## 4 Measurement Results  
The vector modulator described in this paper was fabricated using a 130 nm SiGe BiCMOS GlobalFoundries process (GF-8 XP). Figure 7 shows a chip micro-photograph of the modulator, which occupies an area of 1309.4 \(\upmu\)m \(\times\) 1783.8 \(\upmu\)m (with pads). Figure 8 shows a blocks diagram and a photograph of the measurement setup. The chip was characterized on-wafer using a Cascade SUMMIT 9000 probe station and a Keysight N5225B PNA Network Analyzer. Ground-signal-ground (GSG) probes were employed at the input and output ports. Additionally, multi-contact DC probes were utilized for setting the biasing voltages and currents. The biasing currents were generated using current mirrors biased with the voltage source \(V_{BIAS}\). DC voltage sources were employed to generate \(V_{CC}\), \(V_{B1}\), \(V_{B2}\), and \(V_{B3}\), while the quadrant selection voltages (\(V1^{+}\), \(VI^{-}\), \(VQ^{+}\), and \(VQ^{-}\)) were generated using an external FPGA. Finally, the Keysight B1500A Semiconductor Device Parameter Analyzer Source Measure Units (SMU) configured as current sources were used to generate the currents for controlling the phase shifting (\(DACI^{+}\), \(DACI^{-}\), \(DACQ^{+}\), and \(DACQ^{-}\)). The modulator consumes 25 mA under 3.3 V including the output subtractor. Figure 9 displays the simulation and measurement results for the S21 parameter at 19 GHz as a function of phase shift. In the simulation, 8-bit DACs with a minimum LSB-bit current step of 35 \(\upmu\)A were used to generate steering currents that control the gain of each branch. For a 360\({}^{\circ}\) phase range, the simulated S21 ranges from 7.5 to \(-\)45 dB. By carefully selecting the DAC currents, it was possible to achieve the desired phase jumps with a constant amplitude. For instance, for a constant amplitude of 0 dB and 5.625\({}^{\circ}\) phase jumps (i.e., 64 states or 6-bit resolution), the RMS phase and gain errors are only 2.36\({}^{\circ}\) and 1.46 dB at 19 GHz. The vector modulator was tested in 112 different states covering the 360\({}^{\circ}\) circle. Figure 10a,b depict the measured phase shift and gain as a function of frequency from 17.8 to 20.2 GHz for phase angles ranging from 0\({}^{\circ}\) to 360\({}^{\circ}\) with steps of 30\({}^{\circ}\). Although the measured cases do not provide enough data to determine the value of the RMS phase and gain errors, the graph demonstrates that the vector modulator can generate phases from 0\({}^{\circ}\) to 360\({}^{\circ}\) over the entire 2.4 GHz band. As shown, the modulator exhibits a relatively flat gain across the frequency band with minimal deviation. Furthermore, the phase shift shows  
Figure 7: Die photograph of the fabricated chip. a linear trend, indicating that the circuit can achieve accurate phase modulation over the entire frequency range. Figure 10c,d present the measured S11 and S22 parameters of the vector modulator for the selected states. As can be seen, the output is well matched (S22 \(<-10\) dB) in all cases. The input matching, however, is slightly worse due to insertion losses incurred by the input balun. In this paper, we propose the use of a lumped-component Marchand balun topology for its potential to reduce the required area at the operating frequencies [35]. This approach combines distributed elements with lumped components so that, instead of using quarter-wavelength transmission lines, we substitute them with pi-type lumped component equivalents. By coupling the inductors together, we are able to increase mutual inductance and further minimize the area needed. This approach not only allows for a reduction in size, but also results in a more compact and efficient design. However, the input matching is negatively affected. Figure 8: Measurement setup: (**a**) blocks diagram and (**b**) photograph. Figure 9: Simulated and measured phase shifting at 19 GHz (polar plot). In Table 1, a comparison is presented between this work and other phase shifters that operate at similar frequencies and with comparable phase resolutions.