WO2022058028A1

WO2022058028A1 - Microstrip antenna with impedance matching bandpass filter

Info

Publication number: WO2022058028A1
Application number: PCT/EP2020/076231
Authority: WO
Inventors: Dmitrij SEMILOVSKY; Johannes Kammerer
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-09-21
Filing date: 2020-09-21
Publication date: 2022-03-24
Also published as: CN116325359A; EP4205232A1

Abstract

A microstrip antenna for operating in an operational frequency range. The microstrip antenna includes an antenna structure printed within a compact area on a substrate. The microstrip antenna further includes a feedback structure printed within the compact area on the substrate, wherein the feedback structure is configured to operate as an impedance matching bandpass filter with a passband defining the operational frequency range. The microstrip antenna provides a high efficiency, low losses and a compact size because of the integrated bandpass filter and suitable for use in an ultra broadband wireless network.

Description

MICROSTRIP ANTENNA WITH IMPEDANCE MATCHING BANDPASS FILTER

TECHNICAL FIELD

The present disclosure relates generally to the field of antenna systems and wireless communication technologies; and more specifically, to a microstrip antenna with an impedance matching bandpass filter for use in an ultra broadband wireless network.

BACKGROUND

With the development of connected vehicles, such as autonomous vehicles (e.g. self driving cars) or semi-autonomous vehicles, a requirement for complex interconnectivity and a machine-to- machine network is rising steadily. Additionally, there is a trend of integrating user devices (e.g. smartphones) with entertainment and security systems of a customers’ car. Therefore, there is an increasing demand of higher data transmission via wireless networks which in turn requires spatial dense integration of antennas in vehicles (e.g. in autonomous as well as in customers’ vehicles). However, the limitation of an available space and rising number of the antennas (e.g. integrated antennas) and also, an electromagnetic coupling between the antennas, create a challenge for efficiently using the available space. For example, an antenna operating in a frequency band creates an interference to a neighourbing antenna operating in an adjacent frequency band by absorbing the frequencies from the adjacent frequency band (because of the limited space and the electromagnetic coupling) and hence, results into a reduced efficiency of the neighbouring antenna.

Currently, certain attempts have been made for decoupling of the antennas (i.e. integrated antennas), for example, by use of conventional distributed filters or conventional lumped filters between the antennas. Each of the conventional distributed filters and the lumped filters have their own features and limitations. The conventional distributed filters use electromagnetic properties of a wave (e.g. an operating wave) in order to create inductive or capacitive effects within a certain bandwidth. This is the reason that the conventional distributed filters are comparable in size with the operating wave (or wavelength). The conventional distributed filters manifest somewhat low losses (or low loss characteristic) but require a relatively large area to be employed. The conventional distributed filters, for example, a conventional distributed bandpass filter may have a center frequency of 5 gigahertz (GHz) and a size of approximatley 14mmx14mm. Therefore, a wireless network including the conventional distributed filters, termed as a distributed band pass matching network, manifests somewhat low losses (e.g. insertion loss and return loss) but has a limited bandwidth and a large size to be employed. Therefore, the advantage of low losses of the conventional distributed filters comes at a price of the large size. Another approach for decoupling of the antennas (i.e. integrated antennas) is use of the conventional lumped filters. The conventional lumped filters use inductive or capacitive components where dimensions of each component is much smaller than the operating wavelength. Generally, the conventional lumped filters are employed in a compact form by use of typical surface mount device (SMD) filters. The surface mount devices (SMDs) also referred as integrated passive devices (IPDs), or integrated passive components (I PCs) or embedded passive components (EPCs) are electronic components where resistors (R), capacitors (C), inductors (L) or coils or chokes, microstriplines, impedance matching elements, baluns (i.e. balanced-unbalanced) or any combinations of said components are integrated either on a same package or on a same substrate. Therefore, the conventional lumped surface mount device (SMD) filters can be realized on relatively small structures hence, can be very compact. However, the conventional lumped SMD filters are expensive (approximately 20cent-30cent) in comparison to the conventional distributed filters for mass production and manifest significant losses (e.g. 1dB-2dB), when in operation. The conventional lumped SMD filters have a fixed frequency range and are less reliable because of aging of SMD elements. Moreover, if the conventional lumped SMD filters are employed as integrated passive devices (IPDs) filters which have a limitation of inflexibility in the filter design. Because in case of the conventional IPDs filters, every component such as an inductor (L), a capacitor (C), a resistor (R), etc. is integrated in one package and therefore, the characteristics of the conventional IPDs filters are defined prior to production and thereafter, no change is possible in the filter design. Therefore, in applications, where low loss and high efficiency is required, the conventional lumped SMD filters are less preferred. In other words, lumped matching networks comprising the conventional lumped SMD filters are compact but introduce significant losses (e.g. insertion loss and return loss) to the network. Thus, there exists a technical problem of an inefficient antenna that manifests reduced efficiency, significant losses (i.e. insertion loss and return loss) and has a large size that is comparable to an operating wavelength and thus, the conventional antenna is not suitable for use in a broadband or an ultra broadband wireless network.

Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with the conventional antenna.

SUMMARY

The present disclosure seeks to provide a microstrip antenna with an integrated band pass filter for use in an ultra broadband wireless network. The present disclosure seeks to provide a solution to the existing problem of an inefficient antenna that manifests significant losses (i.e. insertion loss and return loss) and has a large size that is comparable to an operating wavelength, and not suited for use in a broadband or an ultra broadband wireless network. An aim of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in prior art, and provides an improved antenna with an integrated band pass filter with an improved efficiency, low losses, and a compact size for use in the ultra broadband wireless network.

The object of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.

In one aspect, the present disclosure provides a microstrip antenna for operating in an operational frequency range, comprising an antenna structure printed within a compact area on a substrate. The microstrip antenna further comprises a feedback structure printed within the compact area on the substrate, wherein the feedback structure is configured to operate as an impedance matching bandpass filter with a passband defining the operational frequency range.

The microstrip antenna of the present disclosure creates a matching network with bandpass characteristics. The disclosed microstrip antenna integrates a bandpass filter into an antenna structure. By using the bandpass filter as part of the antenna structure, it becomes possible to create a considerable compact design. The bandpass filter has the advantages of a distributed filter while having relatively small dimensions in comparison to a conventional distributed filter. In this way, the disclosed microstrip antenna possesses significantly low losses and a compact design. The disclosed microstrip antenna reduces an electromagnetic coupling between the integrated antennas by use of the bandpass filter and hence, reduces electromagnetic interference among the integrated antennas. Moreover, the disclosed microstrip antenna significantly reduces the influence of aging of SMD elements in comparison to a conventional lumped SMD filter and increases the reliability. Additionally, the disclosed microstrip antenna does not require an additional space on a main printed circuit board (PCB) and also has no negative effect on antenna efficiency in comparison to the conventional lumped SMD filter. Thus, the disclosed microstrip antenna provides a high efficiency, low losses and a compact size because of the integrated bandpass filter and suitable for use in an ultra broadband wireless network.

In an implementation form, the feedback structure comprises two stub feedback lines arranged on two sides of a feeding point of the antenna structure. The two stub feedback lines are used to create a bandpass filter and the created bandpass filter decouples a nearby antenna operating in an adjacent frequency band and hence, reduces an electromagnetic interference between the disclosed microstrip antenna and the nearby antenna. The bandpass filter is created by tuning the impedance of the disclosed microstrip antenna through variation of its dimensions and the dimensions of the two stub feedback lines.

In a further implementation form, each of the two stub feedback lines ends close to the feeding point of the antenna structure.

The two stub feedback lines ends close to the feeding point of the antenna structure and thus, enables the microstrip antenna to have a more compact design.

In a further implementation form, each of the two stub feedback lines runs along an edge of the compact area.

Each of the two stub feedback lines is used as a compact bandpass and matching filter that is integrated into the disclosed microstrip antenna on a same printed circuit board (PCB). This enables the microstrip antenna to have a more compact design.

In a further implementation form, the compact area is essentially rectangular or square-shaped, with a height and a width each in the range of 15 mm to 20 mm.

Since both the antenna structure and the feedback structure are fabricated within the compact area on the substrate, it leads to a more compact size of the miscrostrip antenna and hence, manifests low losses as well, when in operation.

