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

RFID coverage extension using microstrip-patch antenna array

In this paper, a UHF-band 2 x 2 microstrip phased-array antenna is designed and implemented to extend the coverage of an RFID reader system. The phased-array antenna has four microstrip-patch antennas, three Wilkinson power dividers, and a transmission-line phase shifter. These are printed on a dielectric substrate with a dielectric constant of 4.5. The array has dimensions of 34 cm x 45 cm, operating at a frequency of 867 MHz, as specified in RFID Gen2 protocol European standards. The phased-array antenna has a measured directivity of 12.1 dB, and the main-beam direction can be steered to angles of +/- 40 degrees, with a HPBW of 90 degrees. The phased-array antenna is used as the receiving antenna in a commercial reader system. Experimental results indicate that the coverage of the RFID system with the phased-array antenna is superior to the coverage with a conventional broader-beamwidth microstrip-patch antenna. The proposed system can also be used for a wireless positioning system

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

A 77GHz on-chip microstrip patch antenna with suppressed surface wave using EBG substrate

This paper presents the design of a patch antenna with suppressed surface waves by means of applying an electromagnetic band-gap structure. Establishing th e antenna on high dielectric substrate such as Silicon makes it possible to integrate the antenna with RFIC active component and circuitry. However, the performance (gain and radiation pattern) of antenna will be degraded due to the presence of surface waves on a thick dielectric substrate. It is possible to des ign an engineered substrate that filters out the surface wave around the frequency of interest. Moreover, having high dielectric substrate will localize EM wave to substrate and hence reduce antenna gain. For this problem, available silicon etching technology is used to remove the substrate right under the patch and have a locally low dielectric constant substrate underneath the antenn a. Proposed microstrip antenna resonates at 77GHz with 7dB realized gain which can be used in array for Automotive Radar purposes. Simulation results show great improvement in radiation pattern and 3dB increase in antenna's broadside gain in comparison with antenna on normal substrate

An x-band RFIC active phase shifter

Abstract— An active RFIC X-band phase shifter is implemented using IHP SiGe HBT 0.25 μm SGB25V technology with an improved vector sum method. The chip is formed by a three way Wilkinson power divider, three phase delays for 0-120-240 degrees, three similar RFIC LNAs and a final three way Wilkinson power combiner on the same chip and occupies an area of 4x1.8 mm2. The circuit provides both phase and amplitude control without the need of any additional digital circuitry. Phase shifting is simply based on the weighted vector sum of three vectors which are separated by 120º from each other. All 0-360 degree phase can be scanned simply by this method with the addition of amplitude control. The RFIC LNA circuit is fabricated and measurement results show that LNA has a gain of 10 - 13 dB with in the band of 6-9 GHz and 2-3 dB NF within the same band. The simulation results show that the phase can be scanned from 0-360 degrees with average 7 degree resolution for a 2 dB amplifier gain change. The gain of the overall active phase shifter circuit is 12-13 dB with output gain flatness is 1 dB and the circuit consumes 15.36 mW power. The circuit combines the amplifier with phase shifter and can be used for X-band 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

A77 GHz on-chip dipole antenna with etched silicon substrate

In this paper, a 77 GHz microstrip dipole antenna is integrated on a layered 11.4 m SiO2 and a silicon substrate with thickness of 670 m. The unbalanced microstrip line is balanced by using a lumped LC circuit balun to feed both of the dipole arms. To decrease the substrate loss and hence increase the antenna gain, Localized Backside Etch (LBE) module offered by IHP is utilized to etch the area under the dipole antenna. For mechanical robustness, two walls of silicon substrate are left at the end of the dipole arms inside the etched area. The simulation results show a 3.2 dBi gain and 15 GHz bandwidth at 77 GHz

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