High-frequency coupler

High-frequency coupler. (Courtesy of Circuits Processing Technology Inc. EhiPont Application Note Reference H-84338.)... 

Fig. 10.5 High frequency optical modulators and switches (a) construction of a rib wave guide with microwave strip line upper electrode, and plan views of (b) Mach-Zehnder, (c) birefringent, and (d) bi-directional coupler modulators. Reproduced with permission of Wiley-VCH from Dalton et al. (1995).

For RF measurements, another class of instruments is available. Modem high-end network analyzers range up to 110 GHz. These instmments use reflexion measurements to determine ratios of inserted to reflected power. Because of the use of directional couplers, the lower frequency limit will typically not go below a few kHz. To obtain complex impedance values, a vector network analyzer (VNA) is needed, because scalar network analyzers give absolute values only. Measurements can be conducted very fast... 

The transmitted and reflected power measurement needs a bidirectional coupler and two power detectors, one for each measurement. The coupler main characteristics are the following ones coupling, directivity, low insertion losses, 27.095MHz operation frequency and a high input power. The design of this component has lead to consider and compare two possibilities microstrip lines and toroidal cores. 

A test method for examining the effect of flux residues at frequencies as high as 10 GHz was developed (Ref 40). A bidirectional coupler was used (Fig. 18) and a lumped element model to... 

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