This is a type of ultra wideband tags that does not have its built-in power source. Instead, it relies greatly on the power that is provided by an external ultra wideband uwb reader or ‘interrogator.’ This passive ultra wideband tag is smaller yet very useful at the same time. A passive UWB tag is commonly used for access control. They are also helpful in inventory tracking and material flow. This real-time location system is cheaper too. Which is why it is more preferred by many companies compared to an active UWB tag.