This application claims priority to European patent application no. EP16382335.4, filed on Jul. 14, 2016, the disclosure of which is incorporated herein by reference in its entirety.
Traditionally, vehicles have been provided with antennas mounted in different locations of the vehicle. Usually, these antennas were broadband monopoles located at the rear window and/or on the roof.
Over the years, the number of radio-communication services has increased and, in consequence, the number of antennas required for providing these services.
Also, aesthetic and aerodynamic trends have changed and, over the years, satisfying customer tastes has become essential in the automotive industry. Lately, customer tastes generally lead to vehicles having a streamlined and smooth appearance, which interfere with providing the vehicle with multiple and dispersed antennas.
Thus, both for meeting customer tastes and providing all the radio-communication services possibly demanded by the driver, the automotive industry is tending to integrate in a single module all the communication modules specifically designed for providing one communication service, such as telephony, AM/FM radio, satellite digital audio radio services (SDARS), global navigation satellite system (GNSS), or digital audio broadcasting (DAB).
The integration of multiple antenna units in a single global antenna module leads to achieve great advantages in costs, quality and engineering development time.
This global antenna module is subject to meet current customer tastes. For that, it would be desirable to reduce the size of traditional antenna systems in order to be able to integrate them in a module that can maintain the streamlined appearance of the vehicle. However, reducing the size of an antenna system affects its performance.
Further, the automotive industry has to meet customer demands on communication, being thus obliged to provide robust communications in all services available for the driver. For that, it would be desirable to provide an antenna system able to operate in a broad bandwidth with high efficiency.
Then, it would be desirable to develop an improved antenna system for a vehicle that having a reduced size, offers a high efficiency and a broadband behavior. It would be also desirable that the improved antenna system operates on all LTE frequency bands without losing its broadband and high efficient characteristics in any band.
The present invention overcomes the above mentioned drawbacks by providing a new design of a broadband antenna system for a vehicle, which having a reduced size is capable of providing a high bandwidth and a high efficiency, also at all LTE frequency bands.
In one aspect of the invention, the broadband antenna system for a vehicle comprises a radiating element for operating at at least one frequency band of operation and disposed on at least a first portion area of a dielectric material, a substrate, a conductive element disposed on that first portion area, a grounding point, a feeding element, and a ground plane circumscribed by a rectangle having said circumscribed rectangle minor and major sides.
The ground plane could be disposed in the same substrate with the radiating element, disposed on a second portion area of the substrate, or disposed perpendicular to the radiating element, outside the substrate.
The radiating element has at least three angles and at least three sides, a first side being substantially aligned with one side of the circumscribed rectangle and a first angle having an apex, said apex being the closest point of the radiating element to the ground plane.
The conductive element has at least a first portion extending between one of the sides of the first portion area of the substrate and the radiating element. The conductive element is electrically isolated from the radiating element, having no electric connection therebetween. Further, the conductive element is coupled to ground plane through the grounding point.
The grounding point is disposed at one extreme of the first portion area of the substrate. The feeding element is electromagnetically coupled with the radiating element through the apex of the first angle.
Additionally, each major side of the ground plane has an electric length (Lgp) of at least 0.13λ, being λ the lowest frequency of the antenna's band operation, and the first angle of the radiating element having an aperture lower than 156°, said aperture preferably ranging from 80° to 156°, having an optimum range from 120° to 156° and with a optimum aperture value of 150°.
Preferably, the conductive element has an electric length, and the sum of the electric length of the major side of the ground plane and the electric length of the conductive element ranges from 0.18λ to 0.22λ, being λ the lowest frequency of the antenna's band operation.
According to a preferred embodiment, the radiating element has a length measured from the first side to the first angle lower than 1/10λ, and a width measured as the length of the first side of the radiating element lower than ⅛λ, being λ the lowest frequency of the antenna's band operation.
Also, according to a preferred embodiment, the first portion of the conductive element is bigger than ⅛λ, being λ the lowest frequency of the antenna's band operation.
Providing the radiating element and the conductive element as described, the antenna system modifies the electric length of the ground plane, modifying its frequency behaviour. This modified frequency behaviour brings the resonance of the ground plane to lower frequencies, surging a new resonant frequency, which in case of the radiating element operates at the LTE frequency band of operation, a new resonant frequency surges at the LTE 700 band.
For instance, for the LTE frequency band of operation, the invention provides an antenna system capable of covering the lowest frequencies of LTE on a ground plane of reduced dimensions, in particular, on a ground plane of at least 0.13λ, being λ the lowest frequency of the antenna's band operation, i.e. λ=700 MHz (ground plane: 55.9 mm).
