Showing papers by "Per-Simon Kildal published in 2013"

Ka-Band Gap Waveguide Coupled-Resonator Filter for Radio Link Diplexer Application

Abstract: 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 parallel metal plates, leaving an air gap between them. After milling one of the plates, silver-plating is applied on them. Measurements show a minimum in-band insertion loss of 1 dB and agree quite well with simulations.

Study of Q-factors of ridge and groove gap waveguide resonators

Abstract: The gap waveguide technology for millimeter waves applications has been recently presented. The new structure is made by generating a parallel plate cut-off region between an artificial magnetic conductor (AMC) and a metallic plate. Propagating waves will be only allowed to follow a metal ridge or groove surrounded by the AMC. The gap waveguide can be made of only metal and does not need any contact between the metal joints compared to standard waveguides. In this study, a study of Q-factors of resonators made in ridge and groove gap waveguides are presented. The resonators are made of copper and the AMC used is a textured surface of metallic pins. Simulated and measured unloaded Qs are presented and compared with Q of a standard rectangular waveguide. High Q-factors are measured for the prototypes presented, approaching 90-96% of the simulated values. Furthermore, it is shown how the lid of pins can easily stop the leakage loss at the joints of the circuit, which is the typical cause of reduced Q-factor of standard waveguides at high frequency.

Design of a Simple Transition From Microstrip to Ridge Gap Waveguide Suited for MMIC and Antenna Integration

Abstract: This letter describes a simple and low-loss microstrip-to-ridge gap waveguide transition with a very compact geometry. The transition transforms the electromagnetic (EM) fields from the microstrip mode to the air-filled ridge gap waveguide mode. This is achievable if the height of the air gap in the ridge gap waveguide is kept almost equal to the thickness of the substrate of the microstrip line. The transition has a pressure contact between the ridge and the microstrip line, so it works without soldering. This is advantageous in systems that require mechanically separable split-blocks or modules and need a lot of transitions. Experimental results of the manufactured back-to-back transition show an insertion loss of 0.32 dB and a return loss of 14.15 dB over 55% relative bandwidth in Ka-band.

MRC Diversity and MIMO Capacity Evaluations of Multi-Port Antennas Using Reverberation Chamber and Anechoic Chamber

Abstract: It has been shown that diversity gains and MIMO capacity of multi-port antennas can be conveniently determined from reverberation chamber measurements. In this paper, we first present the covariance eigenvalue approach and the embedded far field function method to determine diversity gain and MIMO capacity, respectively, for arbitrary multi-port antennas. Then, we discuss the convergence of the covariance eigenvalue approach. In the end, we apply both methods to compare MRC diversity gains and MIMO capacity measured in a reverberation chamber (based on direct channel measurements) and an anechoic chamber (based on measurements of the embedded far field functions and efficiencies at all antenna ports). The comparison is performed over 2-8 GHz using a wideband multi-port antenna in two configurations. There are in general good agreements between the reverberation and anechoic chamber measurement results.

Resemblance between gap waveguides and hollow waveguides

Abstract: There is a lack of suitable numerical ports for the gap waveguides This study studies the resemblance between the ridge/groove gap waveguide and the conventional hollow ridge/rectangular waveguide, respectively, by using numerical analysis The dispersion diagrams and characteristic impedances are compared and found to be similar within the stopband of the parallel-plate modes Therefore conventional hollow waveguides can be used as ports in numerical analysis of gap waveguides In addition, this means that the geometry of circuit components in hollow ridge/rectangular waveguides can be used as a good starting point when designing ridge/groove gap waveguide components

Rethinking the Wireless Channel for OT A testing and Network Optimization by Including User Statistics:RIMP, pure-LOS, Throughput and Detection Probability

Abstract: The reverberation chamber has through the last thirteen years been used to emulate a rich isotropic multipath (RIMP) environment, and it has successfully been demonstrated that it can be used to test performance of multiport antennas and complete wireless terminals with MIMO and OFDM. The measured throughputs of practical LTE devices have been shown to be in excellent agreement with basic theoretical algorithms. Now is the time to use this concept and complete the picture so that also real-life environments can be covered. This is done by introducing the pure-LOS as another limiting edge environment, and by introducing the statistics of the user. The latter plays a major role in pure-LOS that thereby becomes a random-LOS. The two limit-environments are linked together with a real-life hypothesis, and work has started to test this by simulations. It will be shown that the major characterizing quantity becomes the detection probability of the single or multiple bit streams (for diversity and multiplexing cases, respectively) over an ensemble of users. This detection probability becomes equal to throughput in a multipath environment, readily seen through a simple threshold receiver model representing an ideal digital receiver. The new approach represents a way to start optimizing the wireless networks by taking the statistics of the user into account.

