Satellite Communication and Radio Wave Fundamentals
Iridium Satellite Constellation
Iridium is the name of a constellation of 66 communications satellites orbiting the Earth in 6 low Earth orbits (LEO), each consisting of 11 evenly spaced satellites. Its name comes from the element Iridium, which has an atomic number of 77, equivalent to the number of satellites in the constellation, including its original design.
Radio Wave Fundamentals
Frequency
Frequency is a measure that is generally used to indicate the number of repetitions of any phenomenon or periodic occurrence per unit of time.
Channel
Channel is the conduit through which signals travel, carrying information between the sender and receiver. It is also commonly referred to as a data channel.
Amplitude
Amplitude is the maximum value of a wave.
Wavelength
Wavelength is the distance between two consecutive equal points on a wave.
Frequency and Waves
Frequency is the number of cycles a wave makes in one second. It is measured in Hertz (Hz).
A wave is a disturbance that propagates in a medium, characterized by its wavelength, amplitude, and frequency. The parts of a wave are: amplitude, wavelength, period, and frequency.
Transmission Medium
Transmission medium is the channel that allows the transmission of information between two terminals in a transmission system.
AM (Amplitude Modulation)
AM is a linear modulation type that consists of varying the amplitude of the carrier wave so that it changes in accordance with the changes in the level of the modulating signal, which is the information being transmitted.
FM (Frequency Modulation)
FM is an angular modulation that transmits information via a carrier wave by varying its frequency (contrast this with amplitude modulation or AM, where the wave amplitude is varied while its frequency remains constant).
Satellites and Other Radio Concepts
Moon
The Moon is a celestial body that orbits a planet or other smaller body, which is called the “primary.” It does not have its own light, unlike planets.
Artificial Satellites
There are also artificial satellites. Artificial satellites are objects put into orbit by human intervention, created by humans.
Repeater
A repeater is a special type of base station located at some distance from the base of operations of the system. It also consists of a transmitter and a receiver, but its manner of operation varies.
Basic Radio
Basic Radio is a type of community radio.
Multiplexer
A multiplexer is a device that can receive and transmit multiple inputs through a shared transmission medium. It does this by dividing the transmission medium into multiple channels so that multiple nodes can communicate simultaneously.
Demultiplexer
A demultiplexer is a combinational circuit that has an input of data d and n control inputs used to select one of the 2n outputs, which must output the data present in the input.
Bandwidth
Bandwidth is the width, measured in Hz, of the frequency range in which most of the signal strength is concentrated. It can be calculated from a temporal signal by Fourier analysis. Frequencies outside this range are also called effective frequencies.
Duplex
Duplex is the ability of a device to work and communicate in both directions (receive/send in the case of a modem). There are two types of duplex:
- Half-duplex: It can receive or send, but not simultaneously.
- Full-duplex: It can receive and send simultaneously.
Carrier Wave
A carrier wave is an analog signal that can be used to transmit information. The information is incorporated into the carrier using frequency modulation (FM) or amplitude modulation (AM).
Key Figures in Radio Wave History
John Hertz
John Hertz was a Slovak-American businessman, owner of thoroughbred racehorses, and philanthropist. Born in the village of Vrútky, Slovakia, part of the Austro-Hungarian Empire before, his family emigrated to the United States at the age of 5.
James Clerk Maxwell
James Clerk Maxwell (Edinburgh, June 13, 1831 – Cambridge, UK, November 5, 1879) was a Scottish physicist best known for having developed the classical electromagnetic theory, synthesizing all previous observations, experiments, and laws on electricity, magnetism, and even optics, into a consistent theory. Maxwell’s equations showed that electricity, magnetism, and even light are manifestations of the same phenomenon: the electromagnetic field.