JPH11178093

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DESCRIPTION JPH11178093
[0001]
FIELD OF THE INVENTION The present invention relates to a method and apparatus for
improving the leak tolerance at the handset of a wireless device. The invention can preferably be
used in telecommunications terminals, in particular in mobile stations.
[0002]
BACKGROUND OF THE INVENTION A telecommunications terminal usually includes a receiver
having an earpiece for reproducing received acoustic signals. The handset is usually designed to
produce maximum volume and best sound quality when the handset is in close contact with the
user's ear. If there is a gap or leak between the earpiece and the user's ear, the perceived sound
pressure will usually be significantly reduced. Also, the frequency distribution of the sensed
sound does not match the original acoustic signal, and low frequencies are significantly
attenuated than high frequencies. The ability of the handset to maintain its acoustical properties
when the gap between the handset and the ear changes is called leak tolerance.
[0003]
The problem is particularly acute at the mobile station, since it is rare that the mobile station is
completely in intimate contact with the user's ear. On the other hand, the standards for mobile
stations are mainly based on measurements when a tight seal exists in the gap between the
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mobile station and the artificial ear. The device in the receiver port needs to have very good leak
resistance so that the volume and frequency distribution of the sound reproduced under real
operating conditions conforms to the specification.
[0004]
The following methods for improving leak resistance are conventionally known. Improving
leakage resistance by providing a loose coupling to the membrane that generates sound waves in
the handset capsule and loading it at a relatively large volume located behind the earpiece
capsule it can. The volume behind the handset capsule is most conveniently open, in which case
the aforementioned volume will be as large as possible. Another way to improve leakage
resistance is to reduce the acoustic output impedance of the device by using an acoustic return
path.
[0005]
The drawback of the prior art described above is that it is difficult to optimize the load caused by
the acoustic return path. The leakage resistance to be achieved is essentially dependent on the
size of the volume provided behind the earpiece capsule. In small devices such as mobile stations,
it is not possible to provide a large enough volume to achieve the best acoustical load, as the
electronic unit of the device occupies the volume in the casing of the device.
[0006]
The object of the present invention is to devise an earpiece solution which achieves good leak
tolerance in small radio devices such as mobile stations.
[0007]
One idea of the present invention is to provide an acoustic volume behind the handset using the
RF shield casing of the radio frequency unit of the device.
The purpose of the RF shield is to prevent radio frequency signals formed by wireless devices,
such as mobile stations, from entering the surrounding environment, and RF radiation present in
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the surrounding environment can interfere with the RF circuitry of the device. To prevent. The
present invention utilizes this type of RF shield volume as an acoustic volume acting as a load on
the handset.
[0008]
A particular advantage of the present invention is that an acoustic volume can be formed behind
the handset that acts as the best load on the handset without unnecessarily increasing the size of
the device.
[0009]
In one embodiment of the invention, one wall of the casing provided behind the earpiece is
formed by an electronic circuit board to which the radio frequency components of the electronic
unit are coupled.
An acoustic path can be preferably formed between the casing and the external volume by a
through hole provided in the circuit board.
[0010]
SUMMARY OF THE INVENTION A first acoustical device wherein a sound formed by a receiver
capsule is defined from the front of the receiver capsule by the user's ear and the housing
portion between the receiver capsule and the ear. The method according to the invention for
improving the leak resistance of a receiver of a wireless device to be directed to a volume,
wherein the sound formed by the receiver capsule is further defined by a casing from the back of
the receiver capsule. And 2) characterized by being directed to the radio shielded volume of the
radio device acting as an acoustic volume.
[0011]
A housing portion capsule, a housing portion located between the handset capsule and the user's
ear and defining a first acoustic volume between the user's ear, a front portion of the handset
capsule and a first acoustic volume The device of the present invention, which is provided
between the first and second sound paths, and which comprises a first acoustic path for directing
sound from the front of the earpiece capsule to the acoustic volume, the device of the invention
being defined by a casing A wireless shielded volume provided for the RF portion of the wireless
device, and a second acoustic path for directing the sound formed by the receiver capsule from
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the back of the receiver capsule to the wireless shielded volume And the like.
