RF and Microwave Systems

What are RF and Microwave Systems:

Radio Frequency (RF) and Microwave RF refers to electrical systems that uses frequencies over which microwave communications can take place. The use of RF and Microwave Systems was invented in the early 1940's by Western Union. They used these systems to sent messages and to communicate across states, which made Rf and Microwave RF communication popular for the Telecommunication providers. Today microwave RF technology isn't used as often because of new communication technologies like satellite, cellular, and fiber-optic. However, a benefit of microwave RF communication is that these systems don't need running wire and the microwave equipment provides the most economical transmission method.

For more information on what RF and Microwave systems are, please see the link here: https://www.dpstele.com/network-monitoring/microwave/rf.php.

Radio Wave vs Microwave. What’s the difference and why do we care?

Radio wave frequency range from 30 Hz to 300GHz on the electromagnetic spectrum. Microwave frequency is a subset of radio wave frequency that ranges from 300MHz (1 meter wave length) to 300GHZ (1 mm wavelength). In the RF range, the lower frequency signals can pass around objects ranging from trees to hillsides, while the signals in the Microwave range require line-of-sight transmission between antennae. This is due, in part, to the wavelength, and the ability of the larger wavelength spectrum to diffract and bend the signal. Higher frequency signals simply do not diffract with the same degree of ease as the lower frequency signals.

Microwave frequency transmission is highly susceptible to atmospheric attenuation. According to Michael Steer, the author of Fundamentals of Microwave and RF Design, “RF signals in air are absorbed by molecules in the atmosphere primarily by molecular resonances such as the bending and stretching of bonds which converts EM energy into heat.” In dry air, signals up to about 60 GHz can be transmitted without much attenuation (this [60 GHz] is the resonant frequency of oxygen). However, when high moisture content is in the air such as during a good rain, signals in the GHz range can be severely attenuated by this moisture resonant frequency.

Bluetooth technology and how it falls under RF.

Similar to IR and wireless , Bluetooth is a transmitting service (GATT) which allows devices to communication with one another. Bluetooth sits of the radio frequency spectrum at 2.4GHz, utilizing oscillation in the waves to transmit characteristic packages between a peripheral device(Master/Server) and multiple client devices(such as a cellular device). To connect to a peripheral device, the client connects to a service address which the peripheral device provides. Many of these services are pre-attributed to different devices that handle specific operations, like a fitness machine or heart monitor (to see more examples, see https://www.bluetooth.com/specifications/gatt/services/)

To send the service between devices, the Bluetooth advertisement method is used, a permission based communication which allows for a peripheral to deny or notify a client, or vice versa. The advertisement is a service which is broadcasted function, which can send and receive in many different formats.

RF / Microwave Circuit Design:

The frequencies of RF and Microwave systems are high enough that the voltage on a wire cannot be treated as uniform. Because of this, RF designers must use transmission line theory to design circuits. Transmission line theory dictates that components be designed in terms of both RLC and wavelength and wires using LC-by-unit length.

The dependence on wavelength means that systems are usually designed to work with a specific frequency. If one were to design an antenna to work with wifi, that frequency would be 5Ghz (at OSU at least). A simple dipole would be ¼ wavelength: c/(4 * frequency) = 3*10^9/(4 * 5*10^9) = 0.15m

Past these general principals, circuit design branches into many different subfields. See the following links if you want to learn more!

Comprehensive guide to transmission lines

Examples of antenna types

High Speed Circuit Design (CMOS integrated circuits)