casing) and dimensions (thickness, screen size) are not favorable for the efficiency of mmWave antennas, and additional power losses on the order of 2-3 dB are often discussed. This is a big challenge to the success of mmWave in the phone as it adds to all the mobility challenges that are big and brand new for the network. In FR1, SAR considerations are the main reason for placing transmit antenna ports at the bottom of the UE, SO as to minimize head exposure during voice calls in the case of hand and head test cases. Proximity sensors are also sometimes used to back-off trans- mission power in case SAR might be violated, a scheme that is also known as Power Management UE Maximum Power Reduction (P-MPR). Unless the user is deliberately trying to cover all primary Tx/Rx and diversity Rx antennas simultaneously, it is difficult under FR1 normal cell coverage conditions to entirely block signal reception. On the other hand, hand blockage at mmWave can easily cause a 30 dB signal attenua- tion, which, considering the difficult link budget, can make mmWave more susceptible to dropping the link. Steering the beam peak away from blockage, for example, to attempt to maintain the link using a multipath reflection may not be always successful as absorp- tion on walls/buildings materials might be as detrimental as hand blockage. Even though 3GPP assumptions for SC are a compromise to accommodate single-antenna panel UEs, one common mitigation technique to cope with blockage consists in equipping the UE with a minimum of two panels, SO that it can benefit from panel switching/diversity. To 12 5G RF Design Challenges ensure maximum SC, the antenna placement strategy adopted in FR1 is no longer an option; that is, the TX antenna port can no longer be constrained to the bottom part of the smartphone. For example, the two panel placements shown in Figure 12.7 (left; Section 12.2.4.1), uses one panel located at the top-left corner, on the UE back side, while the second panel is located at bottom-right corner on the front side. Wi