# Detection of Quasi-Static Trapped Human Being Using Mono-Static UWB Life-Detection Radar
## 2 Material and Methods
### The UWB Life-Detection Radar Hardware System Design
#### 2.1.3 The Design of Single Golay-Coded Radar  
The key components of the Golay-coded radar are a digital transmitter, a dual-channel receiver, a clock manager, a network clock, a self-positioning module and a wireless communication module, which are shown in Figure 1. The radar uses low sidelobes sinusoidal modulation Golay complementary coded signal with a center frequency of about 1 GHz as the transmit signal, which can improve the SNR [27; 28; 29; 30]. To reduce the system cost and improve the spurious-free dynamic range (SFDR), the equivalent-time sampling technique is adopted. A Xilinx Artix-7 field-programmable gate array (FPGA) is used as the main control unit to manage the peripherals. A 16-bit analog to digital converter (ADC) with a maximal sampling rate of 160 million bits per second (Mbps) and a full-power bandwidth of 1.4 GHz is used for the receiver. A 14-bit digital to analog converter (DAC) at 2.5 Gigabit samples per second (GSPS) update rate is used for the transmitter. A W5300 chip is used for exchanging the raw radar data and commands with the control host by Transmission Control Protocol (TCP) network protocol, and the wireless bridge realizes the wireless communication. A pair of bow-tie antennas are used for electromagnetic radiation and reception. The prototyped radar system and its antennas is presented in Figure 2.  
Figure 1: The block diagram of the Golay-coded radar. Figure 2: The prototyped radar system (**left**) and its antennas (**right**). 2.1.4. The Additional Modules for Scanning Operating Mode  
In the scanning operating mode strategy, radars are deployed at different observation points with TDM architecture, executing electromagnetic detection in their own time slices. The network clock module and self-positioning module are adopted as additional modules to achieve the multiple observation points. The network clock module avoids mutual interference between Golay-coded radars during the detection process via setting a time margin and executing wireless clock synchronization. Here, the module is designed based on Texas Instruments' CC1310 chip and a counter in FPGA. The CC1310 provides a set of timers and taggers for radio operation by Sub-1 GHz technology. By sending and receiving synchronization requests twice, the modules can measure the difference value of the local network clocks between two Golay-coded radars via the two-way synchronization algorithm [31]. The measured values are used to correct the different initial offset. By executing wireless clock synchronization and setting the time margin as ~15 ms, different initial offset and clock drift between Golay-coded radars could be corrected. The self-positioning module is deployed in each Golay-coded radar to sense the relative positions, as the relative positions are needed for the human respiration detection strategy. The automatic measure avoided manual measurement errors and time wasting. The DWM1000 is the critical component of the self-positioning module. It provides the function of timestamping and transmission times precise controlling and can be used in the two-way ranging with an error within 10 cm [32; 33; 34; 35; 36]. Here, the two-way ranging is realized by the double-sided two-way ranging algorithm executed in the STM32 Microcontroller Unit (MCU) to achieve the self-positioning of the Golay-coded radars. 2.1.5. The Workflow for Scanning Operating Mode  
The orderly collaboration between Golay-coded radars depends on the reasonable time slice management and workflow management, which are designed in accordance with the radar's parameters in Table 2.  
In the system's workflow, each time slice for the Golay-coded radar contains an electromagnetic detection and a data transmission. According to Table 2, the corresponding time consumption is about 17 ms for UWB A-scan and about 6 ms for data transmission. It means the minimum time slice is about 23 ms. Here, we set the time slice as 32 ms, and retained the time margin for wireless transmission and the network clock module.