Operating Manual Vol 1 - ES Documentation

Vector ModulationSMIQ2.8 Vector ModulationIn the vector modulation mode (I/Q modulation) external modulation signals can be applied tomodulation inputs I and Q for a complex modulation of the RF carrier.SMIQI = 0.3 VQ = 0.4 VQAmplitude =2 2I + Q05 , Vx input value LEVELIFig. 2-33Example: vector modulation2 2If the I/Q modulator is driven by a constant sum vector modulation of I + Q = 05 . V the actual RFlevel corresponds to the displayed RF level. To avoid the I/Q modulator being overdriven, care shouldbe taken that the sum vector never exceeds 0.5 V when digital modulation modes with amplitudemodulation components such as QPSK are used. For full-scale input, the peak envelope power of themodulated RF signal is thus equal to the indicated LEVEL. The average power is smaller. Thedifference can be entered as an offset in the LEVEL menu.Vector modulation settings are accessible in the VECTOR MOD menu, see following page.Note: - Types of modulation VECTOR MOD and BB-AM cannot be set at the same time; theyswitch each other off.- A selectable internal calibration of the I/Q modulator allows accurate and reproduciblemeasurements to be made. The calibration routine should be called up with theCALIBRATE in the menu VECTOR MOD or UTILITIES-CALIB-VECTOR MOD aftertemperature changes of more than 5° C.1125.5555.03 2.66E-8