A design of the double-element E-plane quasi-Yagi–Uda antenna is proposed offering two different radiation patterns and reconfigurable bandpass-to-bandstop frequency-tunable responses. The double-element antenna covers a wide frequency range that is exploited for the realization of the tunable operation modes. This is achieved by the integration of a pair of bandpass-to-bandstop filters, each of which can be reconfigured using two varactor diodes and one p-i-n diode. The p-i-n diode serves the function of switching between bandpass and bandstop states, and the varactors facilitate the frequency tunability for both states of operation. The bandpass filter provides a continuous frequency tuning function with a minimum rolloff rate of 57 dB/GHz and out-of-band transmission coefficient −1 dB. Importantly, the reconfigurable filtering functionality of the two-element antenna is preserved when fed by a wideband hybrid coupler to produce both the sum and difference radiation patterns. To obtain a high beam symmetry, the antenna elements are fed by the difference ( $\Delta $ ) signal to produce the directive radiation pattern and they are fed by the sum ( $\Sigma $ ) port to produce the null in the main radiation direction. The experimental results validate this concept with a measured tunability of 50.0% for the bandpass state and 50.4% for the bandstop state.

Tunable Bandpass-to-Bandstop Quasi-Yagi–Uda Antenna With Sum and Difference Radiation Patterns

This paper presents a novel method to evaluate radiation energy and mutual coupling in multimode antennas. Based on the theory of characteristics mode, how much each mode occupies the radiation and the mutual coupling from each feeding port is calculated with the modal energy occupied coefficients. Furthermore, the linear transformation of feeding network in multimode antenna system has been adopted to complete the modal-based method. Then, this method is utilized to analyze and decrease the mutual coupling between feeding ports. Hence, a hexagonal wideband antenna is proposed with its evolution process and measured to validate the proposed method. The presented hexagonal antenna is a four-port multimode antenna consisting a planar hexagonal plate, vertical tapered baluns, and feeding network at the ground plane. The whole antenna works in 3–6 GHz and all its four ports are well matched with high port-to-port isolation.

/pdf/radiation-energy-and-mutual-coupling-evaluation-for-zz079sjg51.pdf

Radiation Energy and Mutual Coupling Evaluation for Multimode MIMO Antenna Based on the Theory of Characteristic Mode

This communication proposes a simple, low-cost multimode patch antenna combining good multi-in multi-out (MIMO) performance with precise angle of arrival (AoA) estimation. The AoA is based on the monopulse antenna concept; however, unlike in radar applications, the necessity for complex circuitry is replaced by the intrinsic properties of even and odd resonant patch modes. This capability is advantageous for future “Internet of Things” antennas, embedded into low-cost and size-constrained devices. The envelope correlation coefficient, measured in an anechoic chamber, is below 1.5%, ensuring good MIMO performance. An exemplary addition to localization algorithm exploiting antenna properties is demonstrated.

/pdf/low-cost-multimode-patch-antenna-for-dual-mimo-and-enhanced-18hebrr9ek.pdf

Low-Cost Multimode Patch Antenna for Dual MIMO and Enhanced Localization Use

This paper explains the design of a metasurface that tilts and focuses the broadside beam of an ordinary antenna to an offset angle. The design is based on the theory of near-field phase transformation, which has been demonstrated in our previous publications. In the final design, the metasurface is simply stacked above the base antenna within its near-field region - for the purpose of demonstration the base antenna is a classical resonant-cavity antenna (RCA). The metasurface transforms the arbitrary phase distribution of the field, radiated by the RCA, at its input into a linearly increasing phase at its output, thus tilting and focusing the RCA beam. The metasurface is made of spatially distributed printed cells for locally introducing a specific phase shift. With the metasurface, the RCA beam points at a 20° elevation angle and is 8 dB more directive with significantly reduced 3dB beamwidth.

