Single balanced planar mixer

Claim 1

A single balanced planar mixer comprising A. an insulating substrate having an upper and lower surface suitable for supporting patterned conductors and electronic components; B. a first balanced transmission line of a coplanar strip design for propagating waves at input signal frequency, comprising first and second conductors supported on said upper surface; C. a second unbalanced coplanar transmission line for propagating waves at local oscillator and intermediate frequencies, transitioning to said first line, and comprising: a third conductor supported on said upper surface and positioned along the axis of said first line but spaced from the conductors of said first line at said transition; and fourth and fifth conductors supported on said upper surface to each side of said third conductor and transitioning in an electrically continuous path to said first and second conductors respectively; said fourth and fifth conductors representing finite ground planes of said second transmission line; D. a pair of diodes disposed at the transition between said first and second lines, one diode being coupled between said third conductor and the transition between the first and fourth conductor and the other diode being connected between said third conductor and the transition between the second and fifth conductor, said diodes converting said input waves to an intermediate frequency when local oscillator waves are coupled to said second line; said transition between said first, balanced transmission line and said second, unbalanced transmission line blocking transmission of the input signal to said second line and the intermediate frequency and local oscillator signals to said first line; E. a third unbalanced transmission line of a microstrip design for propagating waves at local oscillator and intermediate frequencies, transitioning to said second transmission line, said third transmission line comprising a sixth conductor of finite width supported on said upper surface, electrically continuous with said third conductor, and a seventh conductor supported on said lower surface to form a ground plane under said sixth conductor; and F. a pair of resonant lines of microstrip design having an electrical length of one quarter wave length at the local oscillator frequency, positioned at the transition between said second and third lines to create low impedance connections at the local oscillator frequency between said finite ground plane conductors of said second transmission line with the ground plane of said third transmission line at the local oscillator frequency, and G. means providing capacitance between said finite ground plane conductors and said ground plane to provide low impedance connections at said intermediate frequency, and H. means for coupling said third line to an input port for connection to a local oscillator and to an output port for connection to an intermediate frequency amplifier.