High-Q metamaterial interdigital transmission line based on complementary spiral resonators for low phase noise voltage-controlled oscillator

In this study, the high-quality factor (Q) metamaterial interdigital transmission line (TL) based on the complementary spiral resonators (CSRs) is presented for reducing the phase noise of the voltage-controlled oscillator (VCO). The high-Q metamaterial TL is realised by adopting the array of the CSRs etched on the ground plane and the interdigital centre line on the signal plane. The interdigital centre line on the signal plane has been used to obtain higher Q value than that of the conventional implementation. The resonance properties and inherent Q value saturation of the proposed high-Q metamaterial interdigital TL have been analysed as follows: width of the centre line on the signal plane, dimensions of the CSRs, current directions between the CSRs, number of the unit cell-pair of the CSRs and whether or not there is the interdigital structure. The phase noise and tuning range of the proposed VCO are -127.50 to -124.87-dBc/Hz at 100-kHz and 5.744-5.86-GHz.