[0012]
The handset of the mobile station according to the invention is a handset capsule and a housing
part situated between the handset capsule and the user's ear, defining an acoustic volume
between the housing part and the user's ear The moving part and the first acoustic path provided
between the front of the receiver capsule and the acoustic volume to direct sound from the front
of the receiver capsule to the acoustic volume, the movement The station comprises a radio
shielded volume provided for the RF part of the mobile station defined by a casing and the sound
formed by the receiver capsule to improve the leak resistance of the handset opening. And a
second acoustic path for directing from the back of the handset capsule to the radio shielded
volume.
[0013]
Preferred embodiments of the invention are presented in the dependent claims.
[0014]
As used herein, the terms front and back of the earpiece capsule refer to the front and back of
the membrane that is within the earpiece capsule to produce sound waves, and these are the
acoustic waves generated at the front and back. Are in antiphase with each other.
[0015]
As used herein, the term receiver port means the receiver port capsule and the acoustic and
mechanical structure coupled thereto.
[0016]
The invention will now be described in detail with reference to the accompanying drawings.
[0017]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a prior art
handset 100. As shown in FIG.
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It has a receiver capsule 101 that converts electrical signals into sound.
The handset capsule 101 is connected at its edge 102 to the handset housing 103.
The sound waves formed by the receiver mouth capsule occur in the volume 104 between the
receiver mouth 101, the edge 102 and the housing 103, from which the sound waves pass
through the holes 105 to the external volume of the housing.
Between the housing 103 and the ear 106 there is a volume 107 which is closed in the best case.
If the handset is part of a mobile station, the housing 103 is preferably a cover of the mobile
station.
[0018]
In the solution shown in FIG. 1, the leak tolerance is improved by providing an acoustic volume
111 behind the handset capsule.
From the earpiece capsule, an acoustic coupling to the volume is formed by one or more holes
110 located at the back of the earpiece capsule.
The acoustic volume is defined by a casing consisting of an RF shield 116 and a circuit board
112. The RF shield 116 is made of a conductive material such as a metal plate. Circuit board 112
preferably has holes that acoustically couple volume 111 to the volume surrounding volume
111. In circuit boards, holes with plated-through edges are used to electrically couple the wires
located in different foil layers of the circuit board. These approximately 0.2 mm diameter holes
can be used to form the acoustic path. FIG. 1 also shows the RF component 117 of the radio
frequency unit coupled to the circuit board 112.
[0019]
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Thus, while an acoustic return path of the receiver capsule can be provided through the volume
surrounding the entire device, Figure 1 also shows how to provide an internal acoustic return
path of the device. The acoustic return path includes the hole 110 in the back of the receiver
capsule, the acoustic volume 111 behind the receiver capsule, the hole 113 in the RF shield
casing of the circuit board, the hole 114 of the circuit board outside the RF shield casing, the
circuit It consists of a volume between the substrate and the housing part and a hole 115 at the
front edge of the receiver capsule. The volume provided for the acoustic return path between the
circuit board and the housing part can be further surrounded by a special second casing, but
with the usual casing of the device such as the mobile station and the components therein It may
be configured.
[0020]
The ability to improve leak tolerance with the solution shown in FIG. 1 is due to the fact that the
acoustic volume provided behind the handset and the acoustic return path provided through it
are particularly low frequency at the handset Based on the fact that it acts as an acoustic loading
of the capsule, in this case fluctuations of the external loading have only a small relative effect on
the total acoustic loading of the earpiece capsule.
[0021]
FIG. 2 shows an acoustic equivalent circuit of the handset of FIG.
In this circuit, the receiver capsule forms a pressure wave and acts as an acoustic source 201 and
has an internal impedance 204. The pressure wave propagates through the hole in the casing out
of the earring device, which forms an impedance 205 and the external volume forms a load
impedance 206. In FIG. 1, the boundary between the handset and the external volume is labeled
207. The acoustic return path formed by the volume surrounding the device acts as a feedback
impedance 213, and the internal acoustic return path of the device acts as a feedback impedance
215. The load impedance 206 mainly consists of the load caused by the ear and the load
resulting from the leak between the earpiece and the ear. From this equivalent circuit, it can be
seen that the feedback impedance can reduce the effect of variations in load impedance 206 on
the acoustic output being transferred to the load. The feedback impedance 213 is shown as a
dashed line, which indicates that the compensation effect of this impedance is small compared to
the feedback impedance 215.
