Siemens A35 Repair Documentation

Also see for A35: User guide Manual

Contents

V1.0 Page 12 of 38 ICM MP CC STA35-A36-A40 Company Confidential 09/014.4 Receivers4.4.1 Receiver: GSM900/1800 Diplexer > Filter > LNA > MixerFrom the antenna switch up to the IF-Mixer, the GSM1800 receiver circuit Notesconsists of:a) a ceramic front end filter (Z555)b) a LNA (Low Noise Amplifier D550)c) and a subsequent discrete distortion LC-high-pass-filter.For GSM900 the signal flow is as follows: From the antenna switch, via a SAW filter(Z556), through the LNA (D550) and a discrete distortion LC-low-pass-filter to theIF-Mixer..The amplification of both LNA´s is approx. 20dB with a matched 50 ohm output.The LNA is switched “On” with the signal LNAON (SMARTI pin 36).For switching between GSM1800 and GSM900 the signal BSW is generated fromthe (SMARTI pin 37).The signal LNAG (SMARTI pin 33) is in use, if the received signal level is too high.with LNAG “active”, the LNA reduces the incoming signal in one step by 20dBThe non-symmetrical LNA output is connected to the IF mixer via a discretebalancing and adaptation circuit. This circuit converts the asymmetricalsignal into a symmetrical signal.The required voltage VCC2_8 is provided by N4304411441244134414