Compression point
The compression point is used for the quantitative description of the non-linear behavior of an active element ( e.g. an amplifier ) e.g. B. in audio components or in high frequency technology . It indicates the greatest amplitude of the input signal at which the distortions caused by non-linearity do not yet exceed a specified level.
The cause of the non-linear behavior is the saturation that occurs in every amplifying component ( transistor , electron tube ) above a certain input amplitude. The designation compression point indicates that the saturation always leads to a smaller, ie "compressed" (compressed) output signal compared to the linear case.
definition
The 1 dB compression point , often referred to as P1dB , is that value of the input amplitude at which the power of the output signal at the fundamental frequency deviates by 1 decibel from the ideal linearly extrapolated characteristic of the component
( and are linear quantities here.)
In data sheets the P1dB is given as input power in dBm . In addition to the 1 dB compression point, you can also use any other compression point, e.g. B. Define P3dB for a deviation of 3 dB.
Calculation of the amplitude
The characteristic of a non-linear amplifier can be expressed in a Taylor series
describe.
In the 1 dB compression point, the following applies
is the amplitude at the 1 dB compression point
The following results are changed:
or logarithmic:
literature
- Otto Mildenberger (Ed.): Information technology compact. Theoretical foundations. Friedrich Vieweg & Sohn Verlag, Wiesbaden 1999, ISBN 3-528-03871-3 .
- Hans Dodel, René Wörfel: Satellite frequency coordination . Regulations - link design - system technology. Springer Verlag, Berlin / Heidelberg 2012, ISBN 978-3-642-29202-6 .
- Johann Siegl, Edgar Zocher: Circuit technology - analog and mixed analog / digital. 5th edition. Springer Verlag, Berlin / Heidelberg 2014, ISBN 978-3-642-29559-1 .
- H. Meinke, FW Gundlach: Pocket book of high frequency technology. Volume 3: Systems. 5th edition. Springer Verlag, Berlin / Heidelberg 1992, ISBN 3-540-54716-9 .
- Frieder Strauss: Basic course in high frequency technology. An introduction. 2nd Edition. Springer Verlag, Berlin / Heidelberg 2016, ISBN 978-3-658-11899-0 .
- Manfred Thumm, Werner Wiesbeck, Stefan Kern: high frequency measurement technology. Procedures and measuring systems. 2nd Edition. Springer Fachmedien, Wiesbaden 2008, ISBN 978-3-519-16360-2 .
See also
Web links
- Description of the 1-dB compression point on page 8 (PDF file)
- Description of the 1 dB compression point on page 9 (PDF file; 76 kB)
- Description of the 1-dB compression point on page 37 (PDF file; 900 kB)