Broadband high frequency mixer

A broadband mixer comprising:

• first balun means including a first microstrip balun and a second microstrip balun coupled to a first signal port for converting an unbalanced first signal applied to said first signal port to a balanced to ground first signal;
• second balun means including a third microstrip balun and a fourth microstrip balun coupled to a second signal port for converting an unbalanced second signal applied to said second signal port to a balanced to ground second signal, said first balun means being connected in a polarity relationship with said second balun means so that the balanced to ground signals of one of said first and second balun means do not pass to the signal port coupled to the other of said first and second balun means;
• third balun means coupled to a third signal port;
• frequency converting means having at least a first set of terminals and a second set of terminals to which are applied said balanced to ground first signal and said balanced to ground second signal, and a third set of terminals, said frequency converting means including two separate rings of four diodes per ring, said rings being connected in a double bridge arrangement with said first, second and third sets of terminals for converting said balanced to ground first and second signals to a balanced to ground third signal at said third set of terminals that is conducted via said third balun means to produce an unbalanced to ground third signal at said third signal port, said diodes electrically isolating first and second signals at said first and second signal ports from said third signal port.

A broadband high frequency mixer comprising:

• first and second unbalanced to balanced microstrip baluns coupled to a first signal port for converting a first input signal applied to said first signal port to a balanced to ground first signal;
• third and fourth unbalanced to balanced microstrip baluns coupled to a second signal port for converting an incoming second signal to a balanced to ground second signal;
• each said first, second, third and fourth baluns having a common dielectric substrate supporting a thin, flat conductor having a constant width and a tapered ground plane with a wide end and a narrow end;
• each of said conductors and each of said tapered ground planes of said first, second, third and fourth baluns having a terminal at opposite ends thereof to provide a pair of terminals on a signal port side and a pair of terminals opposite the signal port side of each of said baluns;
• the terminal connected to the wide end of the tapered ground plane being connected to ground and the other terminal of said pair being connected to an associated terminal of said first and second signal ports to provide a balanced to ground signal on the signal port side of each of said baluns;
• the terminal pairs of said first, second, third and fourth baluns oppposite the port side being cross-connected to one another to apply signals of equal amplitude and phase to each pair of terminals opposite the port side of the baluns so that their respective input signals applied to said first signal port and said second signal port are electrically isolated from one another;
• frequency converting means having a first set of terminals, a second set of terminals and a third set of terminals, said signal converting means including two pairs of matched diodes arranged in an outer ring and two pairs of matched diodes arranged as an inner ring and associated with said first, second, third and fourth baluns to short circuit said balanced to ground first signal and said balanced to ground second signal at said third set of terminals by the symmetry of the diodes in said outer ring and said inner ring to electrically isolate said first and second signals at said first and second signal ports from said third signal ports, each of said two pairs of matched diodes being coupled to said third set of terminals, each of said two pairs of matched diodes being arranged as two series circuits of two diodes each, each diode in each said series circuit being connected for current flow in the same direction;
• a fifth unbalanced to balanced balun coupled to said third set of terminals for converting said balanced to ground third signal to an unbalanced to ground third signal at said third output port.