The high-frequency technology (also RF technology ) deals with the electrical engineering in the high frequency range. It is of importance, among others, to the territories of radio and television technology, communications, transmission and reception technology, antenna technology, radar technology and welding technology.
We distinguish the RF technology of the NF- technology ( low-frequency technology). In the radio engineering of the HF part of the antenna, the antenna amplifier, the tuner, the mixer and the intermediate frequency amplifier. It included all frequencies above the audible limit. The audio portion to about 10-20 kHz belongs to the low-frequency technology.
At higher frequencies, parasitic ( = additional unwanted ) properties are increasingly important. The use of RF transistors, for example, equivalent circuits must be used, which contain additional resistors, capacitors or inductances.
At still higher frequencies, the modules differ, since the electromagnetic waves are important here with correspondingly short wavelengths for the behavior. There are new components such as antennas, waveguides, traveling wave tubes.
For the definitions are no longer frequency can be specified. It also depends on the size of the particular application. In extreme cases, include power supply lines with 50 or 60 Hz already RF technology, when long distances to be bridged. These include the transmission lines in Canada. Electronic circuit cards of the high frequency range starts at about 100 MHz, the digital signals occur in from about 10 Mbit / s. Within microchips include some 100 MHz over short distances even for the low frequency range.
Example: motherboard of computers
Electromagnetic waves in vacuum propagate at the speed of light, ie, with about 300,000,000 m / s In electronic circuit boards their velocity is smaller, only about half to 2/3 that speed.
The first PCs a major manufacturer worked with about 5 MHz. For clean signal transfer about 10-fold higher frequencies must be transferred to the board, or about 50 MHz. The wavelength of an electromagnetic wave of that frequency and 200,000,000 m / s is more than four meters. Since the main circuit board is much smaller, the conductive paths can be made as desired, optionally also bent and with varying lengths. They can be viewed as a normal, electrically short wires.
Later PCs worked on the board with 133 MHz or 266 MHz. The wavelengths of the on-board signals to be transmitted (ten times the frequency ) are here in the range of about 10 cm. Since the interconnects are also of this magnitude, it must be understood here as RF components. Your routing and length is therefore very important for the function. Also their characteristic impedance needs to be considered. To prevent reflections of the signals, the line end is normally closed with the resistance in the magnitude of the wave impedance.