When sourcing 4G antennas, you must prioritize Frequency Band Compatibility to ensure the device supports LTE bands relevant to your region (e.g., B1, B3, B7, B20 for Europe or B2, B4, B12 for North America). Key performance metrics include Gain (measured in dBi), where higher gain indicates better directional reach, and Voltage Standing Wave Ratio (VSWR), which should ideally be less than 1.5 to minimize signal reflection and power loss. Additionally, verify the Impedance (typically 50 Ohms) and the Polarization type (Vertical or Cross-polarized) to match your specific hardware requirements.