Mohammed Aldhaheri
EE311 Project – Spring 2014
Microwaves
Microwaves are considered one of the most important topics in
electromagnetic because it has many advantages and it makes our life much
easier. The use of microwaves has greatly expanded and we can see that in many
microwave appliances that we use usually in our life such as the microwave
oven, satellite television receiver, and the police radar. Microwaves are EM
waves “with wavelengths ranging from as long as one meter to as short as one
millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz)”
(Wikipedia) and 1000 GHz. Also, using microwaves into the communication
systems are so beneficial in finding solutions for communications that include
wide available bandwidths and directive properties of short wavelengths.
Therefore, microwaves could be more useful than other types of wave because of
the many features that other waves do not have. As other electromagnetic
systems, a microwave system consists of a transmitter and a receiver. As it is
mentioned in our class’s textbook, a microwave network (see image 1) has
several components such as coaxial cables, resonators, waveguide sections,
antennas, terminators, attenuators, directional couplers, isolators, circulators,
and filters. Each of these components has their own role to make a microwave
network works and useful. In this paper, I am going to focus on some of the
advantages of microwaves such as the very useful microwave appliances, and I
am going to show some equations about microwave network.
Image 1: Microwave Network
Some of the very useful microwave appliances are microwave oven and
radar. First, the use of microwave oven is almost in every house or restaurant.
Microwave energy provides heating properties that make a microwave oven (see
image 2) very useful for rapid heating of food. A microwave oven heats food by
“ bombarding it with electromagnetic radiation in the microwave
spectrum causing polarized molecules in the food to rotate and build up thermal
energy in a process known as dielectric heating.” (Wikipedia).
Image 2: Microwave Oven
Second, radar is a very useful and common application of microwaves. There are
many useful uses of radar such as detecting aircraft, observing weather patterns,
and determining speeds of cars. As it is mentioned in our class’s textbook,
microwave is useful in radar applications because it provides a better resolution
at higher frequencies.
Relating to microwave network, S-parameters are useful in analyzing
microwave circuits that have input and output with variables at high frequencies
than voltage and current. “S-parameters describe the response of an N-port
network and the most common "N-port" in microwaves are one-ports and twoports.” (microwaves101.com). For example, a two-port S-parameters:
The matrix form of these two-port S-parameters is:
(a1 and a2 represents the incident waves, while b1 and b2 represent the
reflected waves). Also, the input and output reflection coefficients are:
Where ΓL=(ZL-Z0)/(ZL+Z0) and Γg=(Zg-Z0)/(Zg+Z0).
In conclusion, microwaves are very useful waves that have many features
that other waves do not have. Microwaves “are EM waves whose frequencies
range from approximately 300 MHz to 1000 GHz” (our class’s textbook). There
are many useful microwave appliances that make our life much easier such as
microwave oven and radars (radars for detecting aircraft, observing weather
patterns, and determining speeds of cars). Moreover, there is a very useful
method, which is called S-parameters and defined in terms of wave variables,
that helps us in analyzing microwave circuits that have input and output with
variables at high frequencies than voltage and current.
References:
http://en.wikipedia.org/wiki/Microwave
http://scarletwireless.com/solutions-design-microwave-network.html
Elements of Electromagnetics, M. Sadiku, 5th Ed.
http://www.dreamstime.com/royalty-free-stock-photography-microwave-ovenvector-diagram-how-does-work-kitchen-appliance-heats-food-bombardingimage33291207
http://en.wikipedia.org/wiki/Microwave_oven
http://www.microwaves101.com/encyclopedia/sparameters.cfm
http://www.ece.rutgers.edu/~orfanidi/ewa/ch13.pdf