1. Field of the Invention
The invention relates to antennas for receiving broadcast digital television signals and, more particularly, to internal dual band television antennas for small portable entertainment modules for use in vehicles and elsewhere.
2. Discussion of the Background
A wide variety of different architectures for automotive antennas exist for a number of uses. Amplified rod antennas that mount to the exterior such as on the roof of a vehicle are used for different frequency bands such as AM and FM reception. Antennas printed on windshield glass are used for reception of AM, FM, and TV signals. Antennas exist for vehicles that receive satellite signals such as GPS, XM and Sirius signals. Cell phone antennas for vehicles use also exist. Other antennas such as fractal antennas, integrated fractal patch antennas, integrated antennas, shark-fin antennas, Bluetooth and other wireless antennas exist for a multitude of applications including for use in a vehicle.
For some time, small entertainment modules having monitors for viewing programming such as from DVDs and the like have been used internally in vehicles. Recently, these small modules are of a portable design which can be used within the vehicle or remotely there from and are small enough to be hand held. A need exists to receive broadcast television signals over the very high frequency (VHF) and ultra high frequency (UHF) bands in such small portable entertainment modules.
U.S. Pat. No. 7,084,833 B2 shows a portable television having antennas extending outwardly on either side of the screen. This antenna design increases the size of the portable television. U.S. Patent Publication No. 200710096994 provides antennas in speaker enclosures also extending from the sides of the television. Here, the two separate antennas are installed differently so their directions are 90 degrees apart. Another need exists to have the television antenna internal to the housing of the television without extensions on either side.
U.S. Patent Publication No. 2009/0153424 A1 sets forth use of an inverted L-shaped folded antenna for reception of VHF and UHF broadcast signals in a miniature receiver terminal. The antenna is placed on a separate substrate that is, for example, 100 mm by 200 mm in size. Other separate dual band television antennas are also commercially available for mounting inside portable entertainment modules including small chips such as 150 to 200 square mm in area. A further need exists to provide an internal dual band antenna for receiving broadcast television signals not confined to a small chip and that is large enough to take advantage of the size and shape of the module to improve reception.
The form factor for such small portable entertainment modules provides a set of design limitations that are critical in the concept and implementation of an internal television antenna design. The main design limitation comes from the wave length shortening due the size constraint which in most cases is greater than 20 times. A second design limitation comes from the shape used for the antenna inside the module. The shape is limited by the module design itself and the arrangement and placement of various components, air vents, and other physical structures that can be in close proximity to the antenna. A third design limitation concerns the materials used for the antenna that often requires special technologies for printing and etching. A further need exists to provide an internal antenna or a set of internal antennas within the confines of a small portable entertainment module that addresses these three design limitations and that provides maximum gain over the UHF and VHF frequency bands, especially for digital television (DTV) broadcast signals, so that the module can be used in or out of a vehicle.
The dual band internal television antenna of the invention is designed for a portable entertainment module having a screen with a bezel around the screen and that meets the needs described above. The dual band internal television antenna has a first antenna element in the bezel that extends around and in the bezel a first length and a second antenna element in the bezel spaced from and parallel to the first antenna element that also extends a second length in the same direction as the first antenna element. The first and second signal outputs from the two elements are located at the same internal position on the bezel. The lengths of the first and second antenna elements are chosen to compensate for the reception influences caused by said portable entertainment module, materials used and components contained therein and to maximize reception of the television broadcast signals. The first antenna element is tuned to receive VHF and the second antenna element is tuned to receive UHF broadcast signals based on the antenna design, the materials used for the antenna, the shape and size of the module, and the location of various components in the module such as electronics, metal, air vents, etc.
A rear dual band internal television antenna for the portable entertainment module also meets the needs described above. The rear television antenna is a logo-periodic planar antenna printed on a substrate sized to fit in the substantial cross-section of the module and modified to be placed around environmental openings in the substrate. The modified logo-periodic planar rear antenna on the substrate is affixed inside the rear of the housing with the environmental openings accommodating components, air vents and other physical structures.
