This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-194931 filed on Jul. 4, 2005.
The present invention relates to an on-vehicle film antenna attached to a vehicle windshield.
As a vehicle-mounted antenna, a rod antenna, a film antenna or the like is proposed. A film antenna, which is attached to a vehicle windshield (window), is most often adopted recently, because it is not deformed by impact, does not generate whipping sounds, does not damage outlook. One example of such a film antenna is disclosed in JP 2004-72419A.
An improved film antenna is also proposed in US 2005/0264461 A1. This antenna is a loop type for receiving radio waves of UHF band (470 MHz to 770 MHz) corresponding to digital television broadcasting. It is preferred that this antenna is adapted to be capable of also receiving radio waves of VHF band (90 MHz to 220 MHz) corresponding to digital radio broadcasting in addition to the radio waves of the UHF band.
If a loop antenna is adapted to receive the radio waves of the VHF band, the antenna needs to have an antenna element length, which is about one half of the wavelength of the radio wave of the VHF band. As a result, the loop antenna becomes large in its entire size and hinders visibility through a vehicle windshield. If a loop antenna for receiving radio waves of the UHF band and a loop antenna for receiving radio waves of the VHF band are constructed separately, the two loop antennas must be attached to a vehicle windshield. As a result, assembling work becomes complicated, and adds costs due to necessity of power supply terminals and electric wirings for the two antennas.
The present invention therefore has an object to provide an on-vehicle film antenna, which receives both radio waves in two different frequency bands without hindering visibility through a vehicle windshield.
In one aspect, an on-vehicle film antenna is constructed with a loop antenna and a monopole antenna and attached to a vehicle windshield. The loop antenna has a first element set in length to correspond to a first radio wave of a first frequency band. One end of the first element is connected to a power supply near a border section between a vehicle chassis and the vehicle windshield, and another end of the first element is connected to the vehicle chassis. The monopole antenna has a second element set in length to correspond to a second radio wave of a second frequency band. One end of the second element is connected to the power supply near the border section in common with the one end of the first element, and another end of the second element is disconnected from the vehicle chassis.
In another aspect, an on-vehicle film antenna is constructed with a switchable antenna and attached to a vehicle windshield. The switchable antenna has an element, which is switchably coupled capacitively to the vehicle chassis. One end of the element is connected to a power supply near a border section between a vehicle chassis and the vehicle windshield, and another end of the element is connectable to the vehicle chassis to receive a radio wave of a first frequency band and disconnectable from the vehicle chassis to receive a radio wave of a second frequency band.
In a further aspect, an on-vehicle film antenna is constructed with a switchable antenna and a switch and attached to a vehicle windshield. The switchable antenna has an element, which is switchably connectable to the vehicle chassis. One end of the element is connected to a power supply near a border section between a vehicle chassis and the vehicle windshield, and another end of the element is connectable to the vehicle chassis. The switch is connected between the another end and the vehicle chassis to selectively connect and disconnect the element to and from the vehicle chassis.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:
Referring first to
The loop antenna 2 has an element 8, which is bent to have an acute angle. One end 8a of the element 8 is connected to a power supply 9 near the corner section of the ceiling part 5 and the pillar part 6 and near the boundary with the front windshield 7. The other end 8b of the element 8 is connected to the ceiling part 5 of the vehicle chassis 4, which is a grounding plate. Thus, the element 8 is formed in a triangular loop. The length of the element 8, that is, length between the ends 8a and 8b, is set to about one half of the wavelength of the radio wave of the UHF band (470 MHz to 770 MHz), which is a frequency band of a digital television broadcasting.
The length of the element 8 may be set in consideration of the wavelength reduction ratio, which is about 0.7 to 0.8 times, due to the dielectric constant of a glass of the front windshield 7. The angle of bending of the element 8 is acute so that a capacitive coupling is provided between two straight pieces of the element 8. The angle of grounding of the element 8 relative to the vehicle chassis 4 is also acute so that a capacitive coupling is provided between the element 8 and the vehicle chassis 4. Thus, the radio wave of the UHF band, which can be received, is widened in frequency.
The monopole antenna 3 has an element 10, which is bent to have an acute angle. One end 10a of the element 10 is connected to the power supply 9 near the corner section of the ceiling part 5 and the pillar part 6 and near the boundary with the front windshield 7. The other end 10b of the element 10 is disconnected from the vehicle chassis 4. The length of the element 10, that is, length between the ends 10a and 10b, is set to about one quarter of the wavelength of the radio wave of the VHF band (90 MHz to 220 MHz), which is a frequency band of a digital radio broadcasting.
The length of the element 10 may be set in consideration of the wavelength reduction ratio, which is about 0.7 to 0.8 times, due to the dielectric constant of the glass of the front windshield 7. The angle of bending of the element 10 is acute so that a capacitive coupling is provided between two straight pieces of the element 10. Thus, the radio wave of the VHF band, which can be received, is widened in frequency. Since both the loop antenna 2 and the monopole antenna 3 are connected in common to the power supply 9, the radio wave of the UHF band and the radio wave of the VHF band need be separated by a tuner (not shown).
