Design and implementation of a low cost L-band voltage controlled oscillator

This research introduces a novel, low-cost L-band voltage controlled oscillator (VCO) architecture that achieves exceptional performance metrics while utilizing cost-effective FR4 substrate and surface-mount components. The prototype achieves comparable spectral purity at roughly half the fabrication cost of an equivalent Rogers 4350B design, confirming the effectiveness of the proposed FR4-based low-cost topology. The proposed design achieves a 48.9% tuning range from 0.985 to 1.647 GHz-significantly exceeding previously reported FR4-based VCOs-while maintaining an average output power of 13.13 dBm and phase noise of -131.13 dBc/Hz at 1 MHz offset. Key innovations include a differential negative-resistance amplifier topology that ensures unconditional instability across the operational band and a butterfly-shaped low-pass filter that provides superior harmonic suppression. Experimental results validate the design methodology, demonstrating performance comparable to high-end Rogers-based implementations at a fraction of the cost. This work establishes that strategic circuit architecture can overcome FR4 substrate limitations, enabling high-performance L-band VCOs suitable for radar, satellite, and communication systems where cost-effectiveness is paramount.