Compact millimeter-wave frequency doublers using slow wave structure in balun

Compact frequency doublers for operation in millimeter-wave bands are demonstrated. These frequency doublers adopt two types of slow wave structure in Marchand balun, thereby reducing the chip size. The results demonstrate low conversion loss and good fundamental signal suppression with a wide operation bandwidth. These doublers fabricated by GaAs PHEMT process, with a size dimension of less than 0.288 mm², could thus be obtained. In comparison with the conventional Marchand balun, more than 48% of reduction in the length of the coupled line can be achieved.