A set of 6 tutorials in RFID basics sent as 6 emails one per day. Presumably they want you to register in the hope you will opt in for their newsletters etc, The fineprint has the standard no-copying on requirement. Join course http://bit.ly/_RFIDBasics RFID consulting home page http://www.skyrfid.com/ 'Fair use' extract from lesson one (copied to me :-) )as a guide to whether you want to join. Russell Reference from: You know who you are ______________________ *Lesson 1 RFID Basics* Welcome to your first free lesson in RFID basics. If you know of someone who you think would like to take this course please send them the URL for SkyRFID - http://www.SkyRFID.com rather than send this lesson as we are continuously updating this information based on your feedback. We hope by the end of lesson six, you will have a good basic understanding of RFID, it= s strengths and its weaknesses. Additional in depth On Site technical courses are available from SkyRFID, please check our web site for further information. Now on to RFID! *What is Radio Frequency Identification?* Radio Frequency Identification is a technology that uses Radio Frequency waves to interrogate or read objects known as transponders or tags. Each tag always has a *Unique Identification Number* (UID) stored in bits in the tag memory that is transmitted to the reader when the Tag is Read. In addition to the UID there may be other information stored in the tag memory. The technology allows for reading of tags from physical contact to beyond the line of sight of the reader. A simple RFID system consists o= f a reader with a cable attached to an antenna and a tag that is read( interrogated) by the reader. Radio Frequency (RF) Basic Terminology *Radio Frequency signals are a form of electromagnetic wave* consisting of the same radiation as light, ultra-violet, and infra-red rays. Radio Frequency waves/signals radiate outward from an antenna and have both an electric and a magnetic wave component. The frequency that a radio frequency identification (RFID) system operates is called a =93carrier wave=94 or "carrier frequency". *RFID systems operate on a number of frequencies*. Some of the common RFID Frequencies are - 125 kHz. Also known as Low Frequency (LF) - 134.2 kHz. Also known as Low Frequency (LF) - 13.56 MHz. or High Frequency (HF) - 868 MHz. =96 European =96 Ultra High Frequency (UHF) - 915 MHz. =96 Ultra High Frequency (UHF) - North America and other countries - 2.45 GHz. Microwave Frequency (SHF) There is also another radio band assigned to RFID =96 5.8 GHz. SHF (Super H= igh Frequency); also known as Microwave. This band is now being used for longe= r range RFID for asset management and active technology tracking. Missing from these frequencies is the 433 MHz. band which was originally specified for Active Tags and is usually proprietary and or Military. The 2.45 GHz. band is replacing the 433 MHz. since there are inter operable standards and ratified regulations. *Antennas are tuned* to resonate *only to a narrow range of carrier frequencies* that are centred on the designated RFID system frequency. Thi= s means that a system with a carrier wave of 915 MHz.(centre of 902 ~ 928 MHz.) will not read a tag at 13.56 MHz., 125 kHz. Frequencies or 2.45 GHz. However it may be able to read an 868 MHz. tag if the tag is *EPC Gen 2.*More about this later. *RFID systems use the decibel (dB*) to describe antenna gain, cables losses and power output for all hardware specifications and regulations. There ar= e different regulations for different frequencies in different countries that must be taken into consideration when designing, installing and maintaining an RFID system. *The wrong power selection has serious legal and health implications!* The Decibel is ... * SOME MATERIAL REMOVED FROM HERE SEMI RANDOMLY * * * *Gain is positive and loss is negative.* - A 3dB gain/loss is equal to a 2 times increase or decrease in signal level. So if a cable has a 3dB loss, it loses 50% of its signal strengt= h by the time it gets to the other end of the cable. - A 10 dB gain/loss is equal to a 10 times increase or decrease in signa= l level. If a cable has a 10dB loss, then it loses 90% of its signal stren= gth by the time it gets to the other end of the cable. - A 20dB gain/loss is equal to a 100 times increase or decrease in signa= l level. So if a cable has a 20dB loss, then it will lose 99% of its signal strength by the time it gets to the other end of the cable. The Radio Frequency *POWER LEVEL* is expressed in watts or in dBm. dBm refers to the power in decibel referenced to one milliwatt (1mW). The relation between dBm and watts is given by the formula: - *P(dBm) =3D 10 x Log (P/1mW)* dBm Watt 0 0.001 10 0.01 20 0.1 30 1.0 40 10.0 The value 30 dBm =3D 1.0 Watt should be remembered for future use. - P (dBi; references an isotropic radiator) =3D 1 - log (Pr/Pi), where P= i is power received from an isotropic antenna. - P (dBd; references a dipole antenna) =3D 10 Log (Pr/Pd), where Pd is power received from a dipole antenna. *Basic electromagnetic (EM) propagation modes are*: - Free space *line of sight transmission* =96 satellite communications - *Reflection* =96 most commonly used for land mobile communications - *Refraction* =96 bending the EM waves when it passes through media suc= h as water, plastic, and other materials that have different refractive indexes. - *Diffraction* =96 bending the EM waves around an object. *Attenuation is the reduction in amplitude and intensity of a signal*. As the EM wave goes farther, is reflected, refracted or diffracted the signal strength drops dramatically. An Isotropic source radiates power equally in all directions =96 laboratory and theory only just to assist you in understanding theory versus practicality. As the EM signal travels from the transmit antenna to the receiving antenna it loses strength. While the previous information may seem somewhat complicated, rest assured that it will become clearer and clearer in the next few lessons. Lesson 2 will apply the physics of lesson 1 to tags, readers and antenna. Read this lesson at least once today, once again tomorrow and once again i= n 7 days and you will remember most of this for the rest of your life! See you tomorrow! Best Regards SkyRFID Training Staff Training@SkyRFID.com Toronto: 647.476.3265 Cambridge: 519.489.2557 www.SkyRFID.com * * --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .