A 3-bit beam steerable antenna array based on a microstrip line is designed and implemented at 28 GHz for millimetre-wave application. The antenna consists of an 8-element tightly stacked aperture and a switchable feeding network. The latter consists of a one-to-eight-way uniform microstrip corporatefed power divider and is separated from the radiating element by a ground plane. To achieve coupled feeding, the ground plane has two rows of slots under each antenna element. A switching mechanism was implemented on the microstrip line to realize 3-bit periodic phase shifting for beamsteering. By sampling 8 feed points with a separation distance of λ/8, a 3-bit phase shifter was constructed with phases of 0and −315 • . Continuous beamsteering was achieved from −50 • to +50 • by switching eight different sampling states, both in numerical calculation and in simulation. The design was verified by fabricating and testing three different prototype configurations at 28 GHz. The measured prototypes showed an excellent match with the simulation results. Notably, the maximum measured gain was found to be 13.44 dBi with a gain threshold of 10 dBi within the steering range (viz. 100 • ).INDEX TERMS Reconfigurable, millimeter-wave antenna, aperture-fed antenna, 3-bit-phase shifter, beamsteering.

A corporate feeding antenna array with parasitic patches has been investigated previously for millimeter-wave applications due to its high gain and wide bandwidth. However, the parasitic patch integration in the uniformly powered and spaced patch antenna array led to a high sidelobe level (SLL). In this study, we designed a non-uniformly powered and spaced corporate feeding network to feed a 12-element parasitic patch-integrated microstrip antenna array for SLL reduction at 28 GHz in the millimeter-wave band. In the power divider, we arranged two one-to-six unequally feeding power dividers from the opposite side to feed 12 antenna elements with non-uniform excitation, and effectively controlled the spacing between antenna elements. The two opposite input ports from the power divider were fed 180° out-of-phase for good isolation between the adjacent antenna elements. To verify the SLL reduction effect from the non-uniform spacing in the array, we designed two non-uniformly powered patch antenna arrays with uniform and non-uniform spacing. In the measurement, the non-uniformly powered and spaced patch antenna array demonstrated a nearly 16.56 dBi boresight gain and −17.27 dB SLL, which is nearly 2 dB lower than the uniformly spaced counterpart. Finally, we expect that the non-uniformly powered and spaced high gain patch antenna array with a low SLL will be suitable for millimeter-wave communication applications.

For simultaneous transmit (Tx) and receive (Rx), it is a common practice, with monostatic full duplex (FD) systems, to use a single antenna and a circulator to provide isolation between the transmit and receive radio chains. However, most circulators currently on the market are designed to provide 12 to 20 dB of Tx/Rx port isolation, which is not sufficient for full duplex (FD) microwave communication. In fact, it is necessary to provide at least >30 dB of isolation to prevent the receiver desensitization that is caused by the leakage of high-power transmit signals. For this reason, practical simultaneous transmit and receive (STAR) systems require additional cancellation stages. In this paper, we present a novel STAR system that incorporates two circulators, a hybrid coupler, and a self-interference cancellation (SIC) circuit, based on a Finite Impulse Response (FIR) topology. Our design achieves an average Tx/Rx port isolation of ∼37 dB over a 25 MHz bandwidth (viz. 2.395-2.42 GHz) in simulation, with a minimum and maximum cancellations of 35 dB and 41 dB, respectively. A prototype was fabricated and tested showing good agreement with the simulations. All in all, the prototype achieved an average cancellation of 36 dB, with a cancellation range of 33 dB to 42 dB. INDEX TERMS Coupling signal, in-band full duplex (IBFD), simultaneous transmit and receive (STAR), self-interference cancellation (SIC).ELIAS A. ALWAN (Member, IEEE) was born in Aitou, Lebanon, in 1984. He received the B.E. degree (summa cum laude

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In this paper, we propose dual microwave-excited atmospheric-pressure plasma jets (DME-APPJs) that can be generated with a single power source. A T-junction power divider that evenly distributes the input power to two ports is used, and two coaxial transmission line resonators are used as plasma generators for the DME-APPJs. The power divider distributes the incoming power in port 1 and supplies 46% of this power to port 2 and port 3, respectively. Surface treatments are conducted by exposing the multiple plasma jets to polypropylene (PP) specimens and then confirming the degree of hydrophilic change. Using the proposed DME-APPJs, it is possible to perform surface treatments on areas that are up to 50% larger compared to using two single ME-APPJs with the same power consumption. The DME-APPJs thus show more advanced performance for surface treatments by comparison with the single ME-APPJ.