In a further implementation form, the antenna structure comprises a monopole antenna.

The two stub feedback lines create a bandpass filter which can be used with the monopole antenna for automotive applications.

In a further implementation form, the antenna structure comprises a dipole antenna.

In this case the feedback structure comprises four feedback lines as each monopole element of the dipole antenna requires two feedback lines to create a bandpass filter therefor.

In a further implementation form, the operational frequency range is from about 3.3 GHz to about 5.0 GHz.

The disclosed microstrip antenna can be used at microwave frequencies and particularly, for C- band applications, for example, automotive applications. It has to be noted that all devices, elements, circuitry, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1 is an illustration of a microstrip antenna, in accordance with an embodiment of the present disclosure;

FIG. 2 is a graphical representation that illustrates bandpass characteristics of a microstrip antenna, in accordance with an embodiment of the present disclosure;

FIGs. 3A-3B illustrate transformation from bandstop to bandpass in Smith Chart for a microstrip antenna, in accordance with an embodiment of the present disclosure; FIGs. 4A-4B illustrate transformation from bandstop to bandpass in terms of amplitude versus frequency for a microstrip antenna, in accordance with an embodiment of the present disclosure;

FIG. 5A is a graphical representation that illustrates frequency response of feedback stub lines of a microstrip antenna, in accordance with an embodiment of the present disclosure;

FIG. 5B is a graphical representation that illustrates bandpass characteristics of a microstrip antenna, in accordance with an embodiment of the present disclosure; and

In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the nonunderlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.

FIG. 1 is an illustration of a microstrip antenna, in accordance with an embodiment of the present disclosure. With reference to FIG. 1 , there is shown a microstrip antenna 100. The microstrip antenna 100 includes an antenna structure 102, a substrate 104, a first stub feedback line 106A, a second stub feedback line 106B, a feeding point 108 and an electrical ground 110. The feeding point 108 and the electrical ground 110 are represented by dashed sections which are used for illustration purpose only and do not form a part of circuitry.

The microstrip antenna 100 is configured to operate in an operational frequency range (e.g. 3.3GHz-5GHz). The microstrip antenna 100 is used for C-band applications (i.e. 3.3GHz-5GHz), for example, automotive applications. The microstrip antenna 100 may also be referred as a radiating device. An array of such microstrip antennas or one or more microstrip antennas, may be used in a wireless communication system. Examples of such wireless communication systems include, but is not limited to, an active base station antenna system, an automotive antenna system (AAS), a base station (such as an Evolved NodeB (eNB), a Next Generation NodeB (gNB), and the like), a repeater device, a customer premise equipment, and other customized communication hardware.

The microstrip antenna 100 comprises the antenna structure 102 printed within a compact area on the substrate 104. The microstrip antenna 100 further comprises a feedback structure printed within the compact area on the substrate 104, wherein the feedback structure is configured to operate as an impedance matching bandpass filter with a passband defining the operational frequency range. The microstrip antenna 100 comprises the antenna structure 102 and the feedback structure on the substrate 104 and hence, enables a more compact design. The feedback structure acts as a bandpass filter and therefore, the microstrip antenna 100 reduces the impact on nearby antennas which operate on adjacent frequency bands and thus, provides a high efficiency. The antenna structure 102 and the feedback structure are composed of metal (or metals), for example, a copper metal. The bandpass characteristics of the microstrip antenna 100 is described in detail, for example, in FIG. 2.

In accordance with an embodiment, the feedback structure comprises two stub feedback lines arranged on two sides of the feeding point 108 of the antenna structure 102. The feedback structure is implemented by use of the two stub feedback lines which are represented as the first stub feedback line 106A and the second stub feedback line 106B. The first stub feedback line 106A acts as a filter 1 and is arranged on right side of the antenna structure 102. The second stub feedback line 106B acts as a filter 2 and is arranged on left side of the antenna structure 102. The two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) are used to tune an impedance of the antenna structure 102 by varying its dimensions and to create a bandpass filter. Thus, the microstrip antenna 100 comprises an antenna (particularly, C-band antenna) properties and a bandpass filter properties by virtue of the antenna structure 102 and the feedback structure, respectively. The two stub feedback lines may also be referred as quasi stub feedback lines. The bandpass characteristics of the two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) are described in detail, for example, in FIG. 5A.

