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This paper proposes a 5.8 GHz highly efficient rectifier design using harmonic termination for wireless power transfer. The diode used to convert the received RF power to DC is a non-linear device, and a harmonic component is generated, which causes performance degradation. Therefore, in this paper, we designed a band stop filter for harmonic termination and proposed the N-stage harmonic terminated voltage multiplier (N-stage HTVM). The number of stages N can be designed differently to operate with high efficiency at various input powers for the proposed rectifier. In the proposed rectifier circuit, mathematical analysis of output DC voltage, power loss of the diode, and the power conversion efficiency (PCE) were evaluated through voltage/current waveform analysis of the diode. The design method of the filter for terminating harmonics is presented. Furthermore, the change of PCE according to the increase in the number of stages was analyzed using the equivalent model of the proposed circuit and verified through measurement. The maximum PCE of one-stage HTVM was 68% when 18 dBm of input power was applied. The DC output voltage was measured to 11.6 V. When the RF input power was 25 dBm and the load was 1500 Ω, the maximum PCE of the two-stage HTVM was 71% and the maximum DC output voltage was measured as 15.8 V. The measured performance of three-stage HTVM had a PCE of 67% and DC output voltage of 19.8 V when the input power was 30 dBm.

This paper proposes a 7-way microstrip divider for hexagonal honeycomb structures. The honeycomb arrangement has advantages such as equidistant adjacent output ports and high space utilization. The structure comprises six output ports arranged hexagonally and one output port placed at the center of the hexagon in the same plane. To design such a divider considering the output ports' positions, this paper proposes the combination of a microstrip 6:1 unequal Wilkinson divider and a 6-way microstrip divider. To facilitate the implementation of the 6:1 unequal divider, including a transmission line with a high characteristic impedance, a microstrip coupler is used, and for the 6-way microstrip divider, a design scheme and analysis considering the impedance matching and isolation of the output ports are presented. Moreover, the ground layers of the two microstrip dividers are constructed in a back-to-back structure to minimize the size of the overall divider. For validation, a 5.8 GHz 7-way divider is designed, implemented, and measured. The measured S-parameters show that the proposed 7-way divider has appropriate return loss, insertion loss, isolation, and power distribution with a phase difference under 4.7°.

A magnetic resonance wireless power transfer (WPT) system achieves maximum power transfer efficiency (PTE) at the position where critical coupling occurs, but the PTE degrades significantly off this position. In this paper, we propose a new design technique that can achieve high PTE over a wide range by generating critical coupling at two other positions by using a switchless passive dual-matching technique. We present a receiver (RX) and transmitter (TX) configuration implemented with lumped elements for dual-matching and derive the values of each device analytically. A RX part is constructed by connecting parallel LC and C in series to resonate at two frequencies. Considering the mutual inductances between the TX and RX coil at two distances, T-type TX matching is designed to achieve conjugate matching at two resonant frequencies for the source impedance simultaneously. To verify the performance of the proposed technique, a WPT system with critical coupling at 25 and 75 mm for two frequencies of 4 and 6.78 MHz was implemented, and the PTE was measured. The average PTE in the range of 20–80 mm is 70%, and it is verified that the proposed technique can achieve robust WPT system to distance variation.

This paper proposes a behavioral modeling of multi-channel transmitter in microwave power transfer (MPT). An energy beam forming (EBF) is a key technology to solve the low energy transmission efficiency problem of MPT system. To use the EBF, the channel characteristics between receiver and array transmitter should be estimated. Unlike communication systems that use RF power amplifier (PA)s in the linear input range, to increase the transmission efficiency of the MPT system, it is necessary to utilize the maximum output range of the PA. We propose a method for performing nonlinear modeling of each transmitter channel using received signals by periodically changing the weight of the transmitter channels using the attenuator control on each channel. Polynomial model coefficients are extracted by Pseudo-inverse using the signals of each channel and the signal of the receiver. In MPTs with multiple transmitters, the proposed method can model characteristics of each transmitter channel efficiently. To validate the proposed method, we perform the proposed modeling for a 5.8GHz 16-channel phase array MPT system.