Thus, in the LTE case, the invention provides a broadband antenna system having high efficient characteristics, such as:
In another aspect of the invention, a shark fin antenna comprises the broadband antenna system of the invention and a cover for enclosing said antenna system.
The invention can provide a new design of an antenna system, specifically designed for being installed on a vehicle, and preferably, for operating on the LTE network. This new antenna is also designed for being capable of integrating different antennas to provide additional communication services.
In some embodiments, the invention can provide an antenna system having a broad bandwidth behavior, which is capable of offering a high efficiency, and which is capable of reducing the size of existing antenna systems for vehicles.
In some embodiments, the invention can provide an antenna system capable of covering all the 4G frequency bands, ensuring that the antenna maintains the desired behavior at the whole band of operation, and in particular, at the lower LTE frequency range 700-800 MHz.
In some embodiments, the invention can provide an antenna system capable of being integrated with other vehicle radio-communication services in a single compact shark fin antenna module.
For a better comprehension of the invention, the following drawings are provided for illustrative and non-limiting purposes, wherein:
The ground plane 2 has a rectangular configuration, having major 2a and minor 2b sides. The ground plane 2 is disposed on the second portion area 3b of the substrate 3, while the radiating element 4 is disposed on the first portion area 3a of the substrate 3.
In this first embodiment, the ground plane 2 and the radiating element 4 are on the same substrate 3 and can be formed into a single body, where the second portion area 3b of the substrate 3 allocates the ground plane 2, and the first portion area 3a of the substrate 3 allocates the radiating element 4. Further, the first portion area 3a of the substrate 3 allocates the conductive element 5, the grounding point 9, and the feeding element 8.
The first portion area 3a is disposed on a corner of the substrate 3 and the second portion area 3b is disposed on the rest of the substrate 3.
The grounding point 9 is disposed at the upper extreme of the first portion area 3a of the substrate 3, and preferably at the interface between the first 3a and the second portion area 3b of the substrate 3. The grounding point 9 is coupled to the ground plane 2. The feeding element 8 is adapted to feed the radiating element 4, and is electromagnetically coupled with said radiating element 4.
The radiating element 4 has at least three angles and three sides, a first side 7 is aligned with the upper minor side 2b of the ground plane 2, and a first angle 6 whose vertex is the closest point to the ground plane 2. Further, the first angle 6 is opposite to the midpoint of the first side 7, wherein the first side 7 is the longer side of the radiating element 4. The first angle 6 has an aperture lower than 156°, 150° in the embodiment. In
As shown in the detailed view of
Preferably, the first portion 5′ of the conductive element 5 is bigger than ⅛λ, being λ the lowest frequency of the at least one LTE frequency band of operation of the broadband antenna system 1.
Also, the first portion 5′ of the conductive element 5 is preferably spaced 50 μm from the radiating element 4.
Preferably, as shown in
For purposes of describing this invention, space-filling curve should be understood as defined in U.S. Pat. No. 7,868,834B2, in particular, in paragraphs [0061]-[0063], and
One extreme of the conductive element 5 of the broadband antenna system described herein may be shaped as a space-filling curve.
A space-filling curve is a non-periodic curve including a number of connected straight segments smaller than a fraction of the operating free-space wave length, where the segments are arranged in such a way that no adjacent and connected segments form another longer straight segment and wherein none of said segments intersect each other.
In one example, an antenna geometry forming a space-filling curve may include at least five segments, each of the at least five segments forming an angle with each adjacent segment in the curve, at least three of the segments being shorter than one-tenth of the longest free-space operating wavelength of the antenna. Each angle between adjacent segments is less than 180° and at least two of the angles between adjacent sections are less than 115°, and at least two of the angles are not equal. The example curve fits inside a rectangular area, the longest side of the rectangular area being shorter than one-fifth of the longest free-space operating wavelength of the antenna. Some space-filling curves might approach a self-similar or self-affine curve, while some others would rather become dissimilar, that is, not displaying self-similarity or self-affinity at all (see for instance 1510, 1511, 1512).
The major side 2a of the ground plane 2 has an electric length (Lgp) of at least 0.13λ, being λ the lowest frequency of the at least one LTE frequency band of operation of the antenna system 1, i.e. 700 MHz (λ=43 cm).
The electric length of the ground plane (Lgp) is modified by the electric length (Lce) of the conductive element 5, which acts as an extensor of the ground plane. The electric length (Lce) of the conductive element 5 is the sum of the electric length of the first (Lce′) and second portion (Lce″) of the conductive element 5, that is, Lce=Lce′+Lce″.
Preferably, the sum of the electric length (Lgp) of a major side (2a) of the ground plane 2 and the electric length (Lce) of the conductive element 5 ranges from 0.18λ, to 0.22λ, being λ the lowest frequency of the at least one LTE frequency band of operation of the antenna system.
