Electronic device with adjustable filter and associated methods
An electronic device includes an adjustable filter with a first filter element, and a second filter element coupled to the first filter element. The second filter element includes a field effect transistor (FET) including a source terminal, a drain terminal, and a gate terminal. The source terminal and the gate terminal are coupled to a reference voltage. A control circuit is coupled to the drain terminal and is configured to apply a control voltage thereto to vary a capacitance between the source and drain terminals to adjust the adjustable filter.
1. An electronic device comprising:
an adjustable filter comprising
a first filter element,
a second filter element coupled to said first filter element, said second filter element comprising a field effect transistor (FET) comprising a source terminal, a drain terminal, and a gate terminal, said source terminal and said gate terminal being coupled to a reference voltage, and
a control circuit coupled to said drain terminal and configured to apply a control voltage thereto to vary a capacitance between said source and drain terminals to adjust said adjustable filter.
2. The electronic device of claim 1 , wherein said adjustable filter comprises an adjustable bandpass, bandstop, lowpass, or highpass filter.
3. The electronic device of claim 1 , wherein said first filter element comprises an inductor.
4. The electronic device of claim 1 , wherein said first filter element comprises a capacitor.
5. The electronic device of claim 1 , further comprising radio frequency (RF) transmitter circuitry coupled to said adjustable filter.
6. The electronic device of claim 5 , wherein said RF transmitter circuitry comprises an up converter and a power amplifier cooperating with said adjustable filter.
7. The electronic device of claim 1 , further comprising radio frequency (RF) receiver circuitry coupled to said at least one adjustable filter.
8. The electronic device of claim 7 , wherein said RF receiver circuitry comprises a down converter and an amplifier cooperating with said adjustable filter.
9. The electronic device of claim 1 , wherein said FET comprises a source region underlying said source terminal, a drain region underlying said drain terminal, and a channel extending therebetween.
10. A radio frequency (RF) transmitter comprising:
an adjustable filter comprising
a first filter element comprising an inductor,
a second filter element coupled to said first filter element, said second filter element comprising a field effect transistor (FET) comprising a source terminal, a drain terminal, and a gate terminal, said source terminal and said gate terminal being coupled to a reference voltage, and
a control circuit coupled to said drain terminal and configured to apply a control voltage thereto to vary a capacitance between said source and drain terminals to adjust said adjustable filter; and
transmitter circuitry cooperating with said adjustable filter.
11. The RF transmitter of claim 10 , wherein said transmitter circuitry comprises an up converter and a power amplifier.
12. A radio frequency (RF) receiver comprising:
an adjustable filter comprising
a first filter element comprising an inductor,
a second filter element coupled to said first filter element, said second filter element comprising a field effect transistor (FET) comprising a source terminal, a drain terminal, and a gate terminal, said source terminal and said gate terminal being coupled to a reference voltage, and
a control circuit coupled to said drain terminal and configured to apply a control voltage thereto to vary a capacitance between said source and drain terminals to adjust said adjustable filter; and
receiver circuitry cooperating with said adjustable filter.
13. The RF receiver of claim 12 , wherein said receiver circuitry comprises a down converter and an amplifier cooperating with said adjustable filter.
14. An adjustable filter for an electronic device comprising:
a first filter element;
a second filter element coupled to said first filter element, said second filter element comprising a field effect transistor (FET) comprising a source terminal, a drain terminal, and a gate terminal, said source terminal and said gate terminal being coupled to a reference voltage; and
a control circuit coupled to said drain terminal and configured to apply a control voltage thereto to vary a capacitance between said source and drain terminals to adjust the adjustable filter.
15. The adjustable filter of claim 14 , wherein said first filter element comprises at least one of an inductor and a capacitor.