A quadrature coupler, comprising: a dielectric substrate ; a first metal layer disposed on an upper surface of the substrate, the first metal layer being patterned to provide: a first pair of ground pads (16b 1 , 16b 2 ); a first lower strip conductor , spaced from the first pair of ground pads, having an input (18 I ) at a first end, an output (18 O ) at a second end, and a coupling region disposed between the first end and the second end, and between the first pair of ground pads; a second lower strip conductor having an input end (22 I ) and an output end (22 O ); and a third lower strip conductor having an input end (24 I ) and an output end (24 O ); a first dielectric layer disposed over the coupling region; a second metal layer configured as a strip conductor disposed on the first dielectric layer over the coupling region, the second metal layer having one end disposed on, and electrically connected to, the output end (24 O ) of the third lower strip conductor and having another end disposed on, and electrically connected to, the input end (22 I ) of the second lower strip conductor ; a second dielectric layer disposed over the second metal layer and between the first pair of ground pads; and an electrically conductive shield layer disposed on an upper surface of the second dielectric layer; characterized in that : the electrically conductive shield layer extends over a first pair of opposing sides of the second dielectric layer and onto the first pair of ground pads. a dielectric substrate ; a first metal layer disposed on an upper surface of the substrate, the first metal layer being patterned to provide: a first pair of ground pads (16b 1 , 16b 2 ); a first lower strip conductor , spaced from the first pair of ground pads, having an input (18 I ) at a first end, an output (18 O ) at a second end, and a coupling region disposed between the first end and the second end, and between the first pair of ground pads; a second lower strip conductor having an input end (22 I ) and an output end (22 O ); and a third lower strip conductor having an input end (24 I ) and an output end (24 O ); a first pair of ground pads (16b 1 , 16b 2 ); a first lower strip conductor , spaced from the first pair of ground pads, having an input (18 I ) at a first end, an output (18 O ) at a second end, and a coupling region disposed between the first end and the second end, and between the first pair of ground pads; a second lower strip conductor having an input end (22 I ) and an output end (22 O ); and a third lower strip conductor having an input end (24 I ) and an output end (24 O ); a first dielectric layer disposed over the coupling region; a second metal layer configured as a strip conductor disposed on the first dielectric layer over the coupling region, the second metal layer having one end disposed on, and electrically connected to, the output end (24 O ) of the third lower strip conductor and having another end disposed on, and electrically connected to, the input end (22 I ) of the second lower strip conductor ; a second dielectric layer disposed over the second metal layer and between the first pair of ground pads; and an electrically conductive shield layer disposed on an upper surface of the second dielectric layer; characterized in that : the electrically conductive shield layer extends over a first pair of opposing sides of the second dielectric layer and onto the first pair of ground pads. <EOS>