Calibration of received signal strength indication
View Patent ↗Calibration of received signal strength indication (RSSI) within a radio frequency integrated circuit (RFIC) begins by concurrently enables a transmitter portion and receiver portion. With both the transmitter and receiver enabled, the RFIC provides a zero input to the transmitter portion, where the zero input is an effective zero input based on the input circuitry of the transmitter portion. The RFIC then measures, via the receiver portion, the received signal strength of the RF signal generated by the transmitter portion regarding the zero input signal. The RFIC then compares the measured received signal strength with a desired zero input signal strength value. If the measured received signal strength compares unfavorably with the desired zero input signal strength value (e.g., differ by more than a few percentage points), the received signal strength to power level table within the RFIC, which is used to convert a measured voltage into a dBm value, is scaled based on the difference between the measured received signal strength and the desired zero input signal strength value.
1. A method for calibrating received signal strength indication within a radio frequency integrated circuit (RFIC), the method comprises:
concurrently enabling a transmitter portion of the RFIC and a receiver portion of the RFIC;
providing a zero input to the transmitter portion, wherein the transmitter portion up converts the zero input via a mixer section to produce a radio frequency (RF) signal;
measuring received signal strength of the RF signal as received by the receiver portion while the transmitter portion and receiver portion are concurrent enabled to produce a measured received signal strength;
comparing the measured received signal strength with a desired zero-input signal strength value; and
when the measured received signal strength compares unfavorably to the desired zero-input signal strength value, scaling a received signal strength to power level table based on a difference between the measured received signal strength and the desired zero-input signal strength value.
2. The method of claim 1 , wherein the measuring the received signal strength of the RF signal further comprises:
sampling a received signal strength indication to produce a plurality of samples after expiration of a predetermined period of time to allow DC offset and local oscillation leakage correction circuits to settle; and
calculating the measured received signal strength from the plurality of samples.
3. The method of claim 1 further comprises:
determining whether the measured received signal strength is greater than the desired zero-input signal strength value;
when the measured received signal strength is greater than the desired zero-input signal strength value, scaling up values in the received signal strength to power level table; and
when the measured received signal strength is less than the desired zero-input signal strength value, scaling down values in the received signal strength to power level table.
4. An apparatus for calibrating received signal strength indication within a radio frequency integrated circuit (RFIC), the apparatus comprises:
processing module; and
memory operably coupled to the processing module, wherein the memory includes operational instructions that cause the processing module to:
concurrently enable a transmitter portion of the RFIC and a receiver portion of the RFIC;
provide a zero input to the transmitter portion, wherein the transmitter portion up converts the zero input via a mixer section to produce a radio frequency (RF) signal;
measure received signal strength of the RF signal as received by the receiver portion while the transmitter portion and receiver portion are concurrent enabled to produce a measured received signal strength;
compare the measured received signal strength with a desired zero-input signal strength value; and
when the measured received signal strength compares unfavorably to the desired zero-input signal strength value, scale a received signal strength to power level table based on a difference between the measured received signal strength and the desired zero-input signal strength value.
5. The apparatus of claim 4 , wherein the memory further comprises operational instructions that cause the processing module to measure the received signal strength of the RF signal by:
sampling a received signal strength indication to produce a plurality of samples after expiration of a predetermined period of time to allow DC offset and local oscillation leakage correction circuits to settle; and
calculating the measured received signal strength from the plurality of samples.
6. The apparatus of claim 4 , wherein the memory further comprises operational instructions that cause the processing module to:
determine whether the measured received signal strength is greater than the desired zero-input signal strength value;
when the measured received signal strength is greater than the desired zero-input signal strength value, scale up values in the received signal strength to power level table; and
when the measured received signal strength is less than the desired zero-input signal strength value, scale down values in the received signal strength to power level table.
7. A radio frequency integrated circuit (RFIC) comprises:
transmitter section operably coupled to convert outbound data into outbound radio frequency (RF) signals;
receiver section operably coupled to convert inbound RF signals into inbound data;
received signal strength indicator operably coupled to measure signal strength of the inbound RF signals to produce a measured signal strength; and
calibration module operably coupled to calibrate the measured signal strength by:
concurrently enabling the transmitter section and the receiver section;
providing a zero input to the transmitter section, wherein the transmitter section up converts the zero input via a mixer section to produce the outbound RF signal;
measuring received signal strength of the outbound RF signal as received by the receiver section while the transmitter section and receiver section are concurrent enabled to produce a measured received signal strength;
comparing the measured received signal strength with a desired zero-input signal strength value; and
when the measured received signal strength compares unfavorably to the desired zero-input signal strength value, scaling a received signal strength to power level table based on a difference between the measured received signal strength and the desired zero-input signal strength value.
8. The RFIC of claim 7 , wherein the measuring the received signal strength of the RF signal further comprises:
sampling a received signal strength indication to produce a plurality of samples after expiration of a predetermined period of time to allow DC offset and local oscillation leakage correction circuits to settle; and
calculating the measured received signal strength from the plurality of samples.
9. The RFIC of claim 7 , wherein the calibration module further functions to:
determine whether the measured received signal strength is greater than the desired zero-input input signal strength value;
when the measured received signal strength is greater than the desired zero-input signal strength value, scale up values in the received signal strength to power level table; and
when the measured received signal strength is less than the desired zero-input signal strength value, scale down values in the received signal strength to power level table.