Jaeheung Kim

Concurrent Dual-Band Class-E Power Amplifier Using Composite Right/Left-Handed Transmission Lines

A concurrent dual-band class-E power amplifier using composite right/left-handed transmission lines (CRLH TLs) is proposed. Dual-mode operation is achieved by using the frequency offset and nonlinear phase slope of CRLH TLs for the matching network of power amplifiers. The frequency ratio of two operating frequencies is not necessarily an integer. Two operating frequencies are chosen as 836 MHz and 1.95 GHz for simulation. Three methods for designing a CRLH TL power amplifier are proposed. The measured results based on one method show that output powers of 22.4 and 22.2 dBm were obtained at 800 MHz and 1.70 GHz, respectively. In terms of maximum power-added efficiency, we obtained 42.5% and 42.6% at 800 MHz and 1.70 GHz, respectively.

Beamforming Lens Antenna on a High Resistivity Silicon Wafer for 60 GHz WPAN

Wafer-scale beamforming lenses for future IEEE802.15.3c 60 GHz WPAN applications are presented. An on-wafer fabrication is of particular interest because a beamforming lens can be fabricated with sub-circuits in a single process. It means that the beamforming lens system would be compact, reliable, and cost-effective. The Rotman lens and the Rotman lens with antenna arrays were fabricated on a high-resistivity silicon (HRS) wafer in a semiconductor process, which is a preliminary research to check the feasibility of a Rotman lens for a chip scale packaging. In the case of the Rotman lens only, the efficiency is in the range from 50% to 70% depending on which beam port is excited. Assuming that the lens is coupled with ideal isotropic antennas, the synthesized beam patterns from the S-parameters shows that the beam directions are -29.3°, -15.1°, 0.2°, 15.2°, and 29.5 °, and the beam widths are 15.37°, 15.62°, 15.46°, 15.51°, and 15.63°, respectively. In the case of the Rotman lens with antenna array, the patterns were measured by using on-wafer measurement setup. It shows that the beam directions are -26.6°, -21.8°, 0°, 21.8°, and 26.6° . These results are in good agreement with the calculated results from ray-optic. Thus, it is verified that the lens antenna implemented on a wafer can be feasible for the system-in-package (SiP) and wafer-level package technologies.

Compact Two-Layer Rotman Lens-Fed Microstrip Antenna Array at 24 GHz

This paper presents a new design to realize a compact Rotman lens-fed antenna array. The lens-fed antenna has the form of two layers, which is a new approach to reducing the size of the Rotman lens. The approach is demonstrated at 24 GHz aiming for an automotive sensing radar. The lens consists of a top metal layer, a dielectric, a common ground, a dielectric, and a bottom metal layer, in sequential order. The layout of the lens body is placed on the bottom layer and the antennas are placed on the top layer. Both of them are electrically connected through slot transitions. This two-layer structure reduces not only the total size of the lens, but also the loss of the delay lines because the lines can be designed to be as short and straight as possible. The two-layer Rotman lens-fed antenna array is measured in terms of scattering parameters and beam patterns. From the scattering parameters, the power efficiencies of the beam port 1, 2, and 3 at 24 GHz are obtained as 32.3%, 48.5%, and 50.8%, respectively. The measured beam patterns show that the beam directions are -28.1°, -14.9°, 0°, 15.5°, and 28.6° and the beamwidths are 13.4°, 13.2°, 12.8°, 13.5°, and 13.0°. The measurements confirm that the compact two-layer Rotman lens has been successfully demonstrated.

A dual band printed dipole antenna with spiral structure for WLAN application

In this letter, the design procedure and electrical performance of a dual band (2.4/5.8GHz) printed dipole antenna using spiral structure are proposed and investigated. For the first time, a dual band printed dipole antenna with spiral configuration is proposed. In addition, a matching method by adjusting the transmission line width, and a new bandwidth broadening method varying the distance between the top and bottom spirals are reported. The operating frequencies of the proposed antenna are 2.4GHz and 5.8GHz which cover WLAN system. The proposed antenna achieves a good matching using tapered transmission lines for the top and bottom spirals. The desired resonant frequencies are obtained by adjusting the number of turns of the spirals. The bandwidth is optimized by varying the distance between the top and bottom spirals. A relative position of the bottom spiral plays an important role in achieving a bandwidth in terms of 10-dB return loss.

Dielectric slab Rotman lens for microwave/millimeter-wave applications

A new form of a Rotman lens is proposed for microwave/millimeter-wave applications such as a collision-avoidance radar. The proposed lens can be described as a dielectric slab fed by slot lines. The new form is expected to show lower loss and lower mutual coupling than the conventional Rotman lenses fabricated with conducting plates at millimeter-wave frequency. Taking the field distribution inside the dielectric slab into account, the TE/sub 0/ mode was chosen to excite the dielectric slab lens. The dielectric Rotman lens consists of a dielectric slab, tapered slot structure, and the transitions between the antipodal slots and microstrip lines for subminiature A connectors. The conventional design equations have been modified for use in designing the dielectric slab Rotman lens with a high dielectric material. A prototype was implemented with nine beam ports and nine array ports. Measurements from 10 to 20 GHz show that mutual coupling can be lowered at higher frequency. The obtained efficiency of the dielectric slab lens system is approximately 30%. The efficiency of the lens is comparable to that of the conducting plate lenses even though there is a spillover loss from the dielectric slab.

