Microstrip patch antenna array for range extension of RFID applications

In this paper, an UHF band 2X2 microstrip phased antenna array is designed for extending the range of an RFID reader system. The phased antenna array operates at the frequency of 867 MHz, as specified in Gen2 protocol European standards. The phased antenna array has four microstrip patch antennas, three Wilkinson power dividers and a transmission line phase shifter printed on the same Arlon AD450 substrate with a dielectric constant of 4.5 with dimensions of 34x45 cm. The phased array antenna has a measured directivity of 9.5 dB and the main beam direction can be switched between the angles of ± 40 degrees with a 3dB beamwidth of 90 degrees. The phased antenna array can be used to extend the RFID system working range

UHF SATCOM broadband CP antenna: moxon type bent-dipoles over a ground plane

In this paper, we investigate and compare two different antenna types for UHF SATCOM applications; proposed Moxon type (bent dipole) and conventional egg beater (loop) antennas in terms of antenna performance and physical size. Bent dipole and egg beater antennas are simulated using HFSS software. Prototype antenna for Moxon type is also fabricated and measured for its return loss using Agilent network analyzer and compared to that of an egg beater antenna. Antenna gains are also simulated. Simulation results show that Moxon type antenna has more impedance bandwidth than egg beater antenna with smaller dimensions and hence can be used for broadband SATCOM applications

A 77 GHz on-chip strip dipole antenna integrated with balun circuits for automotive radar

In this paper, design and implementation of a 77 GHz on-chip strip dipole antenna integrated with both lumped and transmission line based balun circuits are presented. The on-chip antenna is realized by using IHP’s 0.25 μm SiGe BiCMOS technology with localized back-side etch (LBE) module to decrease substrate loss. The strip dipole antenna is fed by both a lumped LC circuit and strip line tapered baluns integrated on the same substrate and occupies an area of 1x1.2 mm2 including the RF pads. For increased directivity, the antenna sits on a grounded silicon substrate. Experimental results show that antenna is well matched around the design frequency and achieves 7 GHz impedance bandwidth (minimum return loss of 17 dB) for the LC balun circuit. The antenna and its feeding structure are well suited for 77 GHz single chip automotive radar applications

Directional GPS antenna for indoor positioning applications

In this paper, a directional GPS antenna for L1 frequency - 1575 MHz - with RHCP and a high directive gain is proposed for indoor positioning applications. The proposed antenna is made of a standard off the shelf GPS patch antenna with an additional conical reflector to enhance the gain and the beamwidth of the antenna. The angle of the cone reflector is optimized by HFSS 11 software. Finally, the cone is fabricated, integrated with the patch antenna and measured. The measurement results show that the antenna with the reflector has a 9 dBi gain and a beamwidth of 60 degrees with an axial ratio of 1 dB which agrees well with simulation results

Broadband circularly polarized antennas for UHF SATCOM

Novel circularly polarized (CP) antenna configurations derived from Moxon type antenna (bent dipole element over a ground plane) for broadband VHF SATCOM applications. A sequence of topologies starting from a single vertical element to two vertical elements of the Moxon arms, then widened strip arm elements were studied. Further, arms were widened to bow tie structures with bents at 900.for achieving broadband operation. Bow tie elements were further split and optimized at a certain angle to achieve wider bandwidth. The logic in this evolution was to obtain highest possible gain based on Fano-Chu limits, which suggests that higher gain can be achieved in an electrically small antenna with maximized metallization in the structure that fill the volume. Circular polarization is obtained by two Moxon based cross elements that are fed through a hybrid 900 quadrature coupler. For the antennas that are prototyped, return loss S11 measurements were performed, and gains are simulated using HFSS. For the band of 225-400 MHz, antenna gain varies between 8-12 dB, and S11 is measured to be below 10 dB. Fabricated antennas coupled to a hybrid coupler yielded excellent bandwidths, low cross-polarization and low back lobes on the finite ground planes

Minimal Massive Gravity: Conserved Charges, Excitations and the Chiral Gravity Limit

We find the excitations and construct the conserved charges ( mass and angular momentum) of the recently found Minimal Massive Gravity (MMG) in 2+1 dimensions in asymptotically Anti-de Sitter (AdS) spacetimes. The field equation of the theory does not come from an action and hence lacks the required Bianchi Identity needed to define conserved charges. But the theory, which also provides a healthy extension of the Topologically Massive Gravity in the bulk and boundary of spacetime, does admit conserved charges for metric that are solutions. Our construction is based on background Killing vectors and imperative to provide physical meaning to the integration constants in the black hole type metrics. We also study the chiral gravity limit of MMG.Comment: 9 pages, reference added, typos correcte

Chern-Simons Modified General Relativity: Conserved charges

We construct the conserved charges (mass and angular momentum) of the Chern-Simons modified General Relativity in asymptotically flat and Anti-de Sitter (AdS) spacetimes. Our definition is based on background Killing symmetries and reduces to the known expressions in the proper limits.Comment: 9 pages, References added, version to appear in Phys. Rev.