WO2007135230A1

WO2007135230A1 - Speaker and integrated antenna module

Info

Publication number: WO2007135230A1
Application number: PCT/FI2007/050236
Authority: WO
Inventors: Pasi Keskitalo; Jyrki Mikkola
Original assignee: Pulse Finland Oy
Priority date: 2006-05-18
Filing date: 2007-04-27
Publication date: 2007-11-29
Also published as: FI20065333A0; FI20065333L

Abstract

A magnetic miniature speaker (230) which has at least one inductive component in series with one end of the coil wire for shifting the resonance frequency of a speaker circuit being located in the radio frequency range. The component(s) is/are supported to the dielectric jacket (234) of the speaker either directly or over a small circuit board (238) fastened to the jacket. Such a speaker can be a part of an integrated antenna module, which has a radiator of the planar antenna of a radio apparatus, and the dielectric part of which functions as both a radiator support and a speaker chamber. Resonances of the speaker circuit, which interfere with the function of the antenna become effectively removed from the operating frequencies of the antenna, because the components of interference elimination are close to the coil of the speaker. Furthermore, there is no need to consider the interference elimination of the antenna in designing the audio part of the circuit board of the radio apparatus, which means savings in the costs of the circuit board.

Description

Speaker and integrated antenna module

The invention relates to a speaker and a module intended for small-sized radio devices, the module including both this speaker and the radiator of the antenna of the device.

Decreasing the number of separate components is a common aim in technical devices, because a smaller number means lower manufacturing costs and better reliability. Furthermore, it assists in decreasing the size of the structure, which is especially desirable in mobile phones and other portable radio apparatuses. One possibility is to position the speaker of the radio apparatus to the structure of its antenna so that they constitute a physically integral module, in which case no separate space is required for the speaker.

Figs. 1a and 1b show an example of such a known integrated antenna module. Fig. 1a shows the antenna module 100 mounted on the circuit board PCB of a radio apparatus, and Fig. 1 b shows a cross section of the module and the circuit board, the section going through the speaker. The antenna is an internal planar antenna, and the antenna module 100 comprises the planar radiator 110 of the antenna, the dielectric support part 120 and the speaker 130. The radiator is connected by a feed conductor 106 to the antenna port of the radio apparatus and by a short-circuit conductor 105 to the ground plane GND on the upper surface of the circuit board so that an antenna of PIFA (planar inverted F-antenna) type is constituted. The dielectric support part 120 keeps the radiating plane at a certain distance from the ground plane. Such a distance is required for the antenna to function properly, and from it follows that the antenna unavoidably takes a certain space in the radio apparatus. The speaker 130 is a capsular component which comprises a cylindrical permanent magnet MAG and its cup-shaped extension part 131 , a coil 132 in the field of the magnet, a movable speaker diaphragm 133, a jacket 134 and contacts connected to the ends of the coil wire. The circular diaphragm 133 is fastened from its edges to the jacket 134, and the coil 132 is fastened to the diaphragm for generating a force effect proportional to the value of alternating current to the diaphragm. The speaker is positioned in a space between the radiator and the ground plane. For keeping it in place, the dielectric support part 120 comprises a cylindrical shell shaped support frame 123 of the speaker visible in Fig. 1 b in which frame the speaker is fastened from its jacket e.g. by gluing or by ultrasonic welding. The main parts of the dielectric support part, a frame 121 and a bottom 122, constitute an almost closed box. This box prevents the speaker from short-circuiting acoustically and thus functions as a speaker chamber. From the front side of the speaker diaphragm 133, in Fig. 1b from above, leads out a mechanical sound canal, and the inner space of the speaker chamber remains acoustically on the back side of the diaphragm. Thus, the inner space of the antenna becomes utilised in two ways: the speaker itself does not demand a separate space, nor is there a need to separately make a relatively spacious chamber for it, required for sound quality.

On the circuit board PCB, there is an audio amplifier AMP the output of which is connected to the speaker by a first 141 and a second 142 audio conductor. The audio conductors are here conductor strips on the surface of the circuit board and extend below the antenna module where they are connected through vias in the bottom 122 of the dielectric support part to the contacts of the speaker. These contacts are not seen in Fig. 1 b. Instead, aforementioned vias in the bottom have been drawn into sight, even though they do not reside just in the sectional plane presented in Fig. 1 b.