The method of the invention receives VHF/UHF digital broadcast television signals in a portable entertainment module with a dual band front internal antenna embedded in the module around a display screen. The rear dual band internal antenna may also be used in the rear of the housing. The rear antenna has elements modified in shape to have environmental openings to fit around components, vents and the like inside the housing. The signal output from the front and rear internal antennas are combined together.
The summary set forth above does not limit the teachings of the invention especially as to variations and other embodiments of the invention as more fully set out in the following description taken in connection with the accompanying drawings.
a sets forth the details of the rear antenna as printed on a substrate.
b is a table showing the dimensions for the rear antenna of
a sets forth the connection circuitry combining the received signals from the pair of antennas.
b sets forth the connection circuitry using a switch to select the received signals from the front or rear antenna.
a is a performance plot of the front antenna.
b is a performance plot of the rear antenna.
c is a performance plot of the combined front and rear antennas.
While the module 10 has a number of entertainment uses (such as playing games, DVDs, etc.), one use is to receive broadcast digital television signals. The present invention provides one built-in antenna, in one embodiment, or a pair of built-in antennas of different architectures, in another embodiment to receive such broadcast digital television signals.
The module 10 has a touch screen 60, controls 70 and a surrounding bezel 80 as part of the housing 90. The bezel 80 acts as a rim around the touch screen 60 at the front 92 of housing 90. As will be discussed later in more detail, the bezel 80 contains an embedded front antenna generally located around the screen 60 and hidden from view. The use of the front antenna (i.e., an internal dual band television antenna) in the bezel 80 is one embodiment of the invention. While the term “bezel” is used herein, it is to be understood that any rim (or other peripheral structure) around the screen display of a module 10 could contain the front antenna. The term “screen” includes not only a touch screen, but any suitable display such as a conventional TV screen, video monitor, etc.
The housing 90 optionally contains a rear antenna (i.e., an internal dual band television antenna) located within the rear 94 inside of the housing 90. The use of the rear antenna in the rear 94 in combination with the front antenna is a second embodiment of the invention.
Each of the two internal dual band antennas is designed to accommodate the physical dimensions and shape of the housing 90 and to provide maximum gain over the very high frequency (VHF) and ultra high frequency (UHF) frequency bands. Both antennas implement specific and different architectures to achieve the best VHF/UHF reception of electromagnetic waves with different polarization over the two wide frequency bands. Preferably, a high gain dual spiral antenna is implemented in the bezel 80 of the housing 90 as the front antenna and a modified logo-periodic planar antenna is implemented inside the rear 94 of the housing 90 as the rear antenna. In one embodiment only the high gain dual polarization spiral front antenna is used. In another embodiment both front and rear antennas as a set are used.
In
Each element 100A and 100B is preferably a wire made of conductive material. The conductive material is preferably copper, aluminum, or brass and the wire is preferably about one millimeter in diameter. The spacing 102 between elements 100A and 1008 is small such as preferably about two millimeters. In other variations, conductive material could be deposited on a surface of the bezel or other surface rather than using wires. Wires, however, are more rigid and easier to work with.
As shown in
The front antenna 100 fits into the small module 10 (approximately 262×171 mm), within the bezel 80, around the periphery of the screen 60. This provides a small aperture that is about 20× shorter than the wave lengths for receiving VHF/UHF signals. As an example, the lower VHF wave length is about 6 m and the higher wave length is about 1.2 m, i.e. the shortening wave coefficient is about 25 times considering the largest antenna dimension at the lower antenna band. The UHF lower side wave length is 0.666 m and the higher end 0.353 m which is about 1.4 times wave shortening factor in the higher end of the antenna operation frequency band. The front antenna 100 must also topologically fit into the size and shape of the bezel 80 of the housing 90 without interfering with use of the touch screen 60 by a user.