In accordance with an embodiment, each of the two stub feedback lines ends close to the feeding point 108 of the antenna structure 102. The two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) end close to the feeding point 108 of the antenna structure 102in order to create quasi-transmission lines between the antenna structure 102 and the two stub feedback lines. Additionally, this feature enables the microstrip antenna 100 to have a more compact design. In accordance with an embodiment, each of the two stub feedback lines runs along an edge of the compact area. The two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) lie along the edge of the compact area on the substrate 104 and enables the antenna structure 102 and the feedback structure to be fabricated on a single printed circuit board (PCB) without requiring a much larger space.

In accordance with an embodiment, the compact area is essentially rectangular or squareshaped, with a height and a width each in the range of 15 mm to 20mm. In some implementations, the compact area is essentially rectangular or square-shaped, with the height and the width each of 15 mm, 16 mm, 17 mm, 18 mm, 19 mm upto 16mm, 17mm, 18mm, 19mm, or 20mm, respectively. In this embodiment, the compact area of the substrate 104 of the microstrip antenna 100 has a width and a height of 17mmx17mm, respectively. It is to be understood by a personal of ordinary skill in the art that the shape of the compact area may be polygonal or round without limiting the scope of the disclosure as long as it is compact.

In accordance with an embodiment, the antenna structure 102 comprises a monopole antenna. The antenna structure 102 can be used as a monopole antenna based on this application. In the embodiment, the antenna structure 102 is used as a monopole antenna. Therefore, the microstrip antenna 100 comprises the monopole antenna (by use of the antenna structure 102) and a bandpass filter (by use of the two stub feedback lines, i.e. the first stub feedback line 106A and the second stub feedback line 106B).

In accordance with an embodiment, the antenna structure 102 comprises a dipole antenna. The antenna structure 102 can be used as the dipole antenna on requirement basis.

In accordance with an embodiment, the operational frequency range is from about 3.3 GHz to about 5.0 GHz. The microstrip antenna 100 is designed to operate, for example, in C-band (i.e. 3.3GHz-5GHz) for automotive applications. However, it is to be understood by one of ordinary skill in the art that, using similar techniques and structure as disclosed in the present disclosure, the microstrip antenna 100 can be designed to operate in mid band frequencies for fifth generation (5G) of mobile communication such as 3.3GHz-4.2GHz, 3.3GHz-3.8GHz, 4.4GHz- 5GHz, and the like.

Thus, the microstrip antenna 100 comprises the monopole antenna (by use of the antenna structure 102) and a bandpass filter (by use of the two stub feedback lines, i.e. the first stub feedback line 106A and the second stub feedback line 106B). The microstrip antenna 100 integrates the bandpass filter into the antenna structure 102. By using the bandpass filter as part of the antenna structure 102, it becomes possible to create a considerable compact design. The bandpass filter has the advantages of a distributed filter while having relatively small dimensions in comparison to a conventional distributed filter. In this way, the microstrip antenna 100 possesses significantly low losses and a compact design. Moreover, the microstrip antenna 100 significantly reduces the influence of aging of SMD elements in comparison to a conventional lumped SMD filter and increases the reliability. Additionally, the microstrip antenna 100 does not require an additional space on a main printed circuit board (PCB) and also has no negative effect on antenna efficiency in comparison to the conventional lumped SMD filter. Thus, the microstrip antenna 100 provides a high efficiency, low losses and a compact size because of the integrated bandpass filter and suitable for use in an ultra broadband wireless network. The microstrip antenna 100 is also used in automotive antenna system (AAS) in C- band (i.e. 3.3GHz-5GHz) frequencies.

FIG. 2 is a graphical representation that illustrates bandpass characteristics of a microstrip antenna, in accordance with an embodiment of the present disclosure. FIG. 2 is described in conjunction with elements from FIG. 1. With reference to FIG. 2, there is shown a graphical representation 200 that illustrates bandpass characteristics of a microstrip antenna such as the microstrip antenna 100 (of FIG. 1). The graphical representation 200 includes an X-axis 202A that represents frequency in GHz and a Y-axis 202B that represents refelection parameter (S(1 ,1)) in decibels (dB).

