A planar periodic leaky-wave antenna (PLWA) with continuous backward-to-forward beam-scanning capability and consistent gain is presented. The PLWA is made of a new type of periodically arranging meander line structures, in which the capacitive coupling between neighboring units plays the key role in achieving a high scanning rate. In detail, the beam-scanning rate of the proposed PLWA is efficiently tuned by varying the gap between two adjacent units, without considerably changing the working frequency band. To mitigate the open stopband (OSB) and to improve the impedance matching, several inductive open stubs are introduced into a single meander line unit cell to enhance the radiation. In the experiment, a prototype of the proposed PLWA was fabricated and measured. The simulated and measured beams show good agreement in terms of scanning range and radiation performance. A continuous beam scanning from −60° to +58° through broadside in the frequency band of 5.95–7.1 GHz is observed, and hence, a 102.6°/GHz scanning rate is realized in practice. Besides, the PLWA shows an average gain level of 11.96 dBi with a variation lower than 2 dB and a sidelobe below −10 dB at all the measured frequencies. The proposed PLWA may have potential applications in radar, microwave imaging, and wireless communication due to its compact structure, easy to fabricate, and dispersionless performance.

Backward-to-Forward Wide-Angle Fast Beam-Scanning Leaky-Wave Antenna With Consistent Gain

In this paper, a backward-to-forward continuous beam scanning leaky wave antenna is presented in substrate integrated waveguide technology. The antenna radiates from a continuous longitudinal slot etched on its broad wall. The slot is excited by using periodic H-plane steps. An impedance matched unit cell structure is used to suppress the open stopband in the broadside direction. Bloch wave analysis is used to obtain the propagation characteristics of the antenna. However, due to radiation being obtained only from the shunt-type radiating element, namely, the longitudinal slot, a gain dip is observed in the broadside direction. Transversal asymmetry is then introduced in the structure to eliminate the gain dip and obtain the consistent gain. A prototype of the antenna is fabricated and measured. Continuous beam scanning is achieved from −29o to +30o about the broadside direction with a gain variation of less than 2 dB over 8.0–12.4 GHz. A measured peak gain of 16.1 dBi is obtained. Key structural design parameters of the antenna are identified for controlling the leakage rate. Next, Taylor tapered aperture illumination is used to obtain low sidelobe level (SLL). The Taylor tapered antenna is also fabricated with the measured SLL below −21 dB.

Broadside Scanning Asymmetric SIW LWA With Consistent Gain and Reduced Sidelobe

A leaky-wave antenna (LWA) on a substrate integrated waveguide (SIW) with continuous beam-scanning capabilities and improved gain is presented. A one-dimensional (1-D) longitudinal slot-array SIW antenna is used as the main radiating element. It was found that due to the capacitive effect of the slot, an open-stopband (OSB) restrains broadside radiation. Although a reduction of the bandgap can be achieved when the slots are closer to the center, the radiation performance of the LWA degrades around the broadside as the beam scans from backward to forward. Initially, the capacitive effect was mitigated, and hence, the OSB was suppressed by introducing a group of three shorting vias at the opposite side of each longitudinal slot. However, the gain of the antenna drops significantly around its upper scan angles in the forward directions. To improve the radiation performance further, the center via of each of the via group is replaced by a transverse slot. The new unit cell is then used to design a modified 1-D slot-array LWA, and the antenna is analyzed, prototyped, and measured to verify the concept.

Continuous Backward-to-Forward Scanning 1-D Slot-Array Leaky-Wave Antenna With Improved Gain

In this letter, a novel dual-beam and tri-band leaky-wave antenna (LWA) based on substrate integrated waveguide (SIW) structure is proposed, which has the capability of wide beam scanning range including broadside direction. The antenna consists of two kinds of periodic structures which can excite two -1st spatial harmonic waves and result in two radiation beams simultaneously. Through theoretical dispersion diagram analysis of the unit cells of two periodic structures and by applying the techniques of impedance-matching and reflection-cancelling, the open-stopbands at broadside are suppressed. Then the main beam of the proposed LWA can scan from backward to forward through broadside when frequency changes. Moreover, a tri-band application can be achieved in the dual-beam antenna by optimization of the second periodic structure. The measured results validate that the proposed SIW LWA has three operating frequency bands. In band 1 from 8.6 to 9.2 GHz, there is one beam scanning from 42° to 71° in the forward, in band 2 from 10 to 12 GHz, there is one beam scanning from -40° to 4° in the backward, and in band 3 from 12.5 to 15 GHz, there is a dual-beam scanning from -55° to 54° including broadside direction, which show good agreements with the simulated results.

