Transcript Introduction to S

Microwaves
Dr inż. Zdzisław Pólkowski
Badea George-Cosmin
CONTENTS
•Introduction
•Definition
•Discovery
•Scattering Parameters (S-Parameters)
•Frequency Bands
•Classification
•Health Effects
•Examples
INTRODUCTION
• The term microwave refers to electromagnetic energy having a
frequency higher than 1 gigahertz (billions of cycles per second),
corresponding to wavelength shorter than 30 centimeters.
•As a consequence, practical microwave technique tends to move away
from the discrete resistors, capacitors, and inductors used with lower
frequency radio waves.
•Instead, distributed circuit elements and transmission-line theory are
more useful methods for design, analysis. Yhe term microwave generally
refers to the alternating current.
•Electromagnetic waves longer (lower frequency) than microwaves are
called “radio waves”. Electromagnetic radiation with shorter wavelengths
may be called “millimeter waves”, or t-rays.
http://searchnetworking.techtarget.com/definition/microwave
Definition
•Microwaves are a type of electromagnetic radiation, as are radio waves,
ultraviolet radiation, X-rays and gamma-rays. Microwaves have a range of
applications, including communications, radar and, perhaps best known
by most people, cooking.
• Microwaves: 30cm – 1cm (centimeter waves):
• Millimeter waves: 10mm – 1mm:
http://www.livescience.com/50259-microwaves.html
Discovery
• The existence of electromagnetic waves, of which microwaves are part
of the frequency spectrum, was predicted by James Clerk Maxwell in 1864
from his equations.
•Heinrich Hertz was the first to demonstrate the existence of
electromagnetic waves by building an apparatus that produced and
detected microwaves in the UHF region.
•J.C.Bose publicly demonstrated radio control of a bell using millimeter
wavelengths, and conducted research into the propagation of microwaves.
http://www.stmary.ws/HighSchool/Physics/micro_1.htm
Scattering
Parameters
Scattering Parameters
• Content:
• History of S-parameters;
• Introduction to S-parameters;
• Definition of S-parameters;
• Types of S-parameters.
http://www.microwaves101.com/encyclopedias/438-s-parameters-microwave-encyclopedia-microwaves101-com
Scattering Parameters
 History of S-parameters :
• S-parameters refer to the scattering matrix;
• The concept was first popularized around the time that Kaneyuke
Kurokawa of Bell Labs wrote his 1965 IEEE article Power Waves and the
Scattering Matrix.
• We'll also admit that there are several papers that predate Kurokawa's
from the 1950s, one good early work was written by E. M. Matthews, Jr.,
of Sperry Gyroscope Company, titled The Use of Scattering Matrices in
Microwave Circuits.
•Collin's book is extensively annotated, including an author index, which
reads like a Who's Who of electromagnetic theory for the first half of the
twentieth century.
http://www.microwaves101.com/encyclopedias/438-s-parameters-microwave-encyclopedia-microwaves101-com
Scattering Parameters
 Introduction to S-parameters :
• Before we get into the math, let's define a few things you need to know
about S-parameters.
• The scattering matrix is a mathematical construct that quantifies how
RF energy propagates through a multi-port network. The S-matrix is
what allows us to accurately describe the properties of incredibly
complicated networks as simple "black boxes".
 Here are the S-matrices for one, two and
three-port networks:
https://www.cefns.nau.edu/~pgf/ETM/pdf/
S-parameters.pdf
http://www.microwaves101.com/encyclopedias/438-s-parameters-microwave-encyclopedia-microwaves101-com
Scattering Parameters
 Definition of S-parameters
• S-parameters describe the response of an N-port network to voltage
signals at each port. The first number in the subscript refers to the
responding port, while the second number refers to the incident port.
•Let's examine a two-port network. The
incident voltage at each port is denoted
by "a", while the voltage leaving a port
is denoted by "b". Don't get all hung up
on how two voltages can occur at the
same node, think of them as traveling
in opposite directions!
• If we assume that each port is
terminated in impedance Z0, we can
define the four S-parameters of the 2port as:
https://www.cefns.nau.edu/~pgf/ETM/pdf/S-parameters.pdf
Scattering Parameters
 Types of S-parameters :
• When we are talking about networks that can be described with Sparameters, we are usually talking about single-frequency networks:
 Small signal S-parameters: are what we are talking about 99% of the
time. We mean that the signals have only linear effects on the network,
small enough so that gain compression does not take place.
 Large signal S-parameters: are more complicated. In this case, the Smatrix will vary with input signal strength.
 Mixed-mode S-parameters: refer to a special case of analyzing
balanced circuits.
