R.V.S. Ram Krishna

A Horizontally Polarized Rectangular Stepped Slot Antenna for Ultra Wide Bandwidth With Boresight Radiation Patterns

In this paper, a horizontally polarized UWB antenna is proposed. The UWB nature of the antenna is achieved using a stepped impedance microstrip feed line to excite the stepped slot configuration. The -10 dB experimental impedance bandwidth acquired from VNA is 10 GHz (from 3.2 GHz to 13.2 GHz) which is 122% at the center frequency of 8.2 GHz. Symmetric feeding of the slot ensures good polarization characteristics and uniform radiation patterns throughout the operating band. The measured co to cross polarization ratio in boresight direction is around 15 dBi over most of the frequencies while the average peak gain is around 5 dBi. With the help of parametric studies, the choice of the antenna dimensions is justified. Finally, a modified design with band-notch characteristics to suppress interference from 5 GHz WLAN systems is presented. The simulated and measured results are in good agreement.

A Dual-Polarized Square-Ring Slot Antenna for UWB, Imaging, and Radar Applications

In this letter, a dual-polarized slot antenna for ultrawideband (UWB) applications is proposed. The slot has an overall shape of a square ring whose four arms are identical and stepped rectangular. While two adjacent arms of the ring are microstrip-fed and are responsible for the orthogonally polarized fields, the other two arms are introduced to make the structure symmetric and reduce the cross polarization. The impedance matching and isolation are controlled by properly shaping the slot arms and the feed section and by insertion of narrow metallic and slot stubs. The measured impedance bandwidth is 120% (3.0-12.0 GHz). The isolation is better than 20 dB over most of the band. With the help of radiation patterns and aperture electric field distribution, the dual-polarized nature of the antenna is justified. The antenna will be useful for UWB multiple-input-multiple-output (MIMO) transmission, polarimetric radar, and medical imaging applications.

Design of ultra wideband hexagonal patch slot antenna for high-gain wireless applications

In this paper, a CPW-fed modified rectangular slot antenna with ultra wideband characteristics is proposed. The slot has on one of its sides, a rectangular extension of smaller size which introduces asymmetry in the design. The CPW feed is terminated on a hexagonal-shape patch which protrudes into the slot centre and excites the slot. The antenna exhibits an impedance bandwidth of 134% at the centre frequency of 8.8 GHz. The radiation patterns of the antenna are simulated and measured and found to have omni-directional characteristics in the H-plane. In order to increase the gain of the antenna and make it directional, a multi-layer FSS is designed and fabricated. By implementing the FSS, the gain is enhanced by 3–4 dBi throughout the band. To verify the time domain performance of the antenna with and without the FSS, the group delay and fidelity factors (FF) are calculated. While the variations in the group delay are seen to be minimal, the FF are found to be within acceptable limits thus indicating good time domain characteristics with no significant loss of information in the received pulse.

A circularly polarised planar slot antenna for UWB applications

A printed rectangular slot antenna for circular polarisation (CP) is presented in this letter. The slot is excited by a CPW feed terminated on a circular disc. Inverted L-shaped strips are attached to the corners of the slot to obtain the desired CP characteristics. A slant rectangular slit cut in the circular disc enhances the CP behaviour. The antenna has a measured impedance bandwidth from 2.5 GHz to 15.0 GHz (143%), whereas the measured 3-dB axial ratio bandwidth (ARBW) is from 4.36 GHz to 6.15 GHz (33%). An improved version of the antenna is also proposed with simulated ARBW of 52% (4.35 GHz to 7.4 GHz) and measured ARBW of 44% (4.7 GHz to 7.35 GHz). The antenna can be useful for applications requiring CP over this frequency range and linear (vertical) polarisation over the rest of the impedance bandwidth.

A compact microstrip-fed open slot antenna for dual slant polarization with good isolation

Abstract A V-shape slot antenna for dual slant polarization is proposed. The slot is the union of two stepped rectangular slots tilted at ±45° with the vertical. Each section of the slot is excited using a microstrip feed line printed on the other side of the substrate. The feed is also stepped and bent so as to cross the slot at right angles. The decoupling between the ports is provided by means of narrow rectangular stubs placed at the intersection of the slot arms. Measurements taken on the fabricated prototype indicate an impedance bandwidth from 3.3 to 12 GHz with isolation better than 15 dB across the band. The aperture electric field distributions as well as far field radiation patterns are used to verify the dual slant polarization achieved with the antenna. The time domain characterization of the antenna is done by calculating the fidelity factor which is found to be >0.75 indicating suitability of the antenna for pulse transmission. For determining the diversity behavior, the envelope correlation coefficient is calculated and found to be below 0.004. The antenna has a peak gain from 4 to 6 dBi. A modified design of the antenna is also presented with impedance bandwidth from 3 to 12 GHz and isolation better than 20 dB from 3.7 GHz onwards. With compact features and wideband return loss and isolation, the antennas are expected to be useful for diversity applications in ultra wideband communication devices such as MIMO wifi, imaging radars, and polarimetric sensing devices.

