A novel coplanar waveguide-fed rectenna with high efficiency is proposed and implemented in this paper for 2.45-GHz Bluetooth/ wireless local area network applications. The antenna has compact dimensions of 18 mm $\times \,\, 30$ mm, which is simulated and manufactured using a low-cost FR4 substrate with a thickness of 1.6 mm. A tuning stub technique with rectangular slots is used for better impedance matching and enhancing the impedance bandwidth of the antenna with a peak gain of 5.6 dB. The proposed novel antenna for RF energy harvesting applications exhibits dipolelike radiation pattern in $H$ -plane and omnidirectional pattern in $E$ -plane with improved radiation efficiency. Single-stage Cockcroft–Walton rectifier with L-shaped impedance-matching network is designed in advance design system and fabricated on FR4 substrate. The dc output of the rectenna is measured as 3.24 V with a load resistance of 5 $\text{k}\Omega $ . A simulated peak conversion efficiency of 75.5% is attained, whereas the measured one is observed to be 68% with an input signal power of 5 dBm at 2.45 GHz.

A Compact Rectenna System With High Conversion Efficiency for Wireless Energy Harvesting

A realization method of wide-stopband substrate-integrated waveguide (SIW) diplexers and dual-band bandpass filters (BPFs) with widely realizable frequency ratios is presented using modified intrinsic modes suppression technique. Design procedures of dual-band and wide-stopband characteristics for different frequency ratios are systematically summarized by sufficiently using the limited design degrees of freedom. The mixed dual- and single-mode cavities and the offset external coupling slots could help to flexibly control the dual-band frequencies and bandwidths. Meanwhile, the internal coupling windows could produce predictable wide-stopband performance when properly arranged at the positions of weakest electric fields of specific unwanted spurious modes determined by the frequency distributions for the required frequency ratio. Two SIW diplexers and an SIW dual-band BPF with frequency ratios of 1.225, 1.5, and 1.425 are synthesized and designed for demonstration, extending the stopband up to $1.79{f} _{0}$ with better than 24 dB rejection level, $2.05{f} _{0}$ and $2.34{f} _{0}$ with better than 20 dB rejection level, respectively.

Compact SIW Diplexers and Dual-Band Bandpass Filter With Wide-Stopband Performances

This brief presents a low loss reflection-type phase shifter (RTPS) using a single varactor diode as the load. A parallel combination of an open-circuited stub and a varactor loaded stub are used at the load terminal. This arrangement greatly improves the response of the phase shifter. A transmission line based analysis shows real part of the load plays an important role on both phase variation and insertion loss. Based on the analysis, design guidelines are provided for controlling maximum insertion loss of the phase shifter. A prototype phase shifter is fabricated at 10 GHz. Measurement results of the RTPS show a relative phase variation of 190° with a maximum insertion loss of 2 dB when varactor capacitance is varied over 0.1 pF–0.2 pF. Moreover, the return loss is always better than 20 dB over the entire tuning range of the RTPS.

Electronically Tunable Reflection Type Phase Shifters

This letter presents a design for a wideband reflection-type tunable phase shifter (RTPS) with a low in-band phase deviation error. The proposed RTPS consists of a 3-dB hybrid where a through port and a coupled port are terminated with coupled lines, varactor diodes, and a capacitor. The measured capacitance of the varactor diodes was used in the analysis to take into account the in-band phase deviation error caused by the parasitics of the varactor diode. The analysis shows that the desired phase shifting range (PSR) and a low in-band phase deviation error can be obtained by properly selecting the characteristic impedance and coupling coefficient of the coupled line and load capacitance. The experimental results show that the fabricated RTPS provides a PSR of 146.93° at 2.5 GHz and an in-band phase deviation error of ±5.79° within 500 MHz. Moreover, the input–output return losses are higher than 15.76 dB, and the insertion loss is smaller than 1.29 dB within the operating frequency band.

Wideband Tunable Phase Shifter With Low In-Band Phase Deviation Using Coupled Line

A modified multi-spurious modes suppression technique is proposed to realize wide-stopband substrate-integrated waveguide (SIW) bandpass filters (BPFs), which is to set the external ports and internal coupling windows to the positions of weakest electric fields of specific spurious modes. To extend the stopband as wide as possible with the limited design degrees of freedom, different feeding and coupling positions are fully exploited to reject unwanted modes in specific cavities. By suppressing the out-of-band spurious peaks as much as possible and removing the first unsuppressed spurious resonance to the farthest position, the widest stopband can be achieved intrinsically. A second- and a third-order SIW BPFs are synthesized, designed, fabricated, and tested as demonstrations, realizing the stopbands of $2.51{f} _{0}$ and $3.85{f} _{0}$ with the rejection level better than 25 dB and 20 dB, respectively.

