Radio frequency or RF is a frequency or rate of oscillation in the range of 3 Hz to 300 Ghz. This range relates to the frequency of alternating current signals to create and detect radio waves. As this range is beyond the vibration rate that many mechanical systems respond to, RF refers to oscillations in electrical circuits. When the current is passed through an antenna, an electromagnetic field is generated that is suitable for wireless broadcasting and/or communication. These frequencies cover the electromagnetic radiation spectrum ranging from 9 kHz, the lowest allocated wireless communications frequency, to thousands of gigahertz. When an RF current is passed through an antenna, an electromagnetic field is created that propagates through space. Properties of Radio Frequency Electrical Signals

• They can be ionized easily to create a conductive path across air
• The electromagnetic force that drives the RF current to the surface of conductors known as skin effect
• They have the ability to appear to flow through paths containing insulating material similar to the dielectric insulator of the capacitor

Radio spectrum Extremely low frequency - 3 to 30 Hz Super low frequency - 30 to 300 Hz Ultra low frequency - 300 Hz to 3 Khz Very low frequency - 3 Khz to 30 Khz Low frequency - 30 Khz to 300 Khz Medium frequency - 300 Khz to 3 Mhz High frequency - 3 Mhz to 30 Mhz Very high frequency - 30 Mhz to 300 Mhz Ultra high frequency - 300 Mhz to 3 Ghz Super high frequency - 3 Ghz to 30 Ghz Extremely high frequency - 30 Ghz to 300 Ghz Radio Frequency Encoding These techniques physically encapsulate an RF encodable microchip with the synthesis resin. The RF transponder can be scanned post-synthesis to identify the concerned product. RF encoding avoids the need to cosynthesize surrogate analytes, and permits the large-scale synthesis of compounds; each microcapsule can hold tens milligrams of synthesis beads. Radio Frequency Identification This is an automatic identification method. RFID tags or transponders are used for storing and remotely retrieving data. An RFID tag is an object that can be applied in a product, animal or person to help in its identification using radiowaves. Some tags can be read beyond the line of sight of the reader. These tags consist of two parts. One is an integrated circuit for storing and processing information, modulating and demodulating signals, and for other specialized functions. The second is an antenna used for receiving and transmitting the signal. Chipless RFID discretely identifies tags in the absence of an integrated circuit. So, tags are printed directly on assets, and this helps lower its production cost. RFID Tag Types The various types of tags are as follows:

• Passive : There is no internal power supply. The practical read distances range from 10 cm to a few meters, depending on the selected radio frequency and antenna design/size
• Active : There is an internal power source. The range is of hundreds of meters, and the battery life is about 10 years
• Semi-passive : They have their own power source. The battery powers the microchip, and cannot broadcast any signal

Use of RFID technology

• RFID chips for animals are very small devices injected through a syringe under the skin
• Real-time inventory tracking allows companies to control supply
• RFID systems are used in some hospitals to track a patient's location, doctors, and nurses
• Traffic monitoring system uses roadside readers to collect signals from transponders