An antenna system

2. Applicants:

a. Name: Robert Bosch Engineering and Business Solutions Private Limited

Nationality: INDIA

Address: 123, Industrial Layout, Hosur Road, Koramangala, Bangalore - 560095, Karnataka, India b. Name: Robert Bosch GmbH

Nationality: GERMANY

Address: Feuerbach, Stuttgart, Germany

Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.

Field of the invention

[0001] This invention is related to an antenna system.

Background of the invention

[0002] Conventional techniques for employing conducting plates or strips configured in different shapes as antennas for transmitting and receiving radio frequency signals of different frequencies are limited by a major difficulty that the bandwidth provided by the antennas for such transmissions are not sufficiently broad and also the space occupied on the circuit boards. The demand for the lesser space occupancy is ever increased for portable communication systems as more communication transmissions are rapidly increased and greater crowd of users are causing 'traffic jams' in different frequency-bands. Most of the traditional antennas employed by mobile communication systems are extendible types. It is well known fact in the art that the performance characteristics of these antennas are functions of the height of the antenna. Due to the design considerations of simplicity, convenience of use, serviceability, reliability, and price, internal antennas are increasingly replacing the external extendible antennas. The internal antennas not only provides a design configuration to overcome the difficulties and limitations of the external antennas mentioned above, it further enhances the portability of the communication systems since the antennas can be conveniently placed as a standalone system without special radio frequency cables.

[0003] A prior art document US5644319 discloses a Multi-resonance horizontal-U shaped antenna. A novel design of high frequency hidden hand-held antenna which includes two metal arms above a lower arm of finite ground plane. By properly choosing the lengths of these arms and the separations between them, the bandwidth can be broadened more than 20%.

Brief description of the accompanying drawings

[0004] Figure 1 illustrates an antenna system, in accordance with an embodiment of an invention; [0005] Figure 2 illustrates the antenna, according to an embodiment of the invention;

[0006] Figure 3 illustrates an impedance matching network of the antenna system, according to an embodiment of the invention;

[0007] Figure 4 illustrates a graph comprising multiple frequency values mapped to multiple bandwidth values of the antenna, according to an embodiment of the invention, and

[0008] Figure 5 illustrates a graph comprising multiple efficiency values mapped to multiple frequency values, according to an embodiment of the invention.

Detailed description of the embodiments

[0009] Figure 1 illustrates an antenna system, in accordance with an embodiment of the invention. The antenna system 10 comprises an antenna 12 having a first portion 14, a second portion 16 and a third portion 18. The first, the second and the third portions (14, 16, 18] are made of different dimensions to each other.

[0010] Further the construction of the antenna system and the components of the antenna is explained in detail as follows. The antenna 12 is made in the shape of an inverted U or an arc. However, the shape of the antenna 12 is not restricted to the inverted U, but can be any help which makes the entire system compact as known to a person skilled in the art The antenna is soldered on a Printed Circuit Board (PCB] 30 that has multiple plane structures. The antenna 12 is soldered on at least one plane, which is a top plane 28 of the PCB 30. The antenna 12 comprises plurality of pins (11, 13] made on each end/edge of the antenna 12. According to one embodiment of the invention, each end of the antenna 12 comprises three pins.

[0011] A first set of three pins 11 on one end of the antenna 12 is categorized into two supporting pins 22 and an electric pin 24. The two supporting pins 22 are used for mechanical support to hold the antenna 12 on the top plane 28 of the PCB 30. The electric pin 24 is used to transmit and receive signals from an external source. According to one embodiment of the invention, the signal is a radio frequency signal. The two supporting pins 22 and the electric pin 24 is made on the longer side in the first portion 14 of the antenna 12. A second set 13 of three pins on the other end of the antenna 12 are categorized into grounding/shorting pins 26. The shorting pins 26 are used to short the antenna 12 to the ground. The shorting pins 26 of the antenna 12 are made on the shorter side in the third portion 18 of the antenna 12.

[0012] A contour of the second portion 16 reduces in the direction from the first portion 14 to the third portion 18. The first portion 14 is made longer than the second portion 16 and the second portion 16 is made longer than the third portion 18. The length is reduced from the first portion 14 to the third portion 18 keeping the width constant, thus altering the area of the portions (14, 16, 18). The first, the second and the third portions (14, 16, 18) of the antenna 12 are made as a single component. The width of at least one portion of the antenna (the main part of the antenna above the pin portion) and the width of at least one pin is adjusted based on the requirement to improve the mechanical reliability in high vibration environments. According to one embodiment of the invention, an additional loading of the antenna structure is achieved in terms of slot/opening of metal in one or more number of regions. The formed slot can take any of the basic shapes comprising rectangular, circular, elliptical etc. or combination of them to have a better efficiency.

