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The authors have proposed a dual‐band reconfigurable Fabry–Pérot (F‐P) cavity antenna with high gain and meanwhile small radar cross‐sections (RCSs) in wideband. Different from the traditional F‐P antennas, they used a dynamic metasurface reflective plane (DMRP) as the lower superstrate to realise reconfigurable functions and a digital coding metasurface as the upper superstrate to achieve wideband RCS reduction. To investigate the dual‐band reconfigurability, a wideband rectangular waveguide is used to feed the F‐P antenna. By varying the bias voltage applied to varactors embedded in the elements of DMRP, the reflection phase of DMRP is changed and the two operating frequencies can be tuned electronically. To realise RCS reduction, they adopted a meticulous arrangement of the coding elements on partially reflecting surface. The designed metasurface‐assisted F‐P antenna has good radiation performance with high gain, high aperture efficiency, and high radiation efficiency. In the experiments, a prototype was fabricated via printed circuit board technology, and measured results agree well with numerical simulations. The measured peak gain reaches 17.52 dBi and the maximum aperture efficiency is 56.97%. The two reconfigurable bandwidths cover 5.10–5.40 and 6.60–6.93 GHz, respectively; and 7 dB RCS reduction is achieved from 9.40 to 13.7 GHz for arbitrary polarisation [ABSTRACT FROM AUTHOR]

A polarisation reconfigurable fractal slot antenna with dual‐band performance is proposed in this study. The antenna consists of a Minkowski Island fractal inspired slot in the ground plane, which is excited by a microstrip line. The input match of the antenna is improved by placing two protruding horizontal stubs inside the two corners of the fractal slot. Four p‐i‐n diodes are placed within the grounded fractal structure to realise polarisation reconfigurability. Based on the switching states of the p‐i‐n didoes, the proposed antenna can produce right‐hand circular polarisation or left‐hand circular polarisation. A novel biasing network is used, which uses only two wires for polarisation switching. A prototype of the proposed antenna is fabricated and tested. When the antenna is configured to radiate circular polarisation, the measured reflection coefficient bandwidths (corresponding to |S11|≤−10 dB) for the two bands are 15.44 and 13.16% and the measured axial ratio bandwidths (corresponding to AR ≤3 dB) are 17.61 and 8.69%, respectively. [ABSTRACT FROM AUTHOR]

This study reports on a highly miniaturised polarisation selective surface (PSS) for dual-band Wi-Fi and WLAN applications. The proposed unit cell consists of two independently tuneable square loops. The outer loop is split with a gap of 0.2 mm to introduce polarisation selectivity and miniaturisation for lower-frequency band of 2.5 GHz. The inner square loop is inductively loaded with arms to suppress 5.45 GHz frequency band. These configurations have resulted in a unit element size of $\lambda _{\circ }/14$λ∘/14 at 2.5 GHz, which is not presented before to the best of the authors' knowledge. A wide rejection bandwidth ($-10\,{\rm dB}$−10dB) of more than 600 and 1180 MHz is obtained around 2.5 and 5.45 GHz, respectively. Furthermore, the proposed PSS exhibits an excellent polarisation selective characteristic by generating two stopbands at 2.5 and 5.45 GHz when illuminated by horizontal (TM) incident waves, whereas vertically (TE) polarised incident waves result in the generation of passbands for these two frequencies. Numerical validation through equivalent circuit modelling of the proposed PSS has also been carried out. A finite prototype containing $31 \times 33$31×33 elements is fabricated and tested. The measured results demonstrated that the PSS has excellent potential for applications that employ polarisation separators and wave generators. [ABSTRACT FROM AUTHOR]

A novel dual‐wideband dual‐polarised magnetoelectric (ME) dipole antenna for the fourth generation (4G)/fifth generation (5G) microcell base station is proposed. Using a pair of orthogonal ME dipoles and Γ‐shaped tapered cross feeding lines, the initial antenna achieves dual‐band and dual‐polarised. Then, four U‐shaped gaps, added in electric dipoles, effectively extend the lower impedance bandwidth. Finally, a circular parasitic patch with capacitive properties is innovatively loaded above the ME antenna, which obviously reduces the high‐resonant frequency from 5.5 to 4.9 GHz. Meanwhile, a box‐shaped reflector is employed to achieve stable gain and radiation patterns. As a result, the measured results show the good dual‐wideband performance of 52.4% (2.14–3.66 GHz) and 7.4% (4.68–5.04 GHz) with voltage standing wave ratio (VSWR) < 2, high isolation (>25 dB) and high gain (9.5 and 5.5 dBi, respectively). In addition, a stable radiation pattern with a half‐power beam width of 63.5°±6.8° and good cross‐polarisation discrimination (>20 dB) on the E‐plane is realised over these two bands. [ABSTRACT FROM AUTHOR]

