The invention relates generally to radio antennas. More particularly, the invention relates to antenna reception of satellite and terrestrial re-transmitted satellite signals for mobile structures that include two or more antennas for mounting internally or externally on the mobile structure.
With reference to
In the known antenna system 1a depicted in
Both types of antenna mounting systems 1a, 1b illustrated in
The vehicle body mount (i.e. roof mount) antenna system 1b includes other maintenance, safety, and performance issues. For example, the installation of antenna 2b is located remotely with respect to LNA 6b and radio receiver 8b, which is generally considered unattractive to consumers of mobile satellite services, such as SDARS. This is true for several reasons. First, the roof mounted antenna 2b is unsightly, not only to the external observer, but also to the vehicle occupants where the RF cables 5b, 7b must be routed through the interior of the vehicle, V. Secondly, as a result of height restrictions on car carriers, truck carriers, or other vehicle carriers, an antenna 2b placed on the roof has to be below some maximum height, such that the overall vehicle height does not exceed the maximum allowable height whereby this causes a problem with being loaded on a carrier loaded on a carrier.
Thirdly, RF transmissions are often subject to multi-path fading. This is especially true of satellite transmitted signals, S. Signal blockages, or obstructed satellite signals, O (
A need therefore exists for a vehicle antenna system that provides an effective means for reception of satellite transmitted signals while reducing maintenance issues and increasing signal performance. A need also exists for a vehicle antenna system that prevents additional holes from being drilled in a vehicle's exterior shell. Even further, a need also exists for a vehicle antenna system that eliminates the need to position a relatively large, unsightly antenna on the roof of a vehicle. Yet even further, a need also exists for a vehicle antenna system that eliminates the need to locate a magnetically mounted antenna on the roof or glass of a vehicle, or to use antenna couplers on the glass of a vehicle.
The present invention relates to an antenna system for a vehicle. Accordingly, one embodiment of the invention is directed to an antenna system that includes at least one first and second antenna. The at least one first antenna is located about a first portion of a mobile structure and is capable of receiving satellite and terrestrial re-transmitted satellite signals. The at least one second antenna is located about a second portion of a mobile structure and is capable of receiving satellite and terrestrial re-transmitted satellite signals. The at least one first and second antenna receive the satellite and terrestrial re-transmitted satellite signals. Signal reception on the mobile structure is maintained by switching and/or combining the satellite and terrestrial re-transmitted satellite signals received by the at least one first and second antennas when the satellite and terrestrial re-transmitted satellite signals being received by the at least one first or second antenna is obstructed.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
The above described disadvantages relating to
Essentially, the antennas are strategically located in the vehicle, V, in a fashion such that the antennas are looking up toward the satellite 11. For example, in SDARS applications, the antenna typically looks up at the satellite 11 at a minimum angle of approximately 20° for satellite signal reception while seeking terrestrial re-transmitted satellite signals that are re-broadcast by a repeater at an angle approximately equal to 0°. Accordingly, it is preferable to position the antenna relating to the antenna system 10 above the terrestrial transmission horizon such that any metallic obstructions on the vehicle, V, do not create signal loss.
As illustrated, the antenna system 10 comprises at least two or more antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b mounted internally or externally on the surface of a mobile structure, such as a vehicle, V, for reception of satellite and terrestrial re-transmitted satellite signals, S. The antenna system 10 comprises at least two antennas, which may correlate to antenna pairs 12, 14, 16, and 18. Although the antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b correlate to the antenna pairs 12, 14, 16, and 18, the antenna system 10 does not necessarily operate in pairs; it is contemplated that any desirable amount of antennas may be employed, such as, for example, two, three, four, five or more antennas to achieve the desired signal reception for maximized output performance.
As illustrated, each antenna pair 12, 14, 16, 18 is positioned in a generally symmetrical pattern at the front, F, or rear, R, about the vehicle, V, such that the antennas are mounted within or exteriorly on the vehicle, V. Although not required, it is preferable to locate the antennas at the opposing front, F, and rear, R, portions of the vehicle, V; however, a pair of complementary antennas may be located in a single housing or package (not shown) because the minimum distance the antennas may be separated by is at least one ¼ wavelength, which may be a very nominal distance in view of higher SDARS-type frequencies. In particular, this applies to a terrestrial signal application such that two antennas of the same polarization may be spaced at least ¼ wavelength apart, or two antennas of opposite polarization (i.e. vertically polarized and horizontally polarized antennas) may be placed in the same location. As illustrated, the antennas 12a, 14a, 16a, 18a, (i.e. “the antennas”) are located at the front, F, of the vehicle, V, and the antennas 12b, 14b, 16b, 18b (i.e. “the b antennas”) are located at a rear, R, of the vehicle, V. Even further, although the antennas pairs 12, 14, 16, 18 are shown to be positioned in a generally symmetrical pattern about the vehicle, V, the antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b may be positioned at any desirable location on the vehicle, V, in any non-symmetric pattern, if desired.
