Lesson 7 Intro to Microwaves

Microwave

An electromagnetic wave with a relatively short wavelength and high frequency.

Microwave Frequencies

Range from 300 MHz to 300 GHz, including specific frequencies like L-band, S-band, and others.

Skin Effect

The concept that high-frequency energy travels only on the outside skin of a conductor.

Characteristic Impedance

The inherent opposition that a transmission line offers to the flow of an electromagnetic wave.

Decibel (dB)

A relative term with no units, representing the ratio of two powers, indicating gain or loss.

Impedance Matching

The process of making the load impedance equal to the characteristic impedance of the transmission line to prevent signal reflections.

Multiple Accessing

Techniques allowing multiple users to share the same communication channel without interference.

Frequency Division Multiple Access (FDMA)

Each user is assigned a separate frequency band within the available spectrum.

Time Division Multiple Access (TDMA)

Users share the same frequency but transmit in different time slots.

Code Division Multiple Access (CDMA)

Users share the same frequency and time but are assigned unique codes to separate signals.

300 MHz to 300 GHz

Microwave frequencies range from

microwaves

3-30 GHz

millimeter waves

30-300 ghz

L BAND

used for aviation, sate comms, and GPS

S band

used for radar, weather monitoring and WiFi

C band

used for satellite comms and radar

X band

used for military radar and satellite comms

Ku band

satellite Tv and Communications

K band

radar and scientific applications

Ka

HF satellite communication

millimeter waves

5g networks and advanced radar

Microwave Centrifugal Force

The force that keeps the energy from penetrating the surface of the transmission line and instead makes it follow a path along the skin of the line rather than down into the entire cross- sectional area, as in LF circuits

Reflection Coeffiecient

quantifies the fraction of the incident voltage wave that is reflected due to impedance mismatch

Return loss

measures how much power is reflected back from the load in decibels (dB)

Voltage Standing Wave Ratio (VSWR)

describes how much standing wave interference occurs due to reflections: