Broadband high frequency baluns and mixer

Abstract

A double slot balun has two pairs of coplanar, electric conductive sheets in a superposed, spaced, electrically insulated relation on opposite planar surfaces of a dielectric substrate forming two slots disposed in spaced, parallel planes. Unbalanced signals applied simultaneously to common ends of the slots result in balanced in-phase signals at the opposite end of the two slots. A constant impedance balun has two alined, electric conductive strips in a superposed, spaced, electrically insulated relation mounted on opposite planar surfaces of a dielectric substrate with the widths at opposite ends of each conductive strip being chosen for selected parallel-plate impedance characteristics and one conductive strip having a selected taper, preferably following a cosine curve, while the width of the other conductive strip is selected relative to the cosine taper along its length to provide a constant impedance at any point along the length of the two conductive strips. A broadband mixer has a common dielectric substrate with a double slot balun associated with an RF signal port and two of the constant impedance baluns associated with the LO signal port and in turn these baluns are interconnected with a double balanced bridge arrangement having two separate rings of matched diodes with no cross-over connections between the baluns or between the baluns and the diodes.