The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 &mu, m in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs&rsquo, catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs&rsquo, catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.

A coupling coefficient $k$ decreases as the size of the receiver coil decreases, when RF power is transmitted to small size devices such as implantable medical devices by magnetic resonant method. In this case, the rectifier efficiency using conventional voltage multiplier (CVM) is very low. The turn-on time of rectifying diode becomes unstable, when a low input voltage is applied to CVM, and power conversion efficiency (PCE) is reduced. In order to overcome this problem, we present novel voltage multiplier with second harmonic resonance (SRVM). Using the resonance of the second harmonic of operation frequency, the proposed SRVM overcomes the threshold voltage of diode with the induced voltage of the LC tank and achieves high PCE in the case of low coupling coefficient. When $k$ is 0.01~0.05, the maximum PCE of SRVM is 77.5%, which is more than 51 % higher than CVM.

A location-based phase-controlled array antennas system to improve power transfer effciecny (PTE) of RF power transfer(RFPT) system is presented. The proposed system consists of multiple antennas with each phase control device for transmitter (TX) and receiver (RX) respectively. For the multiple TX antennas, the phase of each antenna is determined to adjust the direction of main beam to the location of RX antenna. For the multiple RX antennas, the phase of each antenna is determined to eliminate delayed potential occurred by different positions of each RX antenna in array. A method of theoretically extracting the phase offset values of TX and RX for given relative positions of the TX and RX antennas is provided. A 5.8 GHz phase-controlled RFPT system with 4x4 TX antennas and 2x2 RX antennas is implemented, and it is verified that the proposed system improves the PTE up to 2.7 times than conventional method.

An electrodeless plasma bulb is one of promising lighting source due to its high efficacy, long life time, and sun-like light spectrum. Recently, a plasma lighting system (PLS) using a radio frequency (RF) solid-state power amplifier (SSPA) as a power source of the plasma bulb is widely used instead of the conventionally used magnetron. The SSPA is easy to control an RF signal of the system, and therefore has benefit in dimming control. One of the simple dimming scheme is to control magnitude of continuous wave (CW) signal of the PLS. However, the efficiency of the SSPA degrades due to thermal problem for the CW signal. In addition, a power back-off for the dimming decreases the efficiencies of the SSPA and the PLS. To overcome this problem, a pulsed RF signal is used for the dimming of the PLS. A combination of switch-mode RF SSPA and pulsed RF signal can improve the efficacy of the PLS. In this paper, we propose an efficient dimming scheme by modifying the pulsed RF signal. In order to achieve better efficiency and linearity performances, the proposed RF pulsed signal has a slope in time-domain unlike the conventional pulsed RF signal that have rectangular shape. A spectral regrowth of the modified pulsed RF signal can be reduced by changing slope rate. In result, the adjacent channel leakage power ratio of the proposed method is less than that of the conventional pulsed RF signal. A PLS using the proposed dimming scheme shows better efficacy because it reduces return loss in the adjacent channel. A 2.47 GHz PLS with a 300 W gallium-nitride (GaN) SSPA is implemented, and it is used to verify the proposed method. The PLS using the proposed method shows better performance compared with those using the CW signal or the conventional pulsed RF signal.

This paper presents low power frequency shift keying (FSK) transmitter using all digital PLL (ADPLL) for smart utility network (SUN). In order to operate at low-power and to integrate a small die area, the ADPLL is adopted in transmitter. The phase noise of the ADPLL is improved by using a fine resolution time to digital converter (TDC) and digitally controlled oscillator (DCO). The FSK transmitter is implemented in 0.18㎛ 1-poly 6-metal CMOS technology. The die area of the transmitter including ADPLL is 3.5 ㎟. The power consumption of the ADPLL is 12.43 ㎽. And, the power consumptions of the transmitter are 35.36 ㎽ and 65.57 ㎽ when the output power levels are -1.6 ㏈m and +12 ㏈m, respectively. Both of them are supplied by 1.8 V voltage source. The frequency resolution of the TDC is 2.7 ㎰. The effective DCO frequency resolution with the differential MOS varactor and sigma-delta modulator is 2.5 ㎐. The phase noise of the ADPLL output at 7.8㎓ is -121.17 ㏈c/㎐ with a 1㎒ offset.

