Fully Automatic Laser-Adjustable Ka-Band Phaselocked Ring Resonator Signal Source

A new and very compact Ka-Band local oscillator for point-to-multipoint (PMP) radio link systems has been developed. The local oscillator consists mainly of a voltage controlled oscillator with a planar ring resonator (RR-VCO) and a GaAs-pHEMT microwave monolithic integrated circuit (MMIC), a sampling phase detector (SPD) and a control circuitry including PLL amplifier and filtering. The ring resonator operates at harmonic frequencies. An innovative fully automated active laser-trimming procedure is used to adjust the frequency, the varactor tuning sensitivity and the electrical length between the ring resonator and the MMIC of the free-running oscillator. In addition, laser-trimming is used to adjust the symmetry of the sampling phase detector, the symmetry of the PLL amplifier as well as the attenuation of an adjustable attenuator between the output of the RR-VCO and the RF input of the SPD. A single side-band phase noise of approx. -110dBc10dBc/Hz is achieved for offset frequencies between 10kHz and 4MHz. In addition, the laser tuneable frequency tuning range is larger than 10% without any significant change of the VCO's characteristics. The temperature drift of the oscillator frequency is less than 4ppm/K. The attenuation of the laser adjustable attenuator can be adjusted in the range between 0.4dB and 11dB.