Where do Digital wireless signals fit into the E.M. Spectrum?

Question

Im familiar with AM & FM modulation and how the signals have a wavelength/ freq. in the electromagnetic spectrum.

Where do digital transmissions fit into the spectrum? Im somewhat familiar with "Pulse"WidthModulation and squarewaves. Where do the "Pulses" in pwm fit into the spectrum. Does UHF, VHF, HF... have any relevence in wireless digital.

Answer 1

They operate near the top of the UHF band (300 - 3000 MHz).

Some mobile operators use a band around 1850 - 2000  MHz  others use a band around 2100 - 2200 MHz.

Pulses are simply a way of turning on an off the carrier.  Unfortunately turning a carrier on and off with a square-wave creates lots of harmonics which increases the bandwidth of the signal, but through careful encoding of the pulses a pseudo random bit-stream can be created which makes the spectrum of the modulated digital comm. signal look like background noise.

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Answer 2

they can fit in anywhere they are put. AM, FM, and PWM are ways of encoding information that is transmitted. UHF, VHF, ULF etc, are different types of carrier frequencies. that being said, all ways of encoding can be used on all types of carrier frequencies. Ethernet and cdma are also ways of encoding info. ethernet was originally used with a copper medium for tranmition and CDMA was used for broadcast tranmition. now both can be transmittied through either air, copper, fiber media, ect.

if you would like to do a little research look up: CMDA, PCS and GSM for examples of digital encoding. also look up the ISO's seven layers of a program. your question deals with (i think) network layer 3 (digital question) and layer one (physical transmition). each layer is said to be transparent to the others so when the data is encoded, the system encoding the data doesnt change the encoding to fit the physical layer in any way. it is worth noting that this response will reach you via a digital signal with a carrier of 2.4GHz using IEEE 802.11G for encoding (wireless router).