A wideband circularly polarized (CP) planar U-shaped antenna array is presented for millimeter-wave (mm-wave) applications. First, the antenna element consists of two tilted parasitic U-shaped patches fed by a slot etched on a substrate integrated waveguide (SIW). An improved simulated axial ratio (AR) bandwidth of 40% is achieved by stacking the slot and the patch element. Then, the right- and left-handed orthogonal unit vectors and resonant circuit technique are employed to explain the improved CP operating principle. Finally, an 8 × 8 array is achieved based on the CP element, multiple SIW cavities, and a 16-way SIW feeding network using full-corporate scheme. To verify the design, a prototype is fabricated and measured, which demonstrates a wide impedance bandwidth of 40.4%, a wide AR bandwidth of 31%, a peak gain of 24.6 dBic and supporting dual-CP mode character. The proposed antenna array shows excellent performance and a novel structure, making it a promising candidate for mm-wave wireless systems.

A compact asymmetric waveguide orthomode transducer (OMT) with broad bandwidth and high isolation is presented in this letter. A novel combined transition-bending structure is proposed within the common arm in the design of the OMT branching T-junction. It implements the E-/H-plane 90° waveguide bends and the square-to-rectangular waveguide transition for both polarization sidearms. Its multiple roles help to reduce the geometry discontinuities and improve the matching bandwidth. The measurements demonstrate that the OMT achieves higher than 50 dB isolation level between the two modes and better than 18 dB return loss from 30.3 to 36.3 GHz (18%). Furthermore, the isolation level is typically 60 dB over 50% of the operation bandwidth. The insertion loss of each polarization is below 0.23 dB for a single OMT. The overall size of the OMT functional section is reduced to $1.55\,\,\lambda _{0}\times 1.45\,\,\lambda _{0}\times 0.78\,\,\lambda _{0}$ .

A planar wideband circularly polarized (CP) end-fire antenna is presented for millimeter-wave (mm-wave) applications. First, the antenna consists of an open-ended substrate integrated waveguide (SIW) feeding line in the middle, a pair of stacked substrates with shorted triangular patches on both upper and lower sides, and an offset parallel strip. The shorted triangular patch is viewed as a horizontally polarized electric dipole, while the open-ended SIW is equivalent to an enhanced magnetic dipole due to the stacked substrates. Wide axial ratio (AR) performance is achieved by simultaneously exciting the two dipoles with orthogonal phase supplied by the offset parallel strip. Then, working principle and parameter analysis are explained and discussed for a further understanding. Finally, a prototype is fabricated and measured to verify the design scheme, which demonstrates wideband impedance bandwidth and AR bandwidth performance, novel and efficient radiating structure, simple and small antenna size. This indicates that the proposed antenna is a promising candidate to design wideband end-fire CP antenna in the mm-wave frequency band.

In this letter, a novel aperture-shared dual-polarized omnidirectional antenna for 5G application is proposed. To realize the compact and broadband characteristics, the vertically polarization (VP) and horizontal polarization (HP) share a physical region and a Wilkinson power divider with a Z-shaped feeding networks is utilized. Two antenna prototypes are fabricated and measured, with the dimensions are 0.70λ ₀ × 0.70λ ₀ × 0.07λ ₀ and 0.62λ ₀ × 0.62λ ₀ × 0.09λ ₀ for the 3.5GHz and 5.8GHz antennas, respectively. The port isolation of the 3.5 GHz antenna is better than 35 dB, with radiation efficiency higher than 85.4%. The measured -10dB impedance bandwidths of the 5.8GHz antenna are better than 23.8%. The proposed antennas are suitable for 5G application for their low-profile, compact, broadband, and dual polarization characteristics.

Inversion channel technology provides a straightforward way to integrate lasers with detectors and transistors. One inversion channel laser is the double heterostructure optoelectronic switch VCSEL which is reported here with a 2.1 mA threshold for a 10 µm diameter device. A deposited stack of SiO₂/TiO₂ was used with post-growth etching of the cavity. Excellent electrical switching parameters of V_sw = 13 V, V_h = 2.1 V and I_h = 0.5 mA were obtained, making the device suitable for the digital optoelectronic sensing of small optical inputs.

We report on a W-band frequency-modulated continuous-wave (FMCW) radar module with fractional bandwidth over 10 %. To improve flatness over large operation bandwidth, the radar module is developed with focus on the 90–101 GHz modular transceiver, for which accurate modeling of Schottky diode in combination with an integrated design method are proposed in this work. Moreover, the nonlinearity compensation approach is introduced to further optimize the range resolution. To verify the design method and RF performance of the radar module, both measurements of critical components and ISAR imaging experiments are performed. The results demonstrate that high resolution in range and azimuth dimensions can be achieved based on the radar module, of which the receiving gain flatness and transmitting power flatness are better than ±1.3 dB and ±0.7 dB over 90~101 GHz, respectively.