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[0022]
FIG. 3 shows another embodiment of the present invention for improving the receiver's leak
tolerance. The device comprises a receiver capsule 301 which converts electrical signals into
sound. The receiver capsule 301 is coupled to the housing portion 303 at its edge 302. The
sound waves formed by the receiver mouth capsule are generated in the volume 304 between
the receiver mouth capsule 301 and the edge 302 and the housing portion 303, from which the
sound waves are passed through the hole 305 forming the first acoustic path. Move to the
outside volume. A first volume 307 is defined between the housing portion 303 and the ear 306.
If the handset is part of a mobile station, the housing part is preferably the cover of the mobile
station.
[0023]
In the solution shown in FIG. 3, the leak tolerance is improved by providing an acoustic volume
acting as a load on the handset capsule according to the invention behind the handset capsule.
The acoustic volume also acts as an RF shielded volume of the radio frequency unit. The acoustic
volume is defined by a casing consisting of an RF shield 316 and a circuit board 312. The sound
produced by the receiver capsule 301 is directed through the aperture 310 to the acoustic
volume 311. The circuit board 312 preferably has holes 313, 314 that couple the acoustic
volume 311 to the volume surrounding the acoustic volume. FIG. 3 also shows the RF component
317 of the radio frequency unit coupled to the circuit board 312.
[0024]
In the embodiment shown in FIG. 3, an acoustic return path is provided from the back of the
receiver capsule 301 to the first volume 307. The RF shield 316 may be provided with holes 318
for this acoustic path, or the acoustic return path may be directed through the holes 313, 314 of
the circuit board 312. A hole 320 is additionally provided in the housing portion of the handset
for the acoustic return path.
[0025]
The volume provided on the side of the mouthpiece capsule is closed with a special casing 330 in
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the solution of FIG. Volumes 311 and 331 may not necessarily be volumes separated from one
another, and may form one RF shielded composite volume.
[0026]
The ability to improve the leak tolerance in the solution shown in FIG. 3 is based on the fact that
an acoustic return path, especially provided for low frequencies, acts as an acoustic load for the
earpiece capsule at low frequencies, In this case, external load variations have only a small
relative effect on the total acoustic loading of the earpiece capsule. When the acoustic return
path is directed to the volume between the ear and the housing part, it is possible to utilize the
small volume behind the earpiece capsule and still obtain the best loading at low frequencies.
Thus, for example, when applied to a mobile station, this arrangement of the invention does not
significantly increase the size of the mobile station and does not affect its shape.
[0027]
The holes 320 in the housing portion 303 provided to form the second acoustic path are
preferably in the same size range as the holes 305 provided for the first acoustic path. Thus,
none of the embodiments of the present invention have a noticeable effect on the appearance of
the device.
[0028]
FIG. 4 shows a simplified acoustic equivalent circuit of the handset of FIG. In this circuit, the
receiver capsule acts as a sound source 401 that generates a pressure wave, to which an internal
impedance 404 is further coupled. The pressure wave propagates through the hole in the casing
out of the earring device, which forms an acoustic impedance 405 and the external volume forms
a load impedance 406. In FIG. 4, reference numeral 407 is attached to the boundary between the
handset and the external volume. An acoustic return path directed between the user's ear and the
housing portion acts as a feedback impedance 420. From this equivalent circuit, since the
feedback impedance compensates for the effect of the hole 305 of the casing, ie the effect of the
acoustic impedance 405, the effect of the change of the load impedance 406 on the acoustic
output transferred to the load is a feedback impedance It can be seen that it can be reduced to a
minimum by 420. Comparing this embodiment of the invention with the solution shown in FIG. 2
achieves a constant pressure level (corresponding to the voltage of the electrical circuit) to the
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listener's ear 406 with a constant impedance value as viewed from the source. The acoustic
volume velocity (corresponding to the current of the electric circuit) required for the second
embodiment is relatively small in the second embodiment of the present invention in which the
effect of the feedback impedance 420 is larger than the effect of the feedback impedance 213 of
FIG. Recognize. This means that less movement of the membrane is required in the earpiece
capsule to achieve a given level of audibility.
[0029]
The application of the invention to mobile stations will now be considered. First, the operation of
a conventional mobile station will be described with reference to FIG. 5, and then the mechanical
structure of the mobile station of the present invention will be described with reference to FIG.
