## 6 Conclusions  
A novel design of a single-channel arrangement for the CTS system is introduced in this paper. By adding an additional source, a mixer, and a splitter\(\backslash\)combiner, one channel of the classical CTS system is replaced. The output pulses from the two simulation models with ideal devices match well. Considering the introduced nonideal devices of the mixer and power splitter\(\backslash\)combiner, the main influence is that differences exist between the amplitudes of the output pulses, which have been observed both in results of the simulation model with nonideal devices and in the real hardware circuit experiment. Generally, the amplitude differences of output pulses can be compensated in the later digital signal processing. The dispersion of the introduced mixer, power splitter, and combiner is usually very small, and its influence on signal resolution can be ignored. In addition, the experimental results indicate that the retrieved instrument's spectral resolution is particularly close to the maximum achievable spectral resolution of the expander-compressor arrangement.  
Compared to the classical two-channel arrangement CTS structure, the novel single-channel structure can save three amplifiers, two filters, a SAW filter, and a switch. The structure of the CTS system is simplified due to the saved active devices. The matching problem between the two channels is ignored and the sequential control system can be simplified. This indicates that the novel single-channel CTS system may have the potential feasibility for practical application. However, as the simulation and experiment only focus on the signal detection and fundamental spectral analysis without real SAW filter and the subsequent signal processing, there still exists some main characteristics (such as the system linearity and power spectral density accuracy) of the CTS system needing further investigation. Even though the single-channel structure is simple, the introduced mixer and power splitter\(\backslash\)combiner may cause uncertain signal interference influencing the system performance, which would not occur in the classical two-channel structure. An additional data compensation procedure is also needed in the subsequent signal processing which will increase additional power consumption. Further research will be focused on compensating actual measured data in the later digital signal processing; investigating the implementation of the novel signal-channel CTS system with real SAW filter and subsequent signal processing; and evaluating system performance with other main characteristics of power spectral density accuracy, linearity, and sensitivity, along with the front-end antenna system and the retrieval algorithm.  
Conceptualization, Q.Z. and L.T.; methodology, Q.Z.; validation, Q.Z., L.T., and B.G.; formal analysis, Q.Z.; resources, Q.Z.,L.T., and B.G.; writing-original draft preparation, Q.Z.; writing-review and editing, Q.Z. and L.T.; funding acquisition, L.T. All authors have read and agreed to the published version of the manuscript.  
This work was funded by The Pre-research Project of Civil Aerospace Technology of China (D040109).  
The authors would like to thank Prof. [PERSON] for the supply of the AWC (7082c) for experiment.  
The authors declare no conflict of interest.