A dual polarized UWB slot antenna with kite shaped slot for high isolation

In this paper, the design of a two port antenna for ultra wideband applications is presented. The radiating element in the antenna is an L-shaped slot which is excited using two microstrip feed lines for generating the orthogonal polarizations. The slot and the feed lines have stepped profiles for achieving wideband impedance matching. The decoupling between the ports is provided by means of three different structures. First, a slant metallic strip is attached at a corner inside the L-shape slot, next, a trident shaped slot is etched below the L-shape slot near its corner and finally, a kite shaped slot is placed in the center. The impedance bandwidth achieved with the antenna is from 3 GHz to 11.6 GHz while the isolation is better than 20 dB from 3.8 GHz onwards. The dual polarized nature of the antenna is shown from the aperture electric field distribution and the radiation patterns. The peak gain of the antenna varies from 4 to 6 dBi over the band. The antenna is expected to be useful for dual polarization applications in radar, imaging and high speed wireless communication.

A Dual Polarized Ultra-Wideband Slot Antenna Using Stepped Microstrip Feed Structure

Abstract In this paper, a printed slot antenna for ultra-wideband dual polarization is proposed and experimentally demonstrated. The slot is L-shape and its two arms are individually microstrip fed for producing the orthogonal polarizations. The slot arms and the microstrip feed lines are step sectioned for wideband impedance matching. For isolation purpose, a slant narrow metallic stub is inserted at the junction of the slot arms. The antenna has an impedance bandwidth of 118% (3.1–12 GHz) and isolation of around 20 dB over most of the band. The radiation patterns are nearly omnidirectional with a peak gain varying from 3 to 6 dBi. For assessing the diversity performance of the antenna, the envelope correlation coefficients are computed from the simulated and measured S-parameters and found to be within acceptable limits. With a compact, single substrate design, the antenna is expected to be useful for printed circuit ultra wideband applications requiring dual polarization features.

Design of asymmetric CPW fed slot antennas for pattern and polarization diversity

This paper presents the design of an ultra wideband slot antenna for MIMO diversity applications. The antenna has an asymmetric rectangular slot to achieve the broad band impedance matching. The simulated band width of the antenna is 3.0 to 12.0 GHz which is beyond the FCC band. For MIMO, the antenna is implemented in four different configurations. To assess the diversity performance, the envelope correlation coefficient, diversity gain and capacity loss are calculated for all the configurations. From a comparison of the results, it has been found that the antennas placed in the orthogonal configuration offer the best impedance matching and isolation over the band. The proposed antennas are compact and have a peak gain around 5dBi which increases slightly over higher frequencies in the operating band.

A fractal monopole antenna for UWB applications

A printed monopole antenna for UWB applications is presented in this paper. The monopole has a circular sector shape and is excited using a CPW feed. Quasi fractal elements in the form of triangular slots of varying dimensions are incorporated in the circular secto disc for obtaining the UWB behavior. The measured impedance bandwidth is from 4 GHz and extends well beyond 12 GHz. The measured radiation patterns of the antenna are nearly omni directional in the H-plane and dumb bell shape in the E-plane.

Design of horizontally polarized stepped slot antenna for ultra-wideband applications

A horizontally polarized ultra wideband stepped slot antenna is proposed in this paper. First, a stepped-slot structure is fed by an L shaped microstrip feed to achieve multiple resonances. Then a parasitic slot is introduced near the vertical arm of the L-shaped feed to get better impedance matching over the bandwidth of 3.7 GHz (5.0–8.7 GHz). Further, an impedance step is introduced in the feed line and the measured −10 dB impedance bandwidth covering from 2.8 to 12.8 GHz is achieved. The measured peak gain is around 4.5 dBi throughout the band. The measured radiation patterns are bidirectional in E plane and omnidirectional in H plane. The experimental results are in close agreement with the simulated results. This antenna can be used for ultra-wideband communication devices, medical imaging and vehicular radars.