Mahima Arrawatia

RF energy harvesting system from cell towers in 900MHz band

An experimental RF energy harvesting system to harvest energy from cell towers is presented in this paper. An electromagnetically-coupled square microstrip antenna is designed and fabricated for deployment in the presented system. Antenna gain of 9.1dB and bandwidth from 877 MHz to 998 MHz is achieved. A Schottky diode-based single stage voltage doubler and six-stage voltage doubler has also been designed and fabricated for DC voltage generation. Measured results show that a voltage of 2.78V is obtained at a distance of 10m from the cell tower and a voltage of 0.87V is obtained at a distance of 50m.

Broadband Bent Triangular Omnidirectional Antenna for RF Energy Harvesting

In this letter, a broadband bent triangular omnidirectional antenna is presented for RF energy harvesting. The antenna has a bandwidth for VSWR ≤ 2 from 850 MHz to 1.94 GHz. The antenna is designed to receive both horizontal and vertical polarized waves and has a stable radiation pattern over the entire bandwidth. Antenna has also been optimized for energy harvesting application and it is designed for 100 Ω input impedance to provide a passive voltage amplification and impedance matching to the rectifier. A peak efficiency of 60% and 17% is obtained for a load of 500 Ω at 980 and 1800 MHz, respectively. At a cell site while harvesting all bands simultaneously a voltage of 3.76 V for open circuit and 1.38 V across a load of 4.3 k Ω is obtained at a distance of 25 m using an array of two elements of the rectenna.

Differential Microstrip Antenna for RF Energy Harvesting

A differential microstrip antenna with improved gain for RF energy harvesting is presented in this paper. The developed antenna can be used in either center grounded or differential configuration. The antenna is designed and fabricated for GSM900 band (890-960 MHz). The antenna has a gain of 8.5 dBi at the center frequency and exhibits VSWR ≤ 2 for frequencies between 870 MHz to 1.05 GHz. The efficiency of the antenna is 80%. The developed antenna finds its application in energy harvesting, RFID tags and in wireless communication circuits, where differential inputs/outputs are needed. A complete differential RF energy harvesting system with a peak efficiency of 65.3% for a load of 3 kΩ is also developed.

An Integrated CMOS RF Energy Harvester with Differential Microstrip Antenna and On-Chip Charger

This paper presents an energy harvesting system which extracts energy from radio frequency radiation for battery charging applications. It comprises of a new differential center tapped Micro strip antenna, off-chip matching circuit, on-chip novel CMOS rectifier and control circuitry in 180nm CMOS technology. For on-chip modules, thick oxide devices have been used so as to meet the charging requirements of the target batteries. The designed battery charging module charges either of 250 Ah and 10 Ah batteries according to the selected battery and available input power. The 250 Ah battery is charged at input power of 2dBm and 10 Ah battery is charged at input power of -6.5dBm. The fabricated antenna has a gain of 8.3dB and a VSWR less than 2 in the bandwidth from 844 to 970MHz. An efficient Periodic Steady State(PSS)-based power matching technique is also presented which improves the system efficiency. For 0dBm input power at 950 MHz to the antenna the proposed technique leads to 55.2% efficiency of RF to DC converter system. In addition to the integrated design a discrete rectifier using high frequency Schottky diodes and differential micro strip antenna at the input are fabricated. The discrete system uses the proposed matching technique and exhibits efficiency of 40% for-11dBm received power by the antenna.

Broadband RF energy harvesting system covering CDMA, GSM900, GSM1800, 3G bands with inherent impedance matching

A broadband RF energy harvesting system for harvesting energy from 800 MHz to 2.5 GHz is presented. A passive voltage amplification scheme and inherent matching technique using higher antenna impedance is employed to enhance the output voltage of the rectifier. A planar broadband folded dipole antenna having an input impedance of 300Ω is designed and fabricated. The measured VSWR is less than 2 from 825 MHz to 1.27 GHz and 1.67 GHz to 2.17 GHz. A RF energy harvesting system consisting of the high impedance antenna, Schottky diode based rectifier and a self oscillating boost converter is used to charge a 12 μAh battery to 3.8 V. At 844 MHz for a received power of -10.7 dBm the battery charges to 3.8 V. At 1.73 GHz the battery charges to 3.8 V for a received power of -5.72 dBm. Also using the designed RF energy harvesting system, a voltage of 4.4 V is measured for a load of 3 kΩ at 10 cm from a cell phone making a call.

Broadband rectenna array for RF energy harvesting

In this paper, a broadband rectenna array is designed and tested. The array is designed using a triangular monopole antenna. It has Su less than -10dB from 850 MHz to 2.6 GHz. The gain is greater than 3.5dBi from 900 MHz to 2.6 GHz and a maximum gain of 8.6dBi is achieved at 2 GHz. Efficiency of 76% and 29% is obtained for a resistive load of 560Ω at 900 and 1800 MHz, respectively. A voltage of 6.95V for a load of 4.3kQ is obtained close to a cell phone making a call.

A CMOS power amplifier with 180° hybrid on-chip coupler for 4G applications

This paper presents a CMOS Class AB power amplifier with an on-chip 180° hybrid coupler for 4G applications. Two-stage power amplifier architecture with a combination of low voltage core transistor and high voltage I/O transistors, is designed to achieve the power gain in the 180nm standard CMOS technology. The driver stage has a power gain of 18.5dB and linear output power of 12.9dBm. The power stage has a gain of 13.7dB and P1dB of 24.4dBm. The paper also presents an on-chip 180° hybrid coupler, designed in the same technology, for combining the power generated from individual power amplifiers. The measured results of the coupler show an isolation better than -30dB, S11 better than -20dB and, S21 and S31 equal to -5.4dB, at 2.35GHz. The complete differential power amplifier using the on-chip coupler gives P1dB of 26.4dBm and saturated output power of 27.4dBm. As compared to all the reported on-chip couplers configurations, use of 180° hybrid coupler leads to better load insensitivity as well as improved linearity due to the second harmonic cancellation.

Broadband omnidirectional antenna for GSM900, GSM1800, 3G, 4G and Wi-Fi applications

In this paper, a broadband omnidirectional antenna, consisting of three tapered monopoles is presented. The antenna has |S11| < −10dB from 880MHz to 2.52GHz. The gain of the antenna is greater than 2dBi over the entire bandwidth. The measured H-plane radiation pattern is omnidirectional with less than 8dB variation over the entire bandwidth. The antenna covers GSM900, GSM1800, 3G, 4G and Wi-Fi bands.

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.

Dual band dual circular ring monopole antenna

In this paper, a dual band planar dual circular ring monopole antenna is designed and fabricated on 1.6mm thick FR4 substrate. The measured bandwidth of the antenna is from 0.82-1.25 GHz and 1.65-2.79 GHz for return loss <; -10dB. This antenna finds its application in CDMA, GSM900, GSM1800, 3G, 4G and Wi-Fi bands. A uniform omnidirectional radiation pattern is also obtained over the entire bandwidth. The maximum gain of the designed antenna is 3.7dBi.