Dual band PCB antenna for vehicle

A printed circuit board (PCB) is disposed to stand vertically on a main board and having a first surface and a second surface opposite to the first surface. A main antenna pattern is formed on the first surface of the PCB to operate in dual band including a low frequency band and a high frequency band. A bandwidth extension pattern is formed on the second surface of the PCB and formed to operate in the high frequency band, the bandwidth extension pattern having a coupling stub which forms an overlapping portion with a portion of the main antenna pattern, with the PCB interposed therebetween, to implement an antenna having an extended bandwidth, which operates together with the portion of the main antenna pattern in the high frequency band.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2014-0019476 filed on Feb. 20, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND

(a) Technical Field

The present disclosure relates to an antenna for a vehicle. More particularly, the present disclosure relates to a dual band printed circuit board (PCB) antenna having an extended bandwidth for a vehicle, which is disposed on a main board having a feed circuit thereon and can stably operate in both low and high frequency bands.

(b) Background Art

An antenna for a vehicle performs a function of transmitting/receiving radio signals so that a transceiver for broadcast/communication, mounted inside the vehicle, can communicate with an external device. An antenna of the related art for a vehicle is typically mounted only for the purpose of receiving AM/FM radio signals. A passive antenna of a monopole type, which does not include an amplifying circuit therein, has been widely used as such an antenna. However, the antenna of the related art requires a physical length of about 70 cm and hence becomes a factor that deteriorates the appearance and the driving performance of the vehicle.

Accordingly, an active antenna including an internal amplifying circuit has been developed in order to reduce the physical length of the antenna and to overcome the deterioration of reception signals. The active antenna mainly has the form of a poly-type helical antenna, which is an antenna having a structure of a spiral coil shape so that resonance can be generated with a length shorter than the basic resonance length. The helical antenna can receive broadcast signals by generating resonance at a specific frequency through adjustment of its length, pitch, etc.

Meanwhile, as services including mobile communications and the like are commercialized, various equipment and new electronic products, to which information/communication technologies are applied, have been continuously developed. In addition, electronic products for performing functions related to Internet, TV, GPS, satellite radio, DMB, telematics and the like have been developed and mounted in vehicles in order to satisfy various customers' requirements. As the variety of radio services in a vehicle, including Internet, TV, GPS, satellite radio, DMB, telematics and the like, increase as described above, the need for an antenna capable of operating in various frequency bands, and particularly an integrated antenna for supporting radio communication services in several bands, also increases.

Hereinafter, an integrated antenna for a vehicle according to the related art will be described with reference to the accompanying drawing.

FIG. 1is a perspective view showing an example of an integrated antenna for a vehicle, which is implemented with a shark-fin antenna, in which its case is indicated with a dotted line.

As shown in this figure, the shark-fin antenna includes a pad1, a frame2, a case3, a main board4and the like, and may be provided with a patch antenna5, a helical antenna6, a PCB antenna7and the like, which are built-in antennas connected to the main board4. Here, the patch antenna5may be a satellite radio antenna that operates in a satellite radio frequency band, and the helical antenna6may be an antenna for receiving broadcast signals, e.g., a DMB receiving antenna that operates in a DMB frequency band. The PCB antenna7is an antenna implemented by forming an antenna pattern designed to operate in a predetermined frequency band on a surface of a PCB and then connecting the antenna pattern to a circuit of the main board4. In addition, the PCB antenna7may be an antenna that operates in a mobile communication frequency band.

A telematics unit (TMU) has integrated antennas built therein to communicate with external devices, thereby having a function of transmitting/receiving radio signals for the TMU. Recently, integrated antennas have evolved into specifications of long term evolution (LTE) from specifications of the existing TMU. The LTE has a broad frequency bandwidth while having a multi-band, and thus, it is necessary to develop an LTE antenna for extending the bandwidth of operating frequencies. More specifically, the use frequency of the LTE is changed for each communication provider. For example, the use frequency of the LTE has a multi band such as 824 MHz to 894 MHz, 1710 MHz to 1870 MHz and 1920 MHz to 2170 MHz.

