Wireless device

Abstract

A wireless multi-band device comprises a radiating system comprising a ground plane layer, a boosting element, and a radiofrequency system, wherein the radiofrequency system comprises a tunable reactive element.

Claims

1. (canceled)

2. A wireless device comprising: a ground plane layer having a maximum size smaller than half of a longest free-space operating wavelength of the wireless device; a boosting element having a largest dimension smaller than ⅙ times the longest free-space operating wavelength; and a radiofrequency system comprising a tunable reactive circuit including: a switch connected between the boosting element and a transceiver, and a bank of fixed matching networks, wherein at least a portion of an orthogonal projection of the boosting element onto a plane containing the ground plane layer overlaps the ground plane layer.

3. The wireless device of claim 2, wherein a matching within the bank of fixed matching networks comprises a series inductor.

4. The wireless device of claim 2, wherein a matching within the bank of fixed matching networks comprises a parallel LC circuit.

5. The wireless device of claim 2, wherein the boosting element has a largest dimension smaller than 1/10 times the longest free-space operating wavelength.

6. The wireless device of claim 2, wherein the boosting element has a largest dimension smaller than 1/20 times the longest free-space operating wavelength.

7. The wireless device of claim 2, wherein the boosting element has a largest dimension smaller than 1/30 times the longest free-space operating wavelength.

8. The wireless device of claim 2, wherein the ground plane layer has a maximum size smaller than ⅓.sup.rd of the longest free-space operating wavelength.

9. The wireless device of claim 2, wherein the ground plane layer has a maximum size smaller than ¼.sup.th of the longest free-space operating wavelength.

10. The wireless device of claim 2, wherein the ground plane layer has a maximum size smaller than ⅕.sup.th of the longest free-space operating wavelength.

11. The wireless device of claim 2, wherein the ground plane layer has a maximum size smaller than 1/10.sup.th of the longest free-space operating wavelength.

12. The wireless device of claim 2, wherein the wireless device operates in two frequency regions.

13. The wireless device of claim 12, wherein the wireless device operates in a first frequency region from 698 MHz to 960 MHz and in a second frequency region from 1710 MHz to 2690 MHz.

14. A wireless device comprising: a ground plane layer having a maximum size smaller than half of a longest free-space operating wavelength of the wireless device; a boosting element having a largest dimension smaller than ⅙ times the longest free-space operating wavelength; and a radiofrequency system comprising a matching network including a tunable reactive element, wherein at least a portion of an orthogonal projection of the boosting element onto a plane containing the ground plane layer overlaps the ground plane layer.

15. The wireless device of claim 14, wherein the matching network includes three reactive elements.

16. The wireless device of claim 15, wherein the matching network includes an inductor connected in series with a parallel arrangement of circuit elements including a tunable capacitor and an inductor.

17. The wireless device of claim 14, wherein the matching network includes a tunable capacitor.

18. The wireless device of claim 14, wherein the matching network includes a tunable capacitor arranged in parallel with an inductor.

19. The wireless device of claim 14, wherein the matching network includes a tunable inductor and a passive capacitor.

20. The wireless device of claim 19, wherein the tunable inductor comprises a switch and a bank of fixed inductors.

21. The wireless device of claim 14, wherein the matching network includes a tunable inductor and a tunable capacitor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Some embodiments will now be described with reference to the figures.

[0033] FIG. 1a shows an example for a wireless device 100 comprising a ground plane layer 152, a radiation booster 151 and a radiofrequency system 153.

[0034] FIGS. 1b, 1c, and 1d show two different examples for ground plane layers that may be used in a wireless device according to the invention.

[0035] FIG. 1e shows an excerpt of an example for a ground plane layer that may be used in a wireless device according to the invention.

[0036] FIG. 2a shows a radiofrequency system according to the prior art.

[0037] FIGS. 2b and 2c show radiofrequency systems which may be used in a wireless device according to the present invention.

[0038] FIGS. 3a, 3b, 3c, 3d, 3e and 3f show a comparison of a reflection coefficient of the prior art with reflection coefficient of a radiofrequency system tuned to different values.

[0039] FIG. 4a shows a radiofrequency system according to the prior art.

[0040] FIGS. 4b and 4c show radiofrequency systems which may be used in a wireless device according to the present invention.

[0041] FIGS. 5a, 5b, 5c, 5d, and 5e show a comparison of a reflection coefficient of the prior art with an exemplary reflection coefficient of a radiofrequency system tuned to different values.

DETAILED DESCRIPTION

[0042] Fig. la shows a wireless device 100. In this particular example, the wireless device is a cell phone comprising a radiating system with a ground plane layer 152, a boosting element 151 and a radiofrequency system 153. The particular example shown in FIG. 1a is antennaless, i.e., it does not have a separate antenna element in addition to the ground plane layer. In other embodiments, the wireless device may be a different wireless device, for example one of the wireless devices mentioned above.

[0043] FIGS. 1b and 1c show examples for ground plane layer and boosting element arrangements which can be used in exemplary wireless multi-band devices.

