The RF wireless signal travels as an electromagnetic wave with electric field E and magnetic field B perpendicular to the propagation direction, determined by the right-hand rule.

Explain scattering and diffraction of electromagnetic waves on rough surfaces and through media, and illustrate absorption by walls and atmospheric water vapor, including the RF shadow region.

Explore multipath propagation in wireless links, where direct and reflected paths create delay spread, leading to constructive and destructive interference, intersymbol interference, and small-scale fading and large-scale fading.

Explore ground wave propagation up to 3 MHz, its surface diffraction allowing long-distance communication, and the requirement for long antennas, with references to AM radio broadcasts and maritime radio navigation.

Tropospheric communication in VHF and UHF uses moisture gradients and temperature inversions to refract RF signals via ducting, enabling non line of sight propagation for TV, FM, and microwave links.

Modulation moves the mic signal to the carrier frequency; RF transmitter and RF receiver carry it over the air via the antenna, while demodulation returns it to zero hertz.

Explains how a carrier sinusoidal wave is modulated by a message signal using amplitude, frequency, or phase modulation, showing how carrier amplitude, frequency, and phase vary with the message.

Explain how modulation shifts a signal’s center frequency to a carrier, enabling smaller antennas and allowing multiple signals to share a bandwidth via frequency division multiplexing.

Explore frequency shift keying, where the carrier frequency encodes binary 1s and 0s with high and low frequencies, while amplitude and phase remain constant, improving robustness to amplitude noise.

Explain phase shift keying, a modulation scheme that encodes binary bits by changing the carrier phase. Identify ones with 180-degree phase shifts, zeros with no phase change, using coherent detection.

Amplitude phase keying blends amplitude and phase modulation to yield 16 symbol points, delivering four bits per symbol and higher data rates in smaller bandwidth, known as quadrature amplitude modulation.

Antennas on both transmitter and receiver sides convert RF signals between electrical and electromagnetic forms, while the isotropic radiator provides the reference to compare real antenna gain.

Define watts, milliwatts, and decibel milliwatts. Relate power to voltage times current, use 1 volt with 1 ampere to show 1 watt and milliwatt as a thousandth of a watt.

Convert milliwatts to dBm using the log base 10 formula; this logarithmic scale makes 1 mW equal 0 dBm and 1 MW equal 90 dBm.

Explore how the decibel compares relative power levels, signaling gain or attenuation in devices like amplifiers and during free space path loss between mobile and base station.

Explore equivalent isotropically radiated power (EIRP) by equating transmit power plus antenna gain minus cable loss, illustrated with isotropic and directional antennas to show equal coverage.

Free space path loss attenuates signal power as electromagnetic waves spread in free space; it increases logarithmically with distance and frequency, with double distance causing about six decibels of loss.

Identify the noise floor as background noise in a communication system, shaped by transmitter, receiver, environment, and sources like electronic devices, RF interference, and thermal and natural noise, affecting demodulation.

Explain how the signal-to-noise ratio compares signal power to noise power in watts and converts to db via 10 log10; increase in snr yields clearer signals and fewer errors.

Explore the received signal strength indicator (rsi), a dbm-based measure of incoming rf power that ignores noise floor and ranges from -30 to -85 dbm, with vendor variation.

Calculate the received power in a microwave link by adding transmitter power and antenna gains and subtracting cable losses and free-space path loss, ensuring it exceeds the receiver sensitivity.

Explain impedance, resistance to rf signal flow, and show how matching a 50 ohm transmitter, cable, and antenna minimizes reflected power, while defining return loss and voltage standing wave ratio.

An RF transmitter sends an AC signal to the antenna, generating an electromagnetic wave at the same frequency that travels at light speed and induces current in the receiving antenna.

Antenna polarization describes the orientation of the electric field in the electromagnetic wave, typically vertical or horizontal; circular polarization via helical antennas enables reception by vertical, horizontal, or circular antennas.

Explore the half power beam width of an antenna, defined by the -3 decibels points from the main lobe peak, and learn horizontal and vertical measurements on polar plots.

Explore passive gain as the antenna's focus of energy into a beam, increasing range with higher gain and narrower beam width, exemplified when a 100 milliwatt input becomes 200 milliwatt.

Examine omnidirectional antennas with a 360-degree horizontal beam, producing circular top-view radiation patterns; increasing gain flattens the vertical pattern and extends coverage.

Highly directional antennas use parabolic dishes for long-range point-to-point links, delivering high gain with a narrow beam width of 3–15 degrees; grid dishes reduce wind loading and enable wind-resistant installations.

Explore diversity techniques in wireless systems that improve signal reliability amid multipath fading, enabling higher data rates by sending the same information over multiple paths.

Describe transmit and received diversity with multiple antennas, how the receiver combines signals to improve quality and reliability, and compare selection, equal gain, maximum ratio, and switching diversity.

Mimo increases wireless throughput using multiple input, multiple output to transmit data layers over the same channels with multiple antennas at the transmitter and receiver, limited by antenna count.

Explore how antenna arrays enable beamforming to boost data rates in wireless systems. Adjust phase and amplitude across array elements to steer a directional beam and enhance signal quality.