In-situ gain calibration of radio frequency devices using thermal noise
An apparatus for calibrating gain of an radio frequency receiver (“Rx”) is disclosed to provide, among other things, a structure for performing in-situ gain calibration of an RF integrated circuit over time and/or over temperature without removing the RF integrated circuit from its operational configuration, especially when the gain of the RF integrated circuit is susceptible to variations in process, such as inherent with the CMOS process. In one embodiment, an exemplary apparatus includes a thermal noise generator configured to generate thermal noise as a calibrating signal into an input of an Rx path of an RF integrated circuit. The apparatus also includes a calibrator configured to first measure an output signal from an output of the Rx path, and then adjust a gain of the Rx path based on the thermal noise. In one embodiment, the thermal noise generator further includes a termination resistance and/or impedance.
1. A bi-modal radio receiver (“Rx”) integrated circuit formed on a substrate and configured to operate in a receiver mode to receive radio communication signals and to operate in a calibration mode to perform in-situ gain calibration, the bi-modal radio Rx integrated circuit comprising:
an antenna port configured to receive radio communication signals from an antenna;
an in-situ calibration signal generator configured to internally generate a calibration signal;
a mode selector configured to select a signal source from either said antenna port or said in-situ calibration signal generator; and
an amplification path including an amplifier having a gain that is adjustable, said amplification path coupled to said mode selector for amplifying radio communication signals in said receiver mode and for amplifying said calibration signal in said calibration mode,
wherein said amplifier is configured to receive an adjustment signal representative of an amount to adjust said gain; and
wherein said amplification path further comprises an analog-to-digital converter, whereby said adjustment signal is configured to modify said gain to minimize measurement errors due to said analog-to-digital converter including clipping errors, quantization noise floor errors, and estimation errors due to sample size.
2. The bi-modal radio Rx integrated circuit of claim 1 wherein said calibration signal is thermally generated and said amplifier is a radio frequency (“RF”) amplifier.
3. The bi-modal radio Rx integrated circuit of claim 1 wherein said adjustment signal is based on a noise figure value of at least a portion of said amplification path.