Dual Port Antenna Combining Sensing and Communication Tasks for Cognitive Radio

Dynamic spectrum access has been proposed asthe effective solution to overcome the spectrum scarcity issue,supported by cognitive radio technology. Sensing and communicationfunctions are both the most important tasks in cognitiveradio systems. In this paper, an antenna system combiningsensing and communication tasks is proposed to be integratedinto cognitive radio front-ends. Sensing task is performed bythe means of an ultra-wideband quasi-omnidirectional antenna.Whilst the communication task is ensured by using a narrowbandantenna. Both antennas have been designed on the same layer ofa FR4 substrate, for manufacturing cost constraint. Therefore,the isolation between them must take into consideration. Themeasured mutual coupling of less than -18dB is achieved overthe whole impedance bandwidth. The proposed sensing antennacovers a wide range frequency bands ranging from 2 to 5.5GHz.While the communication antenna operates at 2.8GHz, and byadding inductors to the antenna, the resonant frequency canbe tuned from 2.6 to 2.7GHz. The whole antenna system wasdesigned, fabricated, and tested. Measurement and simulationresults prove the feasibility of the proposed structure for cognitiveradio applications

Ultra-broadband high efficiency mode converter

In this paper we develop a small-sized mode converter with high performance, high conversion efficiency and instantaneous bandwidth as high as 55%. This mode converter transforms energy from the TM01 first high-order mode towards the fundamental TE11 circular waveguide mode. The proposed structure increases the free spurious operating bandwidth in comparison with the existing results in literature. An X/Ku-bands experiment prototype unit was designed, ensuring practical return losses better than 28 dB and insertion losses less than 0.1 dB (conversion efficiency > 98.8%) within the entire frequency bandwidth ranging from 9.25 GHz to 16.25 GHz. The presented architecture offers useful features such as very wide bandwidth, small size, easy achievement as well as excellent performance, which makes it very suitable for High-power microwave (HPM) sources that generate the TM01 circular waveguide mode. In these cases the TE11 mode is needed since it has a convergent radiation pattern able to drive conventional antennas. Moreover, this compact concept is fully scalable to any millimeter frequency band

An accurate method to estimate complex permittivity of dielectric materials at X-band frequencies

In this paper, a measurement method is presented to estimate the complex permittivity of a dielectric material even if its length is higher than the half wavelength in the waveguide. The Sij-parameters at reference planes in the rectangular waveguide loaded by material sample are measured by Network Analyzer. First of all, the expression of the complex permittivity as a function of Sij-parameters are calculated by applying the transmission lines theory. Further, a comparison of the estimated values of the complex permittivity obtained from the presented method and the Nicholson-Ross method is presented. Finally, the results for complex permittivity of Teflon, Nylon and Verde measured at the X-band frequencies are presented

A dual band orthomode transducer in K/Ka bands for satellite communications applications

This article presents the design, simulation and machining of a dual Orthomode Transducer for feeding antenna using waveguide technology. Linear orthogonal polarizations in common port are separated to single linear polarizations in other ports. This device is developed to work in K and Ka bands and could be exploited in satellite communications applications. Also, it is designed to provide good scattering parameters results experienced with simulation tools and real load laboratory measurement. The designed circuit exhibits important results with return losses less than 25 dB, insertion losses in theory of about 0.05 dB as well as a good isolation of 40 dB in both frequency bands of interest (19.4 GHz-21.8 GHz) and (27 GHz-32 GHz)

New FDTD method to estimate the dielectric constant and loss tangent of a bilayer dielectric material at x-band frequencies

In this paper, a new iterative method is presented to estimate the dielectric constant and loss tangent for each layer in a Bi-layer dielectric material using an X-band short-circuited rectangular waveguide WR90. The S11-parameter at the reference plane as a function of dielectric constant and loss tangent of each layer is calculated by applying the two-dimensional finite difference in time-domain method (2DFDTD) for the wave equation. Then, the Nelder-Mead algorithm is applied to estimate the dielectric constant and the loss tangent by matching the measured and calculated S11-parameter. This method has been validated on three bi-layer dielectric materials such as Teflon-FR4 Epoxy and FR4 Epoxy-Plexiglas and Plexiglas-Teflon. A comparison of estimated values of the dielectric constant and loss tangent obtained from FDTD-2D Maxwell's equations measurements and 2D-FDTD Wave equation measurements is presented. Remarkably, this method reduces the execution time by a factor of five while maintaining equal precision

Characterization of magneto-dielectric materials by a rectangular waveguide using the 2D-FDTD method

In this paper, a new measurement method is proposed to estimate simultaneously the complex permittivity and the complex permeability for a magneto-dielectric sample using a X-band rectangular waveguide WR90. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a material sample are measured as a function of frequency using the E8634A Vector Network Analyzer. Also, by applying the two-dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity and complex permeability are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity and complex permeability by matching the measured and calculated Sij-parameters. This method has been validated by estimating, at the X-band, the complex permittivity and complex permeability of two materials such as FR4 Epoxy and Titanium Carbide powder (TiC)

Complex permittivity estimation for each layer in a bi-layer dielectric material at Ku-band frequencies

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a bi-layer dielectric material using a Ku-band rectangular waveguide WR62. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a bi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the transmission lines theory, the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated the Sij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from bi-layer measurements and mono-layer measurements is presented

Calculating the SAR distribution in two human head models exposed to printed antenna with coupling feed for GSM/UMTS/LTE/WLAN operation in the mobile phone

The scope of this paper is to examine the Specific Absorption Rate (SAR) inside the human head model exposed to the radiation of a low-profile printed monopole antenna with coupling feed for GSM/UMTS/LTE/WLAN operation in the slim mobile phone. The presented antenna operates for most of the mobile phone applications such as the GSM850, GSM900, GSM1900, UMTS2100, LTE2300, LTE2500 and WLAN2400 bands. In this study, two different human head models are used: homogenous spherical head and spherical seven layer model. In addition, the effects of operating frequency and the gap distance between the mobile phone antenna and the human head model on distributions of the SAR within the human head are analyzed. All the simulations are done for three different distances between the antenna and the head model (5 mm, 10 mm, 20 mm). Furthermore, the SAR levels for the head tissues are calculated for and with accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP). All numerical simulations are performed using the Ansoft HFSS Software and CST Microwave Studio

2D-FDTD method to estimate the complex permittivity of a multilayer dielectric materials at Ku-band frequencies

In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a multi-layer dielectric material using a Ku-band rectangular waveguide WR62. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a multi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the two dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated Sij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer and one tri-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from multi-layer measurements and mono-layer measurements is presented