Kang Wook Kim

A New Ultra-wideband Microstrip-to-CPS Transition

A novel ultra-wideband microstrip-to-CPS (coplanar stripline) transition has been developed. The transition is designed to provide the field and impedance matching between adjacent transmission lines. The proposed design is applicable to substrates with any dielectric constant. The transition provides the balun role as well as the impedance transformation. The fabricated transition in back-to-back configuration provides the insertion loss less than 1 dB per transition and the return loss better than 10 dB for frequencies from 5.39 GHz to over 40 GHz. In addition, a simulation study indicates that this transition can possess a 3 dB bandwidth of ~ 100 GHz.

An ultra-wideband microstrip-to-CPW transition

A new design for an ultra-wideband microstrip-to-CPW (coplanar waveguide) transition is presented. The proposed transition provides the field and impedance matching between adjacent transmission lines by ground shaping. Clear design guidelines are provided to determine the ground shape and the transition length. As design examples, two transition designs for substrates with low (2.2) and high (10.2) dielectric constants are presented. The fabricated transitions in back-to-back configuration provide insertion loss less than 0.7 dB per transition and return loss better than 10 dB for frequencies from 7 GHz to over 40 GHz and from DC to over 20 GHz, respectively.

New dielectric-covered waveguide-to-microstrip transitions for Ka-band transceivers

New dielectric-covered waveguide-to-microstrip transitions at Ka-band have been developed. These transitions are probe-type, but the dielectric material completely covers the waveguide opening in order to provide a moisture barrier and robustness. These transitions are also designed to be less sensitive to fabrication tolerances. The transition structures have been comprehensively analyzed using a 3-D EM software. The resonance phenomena caused by the waveguide-wall discontinuity have been removed by placing vias around the waveguide aperture. These transitions have also been fabricated and measured. The measured insertion loss of the transition is less than 0.4 dB and the return loss is about 15 dB over the entire Ka-band.

A simplified design of quasi-Yagi antennas using the new microstrip-to-CPS transitions

A new, systematic, simplified design procedure for quasi-Yagi antennas is presented. The design is based on the simple impedance matching among antenna components: i.e., transition, feed, and antenna. This new antenna design is possible due to the newly developed ultra-wideband transition. As design examples, wideband quasi- Yagi antennas are successfully designed and implemented in Ku- and Ka-bands with frequency bandwidths of 53.2% and 29.1%, and antenna gains of 4-5 dBi and 5.2-5.8 dBi, respectively. The design method can be applied to other balanced antennas and their arrays.

Design of bow-tie-type UWB antennas using an ultra-wideband balun

A new UWB antenna in bow-tie-type has been designed and implemented by utilizing the new ultra-wideband balun. In order to reduce antenna size, the balun is bended without sacrificing the balun performance. The fabricated antenna provides the operating frequency ranges from 3.2 to 11.2 GHz covering for the whole UWB frequency. The antenna maintains gains from 2.5 - 4.9 dBi for the operating frequencies with quasi- omni directional radiation patterns.

A planar ultra-wideband balanced doubler

A new low-cost design for a planar balanced doubler with ultra-wide bandwidth is presented. This doubler utilizes two types of ultra-wideband transitions: microstrip-to-CPW (coplanar waveguide) and microstrip-to-CPS (coplanar stripline) transitions. The transitions are designed to provide field and impedance matching between adjacent transmission lines. The fabricated doubler provides less than 10 dB conversion loss for output frequencies from 9 GHz to 26 GHz and less than 12 dB conversion loss from 7 GHz to 38 GHz.

Broadband antennas using a planar ultra-wideband balun

Ultra-wideband antennas can be systematically and simply designed utilizing a new ultra-wideband planar balun, which is a microstrip-to-CPS (coplanar stripline) transition. The new balun has the operating bandwidth of over 40 GHz. With the proposed balun as an antenna feed, design examples of three types of antennas are presented. Comparisons of simulated and measured results demonstrate validity of the design procedure.

Implementation of a phase-locked loop clock recovery module for 40 Gb/s optical receivers

A low-cost, high-performance clock recovery (CR) module using a phase-locked loop (PLL) for 40 Gb/s optical receivers have been successfully designed and implemented. The recovered 40 GHz clock is synchronized with a stable 10 GHz VC-DRO. The timing jitter of the implemented PLL clock recovery module is significantly reduced as compared with the conventional open-loop type clock recovery module with a DR filter. The measured RMS jitter with the phase-locked CR module is about 250 fs. In addition, the CR module has been operated error-free during a 30-minute BER test with 40 Gb/s optical transceivers.

Resonant transmission enhancement with a subwavelength aperture

We have considered the degree of enhancement in the transmitted power through the subwavelength aperture, which can be achieved by introducing some perturbation in small aperture shape. The maximum transmission condition has been described from the viewpoint of equivalent circuit representation. This study may find applications such as optical data storage and nanolithography as well as small aperture-type antenna design.

A new 40 GHz analog phase shifter using phase-locked loops

A new analog phase shifter at 40 GHz using phase-locked loops have been successfully designed and implemented. With this phase shifter, a 40 GHz input signal is synchronized with a stable 10 GHz oscillator, phase-shifted with a reflection-type phase shifter at 10 GHz, and then quadrupled by a multiplier. The implemented phase shifter achieves continuous phase shift from 0/spl deg/ to 640/spl deg/ at 40 GHz.