Patent ID: 7961064

Claim:
A directional coupler comprising: a pair of coupled transmission lines, said pair of transmission lines being located in close proximity to each other so that they are electromagnetically coupled to each other, said pair of coupled transmission lines comprising a first transmission line and a second transmission line, said first transmission line comprising a first end, to which a first RF port is connected, and a second end to which a second RF port is connected, said second transmission line comprising a first end to which a third RF port is connected and a second end to which a fourth RF port is connected, so that an electrical signal fed to said first RF port produces a direct electrical signal at said second RF port, and a coupled RF signal at said third RF port, said pair of coupled transmission lines having an even mode impedance Z 0E and an odd mode impedance Z 0O ; said directional coupler further including a first impedance matching and impedance transforming attenuator connected at said third port which provides a level of attenuation and which transforms a reference impedance value Z 0 connected to a fifth RF port to a transformed impedance Z P3 not equal to Z 0 which appears at said third RF port, the value of Z P3 being given by: Z P ⁢ ⁢ 3 = Z 00 × Z 0 ⁢ E Z 0 , wherein one or both of said first and second transmission lines has an increased width vis-à-vis the required width of each first and second transmission line when Z P3 =Z O , and wherein the product of said even mode impedance and said odd mode impedance of said pair coupled transmission lines has a value that is less than Z O 2 .