A spoof surface plasmon leaky‐wave antenna with circular polarization

In this article a circularly polarized (CP) leaky‐wave antenna (LWA) based on spoof surface plasmon (SSP) is proposed. Corrugated circular patches are loaded on either side of the SSP waveguide periodically and asymmetrically, which enables continuous CP beam steering from backward to forward quadrant eliminating “the open stopband” at broadside. The antenna exhibits an impedance bandwidth of 43.5% (<?10 dB) and a 3‐dB axial‐ratio bandwidth of 27.8%; within the impedance bandwidth from 4.5 to 7 GHz the radiation beam can be steered from 120° to 70°. With a ground plane placed underneath, the antenna can achieve average radiation gain and efficiency of about 10 dBic and 84.2%, respectively, showing a radiation gain increase of about 3 dB over that without a ground plane. The proposed SSP‐based CP LWA is expected to find applications in wireless communication systems based on planar antennas.     

Spoof surface plasmon polariton‐fed circularly polarized leaky‐wave antenna with suppressed side‐lobe levels

A wide‐angle scanning circularly polarized (CP) leaky‐wave antenna (LWA) with suppressed side‐lobe levels (SLLs) is proposed, which can be a good candidate for future radar and wireless communication systems. The LWA consists of 12 cross slotted elliptical patch elements, which are fed by a microstrip spoof surface plasmon polariton (SSPP) line. Two fundamental modes of the patch array with two orthogonal polarizations can be excited by the electromagnetic coupling between the array and the SSPP line. By optimizing the elliptical eccentricity e and etching cross slots on the elliptical patch array, a 90° phase difference is introduced, and then, the CP radiation is realized. A tapered aperture field distribution is also realized by adjusting coupling intensities between the patch elements and the SSPP line, which is beneficial to reduce the SLLs. The electrical size of the LWA is 1.29λ₀ × 6.02λ₀ × 0.08λ₀, where λ₀ is air wavelength at 12.9 GHz (broadside direction). Both the simulated and measured results indicate that the CP operating band is 12.0 to 15.0 GHz. The proposed CP LWA scans continuously from ?14° to 38°. In the whole operating band, the axial ratios are less than 3 dB, and the SLLs are less than ?20 dB as well.     

A compact leaky‐wave antenna using a planar spoof surface plasmon polariton structure

This article presents and validates a leaky‐wave antenna by using the spoof surface plasmon polariton (SSPP) technique. By properly designing the proposed SSPP unit, the SSPP wave can be switched between the confinement and radiation modes. A large radiation efficiency can be achieved by properly designing the modulation depth, which ensures that a compact SSPP leaky‐wave array can be realized by using a small number of SSPP radiation units. To verify the design, a prototype which consists of a SSPP feeding network and a 4 by 4 SSPP radiation units has been fabricated by using a low cost FR‐4 substrate. A good agreement between simulated and measured results has been obtained. The proposed array antenna shows the promising capability of the SSPP technique for leaky‐wave antenna applications.     

Bandwidth‐controllable band‐stop filter using spoof surface plasmon polaritons

This article presents a bandwidth‐controllable band‐stop filter based on spoof surface plasmon polaritons (SSPPs) transmission line in the microwave frequency band. The approach of introducing rectangular slots into the corrugation strips offers a greater degree of flexibility in the SSPPs unit cell design. Meanwhile, the high‐order mode can be pulled to the low frequency segment of interest. The lower and upper edge of the stop band of this filter, therefore, can be controlled independently and conveniently. An equivalent circuit model of this unique unit cell is proposed for analyzing stop band formation and guiding the design of this SSSPs filter. Both numerical simulations and measured results demonstrate excellent stop band performance of the filter. The proposed filter may have potential applications in the SSPPs‐based communication system.     

Wideband filtering power dividers using single‐ and double‐layer periodic spoof surface plasmon polaritons

In this article, four wideband power dividers (two are filtering power dividers) using single‐ and double‐layer periodic spoof surface plasmon polaritons (SSPPs) are proposed. Double‐sided parallel‐strip line is used to realize the wideband and low loss for the double‐layer SSPPs. T‐shaped SSPPs power dividers with large bandwidth, wideband isolation, and low loss using double‐layer SSPPs to single‐layer SSPPs transition are realized. Conventional coplanar waveguide is used as the output ports for the single‐layer SSPPs. Moreover, two new SSPPs power dividers with filtering performance are realized with adding via holes in the double‐layer SSPPs. The theoretical analysis, parametric study, and design procedure for these wideband power dividers are illustrated. In addition, for validity demonstration, four wideband SSPPs power dividers are fabricated in microstrip technology and characterized. Good agreements can be observed between the measured and simulated results, indicating good potential applications in the integrated plasmonic devices.     