This paper proposes a networked smart LED lighting system which targets building lightings. Lighting network is proposed with the concept of multi-hop ad hoc network, using Bluetooth beacon communication. With this system, building administrator can control numerous lightings easily and visitors can get visual information from the lightings with their smart devices. These applications are suggested and demonstrated.

This paper suggests an outphasing scheme to reduce adjacent channel spectral regrowth triggered by the gain and phase mismatch between two signal paths in linear amplification with nonlinear component (LINC) systems. The error vector magnitude and power spectral density of the output signal considering path mismatch are described analytically using path mismatch factor. An outphasing scheme is proposed to reduce the spectral regrowth. The proposed outphasing scheme reshapes the phases of the separated signals in LINC systems to reduce the changes of the phases. Its performance is verified by performing simulations with multi-tone signals. The result shows that the scheme can reduce the spectral regrowth of the multi-tone signals significantly compared to the conventional outphasing scheme for LINC systems with path imbalance.

In this paper, Current-Mode Class-D(CMCD) RF Power Amplifier(PA) is designed and implemented at 900 MHz. Conventional CMCD PA has output parallel resonator to reconstruct a fundamental frequency component of the output signal. However the resonator can be removed by connecting inverse class-F PAs because even-harmonic components can be removed by CMCD PA`s push-pull structure. Using load-pull, inverse class-F PA with GaN transistors is designed, and CMCD PA with the inverse class-F PA is implemented. The CMCD PA has 64.5 % drain efficiency, 34.2 dBm output power. Comparing with the drain efficiency of a CMCD PA with parallel resonator, the CMCD with the inverse class-F technology has 13.6 % improved drain efficiency.

In this paper, we suggest a scheme to develop an efficient discrete nonlinear model based on polynomial structure for a RF power amplifier(PA). We describe a procedure to extract a discrete nonlinear model such as Taylor series or memory polynomial by sampling the input and output signal of RF PA. The performance of the model is analyzed varying the model parameters such as sample rate, nonlinear order, and memory depth. The results show that the relative error of the model is converged if the parameters are larger than specific values. We suggest an efficient modeling scheme considering complexity of the discrete model depending on the values of the model parameters. Modeling efficiency index(MEI) is defined, and it is used to extract optimum values for the model parameters. The suggested scheme is applied to discrete modeling of various RF PAs with various input signals such as WCDMA, WiBro, etc. The suggested scheme can be applied to the efficient design of digital predistorter for the wideband transmitter.

In this paper, we analyse the effect of the path imbalances(gain and phase mismatches) in LINC(LInear amplification with Nonlinear Component) system, and propose a simple scheme using LUTs(Look Up Table) to compensate the path imbalances. The EVM(Error Vector Magnitude) and ACPR(Adjacent Channel Power Ratio) of the LINC system are degraded significantly by the path imbalances because it adopts an outphasing technique. The EVM and ACPR are theoretically extracted for two variables(gain and phase mismatch factors) and 2-D LUTs for those are generated based on the analysis. The efficient and simple compensation scheme for the path imbalances is proposed using the 2-D LUTs. A LINC system with the suggested compensation scheme is implemented, and the proposed method is verified with an experiment. A 16-QAM signal with 1.5 MHz bandwidth is used. Before the compensation, the path gain ratio was 95 % and phase error was . The proposed scheme adjusts those values with 99 % and , and improves ACPR about 18.1 dB.

This paper discusses an efficient discrete model for nonlinear RF power amplifier (PA) with long-term memory effects and analyzes its error. The procedure of converting RF signals and systems into a discrete domain is explained for a discrete baseband memory polynomial model. Unlike a previous simple memory polynomial model, the proposed discrete model has two different sampling frequencies: one for nonlinear system with long-term memory effects and one for input signal. A method to choose an optimal sampling frequency for the system and a discrete memory depth is proposed to minimize the sensitivity of the system for perturbation of the measured data. A two-dimensional sensitivity function which is a product of relative residual and matrix condition number is defined for least square problem of the proposed model. Examples with a wideband WiBro 3FA signal and a WCDMA 4FA signal for nonlinear transmitters are presented to describe the overall procedure and effectiveness of the proposed scheme.

