A double-layer wideband transmitarray antenna using two degrees of freedom elements is presented. The double-layer transmitarray antenna is composed of 441 elements. Each element includes four metal vias and two patches with two degrees of freedom (TDF) printed on both sides of the dielectric substrate. Four metal vias are used to achieve the maximum transmission magnitude and two patches with TDF are adopted to obtain a sufficiently large variation range of phase shift. A square transmittarray is designed, fabricated, and measured to validate the proposed design. Simulation and measurement results have good agreement. Experimental results show that the proposed antenna has high gain of 30.0 dBi at 21GHz, aperture efficiency of 40% and 1-dB gain bandwidth of 9.6% (20.1GHz-22.2GHz). The proposed double-layer transmittarray antenna greatly simplifies the design complexity and reduces the thickness, the mass, and the cost with respect to existing transmitarray antennas.

A new dual-polarized dual-band (DPDB) omni-directional antenna is presented in this communication. The proposed antenna consists of a circular patch with eight open slots, eight shorted metal pins, and a central feed coaxial probe. By utilizing TM ₀₁ mode, eight shorted metal pins, and open slots can radiate $\theta$ - and $\varphi$ -components, respectively. Omni-directional circular polarization can be generated over the lower band. When the basic TM ₀₂ mode is excited, omni-directional linear polarization can be generated over the higher band. Omni-directional circularly polarized fields and omni-directional linearly polarized fields can be achieved at both resonant frequencies. The circular patch antenna is printed on a substrate with a radius of 48 mm ( $0.24~\lambda _{\mathrm {\mathbf {0}}}$ , where $\lambda _{\mathrm {\mathbf {0}}}$ is the wavelength in free space). The antenna has a low profile of 4 mm ( $0.02~\lambda _{\mathrm {\mathbf {0}}}$ ). The antenna is fabricated and measured; the measured results show that the impedance bandwidths for VSWR <2 are 18 MHz (1566—1584 MHz) and 32 MHz (2440—2472 MHz). The axial ratio in the xoy plane is less than 3 dB over the lower band. These measured results are congruent with the simulated data. The antenna can be a good candidate for both GPS and WLAN applications. Besides, the S-parameters, radiation patterns, and some key structures are studied.

This communication proposes a low-profile dual-band circularly polarized (CP) antenna for satellite communication at K and Ka-bands. The antenna consists of a folded transmitarray (TA) operating at 20 GHz and a multi-feed reflectarray (RA) operating at 30 GHz. The dual split rings are used as the TA and RA elements. The TA is placed above the RA. The TA acts as the phase-controlling surface at 20 GHz and does not affect the transmission of plane waves at 30 GHz generated by the RA. The RA simultaneously serves as the phase-controlling surface at 30 GHz and as the ground for the folded TA at 20 GHz. Owing to the combination of the folded TA and multi-feed RA with a small focal length-to-diameter ratio, the antenna profile is reduced, and the height-to-diameter ratio is only 0.4. Compared with the traditional horn feed system, the CP patch arrays integrated on the TA surface are used as the feeds in this design. The orthomode transducer (OMT) and circular polarizer are not needed, which significantly saves space and cost. The antenna was manufactured and measured to verify its performance. The measured results keep good consistent with the simulated results.

A novel design of 2.45GHz rectifying antenna (rectenna), which are composed of antenna element, two-element series-fed array and four-element cascaded array,have been proposed in this paper. The array designs are introduced in order to adapt various power density if used in the array, especially in near-field of the transmitting antenna, in this case the power density in the center and far away from center differs greatly. The compact low profile air supported microstrip antenna is introduced as receiving antenna element in order to reduce substrate loss. The rectifying circuit has been designed and optimized using ADS software. The diode in the rectifying circuit is installed in series and the capacitance is replaced by microstrip line as DC pass filter. A maximum RF to DC conversion efficiency of the rectifying circuit can reach 80% when input power is 21dBm and 3500Ù resistive load is connected to the circuit end through experiment. The rectenna exhibits a maximum efficiency of 77.2% and an output dc voltage of 18.5V. The proposed rectenna element and array can be easily expanded to large scale integrated rectenna arrays, it will be practically attractive for wireless power transmission system design.

A method for designing linearly-polarized-feed dual-circularly polarized dual-beam transmitarray (TA) is presented in this letter. According to a theory, a linearly polarized (LP) wave can be decomposed into left-handed and right-handed circularly polarized (LHCP and RHCP) waves. The LHCP and RHCP phase can be compensated independently and simultaneously by adjusting the initial and rotation phases of the element so that the LHCP and RHCP beams of the TA can appear simultaneously in space and can be controlled independently. The designed receiver-transmitter element is used to achieve the above functions, and the TA is fabricated and measured. Simulated results are consistent with experimental results.

A multifunctional tri-band antenna combining transmitarray (TA) and reflectarray (RA) is presented in this communication. Five-layer patches etched on three dielectric substrates with two air gaps are used as the unit cell. Cross dipoles inserted in cross slots control transmission characteristics at Ku-band (14 GHz). Double square rings on the top and bottom layers control reflection characteristics at K (21 GHz) and Ka (30 GHz)-bands, respectively. The antenna has dual-polarized characteristics in each band. The phase shift range that can be obtained is 360° for 3 dB transmission magnitude at Ku-band and 0.15 dB reflection magnitude at K and Ka-bands. The tri-band dual-polarized TA/RA antenna is designed, manufactured, and measured to verify the performance. The simulated results keep consistent with the measured ones. The measured results show that the TA has a peak gain of 23.8 dBi with an aperture efficiency of 40% at 14.25 GHz and 1-dB gain bandwidth of 6.5%. The RA has a peak gain of 28 dBi with an aperture efficiency of 44% at 21 GHz and 1-dB gain bandwidth of 7.3%, and has a peak gain of 31.5 dBi with an aperture efficiency of 47% at 30.5 GHz and 1-dB gain bandwidth of 7.1%.