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.