Radio frequency tuner
An RF tuner is described for handling RF signals in a broad frequency range and a broad power range while maintaining high linearity and tolerating high power blockers. A continuous feedback loop comprising a substantially linear LNA and an RF RSSI can adjust the power of the RF signal on the RF side. A substantially linear, variable gain transconductor may convert and amplify the voltage of the RF signal to a current signal. The converted signal may be down converted and filtered to an IF or baseband signal. An IF or baseband RSSI may measure the power of the down converted and filtered signal. The measured power may be compared against a preferred value to adjust the amplification of the transconductor.
1. A method for processing a first signal, the method comprising:
receiving, at a receiver, the first signal;
amplifying, at a transconductor in the receiver, the first signal in a voltage format to a second signal in a current format, an amplitude of the second signal being proportional to an amplitude of the first signal;
converting, by a switch connected to the transconductor, the second signal with a first frequency to a third signal with a second frequency, wherein the second frequency is lower than the first frequency;
filtering, by a first filter of the receiver, the third signal into a fourth signal;
measuring a power value of the fourth signal;
determining that the power value is larger than a threshold value;
decreasing an amount of amplification at the transconductor;
conveying a quadrature component of the second signal along a quadrature path;
conveying an in-phase component of the second signal along an in-phase path, wherein one of the quadrature path or the in-phase path carries both the third signal and the fourth signal; and
applying a load on a path that does not carry both the third signal and the fourth signal to match the load applied by measuring the power value of the fourth signal.
2. The method of claim 1 , further comprising:
conveying a quadrature component of the second signal along a quadrature path; and
conveying an in-phase component of the second signal along an in-phase path, wherein one of the quadrature path or the in-phase path carries both the third signal and the fourth signal.
3. The method of claim 1 , further comprising changing the threshold value.
4. The method of claim 1 , further comprising:
determining that the power value is smaller than the threshold value; and
increasing the amount of amplification at the transconductor.
5. The method of claim 1 , further comprising:
filtering, by a second filter, the first signal.
6. The method of claim 5 , wherein the first filter is a low pass filter and the second filter is a bandpass filter.
7. The method of claim 1 , wherein the transconductor comprises a plurality of attenuators in series.
8. The method of claim 7 , wherein the plurality of attenuators are highly linear and programmable.
9. A system comprising:
a transconductor configured to amplify a first signal in a voltage format to a second signal in a current format, an amplitude of the second signal being proportional to an amplitude of the first signal;
a switch connected to the transconductor and configured to convert the second signal with a first frequency to a third signal with a second frequency, wherein the second frequency is lower than the first frequency;
a first filter configured to receive the third signal and to filter the third signal into a fourth signal;
a first received signal strength indicator (RSSI) configured to:
measure a power value of the fourth signal;
determine that the power value is larger than a threshold value; and
decrease the amount of amplification at the transconductor;
a second RSSI;
a quadrature path configured to receive a quadrature component of the second signal; and
an in-phase path configured to receive an in-phase component of the second signal, wherein one of the quadrature path or the in-phase path carries both the third signal and the fourth signal, and wherein the second RSSI is configured to measure the power of a fifth signal that is on the path that does not carry both the third signal and the fourth signal.
10. The system of claim 9 , further comprising:
a quadrature path configured to receive a quadrature component of the second signal; and
an in-phase path configured to receive an in-phase component of the second signal, wherein one of the quadrature path or the in-phase path carries both the third signal and the fourth signal.
11. The system of claim 9 , wherein the first RSSI is further configured to change the threshold value.
12. The system of claim 11 , wherein the first RSSI threshold value is programmable via a serial port on the first RSSI.
13. The system of claim 9 , wherein the first RSSI is further configured to:
determine that the power value is smaller than the threshold value; and
increase the amount of amplification at the transconductor.
14. The system of claim 9 , further comprising:
a second filter configured to filter the first signal.
15. The system of claim 14 , wherein the first filter is a low pass filter and the second filter is a bandpass filter.
16. The system of claim 9 , wherein the transconductor comprises a plurality of attenuators in series.
17. The system of claim 16 , wherein the plurality of attenuators are highly linear and programmable.
18. The system of claim 17 , wherein the first RSSI is further configured to decrease the amount of amplification in the transconductor by being configured to send a control voltage signal to active resistors contained in the plurality of attenuators.