator circuit does not utilize a varactor diode to provide capacitance variations.