A new wideband ring voltage-controlled oscillator (VOC) was proposed by UNIST undergraduate student, Seyeon Yoo, with the the research work published in IEEE Microwave and Wireless Components Letters (Ulsun, S. Korea).

Wideband VCO is a key component of an IR-UWB system (Impulse radio-Ultra-wideband) which has drawn attention as a practical technology for a Doppler radar system that can detect human vital signs such as heart beats and respiration.

The IR-UWB’s large signal bandwidth can yield an increased time resolution and its wide range of frequency bands is desirable because an optimal band can be selectively used to maximize detection accuracy.

With the new VCO designed by the UNIST research team led by Prof. Jaehyouk Choi and proposed by a UNIST undergraduate student, Seyeon Yoo, an operating frequency band is digitally set using a digital-to-analog convert (DAC) in the supply-voltage regulator.

Once a band is selected, the specific target-frequency is analogously tuned, controlling the strength of latches in delay cells. Furthermore, by storing the latches in each cell, the KVCO becomes scalable.

Ultimately, throughout the entire 2-8 GHz frequency band, the KVCO can be constantly maintained, which helps ensure the stable operation of the phase-locked loop (PLL).

“This technology will be applicable for IR-UWB based Doppler radar systems and various radio frequency (RF) semiconductor applications since it provides stable wideband frequency,” says Prof. Choi.

Speaking of Yoo, he says, “Developing an analog/RF integrated circuit (IC) chip requires extensive knowledge and know-how on IC designs. As an undergraduate student, developing a new IC and publishing a research paper in a leading science journal is a remarkable performance.”