Characterization of Implemented Algorithm for MIMO Spatial Multiplexing in Reverberation Chamber

Abstract: Previously, the throughput for a single-input multiple-output (SIMO) system was successfully tested in a reverberation chamber (RC), and the results were in good agreement with a model based on the ideal threshold receiver. In the present communication, we measure the throughput of a 2 × 2 open loop multiple-input multiple-output (MIMO) system with full spatial multiplexing (i.e., two data streams), and we compare the results with an extended throughput model taking the spatial multiplexing into account. The measured throughput is found to be in agreement with the simulated one of a simple zero-forcing (ZF) receiver. The throughput degradations due to correlation and power imbalance (caused by different embedded radiation efficiencies of antennas) are studied and referred to as a throughput multiplexing efficiency. These can, to a large extent, be explained by the ZF algorithm. The results show clearly that the rich isotropic multipath (RIMP) environment generated by an RC can be used to study how effective different MIMO algorithms are when there is correlation and efficiency imbalance between the antenna elements.

Suppression of Parallel Plate Modes in Low Frequency Microstrip Circuit Packages Using Lid of Printed Zigzag Wires

Abstract: This work deals with the suppression of parallel plate and cavity modes in shielded microstrip circuits operating at the lower microwave frequency range. The suppression is achieved by using a lid made of zigzag wires printed periodically on narrow slices of ungrounded circuit boards, located vertically side by side. This structure is very compact both in periodicity and height, it suppresses cavity modes over about an octave 2:1 bandwidth, and it does not interfere with the packaged microstrip circuit.

Ku band linear slot-array in ridge gapwaveguide technology

Abstract: A Ku band 4×1 linear slot array antenna design based on recently developed gap waveguide technology is presented. The complete antenna has been built using two parallel plates where the bottom metal plate has the guiding ridge and periodic pins and the top metal plate is smooth. The antenna feed network consists of power dividers has been realized on the bottom metal plate, and the radiating slots are placed on the top metal plate. Design and simulation results of the linear array show that it is possible to have a slot array antenna with 20 % bandwidth based on ridge gap waveguide technology.

Gap waveguide structures for THz applications

Abstract: A microwave/millimeter device having a narrow gap between two parallel surfaces of conducting material by using a texture or multilayer structure on one of the surfaces is disclosed. The fields are mainly present inside the gap, and not in the texture or layer structure itself, so the losses are small. The microwave/millimeter wave device further comprises one or more conducting elements, such as a metallized ridge or a groove in one of the two surfaces, or a metal strip located in a multilayer structure between the two surfaces. The waves propagate along the conducting elements. At least one of the surfaces is provided with means to prohibit the waves from propagating in other directions between them than along the ridge, groove or strip. At very high frequency, the gap waveguides and gap lines may be realized inside an IC package or inside the chip itself. Conventional machining such as, but not limited to: drilling, milling and sawing, cannot define the structures with the precision required of devices between 100 GHz and 10 THz. To obtain the high precision required, microsystem manufacturing methods such as deep reactive etching can be used to define the structures with high precision. Alternative fabrication methods such as injection molding or other micromolding process may also be used. A metal layer can cover some or all surfaces.

Design of a dual-mode horn element for microstrip gap waveguide fed array

Abstract: The low loss microstrip gap waveguide provides an easy and suitable solution to be used as feed network for antennas at high frequency. This paper presents the design of a slot coupled dual-mode horn element fed by microstrip gap waveguide for array applications at 60 GHz. The directive dual mode horn is used to reduce the grating lobes which are generated when the slot array elements have a distance bigger than lambda. Simulation results of the proposed design are presented in terms of return loss and grating lobe level.

