New method of designing 0.01GHz∼40GHz wideband directional detector

This paper presents a new method of designing ultra-wideband directional detector using monolithic microwave integrated circuits (MMIC). The detector inherently is similar to a directional bridge, and so attains much broader band than ordinary directional coupler. The detector has good input port and output port match characteristics by way of computational formula according to the detector structure, almost 50 ohm at the input and output port. Simultaneously, the detector has low insertion loss and superior directivity, when signal travels in the reverse direction, the detection voltage got from the diode is zero approximately, which is what we desire in the ideal status. The diode employed is also an important device in the detector circuit. The diode is zero-bias diode specially fabricated, not the unbiased Schottky diode. It has wide dynamic range, high tangential sensitivity and high temperature stability. We executed detector circuit simulation in ADS, and got perfect performance. The detector circuit was fabricated in the MMIC in order to gain good uniformity and small area, and also low cost. Measured S-parameters show insertion loss is less than 2 dB, input and output return loss is less than -15 dB with frequency range from 10 MHz to 40 GHz. Still more, the wideband detector has superior directivity and sensitivity, with forward voltage variation 7mV/mW and reverse voltage variation less than 0.1mV/mW, which satisfies our demand.