Abstract

Ϫ48.3 and Ϫ40.94 dB, respectively. The RF input return loss shown in Figure 6 is better than 25 dB in the 5.725-5.825-GHz received band, which clearly shows the 50⍀ characteristic during application. Plotted in Figure 7 are the measured results of the intermodulation products in a two-tone test, showing IIP3 of Ϫ9.5 dBm. Figure 8(a) shows the corresponding double-sided band NF and conversion gain revealed for the 5.8-GHz-band operation are 4.15 and 34.61 dB, respectively, under Ϫ4 dBm of LO conversion gain. NF with wide IF-frequency is shown in Figure 8(b). CONCLUSIONA new on-chip balun has been designed and successfully applied to the subcircuit design of a receiver. Wide bandwidth with small amplitude error is obtained due to the use of a fully symmetric layout and the same common virtual ground. Further, this paper has also shown how to merge a single-ended LNA and doublebalanced mixer with the on-chip balun in order to realize remarkable performance with low-power dissipation. This balun will be quite useful for applications in wireless communication systems.ABSTRACT: An experimental study of a planar microwave imaging system with step-frequency synthesized pulse for possible use in medical applications is described. Simple phantoms, consisting of a cylindrical plastic container with air or oil imitating fatty tissues and small highly reflective objects emulating tumors, are scanned with a probe antenna over a planar surface in the X-band. Different calibration schemes are considered for successful detection of these objects. Figure 8 Measured conversion gain and NF for LNA-Mixer: (a) sweep RF frequency; (b) sweep IF frequencyABSTRACT: A novel NRZ-to-PRZ converter consisting of an SOA and an AWG is proposed. The parameters are investigated through numerical analysis to optimize its performance. In the experiments, all-optical clock recovery from NRZ data and NRZ-to-RZ format conversion are successfully demonstrated at 10 Gb/s, which further proves that the proposed scheme is applicable.

The design of ultra-wideband vias and power dividers in microstrip-slot technology is presented. The devices employ two substrates supported by a common ground plane. Their design is accomplished with the use of commercially available full EM analysis and design software. Low insertion loss and good return loss performances over an ultra wide frequency band for the designed structures are noted.

Abstract-The design of compact wideband microwave reflectometers for the purpose of inclusion in a breast cancer detection system is presented. In this system, a wideband frequency source is used to synthesize a narrow pulse via the step-frequency synthesis method. The reflectometer undertakes measurements in the frequency domain and the collected data is transformed to the time/space domain using IFFT. In order to accomplish reflection coefficient measurements over a large frequency band, compact wideband couplers and power dividers are used to form the reflectometer. Two compact six-port reflectometer configurations are investigated. One uses the Lange coupler and the Gysel power divider and the other one employs a 3dB slot-coupled microstrip coupler and a 2-stage Wilkinson power divider. The reflectometer employing the slot-coupled coupler and the Wilkinson divider provides a wider operational bandwidth, as shown by simulation results performed with Agilent ADS.

This article describes an ultra wideband (UWB) microwave system that uses the frequency-domain reflection coefficient data acquired by a UWB antenna to form a microwave image of a homogenous cylindrical dielectric body containing cylindrical targets. Both hardware and signal processing aspects of the system are described. The system uses a frequency-domain image reconstruction algorithm using the different data obtained for adjacent positions of the scanning antenna so that the effect of air-image body interface is removed. The algorithm is tested in examples of a cylindrical dielectric container including a vegetable oil and targets in the form of smalldiameter plastic straws filled with water. Both simulated and measured results are presented. The successful detection and location of the targets is achieved by visual inspection of the formed microwave images. V C 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54: [13][14][15][16][17][18] 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26465Key words: microwave radar; microwave antenna; ultra wideband INTRODUCTIONRecent years have shown an increased interest in using active microwave techniques to obtain internal images of various dielectric objects. A prominent example is the ground penetration radar to detect and locate voids, pipes, and other objects buried underground, and its recent extension, the ''breast radar'' for detection of a tumor in the woman's breast [1][2][3][4][5].There have been two major approaches to see the inside of a dielectric body using active microwave techniques. One of the approaches uses the so-called inverse scattering technique using a single or multiple frequency signal data acquired by antennas surrounding an imaged body [1,[6][7][8][9]]. An alternative is an ultra wideband (UWB) radar approach using short duration pulses, which are transmitted and received by UWB antennas [1][2][3][4][5]. The two approaches encounter different challenges concerning hardware implementation and image reconstruction. Both face the same trade-off between penetration and in-depth resolution, with high microwave frequencies offering high resolution images but small penetration, and low microwave frequencies providing large penetration but poor resolution. The inverse scattering approach does not require any a priori information to produce the complex dielectric constant distribution of an imaged object as it solves the problem by comparing the data obtained from a forward full electromagnetic (EM) solution with the measured data. However, it needs a considerable effort to overcome challenges of an ill-posed nonlinear problem. The UWB radar approach does not offer an exact EM image reconstruction as it looks for locations of an increased scatter inside an image body. It requires an estimate of average dielectric properties of the body to produce a spatial scatter map. Its main dare comes from a large magnitude signal caused by reflections at the body interface that masks small return signals of internal targ...