A high frequency, surface mountable coupler comprising: a monolithic base substrate having a top surface, a bottom surface, a length (Ls) in a longitudinal direction, and a width (Ws) in a lateral direction that is perpendicular to the longitudinal direction; a first thin film microstrip disposed on the top surface of the monolithic base substrate, the first microstrip having an input end and an output end; a second thin film microstrip disposed on the top surface of the monolithic base substrate, the second microstrip having an input end and an output end; a base ground plane disposed on the bottom surface of the monolithic base substrate; at least one via extending through the monolithic base substrate from the top surface to the bottom surface of the monolithic base substrate, the at least one via electrically connected with at least one of the input end or the output end of the first microstrip or the second microstrip; and four contact pads disposed on the bottom surface of the base substrate, and wherein the at least one via comprises: a first via electrically connecting the input end of the first thin film microstrip to a first of the four contact pads; a second via electrically connecting the output end of the first thin film microstrip to a second of the four contact pads; a third via electrically connecting the input end of the second thin film microstrip to a third of the four contact pads; and a fourth via electrically connecting the output end of the second thin film microstrip to a fourth of the four contact pads, wherein the base ground plane is located between the vias in the longitudinal direction or lateral direction such that the contact pads are adjacent to corners of the base ground plane, and the base ground plane is sized such that the base ground plane extends between the contact pads without directly contacting the contact pads, wherein at least a portion of the first thin film microstrip and at least a portion of the second thin film microstrip extend parallel to each other in a first direction along a coupling length (L c), the coupling length (L c) ranging from about 0.1 mm to about 3.8 mm, and wherein the coupler is configured to have a coupling factor that is greater than about -30 dB at about 28 GHz. a monolithic base substrate having a top surface, a bottom surface, a length (Ls) in a longitudinal direction, and a width (Ws) in a lateral direction that is perpendicular to the longitudinal direction; a first thin film microstrip disposed on the top surface of the monolithic base substrate, the first microstrip having an input end and an output end; a second thin film microstrip disposed on the top surface of the monolithic base substrate, the second microstrip having an input end and an output end; a base ground plane disposed on the bottom surface of the monolithic base substrate; at least one via extending through the monolithic base substrate from the top surface to the bottom surface of the monolithic base substrate, the at least one via electrically connected with at least one of the input end or the output end of the first microstrip or the second microstrip; and four contact pads disposed on the bottom surface of the base substrate, and wherein the at least one via comprises: a first via electrically connecting the input end of the first thin film microstrip to a first of the four contact pads; a second via electrically connecting the output end of the first thin film microstrip to a second of the four contact pads; a third via electrically connecting the input end of the second thin film microstrip to a third of the four contact pads; and a fourth via electrically connecting the output end of the second thin film microstrip to a fourth of the four contact pads, a first via electrically connecting the input end of the first thin film microstrip to a first of the four contact pads; a second via electrically connecting the output end of the first thin film microstrip to a second of the four contact pads; a third via electrically connecting the input end of the second thin film microstrip to a third of the four contact pads; and a fourth via electrically connecting the output end of the second thin film microstrip to a fourth of the four contact pads, wherein the base ground plane is located between the vias in the longitudinal direction or lateral direction such that the contact pads are adjacent to corners of the base ground plane, and the base ground plane is sized such that the base ground plane extends between the contact pads without directly contacting the contact pads, wherein at least a portion of the first thin film microstrip and at least a portion of the second thin film microstrip extend parallel to each other in a first direction along a coupling length (L c), the coupling length (L c) ranging from about 0.1 mm to about 3.8 mm, and wherein the coupler is configured to have a coupling factor that is greater than about -30 dB at about 28 GHz.