A method to excite dual band for a microstrip antenna on a two-layer substrate by combining the proximity feed and the inset feed in a simple way is presented. Both linearly polarised and circularly polarised (CP) dual-band waves can be excited. The CP antenna consists of two stacked perturbed patches. If the lower patch were directly connected to the feed line, it is hard to form two bands. A single resonant frequency is found dependent on the size of the lower patch and is insensitive to the loading effect of the upper patch. The lower patch is inset coupled to the feed line. The authors found that two bands can easily be excited. To demonstrate the idea, a dual-band global positioning system antenna is designed and tested. The achieved impedance bandwidths are 60 MHz centred at 1215 and 65 MHz centred at 1563 MHz. The 3 dB axial-ratio bandwidths are 15 MHz centred at 1228 and 20 MHz centred at 1575 MHz.

This Letter demonstrates the design of a two‐element polarisation diversity antenna, applicable for modern small satellite application systems. The intended antenna mainly consists of two monopole radiators loaded with metasurface reflector as a ground plane. The dimensions of the radiator antenna are 40 × 22 × 1.6 mm3. The antenna measured results offers a wider S11 bandwidth of (2.23–2.91 GHz) and wider axial ratio bandwidth (ARBW) of (2.16–2.92 GHz) with a common S11 and ARBW of 26.45% is obtained. A maximum gain of 7.02 dBic and isolation better than 14.5 dB is observed along with the operating frequency range. The antenna provides an ARBW(< 3 dB) and gain (> 2.38 dBic) for theta = ± 45°, for all phi values along with the complete operating frequency range. Also, the antenna port‐1 provides left‐handed circular polarisation and port‐2 provides right‐handed circular polarisation radiation with directional radiation characteristics. [ABSTRACT FROM AUTHOR]

A square patch radiator supports both TM01 and TM10 modes with equal resonant frequencies. Feeding the patch in its diagonal can excite both modes with equal amplitudes and phases. By utilising this property, an effective technique is proposed to realise dual‐band dual‐polarised patch antenna. While the lower resonant frequency can be calculated using an existing analytical formula, an expression of the higher resonant frequency is still missing in the literature. To this end, an approximate expression of the higher resonant frequency is devised using the equivalent transmission line model in this work. It is a function of the distance between the shorting post and the feeding location. In order to validate the accuracy of the expression, three different antenna configurations are designed and manufactured. Good agreements between theoretical, simulated, and measured results are observed. [ABSTRACT FROM AUTHOR]

A novel single‐radiator card‐type tag is proposed which is constructed using a series Hilbert‐curve loop and matched stub for high frequency (HF)/ultra high frequency (UHF) dual‐band radio frequency identification (RFID) positioning applications. This is achieved by merging the series Hilbert‐curve for implementing the HF coil antenna, and square loop structure for implementing the UHF antenna to form a single RFID tag radiator. The RFID tag has directivity of 1.75 dBi at 25 MHz, 2.65 dBi at 785 MHz, 2.82 MHz at 835 MHz and 2.75 dBi at 925 MHz. The tag exhibits circular polarisation with −3 dB axial‐ratio bandwidth of 14, 480, 605 and 455 MHz at 25, 785, 835 and 925 MHz, respectively. The radiation characteristics of the RFID tag is quasi‐omnidirectional in its two orthogonal planes. Impedance matching circuits for the HF/UHF dual‐band RFID tag are designed for optimal power transfer with the microchip. The resulting dual‐band tag is highly compact in size and possesses good overall performance which makes it suitable for diverse applications. [ABSTRACT FROM AUTHOR]

This work explains the design and development of a low profile and compact single probe‐fed metamaterial (MTM)‐based circularly polarised (CP) antenna using the modified rectangular patch with two pairs of spiral strips and vias for 5.2/5.8 GHz WLAN applications. The intended CP antenna mainly consists of two pairs of radiators and each radiator is realised by using epsilon negative (ENG) transmission line (TL) to generate zeroth‐order resonance. CP characteristics are achieved by placing two radiators for x‐polarised wave are orthogonally aligned to the other two radiators for y‐polarised wave. The antenna radiating element offers a compact size of 0.24λ0 × 0.22λ0 with a low profile of 0.04λ0 at 5.5 GHz. To confirm the characteristics of the intended MTM CP antenna design, the designed antenna is fabricated and measured. Measurement results show that the antenna obtains −10 dB impedance bandwidth of 610 MHz (10.86%) which is 2.3 times larger than the standard microstrip patch antenna and axial ratio bandwidth of 140 MHz (2.54%) is obtained. [ABSTRACT FROM AUTHOR]

