## 6 Conclusions  
Power supply rejection for the ET PA and receiver sensitivity degradation due to PA noise were analyzed, and these show the importance of the output noise performance of the supply modulator. The low output noise is made possible by noise blocking and generating a low output impedance. The RFT blocks switching noise transfer between the power inductor of the switching amplifier. The notch filter and load capacitance achieve low output impedance and remove the output noise. The measured results show a maximum of 1.8/5/5.3/3.8/3 dB noise reduction in the LTE B17/B5/B2/B3/B7 RX band due to the RFT and notch filter, respectively. The designed SM achieved peak efficiencies of 78-83% for LTE signals with a 5.8 dB PAPR with various channel bandwidths. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Band** & \
\begin{tabular}{c} **Duplex Spacing** \\ **(MHz)** \\ \end{tabular} &
\begin{tabular}{c} **SM Output Noise** \\ **(dBm/Hz)** \\ \end{tabular} \\ \hline \multirow{2}{*}{This Work} & B17 & 30 & \(-136.5\) \\  & B5 & 45 & \(-143\) \\ \hline \multirow{2}{*}{[13] ISSCC16} & B17 & 30 & \(-129\) \\  & B5 & 45 & \(-134\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Performance comparison. Figure 10: Measured output noise of the designed supply modulator in the cases of reference sensitivity QPSK PREFSENS (Table 7.3.1-1 in [5]) for each LTE band. Figure 9: PSRR measurement setup and chip photograph. Funding: This study was conducted with support from institute information & communications technology planning & evaluation from the government (Ministry of Science and ICT) in 2024. (No. RS-2024-00395702, Development of Envelope Tracking PAM for Sub-6 GHz Massive MIMO Supported Base Stations). Data are contained within the article. Conflicts of Interest: The author declares no conflict of interest. References  
* [PERSON] et al. (2019) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] An 88%-Efficiency Supply Modulator Achieving 1.08 \(\upmu\)s/V Fast Transition and 100 MHz Envelope-Tracking Bandwidth for 5G New Radio RF Power Amplifier. In Proceedings of the 2019 IEEE International Solid-State Circuits Conference-(ISSCC), San Francisco, CA, USA, 17-21 February 2019; pp. 238-239. * [PERSON] et al. (2014) [PERSON]; [PERSON]; [PERSON]; [PERSON] Envelope Modulator for Multimode Transmitters with AC-Coupled Multilevel Regulators. In Proceedings of the 2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC), San Francisco, CA, USA, 9-13 February 2014; pp. 296-297. * [PERSON] et al. (2013) [PERSON]; [PERSON]; [PERSON]; [PERSON] An AC-coupled hybrid envelope modulator for HSUPA transmitters with 80% Modulator. In Proceedings of the 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers, San Francisco, CA, USA, 17-21 February 2013; pp. 364-365. * [PERSON] et al. (2012) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] A wideband CMOS/GaAs HBT envelope tracking power amplifier for 4G LTE mobile terminal applications. _IEEE Trans. Microw. Theory Tech._**2012**, _60_, 1321-1330. [CrossRef]
* [PERSON] et al. (2021) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] A 5G New Radio SAW-less RF Transmitter with a 100 MHz Envelope Tracking HPEW 2r7 Power Amplifier Module. In Proceedings of the 2021 Symposium on VLSI Circuits, Kyoto, Japan, 13-19 June 2021; pp. 1-2. * [PERSON] et al. (2018) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON]; et al. An 87.1% Efficiency RF-PA Envelope-Tracking Modulator for 80 MHz LTE-Advanced Transmitter and 31 dBm PA Output Power for HPUE in 0.153 \(\upmu\)m CMOS. In Proceedings of the 2018 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, USA, 11-15 February 2018; pp. 432-433. * [PERSON] et al. (2005) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Design of wide-bandwidth envelope-tracking power amplifiers for OFDM applications. _IEEE Trans. Microw.