A Metasurface to Focus Antenna Beam at Offset Angle

A compact planar quasi-Yagi antenna with a wideband microstrip-to-slotline transition and a modified bow-tie driver is designed with an enhanced bandwidth for precise indoor positioning applications. A compact interdigital capacitor loaded loop resonator with a high quality factor is placed inside the ring resonator at the end of the antenna's slot to realise band-notched characteristics over a frequency range of 5.1-6.3 GHz, thus avoiding interference from wireless local area networks (WLANs) and dedicated short-range communications (DSRCs). Measured results show that the proposed antenna obtains a relative impedance bandwidth, determined by the voltage standing wave ratio <;2, higher than 122.6% (3.0-12.5 GHz) and a gain of 4.9-7.8 dBi outside of the stop band.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2017.0982

Compact planar quasi-Yagi antenna with band-notched characteristic for WLAN and DSRC for ultra-wideband applications

Aiming to realise an end-on-fire antenna with band rejection for ultra-wideband (UWB) system, a planar quasi-Yagi antenna with dual-dipole structure is proposed. The antenna comprises of a coupling transition structure, two stripes and a dual-dipole connected by a coplanar stripline. The compact arrangement of the dual-dipole generates reverse currents at some specific frequency points on their edges, giving rise to phase offsets in far field. This mechanism is used to design band rejection. Simulated and measured results show that the proposed antenna has a bandwidth from 3.08 to 11.1 GHz, which covers the whole UWB band. Meanwhile, the antenna achieves a band rejection from 5.12 to 6.08 GHz, which avoids wireless local area network interference. In pass-band, the antenna achieves a moderate gain, from 4.6 to 7.1 dBi.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-map.2016.0160

Planar quasi-Yagi antenna with band rejection based on dual dipole structure for UWB

In this paper, a four port disk shaped compact multiple input multiple output (MIMO) patch antenna for vehicular application is proposed and fabricated. The structure is composed of a circle patch with cross slot combined to an annular ring patch. The structure is analyzed by using Theory of Characteristic Modes (TCM). The inner and outer part of the antenna operated at its TM11 and TM21 modes respectively. As a result, four different radiation patterns are achieved. The antenna exhibits a mutual coupling between the four input ports less than −16dB in simulation and −18dB in measurement in the frequency band. Both simulated and experimental results have been presented and discussed.

http://ieeexplore.ieee.org/iel7/7499994/7504672/07504999.pdf

Four port compact multimode patch antenna system for vehicular application

This paper presents a planar printed quasi-Yagi antenna. The proposed antenna consists of a microstrip line slotline transition structure, a driver dipole and two parasitic stripes. The driver dipole is connected to the slotline through coplanar stripline (CPS) which is designed by using a pair of exponential curves and a circular groove end, just the Vivaldi antenna structure, so as to achieve a wide bandwidth. The ground plane is modified by symmetrically adding two extended stubs and cutting two blocks to adjust the matching with the dipoles. Experimental and simulated results show that the proposed quasi-Yagi antenna has a wide bandwidth and good unidirectional radiation characteristics. Compared with conventional printed quasi-Yagi antennas, the bandwidth is wider, from 2.9GHz to 10.1 GHz with a ratio of about 3.48∶ 1, and it's front-to-back ratio greater than 10 dB. The antenna achieved a moderate gain, which is maintained from 4 dBi to 6.2dBi, and efficiency is mainly located at 90%, the minimum is more than 71%.

Broadband planar printed quasi-Yagi based on Vivaldi structure

In this paper, a beam-tilted array used as the reader antenna of ultra-wideband (UWB) location systems is proposed. Bow-tie antenna is adopted as element in the array to achieve a wideband performance. Feeding structure of coaxial line is employed to realize beam tilt angle. Good simulation and measurement results are presented. The antenna achieves a wide impedance bandwidth of 36.8% (3.1∼4.5GHz). A stable gain of more than 4.5dBi and beam tilt angle of 30° is realized within the whole impedance bandwidth.

Design of beam-tilted array antenna for UWB location system

Aiming to realize an end-on-fire antenna with band rejection for UWB system, this paper proposes a planar quasi Yagi antenna with dual-dipole structure. The antenna uses a dual-dipole to generate reverse surface currents at some specific frequency points. This mechanism is used to design band rejection. Simulated and measured results show that the bandwidth of the proposed antenna is from 3.37 GHz to 11.28 GHz. Meanwhile, the antenna achieves a band rejection from 5.15 GHz to 6.12 GHz, which avoids WLAN interference. In passband, the antenna achieves a moderate gain, from 4.3 dBi to 7.9 dBi.

Jiafeng Qu

Papers

Planar quasi-Yagi antenna with band rejection based on dual dipole structure for UWB

Four port compact multimode patch antenna system for vehicular application

Broadband planar printed quasi-Yagi based on Vivaldi structure

Design of beam-tilted array antenna for UWB location system

Broadband planar quasi-Yagi antenna with band rejection