Alan E. Waltho

Multi-Radio Coexistence: Challenges and Opportunities

In this paper, we study the emerging heterogeneous multi-radio network, focusing on interference issues due to simultaneous operation of multiple radios. A comprehensive review is given on the sources of coexistence interference, including transmitter noise, receiver blocking, and inter-modulation. We compare various coexistence techniques, and relevant standardization efforts. Then, we propose a media independent coexistence service (MICE) layer, and suggest that the performance of a multi-radio system can be further improved if necessary support and modification is added to individual wireless technology, e.g. air interface / wireless protocols. Specifically, we show that the proposed coexistence-aware TXOP adaptation achieves up to 50% improvement of the transmission efficiency in a WiFi/Bluetooth dual-radio device, where the 802.15.2 PTA (packet traffic arbitration) technique is used for coexistence.

A UWB antenna with a stop-band notch in the 5-GHz WLAN band

A new UWB antenna, the sail-boat antenna, is proposed that provides a stop-band notch in the 5-GHz WLAN band. The CPW-fed sail-boat antenna offers a compact planar structure. Measured results for input impedance, VSWR, patterns, and gain demonstrate that the antenna provides the stop-band notch of 11/spl sim/13.5 dB in the WLAN band.

A novel CPW-fed disc antenna

Many disc antennas have been proposed for ultra-wideband (UWB) applications, but they suffer from the disadvantages of requiring a large ground plane and a complicated feed structure. This paper reports on a new and novel coplanar waveguide (CPW) fed disc antenna. Measured data show that the antenna provides more than a 3:1 bandwidth covering the frequency range of 2.4 /spl sim/ 10.9 GHz for the tested prototype. Radiation patterns are dipole-like omnidirectional patterns with half power beam width (HPBW) values of 60/spl deg/ /spl sim/ 70/spl deg/. Maximum gain is about 2 /spl sim/ 4 dBi over the bandwidth. The antenna has a good impulse response with less than 1 nanosecond pulse width and linear phase over a broad bandwidth. The CPW-fed disc antenna is a promising antenna element for UWB applications.

A novel broadband antenna, the low profile dipole planar inverted cone antenna (LPdiPICA)

A new broadband dipole teardrop antenna, the LPdiPICA (low profile dipole planar inverted cone antenna), is proposed for wireless communication applications. The antenna element has the shape of dual teardrops printed on a dielectric material. The element is backed with a finite ground plane for a high gain unidirectional pattern. The antenna is linearly polarized and provides more than 10:1 impedance bandwidth and 2.2:1 pattern bandwidth. The HPBW (half power beam width) of the antenna is 50/spl deg/-60/spl deg/ and 70/spl deg/-90/spl deg/ in the E- and H-planes, respectively, and a maximum gain of 6-10 dBi over the bandwidth. The dipole teardrop antenna is modeled as made up of wire and tapered slot antenna components that operate in the lower and upper bands, respectively.

Evolution of broadband antennas from monopole disc to dual-polarized antenna

The demand for broadband wireless communication is rapidly increasing due to the need to support more users and to provide more information with higher data rates. Wideband antennas are essential front-end elements for broadband wireless communications. In several applications, it is also desirable for broadband antennas to have dual-polarization, especially for advanced wireless communication systems employing diversity and MIMO techniques. Most broadband antennas reported in the literature are forms of monopole, dipole, or crossed-dipole antennas. This paper summarizes broadband antennas and proposes an evolution process from the monopole disc antennas to broadband dual-polarized antennas

A miniaturized dual-band dipole antenna with a modified meander line for laptop computer application in the 2.5 and 5.25 GHz WLAN band

In this paper, a reduced size dual-band balanced antenna is presented and tested in a lid of a laptop computer. The antenna size is only 0.28 lambda0, which is 44% smaller than the conventional dipole antenna and is comparable to the size of unbalanced antenna. A modified meander line technology is used in the particular antenna configuration to achieve dual-band operation in the 2.5 and 5.25 GHz WLAN bands

Bandwidth improvement for crossed-dipole type antennas using a tuning plate

Significant bandwidth improvement is achieved on the crossed-dipole antenna using the tuning plates. The tuning plate was tested on the foursquare and fourpoint antennas. The test models demonstrate that a tuning plate increases the bandwidth of crossed-dipole type antennas up to 25% over that for the same antenna without the tuning plate. The foursquare and fourpoint antennas with the tuning plate are good candidates for dual-polarized, multi-functional antenna applications and for MIMO systems.

A generalized crossed dipole antenna, the Fourtear antenna

A generalized form of a crossed dipole antenna, the Fourtear antenna, has been designed and tested. The Fourtear antenna is a promising dual-polarized broadband antenna element. The antenna consists of four identical teardrop elements, but the horizontal elements are positioned perpendicular to the vertical elements. The radiating element is printed on a dielectric material that is backed with a finite ground plane to achieve a high-gain unidirectional pattern. The antenna provides more than 10:1 impedance bandwidth and 2:1 pattern bandwidth for each feed position. The radiation patterns are unidirectional patterns with HPBW (half-power beam width) values of 50/spl deg//spl sim/ 60/spl deg/ and 70/spl deg//spl sim/ 90/spl deg/ in the E- and H-planes, respectively. The peak gain is between 7 to 11 dBi over the full bandwidth. The antenna characteristics are not identical for each feed position due to the asymmetric antenna geometry. This paper provides the fundamental ideas on how to design a dual-polarized broadband antenna.