1. Field of the Invention
This invention relates to a miniaturized dual-balanced mixer circuit which is fully equivalent in function to a conventional star-type dual-balanced mixer (DBM) for frequency mixing of millimeter wave (MMW) signals, except that the construction of the invention is based on a double spiral layout architecture that allows its IC implementation to be more miniaturized than the conventional star-type DBM.
2. Description of Related Art
In communications systems, the mixer is an essential circuit component which receives an input of a carrier signal RF and mixes it with a local oscillation signal LO to thereby produce an intermediate-frequency signal IF, where IF is either an up-converted frequency or a down-converted frequency, i.e., IF=RF+LO or IF=RF−LO.
In millimeter wave (MMW) communications systems, the dual-balanced mixer (DBM) is a widely utilized frequency mixing circuit. Various types of DBM circuits have been proposed, including a ring-type and a star-type. The star-type DBM has better performance than the ring-type so that it is more widely utilized in the industry than the ring-type. The star-type DBM is so named due to the fact that the layout pattering of the microstrip lines used to constitute the mixer circuitry looks like a star.
In practical applications, however, one drawback of the conventional star-type DBM is that it is based on a dual-balun circuit architecture which is considerably large in size in IC implementation so that it is unsuitable for use in the fabrication of miniaturized IC chips.