NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 61580 4 Première édition First edition 1997 08 Méthodes de mesure appliquées aux guides d’ondes – Partie 4 Atténuation des guides d’ondes et des ens[.]
Méthode 1
Analyseur d’amplitude et/ou enregistreur
The article discusses essential components for RF systems, including low-pass filters, couplers, and calibrated attenuators A low-pass filter is crucial for eliminating unwanted harmonic frequencies, and if its return loss is inadequate, it should be placed before the isolator, provided it does not negatively impact the RF source Couplers must ensure that the error signal at the detector ports is minimal compared to the measured signal, which can be achieved by maintaining well-matched ports and high directivity, typically exceeding 45 dB Coupling values generally range from 10 dB to 20 dB with a consistent response across the desired frequency band Additionally, attenuators must be calibrated within the test frequency range to ensure accuracy.
Amplitude analyser and/or recoder
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Méthode 2
Analyseur d’amplitude et/ou enregistreur
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Amplitude analyser and/or recorder
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Méthode 3
Analyseur polaire et/ou enregisteur
Le principe de cette méthode est de mesurer le facteur de Qualité (Q) d'une cavité à une porte
Considering the waveguide as a transmission line of length \( l \), with the equivalent admittance of the waveguide, it is advisable to select an iris with approximately 10 dB of coupling, denoted as \( Y_e \), in the inductance plane (iris).
Y e = coth ( γ × l ) (1) ó γ est la constante de propagation: ( γ = α + j β )
Si Y s est la susceptance de l'inductance, l'admittance résultante est:
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Polar analyser and/or recorder
The principle of this method is measuring the Q factor of a one-port cavity
In a transmission line waveguide of length \( l \), the equivalent admittance \( Y_e \) is positioned in the same plane as the inductance (iris), utilizing an iris with an approximate coupling ratio of 10 dB.
Y e = coth ( γ × l ) (1) where γ is the propagation constant: ( γ = α +j β )
If Y s is the susceptance of the inductance, the resulting admittance is:
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Lorsque la fréquence varie, Y e décrit un cercle sur le diagramme polaire Pour f 0 , à la résonance:
Après simplification et avec A = tanh αl
Ainsi, si nous notons le facteur de surtension Q 0 comme:
2 0 δ δ (5) ó δ B est la variation de susceptance pour δ f variation de fréquence (B = Im (Ytot))
Après différentiation et simplification par A 2