Philippe Pouliguen

Circularly Polarized Transmitarray With Sequential Rotation in Ka-Band

We present here the design and demonstration of a circularly polarized (CP) transmitarray antenna operating in Ka-band and illuminated by a linearly polarized (LP) source. The proposed design is based on a CP unit-cell with simulated insertion loss of 0.2 dB at 30 GHz. In order to improve the axial ratio (AR) bandwidth, the sequential rotation technique is applied to the full array configuration. A model based on a hybrid in-house simulation tool is also proposed to predict accurately the array performance. The realized prototype, formed by 400 unit-cells, has 1 bit of phase resolution. The measured broadside gain is 22.8 dBi at 30 GHz with a 3-dB bandwidth of 20% in right-handed CP (RHCP). The obtained 3-dB AR bandwidth of 24.4% is comparable with higher resolution designs.

Focal Distance Reduction of Transmit-Array Antennas Using Multiple Feeds

The reduction of the focal distance of transmit-array antennas using multiple feeds is investigated theoretically and through full-wave simulations. A theoretical model of multiple-feed transmit arrays is derived using analytic formulas; it shows that the focal distance can be divided by a factor of two using a quadruple-feed configuration. The theoretical results are validated through full-wave simulations for two transmit arrays operating in the 60-GHz band.

1-Bit Reconfigurable Unit Cell for Ka-Band Transmitarrays

This letter presents an electronically reconfigurable, linearly polarized unit cell for transmitarray applications in Ka-band. A 1-bit phase resolution (namely with two phase states 0 ° and 180 °) is obtained using two p-i-n diodes mounted on a slot-loaded patch antenna. The design, realization, and experimental characterization in a standard waveguide simulator are reported. The measured insertion losses only reach 1.09 and 1.29 dB for the two-phase states, respectively, with a 3-dB transmission bandwidth of about 11.2%.

Analytical Formulae for Radar Cross Section of Flat Plates in Near Field and Normal Incidence

Radar Cross Section is most of the time defined in far field. In that case, RCS is totally independent of the range between the radar and the target. However, in several kinds of military scenario, it can be more realistic to deal with the target nearfield scattering characteristics. Using a relation to define near-field RCS, this communication proposes simple and approximated analytical formulas to express monostatic near-field RCS of perfectly conducting flat targets observed in normal incidence. † Also with IREENA, Polytech’Nantes, La Chantrerie, rue C. Pauc, 44306 Nantes cedex 3, France. 264 Pouliguen et al.

RCS computation in near field

This communication presents a physical optics based method developed by CELAR to calculate radar cross section (RCS) in function of the distance separating the target and the radar system. Initially this method has been developed to calculate RCS in the same geometrical configurations than the measurements performed in the CELAR facilities. So, after a short presentation of RCS measurement facilities of CELAR, this paper will expose the method developed to calculate near field RCS. Comparisons between measurements and calculations will be shown to validate the method. Then, some applications will be given on canonical and complex targets. For flat circular and square plates, particular phenomena will be detailed and some analytical approximated formula will be proposed to express their monostatic specular RCS

A Conical Patch Antenna Array for Agile Point-to-Point Communications in the 5.2-GHz Band

We study here a 12-element conical antenna array made of four linear subarrays angularly spaced by 90 ° and with three probe-fed radiating elements per subarray. A prototype has been designed and manufactured. The measured radiation characteristics of the elementary radiating element (active pattern) and of the subarray are found in good agreement with the simulation results. The proposed array configuration is considered as a promising solution to rotate and steer the antenna beam for ensuring point-to-point communication at 5.2 GHz.

RCS OF LARGE BENT WAVEGUIDE DUCTS FROM A MODAL ANALYSIS COMBINED WITH THE KIRCHHOFF APPROXIMATION

In this paper, we present a fast method to predict the monostatic Radar Cross Section (RCS) in high-frequency of a cavity, which can be modeled as a succession of bent waveguides of the same cross section and stuffed by a perfectly-conducting termination. Based on a modal analysis combined with the Kirchhoff Approximation, this method allows us to obtain closed-form expressions of the transmission matrix at each discontinuity. In addition, to improve the efficiency, a selective modal scheme is proposed, which selects only the propagating modes contributing to the scattering. Compared to the Iterated Physical Optics (IPO) method and the Multi-Level Fast Multipole Method (MLFMM, generated from the commercial software FEKO), this approach brings good results for cavities with small tilt angles of the bends, typically smaller than 2 degrees.

Comparison between Matrix Pencil and Prony methods applied on noisy antenna responses

A comparison between the TLS-Prony and the TLS-Matrix Pencil methods applied on antenna backscattered responses in presence of noise is presented. This work focuses on errors on the poles extracted when the SNR of the signal becomes low. Algorithms of the two methods are quickly described. The two algorithms are applied on the backscattered responses of a dipole and an UWB antenna. The TLS-Matrix Pencil method is less sensitive to noise and especially for damping coefficient extraction.

1-bit reconfigurable unit-cell for transmit-array applications in X-band

This paper presents an electronically reconfigurable 1-bit phase quantization (0°/180°) unit-cell for transmit-array applications at 10 GHz. The unit-cell consists of a single ground plane, two identical substrates, two rectangular slot-loaded patch antennas connected by a metallized via hole. Reconfiguration is obtained by two PIN diode switches located in the slot of the top patch. A prototype has been manufactured and measured in a dedicated waveguide simulator. The experimental results are in very good agreement with full-wave simulations and confirm the operating principle of the proposed design.

3-D Shaping of a Focused Aperture in the Near Field

The manipulation of the near-field (NF) is a challenging topic in electromagnetics, carrying essential importance for several applications. In this paper, we develop an algorithm capable of shaping the NF in 3-D domains according to given specifications. The algorithm is based on a set theoretic approach and a front-and-back iterative propagation scheme. The latter is realized using fast Fourier transforms (FFT), reducing the required computational time. The algorithm is applied on a focal shaping scenario. In this case, a full control of the depth of focus, spot diameter, and sidelobe level of the generated radiation is achieved. In particular, the proposed procedure is successfully adopted to control the normal component of a radiating aperture over a range of 12λ at 30 GHz. The derived aperture field distribution is then synthesized by a radial line slot antenna (RLSA) by means of an in-house method of moments (MoM) code. NF measurements have validated the proposed approach and prototype.