Direct-conversion quadrature modulator MMIC design with a new 90/spl deg/ phase shifter including package and PCB effects for W-CDMA applications

This paper presents a wideband code-division multiple-access direct-conversion quadrature modulator monolithic-microwave integrated-circuit (MMIC) design that employs a new technique to generate the 90/spl deg/ phase shift with low implementation loss. From the bare-chip measurement, this new 90/spl deg/ phase shifter has been proven with an amplitude and phase error less than 0.6 dB and 0.8/spl deg/, respectively, within the applied frequency range from 1.85 to 1.98 GHz. The package and printed circuit board (PCB) interconnects are also analyzed using the three-dimensional electromagnetic simulation tool and transformed into the equivalent-circuit elements for co-simulation with the designed quadrature modulator MMIC. The degradation of error vector magnitude and sideband suppression due to the package and PCB can be well predicted and verified by measurements. Although the proposed 90/spl deg/ phase shifter has a remarkable advantage over the others in implementation loss, it is quite susceptible to the package and PCB effects and needs more design efforts to deal with those effects.