Accordingly, in order to implement an antenna satisfying operating characteristics of the multi band, it is required to develop a dual band antenna, particularly an antenna having a broad bandwidth in the high frequency band, that operates, for example, in a low frequency band of 824 MHz to 894 MHz and a high frequency band of 1710 MHz to 2170 MHz.

However, in order to implement the LTE antenna with the multi-band operating characteristics, bandwidth should be extended so that the LTE antenna can operate in a broader frequency band, including the existing mobile communication frequency bands. However, it can be difficult to apply a general bandwidth extension method to the dual band antenna. For example, when a method for extending a bandwidth in a high frequency band is applied in order to implement a dual band antenna that operates in both the low frequency band of 824 MHz to 894 MHz and the high frequency band of 1710 MHz to 2170 MHz, the low frequency band can be negatively affected, making it is difficult to use the dual band antenna.

SUMMARY OF THE DISCLOSURE

The present disclosure provides an antenna for a vehicle, which can stably operate in a dual band. The present disclosure also provides a dual band PCB antenna having an extended bandwidth for a vehicle, which is disposed on a main board having a feed circuit thereon. The dual band PCB antenna can be disposed in a shark-fin antenna, can stably operate in both low and high frequency bands without negatively affecting the low frequency band, and can relatively extend the bandwidth of the high frequency band.

In an embodiment, the present disclosure provides a dual band PCB antenna having an extended bandwidth for a vehicle, which is disposed on a main board having a feed circuit formed thereon, the dual band PCB antenna including: a PCB disposed to stand vertically on the main board and having a first surface and a second surface opposite to the first surface; a main antenna pattern formed on the first surface of the PCB to operate in dual band including a low frequency band and a high frequency band; and a bandwidth extension pattern formed on the second surface of the PCB and formed to operate in the high frequency band, the bandwidth extension pattern having a coupling stub which forms an overlapping portion with a portion of the main antenna pattern, with the PCB interposed therebetween, to implement an antenna having an extended bandwidth, which operates together with the portion of the main antenna pattern in the high frequency band.

In an embodiment, the bandwidth extension pattern may be connected to a ground through the main board. The bandwidth extension pattern may be vertically formed on the second surface of the PCB. The coupling stub extends so as to protrude sideward from one side of the bandwidth extension pattern. A ground connection terminal that is a lower end portion of the bandwidth extension pattern may be connected to the ground through the main board. The main antenna pattern may include a lower first pattern portion and an upper second pattern portion formed on the first surface of the PCB; a low frequency band pass filter portion formed between the first and second pattern portions to reject signals of the high frequency band in the low and high frequency bands; and a feed portion formed at the first pattern portion that is electrically connected to the feed circuit of the main board. The low frequency band pass filter portion may be configured to include first and second inductor patterns respectively formed on the first and second surfaces of the PCB to have inductor elements, and a capacitor pattern formed on the second surface of the PCB to have a capacitor element. The capacitor pattern may be integrally connected to the first pattern portion, the first inductor pattern may be integrally connected to the capacitor pattern, and the second inductor pattern may be electrically connected to the first inductor pattern and the second pattern portion. The second inductor pattern may be electrically connected to the first inductor pattern and the first pattern portion through a via hole formed in the PCB. The first and second inductor patterns may be formed as loop-shaped patterns of which both ends are opened on the first and second surfaces of the PCB. The opening directions of both ends of the first and second inductor patterns may be different from each other. The first and second inductor patterns may be electrically connected to each other through the via hole, thereby entirely having a spiral pattern shape.

Accordingly, the PCB antenna of the present disclosure is provided with a main antenna pattern operating in the dual band including a low frequency band and a high frequency band and a separate bandwidth extension pattern coupled to a first pattern portion operating in the high frequency band in the main antenna pattern, so that the bandwidth of the high frequency band is extended without negatively affecting the operating performance of the low frequency band, thereby stably operating in the dual band.

