## 2 Materials and Methods
### Monitoring of Glacier Termini Movement Speed from GB Radar  
#### 2.2.1 GB Radar System and Parameters  
In Radio Frequency (RF) engineering, Vector Network Analyzer (VNA) is designed as an instrument for efficiently and accurately performing circuit or network analysis. The range of circuits that can be tested with VNA is extremely wide, from simple microwave devices such as filters, amplifiers, and mixers, to integrated microwave equipment. A Stepped Frequency Continuous Wave (SFCW) signal is an important form of signal composed of a series of continuous waves with linearly increasing carrier frequencies. The processing of single-frequency sub-signals by the receiver reduces its requirement for instantaneous bandwidth, making the synthesis of large bandwidth signals more convenient. By combining VNA with antennas and control computers, a radar system that emits SFCW signals can be formed. Based on the above considerations, an independent radar experimental system was built, which mainly consists of three parts: a standard gain horn antenna, VNA, and Programmable Computer (PC). The physical diagram of the system is shown in Figure 4, and the parameters are shown in Table 1.  
Figure 4: Physical diagram of the GB radar system. Figure 3: Topography and Sampling Area Map of Yangbulake Glacier, etc. Compared to the C band and Ka band, the Ku band has less spectral resource interference and lower atmospheric attenuation [35]. The dynamic range of the Ku frequency band can reach 100 dB, which is much larger than the difference in radar cross sections between strong and weak scattering targets. It has a better micro deformation measurement effect for weak scattering targets. This system uses a Ku band standard gain horn antenna with a gain of 20 dB, model XB-HA62-20S, produced by Beijing Xibao Electronic Technology Co., Ltd, Beijing, China. When the frequency is 16 GHz, the measured beam width is about 16\({}^{\circ}\), and the measured gain is about 16 dB, which can meet the measurement requirements. The antenna adopts a dual antenna structure with separate transmission and reception, which can simultaneously transmit and receive signals, improving the isolation between the receiving and transmitting links, while avoiding excessive coupling signals and reducing the dynamic range of the receiver [36]. The VNA used in this system is a dual port Ceyear3656D produced by Ceyear Technologies Co., Ltd, Qingdao, China. It can quickly and accurately measure the amplitude, phase, and other characteristics of the Scatter (S) parameter of the tested object and has wide applications in military [37; 38; 39], civilian [40; 41], and other fields. The VNA supports programmable programming interfaces such as General Purpose Information Bus (GPIB) and Local Area Network (LAN). These interfaces, combined with I/O libraries and the C++ programming language, can enable remote control of VNA. The radar system built in this article is interconnected with a PC through an LAN interface. The PC uses the Virtual Instrument Software Architecture (VISA) library to transmit Standard Commands Programmable Instrumentation (SCPI) commands to VNA to define the system's test parameters. The main parameters of VNA are shown in Table 2.  
The PC is used for system error correction and display of measurement data and also provides a user interface and remote control interface through software compilation. The PC mainly completes two functions: system control and data processing. In order to achieve remote control of VNA by the computer, the VISA library is pre-installed in the PC, providing a standard Input/Output (I/O) function library for instrument programming. SCPI defines standardized instrument program control messages, respons messages, status report structures, and data formats. Based on the Qt Creator 4.8.2 (software) programming environment, combining SCPI programmable commands, I/O library functions, and C++ programming language can remotely control VNA to achieve signal transmission and reception.