Definition of Antenna Diversity Gain in User-Distributed 3D-Random Line-of-Sight

Abstract: The present paper defines diversity gain for stationary users. This deals in particular with gathering the received signal statistics over possible user positions and orientations in space rather than over time, and to define a meaningful diversity gain related to the cumulative improvement of the performances of the 1% users with the worst receiving conditions. The definition is used to evaluate diversity gain for some typical small antennas in an extreme environment with only line-of-sight (LOS). The LOS environment is regarded as user-distributed 3D-random LOS caused by the statistics of an ensemble of stationary users with arbitrary orientations in the horizontal plane (2D), and with arbitrary orientations of their wireless devices in the vertical plane. Thus, an overall 3D-random distribution of user orientation is assumed.

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

Abstract: 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.

Parabolic cylindrical reflector antenna at 60 GHz with line feed in gap waveguide technology

Abstract: A parabolic cylindrical reflector antenna is proposed in this paper for wireless multi-gigabit communications at 60 GHz. The line feed is realized by a power distribution in parallel plate waveguide (PPW). Inside the PPW waveguide there are metal pin rows forming the contours of an H-plane horn structure in front of a parabolic reflector, where we see possible mechanical advantages in not requiring metal contact of the pins to more than one metal plate. They will still work as a total reflecting wall by making use of the same stopband features as in gap waveguide technology. The result is a low loss, low cost and very versatile 60 GHz antenna with high gain. The electrical design for maximum aperture efficiency and minimum loss is explained.

Some reflector and feed antenna inventions that made a difference: Fundamentals and examples from radio telescopes, satellite communications and radio links

Abstract: The paper will review some inventions within reflector antennas and feeds that represented a large step forward when they were introduced, in terms of both performance and industrial or scientific usefulness. The fundamental design principles as well as the actual solutions will be overviewed in a simple manner. The overview covers dipole-disk with ring for ship Earth stations, corrugated horns, hat-fed antennas for radio links, and wideband log-periodic “eleven” feed for SKA and VLBI 2010 radio telescopes. The inventions can in all cases be associated with simple fundamental EM principles, and an improvement of a fundamental subefficiency.

Study of the characteristic impedance of gap waveguide microstrip line realized with square metal pins

Abstract: This paper addresses how to define the numerical ports in the gap waveguide microstrip line, and also a study of its characteristic impedance when the parallel-plate stopband is realized by using metal pins. The results presented here are produced using commercially available EM simulators. The paper also includes a study of how to minimize the effect of the transverse locations of the pin structure under the microstrip line, relative to the location of the strip.

Efficiency, correlation, and diversity gain of UWB multiport self-grounded bow-tie antenna in rich isotropic multipath environment

Abstract: The paper studies the performance of a novel ultra-wideband multiport self-grounded bow-tie antenna and presents simulated embedded radiation efficiencies and correlation at each antenna port, and the diversity gain of the antenna in rich isotropic multipath environment.

Design of a four-element horn antenna array fed by inverted microstrip gap waveguide

Abstract: The paper presents the design of a four-element slot coupled dual-mode horn array with microstrip gap waveguide as feed network. We present simulated results for return loss for the feed network both with and without the radiating horn array. We also compare results for two ways to generate the stopband of the parallel-plate modes: the ideal Perfect Magnetic Conductor used during the initial design, and the real bed of nails used in the practical realization. The study is performed at 60 GHz obtaining about 10% bandwidth.

Packaging of MMIC by using gap waveguide and design of a microstrip to ridge gap waveguide transition

Abstract: In this work, gap waveguide based packaging technique is used to improve the isolation among critical microwave circuit components such as high gain amplifier chain. Amplifier chains at Ka-band were tested for a stable forward gain and it was found that-with gap waveguide packaging, 65~70dB of forward gain is achievable without the problem of self-resonance. Apart from the new packaging technique, a low-loss transition from microstrip to ridge-gap waveguide had been designed and tested. This transition is a key component to connect such amplifier chains to a planar slot array antenna. Experimental results for manufactured back to back transition show 14 dB return loss over 55% relative bandwidth from 2343GHz.

100 GHz SOI gap waveguides

Abstract: Two gap waveguide technologies, groove and ridge, are presented here for F-band applications. Three different groove gap waveguide devices and four different ridge gap waveguide devices have been fabricated. All of them were micromachined to achieve the feature size required for the frequency band and fabricated in a single process using SOI wafers. The two types provide a more robust coupling to standard waveguides and high frequency probes. Measurements for most of the devices are shown in this paper, showing robust measurements and good agreement with simulations. More measurements need to be done but the initial ones show the promise both in the manufacturing technique and the coupling.

