# A 5G NR FR2 Beamforming System with Integrated Transceiver Module
## 3 Fabrication and Measurement
### Measurement of 28 GHz RF Transceiver Module  
The integrated 28 GHz RF transceiver module was manufactured using commercially available off-the-shelf (COTS) chipsets and RF passive components such as RF switches, frequency up/down-converters, and millimeter-wave signal sources. To fabricate the 28 GHz RF transceiver module, the performance of the individual RF circuit chips was validated, and the design and performance of RF passive components on a PCB were verified. Especially at the high frequencies of the 28 GHz band where RF performance degradation often occurs during SMT, actual measurements were conducted to compare and analyze the performance against the datasheet specifications. Figure 12a shows the top view of the manufactured 28 GHz RF transceiver module, and Figure 12b shows the bottom view of the transceiver module. To minimize power consumption and losses, a frequency conversion structure utilizing a frequency quadrupler at the LO stage was employed in the frequency up/down-converters. To facilitate LO signal supply and frequency variability, a frequency synthesizer in the form of a PLL chip was utilized. To supply the LO signal to the transceiver, differential outputs were supplied to the transmitter and receiver one by one. The RF transceiver board was manufactured using a cost-effective multilayer FR4 PCB. The interface between the RF components utilized the Grounded Coplanar Waveguide (CPWG) transmission lines to minimize losses and coupling between adjacent lines. To implement the RF transceiver on a single PCB, the isolation between the transmission and reception was crucial. The RF signals, baseband signals, and control signals were separated into different groups in the PCB. The size of the fabricated RF transceiver module was 103 \(\times\) 60 \(\times\) 38 mm\({}^{3}\), implemented with an input voltage of 6V and a current consumption of 1.4 A. A command-based control program was developed using SPI and UART for gain/power/frequency variability control. The up-converter measurement of the RF transceiver was performed by supplying the IF frequency of 802 MHz through the signal generator. An external 90\({}^{\circ}\) hybrid coupler was used to select the appropriate sideband for conversion and suppress the signal in the unwanted sideband. The measurement setup of the 28 GHz up-converter is shown in \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ref.** & **This Work** & **[4]** & **[27]** & **[28]** \\ \hline Number of elements & 8 \(\times\) 7 & 4 \(\times\) 2 & 4 \(\times\) 2 & 8 \(\times\) 8 \\ Freq. (GHz) & 28 & 25.8–28 & 26.5–29.5 & 28–32 \\ Polarization & Single & Dual & Dual & Single \\ Gain (dBi) & 15 & 14 & N/A & 22.5 \\ Scan range (\({}^{\circ}\)) & \(\pm\)50 & \(\pm\)20 & \(\pm\)45 & \(\pm\)50 \\ HPBW (\({}^{\circ}\)) & 13 & N/A & N/A & 10.5 \\ SRR (dB) & 15 & 9 & 7 & 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of 28 GHz RF beamforming system performance. Figure 12: Manufactured 28 GHz RF transceiver module: (**a**) top view and (**b**) bottom view. Figure 13. The LO of the transmitter applied a 0 dBm signal at a frequency of 6.8 GHz, and a quadrupler was built inside the transmitter, so the LO frequency of the actual frequency converted was applied at 27.2 GHz. At this time, it was confirmed that the RF signal was output at a frequency of 28 GHz, as shown in Figure 14. The image and the LO signals were highly attenuated compared to the RF signal. At this time, the phase noise at a 1 MHz offset frequency was measured to be \(-118.87\) dBc/Hz at 28 GHz, as shown in Figure 15. The frequency conversion gain of the transmitter was measured to be around 20 dB. The down-converter module was designed similarly to the up-converter. The down-converter measurement of the 28 GHz RF transceiver module was performed by supplying the RF frequency of 28 GHz through the signal generator. The measurement setup of the 28 GHz down-converter is shown in Figure 16. An external 90\({}^{\circ}\) hybrid coupler was used to select the appropriate sideband.