Wide-Stopband SIW Filters Using Modified Multi-Spurious Modes Suppression Technique

In this brief, a high-isolation and wide-stopband diplexer with controllable transmission zero (TZ) nearby the passband, is implemented using substrate integrated waveguide elements. The TZ is generated by the mixed electric and magnetic coupling scheme of $ {TE}_{ {101}}$ mode. It can be flexibly controlled by changing the length of rectangular apertures while keeping good wide-stopband performance unchanged. An ${X}$ -band diplexer with lower and upper channels centered at 9.5 GHz and 10.5 GHz was designed, fabricated, and measured to verify the proposed concept. Good agreement between simulation and measurement can be observed. The designed diplexer exhibits a high isolation level larger than 45 dB over the whole band and a wide stopband up to 20 GHz.

High-Isolation and Wide-Stopband SIW Diplexer Using Mixed Electric and Magnetic Coupling

Wide bandwidth, wide tunable phase range, and a compact circuit size are always desired for the tunable phase shifter utilized in the modern wireless communication system. However, the existing reflection-type phase shifter configurations cannot satisfy all these requirements simultaneously. To resolve these problems, the reflection load consisting of two tunable capacitors and a quarter wavelength transmission line is utilized on a vertically installed planar structure to implement a new reflection-type phase shifter. For demonstration, a reflection-type phase shifter is designed, fabricated, and measured. A wide bandwidth of 66.7% defined by 10-dB return loss had been achieved. Over the same band, a wide phase shift range up to 407° can be observed. Meanwhile, the fabricated circuit occupies a compact circuit size of ${0.26\lambda _{g} *0.37\lambda _{g}}$ .

A Wideband Tunable Reflection-Type Phase Shifter With Wide Relative Phase Shift

In this paper, a balanced bandpass filter (BPF), a balanced-to-balanced filtering power divider (FPD), and a balun filter are implemented using the isosceles right triangular patch element. Two isosceles right triangular patch elements are coupled through an open stub for a triple-mode passband response under differential-mode operation and wide common-mode suppression simultaneously. To further improve the selectivity, an open stub is loaded on each feed-line. Based on these elements, a balanced BPF with excellent performance can be implemented. As an extension, a balanced-to-balanced FPD and a balun BPF are implemented based on the structure of the filter. For validation of the proposed configurations, all the balanced BPF, FPD, and balun BPF have been fabricated and measured. All measured results are found to be in a reasonable agreement with the simulation results.

Design of Balanced Filtering Components Based on Isosceles Right-Angled Triangular Patch

To solve the problems of existing frequency tunable quadrature couplers with limited tuning range and narrow bandwidth, a frequency tunable 3-dB quadrature coupler with wide tuning range and wide bandwidth is proposed and is based on the vertically installed planar (VIP) structure. Varactor diodes are loaded between vertical patches to achieve frequency tuning. Due to the strong coupling characteristics of the VIP structure, broad bandwidth is maintained during the frequency tuning process. For validation, a frequency tunable coupler is designed, fabricated, and measured. The center frequency of the designed coupler can be varied from 1.3 GHz to 2.7 GHz covering a frequency range of 70%. For each operating mode, more than 40% bandwidth defined by 1 dB amplitude imbalance between output ports, 10 dB return loss and isolation, and phase variation of 5°, can be achieved.

A Frequency Tunable Quadrature Coupler With Wide Tuning Range of Center Frequency and Wide Operating Bandwidth

To support different standards simultaneously within a wireless communication system, research on dual-/multi-band components has been conducted extensively. However, the operating frequencies of existing works are usually fixed resulting in a low flexibility. To solve this problem, a highly reconfigurable coupler whose two operating frequencies can be controlled independently is proposed for the first time in this paper. Based on the analysis of a basic configuration, the conditions for realizing the desired independent frequency tuning can be obtained. To realize this unique property, varactors loaded coupled line sections are introduced on a conventional branch line coupler. Owing to the symmetrical structure of the proposed coupler, explicit theoretical analysis can be conducted. For demonstration, two reconfigurable couplers are designed, fabricated, and measured. The first coupler can provide frequency tunability from 3.4 to 4.2 GHz at the upper band with the lower band fixed at 2.4 GHz. The other one can not only provide a tunable frequency from 1.3 to 1.6 GHz at the lower band with the higher band fixed at 3.4 GHz, but also give a tunable higher band from 2.9 to 3.4 GHz with the lower band fixed at 1.55 GHz. The measured results agree well with the simulated results, validating the proposed design methodologies.

Yun Liang Long

Papers

High-Isolation and Wide-Stopband SIW Diplexer Using Mixed Electric and Magnetic Coupling

A Wideband Tunable Reflection-Type Phase Shifter With Wide Relative Phase Shift

Design of Balanced Filtering Components Based on Isosceles Right-Angled Triangular Patch

A Frequency Tunable Quadrature Coupler With Wide Tuning Range of Center Frequency and Wide Operating Bandwidth

Highly Reconfigurable Dual-Band Coupler With Independently Tunable Operating Frequencies