I. A. Illarionov - Ph.D. (Eng.), Leading Research Scientist, FSUE FRPC - Measuring System Research Institute n.a. Yu.Ye. Sedakov - (Nizhny Novgorod). E-mail: illarionovi@list.ru M. I. Dudkin - Research Engineer of 3rd category, FSUE FRPC - Measuring System Research Institute n.a. Yu.Ye. Sedakov - (Nizhny Novgorod). E-mail: dudkin.mikhail.ig@gmail.com A. V. Kuznetsov - Head of Design-Engineering Department, FSUE FRPC - Measuring System Research Institute n.a. Yu.Ye. Sedakov - (Nizhny Novgorod). E-mail: avkvk@mail.ru Ye. V. Zvereva - Research Engineer of 3rd category, FSUE FRPC - Measuring System Research Institute n.a. Yu.Ye. Sedakov - (Nizhny Novgorod). E-mail: ezvereva@mail.ru I. P. Yaroslavtseva - Design Engineer of 2nd category, FSUE FRPC - Measuring System Research Institute n.a. Yu.Ye. Sedakov - (Nizhny Novgorod). E-mail: irinadomcom@mail.ru

The main aim of our study is design of the miniaturized microstrip GNSS antenna with L1 and L2 GLONASS operating bands. The technique of the microstrip antenna miniaturizing which has been implemented in our research is to load the antenna by the high-contrast material - high permittivity ceramic with the relative permittivity equal to 10,2. The stacked topology with two patches is used in the microstrip antenna design to achieve the dual-band mode of the antenna with one-port excitation. Each patch possesses the rectangular shape with cut corners to reach the circularly-polarized radiation. We have studied two variants of stacked microstrip antenna topology with a various set of substrates thickness: 1) 5 mm (lower patch), 2 mm (upper patch); 2) 5 mm (lower patch), 4 mm (upper patch). The starting point of numerical optimization in CST MS is implementation of the transmission-line model of the microstrip patch antennas. The features of our design are particular placing of the antenna covered by a radome with relative permittivity lower than 4 and unstable ceramic properties. Thus the adjusting of the fabricated antennas is required obligatory. Our method of the adjusting is slots cutting on the face of a patch. This simple method allowed achieving good antenna characteristics on demanded bands. We performed antennas with following dimensions: 1) variant 1 - lower patch 39,7×39,7×5 mm, upper patch 30,7×30,7×2 mm; 2) variant 2 - lower patch 39,7×39,7×5 mm, upper patch 30,2×30,2×4 mm. The frequency band by VSWR is equal to 2,5 for the first variant is more than 20 MHz in L1 and L2 band. But unfortunately the best axial ratio (AR) < 3 dB is observed only for the central frequencies of specified bands. The AR exceeds 9 dB on the edge of bands for the first variant. The frequency band by VSWR is equal to 2,5 of the second variant is more than 20 MHz in L2 and more than 120 MHz in L1 band. This broad band allows to accommodate the AR of the antenna in L1 band by slit on patch face to maximum 4,2 dB in 20 MHz band. The results of numerical calculations and experimental studies of the crucial antennas characteristics have been presented. It has been shown that when using the microstrip printed antennas with a thick substrate, despite of risk of the efficient excitation of surface modes on the substrate, it is possible to achieve a sufficiently good polarization purity of the antenna even if the single-port excitation is used.

 

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