Zuping Qian

This letter presents a novel dual-polarized leaky-wave antenna (LWA) based on mode-multiplexed feeding structure (FS). Substrate integrated waveguide (SIW) with groove arrays is exploited to achieve mode-multiplexed FS and two working modes are excited at the same frequency range utilizing different feeding methods. Thirteen dumbbell-shaped patches are placed above the proposed FS and fed through coupling, achieving leaky-wave radiation. When the FS is excited by the microstrip line port, even-mode is obtained and the LWA works in horizontal polarization. With the slotline port excitation, odd-mode is excited and the LWA works in vertical polarization. Therefore, a dual-polarized LWA is realized by using one single transmission line with one type of radiating elements, leading to mode multiplexing in feeding structure and polarization multiplexing in radiating part. A prototype was fabricated and tested for verification. Measured results reveal that the beams can scan from backward to forward under two polarizations. Within the working bandwidth, the cross polarization below −20 dB is realized in the beam-scanning plane.

In this communication, we propose a novel feeding scheme to design a wideband filtering patch antenna. The antenna is composed of two substrates: the feeding and the radiating ones. Two circular patches are etched on the top surface of the radiating substrate as the radiators and a hybrid substrate integrated waveguide (SIW) and spoof localized surface plasmon (SLSP) structure is used as the feeding scheme. Due to abundant resonant modes and filtering feature of the hybrid SIW-SLSP structure, the antenna can radiate under the triple-mode resonance with high filtering performance. Moreover, the proposed filtering antenna has an independently adjustable capability of both low-band and high-band radiation nulls. The presented antenna is designed, fabricated, and measured. The measured results reveal that the operating bandwidth reaches up to 11.3%, ranging from 7.44 to 8.33 GHz. The peak gain of 10 dBi is obtained in passband with 10 dB gain suppression out of the band. This approach provides a simple way to design wideband filtering patch antenna, which can be easily integrated with planar circuit.

In this letter, a wideband beam-scanning antenna with circular polarization (CP) characteristics is proposed. The antenna is designed based on an air-filled substrate-integrated waveguide (SIW), which is composed of three layers of printed circuit board. Since the medium is dug out, the transmission structure has low-loss characteristics. An array of slots is etched on the top layer as radiating elements. Due to the fast-wave characteristic of the air-filled SIW, the antenna can radiate over a wide bandwidth. The proposed antenna is designed, fabricated, and tested. Within the frequency band of 12-18 GHz (40% relative bandwidth), the measured scanning angle is from 28° to -13°. The antenna axial ratio is below 3 dB at the corresponding maximal beam direction, and the gain is above 10.30 dBic over the whole band. This antenna has potential applications in the satellite and wireless communication systems for its advantages of wideband, low loss, CP properties, low cost in fabrication, and simplicity in design.

Automatic modulation classification (AMC) is a key technology of cognitive radio used in non-cooperative communication. Recently, deep learning has been applied to AMC tasks. In this paper, an AMC scheme based on deep learning is proposed, which combines random erasing and attention mechanism to achieve high classification accuracy. Firstly, we propose two data augmentation methods, random erasing at sample level and random erasing at amplitude/phase (AP) channel level. The former replaces training samples with noise information, while the latter replaces AP channel information of training samples with noise information. Erased data segments are randomly stitched to enable training data expansion. Training data of different qualities enables deep learning model to have stronger generalization capability and higher robustness. Then, we propose a single-layer Long Short-Term Memory (LSTM) model based on attention mechanism. In the first part of this model, we propose the signal embedding, which enables the input to contain modulation information more comprehensively and accurately. Then hidden state output by LSTM is input into the attention module, and weighting is applied to the hidden state to help the LSTM model capture the temporal features of modulated signals. Compared to a model without attention mechanism, this model has faster convergence speed and better classification performance. Lastly, we propose a random erasing-based test time augmentation (RE-TTA) method. Test data is randomly erased for multiple times and classification results are comprehensively evaluated, in order to further improve classification accuracy. Experimental results on dataset RML2016.10a show that classification accuracy of the proposed scheme is competitive compared with the state-of-the-art methods.

