In this paper, an L-band low phase noise evanescent-mode (EVA) cavity-based frequency synthesizer is developed, implemented, and experimentally validated. The oscillator is integrated on the substrate of a high- $Q$ ( $Q_{u}\geq 430$ ) EVA resonator board to reduce parasitics in the circuit. A piezoelectric actuator is used as a tuner. A phase-locked loop is used to control the output frequency. The frequency tuning range is from 1000 to 1700 MHz (1.7:1). The circuit achieves a phase noise as low as −94 dBc/Hz at 10-kHz offset, −122 dBc/Hz at 100-kHz offset, and −146 dBc/Hz at 1-MHz offset. The RMS jitter of the system is 267 fs at 1000 MHz. The frequency synthesizer consumes 64.3 mW without the active loop filter, which consumes 200 mW.