This paper presents a new behavioural mixer model in a multi-box structure. In the proposed model, as well as amplitude and phase nonlinearity, the memory effect is also modelled. The multi-box structure is constructed in line with the Hammerstein model to characterise both fundamental signals, intermodulation distortion (IMD) and harmonic distortion (HD) for mixers in particular and all frequency translating devices in general. A testbed is constructed to measure both amplitude and phase characteristics. A good match between the measured and the calculated results is obtained using curve fitting and optimisation algorithms. In order to model the memory effect, a finite impulse response (FIR) filter is used. The measured IM3 imbalance is successfully modelled with this filter. For fundamental components, amplitude and phase errors are less than 0.1 dB and 1 degree, respectively. For IM3 components, amplitude and phase errors are less than 4 dB and 10 degrees, respectively. For the overall accuracy of the model, measurements are conducted with two-tone and modulated signals, and normalised mean square error (NMSE) values are calculated as -31.5 dB and -29.3 dB, respectively. The results are obtained for a wide range of input power span, including the compression region where nonlinearity is strongly pronounced. The proposed model is capable of accurately representing nonlinearity and memory effect for mixers and frequency translating devices in general and thus may be used for system-level modelling and linearisation applications.

This paper presents a comprehensive analysis of a tunable impedance matching network that offers continuous Smith-chart coverage between 1.2-2.7 GHz. High and low frequency characteristics of the hyperabrupt varactors utilized in the network are experimentally measured and presented. By carefully considering the characteristics of these tuning elements and optimizing the design parameters accordingly, the proposed tunable impedance matching network demonstrates superior frequency tunable bandwidth, insertion loss, and noise figure compared to existing approaches. The tunable matching network exhibits less than 1 dB of insertion loss, 0.4 dB of noise figure, and a Q factor exceeding 26 under different reverse bias conditions operating within the frequency tunable band. The 1-dB compression point is observed at an input power of 23 dBm, while the third-order intermodulation intercept point is determined to be 25.66 dBm.

This work proposes a broadband, diamond-shaped, frequency tunable and unique metamaterial resonator design featuring a ground frame and a feedline. Integration of varactor diodes to the design coupled with carefully engineered electric and magnetic field distributions of the resonator enable high frequency tunability as demonstrated by simulations and measurements. Furthermore, the proposed design enables the simpler measurements of the metamaterial resonator without the need for plane wave illuminations or additional waveguides. Measurements show a tunable frequency range over 0.82-2.04 GHz, which corresponds to 85.3% tunable bandwidth percentage with an almost constant Q-factor. Measured maximum insertion loss is 1.68 dB over this tunable band. Results indicate much better tunable bandwidth compared to similar works. Metamaterial properties are also demonstrated with permeability, permittivity, and transmission phase results. The designed tunable metamaterial resonator may be used to realize reconfigurable microwave circuits such as filters, antennas, sensors, absorbers, switches, and matching networks.

In this paper, a new behavioural mixer model is introduced. In addition to amplitude nonlinearity; phase nonlinearity and memory effect of the mixer are modelled in a multi-box structure. Each nonlinearity source is modelled in distinct blocks of which cascade connections compose the behavioural mixer model. A test-bed has been constructed including a reference mixer and through measurements, amplitude and phase characteristics of the main tones and IMD products are modelled. The proposed behavioural model delivers a good match between measured and simulation results. The mixer model may be curve fitted to the characteristics of any mixer by optimizing its variable parameters and thus can be used in modelling different types of mixers. Thus, the proposed mixer model may be used in computer simulation tools and in linearization applications.

The need of this era is a fully automated vehicle parking system using IOT. The real time notification is made possible by integrating a Micro-controller (Arduino) with a wireless communication system (ZigBee) and is feed to the driver via a smart phone. This technique provides a time and energy efficient way to communicate information between sender and receiver. Additionally, this efficient system provides a better monitoring and control application for shopping malls, restaurants, offices and hospitals. In severe cases, this system will also update crowd capacity information to ambulance service, so that they could easily tackle the situation by adopting the less crowded area towards hospital. The comparison between experimental results of ZigBee with other popular wireless technologies such as Wi-Fi and Bluetooth show that it is more energy efficient. GSM module notifies the driver about the current location of empty parking spaces via SMS or software application. The IR sensors embedded in the parking lots provide the real time scenario to user with all possible details and allowing the easy access to parking lots available, ensuring minimal human interaction.