A novel power divider with ultra‐wideband harmonics suppression based on double‐sided parallel spoof surface plasmon polaritons transmission line

A novel wideband power divider with ultra‐wideband suppression of harmonics is proposed in this paper. The power divider is composed of double‐sided parallel spoof surface plasmon polaritons transmission line (DSP‐SSPP‐TL) with periodical grooved bow‐tie cells. The cut‐off frequency of DSP‐SSPP‐TL can be flexibly adjusted by changing the parameters of bow‐tie cells. To demonstrate that, dispersion relations of the bow‐tie cells with different parameters are simulated, and three DSP‐SSPP‐TL counterparts are experimented. Then, a power divider centered at 3.31 GHz (f₀) is designed, fabricated, and measured. Experimental results indicate that the 10‐dB return loss bandwidth of the proposed power divider is about 146% from 0.9 to 5.73 GHz, and the upper stopband is extended up to 40 GHz (12.1 f₀) with the suppression level above 32 dB. Moreover, ultra‐wideband isolation between two output ports of the proposed power divider could be achieved by employing two lumped resistors between two DSP‐SSPP‐TLs.     

Eighth‐mode SIW based compact high gain leaky‐wave antenna

In this article, a novel electrically small eighth‐mode substrate integrated waveguide (EMSIW) based leaky‐wave antenna (LWA) in planar environment is presented. The proposed antenna uses 1/8th mode SIW resonator which helps to improve compactness of the design while maintaining high gain and increased scanning angle. The proposed SIW cavity is excited by a 50 Ω microstrip line feeding to resonate at dominant TE₁₁₀ mode in X‐band. The dimensions of the resonators are adjusted to keep resonant mode at same frequency. The fabricated prototype is approximately 5λ₀ long. Measured results show that the proposed leaky‐wave antenna is able to operate within frequency range of 8‐10 GHz with beam scanning range of 51° and maximum gain of 13.31 dBi.     

An SIW antenna utilizing odd‐mode spoof surface plasmon polaritons for broadside radiation

In this article, a substrate integrated waveguide (SIW) antenna utilizing odd‐mode spoof surface plasmon polariton (SSPP) for broadside radiation is proposed. Double gratings are etched on the top surface of SIW and the SSPP odd‐mode is excited on this hybrid SIW‐SSPP structure. The proposed SIW antenna has open‐circuit termination and can realize broadside radiation. A prototype of the SIW‐based odd‐mode antenna is fabricated. Reasonable accordance is achieved between measured results and simulated results. The antenna impedance bandwidth is about 5.5% (12.4~13.1 GHz) with |S₁₁| < ?10 dB. Stable broadside radiation is also realized within the operating band of 12.3~13.3 GHz and the measured gain varies from 5.66 to 6.34 dB in the frequency band. The proposed broadside radiation antenna is suitable for wireless communication systems due to its compact structure and good radiation performances.     

2D circularly polarized antenna array fed by spoof surface plasmonic waveguide

A two‐dimensional high‐gain circularly polarized (CP) patch array antenna operating in Ku band is proposed in this article. To excite a novel spoof surface plasmonic transmission line (SSP‐TL), which is mounted vertically on the ground, a waveguide with a transition are used for the momentum and impedance matching. A SSP‐TL 4‐way power divider is then used to feed a 4 × 7 circular patch array by travelling waves. Therefore, the CP radiation is generated on the patches located between the parallel SSP‐TLs. Avoiding the deterioration in axial ratio, 90° phase difference between adjacent SSP‐TLs is designed by tuning the height of the SSP‐TLs, as the dispersion property is influenced by the height of the corrugations obviously. The simulated maximum gain of 20.6 dBi is achieved at 15.2 GHz, together with the axial ratio of 0.8 dB. A prototype is fabricated and measured to validate the proposed antenna array.     

Spoof surface plasmon polariton band‐stop filter with single‐loop split ring resonators

A novel band‐stop filter with single‐loop split ring resonators (SRRs) is proposed for spoof surface plasmon polaritons (SPPs) at millimeter wave frequencies, achieving a miniaturized size of 0.052λ₀ × 0.278λ₀ at its resonant frequency. The SRRs provide both a low‐pass response as the rectangular corrugations used in the conventional SPPs and an additional band‐stop response induced by the resonance of SRRs. To verify this design, a back‐to‐back device with two coplanar waveguides as the input and output feeding was fabricated and characterized, the measured S‐parameters of which agree well with the simulation. The measured stop band is centered at 49 GHz with a ?10‐dB bandwidth of 4.1 GHz and a high Q‐factor of 93, in which the maximum attenuation is 31 dB. The filter has a low insertion loss of less than 2.8 dB in the pass band. Such approaches may find many applications to achieve compact millimeter wave circuits.     