In this paper, a nonlinear relationship between an input complex envelope and an output complex envelope of m-th harmonic zone is theoretically analyzed, and AM/ and AM/ are defined. A scheme to extract these characteristics from measured in-phase and quadrature-phase data is suggested. The proposed analysis is verified with a fundamental-fundamental and fundamental-third harmonic measurements for a InGaP power amplifier(PA). Based on the harmonic-band nonlinear analysis and extraction scheme, a new technique to send a signal in m-th harmonic band with a harmonic signal Linearization Digital Predistortion(DPD) scheme is presented. A numerical analysis and a Look-Up Table(LUT) based DPD algorithms to linearize output signal on m-th harmonic zone are developed. For a 16- and a 64-QAM input signals, a DPD for third harmonic signal linearization is implemented, and output spectrum and signal constellation are measured. The wholly distorted signals are linearized, and thus the measured Error Vector Magnitudes (EVM) are 6.4 % and 6.5 % respectively. The results show that a proposed scheme linearizes a nonlinearly distorted harmonic band signals. The proposed nonlinear analysis and predistortion scheme can be applied to multiband transmitter in next generation software defined radio(SDR)/cognitive radio(CR) wireless system.

This paper suggests an extended memory polynomial model that improves accuracy in modeling memory effects of RF power amplifiers(PAs), and verifies effectiveness of the suggested method. The extended memory polynomial model includes cross-terms that are products of input terms that have different delay values to improve the limited accuracy of basic memory polynomial model that includes the diagonal terms of Volterra kernels. The complexity of the memoryless model, memory polynomial model, and the suggested model are compared. The extended memory polynomial model is represented with a matrix equation, and the Volterra kernels are extracted using least square method. In addition, the structure of digital predistorter and digital signal processing(DSP) algorithm based on the suggested model and indirect learning method are proposed to implement a digital predistortion linearization. To verify the suggested model, the predicted output of the model is compared with the measured output for a 10W GaN HEMT RF PA and 30 W LDMOS RF PA using 2.3 GHz WiBro input signal, and adjacent-channel power ratio(ACPR) performance with the proposed digital predistortion is measured. The proposed model increases model accuracy for the PAs, and improves the linearization performance by reducing ACPR.

This paper proposes a new behavioral model to treat memory effects in nonlinear power amplifiers (PAs). Phenomena such as asymmetries in lower and upper intermodulation terms, and variation of AM/AM and AM/PM, depending on signal history, are often observed in high-power PAs. To treat these phenomena, this paper presents a model based on the previously developed memory polynomial model. The contribution made in this paper is to augment the memory polynomial model to include a sparse delay tap structure that reduces the parameter space required for accurate model identification. A figure-of-merit, called the memory effect ratio, is defined to quantify the relative level of distortion due to memory effects, as compared to the memoryless portion. Another figure-of-merit is defined as the memory effect modeling ratio, which quantifies the degree to which the PA memory effects have been accounted for in the model. This new technique is validated using a variety of RF PAs, including an 880-MHz and a 2.1-GHz high-power laterally diffused metal-oxide semiconductor PA and various signals such as two-tone, eight-tone, and IS-95B signals.

This paper proposes a system-level behavioral model for RF power amplifiers (PAs), which exhibit memory effects, that is based on the parallel Wiener system. The model extraction is performed using two-tone intermodulation distortion (IMD) measurements with different tone frequency spacings and power levels. It is found that by using such a model, more accurate adjacent-channel power-ratio levels may be predicted for high PAS close to the carrier frequency. This is validated using IS-95B CDMA signals on a low-power (0.5 W) class-AB PA, and on a high-power (45 W) class-B PA. The model also provides a means to quantify memory effects in terms of a figure-of-merit that calculates the relative contribution to the IMD of the memoryless and memory portion of the PA nonlinearity. This figure-of-merit is useful in providing an estimate of the amount of correction that a memoryless predistortion system may have on PAS that exhibit memory effects.