[0044] For example, ground plane layers used in radiating systems may have a size between 100 mm and 160 mm in one direction (length) and between 40 mm and 80 mm in a direction perpendicular to it (width). Ground plane layers typically have, i.e., for example, less than 1/10 of the width and/or length, for example, less than 1/100 of the width and/or length. Ground plane layers used in smartphones may, for example have a size between 50 to 60 mm in width and between 120 and 150 mm in length. They may, for example, have a rectangular shape.

[0045] The ground plane layer may be printed on a dielectric layer or material. The dielectric layer may, for example, be between 0.5 mm and 4 mm high. As long as the ground plane layer fits on the dielectric layer, its length and width can have arbitrary values in any size. Typically, both length and width of the dielectric layer are much larger than the height of the dielectric layer, for example it may have a width of between 40 mm and 120 mm and a height between 100 mm and 180 mm. If a dielectric material is used, it typically has a flat surface in at least the area to which the ground plane layer is printed. Dielectric layers and materials which may be used for this may, for example, comprise FR4 or other similar materials, and these materials may have a relative permittivity (dielectric constant) of between 3.8 and 4.5, for example a relative permittivity of approximately 4.15. The tangent of the loss angle δ (tan δ) of the dielectric layer or material may have a value in an area between 0.005 and 0.03, in particular between 0.011 and 0.015, in particular for example approximately 0.013.

[0046] The boosting elements may have a greatest length of between, for example, 15 mm and 35 mm.

[0047] In the example of FIG. 1b, the ground plane layer 142 may have a size of approximately 120 mm in length and 60 mm in width and may, for example, be printed on a 1 mm high FR4 layer with a permittivity of approximately 4.15. The tangent of the loss angle δ may approximately be 0.013 (tan δ=0.013). Other sizes for the ground plane layer and/or the boosting element and/or the ground plane layer being printed on a different material are also comprised by the invention.

[0048] FIG. 1b also shows an exemplary clearance area 143 around the boosting element 141 which extends along nearly the entire width of the ground plane layer 142 (with the exception of a small strip 144). Such a small strip 144 may have in one direction (e.g., its width, which along the same direction as the width of the ground plane layer) an extension of less than 1/10 of the width of the clearance area 143 (width again considered in the same direction as the width of the ground plane layer). This small strip 144 serves to connect the boosting element 141 with the ground plane layer 142. The strip may, for example, have a substantially straight or L-shaped form. It may follow the external contour of a printed circuit board (PCB) on which it may be present. In some embodiments, a portion of the strip may be curved to follow a path around a mechanical obstacle such as a screw, a post, an electronic component or the like.

[0049] The boosting element 141 may have dimensions of between 10 mm to 14 mm by 1 mm to 5 mm by 0.4 mm to 4.4 mm. For example, it may be a RUN Antenna booster, and it may have dimensions of approximately 12 mm×3 mm×2.4 mm in the particular example shown in FIG. 1b.

[0050] To match such a radiating system as shown in FIG. 1b, for example for the frequency regions 824-960 MHz and 1710-2690 MHz, six passive components are needed. In FIG. 2a, an example for a prior art radiofrequency system is shown. The indicated capacities and inductivities are exemplary. Other values may be used in other embodiments.

[0051] FIG. 2b shows a radiofrequency system with a tunable capacitor. This can, for example, be used for matching a system as shown in FIG. 1b. In the system shown in FIG. 2b, the capacitor is tunable (the value of 1.311 pF is only one example for possible values).

[0052] FIG. 2c shows schematically how to couple three reactive elements 1, 2 and 3 for a radiofrequency system, wherein one is a tunable capacitor 1 (variable capacitor C.sub.var) and two are passive reactive components, in this case inductors 2 and 3, in order to provide a radiofrequency system for a radiating system according to FIG. 1b. In particular, the left connection point of FIG. 2c may be connected with the boosting element. The right connection point may be connected to the transceiver or input/output of the radiofrequency system of the wireless device.

[0053] Here, the inductor 2 is coupled in series with a system comprising a parallel arrangement of an inductor 3 and the tunable capacitor 1.

[0054] FIGS. 3a to 3f show how the reflection coefficient changes depending on the capacitance value of the tunable capacitor.

[0055] In particular, FIGS. 3a to 3f each show a comparison of a reflection coefficient for a radiofrequency system as of FIG. 2a (marked by X) with the reflection coefficient achieved with a matching system according to FIG. 2b (marked by rectangles) for a single value of capacitance of the tunable capacitor.

[0056] The capacitance of the corresponding tunable capacitor is 1.6 pF for FIG. 3a, 1.1 pF for FIG. 3b, 0.95 pF for FIG. 3c, 0.8 pF for FIG. 3d, 0.58 pF for FIGS. 3e, and 0.45 pF for FIG. 3f. In FIG. 3a, the radiating system operates in the frequency region corresponding to the GSM1800 standard, in FIG. 3b, the radiating system operates in the frequency region corresponding to the GSM850 and GSM1900 standard, in FIG. 3c, the radiating system operates in the frequency region corresponding to UMTS, in FIG. 3d, the system operates in the frequency region corresponding to the GSM900 standard, and in FIG. 3e in the frequency region corresponding to the LTE2300 standard. In FIG. 3f, the system operates in the frequency region corresponding to the LTE2500 standard.

