Synthesizer And Rf Control - Nokia RH-9 Series Ccs Technical Documentation

System module & ui, transceivers

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Service tools (22 pages)

Disassembly instructions manual (8 pages)

Service manual (19 pages)

Table Of Contents

Table of Contents

RH-9

System Module & UI

The outputs from the individual PA chains is feed to individual couplers, that means one

for GSM and one for PCN, before entering the RX/TX switch. The harmonics from the PA

is filtered by filters located in the RX/TX switch.

The output sample from the directional coupler's is rectified by a dual shottky-diode,

with common output, and filtered before being fed to the error amplifier in Mjoelner

which again is controlling the gain of the individual PA chain relative to the TXC voltage.

Power control

The detected voltage is compared in the error-amplifier in Mjoelner to TXC- voltage,

which is generated by a DA-converter in BB. TXC has got a raised cosine form (cos

function), which reduces switching transients, when ramping power up and down.

Because the dynamic range of the detector is not wide enough to control the power

(actually RF output voltage) over the whole range, there is a control named TXP to work

below detectable levels. Burst ramping is enabled and set to rise with TXP until the out-

put level is high enough for the feedback loop to work. The output of the loop error

amplifier controls the PA output level via the gain-control pin in the PA to the desired

output level and the burst has are thereby shaped by the waveform of the TXC-ramp.

Because feedback loops could be unstable, this loop is compensated with a dominating

pole. This pole decreases gain on higher frequencies to get phase margins high enough.

Also this pole filter out the noise which is coming from TXC line. Each band has its own

control line from the loop amplifier.

To mecanial att.sw.

Ant.switch

47R

Vant_1800

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