The coil of the magnetic speaker together with its feed circuit and surrounding conductors has several resonance frequencies above audio frequencies. These will in brief be called the resonances of the speaker circuit. Some of these resonance frequencies can locate in the operating band of the antenna of the radio apparatus. In such a case, the radiation and reception characteristics of the antenna are deteriorated in a certain frequency range around the resonance frequency in question because the speaker and the antenna are so close to each other. Thus a disadvantage of integrating the speaker and the antenna is that the speaker can interfere with the function of the antenna, although the audio and ra- dio frequencies are very far from each other. For diminishing this disadvantage, the known structure shown in Fig. 1a has two coils in the feed circuit of the speaker on the circuit board PCB: a first coil CL1 in series with the first audio conductor 141 , and a second coil CL2 in series with the second audio conductor 141. The purpose of the coils is to prevent the resonance frequencies of the speaker circuit from falling on the operating band(s) of the antenna.

A disadvantage of the solution according to Fig. 1a is that it is difficult to effectively remove the disadvantageous resonances of the speaker circuit from the operating band of the antenna by means of components added on the circuit board, i.e. interference effect readily remains in the function of the antenna. Furthermore, the solution necessitates taking the interference elimination of the antenna into ac- count in the design of the circuit board of the radio apparatus, which increases the costs of the circuit board.

From the publication EP 1703 585 is known a speaker of mobile phone, comprising series inductors with the coil conductor in order to prevent the speaker circuit to resonate at radio frequencies. The coils are located on the vibrating speaker diaphragm. A disadvantage of the solution is that it is laborious causing significant production cost.

The object of the invention is to eliminate aforementioned disadvantages related to prior art. The speaker according to the invention is characterised by what is pre- sented in the independent claim 1. The antenna module according to the invention is characterised by what is presented in the independent claim 7. Some advantageous embodiments of the invention are described in the other claims.

The basic idea of the invention is the following: To a magnetic miniature speaker is added at least one inductive component in series with one end of the coil wire for shifting a resonance frequency of the speaker circuit being located in the radio frequency range. The component(s) is/are supported to the dielectric jacket of the speaker either directly or over a small circuit board fastened to the jacket. Such a speaker can be included in a module which comprises the radiator of the planar antenna of a radio apparatus and the dielectric part of which functions as both the radiator support and the speaker chamber.

An advantage of the invention is that the resonances of the speaker circuit, which interfere with the function of the antenna become effectively removed from the operating frequencies of the antenna. This is because the components of the interference elimination are close to the coil of the speaker. A further advantage of the invention is that there is no need to consider the interference elimination of the antenna in designing the audio part of the circuit board of the radio apparatus, which means savings in the costs of the circuit board. Regarding the speaker, the extra costs are minor.

The invention will now be described in detail. The description refers to the accom- panying drawings in which

Figs. 1a,b show an example of the integrated antenna module according to prior art, Fig. 2 shows an example of the speaker according to the invention, Fig. 3 shows the speaker according to Fig. 2 seen from below, Fig. 4 shows a second example of the speaker according to the invention, Fig. 5 shows a third example of the speaker according to the invention, and

Fig. 6 shows an example of the integrated antenna module according to the invention.

Figs. 1a and 1 b were already described in connection with the description of prior art.

Fig. 2 shows an example of the speaker according to the invention. It comprises a permanent magnet, its cup-shaped extension part 231 which constitutes the bottom of the speaker, a coil in the field of the magnet with its contacts, a movable speaker diaphragm and a jacket 234 similarly to the known speaker shown in Fig. 1 b. The speaker 230 has been drawn sloping from below so that its lower side and side surface are visible. The lower side of the speaker means in this description the side of the aforementioned bottom and the upper side means correspondingly the side of the speaker diaphragm. The speaker 230 further comprises a miniature circuit board 238, which embraces inductive components L1 and L2 according to the invention. The miniature circuit board is fastened on the lower surface of the jacket 234 of the speaker which surface is so much above the bottom of the speaker that the miniature circuit board with its components does not extend below the bottom plane. The board 238 follows the shape of the jacket 234 so that, seen from below, it remains inside the circle defined by the outer surface of the jacket.

In this description and claims, said inductive components are called inductors as a distinction from the coil of the speaker. In this example, the inductors are physically chip components. The first inductor L1 is connected to one end of the coil wire of the speaker and the second inductor L2 to the other end of the coil wire. The connections take place via the speaker contacts which are covered by the miniature circuit board 238 in Fig. 2.

The jacket 234 of the speaker has vertical holes HLE. These function as a sound canal from the speaker diaphragm to the speaker chamber when the speaker has been mounted.

Fig. 3 shows the speaker 230 according to Fig. 2 seen from below and the miniature circuit board 238 unfastened. The board 238 is shown also from the reverse side. Of the speaker 230 are also visible its contacts 235 and 236 which are the type of spring contacts. The contacts are fastened on the speaker jacket 234 inside this and their free ends are below the lower surface of the jacket.

