M. F. Karim

Integration of Circular Polarized Array and LNA in LTCC as a 60-GHz Active Receiving Antenna

A compact 60-GHz active receiving antenna array is designed and fabricated using low temperature co-fired ceramic (LTCC) technology. It integrates a 4 × 4 circularly polarized (CP) patch array and a 21-dB low noise amplifier (LNA) into the same package substrate. By applying a stripline sequential rotation feeding scheme the CP array exhibits a wide impedance bandwidth (SWR <; 2) and 3-dB axial ratio bandwidth, both over 8 GHz, as well as a beam-shaped pattern with a 3-dB beam width of 20° and a peak gain of 16.8 dBi. By applying a bond wire compensation scheme and low-loss transition optimization, the LNA is successfully integrated into the package. The final fabricated prototype measures only 13 × 20 × 1.4 mm3, demonstrates the good integration performance as well as the CP polarization characteristics in measurement, and is estimated to have a peak overall gain of at least 35 dBi.

Miniaturized reconfigurable and switchable filter from UWB to 2.4 GHz WLAN using PIN diodes

This paper reports a new miniaturized reconfigurable and switchable filter from UWB to 2.4 GHz WLAN bands by using pin diodes. First, a reconfigurable filter is developed which changes from bandstop to bandpass filter at the same UWB spectrum. This bandstop filter consists of two bended open stubs of quarter-wavelength and a connecting stub of half-wavelength. The bandstop filter reconfigure to bandpass filter when the two open bended stubs are shorted to ground using Avagos RF pin diode. Different design parameters are evaluated for the reconfigurable filter. A switchable filter is developed by connecting half wavelength stub to the reconfigurable filter. This switchable bandpass filter changes from UWB to 2.4 GHz WLAN by turning ON the pin diodes. The measurement results of the reconfigurable filter in the bandstop state shows a rejection bandwidth of 2.2 GHz and the insertion loss in the passband of 1.9 dB and similarly the reconfigurable filter in the bandpass state shows the insertion loss of 2.1 dB and 3-dB bandwidth from 3.6 GHz to 10.5 GHz. The switchable bandpass filter at 2.4 GHz shows an insertion loss of 0.9 dB and 3 dB bandwidth of 400 MHz. The area of the filter is (λg / 4)2, while the area of the filter realized using the non bending stubs and connecting lines is 2(λg / 4)2

5.8GHz circularly polarized rectennas using schottky diode and LTC5535 rectifier for RF energy harvesting

5.8GHz circularly polarized single element patch antenna and 2×2 antenna array for RF energy harvesting were designed and fabricated. A comparison between Schottky diode and LTC5535 for RF energy harvesting rectenna (rectifying antenna) was analyzed at WLAN frequency of 5.8GHz. Both rectennas are printed on Rogers 4003C substrate. Maximum gain at boresight tip was measured to be 3.4dBi and 8.0dBi for circular polarized single element patch antenna and array patch antenna respectively. And the measured return loss of the two types of antennas was measured to be −10.3dB and −20.3dB respectively. The maximum output DC voltage reading is 72.5mV for Schottky diode and 428.3mV for the LTC5535 rectifier, at a distance of 15cm from the transmitting reference antenna.

Highly efficient wireless energy harvesting system using metamaterial based compact CP antenna

This paper presents a highly efficient 2.4 GHz wireless energy harvesting system comprising of a metamaterial based circularly polarized (CP) antenna and a power management circuit. The antenna is designed at 2.4 GHz using a circular slotted truncated corner square patch radiator placed on reactive impedance surface (RIS) for antenna size miniaturization, better impedance matching and to improve the front-to-back ratio. The power management system integrates a matching circuit with a single stage Dickson charge pump and an ultra low power with high efficiency DC/DC boost converter/charger. The Dickson charge pump uses three Schottky diodes to minimize the losses at high frequency. The DC-DC converter (BQ25504) is capable of acquiring and managing low power levels. The measured axial ratio (boresight) is below 3-dB for the entire 2.40-2.48 GHz band and the 10-dB return loss band is from 2.35-2.49 GHz. The gain (boresight) of the antenna is around 4.6 dBic at 2.44 GHz. The proposed antenna shows an improvement in front-to-back ratio of around 3 dB with size reduction of approximately 22%. The power management system generates an output voltage level of 1.5 volts at -10 dBm and 4 volts at 0 dBm input RF power respectively. The overall efficiency of the proposed energy harvesting system is above 28%.

Miniaturized reconfigurable filter using PIN diode for UWB applications

This paper reports a new compact design of UWB reconfigurable filter which switches from bandstop to bandpass filter using pin-diode. First, a unit cell is developed which consist of two bended open stubs of quarter-wavelength and a connecting stub of half-wavelength. Two unit cells are cascaded by inductive stub to form a bandstop filter. Avago’s RF pin diode is used to switch the filter from bandstop to bandpass filter at the same resonant frequency. The equivalent circuit model and its parameters are extracted. The measurement results for bandstop filter shows a rejection bandwidth is 5.2 GHz and the insertion loss in the passband is 0.6 dB. For the bandpass filter, the insertion loss is 2.1 dB and 3-dB bandwidth is from 3.6 GHz to 10.5 GHz. The area of novel unit cell filter is ( λg/4)2 at the centre frequency of the bandstop, while the area of the filter realized using the non bending stubs and connecting lines is 2( λg/4)2 for the same bandstop characteristics.

