Abstract-In this paper, a compact circularly polarized antenna based on a resonant quadrifilar spiral structure for the application of UHF RFID handheld reader is proposed and demonstrated experimentally. To reduce antenna size and improve impedance matching, the original resonant arms are revised by bending inverted-F structures and printing them on dielectric substrates, and the four arms are fed by a four-way phase shift network. Such an antenna indicates stable circular polarization performance and wide beamwidth. The gain bandwidth (> 2 dBic) can cover the frequency band from 902 MHz to 928 MHz, which is suitable for most of the popular UHF RFID systems in the world. Moreover, the 1×4 array and 2×2 array based on previously demonstrated antenna unit are numerically investigated. The array performances, including the gain, beam scanning and low side-lobe are discussed.

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Abstract-In this paper, a novel W-band substrate integrated waveguide (SIW) power combiner/divider is analyzed theoretically and demonstrated experimentally/numerically, based on the antipodal fin-line SIW-rectangular waveguide (SIW-RW) transition and longitudinal slot coupling techniques. This antipodal fin-line SIW-RW transition can work at the frequency band of 86.4 GHz-106.1 GHz with return loss larger than 15 dB and inserting loss less than 2 dB. By combining the antipodal fin-line SIW-RW into the four-way longitudinal-slot SIW coupling structure, a novel back-to-back power dividing/combining system is achieved, which can operate at the frequency band of 92.8 GHz-93.8 GHz with return loss more than 10 dB and insertion loss less than 3.9 dB. Such a design can be used in future for spatial power amplifier applications.