Spoof surface plasmon polariton transmission line with reduced line‐width and enhanced field confinement

This article proposes a compact spoof surface plasmon polaritons (SSPPs) transmission line, by introducing capacitive loading metal strips to manipulate the dispersion characteristics and electromagnetic field confinement. Results validate that, compared with conventional rectangular‐grooved SSPP structure, the proposed SSPP transmission line features a line‐width reduction up to 53%, and moreover a tighter field confinement, that is, 67% reduction of confinement area. This proposed structure can be further implemented in silicon process with multiple metal layers for on‐chip transmission of terahertz signals.     

A broadband filter based on hybrid spoof surface plasmon and half‐mode substrate integrated waveguide structure

In this article, a novel design way of wideband bandpass filter (BPF) is proposed. A hybrid sharing waveguide based on spoof surface plasmon (SSP) and half‐mode substrate integrated waveguide (HMSIW) is developed. With low‐pass feature of SSP and high‐pass feature of HMSIW, the proposed waveguide is a BPF naturally and the filter bandwidth can be controlled by adjusting parameters easily. A filter sample is fabricated for verification and the measured 3‐dB bandwidth is 46%. The proposed new concept of filter design is attractive and can be used to develop different wideband BPFs.     

Wideband circularly polarized leaky‐wave antenna with flat gain using printed ridge gap waveguide

A wideband beam scanning circularly polarized (CP) leaky‐wave antenna (LWA) at Ku band is proposed based on the printed ridge gap waveguide (PRGW). In this design, the printed technology is used to realize the ridge gap waveguide (RGW) structure, and a substrate layer is introduced to replace the air gap layer in conventional RGWs. The proposed beam scanning CP LWA has been fabricated. Measured results of the fabricated antenna prototype are carried out to verify the simulation analysis. It provides a wide impedance bandwidth of 22% ranging from 12 to 15 GHz while performing continuous frequency beam scanning from ?2° to +47°. Furthermore, it maintains the excellent CP characteristic with axial ratio (AR) below 1.5 dB and a flat gain response with variation less than 2 dB in the entire operation frequency band.     

High‐efficiency leaky‐wave antenna with continuous wide‐angle scanning using hybrid composite right/left handed structure

A hybrid composite right/left handed (CRLH) structure based leaky‐wave antenna with continuous wide beam scanning is proposed in this article. Six series‐wound periodic units, combining spoof surface plasmon polariton (SSPP) with CRLH, form the radiating portion of proposed antenna. The unit is connected to the ground with metal hole, which provides the equivalent parallel inductance, and the unit is separated from its adjacent unit at prescheduled intervals, which provides the equivalent series capacitance. Additionally, the unit operates at balanced state and the open stopband is obviously suppressed. Dispersion diagram is also used to analyze this continuous scanning. A prototype of proposed antenna is fabricated and measured. The main beam of the antenna scans continuously from ?70° to +40° in the range from 5.2 to 8.8 GHz. The antenna radiation efficiency reaches a maximum of 92% in the working band. Measurement results agree quite well with the simulation, which indicate this leaky wave antenna can find potential applications in communication systems and radars.     

Wideband leaky‐wave antenna with consistent gain and wide beam scanning angle based on multilayered substrate integrated waveguide composite right/left‐handed transmission line

In this article, a wideband leaky‐wave antenna is designed for consistent gain and wide beam scanning angle by using the proposed multilayered substrate integrated waveguide (SIW) composite right/left‐handed transmission line (CRLH TL). The proposed SIW CRLH structure consists of two parts: an interdigital fingers slot of rotating 45° etched on the upper ground of the SIW, and a rotated parasitic patch beneath the slot. Due to the continuous phase constants change from negative to positive values of the proposed SIW‐CRLH under the balanced condition, the designed LWA can achieves a continuous beam‐scanning property from backward to forward over the operating frequency band. The designed antenna is fabricated and measured, the measured and simulated results are in good agreements with each other, indicating that the designed antenna obtains a measured continuous main beam scanning from backward ?78° to forward +76° over the frequency range from 7.7 to 12.8 GHz with a consistent gain of more than 9.5 dB. Besides, the designed antenna also exhibits a measured 3‐dB gain bandwidth of 45.1% with maximum gain of 15 dB. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:731–738, 2016.     