[0057] With three reactive components 1, 2, and 3, it is possible to match from 824-960 MB and from 1710-2690 MHz. In addition, for several frequency standards, for example GSM850, GSM900, and GSM1800 and LTE2500, the system comprising a tunable reactive element provides better matching than the solution using only passive components. Such a better matching may, in particular, result in better antenna efficiency. In addition, a radiofrequency system with a tunable reactive element may reduce the losses due to matching processes because a reduced number of components is used in comparison with the passive reactive elements solution.

[0058] In the system according to FIG. 2c, when considering the input impedance of the system with a single L series, capacitive impedance is present for low frequency regions, for example the frequency regions between 824-960 MHz. At the same time, there is an inductive impedance for high frequency regions, for example 1710-2690 MHz.

[0059] For low frequency regions, a single L series has to be used to bring the impedance into resonance, for the high frequency region, a capacitor has to be used. In examples of wireless multi-band devices, an LC-shunt is used in series with an inductor. For the low frequency region, the combination of LC is equal to C, for the high frequency region, it is equal to L. Since there is a tunable capacitor in this shunt, the radiofrequency systems has enough degrees of freedom to match both the low frequency region and the high frequency region.

[0060] FIG. 1c shows a ground plane layer and boosting element alternative to the one of FIG. 1b. In FIG. 1c, the ground plane layer 132 exemplarily has a size of 120 mm in one direction and of 60 mm in a direction perpendicular to it, is printed on a 1 mm high layer of FR4, a permittivity of 4.15 and tanδ=0.013, and the boosting element 131 has the form of a rectangular box with the length of 20 mm, a width of 3 mm, and a height of 1 mm. Other sizes for the ground plane layer and/or the boosting element and/or the ground plane layer being printed on a different material are also comprised by the invention.

[0061] FIG. 1c also shows an exemplary clearance area 133 around the boosting element 131 which extends along nearly the entire width of the ground plane layer 132 (with exception of a small strip 134). Such a small strip 134 may have in one direction (e.g., its width, measured in the same direction as the width of the ground plane layer) an extension of less than 1/10 of the width of the clearance area 133 (width again considered in the same direction as the width of the ground plane layer) and serves to connect boosting element 131 with the ground plane layer 132.

[0062] According to the prior art, for the matching such a radiating system, a radiofrequency system comprising at least six (lumped) components is required to match such a boosting element in several frequency regions in the areas 698-960 MHz and 1710-2690 MHz. FIG. 4a shows a prior art radiofrequency for matching such a system. Here, seven (lumped) components are shown. However, the inductive component LP=81 nH can be neglected, such that matching may also be achieved with six (lumped) components.

[0063] When using a tunable capacitor, matching in the areas between 698-960 MHz and 1710-2690 MHz can be achieved using one (passive) inductor 2 and one tunable capacitor 1, as shown for example in FIG. 4b and schematically in FIG. 4c. FIG. 4b shows a particular example of a radiofrequency system including examples for particular values that may be used. In the example of FIG. 4b, the capacitor is tunable. In other examples, one tunable inductor and one (passive) capacitor may be used (not shown).

[0064] Corresponding reflection coefficients for such a system are shown in FIGS. 5a to 5e. Herein, the capacitance varies from 1.38 pF in FIGS. 5a to 1pF in FIG. 5b, 0.86 pF in FIG. 5c, 0.56 pF FIGS. 5d, and 0.4 pF in FIG. 5e.

[0065] FIGS. 5a to 5e show how the reflection coefficient changes depending on the capacitance value of the tunable capacitor.

[0066] In particular, FIGS. 5a to 5d each show a comparison of a reflection coefficient for a radiofrequency system as of FIG. 4a (marked by triangles) with the reflection coefficient achieved with a matching system according to FIG. 4b (marked by rectangles) for a single value of capacitance of the tunable capacitor.

[0067] FIG. 5a shows matching in the areas of GSM1800 and GSM1900 and the frequency range between 698 MHz and 750 MHz, FIG. 5b shows a matching in the frequency region of 750 MHz to 798 MHz, FIG. 5c shows a matching to the frequency region used by the UMTS standard, FIG. 5d in the frequency region used for LTE2300, and FIG. 5e in the frequency region used for LTE2500.

[0068] FIG. 1d shows another ground plane layer and boosting element alternative. In FIG. 1d, the ground plane layer 152 has a reduced clearance area 153 with regard to the one in FIG. 1b and 1d extending over nearly the entire width of the ground plane layer. In FIG. 1d, also a remaining strip 154 of the ground plane layer connecting the ground plane layer and the booster.

[0069] FIG. 1e shows another ground plane layer and boosting element alternative in which the boosting element is arranged overlapping onto the ground plane layer.

[0070] As can be seen, the use of a tunable reactive element in a radiofrequency system may improve the matching and/or reduce the number of boosting elements and/or reduce the number of components of the radiofrequency system.