As understood from
According to the first embodiment, the antenna for receiving the radio wave of the UHF band is constructed by the loop antenna 2 having the element length which is one half of the wavelength of the radio wave of the UHF band, and the antenna for receiving the radio wave of the VHF band is constructed by the monopole antenna 3 having the element length which is one quarter of the radio wave of the VHF band. As a result, the size of the entire antenna can be made small not to hinder the visibility, while ensuring reception of both the radio waves of the UHF band and the VHF band.
Since the loop antenna 2 and the monopole antenna 3 are integrated into a single unit, both antennas can be attached to the front windshield 7 at the same time thus simplifying attachment work. Further, since the loop antenna 2 and the monopole antenna 3 are connected in common to the power supply 9, power supply to the antennas can be attained by only one electric wiring thus reducing cost.
The on-vehicle antenna 1 is provided near the corner section at which the ceiling part 6 and the pillar part 6 join. As a result, radio waves arriving from the vehicle front part can be surely received. Further, even if radio waves arrive from the vehicle rear part, diffracted waves thereof arriving from the vehicle side surface and the ceiling surface of the vehicle chassis 4 can be more efficiently received. That is, the antenna 1 can stably receive the radio waves irrespective of directions in which the vehicle is heading and the radio waves are arriving.
The first embodiment may be modified in various manners.
As a first modification, as shown in
The element 14 is shaped to extend from the corner section between the ceiling part 5 and the pillar part 6 towards the radially inside part of the windshield frame, so that the other end 14b is distanced away from the corner section towards the lateral downward point on the front windshield 7. As a result, the polarized surface is inclined and hence the antenna can have a non-directional characteristic. The monopole antenna 13 is bent towards and closely to the loop antenna 12. Therefore, the antenna 11 can be arranged in a small area.
As a second modification, as shown in
As a third modification, as shown in
As a fourth modification, as shown in
One end 34a of the element 34 is connected to the power supply 9 near the corner section of the ceiling part 5 and the pillar part 6 and near the boundary with the front windshield 7. The other end 34b of the element 34 is connected to the ceiling part 5 of the vehicle chassis 4, which is a grounding plate. The length of the element 34, that is, length between the ends 34a and 34b, is set to about one half of the wavelength of the radio wave of the VHF band. The length of the element 34 may be set in consideration of the wavelength reduction ratio, which is about 0.7 to 0.8 times, due to the dielectric constant of a glass of the front windshield 7. The antenna 32 is also connected to the power supply 9.
According to an arrangement shown in
According to an arrangement shown in
In a second embodiment shown in
One end 54a of an antenna element 54 of the switchable antenna 53 is connected to the power supply 9 in common with the loop antenna 52 at the corner section at which the ceiling part 5 and the pillar part 6 join. However, the other end 54b of the element 54 is switchably arranged, so that the element 54 may be connected or shorted to the vehicle chassis 4 for receiving the radio wave of the UHF band but disconnected from the vehicle chassis 4 for receiving the radio wave of the VHF band. Thus the capacitive coupling of the element 54 to the vehicle chassis 4 is made switchable.
According to the second embodiment, since the antenna 53 is switchable to a loop antenna (the end 54b is grounded to the chassis 4 for receiving the UHF band radio wave) and to a monopole antenna (the end 54b is made open from the chassis 4 for receiving the VHF band radio wave), the on-vehicle antenna 51 can receive both radio waves in the UHF band and the VHF band.
Since the antenna 53 is switchable, it operates as the loop antenna and the monopole antenna, the operation characteristics of which are different. When the antenna 53 is switched to operate as the loop antenna for the UHF band, two loop surfaces are formed jointly with the loop antenna 52 thus increasing an antenna gain based on antenna arrangement effect. Further, non-directional characteristic is furthermore enhanced.
As a modification of the second embodiment, as shown in
In a third embodiment shown in
One end 74a of the element 74 is connected to the power supply 9 in common with the loop antenna 72 at the corner section. The other end 74b of the element 74 is connected to a switch 75, which is connected to the pillar part 6 of the vehicle chassis 6. The element 74 is grounded to the vehicle chassis 4 to operate as the loop antenna for receiving the UHF band wave when the switch 75 is turned on, and made open to the vehicle chassis 4 to operate as the monopole antenna for receiving the VHF band wave when the switch 75 is turned off. Thus, the third embodiment also provides the similar advantages as the second embodiment.
The above embodiments and modifications may be implemented in many other ways. For instance, the loop antenna for receiving the UHF band radio wave may be in any loop shape other than the triangular loop shape. A plurality of antennas, each of which is constructed according to the second and third embodiments shown in
Number | Date | Country | Kind |
---|---|---|---|
2005-194931 | Jul 2005 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
6535170 | Sawamura et al. | Mar 2003 | B2 |
6891515 | Langley et al. | May 2005 | B1 |
7030821 | Mathiae et al. | Apr 2006 | B2 |
20050264461 | Sugimoto et al. | Dec 2005 | A1 |
20070097001 | Sugimoto et al. | May 2007 | A1 |
Number | Date | Country |
---|---|---|
2001-102836 | Apr 2001 | JP |
2002-135025 | May 2002 | JP |
2002-185238 | Jun 2002 | JP |
2004-072419 | Mar 2004 | JP |
2005-167619 | Jun 2005 | JP |
Number | Date | Country | |
---|---|---|---|
20070001915 A1 | Jan 2007 | US |