Full‐wave analysis of printed leaky‐wave phased arrays

In this work, we propose a full‐wave numerical approach for efficient analysis and design of printed leaky‐wave phased arrays. The proposed technique is based on the method of moments in the spectral domain applied to a leaky structure in a periodic environment. The implementation exploits suitable analytical manipulations to strongly improve numerical convergence. Planar array configurations based on microstrip leaky lines have been considered in detail for accurate evaluations of the relevant dispersion and radiation properties. The effects of phase‐shifted feeding of leaky lines have particularly been investigated as a function of the involved physical parameters, to achieve fundamental information on the beam scanning features both in elevation and azimuth. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 272–287, 2002.     

Wideband dual‐element leaky‐wave antenna with constant gain and enhanced broadside radiation bandwidth using multilayered composite right/left‐handed substrate integrated waveguide

In this study, a wideband dual‐element leaky‐wave antenna (DE‐LWA) is proposed to achieve constant gain and wideband broadside radiation by using multilayered composite right/left‐handed substrate integrated waveguide. The proposed DE‐LWA consists of two leaky‐wave radiator elements which are with slanted and vertical interdigital fingers slot arrays. To verify the simulated results, the proposed DE‐LWA is fabricated and measured. The measured results are in good agreement with the simulated ones, indicating that the fabricated antenna obtains broadside gain of 12.5 dB with variation of 1.0 dB over the frequency range of 8.725‐9.25 GHz (5.84%). Moreover, the proposed DE‐LWA also can provides a beam scanning property from backward ?80° to forward +80° over the frequency range from 7.4 to 12.7 GHz with a constant gain of more than 10 dB. Besides, the electromagnetic performances of this work are better than those of the recently reported similar work in the references.     

Goubau line based end‐fire antenna

This article proposes a simple and low profile planar Goubau line based end‐fire antenna. End‐fire radiation is achieved by modifying the Goubau line into inverted periodic arrangement of V‐shaped unit cells. Designed prototype is simulated and verified experimentally. Both the simulated and measured results are in good agreement. Proposed antenna radiates toward end‐fire direction between 7.8 and 8.3 GHz. The maximum gain of the antenna is obtained around 7.2 dBi. The average efficiency is observed 70% over the entire operating bandwidth. Proposed end‐fire antenna has a single metallic layer with simple configuration which is easy to fabricate and also easy to integrate with other electronics circuits. The proposed antenna can be used for satellite and RADAR applications.     

Dual‐polarized low sidelobe Fabry‐Perot antenna using tapered partially reflective surface

A novel dual‐polarized Fabry‐Perot (FP) cavity antenna with low sidelobes is proposed. Low sidelobes are obtained by using a tapered partially reflective surface (PRS) in the form of circular lattice instead of the conventional rectangular lattice. As the PRS can be regarded as a 2D leaky wave surface on which cylindrical waves propagate outward radially in the form of concentric rings, so arranging the PRS elements in the form of circular lattice and then applying tapering on it yields low sidelobes in both the E‐ and H‐planes. The performance of the proposed PRS is validated by fabricating a dual‐polarized FP antenna and measuring its radiation patterns. Peak realized gains of 18.6 and 18.5 dBi are obtained for horizontal and vertical polarizations respectively, giving an aperture efficiency of around 42%. Measured sidelobe levels are reduced to lower than ?21.3 dB in both the E‐ and H‐planes for the two orthogonal polarizations.     

Compact bilayer substrate integrated waveguide leaky wave antenna with dumbbell‐shaped slot based on the TE20 mode

In this article, a compact dual layer leaky wave antenna array is simulated and constructed using the substrate integrated waveguide (SIW) based on the TE₂₀ mode at the X‐ and Ku‐bands. The proposed antenna is designed by creating dumbbell‐shaped slots on the upper layer of the SIW. These slots have increased the antenna bandwidth so that the proposed antenna has a bandwidth of 9.5 to 13.7 GHz and a fractional bandwidth of 36%. In addition, to excite the TE₂₀ mode, an SIW power divider is used in the feeding network of the antenna located in the bottom layer. Moreover, the gain and directivity are other advantages of the proposed antenna so that at 12.5 GHz the antenna peak gain reaches to 15.7 dB. Antenna beam scanning angle is from 5° to 81°. This antenna is simulated and analyzed by the CST Microwave Studio software. The obtained results from the antenna test lab confirm the simulation results.