return loss bridge schematic
Is a 'standard' weathstone bridge
toroid-line is a balun to make possible measure unbalance between each 'leg' in bridge width extern unbalanced detectors/reciver/RSSI-circurit...
size, quality and frequency range on toroids in balun make limits on usable bandwith on bridge. - i think in your example PDF:s using high frequency toroids inside big outer toroids working for lower frequency to make bridge working between 1 MHz - 1 GHz range - resistive bridge itself can going from DC to very high frequency if you using floating, balanced detectors.
If you using reciver/RSSI-circurit with well balanced input (i think AD8307 or simular high dynamic logaritmic detectors) i think you can skip this toroid line.
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Pity AD8302 has not balanced input... otherwise I think possibly make some intresting return loss measure bridge with measure of phase angle over very wide frequency range from near DC to 2.7 GHz... - and big step to build own network analyze - if known return loss and phase angle (after open, short, load calibrate) - is possible to calculate type of complex loads ie. value on cap/ind and value of resistance on load.
data scheet on AD8302 show vector reflectometer on side 20, but builds on directivity coupler - but build directivity coupler from near DC to 3 GHz is not easy task and need same skillness as build coupler inside hp/agilent 8753 Network analyzer...