and NR-DC between FR1 and FR2 (e.g. DC_n77A-n257A). Other sources of MSD due to harmonic mixing and due to Rx band Tx band Tx band Rx band TDD band e.g. n77 LTE NR UL RB UL RB PCCPCC LTE NR LTE PCC NR PCC 1950 MHz 2140 MHz 4090 MHz ~30 dB MSD Tx band Rx band Tx band Rx band TDD band e.g. n77 TDD band e.g. n257 UL RB UL RB UL RB LTE PCC NR PCC NR PCC 1950 MHz 2140 MHz 4090 MHz 29300 MHz ~30 dB MSD Figure 12.18 Examples of intra- and inter-band EN-DC configurations: (a) FDD intra-band contiguous, (b) inter-band within FR1 (two bands), (c) intra-band non-contiguous, (d) inter-band including FR1 and FR2 (three bands). 12 5G RF Design Challenges cross-band isolation are not covered in this section but are part of the REFSENS exceptions in the standard. Overall, it is easy to understand that EN-DC induces a large expansion of conformance test cases and test time since every MSD test point must be tested. 12.5.4.3 Example of MSD/A-MPR/MPR Challenge with DC_(n)71AA The example of FDD intra-band contiguous EN-DC operation in Band 71, denoted DC_(n)71AA, best illustrates both MSD and A-MPR challenges. Due to the uncoor- dinated operation of the LTE and 5G schedulers, the UE may be operated across all possible RB offset positions and RB lengths. Figure 12.19 shows spectral measurements collected at the power amplifier output port for two RB allocations: on the left, the LTE and RB allocations are nearly contiguous, the LTE RB being transmitted at their highest offset position, and the NR RB at their lowest. In this case, the modulated waveforms exhibit near-single-carrier behavior, where the LTE anchor point suffers from low self-desensitization as the transmitter interference is dominated by its 1/f noise and not the IMD products, resulting in less than 2 dB MSD. In Figure 12.19 (right), the RB allocations are such that a gap is created by using the lowest offset position for the LTE RBs while keeping the 5G RB position identical to Figure 12.19 (left). The LTE and NR receive channels are now victims of IMD 9 and IMD7 prod