Adaptation network
A matching network (also matching network , from English often as matchbox hereinafter) is in the electrical circuitry for matching the impedance between a source of high frequency signals (for example, high-frequency generator ) and a consumer, for example an antenna . Matching networks between a radio device and an antenna are also known as antenna tuners and improve the transmission and reception properties. With the help of this device, the electrical length of the antenna is changed without changing the mechanical length. Similar matching networks are also used in other high frequency generator applications, such as plasma etching .
The circuit contains switchable or variable reactances ( inductances and capacitances - almost lossless transformation, rarely also resistances - lossy transformation). The construction can be done in different circuits. Circuits such as the Pi circuit with a resonance transformer are often used. In addition to the improved adaptation, such circuits can also reduce the harmonics.
By manually or automatically changing the component values, for example when using variable capacitors , it is achieved that the transformed impedance of the antenna corresponds to that of the radio device. It is an impedance transformation . This adaptation is usually narrow-band and must be reset for changed frequencies.
Good adaptation is necessary, especially for transmitters . Mismatching means that part of the transmission power is reflected and has to be destroyed as heat in the transmitter or the power amplifier. The aim is therefore to offer the transmitter a standing wave ratio as close as possible to 1. This problem does not exist with pure recipients. Here, the benefit of the matching network results from a higher signal level at the input of the receiver.
Antenna tuners are sometimes simply referred to as tuners (not to be confused with the receiving circuit ).
literature
- O. Zinke, H. Brunswig (Ed.): High frequency technology 2. Electronics and signal processing, 5th edition, Springer Verlag, Berlin / Heidelberg 1999, ISBN 978-3-642-63678-3 .
- Rainer Geißler, Werner Kammerloher, Hans Werner Schneider: Calculation and design methods of high frequency technology 1. Friedrich Vieweg & Sohn Verlag, Wiesbaden 1993, ISBN 978-3-528-04749-8 .
- J. Peters: Transient processes, negative feedback, stability. Theoretical foundations and applications, Springer Verlag, Berlin / Heidelberg 1954.
- G. Zimmer: high frequency technology. Linear models, Springer Verlag, Berlin / Heidelberg 2000, ISBN 978-3-642-63082-8 .
- Frieder Strauss: Basic course in high frequency technology. An introduction, 2nd edition, Springer Fachmedien, Wiesbaden 2016, ISBN 978-3-658-11899-0 .
Individual evidence
- ↑ Alois Krischke , Karl Rothammel : Rothammels Antennenbuch. 12th edition. DARC, Baunatal 2002, ISBN 388692033X , p. 174ff.
- ↑ Alois Krischke, Karl Rothammel: Rothammels Antennenbuch. 12th edition. DARC, Baunatal 2002, ISBN 388692033X , p. 172.
Web links
- From the antenna to adaptation (accessed August 31, 2017)
- Electrical adaptation network with a transformation line (accessed on August 31, 2017)
- Embedding and de-embedding processes in high-frequency applications (accessed on August 31, 2017)
- Signal transmission and lines (accessed August 31, 2017)