William E. McKinzie

A low profile polarization diversity antenna built on an artificial magnetic conductor

We introduce a low profile antenna system appropriate for polarization diversity. It is a two-port, linearly polarized antenna consisting of two orthogonal bentwire monopoles placed in close proximity to an artificial magnetic conductor. This compact antenna, only /spl lambda//50 in total height, is appropriate for many mobile wireless systems where diversity gain is desired for high data rate communications. Furthermore this antenna is directive into one hemisphere, with a good front to back ratio, allowing it to be placed directly on a lossy dielectric body without significantly compromising the radiation efficiency or VSWR.

TM mode analysis of a Sievenpiper high-impedance reactive surface

Builds on the published work of King and Park [see IEEE Trans. Ant. Propag., vol AP-31, p. 471-6, 1983] in which they analyze TM modes on a Fakirs grounded bed-of-nails structure. Sievenpipers reactive surface is essentially a Fakirs structure with the addition of a capacitive FSS loading the ends of the rods. In this analysis, we show that an infinite number of TM modes can exist on this structure, and that the apparent TM mode cutoff, experimentally observed, is a manifestation of the two lowest order modes coalescing, and then being cut off. Furthermore, we show that this apparent TM mode cutoff can be adjusted independent of the +90/spl deg/ reflection phase frequency by controlling the density and diameter of the rods.

AMCs comprised of interdigital capacitor FSS layers enable lower cost applications

The focus of this work was to reduce manufacturing costs of printed artificial magnetic conductors (AMCs) by employing interdigital capacitors to enhance the effective sheet capacitance of the FSS without resorting to a second layer of overlapping patches. A 2.8 GHz AMC was fabricated and tested to demonstrate the concept. This AMC was then used to demonstrate a 2.9 GHz low profile antenna. Cost savings for this alternative manufacturing technique are estimated to be at least 50%.

A 10 MHz to 100 GHz LTCC CPW-to-stripline vertical transition

A broadband 50Ω coplanar waveguide (CPW)-to-stripline transition is presented which is capable of operation up to 100 GHz. This vertical transition is fabricated in low-temperature co-fired ceramic (LTCC), and it is appropriate for system in package (SiP) module packaging. It was designed for wafer probing an LTCC module containing an embedded stripline. This compact transition occupies only two layers of nominal 5 mil thick tape. Both simulated and measured s parameter results are shown for back-to-back transitions up to 110 GHz. Measured insertion loss for a single transition is less than 0.3 dB near 60 GHz and less than 1 dB up to 100 GHz.

Simulation of artificial magnetic materials using lattices of loaded molecules

Present are numerical studies of the magnetic permeability for arrays of artificial magnetic molecules simulated using a time domain TLM code. These artificial magnetic materials consist of a 3D periodic lattice of electrically small loaded loops suspended in a non-magnetic host medium. For this class of artificial magnetic media, we demonstrate good agreement between the permeability computed using a simple circuit theory model, and that computed using a full wave TLM simulation. This close agreement suggests that the salient physics for this type of artificial magnetic media may be well modeled using simple lumped equivalent circuits. A closed form expression is derived for the effective media permeability as a function of the molecular circuit loads. When molecules are uniformly loaded with lossless capacitors, the artificial media exhibits a Lorentzian response with a resonance ((mu) r yields (infinity) ) below which the media is paramagnetic ((mu) r > 1) and above which the media is diamagnetic ((mu) r < 1). Resonant frequency, and magnetic permeability, can be adjusted by controlling the load capacitance.

60 GHz patch antenna in LTCC with an integrated EBG structure for antenna pattern improvements

We present a 60 GHz LTCC aperture-coupled patch antenna with an integrated Sievenpiper EBG structure used for suppression of TM mode surface waves. This is believed to be the first demonstration of a Sievenpiper EBG structure used inside a millimeterwave LTCC antenna. The merit of this EBG structure is to yield a predicted 6 dB improvement in broadside directivity. Without the EBG structure, edge diffraction of surface waves degrades the pattern into two main beams. The combination of a new LTCC material system (DuPont 9K7 GreenTape™) along with laser ablation processing for fine line and fine slot definition allowed the integration of a successful EBG structure with an aperture coupled patch antenna.

60-GHz

This letter presents a 60-GHz 2 × 2 low temperature co-fired ceramic (LTCC) aperture-coupled patch antenna array with an integrated Sievenpiper electromagnetic band-gap (EBG) structure used to suppress TM-mode surface waves. The merit of this EBG structure is to yield a predicted 4-dB enhancement in broadside directivity and gain, and an 8-dB improvement in sidelobe level. The novelty of this antenna lies in the combination of a relatively new LTCC material system (DuPont Greentape 9K7) along with laser ablation processing for fine line and fine slot definition (50-μm gaps with +/ - 6 μm tolerance) allowing the first successful integration of a Sievenpiper EBG structure with a millimeter-wave LTCC patch array. A measured broadside gain/directivity of 11.5/14 dBi at 60 GHz is achieved with an aperture footprint of only 350 × 410 mil2 (1.78λ × 2.08λ) including the EBG structure. This thin (27 mil) LTCC array is well suited for chip-scale package applications.

2 \times 2

Although Bluetooth and IEEE 802.11b radios each utilize spread spectrum modulation techniques in the 2.4 GHz ISM band, these two wireless standards still interfere with each other when located on the same platform such as a laptop computer. In order to diminish interference, it is advantageous to use two antennas with low mutual coupling. This may be achieved by locating an artificial magnetic conductor (AMC) that suppresses surface currents over a band of frequencies between the antennas. We have demonstrated that an AMC can be used as a reactive edge treatment to isolate two 2.4 GHz antennas by 45 dB on a surrogate laptop.

LTCC Patch Antenna Array With an Integrated EBG Structure for Gain Enhancement

This paper presents characterization of low temperature co-fired ceramic (LTCC) based electromagnetic bandgap (EBG) structures, and a test method to measure the TM mode cutoff frequency at millimeter wave frequencies. This test method differs from prior art in that the TM mode surface wave launchers are fabricated in the same LTCC module as the EBG structure under test to realize a compact and repeatable test vehicle. A pair of two port transmission measurements will experimentally yield the TM mode cutoff frequency. This frequency defines the lower bound for the surface wave bandgap. The TM mode cutoff frequency is a very important parameter where EBG structures are integrated into millimeterwave LTCC antennas because this cutoff frequency must be lower than the antennas operational frequency range. This proposed test method may be used with any open EBG structure which exhibits a TM mode cutoff frequency.

AMC edge treatments enable high isolation between 802.11b and Bluetooth/spl trade/ antennas on laptop computers

Reported for the first time are experimental results of surface wave coupling for a Sievenpiper artificial magnetic conductor (AMC) which has an R-Card attached to its surface. The addition of in-plane resistive loss causes the TE surface wave to undergo broadband absorption at frequencies above the normal cutoff frequency of the strictly reactive AMC. Also the TM mode cutoff frequency is reduced with the use of R-card treatments. These two factors create a broader bandwidth for surface wave suppression.