[0030]
FIG. 5 is a block diagram of a mobile station according to an embodiment of the present
invention. The mobile station comprises the parts normally provided in this type of device, such
as a microphone 531, a keyboard 537, a display 536, a receiver port 501, a transmit / receive
coupling 538, an antenna 539 and a control unit 535. The figure also shows a transmit block
534 and a receive block 541 that are typically provided at the mobile station.
[0031]
The transmission block 534 has functions required for speech coding, channel coding,
encryption and modulation, and RF functions. The receive block 541 has the corresponding RF
functions and the functions necessary for demodulation, decoding, channel decoding and speech
decoding. The signal originating from the microphone 531 and amplified in the amplification
stage 532 and converted to digital form in the A / D converter is transferred to the transmission
block 534, usually to the speech coding element contained in the transmission block. The
transmit signal shaped, modulated and amplified by the transmit block is sent to antenna 539 via
transmit / receive coupling 538. The received signal is sent from the antenna via transmit /
receive coupling 538 to receive block 541 which demodulates the received signal and performs
decoding and channel decoding. The audio signal received as the final result is transferred to the
amplifier 543 via the D / A converter 542 and further sent to the receiver port 501. The control
unit 535 controls the operation of the mobile station, reads the control commands given by the
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user from the keyboard 537 and sends a message to the user via the display 536.
[0032]
The portions of the mobile station to be RF shielded are included in blocks 538, 534 and 541.
The RF portions of the transmit block 534 and the receive block 541, such as the circuitry that
forms the RF frequency signal, may be partially common to the transmit and receive chains.
[0033]
When the handset device of the present invention is used, the frequency response of the handset
may be different from the frequency response of prior art devices. The filter included in the
amplifier 543 allows the frequency response to be compensated in an analog manner. Another
way is to perform compensation in conjunction with digital signal processing in the digital signal
processor (DSP) of block 541. When correcting the frequency response in the digital signal
processor, it is not always necessary to change the components, and the correction can be
performed by making necessary additions to a program for controlling the digital signal
processor.
[0034]
FIG. 6 shows the mechanical structure of the mobile station 600 of the invention viewed from the
front and from the side. The side view (b) is enlarged 2: 1 compared to the front view (a) and
shows a cross-section A-A of the part of the handset according to the invention. The front view
(a) shows a microphone 631, a keyboard 637, a display 636 and an antenna 639 included in a
conventional mobile station. At the top of the mobile station there can be seen a hole 605
forming a first acoustic path leading from the front of the earpiece capsule to the outside of the
device and a hole 620 which is part of a second acoustic path. In the cross-sectional view (b), the
RF shielded volume 611 provided behind the earpiece capsule is also seen. The volumes 611 and
631 do not necessarily have to be separated, and may form one composite volume. The housing
of the earpiece between the earpiece and the user's ear is preferably a cover 603 of the device at
the mobile station where the other mechanical parts of the earpiece are coupled.
[0035]
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As can be seen in FIG. 6, both the handset and the antenna are located at the top of the mobile
station. Since the RF part is directly coupled to the antenna circuit, the placement of the RF shield
in relation to the receiver port is also a good RF technical solution.
[0036]
In the above, the Example of the solution of this invention was described. The principles of the
invention may of course be modified within the scope defined by the claims, for example by
modifying the details and scope of use of the specific structure.
[0037]
According to the present invention, good leak resistance can be achieved in a small radio
apparatus such as a mobile station.
[0038]
Brief description of the drawings
[0039]
1 is a diagram showing a receiver according to the present invention for improving the leak
resistance of the receiver.
[0040]
2 is a diagram showing an acoustic equivalent circuit of the handset device of FIG.
[0041]
FIG. 3 shows another arrangement of the invention for improving the leak tolerance of the
handset.
[0042]
4 is a diagram showing an acoustic equivalent circuit of the handset device of FIG.
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[0043]
FIG. 5 is a block diagram of a conventionally known mobile station to which the present
invention can be preferably applied.
[0044]
6 is a front view and a side view of the mobile station of the present invention.
[0045]
Explanation of sign
[0046]
DESCRIPTION OF SYMBOLS 100 Receiver opening 111 Sound volume 112 Electronic circuit
board 112,116 RF shield and casing 113,114 Through hole 117 Radio frequency component
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