## 4 Dataset and Experimental Setups  
We use a self-developed UWB impulse radar for the experiments. The UWB impulse radar used consists of a pair of bow-tie antennas, a balanced pulse generator, a receiver, and a clock synchronization module, as shown in Figure 3. The balanced pulse generator is based on a Step Recovery Diode (SRD). At the receiver, the signal from the antenna is fed into the low noise amplifier (LNA), and the output is recorded by a 16-bit analog to digital \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Index** & **Input Size** & **Operator** &
\begin{tabular}{c} **Kernel** \\ **Size** \\ \end{tabular} & **Stride** & **Padding** & **Output Size** \\ \hline
1 & \(1\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(64\times 800\times 600\) \\
2 & \(64\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(128\times 800\times 600\) \\
3 & \(128\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(256\times 800\times 600\) \\
4 & \(256\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(128\times 800\times 600\) \\
5 & \(128\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(64\times 800\times 600\) \\
6 & \(64\times 800\times 600\) & Conv2d & \(3\times 3\) & \(1\times 1\) & \(1\times 1\) & \(1\times 800\times 600\) \\
7 & \(1\times 800\times 600\) & Pooling & - & - & - & \(1\times 800\times 1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Detailed overall CNN architecture parameters. converter (ADC) with a maximal sampling rate of 160 Mbps and a full-power bandwidth of 1.4 GHz. To reduce the system cost and improve the spurious-free dynamic range (SFDR), the equivalent-time sampling technique was adopted. One Micrel's SY89297U programmable delay line, which can achieve a maximal delay of 5 ns with 5 ps fine increments, was used to provide a fine delay to the ADC sampling clock. Additionally, a Xilinx Artix-7 Field Programmable Gate Array (FPGA) was used to control the entire system and provide trigger signals to the transmitter, ensuring the synchronization of the whole system by locking these signals to the common clock. A pair of folded bow-tie antennas were used for electromagnetic radiation and reception, whose basic geometry is combined by a novel acorn-shaped bent bow-tie patch and a hollowed stepped back cavity [54]. The UWB impulse radar can be operated remotely for target detection experiments. In this way, there is no operator interference during experiments. The key parameters of the UWB impulse radar used are shown in Table 2. The slow-time sampling rate reaches 15 Hz, which is fast enough to acquire the respiratory signal of the human target according to the Nyquist theorem. To improve the SCNR of the radar echo data, each range profile is obtained by averaging 128 range profiles. The scenarios for dataset collection are shown in Figure 4. We conduct dataset collection in three scenarios. Scenario 1 is a standard brick wall in a gymnasium. The thickness of the wall is 40 cm. Up to three stationary human targets are breathing steadily in the detection area. The UWB impulse radar is placed on the other side of the wall for data collection. In each experiment, the location of the target is random. The maximum range between the target and the radar is 11 m, and the maximum angle is 60\({}^{\circ}\). The minimum spacing between targets is 30 cm. The wall in Scenario 2 consists of three media, namely, brick wall, floor, and wood. The thickness of each medium is 30 cm, and the total thickness of the wall is 90 cm. Similar to Scenario 1, the UWB impulse radar is placed on one side of