Return Loss Bridge
This item is used to check if the impedance of an active or passive circuit is of a certain fixed value -
The circuit below is a simple bridge made up of three RF quality resistors R1-
1. T1 is constructed using a hi-
The RF source is some form of signal generator and the RF detector can be a Spectrum Analyser, sensitive scope, RF millivoltmeter or RF Log Detector followed by a scope.
Good RF quality construction and components are required and the bridge is capable of operation from 1 -
Check the completed bridge with a known good quality 50 ohm load resistor. The output level at the detector port with the load in place should be at least 30dB below the level with the load removed.
2. The Return Loss Bridge may also be used as a Hybrid Combiner. This is a useful mechanism to combine two signals when carrying out intermodulation tests on components or receivers. Connect Signal Generator A to the ‘Signal Input’ port, Signal Generator B to the ‘Detector’ port and take the combined output from the ‘Item Under Test’ port. Both signal generators should have 50 ohms output impedances.