In this communication, a novel wideband fixed-beam leaky-wave antenna (LWA) is proposed. The antenna is designed based on air-filled substrate integrated waveguide (SIW), which is composed of one layer of printed circuit board (PCB) in the middle and two layers of thin copper plates on the top and bottom. The different layers are aligned and fixed by screws. A long slot is etched on the top surface of air-filled SIW as a radiator. Due to the dispersive characteristic of the air-filled SIW, the antenna can radiate at a fixed direction over a wideband. To the best of our knowledge, this is the first time that the air-filled SIW is adopted for LWA design. The proposed antenna is designed, fabricated, and tested. The measured results show that its wide operating bandwidth reaches up to 37.0%, ranging from 11 to 16 GHz. The excellent fixed-beam radiation performance is obtained over the operating bandwidth. The radiation direction is fixed at 59° with only ±3° variation, and the peak gain is within 14.0-15.3 dBi. Although the beam angle can only be fixed nearly the endfire, this method offers a simple way to realize wideband fixed-beam feature.

A novel substrate integrated waveguide horn antenna loaded with offset double-sided parallel-strip lines (DSPSL) is proposed in this letter. The severe mismatch between horn aperture and free space leads to narrow impedance bandwidth when the substrate thickness is much smaller than the wavelength (typically less than λ ₀ /6). Two groups of periodic offset DSPSL structure are placed in front of the horn aperture, which acts as an impedance transformer to realize smooth transition. Good impedance matching can be easily realized by modifying the constitutive parameters of the offset DSPSL structure. Measured results show that the impedance bandwidth can be improved up to 20.5% from 14 to 17.2 GHz with a low profile less than λ ₀ /13. Stable end-fire radiation patterns are obtained across the bandwidth.

One novel single-feed single-layer wideband circularly polarized (CP) magneto-electric dipole antenna (MEDA) with enhanced gain property is presented in this communication. By loading co-planar spiral with the radiating patch, the unidirectional radiation gain of the antenna is effectively improved while the impedance bandwidth and axial ratio (AR) bandwidth unaffected. Surface current distributions with/without the spiral are compared to reveal the antenna’s mechanism. The measurement shows that the left hand circular polarization (LHCP) antenna features impedance bandwidth from 11.4 to 18.5GHz (or 52%), an AR bandwidth from 13.2 to 18GHz (or 32%), the maximum gain of 11.1 dBic at 16.9 GHz with 3-dB gain bandwidth from 12.5 to 18.6 GHz (or 36.1%). Owning to the low profile, broadband and high gain, the proposed antenna is a capable candidate for satellite communication.

In this communication, a compact circularly polarized (CP) substrate integrated waveguide (SIW) horn antenna is proposed and investigated. Through etching a sloping slot on the common broad wall of two SIWs, mode coupling is generated between the top and down SIWs, and thus, a new field component as TE01 mode is produced. During the coupling process along the sloping slot, the difference in guide wavelengths of the two orthogonal modes also brings a phase shift between the two modes, which provides a possibility for radiating the CP wave. Moreover, the two different ports will generate the electric field components of TE01 mode with the opposite direction, which indicates the compact SIW horn antenna with a dual CP property can be realized as well. Measured results indicate that the proposed antenna operates with a wide 3-dB axial ratio bandwidth of 11.8% ranging from 17.6 to 19.8 GHz. The measured results are in good accordance with the simulated ones.

A novel substrate-integrated waveguide (SIW) horn antenna with partially detached broad walls is designed and analyzed. The conventional SIW horn antenna suffers from narrow-operating bandwidth, which mainly results from the mismatch at the horn aperture between the substrate and the free space. However, the detachment of the broad walls makes the left substrate not only act as wave-guiding structure but also impedance transformer, which brings much size reduction in comparison with conventional SIW horn antenna. Moreover, the substrate with graded dielectric constants distributed in the propagating direction is realized through perforating air-vias with different diameters to further improve the radiation performance. Results indicate that the proposed antenna operates from 17.7 to 26.7 GHz with a nearly constant peak-radiating gain between 8 and 9 dBi at end-fire direction. Stable end-fire radiation patterns can be realized in the whole operating band. Above all, the proposed technology makes it compact to design SIW horn antenna of high performance without extra extension after the aperture of the radiating horn.