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This paper presents a multiple-resonance technique that sought to achieve a wide bandwidth for printed wide-slot antennas with fork-shaped stubs. By properly appending an extra fork-shaped stub onto the main fork-shaped stub, the impedance bandwidth was able to be clearly broadened. To validate this technique, two designs where the extra stubs were added at different positions of the main stub were constructed. The measured impedance bandwidths of the proposed antennas reached 148.6% (0.9–6.1 GHz) for S11 < −10 dB, indicating a 17.9% wider bandwidth than that of the normal antenna (0.9–4.3 GHz). Moreover, a stable radiation pattern was observed within the operating frequency range. The proposed antennas were confirmed to be much-improved candidates for applications in various wireless communication systems.

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A novel handheld pseudo random coded ultra-wideband (UWB) radar for human sensing applications is presented in this paper. In order to reduce the size of the radar and obtain good penetrability, the center frequency of the m-sequence is assigned to about 1.1 GHz. The peak voltage of the m-sequence is 4.5 Vpp, while the length of the m-sequence can be chosen to obtain different signal-to-noise ratio (SNR). The digital transmitter, the dual-channel receiver and the clock synchronization are discussed in detail. The experimental results show that the proposed handheld pseudo random UWB radar has good detection performance for human sensing applications in complex environment.

This paper presents a novel tri-band antenna with dual polarizations and shared aperture. The proposed antenna operates at L-, Sand nd X-bands with an approximate frequency ratio of 1:1.9:5.5. Three types of radiation elements resonating at different frequencies, including the square microstrip patch, microstrip dipole, and printed monopole, are interlaced in the same aperture. Printed monopole with a fork-shaped stub is adopted as the L-band element due to its wideband ability. Both the Sand X-band elements adopt a stacked structure to enhance the bandwidth. Besides, the S-band element employs a stepped gradient structure that can obtain a wider bandwidth than the normal microstrip dipole. The measured results agree well with the simulations. The measured impedance bandwidths of L-, Sand nd X-bands are 21.7%, 11.6%, and 18.9%, respectively. The measured isolation at L-, Sand nd X-bands is higher than 25, 38, and 29 dB, respectively. The antenna also exhibits an excellent radiation performance with the high cross-polarization discrimination at the three bands. To the best of the authors' knowledge, this is the first shared-aperture L-/S-/X-band dual-polarized broadband antenna in a true sense, which is useful for potential synthetic aperture radar applications. INDEX TERMS Antenna array, broadband, shared-aperture, L/S/X-band, dual-polarized, synthetic aperture radar (SAR).

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