A 5-GHz frequency-doubling quadrature modulator with a ring-type local oscillator

A 5 GHz direct-conversion quadrature modulator has been developed using a frequency-doubling circuit technique to integrate a local oscillator on a single silicon chip. A three-level mixer, newly designed with symmetrical topology for two local oscillator inputs, is used to apply the frequency-doubling technique, so low image component levels of the modulated signals are achieved. The modulator is implemented on a single chip using Si bipolar process technology with a cutoff frequency of 40 GHz. The image ratio is less than -34 dBc at a 5 GHz carrier frequency.