Design of Cartesian Feedback Loop Linearization Chip for UHF Band

In this paper, the designed and implemented results of CFL linearization chip which can be used in mobile radio and TRS terminal of UHF band(380~910 MHz), using BiCMOS process based on Si, are shown. As gain control circuits for modifying transmit power are inserted not only in feedback path but also in forward path, the stability of CFL is maintained. And, DC-offset correction function of S/H structure, which is suitable for walkie-talkie PTT operation and is easily implemented, is realized. The performance test results of transmitter show that the regulation of FCC emission mask at PEP 3 W(34.8 dBm) is satisfied when the CQPSK modulated signal is fed and more than 30 dBc improvement of 3rd order IMD is achieved when two-tone signal is inputted.