A novel capsule antenna with dual‐band performance and small occupation of inner capsule space is proposed. The antenna is designed by combining rigid Rogers substrate with flexible polyimide, which takes full utilisation of capsule inner surface and the system ground for implanted electronics. The antenna structure is based on two identical orthogonal strips, each connected with one conformal L‐strip. In addition, a shorting pin is introduced, bringing in a fundamental resonance at 1.4 GHz industrial, scientific and medical (ISM) band with linear polarisation. Besides, with the adoption of the shorting pin, two extra resonant modes are excited and split in higher band, generating two orthogonal electric fields with equal amplitude and π/2 phase difference; therefore, covering another ISM band at 2.45 GHz with circular polarisation property. Finally, the simulation results show a wide impedance bandwidth of 16.2% at 1.4 GHz ISM band (for |S11| <−10 dB), and a broad axial ratio (AR) bandwidth of 34.8% at 2.45 GHz ISM band (for |S11| < −10 dB and AR <3 dB), with dual‐band operation further validated by measurement result. [ABSTRACT FROM AUTHOR]

In this Letter, a mu‐negative metamaterial (MTM) filter‐based novel decoupling technique is presented for multiple input multiple output (MIMO) antennas. The design process has been described in a systematic manner, starting with the basic two port monopole antenna and then adding cancellation network and finally the proposed MIMO antenna by adding the matching network. Since the presented decoupling network is developed using MTM structure, good isolation between the antennas is achieved by maintaining compactness. The presented isolation technique can be used in different applications like in developing circularly polarized and multi‐band MIMO antennas. As an example, two port circularly polarised MIMO antenna design is also presented. The proposed designs have been fabricated and the simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

A zonal slot antenna cut onto a conducting cavity is combined with a dielectric resonator antenna (DRA) to form a circularly polarized (CP) dualband hybrid antenna. The zonal slot antenna and DRA are located on the side wall and top face of the cavity, which are responsible for the lower and upper bands, respectively. No external ground planes are used for the hybrid antenna and, thus, the structure is very compact. An L-probe is placed inside the cavity to feed the zonal slot directly and to excite the DRA indirectly through a cross coupling slot beneath the DRA. In this paper, two symmetrical cuts are cut onto the zonal slot for exciting CP fields, and a third cut is introduced to the zonal slot to fine-tune the axial ratio (AR). The DRA is excited by its underlaid cross slot with unequal lengths, giving two orthogonal degenerate modes that generate CP fields. The frequencies and field polarizations of the zonal slot and DRA can be designed independently, which greatly facilitates designs of the dualband CP antenna. The reflection coefficient, AR, radiation pattern, and radiation efficiency of dualband antennas were measured, and the measured results agree reasonably well with our simulated results obtained using Ansoft HFSS. [ABSTRACT FROM PUBLISHER]

A novel dual-frequency dual-linear-polarization printed antenna element benefiting from a single-feed single-layer structure is introduced in this paper. The Boolean particle swarm optimization algorithm in conjunction with the method of moments (MoM) is employed to optimize the geometry of the antenna after considering three objectives: cross polarization, return loss, and boresight direction in both bands. A fuzzy-logic based ordered weighted averaging operator allows us to efficiently implement the multi-objective optimization technique. Prototypes of the optimized designs have been fabricated and tested. The measured results show excellent performance with more than 15 dB of return loss and 10 dB of cross polarization in both frequency bands of operation, i.e., 12 and 14 GHz. A gain of 4.8 dBi has been measured for both frequency bands. [ABSTRACT FROM PUBLISHER]

A new technique for designing dual-band reconfigurable slot antennas is presented. Dual-frequency operation is achieved by loading a slot antenna with two lumped variable capacitors (varactors) placed in proper locations along the slot. Loading the slot antenna with lumped capacitors shifts down the resonant frequencies of the first and second resonances of the antenna. However, these frequency shifts depend not only on the values of the capacitors, but also on their locations along the slot antenna. Here, it is shown that by choosing the locations of the varactors appropriately, it is possible to obtain a dual-band antenna whose first and second resonant frequencies can be controlled individually. In other words, the frequency of either the first or the second band can be fixed, while the other one is electronically tuned. Using such a design, an electronically tunable dual-band antenna is designed and fabricated using two identical varactors having a capacitance range of 0.5-2.25 pF. The antenna is shown to have a frequency ratio (fR=f2/f1) ranging from 1.3 to 2.67. An important feature of this antenna is its consistent radiation pattern, polarization, and polarization purity at both bands and across its entire tunable frequency range. [ABSTRACT FROM PUBLISHER]

