roup, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Measured (AM/AM) Mathematical fit Source Power (dBm) Measured (AM/PM) Mathematical fit Source Power (dBm) Figure 6.24 Measured AM/AM, AM/PM (asterisks), and model fit (solid) versus source power (decibels of measured power [dBm]) [19]. emissions. The latter can lead to violation of the spectral emission mask (SEM) and adjacent channel leakage ratio (ACLR) requirements. The trade-off among the implementation costs, the impact of the imperfections on achieving high perfor- mance, and meeting the requirements is the prominent issue. The nonlinear power amplifier is usually characterized by AM/AM (amplitude to amplitude) and AM/PM (amplitude to phase) distortion curves [18]. The AM/ AM and AM/PM characteristics used in this study, represented as S21 and LS21, are shown in Figure 6.24. These characteristics are based on the measurement result of a UE wideband CDMA power amplifier (PA) module [19]. This PA has a good compromise between linearity and power efficiency for varying envelope input sig- nals. From Figure 6 24, the power amplifier has a 27-dB linear gain and 1-dB compression point at +6.1-dBm input power. Error vector magnitude (EVM) is commonly used as a direct measure of the transmitter signal quality, in particular when related to any RF hardware imperfec- tions in the system. EVM, however, does not cover the disturbance caused to other users, where ACLR must be used as a measure [20]. The EVM is a measure of the © 2009 by Taylor & Francis Group, LLC Single-Carrier Transmission for UTRA LTE Uplink 16QAM OFDM QPSK OFDM 16QAM SCFDMA QPSK SC-FDMA 1 dB Compression point Pin (dBm) Figure 6.25 EVM results for nonlinear PA. difference between the measured and the reference signals. In LTE, the EVM is measured in the constellation domain [21-23] rather than in the time domain as for the previous UTRA specifications [24]. This approach allows pre-and post-FFT time/frequency synchronization and amplitude/phase correction to be included in the freq