Angus C.K. Mak

Isolation Enhancement Between Two Closely Packed Antennas

This paper introduces a coupling element to enhance the isolation between two closely packed antennas operating at the same frequency band. The proposed structure consists of two antenna elements and a coupling element which is located in between the two antenna elements. The idea is to use field cancellation to enhance isolation by putting a coupling element which artificially creates an additional coupling path between the antenna elements. To validate the idea, a design for a USB dongle MIMO antenna for the 2.4 GHz WLAN band is presented. In this design, the antenna elements are etched on a compact low-cost FR4 PCB board with dimensions of 20times40times1.6 mm3. According to our measurement results, we can achieve more than 30 dB isolation between the antenna elements even though the two parallel individual planar inverted F antenna (PIFA) in the design share a solid ground plane with inter-antenna spacing (Center to Center) of less than 0.095 lambdao or edge to edge separations of just 3.6 mm (0.0294 lambdao). Both simulation and measurement results are used to confirm the antenna isolation and performance. The method can also be applied to different types of antennas such as non-planar antennas. Parametric studies and current distribution for the design are also included to show how to tune the structure and control the isolation.

Reconfigurable Multiband Antenna Designs for Wireless Communication Devices

New designs for compact reconfigurable antennas are introduced for mobile communication devices. The uniqueness of the antenna designs are that they allow various groups of their operating frequency bands to be selected electronically. In particular, each group of frequency bands, or mode, can be made to serve several different communication systems simultaneously. These systems may include various combinations of GSM, DCS, PCS, UMTS, Bluetooth, and wireless local-area network (LAN). Therefore, by electronically selecting different antenna modes, a variety of communication systems can be conveniently served by only one antenna. One advantage is that through the different operational modes, the total antenna volume can be reused, and therefore the overall antenna can be made compact. In these designs, the selection of the different modes is achieved by either i) switching different feeding locations of the antenna (switched feed) or ii) switching or breaking of the antennas connection to the ground (switched ground). This paper demonstrates these two designs. For the first design of switched feed, it can support GSM, DCS, PCS, and UMTS. In the second design, the antenna makes use of a switched-ground technique, which can cover GSM, DCS, PCS, UMTS, Bluetooth, and 2.4 GHz wireless LAN. The designs are investigated when ideal switches and also various realistic active switches based on PIN diodes, GaAs field effect transistor, and MEMs configurations. The designs are verified through both numerical simulations and measurement of an experimental prototype. The results confirm good performance of the two multiband reconfigurable antenna designs.

Low Cost Reconfigurable Landstorfer Planar Antenna Array

In this paper, we introduce a practical design for a Landstorfer planar antenna that can be implemented as a compact and low cost reconfigurable planar antenna array. The array, we propose, can have 360-degree coverage in azimuth and allows a wide variety of directive beams to be electronically selected while maintaining a simple structure, ease of manufacture and low cost with high efficiency. One of the possible applications for this array is in WLAN systems where high gain and low cost adaptable antennas promise increases in capacity and coverage. The array design utilizes key innovations in the design of Landstorfer antennas and feed/switching network. The Landstorfer antenna exhibits a high gain with 9.5 dBi and low mutual coupling between elements. A proposed reflector for the Landstorfer antenna is implemented and it allows the antenna array to be fabricated on a 2-layer PCB board. We also present a low cost feed/switching network which allows flexible control of the antenna patterns. The design makes use of PIN diodes as switching elements and a resonant inductor to improve the isolation of the PIN diodes. By integrating the antenna elements, feed/switching network and array configuration, a low cost reconfigurable Landstorfer planar array can be formed.

Compact low cost dual polarized adaptive planar phased array for WLAN

In this paper, we introduce a design for a compact low cost dual polarized adaptive planar phased array for Wireless Local Area Networks (WLAN). The uniqueness of the design is that a wide variety of beam shapes can be electronically selected from a large set of possible patterns while maintaining compact size low cost with reasonable efficiency and having independent dual diversity ports. An important application of the array is in WLAN systems where compact and low cost adaptable antennas promise increases in capacity and coverage. The array design makes use of key innovations in the antenna element and feed network, along with improved low cost phase shifting circuits with low loss performance. The compact antenna element we propose exhibits low mutual coupling between elements with good bandwidth and dual polarized diversity feeds. The feed network is designed to minimize coupling between ports while the phase shifters are low cost but allow flexible control of the antenna patterns. The design is verified both through numerical simulations and also measurements of an experimental prototype and these confirm the good performance of the antenna system and suitability for use in WLAN systems.

High power performance for reconfigurable multi-band mobile antenna

Reconfigurable multi-band antenna is one of the promising techniques to shrink the overall size of the antenna for mobile communication. They can allow various groups of their operating frequency bands to be selected electronically in order to reuse the antenna volume. The concept is that each operating band resonates on the portion of or the entire antenna geometry such that there is almost no extra size required to create multi-band characteristics. One of the reconfigurable multi- band antennas is by changing the location of the feeding point which is reported. To realize the reconfigurable antenna, the active switches have to be used. Obviously, the overall performance of the design does not only rely on antenna design, but also on the proper selection of the active switches. In this paper, we will report compact reconfigurable multi-band antenna (Switched feed) using different type of active switches and compare the performance especially, high power performance.

A low-cost dual-polarized wideband antenna

In this paper, a low-cost dual-polarized wideband base station antenna is presented. The antenna element can cover the frequency band from 1900 to 2700MHz. The results in this antenna design demonstrate that it is more cost-effective and can simplify the manufacturing process. The antenna consists of only one double-size PCB and two single-layer PCBs. It shows that the antenna element can provide more than 9dBi peak gain, 30dB isolation, 15dB co-cross polar ratio and preserve the symmetry of antenna pattern.