Low cost wideband tunable LNA
Methods and devices to fabricate low-cost wideband LNAs that are tunable to multiple frequency bands. Decoupling capacitors are used as part of a tuning circuit implemented at the LNA input. The capacitors are switchably selectable to also tune a signal into desired frequency bands.
1. A low noise amplifier (LNA) comprising:
a plurality of transistors configured in a cascode configuration;
an inductor with a first terminal of the inductor coupled to an RF input;
a DC decoupling element with a first terminal of the DC decoupling element coupled to a second terminal of the inductor and a second terminal of the DC decoupling element coupled to a gate of a transistor in the cascode configuration, and
the DC decoupling element further comprising a parallel connection of a plurality of series connected switches and capacitors.
2. The LNA of claim 1 , wherein the DC decoupling element is configured such that the capacitors are closest to the gate of the transistor.
3. The LNA of claim 2 , wherein the switches can be controlled to ON or OFF states to alter an input impedance match.
4. The LNA of claim 1 , wherein the capacitors, the switches and the plurality of transistors are all implemented on a single chip.
5. The LNA of claim 4 , wherein the single chip is a complementary metal-oxide-semiconductor (CMOS) chip.
6. The LNA of claim 4 , wherein the single chip is a silicon-on-insulator (SOI) chip.
7. The LNA of claim 4 , wherein the switches comprise CMOS switches.
8. The LNA of claim 4 , wherein the inductor is implemented outside the chip.
9. The LNA of claim 1 , wherein capacitance values of the capacitors are selected based on a binary scheme.
10. The LNA of claim 1 , wherein two or more of the one or more frequency bands are tuned into by switching in a) one capacitor at a time, b) two or more capacitors at a time, or c) a combination thereof.
11. The LNA of claim 1 , wherein a frequency band of the one or more frequency bands has a center frequency in the range of 1 to 10 GHz.
12. The LNA of claim 1 , wherein the frequency band of the one or more frequency bands has a bandwidth within the range of 20% to 25% of the center frequency.
13. The LNA of claim 1 , further comprising a bias resistor coupling bias voltage to the input of the transistor of the plurality of the transistors.
14. The LNA of claim 1 , wherein the switches are configured according to a frequency band of operation.