The above and other features of the disclosure are discussed infra.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the disclosure. The specific design features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. In the figures, reference numbers refer to the same or equivalent parts of the present disclosure throughout the several figures of the drawing.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings and described below. While the disclosure will be described in conjunction with embodiments, it will be understood that present description is not intended to limit the disclosure to those embodiments. On the contrary, the disclosure is intended to cover not only the embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the disclosure as defined by the appended claims.

The present disclosure provides a dual band PCB antenna having an extended bandwidth for a vehicle, which is disposed on a main board having a feed circuit thereon in a shark-fin antenna and can stably operate in both low and high frequency bands. Particularly, the present disclosure provides a PCB antenna which stably operates in a dual band without negatively influencing a low frequency band and relatively extends the bandwidth of a high frequency band in the dual band. The PCB antenna according to the disclosed embodiments can operate in a double band of long term evolution (LTE) through a method of dividing a multi-band frequency range of the LTE into the double band, e.g., a low frequency band of 824 MHz to 894 MHz, for example, and a high frequency band of 1710 MHz to 2170 MHz, for example, and extending the bandwidth of the high frequency band. To this end, the PCB antenna can include an additional monopole antenna pattern, i.e., a separate bandwidth extension pattern formed on a surface of a PCB mounted on a main board.

This will be described in detail with reference to the accompanying drawings.FIG. 2is a front view of a PCB antenna according to an embodiment of the present disclosure.FIG. 3is a rear view of the PCB antenna according to the embodiment of the present disclosure.

FIGS. 4 and 5are respectively front and rear perspective views of the PCB antenna according to the embodiment of the present disclosure. In the front perspective view ofFIG. 4, a second inductor pattern15and a bandwidth extension pattern20, formed on a rear surface of a PCB11, are indicated with solid lines. In the rear perspective view ofFIG. 5, a first pattern portion12a, a capacitor pattern13, a first inductor pattern14and a second pattern portion12c, formed on a front surface of the PCB11, are indicated with solid lines.

The dual band PCB antenna7of the embodiment shown inFIGS. 2 to 5may be disposed to stand vertically on a main board (reference numeral4ofFIG. 1) having a feed circuit thereon in a shark-fin antenna as illustrated inFIG. 1. The dual band PCB antenna7of the embodiment includes the PCB11, a main antenna pattern12and the bandwidth extension pattern20. The main antenna pattern12is formed of a conductor on a surface of the PCB11, and has a feed portion12dand a low frequency band pass filter portion12b. The bandwidth extension pattern20formed of a conductor on a surface of the PCB11, and has a coupling stub21that is a pattern portion coupled to the main antenna pattern12.

More specifically, the main antenna pattern12operating in the dual band of the LTE is formed on the surface of the PCB11. The main antenna pattern12is electrically connected to the feed circuit on the main board (reference numeral4ofFIG. 1) through the feed portion12d.

In the main antenna pattern12, the entire configuration is used in the low frequency band, and the second pattern portion12cdescribed later is used as a dual band monopole antenna that operates in the high frequency band.

The main antenna pattern12, as shown inFIGS. 2 to 5, includes the lower first pattern portion12aand the upper second pattern portion12c, formed on one surface (front surface) of the PCB11, the low frequency band pass filter portion12bhaving strip lines respectively formed on both the surfaces (front and rear surfaces) of PCB11to be combined with each other, and the feed portion12dformed at a lower end of the first pattern portion12a.

Here, the first pattern portion12ais a portion that is formed of a conductor pattern with a predetermined length (predetermined height) vertically formed long at a lower side of the PCB11, and the second pattern portion12cis a portion that is formed of a conductor pattern with a predetermined length at an upper side of the PCB11.

The feed portion12dis a portion that electrically connects the main antenna pattern12to the feed circuit of the main board. The feed portion12dis also formed of a conductor on the one surface of the PCB11.

