Cost-Effective VCOs Replace Power-Hungry YIGs

Phase noise is the curse of many a communications system, and one of the key performance parameters that most oscillators strive to minimize. System designers have long recognized the yttrium-iron-garnet (YIG) oscillator for its broadband, lownoise, high-frequency capabilities. But YIG sources are also power hungry and physically large. The mechanical design, with a YIG sphere mounted in the air gap of an electromagnet, is not conducive to integrated-circuit (IC) integration. And the sphere placement and tolerances required do not lend to high-volume production. The size of the sphere and the windings used for the electromagnetic field become prohibitive at resonance frequencies below about 2 GHz. In addition, YIG oscillators are sensitive to thermal drift, vibration, lighting, electromagnetic interference (EMI), microphonics, phase hits, and frequency modulation, all of which have a detrimental effect in designing modern communication systems. Fortunately, there is now an alternative source for tunable high-frequency signals with low phase noise: the distributed coupled YIG-replacement oscillator or DCYR series from Synergy Microwave Corp. (Paterson, NJ). The new patent-pending voltage-controlled oscillators (VCOs) are currently available for frequencies from 250 to 6000 MHz with typical measured phase noise of -132 dBc/Hz offset 100 kHz from carriers 250 to 1000 MHz.