 Pulsed S-parameters: are measured on power devices so that an
accurate representation is captured before the device heats up.
 Cold S-parameters: we refer to active devices that are not powered up
http://www.microwaves101.com/encyclopedias/438-s-parameters-microwave-encyclopedia-microwaves101-com
Frequency Bands
http://ricksturdivant.com/packagingatmicrowave/
Classification
1. According to distance between the points to be connected
•Long-haul microwave links (20 to 50 km, in certain cases even more)
•Short-haul microwave links (a few hundred metres up to 20 km)
2. According to transmission capacity and multiplex process
•Up to around 34 Mbit/s (classical PDH)
•Up to around 200 Mbit/s per system (Ethernet or mixed with PDH)
•Up to n times 155 Mbit/s (SDH)
3. According to frequency band used
•6 to 8 GHz (long-haul microwave links of up to over 50 km, for the
highest possible capacity)
•11 to 15 GHz (medium-haul distances of 10 to 20 km)
•18 to 38 GHz (short-haul microwave links between 1 and 10 km)
•52 GHz and more (shortest distances of all, up to around 1 km)
4. According to equipment technology
•Classical indoor equipment with waveguide between equipment and
antenna
•Splitting equipment (microwave link system with the indoor and
outdoor unit separated)
http://www.microwave-planning.com/wissen/wissen02.htm
Health Effects
• Health effects of environmental electromagnetic fields;
• Antibody responses of mice exposed to low-power microwaves;
•Cancer morbidity in subjects occupationally exposed to high
frequency electomagnetic radiation;
•Accelerated development of spontaneous skin cancer in mice
exposed to 2350 MHz microwave radiation ;
•It is powerful and effects human skin very badly.
http://www.who.int/peh-emf/publications/facts/info_microwaves/en/
Examples
Examples
• COMMUNICATION
• ACTIVE REMOTE SENSING
• PASIVE REMOTE SENSING
• NAVIGATION
• POWER
Uses: COMMUNICATION
• Microwaves are used for communication, as they are easier to control
because small antennas could direct these waves very easily.
•These waves cn cover long distances very easily, about 4 miles.
•Before the invention of optical fibres, microwaves were used for
communication, as they travel with speed of light.
•Microwaves helps in wireless LAN protocol Helps in MAN.
•Cable TV and internet access on coaxial as well as broadcast televisions
uses microwave of lower frequencies.
•Mobile phones network and GSM also uses microwaves of lower
frequencies.
•Microwave radio is used for broadcast and telecommunication due to its
high frequencies.
•Microwaves are used in television news to transmit the signal from a
remote location to a television stations.
•Used for communication satellites.
•They are used for those areas where cables wire could not be used.
http://www.scienceclarified.com/Ma-Mu/Microwave-Communication.html
Uses: ACTIVE REMOTE SENSING
• Radar uses microwave radiation to detect the range, speed and other
characteristics of remote objects;
• Now radar is widely used for applications such as air traffic control,
navigation of ships, and speed limit enforcement;
• A Gunn diode oscillator and waveguide are used as a motion detector for
automatic door openers;
• Most radio astronomy uses microwaves.
http://ntrs.nasa.gov/search.jsp?R=19850058641
Uses: PASIVE REMOTE SENSING
• Passive remote sensing refers to the sensing of electromagnetic waves
that did not originate from the satellite or instrument itself. The sensor is
merely a passive observer collecting electromagnetic radiation.
• Passive remote sensing instruments onboard satellites have
revolutionized weather forecasting by providing a global view of weather
patterns and surface temperatures.
•A microwave imager onboard NASA's Tropical Rainfall Measuring
Mission (TRMM) can capture data from underneath storm clouds to reveal
the underlying rain structure.
http://missionscience.nasa.gov/ems/06_microwaves.html
Uses: NAVIGATION
• Global Navigation Satellite Systems (GNSS) including the American
Global Positioning
•System (GPS);
• Broadcast navigational signals in various bands between about is 1.2
GHz and 1.6 GHz
http://europepmc.org/abstract/med/11707987
Uses: POWER
• A microwave oven passes (non-ionizing) microwave radiation (at a
frequency near 2.45GHz) through food, causing dielectric heating by
absorption of energy in the water, fats and sugar contained in the food;
• Microwave heating is used in industrial processes for drying and curing
products;
•Many semiconductor processing techniques use microwaves to generate
plasma;
• Microwaves can be used to transmit power over long distances. NASA
worked in the 1970s and early 1980s to research the possibillites of using
Solar power satellite (SPS) systems with large solar arrays that would
bean power down to the Earth’s surface via microwaves.
http://hypertextbook.com/facts/2007/TatyanaNektalova.shtml