Human heart cardiac muscles activities can be represented graphically using electrical impulses. Electrocardiography (ECG) signals are very important for physicians to diagnose heart disease. In this study, Bluetooth device is used to transmit data wirelessly. For this purpose, the generated signal from heart beat sensor is analyzed in MATLAB using Support Vector Machine (SVM) and Discrete Wavelet Transform (DWT) techniques. ECG Simulator compares the actual signal of infants with the reference signal and notify the physician about healthy or unhealthy ECG signals. Additionally, simulating the ECG pattern of different infants before designing and developing any biomedical technology is quite efficient and cost-effective.

Reports on the status of microwave education and technological development in Turkey.

This article examines a wideband impedance transformer based on a split ring resonator and defected ground structures. The transformer was designed as a 4section binomial one and it provides a transformation from 50 Ω to 100 Ω. Reversed Z” shaped defects are formed on the ground plane of the design in order to increase the bandwidth. The design has been simulated using a 3D electromagnetic simulator which utilizes finite integration technique. Three distinct resonances are exhibited at specific frequency spots as proofs of the concept of impedance matching. Theoretical and simulated results are in a good agreement with each other and the proposed design might be tailored in many microwave circuits and antenna applications.

Bone fracture is a common problem in daily life which occurs when high pressure is applied on bone or by simple accident and also due to osteoporosis and bone cancer. Different techniques are used today to detect bone fractures such as X-Ray, Computed Tomography (CT-scan), Magnetic Resonance Imaging (MRI) and Ultrasound. Among these four modalities, X-ray diagnosis is commonly used for fracture detection. However, if the fracture is complicated, a CT scan or MRI may be needed for further diagnosis and operation. In this paper, it is intended to make a low-cost portable device for bone fracture detection of patients, having age between 15 to 45 years using sound waves generated by the vibrator of a mobile phone. FFT technique in MATLAB was applied to the generated sound waves to examine the difference between cracked and healthy bone by applying 200 Hz of the sampling frequency. The device will be useful for doctors and public alike since it is portable, practical, mobile and affordable. It must be noted that the proposed device is not intended for a replacement of standard methodologies like X-Ray but rather will serve to be used as an initial detection phase. It is hoped that a negative scan of this device will discount the need for the more costly and timeconsuming X-Ray procedure.

An analogue predistorter using a distortion generator based on a two-stage radio frequency mixer topology is presented. The proposed distortion generator achieves fundamental signal cancellation without using a signal cancellation loop or a resonant circuit, thus it generates an error signal that predominantly consists of unwanted intermodulation distortion (IMD). Measurements are performed using multi-tones, WLAN- and Terrestrial Trunked Radio (TETRA)-modulated signals. Distortion generator provides high levels of IMD and achieves more than 40 dB fundamental signal cancellation across a bandwidth of 120MHz. A proof-of-concept predistorter was constructed to validate the usefulness of the proposed distortion generator, which achieves up to 15 dB suppression of IMD and adjacent channel power ratio at the output of a power amplifier. Distortion generator and predistorter gave similar results at multiple frequencies between 920MHz and 2 GHz, with different test signals having bandwidths ranging from 25 kHz to 120MHz.

In this work, a different approach to achieve a desired characteristic impedance value on microstrips is presented. In standard microwave circuits using microstrip lines, the dielectric thickness is same and uniform across the whole circuit. In this paper, it is proposed to modify the dielectric thickness to achieve a certain design goal by creating variations in the characteristic impedance of the microstrip transmission line without changing the width of the line. The proposed approach is applied to a multi-section quarter wave impedance transformer. Simulation and measured results demonstrate the potential of the defected dielectric approach by achieving a much wider bandwidth than a conventional multisection impedance transformer. The proposed idea can be expanded and applied to other microstrip based microwave circuits such as filters, power dividers, hybrid couplers, matching networks, etc.