[0013] Figure 2 illustrates the antenna, according to an embodiment of the invention. A cut-portion 29 is made on either side of the antenna 12 in the second portion 16 to fit the geometry into a product-housing contour. The antenna 12 is made of a bendable metal element The metal element is chosen from a group of metals, which are electrically good conductors like steel, copper, aluminum, silver etc. The antenna 12 made of the bendable metal element is used to resonate at a frequency band like 1 GHz to 2 GHz. The space constraint on the PCB 30 to mount the antenna 12 is solved by the above disclosed design as it is compact to fit even in a smaller places when compared to the conventional polygonal shaped antenna. The width and the height of the antenna 12 is maintained at a predefined levels, such that, the efficiency of the antenna 12 is not reduced. The top plane 28 of the PCB 30 where the antenna 12 is mounted is used for an improved radiated performance in the lower frequency bands with an additional impedance matching network.

[0014] A distance between a feeding pin 24 and at least one shorting/ground pin 26 is maintained at a predefined value during the manufacturing of the antenna 12, to optimize an input impedance and a bandwidth of the radio frequency signal. In the above-disclosed design, the resonating frequencies of the structure are chosen at two frequencies over the broader frequency range. With the above-disclosed design, the antenna structure will operate in two resonant modes (For example, at 1000MHz and 2200MHz] These resonance frequencies are realizable at the electric / feeding pin 24, such that, the antenna 12 is operated efficiently over the broader frequency range, ex. from 699MHz to 960MHz & 1700MHz to 2700MHz. The location of the electric/ feeding pin 24 and the shorting/grounding pins 26 on the antenna 12 is optimized to get the optimal radiation performance.

[0015] Figure 3 illustrates an impedance matching network of the antenna system, according to an embodiment of the invention. The antenna 12 uses multiple lumped components like capacitors 54 and inductors 52 as shown in Figure 3. The impedance matching network comprises at least two inductors 52 (a, b, c] and two capacitors 54 (a, b). The impedance matching network composes of shunt inductor 52 (a] right at the feeding point, a series capacitor 54(a] or a parallel combination of a capacitor 54 (a] and an inductor 52(c] in series, with an additional shunt inductor 52 (b] and a series capacitor 54(b] The above-disclosed connection is used to improve the radiation efficiency at lower frequency band, for ex. 699MHz to 960MHz. The radio frequency energy is reflected at the electric/ feeding pin 24 depends on the mode of operation.

[0016] According to one embodiment of the invention, the size of the antenna 12 is made thin and the size (i.e., width] of the pins (22, 24, 26] are made thin to make the system compact and ease to solder on the PCB 30 as shown in the figure 1. According to another embodiment of the invention, the size (i.e., width, length, and height] of the antenna 12 is increased, making it bulkier when compared to the above-disclosed one. The width of the at least two supporting pins (22], and the shorting pins 26 are made wider than the feeding pin 24. The working of the antenna 12 is known to a person skilled in the art. With the above disclosed antenna system, the efficiency of the system 10 increases due to the shape and dimensions of the antenna 12 along with the impedance matching network.

[0017] Figure 4 illustrates a graph comprising multiple frequency values mapped to multiple bandwidth values of the antenna in x-axis and y-axis respectively, according to an embodiment of the invention. The antenna bandwidth is defined as the input reflection coefficient (i.e., the amount of power reflected back from the feeding pin 26] and is maintained less than -6dB in lower band and less than -lOdB in upper band frequency. With the above-disclosed design of the antenna along with the impedance matching network, the bandwidth in the lower band and the upper band frequencies are maintained as defined.

[0018] Figure 5 illustrates a graph comprising multiple efficiency values mapped to multiple frequency values in y-axis and x-axis respectively, according to an embodiment of the invention. For instance, the total antenna efficiency over the frequency range of interest for mobile communication systems (i.e., 699 MHz to 960 MHz, and 1700MHz to 2700 MHZ] is shown in the figure 5. With the above disclosed antenna design, the antenna efficiency has been achieved more than 60% in the lower frequency band (ie.,699MHz to 960MHz] and more than 70% in the upper frequency band ( ie, 1700MHz to 2700MHz] Due to the two resonant modes of the antenna structure along with the antenna impedance matching network, the desired efficiency of the antenna system 10 can be achieved.

[0019] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments 5 and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims