RF energy is widely available in urban areas and thus presents a promising ambient energy harvesting source. In this paper, a CMOS harvester circuit is modeled and analyzed in detail at low environmental power levels. Based on the circuit analysis, a design procedure is given for a narrowband energy harvester. The antenna and harvester co-design methodology is discussed to improve RF to DC energy conversion efficiency. We demonstrate that it is difficult to harvest RF energy over a wide frequency band if the ambient RF energy sources are weak, owing to the voltage requirements. Since most ambient RF energy lies in a few narrow bands, a dual/multi-band energy harvester architecture should be able to harvest much of the available RF energy. A dual-band CMOS energy harvester is designed and fabricated using an IBM 0.13 μm process. The simulated and measured results demonstrate a dual-band energy harvester that obtains over 9% efficiency for two different bands (around 900 MHz and around 1900 MHz) at an input power as low as -19.3 dBm. The DC output voltage of this harvester is over 1 V, which can be used to recharge the battery to form an inexhaustibly powered communication system.

An Antenna Co-Design Dual Band RF Energy Harvester

This paper presents lumped dual-frequency impedance transformers for frequency-dependent complex loads. According to difierent dual-frequency allocations of a complex load in Smith chart, three types of impedance matching networks are presented respectively. Several kinds of lumped circuit blocks are used as basic elements for constructing these transformers with design formula deduced. Various examples are given for describing the design procedures. Good features such as big frequency ratio and big matching bandwidths are demonstrated. These lumped dual-frequency impedance transformers have advantage of much compacter dimensions compared to distributive solutions.

Lumped dual-frequency impedance trans- formers for frequency-dependent complex loads

In order to incorporate different communication standards into a single device, a compact quad-band slot antenna is proposed in this paper. The proposed antenna is composed of a dielectric substrate, T-shaped microstrip patch with a circle slot and an inverted L-slot, and a comb-shaped ground on the back of the substrate. By adopting these structures, it can produce four different bands, while maintaining a small size and a simple structure. Furthermore, a prototype of the quad-band antenna is designed and fabricated. The simulated and measured results show that the proposed antenna can operate over the 1.79–2.63 GHz, 3.46–3.97 GHz, 4.92–5.85 GHz, and 7.87–8.40 GHz, which can cover entire PCS (Personal Communications Service, 1.85–1.99 GHz), UMTS (Universal Mobile Telecommunications System, 1.92–2.17 GHz), WCDMA (wideband code-division multiple access, 2.1 GHz), Bluetooth (2.4–2.48 GHz), WiBro (Wireless Broad band access service, 2.3–3.39 GHz), WLAN (Wireless Local Area Networks, 2.4/5.2/5.8 GHz), WiMAX (Worldwide Interoperability for Microwave Access, 2.5/3.5/5.5 GHz), and X-band SATcom applications (7.9~8.4 GHz). The proposed antenna is particularly attractive for mobile devices integrating multiple communication systems.

/pdf/design-of-a-compact-quad-band-slot-antenna-for-integrated-19nx9yrfia.pdf

Design of a Compact Quad-Band Slot Antenna for Integrated Mobile Devices

In this study, the authors propose a cyclic prefix (CP) based imperfect reconstruction (IPR) filter bank multicarrier (FBMC) system in the uplink of multiuser networks, known as filter bank multiple access (FBMA). The prototype filter in the system is a common low-pass filter without any perfect reconstruction (PR) or nearly perfect reconstruction (NPR) constraint. CP appended input signal format is applied to avoid inter-symbol interference and facilitate the equalisation task. The received signal is jointly processed by multi-subband equalisation. Besides, the input data symbols can be complex-valued due to IPR design. Some properties and achievable data rate of the proposed system are discussed. Simulations illustrate that the proposed system with uniformly/non-uniformly designed filter bank has a similar achievable data rate to orthogonal frequency division multiple access (OFDMA). Bit error rate performance of the proposed system is better than OFDMA and an error floor always exists when applying conventional PR FBMC to multi-user networks. In addition, OFDMA is more sensitive to carrier frequency offset than FBMA because of full synchronisation requirement. Therefore, it suggests that the proposed CP based IPR FBMA system works well without PR/NPR conditions and more extensive development is feasible for the filter banks in the foreseeable future.

Properties and achievable data rate of a cyclic prefix based imperfect reconstruction filter bank multiple access system

A novel CPW-fed planar printed monopole antenna with broadband circular polarization (CP) characteristic is presented. The proposed antenna consists of a copper coin-shaped patch (CCSP) and an asymmetrical ground plane. To achieve a broadband CP wave, a vertical stub is added to the CCSP to produce orthogonal surface currents for right-hand circular polarization (RHCP). The design of the CCSP greatly increases the impedance bandwidth (IBW) of 89.2% which can cover the whole CP bandwidth of 71% completely. The measured results show that the proposed antenna has not only a broad 3-dB AR bandwidth (ARBW) of 71% (3900 MHz, 3.1–7 GHz) with respect to the CP center frequency 5.8 GHz, but also a wide 10-dB return loss bandwidth of 89.2% (5040 MHz, 2.16–7.2 GHz) centered at 5.65 GHz.

/pdf/a-novel-cpw-fed-planar-monopole-antenna-with-broadband-3yzx6n2vwf.pdf

A novel cpw-fed planar monopole antenna with broadband circularly polarization

In this work, a new coplanar-waveguide (CPW)-fed monopole antenna with dual-band operation is proposed. The antenna is composed of a meandered monopole, an extended conductor line, and asymmetrical ground planes. Tuning geometrical structure of the ground plane of the CPW feeding structure excites additional resonant frequency bands, and thus enhances the impedance bandwidth. The measured impedance bandwidths, which is defined by −6 dB reflection coefficient, are 186 MHz (863 – 1049 MHz, 19.4%) at the lower resonant mode and 1320 MHz (1490 – 2810 MHz, 61.3%) at the upper mode. It can be observed that the impedance bandwidth of the proposed antenna covers the operated bandwidths of the commercial wireless communication systems, such as GSM 900, DCS, IMT-2000, UMTS, WLAN, LTE 2300, and LTE 2500.

A CPW-fed meandered-shaped monopole antenna with asymmetrical ground planes

A coplanar-waveguide (CPW)-fed monopole antenna for applications of the multi-system integration has been presented in this study. The enhancement of impedance bandwidth and circular polarization in the microstrip rectangular monopole antenna using following techniques: using asymmetrical CPW feeding structure and adding three grounded sleeve strips. By tuning the width of one side of the CPW ground plane, increase of impedance bandwidth and excitation of circular polarization at 1.57 GHz are achieved. Three parasitic inverted-L conducted strips are connected to the ground plane to further extend the impedance bandwidth. The measured impedance bandwidth of a S 11 < −6 dB ranges from 0.65 to 2.85 GHz and the measured 3-dB axial-ratio bandwidth is about 150 MHz. The proposed antenna covers most of commercial wireless communication systems, such as GSM, GPS, DCS, PCS, IMT-2000, WLAN, and LTE.

A wideband CPW-fed monopole antenna with linear and circular polarizations

A design procedure for a dual-band CPW-fed linearly and circularly polarized (CP) antenna based on the L-shaped slot antenna is presented in this paper. The slot antenna and the feeding structure are fabricated on the same plane of the substrate so that circuit processes and position alignment can be simplifled. By shortening the length of one arm of the L-slot, an additional mode with two orthogonal electrical flelds with a phase difierence of 90 degree is excited, so that the circularly polarized wave can also be excited. The enhancement of the resonant bandwidth is achieved by utilizing a stub-protruded feedline, adding one flnger slit at the other arm slot, and tuning the dimension of the ground plane. A bandwidth of 22.0% (2.23{2.78GHz) is achieved with an axial ratio < 3dB for the optimized case.

/pdf/a-dual-band-cpw-fed-l-slot-antenna-with-both-linear-and-2nc42op05l.pdf

A dual-band cpw-fed l-slot antenna with both linear and circular polarizations

New techniques to increase the front-to-back ratio of the monopole slot antenna for operation from 1.67 GHz to 4.25 GHz are presented, covering the required frequency bands of the wireless communications systems, such as DCS, PCS, IM-2000, WLAN, and WiMAX. Compared with conventional unidirectional radiation antennas, the proposed antenna demonstrates the wideband unidirectional radiation characteristics and the small size.

A broad open slot antenna with uni-directional radiation patterns

The design procedure of the microstrip-fed stepped-impedance (SI) slot antenna has been derived by utilizing the transmission-line and lumped-element circuit topologies. The resonant analysis and modeling of the antenna are also included. This study does not only analyze the SI-slot antenna, but also systematically summarizes its frequency response characteristics, including the resonance condition and spurious response. The design formulas with respect to the impedance ratio of the SI slot antenna are analytically derived. Note that the resonant modes of the SI-slot antenna are predicted without utilizing expensive EM simulation software.

http://ap-s.ei.tuat.ac.jp/isapx/2014/pdf/FR2A_05.pdf

Chien-Jen Wang

Papers

A CPW-fed meandered-shaped monopole antenna with asymmetrical ground planes

A wideband CPW-fed monopole antenna with linear and circular polarizations

A dual-band cpw-fed l-slot antenna with both linear and circular polarizations

A broad open slot antenna with uni-directional radiation patterns

Analysis of stepped-impedance slot antenna