Ad C. F. Reniers

A Shared Aperture Dual-Frequency Circularly Polarized Microstrip Array Antenna

A novel 2 2 array of microstrip antennas was developed that generates orthogonal circularly polarized waves at two frequencies simultaneously. This true shared aperture can be used as a building block in full-duplex wireless communication applications such as focal-plane arrays for satellite internet (VSAT) and wireless connectors. An alternative implementation of the sequential rotation technique was applied to create dual-frequency operation using only a single aperture. The concept was verified with experimental results from a prototype consisting of a 2 2 array of aperture coupled microstrip antennas (ACMAs) with corresponding feed network operating at 4 and 6 GHz. Measurements show that the axial ratio (AR) is below 1.2 dB for both the low-band as well as the high-band mode of operation. The isolation between both modes is larger than 26 dB, eliminating the need of high-performance duplexers.

The Influence of the Probe Connection on mm-Wave Antenna Measurements

Commonly used connection methods for measuring antennas in the mm-wave range, like connectors or probes, influence the intrinsic behavior of the antenna under test (AUT). It is shown that nearby structures supporting the antenna and probe or connector cause strong interference on the measured antenna pattern. A new connection setup is proposed eliminating the interfering signal. This is confirmed by a detailed simulation model and verified with experimental results. Furthermore, the probe radiates significantly due to the discontinuity from the transitions of the probe tip to the microstrip line. This radiation influences the signal-to-noise ratio, i.e., the dynamic range. Measures are proposed to reduce this interference, resulting in an improved signal-to-noise ratio by approximately 15 dB.

Measurement and calibration challenges of microwave and millimeter-wave phased-arrays

The effect of amplitude and phase errors on the radiation properties of phased array can be reduced by using a proper calibration scheme. Based on a brief review of microwave phased-arrays we derived the key requirements for a new anechoic millimeter-wave (mm-wave) antenna set-up which was constructed. The residual measurement errors obtained with this new set-up are low enough for the calibration of low-sidelobe mm-wave phased arrays.

ON THE USE OF METAL GRATINGS TO REDUCE DIFFRACTION FROM A FINITE GROUND PLANE IN CIRCULARLY-POLARIZED MICROSTRIP ARRAYS

It is shown that metal gratings can be used to improve the cross polarization of circularly-polarized aperture-coupled microstrip antennas. The metal gratings reduce edge difiraction from the flnite- size grounded dielectric slab on which the antennas are printed. The edge difiraction is due to surface waves that can propagate in the grounded dielectric slab. The design of the metal grating is based on an analytical model, which results in a flrst-order estimation for the design of the metal grating structure. The model provides physical insight and appears to be accurate enough for the application. Using this model, a prototype was developed, consisting of a circularly-polarized 2 £ 2 microstrip array with associated feeding network. Measurements show that the axial ratio can be reduced down to 1.75dB within the beam width of the antenna.

A Novel 60 GHz Wideband Coupled Half-Mode/Quarter-Mode Substrate Integrated Waveguide Antenna

A novel wideband substrate integrated waveguide (SIW) antenna topology, consisting of coupled half-mode and quarter-mode SIW resonant cavities, is proposed for operation in the 60 GHz band. This innovative topology combines a considerable bandwidth enhancement and a low form factor with compatibility with low-cost printed circuit board manufacturing processes, making it excellently suited for the next generation, high data rate wireless applications. Moreover, exploiting SIW technology, a high antenna-platform isolation is obtained, enabling dense integration with active electronics without harmful coupling. The computer-aided design process yields an antenna that covers the entire 57–64 GHz IEEE 802.11ad band with a measured fractional impedance bandwidth of 11.7% (7 GHz). The measured maximum gain and radiation efficiency of the prototype are larger than 5.1 dBi and 65%, respectively, within the entire impedance bandwidth.

Circularly Polarized Sparse Arrays Realized by Randomly Rotated Linearly Polarized Antennas

High-quality circular polarization is obtained using a novel concept that uses a sparse random distribution of randomly rotated linearly polarized antennas. Key benefit of this concept is that a very narrow circularly polarized beam is obtained with a limited number of antenna elements. Another advantage is a significant reduction of the generated heat-flux density as compared to dense regular array concepts. Both the sidelobe level and cross-polarization level can be controlled over a very wide frequency band and behave as 1/N for large array sizes, where N represents the number of array elements. A dual-frequency 16 element demonstrator was realized to show the versatility of our concept. Measured circularly polarized radiation patterns for scanning in the D-plane at 3.8 and 5.8 GHz are in good agreement with the predicted patterns.