Although the antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b generally correlate to antenna pairs 12, 14, 16, 18, respectively, the antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b do not necessarily operate exclusively within the designated antenna pair (e.g. antenna 12a does not necessarily operate exclusively with antenna 12b). In one embodiment of the invention, the antenna 12a, which is positioned on the exterior of windshield glass 20, may operate in concert with the antenna 14b, which is positioned within the vehicle, V, on the rear windshield glass 22. Another embodiment of the invention may include an antenna system 10 comprising an antenna configuration that includes any one of antennas 12a, 12b, 14a, or 14b positioned within (e.g. one of the antennas from antenna pair 14) or on the exterior (e.g. one of the antennas from antenna pair 12) of one of the glass portions 20, 22 that operates in concert with the antenna 16a positioned on the instrument panel 24 or antenna 16b positioned on the rear package shelf 26 within the vehicle. Another embodiment of the invention may be directed to an antenna system 10 that includes antenna 18a or 18b positioned on an exterior shell of the vehicle, such as an outer glass frame portion 28 or fender 30 with any one of the antennas 12a, 12b, 14a, 14b positioned on the interior or exterior of the glass 20, 22 or antennas 16a, 16b positioned on an instrument panel 24 or package shelf 26. Thus, it is contemplated that the antennas comprising the antenna system 10 may include at least two antennas that are located on any portion of the vehicle, V, such as the glass 20, 22, an instrument panel 24, rear package shelf 26, the exterior shell 28, 30, or any other desirable location such that the antennas are positioned exteriorly on the vehicle, V, or within the vehicle, V.
Once the antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b are positioned, an SDARS-satellite cable and/or an SDARS-terrestrial cable, which is generally shown at 32a for the front, F, of the vehicle, V, and at 32b, for the rear, R, of the vehicle, V, extends toward a receiver 34 from the respective antennas 12a, 14a, 16a, 18a positioned at the front, F, and antennas 12b, 14b, 16b, 18b positioned at the rear, R. As explained above, any desirable number of antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b may be implemented in the vehicle in any desired configuration or pattern; therefore, for illustrative purposes, only one cable 32a is shown extending from the antenna 16a and one cable 32b is shown extending from the antenna 16b. However, it is contemplated that multiple cables 32a, 32b may be spliced or individually extend from multiple antennas positioned at the front, F, or rear, R, of the vehicle, V, for implementations including more than two antennas.
It is preferable to locate the receiver 34 as close to the antenna elements as possible such that losses in the cables 32a, 32b are kept to a minimum. In some implementations, it may not be possible to centrally locate the receiver 34 in the vehicle, V, such that both cables 32a, 32b have the same lengths and thus, the same losses. As illustrated, the receiver 34 is positioned about the rear, R, of the vehicle, V, such that the cable 32a is much longer than the cable 32b (i.e. the cable 32a has greater signal loss than the cable 32b). Essentially, in this embodiment of the invention, an LNA 104 (
The antennas 12a, 12b, 14a, 14b, 16a, 16b, 18a, 18b, which are hereinafter referred to as antennas 12a–18b, may be considered low-profile, multi-band terrestrial/satellite antennas. It is preferable that the antennas 12a–18b include a structure that minimizes the overall height (i.e. include a ‘low-profile’) of the antenna such that the antenna is essentially transparent to vehicle occupants and observers and not very noticeable. It is contemplated that ‘low-profile’ antennas may be defined to include any antenna height less than or equal to 20 mm. Although it is preferable to minimize the height of the antennas 12a–18b, the antenna height may extend past what is considered to be ‘low profile,’ as designated above, such that the antennas 12a–18b are positioned according to the antenna system 10, as explained above with respect to
Four possible embodiments of the multi-band terrestrial/satellite antennas 12a–18b that may be applied in the antenna system 10 are illustrated in
Referring specifically to
Referring now to
It is known that antenna impedance is referenced from the ground; therefore, it is preferable to introduce the ground plane 108 in the design of the antennas 100a–100d to avoid undesirable ripple to obtain a smooth polar response. It is preferable to maintain a minimum ground plane 108 of approximately 100 sq-mm or 100 mm-diameter regardless of antenna position. If the antenna is located on the glass 20, 22, then ground plane 108 may be introduced without any structural alterations to the antenna; however, if the antenna is located on the front or rear dash 24, 26, the ground plane 108 is not effected because a ground plane already exists on the front or rear dash 24, 26. Referring to
Referring now to
Although not illustrated, it is contemplated that any desired antenna may be implemented in the design of the antenna system 10. For example, the antennas 12a–18b may include a patch antenna incorporating a plurality of micro-strips that have a specific impedance when placed on the glass, which is similar to the printed glass antenna illustrated in
As explained above, the antenna system enhances performance of the receiver by using at least a second antenna when a satellite signal is obstructed. Accordingly, there is a higher probability that the second antenna is not being obstructed, and therefore, the receiver would still be able to see the signal. Essentially, signal reception is maintained by switching and/or combining the satellite and terrestrial re-transmitted satellite signals received by the antennas. The switching and/or combining is determined by design-specific criteria used by the receiver, such as bit error rate, carrier to noise, or signal strength, or any other decision-based criteria algorithms. By introducing the second antenna, not only is performance improved, but other packaging, installation, and maintenance issues are overcome as well by locating discrete patch or loop-type antenna inside of, outside of, or about the vehicle. For example, because the antenna may be a low profile antenna, height restrictions on car carriers, truck carriers, or other vehicle carriers should not be an issue. Although discussion of the antenna system has focused on the particular application of a vehicle, V, it should be readily apparent to one skilled in the art, that the antenna system can be just as easily used in an aircraft, boat, train, mobile home, recreational vehicle or truck.
The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.
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