Wireless terminal, wireless module and method of manufacturing such a terminal

The invention relates to wireless terminals. The invention is particularly, but not exclusively applicable to multiple standard telephones that are operable in accordance with telephone standards such as GSM (880 to 960 MHz), DCS (1710 to 1880 MHz) and PCS (1850 to 1990 MHz) and optionally Bluetooth RTM (ISM band in the 2.4 Ghz range).

The invention also relates to wireless modules having an antenna system and at least those components that are included in the coupling stages.

Furthermore, the invention relates to a method of manufacturing such a terminal.

In the development of successive generations of cellular telephones, a great deal of effort has been made to reduce the volume of the wireless terminal, with the attendant desire to reduce the volume of the antenna whilst still maintaining its sensitivity. Externally mounted monopole antennas have been succeeded by internal antennas such as PIFAs (Planar Inverted-F Antennas) and notch antennas (see, for instance, patent document WO 03/094346). However, more efforts have to be made to further reduce the volume of the terminal and to facilitate its manufacture.

It is an object of the invention to use all parts of the terminal in an efficient way.

According to the invention, a wireless terminal formed from a module comprising a substrate, RF components, an antenna system and a linkage part for linking the antenna to the substrate is characterized in that at least one RF component, which may be a part of the coupling stages, is placed in the vicinity of the linkage part.

In accordance with a first aspect of the invention, the RF parts are placed so as to raise the PCB ground (substrate).

In accordance with a second aspect of the invention, at least one RF component is mounted on the linkage part.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 shows a terminal according to the invention.

FIG. 2 shows a wireless module in accordance with a first embodiment of the invention.

FIG. 3 shows a wireless module in accordance with a second embodiment of the invention.

FIG. 4 shows a wireless module in accordance with a third embodiment of the invention.

FIG. 5 shows a wireless module in accordance with a fourth embodiment of the invention.

FIG. 6 shows a wireless module in accordance with a fifth embodiment of the invention.

In the drawings, corresponding features are denoted by the same reference numerals.

FIG. 1 shows a wireless terminal 1 . This terminal comprises a housing and a wireless module shown in FIG. 2 . In FIG. 1 , the housing of the terminal 1 is provided with a screen 5 , various buttons 7 , a microphone 9 and a loudspeaker 10 .

The module shown in FIG. 2 is constituted by a main board 20 formed from a PCB (printed-circuit board), on which the usual elements or circuits for operation of the terminal are soldered. For the sake of clarity, these elements or circuits are not shown in FIG. 2 . This module comprises an antenna 25 , which is of the PIFA type. An antenna of this type is disclosed, for instance, in patent document WO 03/094346. This antenna, which is placed on an antenna substrate, is linked to the main board 20 via a linkage part 30 .

In accordance with an aspect of the invention, this linkage part is a support for RF (radio frequency) components 32 and 33 . These components are represented schematically above the linkage part. In practice, they can be mounted below this part 30 . Note that FIG. 2 shows a differential slot 37 , a feed tab 40 and a shorting tab 42 . These elements are necessary for operation of the antenna.

Advantageously, the antenna substrate is constituted by a flexible support PCB, which also constitutes the linkage part 30 . Initially, the antenna 25 has a planar structure. It is then bent along the line A-A′ as illustrated in FIG. 2 .

Since there is radiation from both the antenna 25 and the PCB (a voltage is fed between them), the location of the feed is not critical for the performance of the antenna 25 /PCB-coupled system (the main board 26 ). It is realistic to make a sufficient area available on the antenna 25 to accommodate the entire RF circuit, without compromising the overall performance. Indeed, it is possible to improve the RF performance, because RF circuits made on a flexible PCB do not need to be realized above a ground layer. This leads to a more even distribution of current within these components and, consequently, to higher quality factors.

