Low noise second harmonic Gunn diode oscillator using square-shaped slot line resonator

This paper presents a low noise second harmonic Gunn diode oscillator using square-shaped slot line resonator. A multi-layer MIC technology is adopted to reduce the circuit size of the oscillator. The oscillator consists of Gunn diodes, slot line resonators and microstrip lines. The Gunn diodes are embedded in the slot line resonators. The output circuit is formed using the microstrip line. A second harmonic signal can be obtained from the output circuit. A square-shaped slot line resonator is used in order to achieve the low phase noise and the suppression of undesired harmonics. The second harmonic oscillator is designed and fabricated in K band. The output power is +8.89 dBm at the design frequency of 18.75 GHz (2f₀) with the phase noise of -116.2 dBc/Hz at the offset frequency of 1 MHz. Excellent suppression of the undesired fundamental frequency signal (f₀) of -33 dBc is achieved. Moreover, the circuit size is reduced by three-tenths relative to that of the previous model of the proposed oscillator.