Post-Amplifier PRB Filtering for Residual Subcarrier Energy

The patent divides the frequency spectrum into distinct segments (blanked PRBs and non-blanked PRBs) and applies different filtering treatments to each segment. The bandstop filter specifically targets and attenuates frequencies corresponding to blanked PRBs, while the bandpass filter allows frequencies corresponding to non-blanked PRBs to pass through. This segmentation approach enables selective mitigation of residual energy on blanked PRBs without affecting the transmission of desired signals on active PRBs.

The patent applies different filtering characteristics to different frequency regions. The bandstop filter is configured with specific stopband frequencies that correspond to blanked PRBs, creating localized attenuation only where needed. Similarly, the bandpass filter is configured with passband frequencies that correspond to non-blanked PRBs. This local quality approach ensures that filtering is applied precisely where required to eliminate residual energy, while preserving the integrity of desired transmissions in other frequency regions.

The patent combines the functions of bandstop filtering and bandpass filtering into a single filtering system that processes the amplified waveform simultaneously. The filtering system is configured to perform multiple functions: attenuating blanked PRB frequencies through bandstop filtering while allowing non-blanked PRB frequencies to pass through via bandpass filtering. This multi-functionality reduces the need for separate filtering stages and simplifies the overall system architecture compared to implementing independent bandstop and bandpass filter systems.

The patent applies filtering to the amplified waveform after power amplification, which is the final stage before transmission. By performing the filtering action at this preliminary point in the transmission chain, the system ensures that residual energy is attenuated before the signal is transmitted over the air. This timing of the filtering action optimizes the effectiveness of interference mitigation while minimizing the impact on desired signals, thereby reducing the complexity of additional correction mechanisms that would be needed if filtering were applied at earlier stages.

The patent performs filtering as a preliminary action immediately after power amplification, before the signal is transmitted through the antenna and into the communication channel. By applying the bandstop and bandpass filters at this stage, the system ensures that residual energy is attenuated while the signal is still in a controlled environment. This timing preserves signal integrity because the filtering occurs before the signal is exposed to channel impairments, and it minimizes energy consumption by avoiding the need for retransmission or additional signal processing at later stages.

The patent converts the potentially harmful effect of power amplifier nonlinearity, which generates spectral regrowth and residual energy on blanked PRBs, into a benefit by applying filtering that specifically targets and attenuates these unwanted frequency components. The bandstop filter is configured to reject frequencies corresponding to blanked PRBs, thereby converting the harmful spectral leakage and amplifier nonlinearity effects into a controlled attenuation process. This approach maintains signal integrity by removing harmful components while preserving the desired signal, and it does so in an energy-efficient manner by addressing the problem at the source rather than requiring additional power for error correction or retransmission.