AN INTRODUCTION TO RADIO FREQUENCY ENGINEERING PDF
Cambridge Core - RF and Microwave Engineering - An Introduction to Radio Frequency Engineering - by Christopher Coleman. PDF; Export citation. Contents. Broadly speaking, radio frequency (RF) technology, or wireless as it is sometimes - An Introduction to Radio Frequency Engineering. It is not a practical unit for measuring communications signals. ▫ The magnitude is much too small. > Very few RF engineers outside of radio astronomy will know.
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Request PDF on ResearchGate | An Introduction to Radio Frequency Engineering | Using an easily understood approach combined with numerous worked. RF electronics deals with the generation, acquisition and manipulation of Introduction of beam-induced effects, CAS-CERN Accelerator School: Radio Frequency Engineering, wildlifeprotection.info .pdf. Cambridge University Press, , pages, ISBN: Using an easily understood approach combined with numerous worked.
It is therefore indispensable reading for advanced professionals and designers who operate at high frequencies as well as senior students who are first approaching the subject.
In , he joined the microwave department of Electtronica S. L where he was responsible for microwave designs. In his 23 years of design experience he has covered both passive and active microwave components, including filters, amplifiers, oscillators, and synthesizers. He is the author of four books including the present one as well as 12 papers.
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Skip to Main Content. Microwave and RF Engineering Author s: Roberto Sorrentino Giovanni Bianchi. In the latter case one might alternatively use the square of the magnitude signal, referred to as the intensity signal.
The random signals may include a component with some long-range organization or order. In MRI this might be the presence of either a steady or an amplitude-modulated signal, and in ultrasound the presence of a regular scattering structure. Separation of the ordered from the random components is desirable in MRI to improve signal detectablity, and in ultrasound to distinguish features of the scattering for the purpose of tissue characterization or discrimination.
In principle, this separation task is more straightforward when the rf signal is analyzed directly, and, in fact, tissue discrimination using this approach has been quite successful in the eye and in the liver. Also, it is the envelope-detected signal that is displayed in the conventional ultrasound B-scan image.
Tissue discrimination using only envelope signals has also been successful in the liver. In the course of this examination we shall uncover the stronger points of each approach. The probability-density functions pdf's required to characterize the first-order properties of these random phenomena include the circular complex Gaussian pdf, the Ray-leigh and Rician pdf's, and their generalizations to the case of organized structure.
In the s, the research on RFID started to accelerate very fast, this acceleration was driven by developers, educational institutions and commercial laboratories .
These researches had participated heavily in improving the tag hardware, RF immittance, and tag size. The key to this advancement was the use of low-voltage, low-power CMOS logic circuit. Tag memory utilized switches or wire bonds which had improved with the use of fusible link diode arrays by the end of the decade . The invention of the transistor has led the way to the current semiconductor revolution, which contributed in the development of all sectors including the digital world; RFID has got its share of this bloom.
The system contains a transmitter, receiver, and two antennas. One antenna is designated to send the RF signal, and the second to receive the tag response. Localization methods for conventional chipped tags rely mostly on the processing capabilities of the integrated circuit . The main focus of this paper is chipped RFID Localization, and more specifically the research is focusing on the Received Signal Strength technique to identify and track library objects.
Before going further on this subject; a new technical term needs to be explained; Load Modulation -which is how RFID system transfers data- the antenna uses radio frequency signal to transmit data, by modulating the amplitude of the carrier radio frequency signal to combine it with the carried signal .
Radio Frequency Propagation Made Easy
In an RFID system, load modulation procedure using subcarrier is primarily used in inductively coupled systems for data transfer between the tag and the reader .
In every chip there is a reader that powers up the tag from the energy captured by the antenna.
Receiver circuit is a key component of RFID reader, which is the main component that has been rapidly developed during recent years as shown in Fig.
RFID systems operate in a wide range of the spectrum depending on the antenna and tag design, which can range from kHz to microwave frequencies 5. Table 1 categorizes the frequencies used in RFID with example uses, advantages and disadvantages of using each frequency band.
The first category is Near Field magnetic induction. The second type is Far-Field electromagnetic EM wave capture. They both take advantage of the Electro-Magnetic characteristics associated with the RF signal to power up the tag.
Both types describe certain electromagnetic areas formed by a Radio Frequency signal transmitted by an antenna . There is a thin line between both terms, and also there is a transition area between them as well, which has the characteristics of both regions.
Electromagnetically; far-field is commonly used whenever a long reading range is required, and typical UHF RFID reader antenna works with a pure far-field characteristic. Inductively near-field operation is usually used for objects surrounded by metals or liquids . Therefore, only low carrier frequencies are used in near-field coupling tags; the two most commonly used are kHz LF and It is a magnetic induction that is normally a result of a reader passes a large alternating current through the reader coil, resulting in an alternating magnetic field.
If a tag is placed that incorporates a smaller coil see Fig. If this voltage is rectified and coupled to a capacitor, a reservoir of charge accumulates, which you can then use to power the tag chip . The EM field in the near-field region is reactive in nature, the electric and the magnetic fields are orthogonal. Depending on the type of antenna, one field such as the electric field for a dipole or magnetic field for a coil dominates the other .
Near-Field coupling was one of the first approaches to be chosen for Passive RFID implementations around the world because of its design simplicity despite its physical limitations . As the frequency of operation increases, the distance over which near-field coupling can operate decreases.
