Radio Frequency Theory Flashcards
Attenuation
Decrease in amplitude (signal loss) as it propagates through the transmission medium.
Multipath
Radio wave takes different paths when propagating from source to destination around obstacles
Reflection
Abrupt change in direction of a signal as it bounces off an obstacle.
Refraction
Change in direction of a signal as it travels through a medium.
Diffraction
Change in direction of a signal as it bends around the edges of an obstacle.
Amplitude Shift Keying (ASK)
Amplitude modulation.
Binary 0 is represented by one amplitude and 1 a different amplitude multiplexing
Frequency Shift Keying (FSK)
This modulation technique modulates a carrier frequency to represent 1 or 0
Phase Shift Keying (PSK)
Modulates the phase of a reference signal (carrier signal)
Quadrature Amplitude Modulation (QAM)
Uses phase and amplitude modulation to increase throughput
Frequency Division Multiple Access / Frequency Division Multiplexing
Communication between devices occur on a dedicated channel
Time Division Multiple Access / Time Division Multiplexing
All communicating devices share a channel, taking time slots to send and receive.
Code Division Multiple Access
All devices communicate at the same time on the same channel, but using different encoding.
Othogonal Frequency Division Multiplexing (OFDM)
Frequency division multiplexing scheme used as a digital multi-carrier modulation method.
OFDM transmits across multiple subcarriers that are separate, closely and precisely spaced frequencies but that are considered one channel.
Direct Sequence Spread Spectrum (DSSS)
Uses a Pseudorandom - Noise Code (PN-Code) to spread the data across a range of frequencies.
Unlike Frequency Hop Spread Spectrum (FHSS), where the transmitter jumped between frequencies, DSSS is set to one channel.
Data is spread across the range of frequencies that make up the channel. This is known as data encoding.
