Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
1996-07-31
2001-08-21
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S792500
Reexamination Certificate
active
06278414
ABSTRACT:
RELATED APPLICATIONS
This application is related to a commonly owned Patent Application filed on even date herewith and entitled “Dual-Band Coupled Segment Helical Antenna”, and having Ser. No. 08/690,117, and a second patent application Ser. No. 08/640,298, entitled “Coupled Multi-Segment Helical Antenna,” filed on Apr. 30, 1996. The full disclosure of each of these applications is incorporated herein by reference as if reproduced in full below.
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates generally to helical antennas and more specifically to a helical antenna having bent-segment radiators.
II. Field of the Invention
Contemporary personal communication devices are enjoying widespread use in numerous mobile and portable applications. With traditional mobile applications, the desire to minimize the size of the communication device, such as a mobile telephone for example, led to a moderate level of downsizing. However, as the portable, hand-held applications increase in popularity, the demand for smaller and smaller devices increases dramatically. Recent developments in processor technology, battery technology and communications technology have enabled the size and weight of the portable device to be reduced drastically over the past several years.
One area in which reductions in size are desired is the device's antenna. The size and weight of the antenna plays an important role in downsizing the communication device. The overall size of the antenna can impact the size of the device's body. Smaller diameter and shorter length antennas can allow smaller overall device sizes as well as smaller body sizes.
Size of the communication device is not the only factor that needs to be considered in designing antennas for portable applications. Another factor to be considered in designing antennas is attenuation and/or blockage effects resulting from the proximity of the user's head to the antenna during normal operations. Yet another factor is the desired radiation patterns and operating frequencies.
An antenna that finds widespread usage in satellite communication systems is the helical antenna. One reason for the helical antenna's popularity in satellite communication systems is its ability to produce and receive circularly-polarized radiation employed in such systems. Additionally, because the helical antenna is capable of producing a radiation pattern that is nearly hemispherical, the helical antenna is particularly well suited to applications in mobile satellite communication systems and in satellite navigational systems.
Conventional helical antennas are made by twisting the radiators of the antenna into a helical structure. A common helical antenna is the quadrifilar helical antenna which utilizes four radiators spaced equally around a core and excited in phase quadrature (i.e., the radiators are excited by signals that differ in phase by one-quarter of a period or 90°). The length of the radiators is typically an integer multiple of a quarter wavelength of the operating frequency of the communication device. The radiation patterns are typically adjusted by varying the pitch of the radiator, the length of the radiator (in integer multiples of a quarter-wavelength), and the diameter of the core.
Conventional helical antennas can be made using wire or strip technology. With strip technology, the radiators of the antenna are etched or deposited onto a thin, flexible substrate. The radiators are positioned such that they are parallel to each other, but at an obtuse angle to the sides of the substrate, or the eventual central antenna axis. The substrate is then formed, or rolled, into a cylindrical, conical, or other appropriate shape causing the strip radiators to form a helix.
This conventional helical antenna, however, also has the characteristic that the radiators are an integer multiple of one quarter wavelength of the desired resonant frequency, resulting in an overall antenna length that is longer than desired for some portable or mobile applications.
SUMMARY OF THE INVENTION
The present invention is a novel and improved helical antenna having a plurality of helically wound radiators. According to the invention, each radiator is formed in a bent-segment configuration. As a result, for a given operating frequency, a radiator portion of a half wavelength antenna according to the invention is shorter than the radiator portion of a conventional half wavelength antenna.
More specifically, in one embodiment, the radiators are comprised of a plurality of segments. A first segment extends from a feed network at a first end of a radiator portion of the antenna toward a second end of the radiator portion. A second segment is adjacent to and offset from the first segment, and is generally parallel thereto. A third segment connects the first and second segments at the second end of the radiator portion. As a result, the radiator is roughly U-shaped. The terms “U-shape” or “U-shaped” are used in this document to refer to a U-shape, V-shape, hairpin shape, horseshoe shape, or other similar or like shape.
An advantage of the invention is that for a given operating frequency, the radiator portion of the bent-segment antenna can be made smaller than the corresponding conventional helical antenna.
Another advantage of the bent-segment antenna is that embodiments using odd multiples of a quarter-wavelength of interest for the length, can be easily tuned to a given frequency by adjusting the length of the radiator segments by trimming the length of the second segments. The length of the segments is easily modified after the antenna has been made to properly tune the frequency of the antenna.
Yet another advantage of the invention is that its directional characteristics can be adjusted to maximize signal strength in one direction along the axis of the antenna. Thus for certain applications, such as satellite communications for example, the directional characteristics of the antenna can be optimized to maximize signal strength in the upward direction, away from the ground and toward the satellite.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
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Ogrod Gregory D.
Phan Tho
Qualcomm Inc.
Wadsworth Phillip R.
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