In this paper, a Frequency Modulated Continuous Wave Radar is built using radio frequency techniques. Radar can measure the nearest object's range from 2 to 30 meters with 1-meter range resolution. The design process was carried out by using computer-aided design techniques, and mathematical tools. The hardware prototype was built and measurements were carried out confirming successful operation of the range detection radar.

This paper represents the design of a microstrip patch antenna which is reconfigurable by means of the effect of a pixel grid overlay that is placed at a certain distance from the antenna. In addition to beam steering capability, this article will focus on several important parameters of the aforementioned antenna, such as, the directivity, the gain, radiation pattern and polarization. The antenna consists three main parts; a rectangular microstrip patch antenna that has the operating frequency at around 2.4 GHz, a medium that keeps antenna apart from the pixel grid overlay on distance of coupling and the pixel grid overlay itself. The objective is to design a smart and compact antenna with beam steering capability to improve the power efficiency of transceivers used in WLAN, WiFi and wiles sensor networks. The medium is adjusted to keep two adjacent layers on the coupling distance. The pixel grid overlay is formed by 31 pieces of a hexagonally shaped copper patch grid, each patch on the grid is arranged to be at coupling distance with neighboring patches as well. Besides being cost-effective, practical to apply and easy to produce, the parasitic-layer, has the advantage of ensuring the beam steering ability of the device. It has been also observed to increase the gain of the antenna and affect the radiation pattern.

In this paper, a broadband rectenna for radio frequency (RF) energy harvesting is presented. The proposed rectenna consists of a broadband fractal slot antenna and a voltage doubler rectifier circuit with a novel matching network. First of all, a broadband fractal antenna is proposed, which covers the most frequently encountered frequency bands which are located around 1800 MHz, 2.1 GHz, 2.4 GHz, and 2.45 GHz corresponding to the standards like GSM, UMTS, ISM, and WLAN, respectively. The return loss of the proposed antenna is below -10 dB over the desired frequency bands of the interests. Secondly, a novel dual-band impedance matching technique is employed to a voltage doubler rectifier circuit in order to enhance RF-to-DC conversion efficiency which reaches 45% and up to 72.2% when the input power to the rectifier is -10 dBm and 4 dBm, respectively. Finally, it has been demonstrated that the proposed rectenna is able to harvest RF energy from both GSM-1800 and wireless LAN/Wi-Fi bands. It could be utilized to powerup low-power sensor platforms.

Microwave energy harvesting has the potential to power low powered electronic micro systems. Here we propose a fractal antenna topology that may be used for the conversion of microwave energy into usable DC power. The design of a broadband antenna that uses fractal approach is investigated. Simulation results demonstrate that improvements may be obtained in bandwidth and gain characteristics of planar antennas by using fractal approach.

The following topics are dealt with: antenna radiation patterns; UHF antennas; permittivity; microwave antennas; microstrip antennas; antenna feeds; calibration; wireless LAN; energy harvesting; electromagnetic wave scattering.

A frequency tunable resonator topology is proposed that consists of an S-shaped resonator, a ground frame and a feeding transmission line. Tunability is achieved by using reverse biased varactor diodes employed at critical locations on the structure. As well as being a tunable resonator, the structure also provides tunable metamaterial properties. Reflection and transmission parameters, electric and magnetic field distributions, and permittivity and permeability at each tuned frequency were analyzed and shown. Simulation and measured results agree well and demonstrate about 28% frequency tunability.

In this article, impedance transformers and branch line hybrids are selected to demonstrate the impact of defected ground structures on the operational bandwidth of microwave circuits. Three different branch line hybrids are studied with simulations and laboratory measurements, these are; a standard branch line hybrid, one using tapered lines and another one using both tapered lines and DGS. Based on these results, an optimum design in terms of location, size and number of DGS was proposed to achieve the widest operational bandwidth. Simulation and measured results demonstrate that correct usage of DGS and tapered lines can enhance the bandwidth of a narrowband microwave circuit. (c) 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:311-316, 2016.