Compact and low phase-noise dual-frequency oscillator based on dual-band filter with multiple coupling technique

This paper presents a switchable feedback dual-frequency oscillator with ultra low phase-noise based on dual-band filter for the first time. The application of multiple coupling technique in dual-band filter such as direct coupling, indirect coupling, self-coupling and source-load coupling not only reduces the circuit size significantly but also obtains high group delay that the ultra low phase-noise can be achieved. Due to the auxiliary oscillating network, two different oscillation frequencies are switched independently without inter-modulation. For demonstration, a physical prototype was fabricated and measured. The measured results show that the proposed dual-frequency oscillator can oscillate at 887 MHz or 2.446 GHz by controlling four PIN diode switches and the phase-noise keeps better than −139 dBc/Hz and −136.1 dBc/Hz at 1 MHz frequency offset. And the output power of 887 MHz and 2.446 GHz are 5.94 dBm and 5.08 dBm respectively.