Integrated 60-GHz LTCC circularly polarized antenna array

A 60-GHz wideband circular polarized (CP) patch array of 4×4 elements is designed and fabricated in low temperature cofired ceramic (LTCC) technology. By applying a strip line sequential rotation feeding scheme this array exhibits wide impedance bandwidth (VSWR<2) and 3-dB axial ratio (AR) bandwidth, both over 8 GHz. In addition, it exhibits a peak gain of 16.8 dBi and a beam-shaped pattern with a 3-dB beam width of 20º. With a grounded co-planar waveguide (GCPW) to strip line (SL) transition added to facilitate the testing, the array performance is not degraded except of a 0.6-dB peak gain penalty. The fabricated antenna sample measures 13×18.7×1.4 mm3. The wireless test is finally conducted to demonstrate the CP characteristic and wide impedance bandwidth over 8 GHz (VSWR<2) of this antenna.

A Curved Electromagnetic Energy Harvesting System for Wearable Electronics

In this paper, a new curved electromagnetic energy harvesting system is designed, developed, and tested. This system is able to capture energy through oscillatory motion and proposes the use of a curved oscillatory electromagnetic harvester over the regular linear electromagnetic harvester due to its ability to harvest energy in two directions while walking/running. This paper also examines how the curvature of an oscillatory energy harvester affects its conversion efficiency from kinetic energy to electrical energy which is then stored. An enameled copper coil, having 1000 windings, is fixed at the center of a high-density polyethylene tube, in which a freely moving neodymium iron boron (NdFeB) magnet is housed. The 0.21 m×0.016 m harvester curved at a 0.25 m radius is able to produce the no load dc voltages of between 2.55 and 4.07 V when shaken at frequencies ranging from 2 to 5Hz. The 0.140 kg prototype is also tested by the human body motion during walking and running. The experimental results show that the harvester could generate a power of 5.185 mW.

Linearly polarized and circularly polarized Arrays in LTCC Technology for 60GHz Radios

Designs towards low-cost highly-integrated 60GHz transceivers have been carried out using the multi-layer low temperature cofired ceramic (LTCC) based System-in-Package (SiP) technology [1]. 60GHz antenna designs are also shifting from conventional discrete designs to Antenna-in-Package solutions [2,3]. In this paper we present two antennas for 60GHz radios in Ferro A6 LTCC package with a relative dielectric constant of εr = 5.9. The two antennas are fed by stripline (SL) structures. This makes the antenna performance less sensitive to the surrounding package- and PCB-level dielectric and metal layers. These structures also decouple the design of the antenna from the exact physical properties of the package, simplifying simulation and modeling complexity. The two antennas have different polarization characteristics. One antenna is circularly polarized (CP), which is realized by an aperture-coupled 2×4 patch array with a sequential rotation scheme. With this scheme, wide axial ratio (AR) and impedance bandwidth are achieved. The other antenna is linearly polarized (LP), which is realized by a grid array antenna. This type of antenna is particularly suitable for fabrication in LTCC with rectangular meshes of microstrip lines for radiation. It also avoids the complicated feeding network associated with the commonly used patch array antenna. In view of wireless access applications, the CP property is very desirable for 60GHz antennas [4]. This is because the LP antenna requires the transmitting and receiving antenna to be rotated properly to achieve polarization matching. Using the CP antenna, this problem can be eliminated. In this paper, we not only present the design of two antennas but also the measurement to show the wireless access advantage of the CP patch array over the LP grid array antenna.

A proximity-coupled circularly polarized slotted-circular patch antenna for RF energy harvesting applications

A proximity-coupled (electromagnetic coupling feed) circularly polarized slotted-circular microstrip antenna is proposed for RF energy harvesting applications. The antenna consists of an asymmetric-slotted-circular-patch radiator with a proximity-coupled feed. Two asymmetric-circular slots are cut diagonally onto a circular-patch antenna to generate two orthogonal modes with a 90° phase-shift for requirements of circularly polarized radiation. The proposed designed antenna is achieved gain of more than 6.0 dBic across the 3-dB axial ratio (AR) bandwidth (2.36 GHz–2.40 GHz). An overall antenna volume is 60 mm × 60 mm × 3.2 mm.

Overview of antennas for RF energy harvesting

In this paper, an overview of the antennas for RF energy harvesting is presented. The specifications for these antennas such as low profile, lightweight, compact size, polarization multiband and planar structure characteristics are also discussed. In addition, the recent related work of our group is also included.