Receiver DC offset calibration with antenna connected
Systems and methods for determining the DC offset of a wireless device including the antenna are disclosed. Systems and methods for calibrating or cancelling the DC offset are also disclosed.
1. A wireless device comprising:
a receiver to receive a receive signal from one or more other wireless devices;
an antenna connected to the receiver;
a processor to determine a DC offset value of the wireless device with the antenna connected by performing energy detection and averaging, and calibrate the wireless device using the determined DC offset value,
wherein the energy detection and averaging comprise, each time when the receiver has filled a sample buffer of an analog to digital converter with a plurality of samples, determining an average of the plurality of the samples in the sample buffer to obtain a DC power of the system, computing a total power of the plurality of the samples, computing an AC power of the plurality of samples by subtracting the DC power from the total power, comparing the AC power to a predetermined threshold, wherein only if the AC power is higher than the predetermined threshold, the AC power and the DC power are rejected, and only if the AC power is below the predetermined threshold, moving average buffers are updated with the AC power and the DC power, and
wherein an averaged AC power and the DC offset value are determined by averaging the AC power with previous AC power values and averaging the DC power with previous DC power values in the moving average buffers, respectively; and
memory to store the DC offset value.
2. The wireless device of claim 1 , further comprising a digital to analog converter, and wherein the wireless device is calibrated by adjusting the value at the digital to analog converter.
3. The wireless device of claim 1 , further comprising a receive chain, and wherein the wireless device is calibrated by adjusting a gain at the receive chain.
4. The wireless device of claim 1 , wherein the wireless device is calibrated by adjusting a gain in multiple components of the wireless device.
5. A method comprising:
receiving a plurality of receive signals at a receiver of a wireless device;
performing energy detection and averaging on the plurality of received signals in a processor of a wireless device to determine a DC offset, the wireless device comprising an antenna,
wherein performing the energy detection and averaging comprises, each time the receiver has filled a sample buffer of an analog to digital converter with a plurality of samples of the plurality of received signals, determining an average of the plurality of samples in the sample buffer to obtain a DC power of the system, computing a total power of the plurality of samples, and computing an AC power of the plurality of samples by subtracting the DC power from the total power;
comparing the AC power determined with a predetermined threshold, wherein the predetermined threshold comprises previously averaged values of energy of previously received signals of the plurality of receive signals, wherein only if the AC power is higher than the predetermined threshold, the AC power and the DC power are rejected, and only if the AC power is below the predetermined threshold, moving average buffers are updated with the AC power and the DC power; and
determining an averaged AC power and the DC offset by averaging the AC power with previous AC power values and averaging the DC power with previous DC power values in the moving average buffers, respectively; and
storing the DC offset in memory of the wireless device.
6. The method of claim 5 , further comprising performing calibration to adjust a DC cancellation based on the determined DC offset.
7. The method of claim 6 , wherein the DC cancellation is adjusted in a closed-loop fashion to cancel the DC offset to within a predefined range for the wireless device.
8. The method of claim 5 , wherein the total energy is used to update a previously averaged value if the total energy is the same as or lower than the previously averaged value.
9. The method of claim 6 , wherein the wireless device is calibrated by adjusting a gain at a digital to analog converter.
10. The method of claim 6 , wherein the wireless device is calibrated by adjusting a gain at a receive chain.
11. The method of claim 6 , wherein the wireless device is calibrated by adjusting a gain in multiple components of the wireless device.