Method for operating a base station by prelimiting an output signal station
View Patent ↗A base station employing a CDMA technique comprising the steps of combining a plurality of spread spectrum data signals into a combined signal having a fluctuating power level corresponding to the data signals; modulating the combined signal to produce an RF signal; measuring average power of the combined signal over a selected time period; adaptively limiting the combined signal power to a calculated level based at least in part on the measured power; and transmitting the RF signal.
1. A base station comprising:
a plurality of mixers configured to mix a plurality of data signals with different code sequences;
a combiner configured to combine the plurality of mixed data signals to produce a combined signal;
an adjustable signal limiter configured to produce a limited signal wherein the adjustable signal limiter is coupled to an output of the combiner;
a mixer configured to modulate the limited signal up to radio frequency;
a power measurement device configured to measure a power of the modulated limited signal over a predetermined time period;
an amplifier configured to amplify the modulated limited signal to a predetermined power level to produce an amplified signal;
an antenna configured to radiate the amplified signal, and
a processor coupled to an output of the amplifier and configured to:
determine an average of a square of a magnitude of the amplified signal over the predetermined time period;
measure a power of the amplified signal;
determine a clipping level of the adjustable signal limiter based on the measured power of any one of: the modulated limited signal or the amplified signal; and
scale down the output of the power measurement device by a gain of the amplifier.
2. The base station according to claim 1 wherein the plurality of data signals includes any one of traffic signals, pilot signals, or maintenance signals.
3. The base station according to claim 1 wherein the adjustable signal limiter limits signal power levels.
4. The base station according to claim 1 wherein an output of the power measurement device approximates a variance of the modulated limited signal.
5. The base station according to claim 1 wherein an output of the power measurement device approximates a variance of the amplified signal.
6. The base station according to claim 1 wherein
the power measurement device is configured to approximate a variance of the amplified signal over the predetermined time period; and
the processor is configured to determine a square root of the amplified signal as a standard deviation.
7. The base station according to claim 6 wherein the standard deviation is two times a clipping level of the adjustable signal limiter.
8. The base station according to claim 1 wherein the processor is configured to override a determined clipping level of the adjustable signal limiter.
9. The base station according to claim 1 wherein the processor is configured to control the gain of the amplifier.
10. The base station according to claim 9 wherein the gain of the amplifier is adjusted to prevent the amplifier from going into a nonlinear operating region.