Novel monolithic ultra-wideband unilateral 4-port junction using distributed amplification techniques,

A novel active unilateral four-port junction operating over 1 to 20 GHz has been demonstrated in monolithic microwave integrated circuit (MMIC) technology, using distributed amplifier techniques. The circuit is capable of covering an extremely wide frequency range. This prototype had insertion losses of approximately 5 dB and excellent port-to-port isolation. One of the key advantages of this active technique, compared to conventional circulators and directional couplers, is that the low-frequency cutoff is limited only by the design of the bias networks.<>