The differential slot 37 , shown in FIG. 2 , is necessary to prevent the antenna 25 from being short-circuited. In this embodiment, this is realized in the part of the structure that is orthogonal to the main PCB, i.e. the part that also supports the RF circuitry or elements. It could also be formed on the antenna top plate (parallel to the main PCB), though this is avoided here to prevent any possibility of user interaction. Indeed, the antenna slot may also be removed to avoid problems associated with user interaction. Instead, the functionality of the slot can be replicated, using discrete components (as disclosed in PCT pending patent application IB2004/002369 filed on 15 Jul. 2004).

A second embodiment of the invention is shown in FIG. 3 . In accordance with this embodiment, the antenna feed 40 and the shorting tab 42 are moved on to the planar part of the antenna 25 . It must be considered in this embodiment that there is likely to be a compromise between the area that can be made available for circuitry and the performance of the antenna when subject to user interaction (the user may put his finger over the feed area of the antenna).

A third embodiment of the invention is shown in FIG. 4 .

The bandwidth and resonance frequency of PIFA antennas strongly depend on the antenna height above the PCB ground. RF modules tend to raise the effective ground level over a localized area, which tends to an increase of the antenna resonance frequency and a reduction of the bandwidth. The extent of this depends on the position of the module. According to the invention, the RF modules 60 , 60 ′ . . . are placed close to the antenna feed 40 . Then, the effect is the least. Indeed, here the local ground level can be significantly increased without adversely affecting the performance of the antenna. To show this, the antenna configurations in FIG. 4 yield results as indicated in Table 1 below.

This Table 1 illustrates the relations between the resonance frequency and the Q of a conventional arrangement (without RF module placed in a prominent way on the main board) and the arrangement illustrated in FIG. 4 .

Raising the PCB ground near the feed raises the antenna resonance frequency but does not degrade the antenna Q and, consequently, the bandwidth. Indeed, the increased resonance frequency may be useful in dual-band applications, because the optimum resonance frequency is at approximately the geometric mean of the two frequencies concerned before the slot is applied. Because of this, RF modules 60 , 60 ′ . . . can be stacked on top of each other without significantly affecting the overall performance. This saves PCB area.

A way of manufacturing a wireless module is shown in FIG. 5 . All parts, namely, part 20 , which already comprises the essential elements ( 70 , 71 , 72 , . . . ) for operation of the module, part 30 , which comprises the RF elements 32 and 33 , and part 25 , which constitutes the antenna, are arranged on the same support and are folded in another manufacturing step so as to give them the required shape. As already mentioned above, an alternative is to put the antenna and the RF elements on a flexible PCB, then link the flexible PCB to the main board 20 and fold them in the same way.

Another interesting embodiment of the invention is shown in FIG. 6 . The wireless module is represented in an unfolded state. This embodiment is based on the recognition that, in principle, a large part of the circuit currently located on the main PCB of a device may be moved on to the antenna part 25 .

In a conventional arrangement, the RF signal is applied between the antenna and the main PCB, such that both contribute to radiation (to some extent). All components are located on the main PCB. This is convenient because all inputs (such as the microphone, keypad, battery, etc.) and outputs (such as the display, loudspeaker, etc.) also connect with the main PCB 25 .

In FIG. 6 , the antenna 25 is considered to be the part above the line A-A′. Its feed point is denoted by reference numeral 40 . The PCB 20 is the part below this line. If the antenna is made with a flexible PCB or MID construction, components 32 , 33 . . . can be located on the antenna structure and it can be considered as an extension of the main PCB. This saves space and allows use of the generally superior substrate used to form the antenna for RF components.

The problem with using the antenna as a circuit substrate is that power and data lines must connect back to the main PCB 20 in order to subsequently connect to required inputs and outputs. Such connections would normally disturb the performance of the antenna. Hence, an antenna is made with a shorting tab 42 that is connected to ground of the main PCB. Data and power lines can then be run above or within this tab without disturbing the performance of the antenna as denoted by reference numeral 80 in FIG. 6 .

The shorting tab will cause an impedance transformation as described in patent document WO 02/06005. A slot between the feed and shorting tabs can be used to control the level of this transformation.

The antenna may be a planar monopole-like structure or a PIFA (wherein folds would be applied along the lines A-A′ and B-B′).