Changrong Liu

A Wideband Absorber With a Multiresonant Gridded-Square FSS for Antenna RCS Reduction

This letter proposes a wideband absorber using a multiresonant gridded-square frequency-selected surface structure. Equivalent circuit models of parallel LC resonant circuits in series are given to clarify the multiresonant working principle. Using this method, a quad-resonant absorbing ground plane is designed. Surface current distributions are shown to explicate the multiresonant modes. By using the proposed absorbing ground, a wideband dipoles radar cross section (RCS) can be reduced effectively. Measured results show that 50% absorption bandwidth of the proposed absorbing ground plane is from 2 to 2.7 GHz, and maximum RCS reduction of the antenna with absorbing ground is 5 dB. The peak gain of the antenna still maintains above 6.8 dBi in the frequency range from 1.66 to 2.76 GHz. The proposed absorbing ground has advantages such as multiresonant mechanism, wideband absorbing bandwidth, and polarization independence. Thus, it can be used to reduce antennas RCS with maintained radiation performance.

Wideband collar-shaped antenna for RF energy harvesting

This paper presents a wideband collar-shaped antenna, which was designed for multiband RF energy harvesting. The antenna consists of two folded dipoles, which are laid on a circular FR-4 substrate. The center parallel-wire transmission line and marginal bent dipoles work together to provide a broadband feature. An additional reflector ground is employed to raise the antenna directivity and suppress back radiation. The measured gain of the proposed antenna is above 7.96 dBi among the whole -10 dB bandwidth from 1.7 GHz to 3.6 GHz and the in-band peak gain reaches up to 9.05 dBi. An RF energy harvesting experiment has been conducted concerning wireless RF beams of 1.8 GHz (within Chinese mobile communication band) and 2.4 GHz (within WLAN band). The proposed antenna was connected to a dual-band RF-DC convertor and tested as part of a RF energy harvesting system. When the 1.8 GHz and 2.4 GHz RF beam was separately provided, the convertor output DC power of -27.9 dBm for the 1.8GHz beam and -26 dBm for the 2.4 GHz beam. In contrast, when both RF beams were present, the DC output power was enhanced to -20.6 dBm. The experimental results corroborate the multiband RF energy harvesting capability of the proposed antenna.

Small-Size Dual-Antenna Implantable System for Biotelemetry Devices

A dual-element miniaturized implantable antenna is designed and experimentally demonstrated at Medical Device Radiocommunications Service (MedRadio) (401-406 MHz) band for wireless biomedical multiple-input-multiple-output (MIMO) applications. First, a single-fed planar monopole antenna is designed by embedding the spiral line as a radiator and helix line on the ground. The proposed antenna element can obtain effective size reduction and wide impedance characteristic at a fixed frequency operation. Second, two antenna elements were placed in close to study the coupling strength of the two elements. The proposed MIMO antenna has dimensions of 22 × 22 × 0.635 mm3. The simulated and measured impedance bandwidths are 35.9% and 61.7%, respectively. The measured maximum mutual coupling is below -26 dB at MedRadio Band.

Uniform Periodic Leaky-Wave Antennas With Eliminated Open Stopbands

This letter studies an open stopband elimination method for a class of periodic leaky-wave antenna (PLWA) composed of two varied uniform transmission lines in alternatively cascading arrangement. By using a transmission line model, a dispersion diagram is extracted and an equal phase shift condition of <italic>β</italic>₁<italic>L </italic>₁ = <italic>β</italic>₂<italic>L</italic>₂ is proposed to eliminate the open stopband at broadside. The working principle is illustrated by numerical extraction and calculation. To verify the proposed method, an antenna prototype with two kinds of transmission lines—microstrip lines with and without covering strips—is accordingly designed and fabricated. Furthermore, simulated and measured results coincide well with the numerical prediction, showing that the proposed strip-covered uniform PLWA owns a certain radiation capability to continuously scan through the broadside direction.

Dual-band monopole antenna with multi-band EBG ground plane for 2.4/5 GHz WLAN applications

This paper presents a 2.4/5 GHz WLAN dual-band monopole antenna with wideband electromagnetic band-gap (EBG) ground plane. The monopole consists of a shorter direct-fed part and a longer ground-shorted coupled part so as to produce 2.4 GHz and 5GHz bands, respectively. The ground plane is composed of mushroom-like EBG structures for the purpose of reducing the ground influence and improving the antenna radiation performance. Simulated dispersion diagram of the proposed EBG structure has been given, which shows multiple band gaps covering WLAN lower and higher bands. Reflection coefficients and radiation patterns between the proposed monopole with the conventional ground and the proposed EBG ground are compared, which verifies the validation of the proposed EBG structure to reduce the influence of the ground plane and improve the antenna performance.