A novel wideband filtering patch antenna loaded T-Shaped strips is proposed in this paper. The antenna consists of a radiating patch with a pair of symmetrical T-shaped strips and a parasitic branch located at the bottom of the dielectric substrate. Introducing a pair of T-shaped strips on both sides of the square patch excites a low-frequency resonant mode and generates a radiating null at the edge of the lower-band. Then, a rectangular branch is introduced underneath the substrate as a quarter-wavelength open-circuit strip, and a high-frequency resonant mode and an upper-band radiation null are created. In addition, the introduction of the two structures above excites double resonant modes, which will efficiently improve the bandwidth of the antenna. The prototype has been fabricated and measured. The measurement results of the proposed wideband filtering antenna show that the -10 dB impedance bandwidth is 16.1% (from 2.29 GHz to 2.69 GHz), with a peak gain of 9.6 dBi. Two radiation nulls besides the passband are located at 2.23 GHz and 2.81 GHz, separately. What's more, the antenna is simple in structure and easy to manufacture.

This letter presents a reconfigurable antenna that uses gravity to control the self-circulation of liquid metal (LM), thereby realizing an adaptive reconstruction method. Then the polydimethylsiloxane (PDMS) structure with a square ring channel is loaded on the microstrip antenna, and the contact position between the liquid metal and the patch is controlled by gravity, which provides conditions for reconfiguration. The antenna has four reconfigurable frequency bands, which can be switched between the dual circle polarization (left- and right-hand circular polarization) mode and the linear polarization (LP) mode without additional mechanical adjustment structures, radio frequency circuits or related components. The measured results show that the proposed antenna has −10 dB impedance band of 1.2-1.6 GHz, 2.5-2.75 GHz, 4.2-4.55 GHz and 5-5.4 GHz and peak gain of 3.6 dBi, 5.07 dBi, 2.68 dBi and 3.25 dBi within passband, which agree well with the simulated results.

A novel fifth-order dual-band half-mode substrate integrated waveguide filtering antenna with a multifunctional single slot and seven shorting pins of different sizes integrated into a single layer is presented in this letter. Initially, the fifth-order modes TM _3/2,1 , TM _5/2,1 , TM _3/2,3 , and TM _5/2,3 have been excited successively by the coaxial feed. Then, seven shorting pins of different sizes have been loaded to reallocate these modes to form dual passband characteristics and generate three transmission zeros. In addition, a multifunctional slot has been etched to improve the out-of-band suppression, and the radiation gain of the second passband has increased approximately by 5.5 dB. Finally, a prototype has been fabricated and measured to validate the design. The measured results show that the proposed antenna has a $-$10 dB bandwidth from 2.49-2.56 GHz and 3.37-3.49 GHz. It has a peak gain of 7.9 and 8.55 dBi within passband, which are in good agreement with the simulated results.

An ultraminiature two-pole bandpass filter based on the eighth-mode substrate integrated waveguide is proposed in this letter. The combination of a coplanar waveguide and circular-ring miniaturized element as a new feeding method is used to improve the out-of-band rejection by introducing two transmission zeros. The measured insertion loss and return loss of the filter operated at 690 MHz are 1.25 dB and better than 20 dB, respectively. The out-of-band rejection is better than 30 dB up to 3 GHz. The equivalent circuit, simulation, and measured results are consistent with one another. The overall size of the filter is 35 mm x 35 mm, which is equivalent to 0.08λ₀ x 0.08λ₀. A miniaturization factor of 98.8% is achieved.

A new type of low-profile filter antenna with low H-plane cross polarization (cross-pol) and good suppression of sidebands is proposed using multifunction single slot and five shorting pins integrated into half-mode substrate integrated waveguide (SIW). Initially, the TM1,3/2 mode, the TM1,5/2 mode, and the TM3,1/2 mode have been excited successively in the low H-plane cross-pol SIW. Then, in order to realize third-order half-mode radiation of the antenna, the five shorting pins and the key slot have been used to reallocate those modes above. In addition, the slot also introduces two transmission zeros at 4.94 and 6.12 GHz to improve the filtering characteristic and to suppress the sidebands of the antenna. Finally, the filtering antenna is designed at 5.16 GHz with 2.5% impedance bandwidth for WLAN wireless communication application. The attenuation for lower sideband is always below 30 dBi, while the corresponding bandwidth for upper sideband achieves high out-of-band suppression levels of 20 dBi is about 1.52 GHz. The cross polarization can reach below -30 dB; meanwhile, its gain in frequency band is 6.79 dBi above. In addition, the low-profile property has been obtained with the height of 0.0087 free-space wavelength.

A polarization-reconfigurable liquid dielectric resonator antenna is introduced in this letter. The antenna uses gravity-controlled ethyl acetate as the reconfigurable variable, which can adapt to the attitude of the equipment and realize the independent switching between linear polarization, i.e., left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP), without an additional control circuit or mechanical structure, which greatly reduces the manufacturing cost. Under circular polarization, LHCP and RHCP have bandwidth utilization of 92.6% and 61.3%, respectively, and peak gain of 6.9 dBi and 7.2 dBi, respectively. The simulation results of the antenna prototype agree with the measured results. The antenna works in industrial scientific medical (ISM) band, which can be used in Wi-Fi intelligent equipment, vehicle satellite communication, and other scenes.