Adjacent channel power and error-vector magnitude performance of reduced complexity CALLUM systems

The combined analogue locked-loop universal modulator (CALLUM) is a power e fficient linear RF transmitter based on the LINC principle (linear amplific ation with nonlinear components). The system provides both upconversion and amplification of a baseband input signal, within a closed-loop control sch eme. The variant known as CALLUM1 is optimal, but difficult to implement pr actically. Simplifications to this system can be made so that the processin g requirement is reduced. The simulated performance of these systems is com pared to that of CALLUM1, in terms of adjacent channel power (ACP) and erro r-vector magnitude (EVMrms), in response to a TETRA (terrestrial trunked ra dio) baseband modulation signal. The existing CALLUM systems and the simpli fied versions proposed in the paper meet the TETRA ACP specification of -60 dBc if enough stable loop gain can be provided.