Practical RF Handbook, 4th Edition

5

Couplers, hybrids and directional couplers

This chapter describes some further important passive components. Hybrids are based upon transformer action, whilst directional couplers depend upon capacitive coupling in addition. First a look at simple resistive couplers or ‘splitters’. These can be used to split a signal between two outputs, in any desired ratio. Figure 5.1a shows three-way resistive splitters which provide a 50 Ω match at each port, provided that the other ports are correctly matched. Any port can be used as the input and the outputs at the other two are each 6 dB down on the input and both are in phase with it. There is thus 3 dB more attenuation at each output than with an ideal hybrid coupler, which has no internal losses. ...