The code is based on Matlab 2018b, Yalmip and Mosek 8, but applied to other versions.
Details of installing Yalmip and Mosek in Matlab can be found in links: 
https://yalmip.github.io/tutorial/installation/
https://docs.mosek.com/9.1/toolbox/install-interface.html

Note: A free personal academic licence can be requested from Mosek: https://www.mosek.com/products/academic-licenses/.

The folder includes:

1 - Main_file.m

2 - Attenuation_observer.m
3 - Attenuation_Closed_sys.m

4 - Partial_observer.m
5 - Partial_Closed_sys.m

6 - Proposed_observer.m
7 - Proposed_Closed_sys.m

6 - Draw_figures.m

Way to run the code:
Open and run "Main_file.m", it will automatically call the other files.