# A 5G NR FR2 Beamforming System with Integrated Transceiver Module
## 2 A 28 GHz RF Beamforming System and Transceiver Module
### Development of 28 GHz RF Transceiver Module  
The 28 GHz RF transceiver module consists of an up-converter, down-converter, phased locked loop (PLL) frequency synthesizer, and power and digital controller. In the transceiver module, we used the commercially available chips for the up-converter (ADMV 1013), down-converter (ADMV 1014), and PLL (ADF 4355) from the analog device (Analog Devices, Wilmington, MA, USA). A mixer-based RF transceiver structure was employed to enable simultaneous communication and sensing in the millimeter-wave range by up-converting and down-converting the baseband signal to the millimeter-wave frequency. The 28 GHz RF transceiver used a super-heterodyne method. The RF signal generator was implemented in the form of a frequency synthesizer, based on a PLL, capable of various frequency generations with low spurious content and excellent phase noise characteristics. The upconverter integrated a mixer, RF power amplifier, RF voltage variable attenuator (VVA), and LO frequency quadrupler. An external 90\({}^{\circ}\) hybrid coupler was used to achieve single-band up-conversion and to suppress the signal in unwanted sidebands. Similarly, the down-converter integrated the LNA, mixer, IF PA, and LO frequency quadrupler, resulting in the signal being received independently. The up-converter and down-converter provide two modes of frequency translation. The up-converter can directly convert in-phase quadrature (I/Q) input signals from baseband to RF. Additionally, it supports single-sideband (SSB) up-conversion when given complex intermediate frequency (IF) inputs. Similarly, the down-converter is capable of direct quadrature demodulation to the baseband in-phase (I)/quadrature (Q) output signals, as well as image rejection down-conversion to a complex intermediate frequency (IF) output carrier frequency. The assumption of the input signal with image signal and LO source can be expressed as follows:  
\[\mathrm{v_{in}(t)=A_{RF}cos(w_{RF}t+\Phi_{RF})+A_{Img}cos(w_{Img}t+\Phi_{Img})} \tag{3}\]  
\[\mathrm{v_{LO\_I}(t)=sin(w_{LO}t+\[PERSON]_{LO})} \tag{4}\]  
\[\mathrm{v_{LO\_Q}(t)=cos(w_{LO}t+\[PERSON]_{LO})} \tag{5}\]  
Then, the mixed signal can be expressed as  
\[\mathrm{v_{I}(t)=-\frac{1}{2}A_{RF}sin(w_{IF}t+\[PERSON]_{RF}-\[PERSON]_{LO})+\frac{1}{2 }A_{Img}sin(w_{IF}t+\[PERSON]_{LO}-\[PERSON]_{IMG})} \tag{6}\]  
\[\mathrm{v_{Q}(t)=-\frac{1}{2}A_{RF}cos(w_{IF}t+\[PERSON]_{RF}-\[PERSON]_{LO})+\frac{1}{ 2}A_{Img}cos(w_{IF}t+\Phi_{LO}-\Phi_{IMG})} \tag{7}\]  
Figure 8: EM simulation results of feedline: (a) return loss, (b) phase characteristics. The image signal is mitigated by employing an external 90\({}^{\circ}\) hybrid coupler, and the resulting intermediate frequency (IF) output can be expressed as follows:  
\[v_{IF}(\mathbf{t})=\mathrm{A_{RF}cos}(\mathrm{w_{IF}t}+\Phi_{RF}-\Phi_{\mathrm{ LO}}) \tag{8}\]  
The IF frequency ranges from 0.8 GHz to 4.5 GHz. The frequency range for creating the LO signal ranges from 5.6 GHz to 6.4 GHz. Therefore, the RF band spans from 24.25 GHz to 30.1 GHz. To generate a frequency in the 28 GHz band, a frequency multiplier was built into the transmitter and receiver chip, so the PLL could operate at a frequency lower than 28 GHz, reducing the power loss when distributing for transmitting and receiving LO supply. In order to supply the LO signal to the transceiver, differential outputs were supplied to the transmitter and receiver one by one. The transceiver module was mainly based on the commercially available RF surface-mounted components from the analog devices including the up-converter module, down-converter module, and local oscillator (LO) source module. The IF signal supplied was connected using an SMA connector, and to link the 28 GHz band beamforming antenna, the RF transceiver integrated board was equipped with an RF/DC connector for power supply and SPI control, and a K-type connector was used. This reduced the insertion loss between the beamforming antenna and the RF transceiver.