The eleven antenna: a compact low-profile decade bandwidth dual polarized feed for reflector antennas

A novel dual polarized ultrawide-band (UWB) feed with a decade bandwidth is presented for use in both single and dual reflector antennas. The feed has nearly constant beam width and 11 dBi directivity over at least a decade bandwidth. The feed gives an aperture efficiency of the reflector of 66% or better over a decade bandwidth when the subtended angle toward the sub or main reflector is about 53°, and an overall efficiency better than 47% including mismatch. The return loss is better than 5 dB over a decade bandwidth. The calculated results have been verified with measurements on a linearly polarized lab model. The feed has no balun as it is intended to be integrated with an active 180° balun and receiver. The feed is referred to as the Eleven antenna because its basic configuration is two parallel dipoles 0.5 wavelengths apart and because it can be used over more than a decade bandwidth with 11 dBi directivity. We also believe that 11 dB return loss is achievable in the near future

Study of Grating Efficiency of Planar Arrays

This paper studies the aperture efficiency reduction due to grating lobes of a uniformly excited planar array. The grating lobes will not cause major interference problems in the millimeter wave region, because of the attenuation in the atmosphere, but they cause a reduction of the directivity and thereby aperture efficiency of the antenna. Therefore, we present a simple formula for calculating the aperture efficiency in the presence of grating lobes, from knowledge of the element pattern. The accuracy of the formula is verified by comparing with simulated results for a full array with slot elements

Contactless non-leaking waveguide flange realized by bed of nails for millimeter wave applications

Waveguide flanges are typically used to connect and measure high frequency circuits. When good conductive contact is not provided between the joining flange surfaces, currents will flow between them, and thereby causing leakage and losses affecting the circuit performance. This work presents a non-leaking contactless waveguide flange made with bed of nails. The flange does not need any contact when connected to another smooth flange, since the pins surface and the smooth surface together form a stopband suppressing any current and wave propagation between the two joining surfaces of the flanges

Ka-band gap waveguide coupled-resonator filter for radio link diplexers

Gap waveguide technology represents an interesting alternative as low-loss, cost-effective and high-performance transmission line and package of microwave and millimeter-wave systems. A Ka-band coupled-resonator filter for a radio link diplexer, which requires high selectivity to isolate transmit and receiving channels, is proposed and realized using gap waveguide technology. The band-pass filter, which has a central frequency of 37.37 GHz and a pass bandwidth of 560 MHz, is fabricated between two metal parallel plates leaving an air gap between them. Measurements show a minimum in-band insertion loss of 1 dB and agree quite well with simulations

High Efficiency 2x2 Cavity-Backed Slot Sub-array for 60 GHz Planar Array Antenna Based on Gap Technology

This paper presents a two layer 2x2-slot element as a sub-array for 60 GHz planar array antenna based on gap waveguide technology. The proposed element consists of 2x2 slots in a gap waveguide cavity where the cavity is fed through a coupling slot from a ridge gap waveguide corporate-feed network in a lower layer. The 2x2-slot sub-array is numerically optimized in an infinite array environment. The designed sub-array shows the relative bandwidth of 11% with reflection coefficient better than -13 dB over 58.2-65 GHz frequency band. A prototype of a 8x8-element slot array antenna is designed and fabricated in order to verify the simulations

V-band high efficiency corporate-fed 8×8 slot array antenna with ETSI class II radiation pattern based on gap technology

A multilayer gap waveguide 8×8 slot array antenna with high efficiency for 60 GHz applications is presented in this paper. The proposed antenna is composed of three unconnected metal layers. A ridge gap waveguide corporate distribution network feeds a radiation layer with 4×4 cavity-backed slot subarrays. The co-polar radiation pattern and sidelobe levels of the antenna are improved by using a simple slot-tilting method to fulfill the radiation pattern requirement of the ETSI 302 standard for fixed radio links. The fabricated prototype has a relative bandwidth of 12 % with input reflection coefficient better than -10 dB. The E- and H-planes radiation patterns satisfy the ETSI class II co-polar sidelobe envelope over 57-65 GHz frequency band. The measured total aperture efficiency is better than 65% over the operating frequency band

Numerical studies of bandwidth of parallel-plate cut-off realised by a bed of nails, corrugations and mushroom-type electromagnetic bandgap for use in gap waveguides