The low frequency band pass filter portion12bis provided between the first and second pattern portions12aand12c. The lower frequency band pass filter portion12bis configured to include two conductor patterns respectively formed on the front and rear surfaces of the PCB11, i.e., two strip lines formed to have a relatively thin width.

More specifically, the low frequency band pass filter portion12bis configured with the first and second inductor patterns14and15respectively formed on both the surfaces (front and rear surfaces) of the PCB11to have inductor elements, and the capacitor pattern13formed on the one surface (front surface) of the PCB11to have a capacitor element.

Here, the capacitor pattern13is a pattern portion formed to be integrally connected to an upper end portion of the first pattern portion12a, and the first inductor pattern14is a pattern portion formed to be integrally connected to the capacitor pattern13. The second inductor pattern15electrically connects between the first inductor pattern14and the second pattern portion12c.

To this end, a via hole16is formed in the PCB11, and the first and second inductor patterns14and15respectively formed on both the surfaces of the PCB11in the low frequency band pass filter portion12bare electrically connected to each other through the via hole16.

In addition, the second inductor pattern15is electrically connected to one end portion of the second pattern portion12cthrough another via hole17of the PCB11.

In this state, the first and second inductor patterns14and15are formed as loop-shaped patterns of which both ends are opened on both the surfaces of the PCB11. Here, the opening directions of both the ends are different from each other. The first and second inductor patterns14and15are electrically connected to each other through the via hole16, thereby entirely having a spiral pattern shape.

In the configuration described above, the first inductor pattern14is formed to be integrally connected to the capacitor pattern13, and therefore, the first and second inductor patterns14and15have a structure connected in series to the capacitor pattern13.

The low frequency band pass filter portion12bhaving the first and second inductor patterns14and15combined with each other as described above performs a function of passing only frequency signals in the low frequency band and rejecting frequency signals in the high frequency band.

Accordingly, the entire main antenna pattern12configured to include the first pattern portion12a, the second pattern portion12c, the low frequency band pass filter portion12band the feed portion12dbecomes a monopole antenna that operates in the low frequency band (e.g., 824 MHz to 894 MHz). In addition, the second pattern portion12cand the bandwidth extension pattern20described later become another monopole antenna that operates in the high frequency band (e.g., 1710 MHz to 2170 MHz).

Thus, the PCB antenna7of the embodiment becomes an antenna that can operate in the dual band including the high frequency band and the low frequency band. Particularly, the separate bandwidth extension pattern20is additionally provided, so that the bandwidth of the high frequency band can be extended much broader without having influence on operating characteristics of the low frequency band.

The bandwidth extension pattern20is formed on the opposite surface to the second pattern portion12cin the PCB11. If the second pattern portion12cis formed on the front surface of the PCB11, the bandwidth extension pattern20is formed on the rear surface that is the opposite surface to the front surface.

The bandwidth extension pattern20is formed at a predetermined distance from the second pattern portion12con the opposite surface of the PCB11. As illustrated in these figures, the bandwidth extension pattern20may be vertically formed long on the surface of the PCB11.

In this state, the bandwidth extension pattern20may be vertically formed long in parallel to the second pattern portion12cto be spaced apart from the second pattern portion12cat a predetermined distance in the PCB11. A lower end portion of the bandwidth extension pattern20is used as a ground connection terminal22.

That is, the lower end portion of the bandwidth extension pattern20is not connected to the feed circuit of the main board but connected to a ground through the main board.

The bandwidth extension pattern20has the coupling stub21for coupling to the main antenna pattern at one side thereof, more specifically, for coupling to the second pattern portion12c. In this case, the coupling stub21is a pattern portion extended to protrude sideward from one side of the bandwidth extension pattern20. Particularly, the coupling stub21is formed so that portions of the coupling stub21can be overlapped with the second pattern portion12con the respective front and rear surfaces of the PCB11.

InFIGS. 4 and 5, hatching portions indicated by ‘A’ represent overlapping portions of the coupling stub21, which are overlapped with the second pattern portion12con the respective front and rear surfaces of the PCB11.

