Tunable notch filter and contour tuning circuit

Abstract

Aspects of this disclosure relate tuning an impedance presented to a common port of a multi-throw switch and a tunable notch filter coupled to the common port. The impedance presented to the common port can be tuned based on an impedance associated with a throw of the multi-throw switch that is activated. According to embodiments of this disclosure, a shunt inductor in parallel with a tunable capacitance circuit can tune the impedance presented to the common port of the multi-throw switch. In certain embodiments, the tunable notch filter includes a series LC circuit in parallel with a tunable impedance circuit.

1 . (canceled) 
     
     
         2 . A radio frequency system comprising:
 an antenna switch including multiple throws;   an antenna port; and   a tunable notch filter configured to filter a radio frequency signal propagating between the antenna switch and the antenna port, the tunable notch filter including a tunable impedance circuit and a series resonance circuit in parallel with the tunable impedance circuit, the tunable impedance circuit including a switch in series with a capacitor, and the series resonance circuit arranged to limit a voltage swing across the switch of the tunable impedance circuit.   
     
     
         3 . The radio frequency system of  claim 2  wherein the radio frequency signal has a power of at least 15 decibel-milliwatts. 
     
     
         4 . The radio frequency system of  claim 2  wherein the series resonance circuit includes a tunable capacitance circuit in series with an inductor. 
     
     
         5 . The radio frequency system of  claim 2  wherein the series resonance circuit includes a capacitor in series with an inductor. 
     
     
         6 . The radio frequency system of  claim 2  wherein the tunable notch filter provides a notch at a second harmonic frequency of the radio frequency signal. 
     
     
         7 . The radio frequency system of  claim 2  wherein the series resonance circuit has a resonant frequency that corresponds to the frequency of the radio frequency signal. 
     
     
         8 . The radio frequency system of  claim 2  wherein the series resonance circuit is configured to limit a voltage across the switch to less than 1.4 Volts. 
     
     
         9 . The radio frequency system of  claim 2  wherein the series resonance circuit is configured to limit a voltage across the switch to less than 1 Volt. 
     
     
         10 . The radio frequency system of  claim 2  further comprising a low pass filter coupled between the common node and the antenna port. 
     
     
         11 . The radio frequency system of  claim 2  wherein the series resonance circuit is configured to effectively short the tunable impedance circuit at a frequency of the radio frequency signal. 
     
     
         12 . A method of filtering radio frequency signals, the method comprising:
 adjusting an impedance of a tunable impedance circuit of a tunable notch filter coupled between a common node of an antenna switch and an antenna, the tunable notch filter including a series resonance circuit in parallel with the tunable impedance circuit;   filtering, with the tunable notch filter, a radio frequency signal propagating between the common node and the antenna; and   limiting a voltage swing across the tunable impedance circuit with the series resonance circuit of the tunable notch filter during the filtering.   
     
     
         13 . The method of  claim 12  wherein the tunable impedance circuit includes a switch in series with a capacitor. 
     
     
         14 . The method of  claim 13  wherein the limiting causes a voltage across the switch to be less than 1.4 Volts. 
     
     
         15 . The method of  claim 12  wherein the radio frequency signal has a power of at least 15 decibel-milliwatts. 
     
     
         16 . The method of  claim 12  further comprising low pass filtering the radio frequency signal with a low pass filter coupled between the common node and the antenna port. 
     
     
         17 . The method of  claim 12  wherein the filtering provides a notch at a second harmonic frequency of the radio frequency signal. 
     
     
         18 . The method of  claim 12  wherein the series resonance circuit is a series LC circuit. 
     
     
         19 . A wireless communication device comprising:
 an antenna configured to transmit a radio frequency signal;   an antenna switch including multiple throws; and   a tunable notch filter coupled in series between the antenna switch and the antenna, the tunable notch filter including a tunable impedance circuit and a series resonance circuit in parallel with the tunable impedance circuit, and the series resonance circuit arranged to limit a voltage swing across the tunable impedance circuit.   
     
     
         20 . The wireless communication device of  claim 19  wherein the radio frequency signal is a carrier aggregation signal 
     
     
         21 . The wireless communication device of  claim 19  wherein the wireless communication device is a mobile phone.