The reverse side of the miniature circuit board comes against the lower surface of the jacket 234. On the reverse side of the board there are two counter contacts, the first counter contact CT1 of which makes a contact to the first speaker contact 235 and the second counter contact CT2 to the second speaker contact 236, when the miniature circuit board has been mounted. From the first counter contact CT1 there is a via to the component side of the board 238 to a first conductor pad CP1 and from the second counter contact CT1 there is a via to a second conductor pad CP2. On the component side, the first inductor L1 has been soldered between the first and a third conductor pad from which third conductor pad extends a short intermediate strip to a first surface contact CTA. Correspondingly, the second inductor L2 has been soldered between the second and a fourth conductor pad from which fourth conductor pad extends a short intermediate strip to a second surface contact CTB. The first and the second surface contact are next to each other and they are connected to the lead-through pins of the bottom of the speaker chamber, when the speaker has been mounted to the integrated antenna module.

The integrated antenna module being mounted in a radio device, aforementioned lead-through pins are connected further to the audio conductors of the device and through these to an audio amplifier. In accordance with the above-described, the inductors L1 and L2 are in series with the audio conductors relatively close to the speaker coil. The inductance of the inductors is of the order of 10-100 nH, which means e.g. at the frequency of 1 GHz an absolute value of the impedance of a couple of hundred ohms. From this follows that in the speaker circuit the transmis- sion line constituted by the audio conductor and the ground is seen from the speaker coil as a considerably different impedance than without the inductor in series, in which case the radio-frequency resonances of the speaker circuit shift on the frequency scale. If a resonance frequency falls on the operating band of the antenna, it is made to shift adequately aside by rating the inductors suitably.

Fig. 4 shows a second example of the speaker according to the invention. Of its basic structure, the speaker 430 is similar to the speaker 230 described in Figs. 2 and 3. A difference to this is that there is no miniature circuit board for the insertion according to the invention, but the required conductor strips and pads have been directly processed on the surface of a dielectric speaker jacket 434. Because of this, there also are no spring contacts in the speaker. One end of the coil wire of the speaker is connected inside the structure e.g. by soldering to a first conductor strip 435 which is on the inner surface of a hole HLE of the jacket 434 extending to the side of the lower surface of the jacket where there is a first pad CP1 belonging to it. On the lower surface, there is also a third conductor strip at one end of which there is a third pad and which joins at its other end the first surface contact CTA. The first inductor L1 has been soldered between the first and the third conductor pad. Correspondingly, the other end of the coil wire of the speaker is connected inside the structure to a second conductor strip 436 which is on the inner surface of a second hole HLE of the jacket 434 extending to the side of the lower surface of the jacket where there is a second pad CP2 belonging to it. On the lower sur- face, there is also a fourth conductor strip at one end of which there is a fourth pad and which joins at its other end the second surface contact CTB. The second inductor L2 has been soldered between the second and the fourth conductor pad. The first and the second surface contact are relatively close to each other and they are connected to the lead-through pins of the bottom of the speaker chamber when the speaker has been mounted to the integrated antenna module.

Said conductor strips with their pads are constituted e.g. by the in-mould decoration (IMD) technology. Uppermost on the surface contacts there can be an additional metallisation for improving the reliability of contact.

Fig. 5 shows a third example of the speaker according to the invention. Of its ba- sic structure, the speaker 530 is similar to the speakers described in previous figures. The difference to the speaker according to Fig. 2 is the implementation of the miniature circuit board carrying the inductors. Also in Fig. 5, the miniature circuit board 538 is fastened on the lower surface of a speaker jacket 534, but now the board 538 extends outside the jacket seen from below. On the reverse side of the miniature circuit board, there is a first counter contact which makes a contact to the first speaker contact 535, and a second counter contact which makes a contact to the second speaker contact 536. From the first counter contact there is a via to the component side of the board 538 to a first conductor pad CP1 and from the second counter contact there is a via to a second conductor pad CP2. On the component side, the first inductor L1 has been soldered between the first and a third conductor pad from which third conductor pad extends a conductor strip to a fifth conductor pad CP5. Correspondingly, the second inductor L2 has been soldered between the second and a fourth conductor pad from which fourth conductor pad extends a conductor strip to a sixth conductor pad CP6. The fifth and the sixth conductor pad are next to each other at the outer end of the miniature circuit board 538. The speaker being mounted to the integrated antenna module, the board 538 extends through the wall of the speaker chamber outside of it where the fifth and the sixth conductor pad can be connected to audio conductors e.g. by soldering.

