Branka Jokanovic

Review of printed Marchand and double Y baluns: characteristics and application

A review of printed baluns is presented. This is divided into two main groups; Marchand baluns (band pass networks) and double Y baluns (all pass networks). For each of these groups of baluns, three different realizations are given: microstrip-slot line, CPW-slot line and CPW/sub FGP/-CPS and their theoretical and experimental characteristics are compared. Simple expressions for the design of Marchand baluns with Chebyshev response, which replace the complicated synthesis proposed by Cloete are derived. Superior broadbandwidth features of double Y baluns are demonstrated in the design of two uniplanar double balanced mixers. Both the double Y mixer and the CPW/sub FGP/-CPS mixer have a frequency bandwidth 1:6, whilst maintaining other performance similar to that achieved with classical double balanced mixers. >

Fractal Geometries of Complementary Split-Ring Resonators

Complementary split-ring resonators (CSRRs) are typically used as negative-permittivity particles in microstrip left-handed structures. In this paper, novel CSRRs that use a square Sierpinski fractal curve are proposed and studied in detail. It is shown that the application of fractal geometries results in significant miniaturization of the metamaterial unit cell in comparison with conventional and equivalent meander structures. Multiple fractal CSRRs are also analyzed. The influence of different geometrical parameters and the order of the fractal curve on the performances are investigated, as well as the efficiency of excitation of the particles. When used in the design of left-handed transmission lines, fractal complementary split rings improve frequency selectivity in the upper transition band when compared to other nonfractal topologies.

Filter Parameter Extraction for Triple-Band Composite Split-Ring Resonators and Filters

A configuration of composite resonators consisting of three split-ring resonators is proposed to obtain a triple-band response with two transmission zeros between the passbands. Two new topologies are presented to design triple-band filters with controllable responses. A systematic filter design approach is presented based on a filter coupling model. The model is established to enable triple-band filter design with controlled passbands. Two methods are proposed and compared for the extraction of filter parameters. Coupling between nonadjacent elements is considered in the model and shown to have a significant effect. By changing the orientation of the coupled composite resonators, it is possible to introduce additional transmission zeros. Two sixth-order filter examples illustrate the use of the coupling model with the filter design approach to design filters with specified responses. The limitations of this filter topology are discussed.

Complementary Split Ring Resonators Using Square Sierpinski Fractal Curves

Split ring resonators and complementary split ring resonators are used in a left-handed media to obtain negative values of permeability and permittivity, respectively. In this paper, novel split ring geometry using square Sierpinski fractal curves is proposed, that reduces resonant frequency of the structure and achieves improved frequency selectivity in the upper transition band. In order to validate the results, left-handed microstrip line that uses square Sierpinski complementary split ring resonators is designed, fabricated and measured

Heart Rate Variability Assessment Using Doppler Radar with Linear Demodulation

Heart rate variability (HRV) describes the time variation in beat-to-beat interval, and reflects the manner in which the cardiovascular regulatory system responds to demands, stress, and illness. A particular advantage of Doppler radar for HRV monitoring is the ability to detect and monitor heart and respiration signals simultaneously, and thus provide independent measures of HRV, and respiration-related fluctuations. High accuracy in obtaining HRV parameters using Doppler radar is achieved using linear demodulation method, including SDNN of about 10 ms, and mean beat to beat interval accuracy of close to 1 ms. In addition, respiration signals were obtained simultaneously with the heart signals, clearly showing a correlation between respiration cycles and heart rate variability.

Enhanced Modelling of Split-Ring Resonators Couplings in Printed Circuits

An enhanced equivalent circuit approach for the magnetic/electric interaction of single split-ring resonators (SRRs) with printed lines is presented in this paper. A very simple and efficient lumped-element network is proposed to model the behavior of metamaterial-based printed lines over a wide frequency band. The same circuit topology can be used for the single- and two-mirrored SRRs loaded microstrip line. The corresponding circuit parameters are obtained from the multiconductor transmission line theory as well as from closed-form expressions that make use of just the resonance frequency and minimum of the reflection coefficient (which should be previously extracted from experiments or full-wave simulations). The comparison of our equivalent circuit results with measurements and full-wave simulations has shown a very good agreement in a considerably wider frequency band than other previously proposed simple equivalent circuits.

Effective Electromagnetic Parameters of Metamaterial Transmission Line Loaded With Asymmetric Unit Cells

In this paper, we propose the generalized extraction procedure for retrieval of the effective constitutive parameters for a metamaterial transmission line loaded with asymmetric unit cells. The asymmetric unit cell is replaced with a transmission line immersed in equivalent bianisotropic medium described by effective parameters ε, μ, and Zc, and bianisotropic parameters u and η. The proposed retrieval procedure is applied to novel dual-band unit cells and compared with the standard Nicolson-Ross-Weir (NRW) method that is originally developed for the symmetric unit cell and then extended to the asymmetric one using the averaged value of reflection coefficients. It has been shown that, in case of pronounced asymmetry, the NRW method gives only the exact value of refraction, but effective permittivity and permeability are considerably different from the exact values since they are calculated by means of the approximate value of characteristic impedance.

Direct QPSK modulator for point-to-point radio link at 23 GHz

The design and characteristics of a simple direct QPSK modulator for a terrestrial point-to-point radio link is presented. This modulator enables a compact, low cost and high efficiency transmitter. Good sideband suppression, greater then 25 dB is obtained in the frequency range 21.0 to 24.0 GHz, without tuning. The insertion loss is less than 8 dB in 3 GHz bandwidth and the carrier suppression is about 22 dB.

High gain printed antenna array for FMCW radar at 17 GHz

We are presenting the design of a high gain printed antenna array consisting of 420 identical patch antennas intended for FMCW radar at Ku band. The array exhibits 3 dB-beamwidths of 2° and 10° in H and E plane, respectively, side lobe suppression better than 20 dB, gain about 30 dBi and VSWR less than 2 in the frequency range 17.1 - 17.6 GHz. Excellent antenna efficiency that is between 60 and 70 % is achieved by proper impedance matching throughout the array and by using series feeding architecture with both resonant and traveling-wave feed. Enhanced cross polarization suppression is obtained by anti-phase feeding of the upper and the lower halves of the antenna. Overall antenna dimensions are 31 λ0 × 7.5 λ0.

Heartbeat interval extraction using doppler radar for health monitoring

In this paper heartbeat interval extraction methods using Doppler radar are reviewed. While single channel CW radar offers simple architecture and signal processing, this method is very sensitive to subject position and may result in rate doubling, or the coupling between heart and respiratory rates. Quadrature radio architecture is used to overcome this limitation. The use of linear and non-linear demodulation methods was explored for heartbeat interval extraction.