FR4-Based Low Phase Noise SISL VCO Using Tunable Weakly Coupled Resonators

In this letter, a voltage-controlled oscillator (VCO) with low cost, wide-tuning range, and low phase noise is proposed based on substrate integrated suspended line (SISL) technology. Benefiting from the weak coupling between half-wavelength resonators, the
$Q$
value can be improved, so as to reduce the phase noise of the VCO. By introducing a varactor in the high-
$Q$
resonator, a wide-tuning range is achieved. All the used boards choose FR4 material with very low cost. The designed SISL VCO has a tuning range of 380 MHz and has a phase noise of −122.81 dBc/Hz at a 1-MHz offset relative to the 5.88-GHz carrier. Compared with the existing board-level VCOs, this design features a wide-tuning range and low phase noise based on a low-cost platform.