A 1-GHz single-chip quadrature modulator

The design of an integrated quadrature modulator for a 800-MHz to 1-GHz frequency range is presented. It is shown that this modulator achieves a phase error of less than ±3° without any trimming or tuning. This performance was achieved by reducing the number of building blocks and keeping a symmetrical transistor structure even in the layout. To overcome the amplitude difference of the phase-shifted signals, a modulator principle is used rather than a multiplier principle. The circuit was implemented in a bipolar transistor array with an f_T of 9 GHz