## 3 Experiment Setup  
### Experimental System Setup  
Figures 3 and 4 illustrate the signal flow and the physical layout of the THz wireless communication test platform, respectively. At the transmitter, the upconversion module consists of a frequency multiplier chain (including one frequency doubler and two frequency triplers) and a mixer, both based on Schottky diode technology. The frequency multiplier chain upconverts the local oscillator (LO) signal, with an input power range of 3-6 dBm, to any carrier signal between 220 GHz and 330 GHz. The mixer modulates the upconverted carrier signal with the IF signal carrying the information, which has a maximum input power of \(-10\) dBm, and the double-sideband conversion loss is 10 dB. The maximum output power of the upconversion module is \(-15\) dBm. After generating the terahertz signal, the upconversion module transmits it through a horn antenna with a gain of 20 dBi into the indoor channel. To generate the local oscillator (LO) signal, the R&S (Rohde & Schwarz, Munich, Germany) SMB100A RF and microwave signal generator (MSG) is used, which can produce highly stable sinusoidal signals in the range of 100 kHz to 40 GHz. The LO signal is then output through a power splitter to the transceiver upconversion module. For generating the intermediate frequency (IF) signal, the PXIe-5841 vector signal transceiver (VST) is employed. This instrument integrates a vector signal generator (RF output path), a vector signal analyzer (RF input path), high-speed serial interfaces, and an FPGA for real-time signal control. The PXIe-5841 combines the flexibility of a software-defined radio (SDR) architecture with the high performance of RF instruments. In this platform, the PXIe-5841 receives baseband I/Q signals from the embedded controller PXIe-8881 through the PXIe bus. These signals are captured by the FPGA and converted via two DAC channels with a maximum sampling rate of 1 GS/s. The signals are then upconverted by the RF output submodule into IF signals with an instantaneous RF bandwidth of up to 1 GHz, covering a range from 125 MHz to 6 GHz. On the receiving end, the THz signal is downconverted by a downconversion module matching the transmitter's setup, and the downconverted IF signal is received by the PXIe-5841. The signal is further downconverted to baseband through the corresponding RF input submodule, then collected as baseband I/Q digital signals via two ADC channels and sent to the embedded controller. To further amplify the received signal, a low-noise amplifier (LNA) can be used. Since designing a low-noise amplifier (LNA) with low phase noise (NF) in the high-bandwidth terahertz frequency range is challenging, the platform utilizes an LNA at the IF stage, which operates at a frequency range of 1-6 GHz with a gain of 30 dB. The baseband digital signal processing in the physical layer is implemented in a software-defined manner on the embedded controller PXIe-8881. At the transmitter, LabVIEW is used to construct user-defined information data into frames, which are processed through constellation mapping, pulse shaping, and other steps to generate baseband I/Q signals. These signals are then sent to the VST via the PXIe backplane. Similarly, at the receiver, LabVIEW is used to perform matched filtering, synchronization, and other processing on the baseband I/Q signals, which are then sent to a Python node as the training  
Figure 3: Signal flow chart of the THz wireless communication system performance test platform. The system consists of baseband signal generation and receive signal processing modules (LabVIEW), PXIe-based transceiver (VST), upconversion and downconversion chains based on Schottky diode mixers and multipliers, and a single carrier antenna. The communication link operates under indoor line-of-sight (LoS) conditions in the frequency range of 220 to 330 GHz. dataset for deep learning. The equalization training and equalization processes are conducted offline in Python.