RF descriptionRF introductionThis section describes the RF modules of the RM-91/92 engine. RM-92 uses RF ASIC N7500 and RM-91 uses RFASIC N7505.The RF is controlled by digital baseband circuitry via a serial bus (RFBus). The RFBus is for mode selection,frequency synthesizer control, RX AGC setting, RF regulator control, TX power control loop and PA bias control.In addition to RFBus there are also several other interface signals coming from BB. TX power control (TXC),VCTCXO frequency control (AFC) and some other control signals (voltage and current references, WCDMA TXpower detection, PA combination detection).RegulatorsAll RF regulators, except one, are located in the EM ASIC N2200 in the baseband section or in the RF ASIC ofthe device. The discreet regulator, N7541, feeds the WCDMA PA. The EM ASIC N2200 has three regulators forRF:• 2.5 V regulator VXO• 4.75 V regulator VCP (VCP1 & VCP2)• 1.35 V regulator, VB_EXT, which is the reference voltage.Block diagramsFigure 111 RF block diagram RM-92 using RF ASIC N7500RM-91; RM-92Nokia Customer Care System ModulePage 9 –42 COMPANY CONFIDENTIAL Issue 1Copyright © 2006 Nokia. All rights reserved.