Micromachined Groove Gap Waveguides for 100 GHz applications

Abstract: The present paper demonstrates groove gap waveguides at around 100 GHz, fabricated on Gold-plated micromachined silicon. Three different groove gap waveguides have been manufactured and measured: a resonator for determining Q-factor and thereby attenuation, a straight waveguide, and a waveguide with two 90 degree bends.

Overview of developments of the eleven feeds

Abstract: An overview of different versions of the Eleven feed and recent development is presented in the paper. Eleven feeds have a nearly constant beamwidth and a fix phase center, with a performance of an aperture efficiency higher than 60%, -10 dB reflection coefficient, -0.2dB radiation efficiency, and -15dB cross-polar level, over a decade bandwidth. The Eleven feed can be very compact after applying newly developed optimization algorithms, and some new results of the feed in dual-reflector antennas are reported here.

Correlation between far-field patterns on both sides of the head of two-port antenna on mobile terminal

Abstract: We present an electromagnetic simulation of a practical mobile terminal with a two-port MIMO antenna on left and right sides of the head. The computed far-field patterns include the effect of head and hand phantoms. We show that the far-field patterns on the two sides are strongly correlated if they are presented in the coordinate system of the phone, but they are completely uncorrelated in the coordinate system of the environment.

Diversity gains of multiport mobile terminals in multipath for talk positions on both sides of the head

Abstract: The paper studies the over-the-air (OTA) performance of a mobile terminal. A practical two-port mobile terminal model on the left side and the right side of the head for both standard cheek position and standard tilt position is used to study the diversity gains. The diversity gain has been determined by measurements in a reverberation chamber as well as by simulations using the far field patterns from CST Microwave Studio, and then exposing these patterns to rich isotropic multipath (RIMP) environment in a ray-based simulation tool.

Investigation of the distribution of the random LOS component in a reverberation chamber

Abstract: In the previous measurement uncertainty work by Kildal, et al. (2012), the random line-of-sight (LOS) component in a reverberation chamber (RC) was assumed to be Gaussian distributed without quantitative justification. In the present paper, we apply goodness-of-fit (GOF) test to the measured LOS component samples to check its Gaussianity. It is shown that the Gaussianity hypothesis of the distribution of the random LOS component is accepted at most of the frequencies, which justifies the Gaussian LOS component assumption.

Simple models for multiplexing throughputs in open- and closed-loop MIMO systems with fixed modulation and coding for OTA applications

Abstract: In this paper, we study the multiplexing throughputs of open- and closed-loop multiple-input multiple-output (MIMO) systems with fixed modulation and coding (i.e., fixed maximum data rate). For the open-loop case, we assume the simplest linear decoder, i.e., zero forcing (ZF). For the closed-loop case, we assume singular value decomposition (SVD). Using the threshold receiver model (accounting for the advanced coding), the throughput for either case can be readily obtained via simulations. MIMO antenna degradations such as correlation and imbalanced antenna efficiencies can be readily included in the developed throughput model. In addition to the usual presentation of the average throughput in a fading channel, we introduce the user-distributed detection probability of the (data) streams.

In Memoriam: Olof Dahlsjo

Abstract: The antenna and radome activities at Ericsson were initially related to the development of military airborne radar. Under Olof Dahlsjo's leadership, they also developed into other types of radar, as well as communications for ground, airplane, and space applications. The activity became world leading with a solid scientific foundation, examples of which are polarization-twisting, satellite antennas for scientific pro grams, and phased arrays. The latter were initially done together with the research group of Prof. Folke Bolinder at Chalmers, and several people from his group later started to work for Olof Dahlsjo.

EuCAP 2013 in Gothenburg, Sweden: “An Impressive Success” [EurAAP Corner]

Abstract: “Impressive Success” is, of course, not our words, but we take them to our hearts and want to share them with the readers of the Antennas and Propagation Magazine. And, yes, we were also satisfied with the arrangements of EuCAP 2013. The SCC venue (Swedish Exhibition & Congress Center) was very modern and practical; the collaboration with EurAAP as well as the professional conference organizers was to the satisfaction of all of us. Most important is all the positive feedback we have received from the attendees, who “even” were satisfied with the food provided by the venue restaurant, which was of high quality (the “even” refers to the fact that food is not what Sweden is most world-famous for). According to the EurAAP Chair: “EuCAP is after the Gothenburg edition, a top quality and worldwide appreciated conference.”