**4. Conclusion**

The small signal characteristics of DDR IMPATTs based on GaAs designed to operate at mm-wave window frequencies such as 94 GHz, 140 GHz, and 220GHz are presented in this chapter. Both the DC and Small signal performance of the IMPATT diode based on GaAs are investigated by simulation technique. The results show that the DDR IMPATTs based on GaAs are most suitable device for generation of RF power with maximum conversion efficiency up to 220GHz. However, at higher mm-wave frequencies, the DDR IMPATTs based on GaAs surpass the other semiconductor material for IMPATT not only for frequencies below 94 GHz but also above 94 GHz. Thus, GaAs is a vibrant base semiconductor for IMPATT diodes at the both microwave and mm-wave frequencies and also for higher mm-wave frequencies greater than 94GHz. It is worthy indication of the future of communication technology.