A new technique for designing dual-band reconfigurable slot antennas is introduced. The technique is based on loading a slot antenna with a lumped capacitor (or varactor) at a certain location along the slot. Given a fixed capacitor location along the slot, decreasing the capacitance results in increasing the first and second resonant frequencies of the slot antenna. However, the changes in the resonant frequencies are significantly different for the first and second resonances and, hence, a dual-band antenna with considerable frequency ratio tuning range can be obtained. Based on this technique, an electronically tunable dual-band antenna with a frequency ratio in the range of 1.2-1.65 is designed and fabricated using a single varactor with a capacitance range of 0.5-2.2 pF. The antenna has similar radiation patterns with low cross-polarization levels at both bands and across the entire tunable frequency range. [ABSTRACT FROM PUBLISHER]

We introduce a partly corrugated hard horn, consisting of a smooth-walled horn with an attached longitudinally corrugated outer section. This alleviates the problems with the manufacturing when the longitudinal corrugations extend into the throat of the horn. The transition between the inner smooth walled part and the outer corrugated part is abrupt. This is used and controlled to design better and shorter single-band horns than otherwise possible. Furthermore, it enables the design of dual-band horns with low cross-polarization and high gain, for multifunction use at Ka-band with transmit and receive frequencies in the same antenna. Measurements on a model of such a dual-band horn are presented and discussed. [ABSTRACT FROM PUBLISHER]

This Letter presents the development of a dual linearly polarised microstrip antenna for S‐ and C‐band with improved isolation and bandwidth. The antenna is dual linearly polarised at each of the bands. The S‐band patch is proximity coupled to two orthogonal feed lines, whereas the C‐band patches are aperture coupled to other two mutually orthogonal feed lines. The antenna results in an impedance bandwidth ≥ 3.65% with an isolation ≥ 26 dB at the S‐band ports. At the C‐band ports, it also displays an isolation ≥ 45 dB over the entire operating bandwidth of ≥ 21%. All these results are improved compared to the earlier reported investigations. [ABSTRACT FROM AUTHOR]

Presented is a new compact dual‐band quadruple planar inverted‐F antenna (QPIFA) radiating right‐hand circular polarisation characteristics. The size of the proposed dual‐band QPIFA is 35 × 35 × 10 mm3 and the experimental results exhibit a peak gain of 2.5/4.5 dBic and an axial ratio under 1.5 dB in two target frequencies. [ABSTRACT FROM AUTHOR]

The development of a dual polarised microstrip antenna for S‐ and C‐band with improved characteristics is presented. It is dual linearly polarised at S‐band and dual circularly polarised at C‐band. Two orthogonal feeds have been conceived for proximity coupling at S‐band. The other two composite feeds are aperture coupled at C‐band. These generate left‐hand and right‐hand circular polarisations exclusively. The antenna reveals 3.5% or more impedance bandwidth at the S‐band ports with an isolation better than 22 dB (the best isolation is ≈31.5 dB at the band‐centre). It yields >21.2% impedance bandwidth and about 10.2% axial‐ratio bandwidth at each of the C‐band ports, both being improved compared to the earlier reports. Achieved isolation between the C‐band ports is better than 18.5 dB (≈23.5 dB at the centre of the working band). [ABSTRACT FROM AUTHOR]

A new tri‐band dual‐polarised omnidirectional antenna is proposed. The dual‐polarised antenna consists of a metal cuboid body with a vertical slot for horizontal polarisation (HP) and a rectangular back metal cavity with two folded horizontal slots for vertical polarisation (VP). A metal HP feedline is employed to coupling feed the vertical slot while a metal VP feedline is used to excite the two horizontal slots. Due to the coupling feed and the orthogonality between the vertical and horizontal slots, the dual‐polarised antenna features three bands and a high isolation. Experimental results show that the tri‐band dual‐polarised antenna covers the Chinese Unmanned Aircraft System bands (840.5–845, 1430–1444 and 2408–2440 MHz) with reflection coefficients <−10 dB and isolation >32 dB. Good omnidirectional radiation patterns are observed for both HP and VP. [ABSTRACT FROM AUTHOR]

A novel and compact tri‐band microstrip‐fed monopole antenna with dual‐polarisation characteristics for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is proposed. The antenna is composed of a partial ground and a Y‐shaped radiating patch that consists of two unequal monopole arms and a modified circle monopole. The antenna is able to generate three separate impedance bandwidths to cover the frequency bands of the WLAN (2.4–2.484 and 5.8 GHz) and the WiMAX (3.4–3.7 GHz). In addition, the antenna is circularly polarised in both the WLAN bands. Furthermore, the antenna structure is extremely simple, durable and occupies small space, making it suitable for practical applications. [ABSTRACT FROM AUTHOR]