Patent Application
20070057862
Typically, mobile tracking and messaging antennas for mobile tracking and messaging systems, such as that used with Qualcomm Incorporated's OmniTRACS® system, are housed within a radome. A radome is an enclosed housing, usually made of a low-loss dielectric material that serves to protect antennas mounted on ground-based vehicles, ships, airplanes and the like without significantly altering the electrical performance of the enclosed antennas.
Transit buses and heavy industrial equipment having tracking and messaging systems are well suited for use with radomes. The dielectric material of the radome is usually made of a plastic material having a thickness on the order of the wavelength associated with an antenna used therewith.
Mobile tracking of equipment, such as industrial vehicles, can involve the Global Positioning System (GPS) which can be used to track vehicles using a number of low earth orbiting satellites.
While the messaging antenna is capable of movement to increase transmission and reception signal strength, the GPS antenna is stationary. In order to optimize GPS performance, it is desirable to locate the GPS antenna in clear line of sight to the GPS satellite constellation.
A method and apparatus for improving the GPS satellite reception is needed.
Applicable reference numerals have been carried forward.
In order to improve GPS satellite reception, in one embodiment, the GPS antenna is moved from the base of the ACU as shown in
With reference still to
One challenge in implementing the attachment of cable 22 and cup 16, containing patch antenna 4, to radome 8 lie in identifying a robust mount that would be able to withstand years of fatigue in an outdoor mobile application while potentially being exposed to the Earth's most extreme climates. ACU 2 is frequently deployed in harsh, inhospitable regions of the world and as such, it must operate reliably when exposed to diverse climatic conditions offered by high humidity scenarios encountered in the Amazon River basin, extreme heat typical of desserts in the American southwest and rugged terrain and winter temperatures reaching −40° C. in northern Alaska. The method of attachment would be subjected to rapid excursions in temperature, extended exposure to hot and cold extremes, and high impact stress at severe cold temperatures. Preferably, the bonding agent used for adherence would have low water absorption properties and demonstrate a high degree of radio frequency (RF) transparency over a range of frequencies.
After much experimental testing, adhesion to radome 8 was obtained using a double-sided adhesive tape. It was determined that commercially available 3M™ VHB™ 5952 tape was best suited to adhere cup 16, containing patch antenna 4, and GPS antenna cable 22 to radome 8. 3M™ VHB™ 5952 is a very high bond, double-sided acrylic foam tape. As illustrated in
The high performance tape holding the GPS antenna cup to the radome was required to demonstrate durability under a number of stringent tests. A primary goal of this testing was to observe the stress responses of the tape in order to maintain its suitability and long-term reliability in the radome mounted GPS application.
Thermal shock tests were performed to determine the ability of the high performance tape to withstand sudden changes in temperature. Specifically, vibration tests were conducted to demonstrate the capacity of the tape to withstand the dynamic stress typically encountered in a usage environment. Vibration tests over hot and cold temperatures were also performed to demonstrate the ability of the tape to survive under conditions most likely to cause tensile or shear failures.
Heavy impact tests were done to meet limited market requirements contemplated for customers concerned with vandalism. Further, aggressive side impact tests were performed to assure that a low-hanging tree branch striking the side of the radome would not result in adhesion failure.
The present embodiments are further illustrated by the following examples demonstrating the testing undergone by the foregoing described adhesive tape in which the tape held its bond during such testing. It was determined that an improved bond could be obtained using an adhesion promoter during adhesion of cup 16 and cable 22 to radome 8. Further, thermal shock testing demonstrated improved results by increasing the surface area of the affixed tape.
Accumulated Stress Test
Fifteen thermal shock cycles in an air-to-air thermal shock chamber (−50° C. to +85° C.) followed by 9 hr 5.2 (root mean squared) RMS random vibe (10-1000 Hz) and a quantity of 54, 20 G amplitude bump shocks (half sine, 11 ms).
Simultaneous Temperature and Vibration
Cold random vibration (1 hr. 5.2 gRMS, 10-1000 Hz) performed in the vertical axis while ACUs were held at 50° C. (worst case condition due to reduced tensile strength of the tape at cold temperature). Hot vibration (1 hr, 5.2 gRMS, 10-1000 Hz) performed in the horizontal axis while ACUs were held at +85° C. (worst case condition due to reduced tape shear strength at high temperature).
Temperature-Humidity Cycling
−40° C. to +70° C. and 90% relative humidity (RH), 8 hr cycle, 17 day duration.
Storage Temperature Cycling
−50° C. to +85° C., 8 hr cycle, 17 day duration.
Ambient Top-Down Impact
Three strikes from a 20 oz mass hitting the radome at an impact speed of 28 mph.
Cold Top-Down Impact
Three radome strikes from a 20 oz mass dropped 12 in. (free-fall) while ACU is cold (−50°).
Ambient Side Impact
One strike from a spring-loaded bar hitting the radome at an impact speed of 25 mph.
Cold Side Impact
One strike from a spring-loaded bar hitting the radome at an impact speed of 25 mp while the ACU is cold (50° C.).
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. For example, messaging antenna 10 of