Dual- and Triple-Mode Branch-Line Ring Resonators and Harmonic Suppressed Half-Ring Resonators

Ring resonators have been widely used for various applications. Dual-mode ring resonators have also been investigated due to their applicability to multifrequency mode requirement. In this paper, dual-mode ring resonators using a branch line are designed along with a systematic approach. Triple-mode branch-line ring resonators are also designed adding two branch lines to the ring resonator. Adding more branch lines, multimode resonators can be realized based on the design procedure developed here. The location of the branch lines determines the additional resonant frequencies other than the fundamental resonant frequency generated by the enclosing ring. Furthermore, half-ring resonators working at 2.5 GHz are proposed for suppressing multiple harmonics (second and third harmonics) and providing size reduction with employment of various physical configurations. Equalizing the even- and odd-mode phase delays, harmonics are suppressed effectively in the design of half-ring resonators. Double half-ring resonators with a long opening gap are investigated to continuously decrease the resonant frequency. An open-loop structure provides flexible design and lowers the resonant frequency. Two dual-mode ring resonators and one triple-mode ring resonator are simulated and fabricated along with three different half-ring resonators

A high linearity chireix outphasing power amplifier using composite right/left-handed transmission lines

A high linearity Chireix outphasing power amplifier using composite right/left-handed transmission lines (CRLH-TL) is proposed at 2.4 GHz. The 180deg hybrid power combiner including CRLH-TL is designed to suppress the second and third harmonics. The output matching circuit is optimized for suppressing the second and third harmonics. The output power at the fundamental frequency shows 32.1 dBm, whereas the second harmonic shows -19.5 dBm and the 3rd harmonic -22.3 dBm as simulation results with 20 dBm input power excited. The class-E amplifiers are utilized for maintaining high efficiency for this work.

High quality-factor and inductance of symmetric differential-pair structure active inductor using a feedback resistance design

This paper proposes a new symmetric differential-pair structure for the active inductor. The CMOS spiral inductor occupies a large chip size and is difficult to obtain a high Q-factor. A symmetric differential-pair active inductor circuit topology with feedback resistor is proposed, which can substantially improve its equivalent inductance and quality-factor. This feedback resistance differential-pair active inductor was implemented by using 0.18-μm TSMC RF CMOS technology, which demonstrates a maximum quality-factor of 28 with a 27-nH inductance. The proposed active inductor has one hundredth of chip size of a spiral inductor and it also shows more than ten times wide dynamic range and twice higher Q-factor compared to the conventional 1-port active inductor circuits. In addition, this configuration can be easily implemented using the series circuit.

836 MHz/1.95GHz Dual-Band Class-E Power Amplifier Using Composite Right/Left-Handed Transmission Lines

A dual-band Class-E power amplifier using composite right/left-handed transmission lines is proposed. Dual-mode operation is achieved by the frequency offset and nonlinear phase slope of CRLH TL for the matching network of power amplifiers. The frequency ratio of two operating frequencies is not necessarily an integer. Two operating frequencies are chosen 836MHz and 1.95GHz in this work. The simulated results show that output power of 24.9 and 24.1 dBm was obtained at 836MHz and 1.95GHz, respectively. In terms of maximum PAE, we obtain 48.63% and 48.29% at two operating frequencies

A new vertical half disc-loaded ultra-wideband monopole antenna (VHDMA) with a horizontally top-loaded small disc

In this paper, a new vertical half disc-loaded monopole antenna (VHDMA) with a horizontally top-loaded small disc is investigated. This antenna provides a similar radiation pattern compared to that of the simple monopole antenna, a wide input impedance bandwidth, and a very small size. The radiation pattern of the proposed VHDMA in the azimuthal direction is almost omnidirectional, which is usually required for the design of conventional monopole antennas. In addition, the simulation and measured results show that the return loss characteristic of the VHDMA provides a considerably large bandwidth even with a small radiating area. Comparing the measured results of a circular and a half-circular disc-loaded monopole antenna with a small disc mounted on the top, it is found that the half-circular disc-loaded monopole antenna with a mounted disc is comparable to the circular disc-loaded monopole antenna with respect to size and electrical performance. Surface wave and dielectric loss are often caused by the printed antenna with a high dielectric constant, whereas they are not generated by metallic planar antennas by realizing a good impedance matching and avoiding lossy matching units. This implies that antenna return loss is directly related to antenna radiation efficiency.