Directional antenna configuration for tdd repeater

This patent application is a continuation of U.S. patent application Ser. No. 11/602,455 filed on Nov. 21, 2006 which claims priority to U.S. Provisional Patent Application No. 60/738,579, filed Nov. 22, 2005 entitled “DIRECTIONAL ANTENNA CONFIGURATION FOR TDD REPEATER,” the contents of each of which are incorporated herein by reference.

The present invention relates generally to wireless communication and more specifically to an antenna configuration associated with a wireless Time Division Duplex (TDD) repeater, the antenna configuration made up of closely packaged antennas having orthogonal polarization and isolation to reduce electromagnetic coupling and to provide high directivity.

In a wireless communication node, such as a TDD repeater designed to operate with a TDD based wireless system capable of simultaneous transmission and reception of TDD packets, the orientation of the antenna units is crucial in establishing non-interfering operation as it is critical that the receiver is not desensitized by the transmitted signals. Further, enclosing antenna modules and repeater circuitry within the same package is desirable for convenience, manufacturing cost reduction and the like, but such packaging can give rise to interference problems.

In a full duplex repeater package for use in a TDD system, one antenna or set of antennae may operate with, for example, a base station, and another antenna operates with a subscriber. Since the frequency for the TDD repeater may be the same, or at least may be very close in frequency for both sides of the repeater, isolation becomes important particularly when simultaneous transmission and reception on both sides of the repeater are performed. Further, since the repeater unit houses all circuitry within a single package, it is desirable to closely position the antennae with minimal antenna-to-antenna interaction while maintaining acceptable gain and in many cases acceptable directivity. Directivity in antennae is desirable for use in links where the direction of the signal arrival will not vary, or at least will vary infrequently such as in a link from a repeater to a base station or Access Point (AP). Difficulties arise however, in that the use of antennae with high directivity requires that directional alignment with the base station or AP be performed, typically by trial-and-error manual alignment.

For ease of manufacture, an exemplary repeater should be configured such that it can be easily produced in high volume manufacturing operations using low cost packaging. The exemplary repeater should be simple to set up to facilitate easy customer operation. Additional problems arise however when packaging repeater antennae and circuitry in close proximity. First, it becomes difficult to achieve high isolation between antennae due solely to the close physical proximity even where directional antennae are used. Isolation becomes even more difficult where antennas having omni directional antenna patterns are used and where the proximity of the repeater to structures such as walls, furniture or other objects cannot be anticipated, and thus cannot be compensated for in advance due to unknown such as the final placement of the repeater module.

Simply put, as the antennae are placed closer together, the more likely the antennae will couple energy into each other, which reduces the isolation between the sides of the repeater. Maintaining an omni or semi-omni directional antenna pattern becomes difficult since overlapping radiation patterns of antennae which are placed close to each other tend to generate interference effects. Energy from the antennae can further be electrically coupled through circuit elements such as through a shared ground plane especially in configurations where multiple antennas are integrated and the ground plane is small. While the use of direction antenna can benefit the repeater in terms of increased range and reduced wireless signal variation due to Raleigh fading effects, directional antennas are not typically used for indoor applications, due to the requirement for directional alignment, which is beyond the capability or desire of the average user.

Some improvements can be obtained through cancellation or similar techniques where a version of a signal transmitted on one side of the repeater is used to remove the same signal if it appears on the other side of the repeater. Such cancellation however can be expensive in that additional circuitry is required, and can be computationally expensive in that such cancellation can result in the introduction of a delay factor in the repeater or alternatively can require the use of more expensive and faster processors to perform the cancellation function.

The present invention overcomes the above problems by providing an exemplary antenna array configuration in which two closely spaced patch antennae are combined with a dipole antenna such that one of the patch antennae can be selected depending on the orientation of the repeater package to communicate with a base station, AP, or the like, and the dipole antenna can be directed generally toward a client device such as a subscriber device, a user device, a wireless communication node, or the like. The patch antennae and the dipole antenna are orthogonally polarized to increase isolation and reduce electromagnetic coupling between the patch and dipole antennae. The antennae can be fed in a balanced configuration to reduce common mode currents. The use of multiple switched directional antennae allows for minimal user interaction during initial configuration and the repeater electronics may be utilized for automatic selection of the best directional antenna for use during initial configuration, and also periodically during operation.

The exemplary antenna configuration can include a monopole, a dipole, or another substantially omni-directional antenna element facing a client side of the repeater and two patch antennae facing the base station side of the repeater. The patch antennae are in parallel relation to each other and a substrate such as a ground plane located therebetween. The client side element can be arranged on the ground plane and, as noted, can be a monopole antenna, a dipole antenna, or the like. Either of the patch antennae can operate depending on which antenna has the best signal characteristics for communicating with a base station antenna. An isolation fence can be used between the patch antennae and the client side antenna arranged in perpendicular relation to the planes of the patch antennae and the main ground plane/circuit substrate.

It will be appreciated that placement of the repeater unit will have a large impact on determining the signal quality both toward the base station and between the repeater client or clients. Therefore, repeater performance can be analyzed and a user could be directed to reposition the repeater unit for optimum signal performance. In accordance with the present invention, the use of two or more switchable patch antennae can address the placement issue to an extent by allowing the system to select which of the patch antenna will provide the best reception toward the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages in accordance with the present invention

FIG. 1 is a diagram illustrating dipole array configurations in accordance with various exemplary embodiments.

FIG. 2 is a graph illustrating the radiation patterns of a dipole portion of an exemplary dipole array configuration with and without an isolation fence in accordance with various exemplary embodiments.

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System and method for communicating over a wireles time-division duplex channel
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