An equivalent waveguide approach to designing of reflect arrays with the use of variable‐size microstrip patches

Abstract

tional plane Figure 7(b) indicates diminishing pattern change directionality with increased board length. As board length increases, overall pattern differences addressed in Figure 8(a) decrease in the azimuthal plane.Although co-polarized pattern components are the focus of this work, cross-polarized components add insight to the pattern-difference dependence upon antenna geometry. For the two boards having 39-and 47-mm lengths and 79-mm width, the viewpoint inclusive of both polarizations reveals another aspect of handsetfeed interaction. The increased cross-polarized magnitude [see Figure 7(a)}, through the associated change in polarization state, indicates physical re-distribution of current on the ground plane. DISCUSSIONAntenna impedance sensitivity to board geometry was demonstrated through results presented for two handset designs. For electrically smaller handsets significant response changes between measurements including either the sleeve or regular transmission line devices in the RF feed were observed. The offset between the designed and measured operating band comprises a related effect. If the antenna-handset radiator is idealized to be a half-wave dipole, calculations showed plausibility of a resonance shift from the intended 1.9-GHz operating frequency to 1.75 GHz. Because the system consists of conductors of dissimilar geometry, length compensation techniques were not employed during design. Uncertainties introduced by application of the dipole analogy to an asymmetric antenna prompted dimension choices referenced to free-space wavelength. The match observed at 1.6 GHz suggests that designers should account for board size while tailoring the antenna impedance.Pattern difference mean and standard deviation were utilized to quantify pattern effects introduced by feed-line radiation. The statistical parameters help to contrast measurements of an isolated handset with those that include detrimental feed-line contributions. The mean and standard deviation together capture the isolation device's overall magnitude and direction-dependent changes to the radiation pattern shape. As such, complete assessment of pattern effects requires both and parameters. Electrically longer handsets show decreased sensitivity to cable radiation suppression techniques, while dimensions less than 0 /2 require careful design consideration. Because the 79-mm-width handset's measured and values dominate those corresponding to the 50-mm-width design, geometry and wavelength determine the extent of interaction between antenna and transmission line. ACKNOWLEDGMENTDielectric substrates were provided by Rogers Corporation. AN EQUIVALENT WAVEGUIDE APPROACH TO DESIGNING OF REFLECT ARRAYS WITH THE USE OF VARIABLE-SIZE MICROSTRIP PATCHES

A unit cell waveguide model of a reflectarray formed by microstrip patches and slots

“…Similarly as in the present case, the main task in [9] was to determine a reflection coefficient of the dominant TEM mode in the equivalent waveguide. This task was carried out by determining, in the first instance, the electric current densities (J ជ P ) flowing on the conducting patches.…”

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