As a result, the additional bandwidth extension pattern20described above is configured with a ground antenna connected to the ground and a monopole antenna operating together with the second pattern portion12cof the main antenna pattern12in the high frequency band. Accordingly, the bandwidth of the high frequency band can be extended broad by the bandwidth extension pattern20.

If only the second pattern portion12cis used as the monopole antenna operating in the high frequency band without the bandwidth extension pattern20, the entire main antenna pattern12acts as an antenna operating in the low frequency band, and the second pattern portion12cacts as an antenna operating in the high frequency band, thereby obtaining a dual band antenna. However, in the configuration described above, it is difficult to guarantee stable operating performance due to influence on operating performance in the low frequency band. In addition, it is difficult to perform tuning for broadly extending the bandwidth of the high frequency band.

However, in the present disclosure, when the bandwidth extension pattern20is additionally provided, it is possible to implement a stable dual band antenna without having great influence on the performance of the low frequency band. Further, it is possible to adjust the length of the bandwidth extension pattern20, the position or size (area overlapped with the second pattern portion) of the coupling stub21, or the like, thereby performing tuning suitable for operating characteristics.

FIGS. 6 and 7show impedance of the monopole antenna (main antenna pattern) in the high frequency band and impedance of the additional monopole antenna (extension pattern) connected to the ground.

As shown inFIG. 6, impedance characteristics of the monopole antenna in the high frequency band are similar to those of an open type serial resonator.

The impedance at a resonant frequency is near 50Ω, and serial capacitance is added to the impedance at a frequency lower than the resonant frequency. In addition, serial inductance is added to the impedance at a frequency higher than the resonant frequency.

On the other hand, as shown inFIG. 7, impedance characteristics of the additional monopole antenna are opposite to those of the monopole antenna (main antenna pattern) in the high frequency band. The impedance at the resonant frequency is near 50Ω, and an inductance element is added at a frequency lower than the resonant frequency. In addition, a capacitance element is added at a frequency higher than the resonant frequency.

The impedance of the additional monopole antenna is added to that of the existing dual band antenna (main antenna pattern), thereby extending the bandwidth in the high frequency band. In order to extending the bandwidth through the impedance coupling of the two antennas, the impedance variation (impedance variation with respect to a change in frequency) of the high frequency band of the existing dual band antenna is necessarily similar to the impedance variation (impedance variation with respect to a change in frequency) of the additional monopole antenna. Then, the bandwidth of the high frequency band can be extended through the impedance coupling of the two antennas.

In addition, the impedance coupling position, amount and method of the two antennas are important, and a PCB type capacitor is applied in the present disclosure.

That is, the dual band monopole antenna (main antenna pattern, particularly the second pattern portion) is formed on the front surface of the PCB11, and the coupling stub21is positioned on the rear surface of the PCB11, so that the impedance coupling is made by a capacitance value formed between the two patterns.

Such a method has less influence on the low frequency band of the main antenna pattern12. Thus, the method is a method suitable for being applied to the dual band PCB antenna of the present disclosure.

In addition, the impedance coupling amount can be adjusted using the size (overlapped area) of the coupling stub21, and the impedance coupling position can be tuned by adjusting the position of the coupling stub21.

The position and size of the coupling stub21can be determined using an EM simulation tool (e.g., EM-Pro), in consideration of required antenna operating characteristics.

FIG. 8shows voltage standing wave ratio (VSWR) measurement results of the existing dual band monopole antenna having no bandwidth extension pattern (the dual band antenna implemented by forming only the main antenna pattern).FIG. 9is a view showing VSWR measurement results of the antenna having a bandwidth extension pattern according to the embodiment of the present disclosure.

In the existing dual band monopole antenna, the bandwidth of the high frequency band was 16.4%, based on a VSWR of 2.5. On the other hand, in the antenna having the bandwidth extension pattern20, the bandwidth of the high frequency band was 28%, which increased.