In the graphical representation 200, a first line 204 represents bandpass characteristics of the microstrip antenna 100. The bandpass characteristics (represented by the first line 204) of the microstrip antenna 100 includes a passband in a frequency range of 3.3GHz to 5GHz. In the graphical representation 200, a first vertical line 206A represents a lower cut-off frequency (i.e. 3.3GHz) of the passband of the microstrip antenna 100. A second vertical line 206B represents an upper cut-off frequency (i.e. 5GHz) of the passband of the microstrip antenna 100.

Therefore, the frequencies which lie in the passband (i.e. 3.3GHz-5GHz), pass through the microstrip antenna 100 and the remaining frequencies get blocked.

FIGs. 3A-3B illustrate transformation from bandstop to bandpass in Smith Chart for a microstrip antenna, in accordance with an embodiment of the present disclosure. FIGs. 3A-3B are described in conjunction with elements from FIG. 1. With reference to FIG. 3A, there is shown a graphical representation 300A that illustrates bandstop characteristics of a conventional microstrip antenna in Smith Chart. With reference to FIG. 3B, there is shown a graphical representation 300B that illustrates bandpass characteristics of a microstrip antenna such as the microstrip antenna 100 (of FIG. 1) in Smith Chart. Generally, a Smith Chart is a circular plot and used to analyse impedance of an antenna. In the graphical representation 300A, a circular plot 302 represents bandstop characteristics of the conventional microstrip antenna in Smith Chart. In the conventional microstrip antenna, feedback stub lines (or A/4 lines) are used as narrow band bandstop filters (or notch filters). In the graphical representation 300B, a circular plot 304 represents bandpass characteristics of the microstrip antenna 100 (of FIG. 1) in Smith Chart. The feedback stub lines (i.e. 2/4 lines) of the conventional microstrip antenna are transformed from the narrow band bandstop filters to the bandpass filter of the microstrip antenna 100 by impedance tuning. The impedance of the microstrip antenna 100 is tuned through variation of the antenna dimensions by use of the two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B). Hence, the microstrip antenna 100 achieves the characteristics of the bandpsss filter over the conventional microstrip antenna. The transformation from bandstop to bandpass filter in terms of amplitude versus frequency is described in detail, for example in FIGs. 4A-4B.

FIGs. 4A-4B illustrate transformation from bandstop to bandpass in terms of amplitude versus frequency for a microstrip antenna, in accordance with an embodiment of the present disclosure. FIGs. 4A-4B are described in conjunction with elements from FIGs. 1 , 3A and 3B. With reference to FIG. 4A, there is shown a graphical representation 400A that illustrates bandstop characteristics of a conventional microstrip antenna. With reference to FIG. 4B, there is shown a graphical representation 400B that illustrates bandpass characteristics of a microstrip antenna such as the microstrip antenna 100 (of FIG. 1).

The graphical representation 400A includes an X-axis 402A that represents frequency and a Y- axis 402B that represents refelection parameter (S11). In the graphical representation 400A, a first line 404 represents bandstop characteristics of the conventional microstrip antenna. In the conventional microstrip antenna, the feedback stub lines are used as narrow band bandstop filters.

The graphical representation 400B includes an X-axis 406A that represents frequency and a Y- axis 406B that represents refelection parameter (S11). In the graphical representation 400B, a first line 408 represents bandpass characteristics of the microstrip antenna 100. The feedback stub lines of the conventional microstrip antenna are transformed from narrow band bandstop filters into bandpass filters of the microstrip antenna 100 by impedance matching.

FIG. 5A is a graphical representation that illustrates frequency response of feedback stub lines of a microstrip antenna, in accordance with an embodiment of the present disclosure. FIG. 5A is described in conjunction with elements from FIGs. 1 and 2. With reference to FIG. 5A, there is shown a graphical representation 500A that illustrates frequency response of feedback stub lines of a microstrip antenna such as the microstrip antenna 100 (of FIG. 1). The graphical representation 500A includes an X-axis 502A that represents frequency and a Y-axis 502B that represents refelection parameter (S11). The feedback stub lines correspond to the first stub feedback line 106A and the second stub feedback line 106B of the microstrip antenna 100.