As shown, the antenna system covers LTE frequency bands ranging from 700 MHz to 960 MHz with an efficiency greater than −2 dB, an average gain greater than −1.5 dBi and maximum gain greater than 1 dBi. Thus, the broadband antenna system satisfies customer requirements covering the lower 4G frequency bands (LTE 700/LTE 800) with good directivity and minor power losses (high efficiency) with better frequency response than current mobile phone antennas, which have 6 dB of losses.
Also, as shown in
Also, the antenna system provides at the LTE frequency band ranging from 2500 to 2700 an efficiency greater than −2.5 dB, an average gain greater than −2 dBi, and maximum gain greater than 3 dB. Thus, the broadband antenna system provides very high directive and efficiency features at this range.
According to a second embodiment, the broadband antenna system 1 further comprises a matching network coupling the radiating element 4 with the feeding element 8. The matching network may consist on a transmission line or a multiple section of transmission lines.
According to this second embodiment,
Also, according to a preferred embodiment, the radiating element 4 has a length (Lre) measured from the first side 7 to the first angle 6 greater than 1/10λ, and a width (Wre) measured as the length of the first side 7 of the radiating element 4 greater than ⅛λ, being λ the lowest frequency of the at least one LTE frequency band of operation of the antenna system 1.
For that, the major sides 2a of the ground plane 2 have to be greater than 0.13λ, being λ the lowest frequency of operation of the antenna system, since, this way, at the lowest frequency band, i.e. 700 MHz (λ=430 mm), the major sides 2a of the ground plane 2 would be around 55 mm.
As shown in
According to the preferred embodiment, the radiating element 4 has at least three angles and three sides, wherein a first side 7 is aligned with the minor side 2b of the ground plane 2, and a first angle 6 is the angle whose apex is the closest point of the radiating element 4 to the ground plane 2. In the figure, the first side 7 is the longer side of the radiating element 4, and the first angle 6 is lower than 156°.
The first angle of the radiating element has a direct effect on the real part of the impedance of the antenna system. For that,
As shown, the first angle 6 has to be lower than 156° so as to the real part of the impedance of the antenna system is suitable for offering the mentioned antenna performance.
Preferably, the sum of the electric length (Lgp) of a major side 2a of the ground plane 2 and the electric length (Lce) of the conductive element 5 ranges from 0.18×, to 0.22λ, being λ the lowest frequency of the at least one LTE frequency band of operation of the antenna system 1.
According to a third embodiment, the broadband antenna system 1 further comprises at least one additional antenna selected from the group of: a satellite digital audio radio services (SDARS) antenna, a global navigation satellite system (GNSS) antenna, a digital audio broadcasting (DAB) antenna, and an AM/FM antenna.
In this third embodiment, the ground plane of the antenna system is an integral part of a vehicle, such as a roof, thus having larger dimensions than the previous embodiments.
As shown in
The upper antenna module 29 preferably comprises the first portion area 3a of the substrate 3, and first and second additional substrates 17′, 17″ for allocating the radiating element 4, the conductive element 5, a satellite digital audio radio services (SDARS) 18, a Global navigation satellite system (GNSS) antenna 19, a first 25 and a second 26 DSRC V2X (Dedicated Short-Range Communications Vehicle-to-infrastructure) antennas, and a RKE (Remote Keyless Entry) antenna 27. As shown, the radiating element 4, the conductive element 5, the first DSRC V2X antenna 25, and the RKE antenna 27 are preferably allocated in the first portion area 3a of the substrate 3; the second DSRC V2X antenna 26 is preferably allocated in the first additional substrate 17′; and the SDARS 18, and the GNSS antenna 19 is preferably allocated in the second additional substrate 17″.
The lower antenna module 30 preferably comprises a third additional substrate 17′″ for allocating a WiFi/Bluetooth antenna 23, a digital audio broadcasting (DAB) antenna connection 20, AM/FM antenna connections 21, and TV connections 28. The third additional substrate 17′″ serves as portable support for holding the upper 29 and lower antenna module 30. Further, the third additional substrate 17′″ is supported by a base 22, which can be adapted to be fixed to a roof of a vehicle.
This way, the shark fin antenna 15 integrates all these radio-communication services in a single and compact device.
Finally, according to a fourth embodiment, the invention contemplates a vehicle having a roof and a broadband antenna system 1 as described, wherein the substrate 3 of said antenna system 1 is disposed substantially orthogonal to the ground. Preferably, the substrate 3 is enclosed by a cover 16 to form a shark fin antenna 15 for the vehicle.
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Entry |
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European Search Report from the European Patent Office for EP Application No. 16382335.4, dated Jan. 23, 2017, 8 pages. |
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