The front antenna 100 uses two elements 100A and 100B as shown in the embodiment of
For a better understanding of the front antenna 100 configurations and tuning,
All other dimensions in millimeters are shown for the front antenna embodiment in
The high gain dual polarization internal front antenna 100 is implemented around and behind the front LCD glass 60 in the bezel 80 at the front of the module 10. The design is a modified dual-arm spiral antenna topology and is positioned in the bezel 80 behind the front glass 60 to provide high gain and wideband polarization independent frequency performance. The change of polarization is an issue in mobile environments and can be noted often in the portable module 10 use due either to improper or limited holding positions. The DTV transmission is horizontally polarized in its majority of occurrences. The spiral antenna arms 100 are located along the X and Y coordinates to cover the change of the polarization. Therefore the front antenna 100 is designed to provide maximum gain due the critical dimension change in times to the wavelength while receiving signal with inconsistent polarization. The way the polarization independence works is because the antenna 100 has an active region where the antenna feed is attached and that region corresponds to the rotation of the pattern along the arms 100A, 1008 of front antenna 100. The received pattern corresponds to the direction of the spiral arms and exhibits a peak on the horizontal and vertical axis. Typically the pattern is broad and the gain slightly more than that of a dipole.
In summary, the front internal dual band antenna 100 architecture of this embodiment comprises a first spiral antenna element 100A having a first length that extends in one embodiment around the bezel 80 from a first signal output 110A and a second spiral antenna element 100B parallel to, but spaced from, the first spiral antenna element 100A that extends around and embedded within the bezel 80 from a second signal output 110B in the same direction as the first spiral antenna element 100A. The first and second signal outputs 110A, 1108 are at the same position on the bezel 80 near the bottom center 82; however, any suitable position around the bezel 80 could be used. The first element 110A is longer than the second element 110B and the elements 110A, 1108 have lengths that are tuned to provide optimum VHF/UHF antenna performance based on the size and shape of the module 10, materials used for the antenna 100 and the reception influences caused by said portable entertainment module such as: the housing 90, the screen 60, and any nearby metal and electronic components.
A method of receiving television broadcast signals is also set forth above and in summary includes the steps of: receiving television broadcast signals in a first antenna element 110a, embedded in the housing 90 around the display screen 60, having a length tuned (1) to receive very high frequency broadcast television signals and (2) to compensate for reception influences caused by said portable entertainment module; receiving the television broadcast signals in a second antenna element 110b, embedded in the housing around the display screen and parallel to the first antenna element 110a, having a length tuned (1) to receive ultra high frequency broadcast television signals and (2) to compensate for reception influences caused by said portable entertainment module; and combining signal outputs from the first and second antenna elements 110a and 110b.
In
The MYLAR substrate 1010 has a large central formed environmental opening 1020. The signal output 1030 is shifted towards one side because of the environmental opening 1020. The log periodic rear antenna 1000 is modified to have environmental openings such as opening 1020 to fit around venting, components and other circuitry within the module 10. Elements 1040A and 1040B are substantially shortened to adapt to the requirements of environmental opening 1020 in substrate 1010. Likewise, elements 1050A and 1050B are somewhat shortened to accommodate air vents within the module 10. All elements 1060A and 1060B are substantially shortened to fit near an inside wall of the module 10 as explained in more detail with respect to
Printed circuit board 1200 contains conventional circuitry (not shown) which processes the VHF/UHF signals from outputs 1030A and 1030B and which provides the processed signal outputs at 1510A and 15108. The signal output connectors 1510A, 1510B are fitted into the formed window 1500 of the MYLAR sheet 1010.
In
At the four corners of the antenna 1000 are more formed environmental openings 1100, 1110, 1120, and 1130 that further modify the shape of the rear antenna 1000 as discussed above for
The geometry of the logo-periodic rear antenna 1000 is chosen for its electrical properties that repeat periodically with the logarithm of the frequency. The logo-periodic antenna design approach is also known as a frequency independent approach. A properly designed logo-periodic antenna pattern provides wide frequency reception. The rear antenna 1000 is connected to the feed via PCB assembly and a balun transformer (not shown) for impedance normalization.
The rear antenna gain chart for the above embodiment is shown in
In summary, the rear antenna 1000 architecture of this embodiment is a logo-periodic antenna printed on a substrate that is modified to fit inside the housing 90 with environmental openings over rear vents and over other components and structures. The modified logo-periodic antenna 1000 is affixed inside the rear 94 of said housing 90 with the environmental openings over vents and other components. In its best mode the invention uses the rear antenna 1000 in combination with the front antenna 100 to compensate the gain loss from the influence of large metal body components in or on the module 10.