In the graphical representation 500A, a first line 504 represents frequency response of the first stub feedback line 106A of the microstrip antenna 100. The first stub feedback line 106A acts as a filter 1 for the microstrip antenna 100. A second line 506 represents frequency response of the second stub feedback line 106B of the microstrip antenna 100. The second stub feedback line 106B acts as a filter 2 for the microstrip antenna 100. A third line 508 represents frequency response of the antenna structure 102 of the microstrip antenna 100. The antenna structure 102 acts as a monopole antenna. The first line 504, the second line 506 and the third line 508, collectively represent bandpass characteristics of the microstrip antenna 100, when combined together which is described in detail, for example, in FIG. 5B.

FIG. 5B is a graphical representation that illustrates bandpass characteristics of a microstrip antenna, in accordance with an embodiment of the present disclosure. FIG. 5B is described in conjunction with elements from FIGs. 1 , 2 and 5A. With reference to FIG. 5B, there is shown a graphical representation 500B that illustrates bandpass characteristics when frequency responses of feedback stub lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) and the monopole antenna (i.e. the antenna structure 102) of the microstrip antenna 100 are combined. The graphical representation 500B includes an X-axis 510A that represents frequency and a Y-axis 510B that represents refelection parameter (S11).

In the graphical representation 500B, a first line 512 represents bandpass characteristics of the microstrip antenna 100. The bandpass characteristics of the microstrip antenna 100 (represented by the first line 512) are obtained by combining frequency responses of the two stub feedback lines (i.e. the first stub feedback line 106A and the second stub feedback line 106B) and the monopole antenna (i.e. the antenna structure 102) of the microstrip antenna 100, which are represented by the first line 504, the second line 506 and the third line 508, respectively, of FIG. 5A.

The microstrip antenna 100 is designed, specifically, for C-band frequencies, having a passband of 3.3GHz - 5GHz, while any frequency which is less than 3.3GHz and higher than 5GHz gets blocked, to be used for automotive applications such as automotive antenna system (AAS) and the like. However, using similar techniques and structure as disclosed in the present disclosure, the microstrip antenna 100 can be designed to operate in different frequency bands, such as lower frequency band for mobile communication (i.e. 618MHz - 960MHz), middle frequency band for mobile communication (i.e. 1.42GHz - 2.2GHz), higher frequency band for mobile communication (i.e. 2.30GHz - 2.69GHz), lower frequency band for wifi communication (i.e. 2.40GHz - 2.49GHz), higher frequency band for wifi communication (i.e. 5.15GHz - 5.87GHz), lower frequency band for bluetooth low energy communication (i.e. 2.40GHz - 2.48GHz), different frequency bands of global navigation satellite system, CAR2X (i.e. 5.85GHz - 5.92GHz) and the like.

Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.

Claims

1 . A microstrip antenna (100) for operating in an operational frequency range, comprising: an antenna structure (102) printed within a compact area on a substrate (104), and a feedback structure printed within the compact area on the substrate (104), wherein the feedback structure is configured to operate as an impedance matching bandpass filter with a passband defining the operational frequency range.

2. The antenna of claim 1 , wherein the feedback structure comprises two stub feedback lines arranged on two sides of a feeding point (108) of the antenna structure (102).

3. The antenna of claim 2, wherein each of the two stub feedback lines ends close to the feeding point (108) of the antenna structure (102).

4. The antenna of claim 2 or 3, wherein each of the two stub feedback lines runs along an edge of the compact area.

5. The antenna of any of claims 1 to 4, wherein the compact area is essentially rectangular or square-shaped, with a height and a width each in the range of 15 mm to 20 mm.

6. The antenna of any of claims 1 to 5, wherein the antenna structure (102) comprises a monopole antenna.

7. The antenna of any of claims 1 to 5, wherein the antenna structure (102) comprises a dipole antenna.

8. The antenna of any of claims 1 to 7, wherein the operational frequency range is from about 3.3 GHz to about 5.0 GHz.