This paper presents a wideband vector-sum phase shifter (VSPS) with high phase resolution and high inputreferered 1 dB compression point (IP1dB) which covers the full 360 • phase range with 5.6 • phase steps between 5-13 GHz in a commercial 0.25-μm SiGe BiCMOS technology. A transformer balun and an RC polyphase filter (PPF) are implemented for inphase and quadrature phase (I/Q) reference vector generation while the desired phase states are generated by an adder stage where the amplitudes of the I/Q reference vectors are manipulated with digitally controlled variable gain amplifiers (VGAs). The measured root mean square (RMS) phase error of the VSPS is <2.8 • between 7.4-10.3 GHz and <5.6 • between 5.4-11.9 GHz with a measured average insertion loss >7.8 dB. Thus, the VSPS achieves 6-bit phase resolution. IP1dB for the 1 st state of the VSPS at 10 GHz is measured to be +3.5 dBm. Overall chip size of the VSPS IC is only 1.22×0.59 = 0.71 mm 2 , excluding the RF and the DC pads.Index Terms-Vector-sum phase shifter, active phase shifter, transformer balun, I/Q network, VGA, SiGe BiCMOS, phased array.