Due to the widespread of IoT, it is thought that frequency will become tight even in short distance communication between several meters in the future. In contrast, the sub-mW or less power consumption in wireless communication circuit is desired. Our group presented the circuit technology achieve high spectrum efficiency of 3.3 b/s/Hz while consuming about 100μW. In this paper, we aim to further improve spectrum efficiency, and examine the possibility of high linearization of key RF mixer section. Circuit simulation resulted in the expectation that the reflection coefficient could be linearly controlled.