Modulation is a technique for converting one form of information to another state. This is the digital conversion to analog for transmissions over the satellite link in satellite communications. Multiple digital bits can be converted into one analog symbol in the modulation process. The reverse process is called demodulation.
Phase-Shift-Keying (PSK) is commonly used in Sat Comms (BPSK, QPSK, 8PSK, and 16APSK). PSK works by varying one or more analog signal characteristics (Amplitude, Frequency, and/or Phase). Higher density bits per symbol gives more throughput on the link but will require higher receive signal and transmit power.
Binary Phase Shift Keying (BPSK)
One symbol represents 1 bit of information (0 or 1).
Quadrature Phase Shift Keying (QPSK)
One symbol represents 2 bits of information (00, 01, 10, or 11).
8 Phase Shift Keying (8PSK)
One symbol represents 3 bits of information (000, 001 …. 110,111).
16-Ary Amplitude and Phase Shift Keying (16APSK)
One symbol represents 4 bits of information (0000, 0001 …. 1110, 1111). 16APSK requires a high signal-to-noise ratio (SNR) and will need more Tx power for/a larger dish.