One embodiment of connection circuitry for operatively connecting the signal outputs of each antenna 100, 1000 together is shown in
The outputs 110A, 1108 of the front antenna 100 are connected to an impedance matching circuit 1600A located on printed circuit board (PCB) 140. The circuit 1600A has a 4:1 Balun transformer 1620A for matching the 200 ohm balanced impedance on outputs 110A, 110B to a 50 ohm unbalanced output 1610A.
The outputs 1030A, 1030B of the rear antenna 1000 are connected to an impedance matching circuit 1600B located on printed circuit board 1200. The circuit 1600B also has a 4:1 Balun transformer 1620B for matching the 200 ohm balanced impedance on outputs 1030A, 1030B to a 50 ohm unbalanced output 1610B.
The television output signal from match circuit 1600A is delivered from output 1610A and the television output signal from match circuit 16006 is delivered from output 1610B to conventional combining circuit 1640, in one of its embodiments, having resistors R1 (100 ohms) and R2 (70.5 ohms). The combining circuit 1640 combines the 50 ohm signals from the antennas 100, 1000 together for delivery of a combined television signal over output 1660 to the digital television receiver (not shown) within the module 10. In addition that circuit may include compensation components for any phase and impedance misalignments of the received signal from the two antennas. In another embodiment the combining circuit 1200 may implement an antenna decision directed diversity circuitry. In another embodiment as shown in
A number of different circuits can be used to connect the two antennas together and/or to provide impedance matching for each individual antenna. The signal 1660 from the antennas 100 and 1000 is fed to a dual band TV tuner front-end via conventional VHF and UHF filters (all not shown). The filters are designed to reject all out of band signals with better than 40 dB and have better than 1.5 dB very low in band ripple and insertion loss.
The dual DTV front end incorporates two LNAs for the VHF (40-245 MHz) band and UHF (470-862 MHz) band. Each LNA has 4 gain modes, which are 18 dB, 7 dB, −3 dB and −21 dB typically. The signals are then fed to an AGC amplifier (not shown) with 36 dB gain controlled with 0.5 dB step. All of this is of conventional design and can vary based on design requirements.
A pair of VHF/UHF internal antennas 100, 1000 exhibiting different architectures for a portable entertainment module having a housing and a display screen has been presented above. As shown in
What has been described above is the provision of two internal dual band antennas, in one embodiment of the invention, wherein each internal antenna is of a different antenna architecture: a spiral front antenna 100 and a logo-periodic rear antenna 1000. It is to be understood, that other antenna architectures could be utilized to provide the pair of antennas. For example, the architecture for the rear antenna could include a frame, loop, fractal, dipole, etc. antenna modified to fit within the inside rear of the module 10. Likewise, the front antenna could include any suitable architecture that does not interfere with use of the screen 60. The VHF/UHF output signals from the pair of different antennas 100, 1000 are combined together for use.
The method of using a pair of antennas is shown in
a and 19b show the frequency plots of the front (
The above described antennas may be embodied in other specific forms, shapes and architectures based on the teachings herein. Further, certain precise dimension values have been utilized in the specification. However, these dimensions, either precisely stated or stated with the word “about”, do not limit the scope of the claimed invention and that variations in lengths, spacings, environmental openings, shapes, and configurations can occur.
It is noted that the terms “preferable” and “preferably,” are given their common definitions and are not utilized herein to limit the scope of the claimed disclosure. Rather, these terms are intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure.
For the purposes of describing and defining the present disclosure it is noted that the term “substantially” is given its common definition and it utilized herein to represent the inherent degree of uncertainty that may be attributed to any shape or other representation.
Those skilled in this art will appreciate that various changes, modifications, use of other materials, other structural arrangements, and other embodiments could be practiced under the teachings of the invention without departing from the scope of this invention as set forth in the following claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/287,310 filed Dec. 17, 2009.
Number | Date | Country | |
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61287310 | Dec 2009 | US |