Multi-band tunable resonant circuit

Abstract

A fully integrated, programmable mixed-signal radio transceiver comprising a radio frequency integrated circuit (RFIC) which is frequency and protocol agnostic with digital inputs and outputs, the radio transceiver being programmable and configurable for multiple radio frequency bands and standards and being capable of connecting to many networks and service providers. The RFIC includes a tunable resonant circuit that includes a transmission line having an inductance, a plurality of switchable capacitors configured to be switched into and out of the tunable resonant circuit in response to a first control signal, and at least one variable capacitor that can be varied in response to a second control signal, wherein a center resonant frequency of the resonant circuit is electronically tunable responsive to the first and second control signals that control a first capacitance value of the plurality of switchable capacitors and a second capacitance value of the at least one variable capacitor.

1 . A method of tuning a resonant circuit over a plurality of operating frequency bands and within one operating frequency band of the plurality of operating frequency bands, the method comprising:
 providing an inductance;   providing a first capacitance value and a second capacitance value each in parallel with the inductance to provide the resonant circuit;   selecting the first capacitance value in response to a first control signal to tune a resonant frequency signal of the resonant circuit to the one operating frequency band; and   selecting the second capacitance value in response to a second control signal to tune the resonant frequency within the one operating frequency band.   
   
   
       2 . The method of  claim 1 , wherein selecting the first capacitance value includes switching in and out of the resonant circuit at least one switchable capacitor of a plurality of switchable capacitors so as to obtain the first capacitance value. 
   
   
       3 . The method of  claim 1 , wherein the second capacitance value is provided by a varactor diode, and wherein selecting the second capacitance value includes varying a bias voltage of the varactor diode responsive to the second control signal. 
   
   
       4 . The method of  claim 1 , further comprising controlling a tuning range of a voltage controlled oscillator by coupling the resonant circuit to the voltage controlled oscillator. 
   
   
       5 . A wideband local oscillator tunable over a plurality of operating frequency bands and within a selected one of the plurality of operating frequency bands, the wideband local oscillator comprising:
 a voltage controlled oscillator configured to receive a resonant tuning signal and to generate a local oscillator signal, the local oscillator signal having a center operating frequency determined at least in part by the resonant tuning signal;   a resonant circuit including an inductor, a first capacitance and a second capacitance all connected in parallel, the resonant circuit being coupled to the voltage controlled oscillator and being configured to generate the resonant tuning signal;   the first capacitance comprising a plurality of switchable capacitors coupled to switches that allow selected ones of the plurality of switchable capacitors to be connected in the resonant circuit, responsive to a capacitor control signal, thereby determining a value of the first capacitance;   the second capacitance comprising at least one varactor diode configured to be tuned in response to a diode control signal to determine a value of the second capacitance; and   wherein a frequency of the resonant tuning signal is determined based on the first capacitance value and the second capacitance value in combination with the inductance; and   wherein the plurality of switchable capacitors are configured such that by switching into the resonant circuit the selected ones of the plurality of switchable capacitors, the first capacitance value is controlled so as to tune the frequency of the resonant tuning signal to the selected one of the plurality of operating frequency bands.   
   
   
       6 . The wideband local oscillator of  claim 5 , wherein the at least one varactor diode is configured such that tuning of a center frequency of the resonant frequency signal within the one operating selected frequency band is accomplished by adjusting the second capacitance value. 
   
   
       7 . The wideband local oscillator of  claim 5 , wherein controlling which selected ones of the plurality of switchable capacitors are connected into the resonant circuit allows selecting of different operating frequency bands of the plurality of operating frequency bands, so as to allow tuning of the resonant tuning signal over the plurality of operating frequency bands and within the selected one operating frequency band of the plurality of operating frequency bands. 
   
   
       8 . The wideband local oscillator of  claim 5 , wherein the plurality of switchable capacitors are MOS capacitors. 
   
   
       9 . The wideband local oscillator of  claim 5 , wherein the plurality of switchable capacitors are metal-insulator-metal (MIM) capacitors formed as part of a semiconductor integrated circuit comprising the resonant circuit. 
   
   
       10 . The wideband local oscillator of  claim 5 , wherein the second capacitance value is controlled by adjusting a bias voltage of the varactor diode responsive to the diode control signal.