The IPDS Type Approval Test Set consists of an IPDS MES Protocol Tester (PTT) and an IPDS MES Physical Layer Tester (IPLT), which in turn consists of an RF Unit (RFU) and a Channel Unit (CU). It is used for development and type approval of Mobile Earth Stations (MESs) for the Inmarsat Packet Data System (IPDS).
The IPLT implements the IPDS channels at L-Band to allow communication between the Protocol Tester and the MES under test. In addition, it analyzes the characteristics of the channels received from the MES, and allows channel impairments to be introduced into the channels provided to the MES, to verify compliance with the IPDS performance specifications. The RFU interfaces to the MES at L-Band and converts the IPDS channels to and from IF. The CU modulates, demodulates, and analyzes the IF signals, and exchanges digital data with the Protocol Tester. The CU also provides an operator interface that allows the operator to control and monitor the operation of the Physical Layer Tester.