Methods for matching adaptive hybrids (15) to lines (16) for making
reflectograms of the lines (16) measure (1) input impedances (Z.sub.meas)
of the lines (16), model (2) characteristic impedances of the lines (16)
via physical models (Z.sub.phymod), estimate (3) parameters of the
physical models (Z.sub.phymod) via cost functions which depend on the
measured input impedances (Z.sub.meas), convert (30) the modelled
characteristic impedances into impedance values (13), and set (31) the
adaptive hybrids (15) with the impedance values (13). Unwanted near-end
reflections are minimised and wanted reflections can be measured. The
physical models depend on frequencies s, Bessel functions J.sub.i and
parameters a.sub.i related to geometrical dimensions A, D and L and
material constants .sigma., .epsilon. and .mu. of the lines (16). The
method may further model (6) characteristic impedances of the lines (16)
via rational function models (Z.sub.rafumod) and estimate (7) parameters
of the rational function models (Z.sub.rafumod) via further cost
functions which depend on outcomes of the physical models (Z.sub.phymod).