Method and apparatus for transient frequency distortion compensation
View Patent ↗Transient distortion is compensated for by multiplying an exponentially-decaying phase shift onto the distorted waveform. The exponentially decaying phase shift waveform is patterned after the transient which typically takes the form of an exponential and occurs upon introduction of power to a circuit or circuit component. A digital circuit produces an appropriate exponentially-decaying waveform which is used as the input for a look up table whose output is a complex sinusoidal waveform capable of compensating for the distortion. The complex sinusoid is multiplied onto the transmitted waveform. The decaying exponential is biased so that it crosses a threshold at which point the compensating circuitry is turned off.
1. An apparatus for compensating for signal distortion, the apparatus comprising:
a distortion compensating device configured to produce a compensation signal having a phase shift magnitude approximately equivalent to a magnitude of a frequency distortion occurring on a signal being transmitted, the signal being a time-varying, information-bearing signal; and
a compensation multiplier configured to multiply the compensation signal onto the signal being transmitted for a limited time,
wherein the compensation signal is produced by the distortion compensating device during a transient time frame at a beginning of the signal being transmitted,
wherein the compensation signal is produced by the distortion compensating device during a transient time frame at an end of the signal being transmitted after power down of a device coupled to a transmission chain that processes the signal being transmitted.
2. The apparatus of claim 1 , wherein the frequency distortion is a transient distortion caused by the device turning off before physical layer processing of the signal being transmitted is completed.
3. The apparatus of claim 1 , wherein the device is a power amplifier.
4. The apparatus of claim 3 , wherein the frequency distortion is inferred from a transmit start signal.
5. An apparatus for compensating for signal distortion, the apparatus comprising:
a distortion compensating device configured to produce a compensation signal having a phase shift magnitude approximately equivalent to a magnitude of a frequency distortion occurring on a signal being transmitted, the signal being a time-varying, information-bearing signal; and
a compensation multiplier configured to multiply the compensation signal onto the signal being transmitted for a limited time,
wherein the compensation signal is produced by the distortion compensating device during a transient time frame at a beginning of the signal being transmitted,
wherein the compensation signal is produced by the distortion compensating device during a transient time frame at the beginning of the signal being transmitted after power up of a device coupled to a transmission chain that processes the signal being transmitted.
6. The apparatus of claim 5 , wherein the device is a Media Access Control (MAC).
7. The apparatus of claim 6 , wherein the frequency distortion is inferred from a MAC off signal.