Chong-Yi Liou

A Novel Triple-Band Microstrip Branch-Line Coupler With Arbitrary Operating Frequencies

This letter presents a novel microstrip branch-line coupler operating in three frequency bands. The design methodology of the triple-band branch-line coupler is established by using a compensation technique to improve the matching property within each passband region. The proposed coupler with compact size is realized by folded microstrip open-circuited and short-circuited stubs. The measured, full-wave simulated and equivalent-circuit modeled results illustrate good agreement among them, which validates the design method and shows the advantages of deep rejection between each operating frequency, and the dc grounded input and output ports.

Wireless charging system of mobile handset using metamaterial-based cavity resonator

A metamterial-based cavity resonator using artificial magnetic conductor surfaces is presented and applied to realize a wireless charging system of mobile handset. This wireless charging system demonstrates the advantages of broad bandwidth, small size, long transmitting range, high transferring efficiency and EMI-free feature. The holistic architecture of wireless charging system for a smartphone is established to experimentally validate the usefulness of the metamaterial cavity resonator.

Fully Monolithic BiCMOS Reconfigurable Power Amplifier for Multi-Mode and Multi-Band Applications

A power amplifier (PA) supporting wideband code division multiple access, long-term evolution (LTE), and wireless local area network applications has been implemented in 0.18- μm SiGe BiCMOS technology. The PA integrates a tunable input matching network, a broadband output matching network, and adaptive bias circuits in a single chip to achieve high linearity and high power in different modulation schemes and operating bands. The three-stage PA adopts a differential-type configuration without using through-silicon-via technology to deliver 4 1.3-42 dB of gain and 28.2-28.6 dBm of 1-dB compression output power with a 20.8-27.6% power-added efficiency (PAE) at 1.85-2.5 GHz. To further validate the usefulness of the proposed PA, the envelope-tracking PA is designed to improve the PAE by 6.5% within the linearity specification of a 24.7-dBm average output power and a -33-dBc adjacent channel leakage ratio for 2.35-GHz 16 quadrature-amplitude-modulation time-division LTE signal with 20-MHz bandwidth.

High-Power and High-Efficiency RF Rectifiers Using Series and Parallel Power-Dividing Networks and Their Applications to Wirelessly Powered Devices

The zero-bias and full-wave bridge rectifiers with high RF-to-dc conversion efficiency at high operating power are demonstrated. To overcome the low breakdown voltage limit of silicon-based Schottky diodes, the power-dividing networks are employed to couple the high-input RF power into four differential-type bridge diodes. Transformer-based one-to-four series and parallel power-dividing networks are proposed, and their equivalent circuits are established. To enhance the coupling mechanism of the transformer, the defected ground structures are adopted in the coupled-line sections of power dividing networks. The critical design parameters of power-dividing networks are examined, including the input impedance, the self-resonant frequency, the power loss factor, the phase and amplitude imbalances of differential signal, and the voltage and current on output ports. The bridge rectifiers using the series and parallel power-dividing networks are developed to withstand up to 41-dBm input power before reaching the breakdown limit of Schottky diode, and the RF-to-dc conversion efficiency is 62% for series power-dividing networks and is 76% for parallel power-dividing networks at the operating frequency of 920 MHz and load resistance of 10 Ω. The wireless charging system for a smartphone is established to experimentally validate the application of the high-power and high-efficiency RF rectifiers.

Triple-Band Marchand Balun Filter Using Coupled-Line Admmittance Inverter Technique

This study presents the first reported design and implementation of triple-band Marchand balun filter. The novel balun filter is constructed from the short-circuited coupled line with a triple-band resonator to demonstrate the triple-band admittance inverter characteristic. To improve the amplitude and phase responses within three passbands, the compensation techniques for phase-angle, impedance-matching, and susceptance-slope discrepancies are employed in the balun filter design. Four types of triple-band balun filters with significantly different bandwidths and passband separations are designed and the results are consistent with the specifications. The design procedure for the triple-band Marchand balun filter is established to obtain the amplitude and phase balances in three operating bands with arbitrarily controlled center frequencies and fractional bandwidths. The proposed Marchand balun filter realized by the microstrip coupled-line sections and the defected ground structure stubs is measured and a good agreement among equivalent-circuit calculation, full-wave simulation, and measurement is observed, demonstrating the validity and versatility of the proposed design methodology and balun filter configuration.

Wireless-Power-Transfer System Using Near-Field Capacitively Coupled Resonators

This brief presents the near-field capacitively coupled wireless charging system consisting of a transmitting dock resonator and a receiving multiband resonator. The transmitting dock resonator comprises a planar strip and a ring-shaped metal plate to deliver power to the multiple folded strips as the receiving 3-D multiband resonator at gigahertz band. The wireless charging system for a mobile handset is established to experimentally validate the application of the compact and high-efficiency capacitively coupled wireless charging system.

Triple-band microstrip Wilkinson power dividers with controllable frequency responses

The design methodology and implementation of two novel triple-band Wilkinson power dividers is presented. Based on the bandpass filter design with the compensation technique to improve the matching property within each passband region, two triple-band Wilkinson power dividers with Chebyshev response are realized by microstrip open and short stubs and patterned-ground-structure stubs, and are validated by the equivalent-circuit model, full-wave simulation, and measurement.

Printed spiral metamaterial resonators for ferrite-less wireless powering system with proximal metal plates

This study proposes the metamaterial-like printed spiral coil (PSC) without using ferrite film to improve the proximity effect of metal plate in wireless power transmission. This four-PSC system is experimentally and theoretically verified by power transmission, impedance matching, resonant frequency, and magnetic field distribution. Results demonstrate that the transmission of the four-PSC system is 10.5 dB higher than the conventional two-PSC system when the backside metal plates are added.

A novel wideband circularly polarized dual-fed slot antenna with microstrip feeding network

This study presents the design of novel dual-fed circularly polarized (CP) antenna. This antenna consists of a tapered slot, a backside metal plate and a microstrip-fed delay line phase shifter. Based on the analysis of the radiation mechanism of antenna ground plane, the edge shape is optimized as a half-circle type to enhance the bandwidth of antenna gain and CP purity. The proposed antenna possesses a wideband return loss better than 10 dB in the range of 4.18–7.57 GHz, covering the bandwidth of axial ratio lower than 3 dB from 4.25 to 6.75 GHz. The measured antenna gain is approximately 9–10.5 dBic and the radiation patterns are broadside and consistent within the CP operating bandwidth.

Coupling enhancement between monopole-type resonators using metamaterial cavity

This work presents the strong coupling of monopole-type resonators using a metamaterial cavity with artificial magnetic conductor (AMC) surfaces and metal planes. The AMC surface is constructed by an array of metal patches on a double-layered dielectric substrate backed by a metallic plane, and its reflection phase with respect to the angle and the polarization of obliquely incident plane waves are characterized by the transmission-line model. The measured transmission power is −2 dB when the resonator spacing is 0.4λ. This demonstrates that the power transfer is enhanced significantly by metamaterial cavity compared to the metal cavity and free space.