Compact and Low-Phase-Noise Oscillator Employing Multilayer Sixteenth-Mode Substrate-Integrated Waveguide Filter for 5G Applications

In this paper, a compact and low-phase-noise (PN) free-running oscillator designed by sixteenth-mode substrate-integrated waveguide (SMSIW) bandpass filter (BPF) for 5G applications is proposed. The size of SMSIW cavity exhibits only one-sixteenth of the conventional SIW cavity. The SMSIW BPF is designed by using multilayered printed circuit board (PCB) process, and the active circuits and power divider are positioned on the top layer and bottom layer, respectively. The vertical feedback is achieved by using feedlines of SMSIW BPF and metallic via-hole. A parallel feedback configuration oscillator with four-order cross-coupling SMSIW BPF has been designed, fabricated, and measured. The measured results show that at the oscillation frequency of 3.52 GHz with -1.5-dBm output power, the PN is -107.36 and -132.07 dBc/Hz at 100 kHz and 1 MHz frequency offset, respectively. The figure of merit (FOM) at 1-MHz frequency offset is -191 dBc/Hz. Moreover, the size of SMSIW BPF is only 0.267λ0 x 0.109λ0. The proposed oscillator effectively demonstrates the advantages of compact size and low PN.