Error vector magnitude (EVM) measurements for GSM/EDGE applications revised under production conditions

A main concern in the testing of systems fulfilling the enhanced general packet radio service (EGPRS) requirements is the proper measurement of the error vector magnitude (EVM) for the implemented 8PSK modulator. However, handsets supporting EGPRS also incorporate a GMSK modulator and hence, in order to reduce computing time on the production tester by more than an order of magnitude, this paper suggests obtaining part of the data needed for the 8PSK modulator´s EVM calculations during the phase error measurements of the GMSK modulator. More fundamentally, this approach can be applied to any mixed-signal modulator embodying a phase-only modulator in parallel with a modulator employing a phase and amplitude modulation scheme.