Analysis of the equal-delay topology for transformers and hybrid networks

A complete scattering matrix representation for the ideal equal-delay topology for transformers and hybrid networks is presented. It is shown that while the operation of the hybrid as a 180[degrees] power combiner, current balun, or voltage balun is essentially frequency independent, the operation as a 0[degrees] power combiner or splitter is not. Instead, the isolation between the 0[degrees] and 180[degrees] ports is finite and frequency dependent. Moreover, the reflection coefficient at the sum port is nonzero and frequency dependent. These characteristics lead to the conclusion that while the equal-delay 180[degrees] power splitter/combiner is fundamentally frequency independent, its 0[degrees] counterpart is limited to operation well below the fundamental quarter-wave frequency of the constituent transmission lines. Full three-port scattering parameter representations, which are compatible with the calibration and analysis approach given in the CISPR 16-1 specification, are given for the three fundamental transformer and balun types derivable from the equal-delay hybrid: 1 the Guanella voltage balun, 2 the Guanella current balun, and 3 the 180[degrees] power divider or terminated hybrid balun, as specified in the CISPR 16-1 specification. Index Terms--Balancing network, balun, calculable dipole, CALTS, CISPR 16-1, equal-delay balun, equal-delay transformer, Guanella balun, Guaneila transformer, site attenuation, ultra wideband, UWB.