A triple band travelling wave VCO using digitally controlled artificial dielectric transmission lines

A compact, triple output travelling wave oscillator with combined analog and digital control is presented. The oscillator is based on an eight phase rotary travelling wave oscillator employing shielded digitally controlled transmission lines. The oscillator drives an output buffer, a push-push buffer and a quad-push to generate X, K and Q band outputs simultaneously. Fabricated in standard 0.18μm CMOS it occupies 0.48 mm² and consumes a DC power of 64mW, including pads and buffers. The circuit exhibits 5.5% tuning range in each band with potential 1MHz digital step resolution. With a phase noise of -108 dBc/Hz at 1MHz offset and -1dBm of output power measured at the fundamental frequency, the circuit is a promising candidate for mm-wave software defined radios and digitals PLLs.