Recently it has been shown that so-called gap waveguides can be generated in the gap between parallel metal plates. The gap waveguides are formed by metal ridges or strips along which local waves propagate, and parallel plate modes are prohibited from propagating by providing one of the surfaces with a texture that generates an artificial magnetic conductor (AMC) or an electromagnetic bandgap (EBG) surface on both sides of the ridges or strips. The bandwidth of the gap waveguide is determined by the cut-off bandwidth of a parallel-plate waveguide where one surface has such a texture (and no ridges or strips). This paper studies the bandwidths (or stop bands) of such parallel-plate cut-offs when the AMC or EBG is realised by a metal pin surface, corrugations or a mushroom surface. It is shown that cut-off bandwidths of up to 4:1 are potentially available, and thereby similar bandwidths should be achievable also for gap waveguides

Slot antenna in ridge gap waveguide technology

A Slot antenna design based on recently developed gap waveguide technology has been presented in this work. This antenna can be built easily by having the feed network on the bottom metal plate, where the ridge will be distributing the waves for equal excitation of each slot element, and the top metal plate will have the slots. Design and simulation results of the basic T-junction for a corporate-feed network and the single element slot show that it is possible to have an array antenna with BW of 15 % or more based on ridge gap waveguide technology

Gap waveguides and PMC packaging: Octave bandwidth mm- and submm-wave applications of soft & hard surfaces, EBGs and AMCs

AMCs, EBGs and other surface-based metamaterials are known to have narrow bandwidths. However, when they are used to generate stopbands for parallel-plate modes, the bandwidth can be very large. This characteristic is used in the gap waveguide technology that was invented in 2008, based on old research on soft and hard surfaces. The gap waveguide technology can be used to package microstrip and CPW circuits, but can also with advantage replace such standard technologies and in particular above 30 GHz. The gap waveguides can have similar lowloss performance as solid rectangular waveguides, but they can be realized in a much better way. Rectangular waveguides are normally realized by split blocks which are screwed tightly together to ensure good conductive contact, whereas gap waveguides can be realized between parallel plates without metal connection. This paper overviews how the gap waveguide technology has been explored during the passed five years including: demonstrations of the wideband lowloss guiding characteristics up to 260 GHz, demonstrations of packaging in different frequency ranges with different AMCs or EBGs, and demonstrations of filters, transitions, MMIC packaging, corporate distribution networks, and slot and horn array antennas. The technology demonstrators cover the three different versions of gap waveguides: groove gap waveguide, ridge gap waveguides and microstrip gap waveguides

Preparing for GBit/s coverage in 5G: Massive MIMO, PMC packaging by gap waveguides, OTA testing in random-LOS

In this invited presentation I describe how we prepare for 5G in my research division. The background is that we have contributed to 3G and 4G developments with two commercial successes: The hat-fed reflector antenna for backhaul radio links, and Bluetest reverberation chambers for OTA (Oer-The-Air) characterization of devices with MIMO and OFDM. 5G means Gbit/s data rates, for which higher frequencies are needed towards the user terminal, may be up to 30 or 60 GHz. This means that the multipath will be weaker as it gradually diminishes when frequency increases. Therefore, we prepare by introducing a Random-LOS (RLOS) complement to the OTA testing in Rich Isotropic Multipath (RIMP) being provided by Bluetest\u27s reverberation chambers. Further, high gain steerable beams will be needed, requiring new planar packaging solutions for closer integration of antennas and RF chipsets. Therefore, we prepare by research on gap waveguides. Massive MIMO have many technological uncertainties, so others also consider old-fashioned phased arrays, but they will not work in RIMP. The best hardware can only be chosen if we know how to characterize the system performance. The radiation pattern and realized gain cannot be used directly for this purpose due to all the statistical variations caused by the arbitrariness of the user. Therefore, we introduce instead the Probability of Detection (PoD) as a quality metric. This will be different for each desired number of bitstreams. Further, we quantify the difference between different PoD curves in dBiid in RIMP, i.e. in dB relative to the i.i.d. (idependent identically distributed) case, and in dBt in RLOS, i.e. in dB relative to an ideal polarization- and coverage- matched threshold receiver. The presentation will give an overview of this research