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Technology Stocks : Nokia (NOK) -- Ignore unavailable to you. Want to Upgrade?

To: carranza2 who wrote (17444)	12/19/2001 4:28:18 PM
From: 49thMIMOMander	Respond to of 34857

Direct modulation and-or demodulation is the more original term,that is, one goes directly from the carrier frequency in the antenna to the so called baseband, without an Intermediate (carrier) Frequency. (Zero Intermediate Frequency) (Base Band, BB as in COBBA, when the signal is where it once was produced, like microphone-audio-radio-audio-loudspeaker) In finnish "suora (de-)modulaatio". Minor advice in researching components of handsets - search for the antenna - find the duplex,diplex or whatever filter or thingy, doing some basic separation of what is sent and what is received (transmit, receive, tx,rx) - tx: find the PA (Power Amplifier), the thing which produces the 0.x Watts of power - rx: find some small LNAs (Low Noice Amplifiers), the first path in the receive path - find RF-filters for both tx and rx paths, larger square metallic boxes, ceramic SAW filters (Surface Acoustic Wave), a minimum of one box per tx and rx for every carrier frequency used, 2 or 3-"mode", like 450,850,900,180,1900MHz) - find both mixers (modulators and demodulators) for both tx and rx paths (usually very small or integrated) - if there are more SAW filters, then there is an Intermediat Frequency, with mixers, amplifiers, lots of stuff around them. In general the tx and the rx parts are occupying the same isolated area close to the antenna, but are then separated. That is, all these RF-IF-BB parts are isolated from each other by metallic "walls" ( assuming you have removed the lids) As a result it looks something like this ============= ----- antenna --- diplex filter - PA and LNA amplifiers - tx and rx RF filters ==conductive,isolating wall= tx parts \|\| rx parts ================== possible IF parts for both ================== tx BB \|\| rx BB Analog DA-AD part ============== DSP part ================== the user interface, memory display, keyboard circuits,etc ------------------------------------ Battery charger and power control ----------------------------------- battery and power cord connector However, those who have to use to circuit boards must add some 20-40% to the costs and work harder on isolating the different parts. Ilmarinen Nokia has some other smart trucos in their newest model, but I won\t go into them. Btw, the first, now ancient, Nokia ZIF phone did not have SAW filters. Bottom line, did you see the text on "direct modulation and demodulation" for that old kiddy phone??