This paper presents and analyzes an active vector modulator based on the polar coordinate system and composed of circulator-based phase shifters and a variable gain amplifier. The design provides full phase control range of 360 and gain control range of 36 dB for a wide frequency range of 2-6 GHz. Phase and gain can be controlled with total root mean square (rms) linearity errors of 6.3 and 0.15 dB and rms correlation errors between gain and phase of 0.6 and 1.1 dB, respectively. Therefore, the design is suitable for RF diversity receivers in the - and -bands. The integrated circuit includes all necessary peripheral circuits, such as a digital control block and internal references and covers 1.06 on a 0.25- BiCMOS technology.