A further limitation is the energy available for induction as a function of distance from the reader coil. The magnetic field drops off at a factor, which can be calculated in Eq.
So; the magnetic field drops dramatically as the distance between the tag and the reader increases. As applications require more bits stored in the IC circuit, it is also required to maintain a fixed read rate by distinguishing multi-pole tags in the same read range, the tag requires a higher data rate and thus a higher operating frequency.
These design pressures have led to new passive RFID designs based on far-field communication ; This will be discussed in details in the next section.
As the signal range for this type of coupling is small compared to the other types of RFID techniques; which will result in designing the reader antenna with larger than normal antenna in order to enlarge the interrogation zone to cover up the short read range for the RFID Tag, for instance x mm2 . Moreover, the conventional solid-line loop with the perimeter comparable to one operating wavelength cannot produce even magnetic field distribution in the near-field zone of the antenna for one simple reason; the current distribution along the loop experiences phase-inversion, and the current approaches zero.
The magnetic field is relatively weak in certain region of the interrogation zone, which degrades the reliability of RFID tag detection . Some electrically large loop antennas have been reported to generate strong and even magnetic field.
Dobkin et al. A segmented loop antenna with a diameter of 10 cm performed a desirable performance at a frequency of MHz. Oliver proposed the broken-loop antennas in Three broken-loop antennas using different coupled lines, namely triple line, double line and single line, were demonstrated in the U. To achieve the required reading range, the antenna with the suitable design must be chosen.
Choosing the right antenna depends on the designated tag size, reader antenna size, and operating frequency. The designed antenna should generate a magnetic field evenly distributed across the 3D space to cover as much passive RFID tags as possible, which conventional line loop antennas cannot achieve. Shows the frequency bands and their categories . A smaller dipole antenna in the tag receives this energy as an alternating potential difference that appears across the arms of the dipole.
A diode can rectify this potential and link it to a capacitor, which will result in an accumulation of energy in order to power its electronics. Attenuation occurs as EM waves radiate from the reader to the tag . These days, as the size of the semiconductor-based electronics is getting lower and lower, the energy required to power up the tag continues to decrease, which serves the purpose of RFID very well.
[PDF] Introduction to Radio Frequency Design Popular Colection
Furthermore; customized RFID Tags can be designed and manufactured at a very low cost, and they can be read from a distance that might reach up to metres with average power consumption dBm in a frequency of 2. A typical far-field reader can successfully interrogate tags 3 m away, and some RFID companies claim their products have read ranges of up to 6m, refer to Table 1. The electro-magnetic field in the far-field region is radioactive in nature.
Changing the mismatch or loading on the antenna can vary depending on the amount of reflected energy, which is also called Backscattering . Table 2. For instance, the distance between the RFID Antennas and the tags affects the tag coverage, which must be taken in consideration when planning the system .
The tag type chosen in this paper is the passive RFID for two simple reasons. They can be found in a wide variety of areas like, airports, libraries, shopping malls, home automation applications, and much more. For instance as of , libraries employ RFID applications in 2, facilities . The second reason is the purpose behind this review article, which is to gather as much information as possible about the various RFID technologies and applications. And put them all together in one reference, which can be used later on to build a passive RFID system to be used in a library system to track the library books and different library items.
Each tag is identified by a unique number that uniquely describes this tag, which makes it easy for the middleware to communicate and store information about the objects. Every tag is bundled with an internal antenna that is used to transmit information to the RFID Reader, and also it participates in powering up the tag by receiving the signal from the reader antenna. And normally these two components are packaged separately into two component sets as shown in Fig.
The third and last component is the Backend system, which is the application that contains the information about all the tags in the network and manages the flow of information between the tags and the readers.
In the next few sections, all these three components are studied and investigated closely, with one more section that will be added to the end of this chapter to explain a very important concept in RFID; which is collision, and later on, in the same section, a few anti-collision algorithms are discussed.
Passive tags retrieve the necessary energy from the signal transmitted by the reader's antenna; depending on the antenna type, the tag retrieves the required energy from the interrogating wave or from a constant signal that some antennas transmit to power up the tag. Passive tags are the cheapest to manufacture, do not require maintenance, and are more compact and lighter . The second type of tags is the active tag, which includes a battery as a power source, to enhance reading range.
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Semi-passive tag operates similarly to the passive tag, using backscattering technique to reply to the reader. The primary difference is that semi-passive tag has a battery to power a circuitry that is embedded in the tag, which is used in conjunction with externally integrated electronic components such as sensors; Other than that semi-passive tag has the same characteristics of the passive tag reading range, operating frequency .
The interrogator, an antenna packaged with a transceiver and decoder, emits a signal activating the RFID tag in order to read the information saved on this tag, see Fig.Mathematics , Physics , Electronics , Information technology. Every tag is bundled with an internal antenna that is used to transmit information to the RFID Reader, and also it participates in powering up the tag by receiving the signal from the reader antenna.
Behzad Razavi. Circular Polarisation: In this antenna, the electromagnetic wave covers the two planes when propagating in a circle- like motion which looks like the motion of a screw. Mastoi, A. Sydanheimo, L. Separation of the ordered from the random components is desirable in MRI to improve signal detectablity, and in ultrasound to distinguish features of the scattering for the purpose of tissue characterization or discrimination.
Barolli, F. While the bottom figure depicts a signal for Circular polarization antenna, the blue arrows represent the direction of the magnetic field, and the red line is the electromagnetic signal flow .
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