Hemant Kumar

Normal Mode Helical Antenna on Small Circular Ground Plane

ABSTRACT In this paper, it has been shown that input impedance matching for the Normal Mode Helical Antenna (NMHA) can be obtained by using a small circular ground plane (radius λ/20) without any external impedance matching network. It also discusses the effect of the finite circular ground plane radius, the radius of wire on the input impedance, resonance frequency, and bandwidth of the NMHA. Further, the effects of different ground plane shapes and cupped shape ground plane bending in upward and downward directions on input impedance matching are presented. A prototype of NMHA has been fabricated to operate around 1.8 GHz and the measured results are in good agreement with the simulated results.

Coaxial Feed Pyramidal Horn Antenna with High Efficiency

ABSTRACT In this paper, a short pyramidal horn antenna with coaxial feed has been designed and fabricated with 52% bandwidth, which covers CDMA and GSM 900 bands. The total length of the antenna including coaxial feed is approximately 0.85λ at the lowest usable frequency. The effect of coaxial probe length, probe radius, and its location from the short wall of the waveguide on the resonance frequency, impedance matching, and bandwidth of the horn antenna have been analysed using CST Microwave studio software. Also, parametric analyses have been done by varying the horn length and aperture dimensions to study radiation characteristics of the horn antenna. The horn length has been optimized to obtain maximum efficiency for a fixed aperture. Simulation results show that as the frequency increases from 700 to 1130 MHz, the gain monotonically increases from 8.4 to 12.6 dBi with maximum efficiency of 80% at 850 MHz and it varies between 72% and 80% over this band. The pyramidal horn antenna has been fabricated and measured results are in good agreement with the simulated results.

Compact planar log-periodic dipole array based yagi-uda antenna

In this paper, a compact planar Yagi-Uda antenna based on two elements log-periodic dipole array has been designed to achieve an end fire directional characteristics over a broad range of frequencies. To feed the driven elements of log-periodic dipole array, a tapered microstrip balun is designed, which converts unbalanced coaxial feed to balanced microstrip line feed. The prototype of antenna has been fabricated on a low cost glass epoxy FR4 substrate with overall size of the antenna is 0.41λo × 0.54λo at center frequency (84mm × 111mm). The measured results have been compared with simulated results. Measured results show a bandwidth of approximately 41.4% centered at 1.45 GHz for VSWR < 2. Maximum gain is 7.2 dBi with nearly 1 dB variations over the bandwidth. Peak front to back ratio is 28 dB with better than 15 dB has been achieved over the bandwidth.

Broadband Planar Log-Periodic Dipole Array Antenna Based RF-Energy Harvesting System

ABSTRACT In this paper, a low-cost planar log periodic dipole array antenna has been described using triangular dipole elements for broadband RF energy harvesting applications. The antenna measured bandwidth for VSWR ≤ 2 is from 570 to 2750 MHz (1:4.8), which covers all the cellular bands. The radiation pattern is uniform over the entire frequency range. The measured gain is 7.2 dBi with less than ±0.5 dB variation over the entire bandwidth. A Schottky diode-based voltage doubler rectifier is used to convert RF energy to DC voltage. A broadband impedance matching network using an exponentially tapered microstrip line between log periodic antenna and rectifier has been designed. At a distance of 25 m from the cell tower, a voltage of 1.7 V was obtained using the developed broadband RF energy harvesting system across a load of 4.7 kΩ. A voltage of 3 V was obtained across the same load while initiating a call from a cell phone.

Normal mode helical antenna at 1.8 GHz with small circular ground plane

This paper describes the effect of wire with small circular ground plane size (radius < λ/20) for normal mode helical antenna at which resonance condition is achieved without using any external impedance matching network. A comparative study of variation in performance of helical antenna with respect to variation in thickness of wire and ground plane size at 1.8 GHz is carried out using simulation. By comparing various results, appropriate values of the parameters are selected and the proposed antenna has been fabricated and results are experimentally validated.

Microstrip antenna array with ratrace comparator at X-band for monopulse tracking radar

In this paper, a microstrip antenna array with ratrace comparator at X-band for monopulse tracking radar has been designed and simulated using IE3D software. To achieve better side lobe level and low cross polar components, the radiating antenna consists of mixed feeding technique. The bandwidth of 13.9% has been achieved for VSWR <; 2. The peak gain achieved is equal to 24.7 dBi with less than 1 dBi variations over the entire range of bandwidth. Side lobe level of better than 15 dB and a null depth of better than 30 dB has been obtained. The radiation pattern is symmetric in both the planes with HPBW nearly equal to 9.0°.

Compact waveguide monopulse comparator at Ka-band for monopulse tracking

In this paper, a compact waveguide monopulse comparator at Ka-band for monopulse tracking is presented. Simulated results show a bandwidth of nearly 6% for a return loss of better than 10 dB, an isolation of better than 40 dB between the ports, and a null depth better than 40 dB. There is an imbalance of +0.1/-0.8 dB and 1° in magnitude and phase respectively at the output ports.

An inverted suspended microstrip antenna array integrated with ratrace comparator at X-Band for monopulse tracking

In this paper, an inverted suspended microstrip antenna array with ratrace comparator at X-band for monopulse tracking radar applications has been designed and simulated using IE3D software based on method of moments (MoM). The radiating part of the monopulse antenna consists of hybrid feeding technique to achieve better side lobe level and high gain. The bandwidth of 8.6% has been achieved for VSWR < 2 from 8.96 GHz to 9.76 GHz. The maximum gain of 25.1 dB has been achieved with approximately 1 dB variations over the entire bandwidth. The sum radiation pattern shows a side lobe level of better than 17.5 dB in both azimuth as well as elevation planes. The difference radiation pattern shows a null depth of better than 28 dB. The radiation pattern is symmetric with HPBW of 6.3° and 7.1° in azimuth and elevation planes, respectively.

Single feed dual band circularly polarized stub loaded tunable microstrip patch antenna

A single feed dual band circularly polarized stub loaded tunable microstrip patch antenna operating at S-band has been designed and fabricated. The antenna is designed for center frequencies of 2.23 GHz and 3.85 GHz. Paper also present two more designs to make the antenna compact without much alteration in the results. The proposed antenna configuration is designed using IE3D simulation software. Antenna is designed on Arlon substrate having dielectric constant (εr) = 2.55, loss tangent (tan δ) = 0.001 and thickness = 1.6 mm. An Axial ratio of less than 2 dB is achieved at both the frequencies. Simulated and measured results are in good agreement.