We want to discuss about role and importance of microwave in selecting for satellite . I study on optical communication that is higher frequency from microwave so i had a question can we use light wave as wave in wireless communication, i we here examine ionosphere.
We know ionosphere is a barrier in transmission of electromagnetic wave for example HF wave is called sky or skip wave, they can not pass from ionoshere and refelected beacsue total internal reflection law.
So on earth HF is popular in wifi wakie taki, it is not need satellite and rotate earth easily.
Fig1:Total internal refelection
For microwave is opposite of HF, microwave is pass effectly from ionosphere.so it is good option for communication earth and aerospace.So we know frequency 300M-300G is called microwave.Generally can be write that for wireless communication microwave is used like bluetooth,wimax and GSM,LTE... .
Band frequency of satellite is 1G-40G so we can categorize it, you can see image that describing of it.
Fig3:Band operation of satellites.
Global Positioning System (GPS) carriers and also satellite mobile phones, such as Iridium; Inmarsat providing communications at sea, land and air; WorldSpace satellite radio.
Weather radar, surface ship radar, and some communications satellites, especially those of NASA for communication with ISS and Space Shuttle. In May 2009, Inmarsat and Solaris mobile (a joint venture between Eutelsat and Astra) were awarded each a 2×15 MHz portion of the S-band by the European Commission.
Primarily used for satellite communications, for full-time satellite TV networks or raw satellite feeds. Commonly used in areas that are subject to tropical rainfall, since it is less susceptible to rainfade than Ku band (the original Telstar satellite had a transponder operating in this band, used to relay the first live transatlantic TV signal in 1962).
Primarily used by the military. Used in radar applications including continuous-wave, pulsed, single-polarisation, dual- polarisation, synthetic aperture radar and phased arrays. X-band radar frequency sub-bands are used in civil, military and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defence tracking and vehicle speed detection for law enforcement.
Used for satellite communications. In Europe, Ku-band downlink is used from 10.7 GHz to 12.75 GHz for direct broadcast satellite services, such as Astra.
Communications satellites, uplink in either the 27.5 GHz and 31 GHz bands, and high-resolution, close-range targeting radars on military aircraft .
For more info about frequency satellite see this link.
So some other solution that i think in new century,can be ligth wave or higher frequency for transition, but we can see in below image that light has some distortion,it even it other star has some light that can be affected our signal, so we should send it with more power .
Fig4: Transmission of electromagnetic waves
So using higher frequency can be bring more data rate, but i can not guess how much distortion occur and if we can use light as wireless communication. Today optical signal processing is common in optic communication,perhaps other step is wireless optic comuunication.