How does the power class of a 5G FR2 UE affect the number of antenna elements required?

The power class of a 5G FR2 UE determines the maximum EIRP (Effective Isotropic Radiated Power) that the device must achieve, which directly determines the number of antenna elements required in the phased array, because: EIRP = P_element × N × G_element × array_efficiency, where P_element is the output power per element, N is the number of elements, and G_element is the single element gain. More elements provide more EIRP through both array gain (coherent combining of N elements provides N× power gain) and element gain (the array aperture increases with N). 3GPP defines the FR2 UE power classes: Power Class 1 (PC1): EIRP = 55 dBm (316 W). Used for Customer Premises Equipment (CPE), Fixed Wireless Access (FWA). Requires: 64-256 antenna elements with PA output of 10-15 dBm per element. Achievable with large arrays on CPE devices (no size constraint). Power Class 2 (PC2): EIRP = 43 dBm (20 W). Used for vehicular and laptop devices. Requires: 16-32 antenna elements with PA output of 10-13 dBm per element. Power Class 3 (PC3): EIRP = 23 dBm (200 mW). Used for smartphones. The default power class. Requires: 4-8 antenna elements with PA output of 5-10 dBm per element. This is the minimum antenna count for a smartphone implementation. Power Class 4 (PC4): EIRP = 34 dBm (2.5 W). The most common smartphone class in practice. Requires: 8-16 antenna elements with PA output of 10-12 dBm per element. Most 5G mmWave smartphones implement PC4 with 2-4 antenna modules, each containing 4-8 elements.