An injection locked oscillator for direction-conversion BPSK modulation applications

A microwave binary phase shift keying (BPSK) modulation method is presented in the paper. An injection locked oscillator (ILO) operating in 5.8GHz ISM band is developed to demonstrate the approach using hybrid integrated microwave circuit technique. The developed ILO showed the free-running performance with an output power of 2.67dBm at 5.8GHz, DC-to-RF efficiency of 26.6% and phase noise of -116.8dBc/Hz at 100kHz offset under dc bias of 1.881V and 3.69mA. Under the locked state by a 5.8GHz injection signal of -25dBm, the ILO acquired the output signal phase-shift of 180° with 27.67dB locking-gain by altering the dc bias. The experimental results shown the exact anti-phase output signals from the ILO are achievable in the frequency range from 5.795GHz to 5.805GHz by modulating the dc bias under the locked state by the corresponding locking signal of -25dBm. As a sequence, the ILO can function as a direct-conversion BPSK modulator.