Xertex Technologies, Inc.
Proposed Microsphere TM Dual-Band In-Building Coverage Antennas

 

With competition among wireless service providers intensifying in most markets, network operators are facing increasing pressure to improve the quality of their service and to lower costs. Concerns about customer "churn" are further focusing carriers to address specific problems relating to coverage to an ever-expanding range of customers, from those who still rely upon analog cellular service to those who have entered the PCS user community and expect ubiquitous voice and data connectivity.

In addition, the trend away from higher power car phones (typically 3W transmit power) to truly mobile handsets (typically 600mW transmit power) has exacerbated coverage problems as base station receivers struggle to maintain connections with 6dB less in the up-link budget. The societal trend to ever-increasing mobility has also increased customer expectations that connections can be maintained anywhere- from the roadway to the hallway. Consequently, service providers are beginning to focus more resources on improving network coverage within buildings, where additional path loss and multipath effects virtually require the deployment of pico base stations or repeaters, with an extended signal collection scheme involving both leaky coaxial cable and indoor panel antennas. The additional 6dB link budget degradation at the higher frequency 1800 and 1900 MHz PCS systems (as compared to cellular systems operating in the 800 and 900 MHz bands) make the indoor coverage problem even more severe for PCS networks.

Service providers on three continents are already beginning to implement network improvements to address poor coverage areas, particularly in-building. In Asia, network operators in Hong Kong were among the first to focus on in-building systems, given the extreme interference and multi-path environment in which they operate. Operators like Hutchison and Hong Kong Telecom have already been deploying leaky coax systems throughout public buildings and are extending their efforts to the vast array of large private buildings on Victoria Island and neighboring Kowloon. These operators are seeking alternatives to low-gain leaky coax solutions to further improve coverage. Singapore Telecom, the second largest telecom company in Asia recently announced that they plan to spend $150 million in the next year to improve coverage and network quality on their wireless networks, and highlighted in-building coverage as a principal problem to be addressed. In Europe, the major OEMs, including Ericsson, Nokia, and Alcatel are also beginning to focus on in-building system offerings, attempting to leverage their expertise with DECT and wireless PBX-like systems that rely upon inexpensive, distributed signal collection schemes within buildings.

In North America, numerous providers have also recently indicated their growing interest in addressing indoor coverage problems. After completing their initial major urban build-outs, Sprint recognized that customer churn (principally due to poor coverage) was a particularly serious problem and that focusing on improving network coverage was critical to retaining customers. Regional Bell operators are also increasing their efforts to improve coverage, particularly indoors, both as part of their mobile wireless business as well as in connection with their fixed mobile, or wireless local loop, offerings. In Canada, Bell Mobility Canada and ClearNet are also looking to deploy in-building systems in urban cores like Vancouver, and are specifically looking for dual-band systems that could provide indoor coverage at both cellular and PCS frequencies with a single signal collection scheme.

For these operators, cost remains the most significant design parameter. While the cost associated with BTS equipment and radio channels is ever decreasing, the costs associated with deploying and maintaining networks are increasing. Installation costs are of particular concern for in-building systems where costs for punching holes in walls and wiring floors can dominate the system cost. In many cases, contractors charge upwards of $250 per "hole," making installation of an extended in-building system excessively costly for network connectivity for users of multiple services, the costs of wiring and installation are multiplied several-fold.

For such in-building installations, the preferred scenario would be the installation of a signal collection system that could accommodate multiple user services. In particular, an extended antenna and signal collection system that accommodates the range of services throughout the cellular (or GSM) and PCS (or DCS) bands would be highly preferred. With such a system, a service provider or a building owner could invest in the wiring of a building with a single antenna and cable system, collecting and distributing signals from multiple services at multiple frequency bands.

While such an in-building coverage scheme could involve a variety of radio configurations or architectures, the first requirement is an antenna that operates over the 800-900 MHz and 1.9-2.0 GHz bands. Such an antenna could either be an extreme broadband antenna, or could be a dual-band antenna with pass-bands at both cellular and PCS bands. To effectively meet the needs of the in-building coverage application, such an antenna would also have the following features:

1. relatively low profile (typically requiring some type of panel antenna, or variant of a panel antenna);
2. low cost;
3. reliable and environmentally rugged;
4. adaptable to different beam patterns and gain profiles (to accommodate the different coverage needs within buildings: eg., half-space omni-types, for large room applications; bi-directional types for hallways, etc.)

Xertex Technologies, Inc., in partnership with Sinclair Technologies, Inc., has adapted its proprietary broadband antenna technology to such a dual-band antenna product. Xertex's existing panel antenna products have proven best-in-class gain performance, with an extremely low profile. Xertex's patented designs offer elegant solutions that minimize part count and consequently minimize unit cost. Made of environmentally qualified materials, Xertex antennas also operate in a wide range of environments, from relatively sheltered indoor settings, to exposed, outdoor environments in which even factors like vibration and shock are factors. Xertex's dual-band antenna, offered as Xertex's Dualband Microsphere TM series, exhibits the following performance specs:

1. Peak Gain	3 dBi
2. Frequency range	800-2000 MHz
3. VSWR	1.5:1 (minimum performance within passband)
4. Power handling	50 Watts
5. Polarization	Linear
6. 3 dB Beamwidth	80 degrees (elevation); 240 omnidirectional (azimuth)
7. Impedance	50 Ohms
8. Dimensions
9. Connectors	Various connectors available upon request
10. Cable	Low loss, RG142, plemun rated, "pigtail"
11. Operating temperature	-40 C to +70 C
12. Storage temperature	-40 C to +70 C
Projected Price	$140.00 (retail); $77.00 preferred customer price

The Dualband Microsphere TM antenna series is based on a flared monopole (or conical monopole) design, which is known to intrinsically exhibit broad bandwidth performance. Such antennas also exhibit omnidirectional beam patterns, with fairly broad elevation beamwidths as well. The antenna is designed as two concentric cones: an inner cone, which acts as the radiative element and has a linear dimension approximating a quarter wavelength for the lowest operating frequency (in this case, about 3"), and an outer cone which acts as the ground plane for the element (the outer cone in effect tilts the ground plane up towards the radiating element and provides for an intermediate impedance match between the 50 Ohm input line impedance and the free space radiating impedance. The Dualband Microsphere TM antenna is designed for ease of construction and for low cost. Low loss dielectric foam between the radiating cone element and the ground plane cone is used to provide additional support to protect against shock and vibration.

 

 

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