Fig. 6 shows an example of the integrated antenna module according to the inven- tion. The antenna module 600 comprises a planar radiator 610 of the antenna, a dielectric support part 620 on the upper surface of which the radiator is situated, and a speaker 630. The dielectric support part constitutes a substantially closed box functioning as a speaker chamber, and a support frame of the speaker in which the speaker is fastened, as in the antenna module 100 shown in Fig. 1. Also the speaker is the type of a magnetic speaker, such as in Fig. 1. The only substantial difference to the known module 100 is that now the speaker comprises an inductor/inductors in series with its speaker coil in order for the resonances of the speaker circuit not to deteriorate the function of the antenna. Thus, the speaker 630 is congruent e.g. with Fig. 2 or Fig. 4.

In Fig. 6 the integrated antenna module 600 has been mounted on the circuit board PCB of a radio apparatus. This circuit board also comprises an audio amplifier AMP which feeds the speaker 630 via audio conductors 641 , 642. No coils CL1 , CL2 seen in the arrangement of Fig. 1 are now required on the circuit board. Nevertheless, the interferences in the function of the antenna caused by the speaker circuit are better prevented than in the arrangement of Fig. 1.

Above was described a module according to the invention, which includes both an antenna radiator and a speaker. As mentioned in the description, described speakers and modules are examples. The invention does not limit the implementation of the antenna otherwise than in that its radiator is for its whole surface in a fixed connection with the dielectric support part of the module. The invention does not limit the implementation of the basic structure of the speaker otherwise than in that it is of magnetic type. The number of the inductors according to the invention can be also one. The way in which the inductor/inductors is/are coupled in series with the coil wire can vary. The component called a speaker can also be a micro- phone of its operation. The inventive idea can be applied in different ways within the limitations set by the independent claims.

Claims

1. A speaker (230; 430; 530) which comprises a permanent magnet, a coil in its field constituted by a coil wire, a movable speaker diaphragm and a dielectric jacket (234; 434; 534) and an inductor (L1 ; L2) in series with at least one end of the coil wire to shift a resonance frequency of a speaker circuit being located in the radio frequency range, characterised in that the inductor(s) (L1 ; L2) are supported to said dielectric jacket (234; 434; 534).

2. A speaker (230; 530) according to claim 1 , which comprises a first speaker contact (235; 535) connected to a first end of the coil wire and a second speaker contact (236; 536) coupled to a second end of the coil wire, characterised in that it further comprises a miniature circuit board (238; 538) fastened to said jacket (234; 534), which board comprises a first inductor (L1 ) connected to the first speaker contact through a via and a counter contact (CT1) and a second inductor (L2) connected to the second speaker contact through a second via and a second counter contact (CT2).

3. A speaker (230) according to claim 2, characterised in that said miniature circuit board (238) is inside outer edge of the jacket (234), seen in the direction of the normal of said speaker diaphragm.

4. A speaker according to claim 3, characterised in that said miniature circuit board (238) comprises a first surface contact (CTA) connected to the first inductor

(L1 ) and a second surface contact (CTB) connected to the second inductor (L2) to couple the speaker to an external audio circuit.

5. A speaker (530) according to claim 2, characterised in that, to couple the speaker to an external audio circuit outside the jacket, said miniature circuit board (538) extends outside the jacket (534) and on the circuit board there are conductor strips in series with the inductors extending to conductor pads (CP5, CP6) outside the jacket.

6. A speaker (430) according to claim 1 , characterised in that it comprises a first (435), a second (436), a third and a fourth conductor strip which are of the conductive coating of the dielectric jacket (434), a first end of the coil wire being connected to the first conductor strip (435), a first inductor (L1 ) being connected between the first and the third conductor strip, which third conductor strip joins at its other end a first surface contact CTA, a second end of the coil wire being connected to the second conductor strip (436), a second inductor (L2) being con- nected between the second and the fourth conductor strip, which fourth conductor strip joins at its other end a second surface contact CTB, which surface contacts exist for coupling the speaker to an external audio circuit.

7. An integrated antenna module (600) which comprises a radiator (610) of a planar antenna, a dielectric support part (620) and a speaker (630), which dielectric support part constitutes a substantially closed box functioning as a speaker chamber and a support frame of the speaker, in which frame the speaker is fastened, characterised in that the speaker (630) is in accordance with claim 1 to keep at least one operating band of the antenna clear of the resonance frequen- cies of the speaker circuit.

8. An antenna module according to claim 7, characterised in that conductors of the speaker are connected from surface contacts (CT3, CT4) outside the antenna module by lead-through pins on the bottom of the speaker chamber.

9. An antenna module according to claim 7, characterised in that said induc- tors of the speaker are chip components.