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Dual-Beam and Tri-Band SIW Leaky-Wave Antenna With Wide Beam Scanning Range Including Broadside Direction

Substrate-integrated circuits (SICs) [1] have attracted much attention in the last several years because of their great potential. The first implementation of the concept can be found in [2] as a feeding mechanism for a slot array antenna. Deslandes and Wu [3], [4] used the term substrate-integrated waveguide (SIW) to define this waveguide integrated in a substrate where the lateral walls are synthesized with metallized via holes, and the upper and lower walls are the top and bottom metallization of the substrate.

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Empty SIW Technologies: A Major Step Toward Realizing Low-Cost and Low-Loss Microwave Circuits

In this article, a periodic leaky wave antenna (LWA) is presented for fixed frequency beam scanning in microstrip line technology. Both the beam angle and the beamwidth can be controlled electronically. The unit cell of the antenna is loaded with shunt stubs, which are either short or open-circuited, using p-i-n diodes as a switch. The switching of the stub alters the impedance loading of the antenna, leading to a change in the propagation constant and thus the main beam angle. The input impedance of the stubs is chosen for symmetrical beam scanning through the broadside direction. A total of 50 distinct main beam positions with an angular separation of approximately 1° are selected from the different switching states using an iterative process. The second set of p-i-n diodes are inserted between the consecutive unit cells to control the leakage and, hence, the beamwidth. The antenna is fabricated and measured at 2.45 GHz. The measured main beam angle scans from −26° in the backward direction to +24° in the forward direction, through broadside, with an overall measured gain variation of 1.2 dB. Also, the beamwidth can be continuously tuned up to a maximum of 204%, keeping the gain variation within 1.2 dB.

Broadside Scanning Fixed Frequency LWA With Simultaneous Electronic Control of Beam Angle and Beamwidth

In this letter, a microstrip-based periodic leaky-wave antenna is designed for backfire radiation. Top-plane periodic open-stubs along with periodic rectangular slots in the ground plane are used to align radiating E -field in the top and bottom sides of the antenna in the same phase. This helps to achieve perfect backfire radiation from the n = –1th space harmonic, which is a fast wave. A transmission line model is presented to explain different radiation modes. A prototype of the antenna is fabricated and measured. Backfire radiation is obtained at 11.95 GHz with a measured peak gain of 12.7 dBi and cross-polarization level below –27 dB. Next, Taylor tapered aperture illumination is introduced for low sidelobe levels. The measured gain, sidelobe, and cross-polarization levels of the tapered antenna are 13.8 dBi, –18.5 dB, and –33 dB, respectively, at 12 GHz.

Backfire Microstrip Leaky-Wave Antenna With Reduced Sidelobe and Low Cross Polarization

A dual-beam substrate integrated waveguide (SIW) periodic leaky wave antenna (LWA) is designed and fabricated. The dual-beam operation is obtained by using leakage from the side walls of the SIW. The two beams are mirror image of each other. The feeding arrangement is simple and the antenna as a whole is easy to fabricate. A backward end fire to forward end fire scanning range of almost 74° is obtained by varying frequency from 8.5GHz to 13.3GHz. Side lobe level is better than 13dB in the specified frequency range. Measurement results match well with simulated results.

Dual-beam substrate integrated waveguide periodic leaky-wave antenna

In this paper, a novel excitation technique by a commercially available SMA connector is presented for the empty substrate integrated waveguide (ESIW). The SMA connector is directly connected to one end of the ESIW. A prototype back-to-back transition is designed and fabricated for X-band operation. Measurement results show that the insertion loss of the back-to-back transition is below 1 dB over 7.15 GHz to 12.5 GHz. Losses from the transition are studied in details. The transition has a compact dimension of 22 mm∗3.5 mm.

Ravi Shaw

Papers

Broadside Scanning Asymmetric SIW LWA With Consistent Gain and Reduced Sidelobe

Broadside Scanning Fixed Frequency LWA With Simultaneous Electronic Control of Beam Angle and Beamwidth

Backfire Microstrip Leaky-Wave Antenna With Reduced Sidelobe and Low Cross Polarization

Dual-beam substrate integrated waveguide periodic leaky-wave antenna

A compact and wideband SMA connector to empty substrate integrated waveguide (ESIW) transition