This application is the National Stage entry under 35 U.S.C. § 371 of International Application No. PCT/EP2019/084943 filed Dec. 12, 2019, published as Publication No. WO 2020/126843 on Jun. 25, 2020, which claims benefit of foreign priority of German Patent Application No. 10 2018 132 486.3, filed on Dec. 17, 2018, the entireties of which are herein incorporated by reference.
The invention relates to a microphone capsule, a microphone arrangement with a plurality of microphone capsules, and a method for calibrating a microphone arrangement.
Microphone capsules are components that are used in microphones and that are normally soldered onto circuit boards. Microphone capsules for condenser or electret microphones are often manufactured using the so-called stacking technique, wherein several parts are stacked one after the other in a housing. However, there are component tolerances, resulting in each microphone capsule having individual deviations from a desired ideal electro-acoustic behavior, like e. g. the frequency response and/or phase response. For high quality requirements, and in particular if a plurality of microphone capsules are interconnected in a microphone array, these deviations need to be compensated electronically, e. g. by filtering with a corresponding filter that is individually adapted. For this purpose, the characteristic values such as the frequency response and/or phase response must first be measured. If this measurement is done after soldering the microphone capsule onto a circuit board, the connected circuit may falsify the result. If the measurement is done before the soldering, there occurs the problem that the capsules need to be sorted, depending on the measurement result. This selection, which is error-prone and laborious and often done manually, makes it particularly difficult and expensive to equip circuit boards with microphone capsules by machine. Therefore, only a small proportion of the capsules can be used, namely those with very low deviations, so as to keep the effort low.
The following documents have been considered relevant by the German Patent and Trademark Office (DPMA) for the priority application. DE 10 2012 203 741 A1, US 2008/0 219 483 A1 and Maxim Integrated Products, Inc.: Data Sheet for DS28E04 1-wire EEPROM, San Jose CA, USA, 19-6568; Rev 2; 1/17, 2017, https://datasheets.maximintegrated.com/en/ds/DS28E05.pdf [retrieved on 23 Sep. 2019].
US2008/0219483 A1 discloses an acoustic module that can be used as a microphone array and that comprises two or more microphone capsules, an electronic circuit for signal processing and a memory. After mounting the microphone capsules into the module, they may be tested. The calibration information for the capsules which is obtained in the testing process as well as positional deviations of the capsules within the acoustic module are stored in the memory and are provided to the internal signal processing for configuring filters.
It is an object of the present invention to provide an improved microphone capsule with which an automatic assembly of circuit boards with microphone capsules is facilitated. It is a further object to provide a simplified manufacturing method for microphone arrays and to provide the corresponding microphone arrays.
A microphone capsule according to the invention is disclosed in claim 1. It comprises an electrostatic sound transducer, an amplifier element or impedance converter that outputs an amplified or impedance converted output signal of the electrostatic sound transducer, respectively, and at least one electronic memory element. In the memory element, data may be stored that were obtained by a measurement and that relate to the individual frequency response or phase response of the respective microphone capsule. The data can be read out during the manufacturing process and during operation, which enables both an automatic sorting of the capsules during production as well as an automatic calibration of the target circuitry during operation.
Claim 10 relates to a microphone arrangement, such as e. g. an array, with at least two microphone capsules. Claim 12 relates to a method for calibrating a microphone array.
Further advantageous embodiments are disclosed in the dependent claims.
Further details and advantageous embodiments are depicted in the drawings, showing in
For this, the characteristic values of the capsule such as e.g. the frequency response are measured. In a variant it is also possible to determine deviations against an ideal curve.
An advantage of the microphone capsule according to the invention is that each specimen has its individual characteristic values with it permanently, so that in a simple manner a sorting of the capsules during manufacturing as well as a calibration of the target circuitry during operation is much easier possible. In particular, no measurement is required any more for calibrating the target circuitry. Since manual adjustment and manual sorting always mean an increased production effort, the invention simplifies the production and/or calibration of devices or modules that contain microphone capsules. The measuring of the single microphone capsules is done anyway and is therefore no additional effort. After the capsule is soldered on the board and the circuit is taken in operation, a processor may retrieve during an initialization phase the values stored in the memory element U1 and use them for configuring, individually for each microphone capsule, a corresponding correction circuit. For a microphone capsule having a measurement curve Kr as shown in
In
b) shows exemplarily a similar measurement setup for a digital microphone capsule 200′. An analog-to-digital converter ADC′ is disposed within the microphone capsule 200′, whose output signal DS is a digital signal. In this case, a digital input of the programming device 510′ may be used, instead of an analog input as in
The microphone capsules according to the invention may be used advantageously in particular for microphone arrays, for this requires each microphone capsule to reach ideal values at very small tolerances with respect to magnitude (i.e. absolute value) and phase. For example, a sensitivity tolerance of +/−1 dB may be required over a wide frequency range, for example from 400 Hz to 8 kHz. Instead of manually selecting the microphone capsules during the manufacturing process, the capsules can now be sorted automatically by reading out the measured values from each capsule by a processor before the microphone capsules are soldered, and it is possible to use, for example, only those capsules whose measured values are within certain specified limits. Alternatively or additionally, a processor contained in the device can read out the values of each individual capsule after soldering and commissioning, and can use them to configure an adaptive correction filter individually for the respective capsule. The calibration according to the invention can therefore replace the very costly selection of components, in particular microphone capsules, and thus facilitate the production process. Further, single microphone capsules for example in an array can be replaced at a later time, since the connected circuitry may automatically adapt to the new microphone capsule.
The configuration unit 620, the correction filters 630 and the combination unit 640 may be implemented by one or more appropriately configured processors. Normally, during manufacturing of the microphone array, two or more microphone capsules 6101, . . . , 610n are soldered onto a common circuit board, on which there may also be the processors and possibly further electronic components. In one embodiment, two or more of the microphone capsules 6101, . . . , 610n may share a common serial bus for connecting to the configuration unit in order to read out their measurement values M1, . . . , Mn one after the other. The microphone capsules 6101, . . . , 610n according to the invention enable automatic manufacturing of the circuit board as well as automatic calibration of the microphone capsules, as described above.
In one embodiment, the invention relates to a method for calibrating a microphone array that comprises a plurality of microphone capsules 200.
In one embodiment, separate electronic filters are calculated and configured for each of the at least two microphone capsules in the array. In one embodiment, an electronic filter is jointly calculated and configured for two or more of the microphone capsules.
In the microphone capsule according to the invention, the circuit board comprised therein becomes the carrier of its own calibration data. It may therefore be regarded as a ‘self-calibrating’ capsule. One advantage is that a meaningful correction can already be done with only few stored data (1 kbit, for example). Another advantage is that the target device (i.e. the device into which the microphone capsule is installed) can in a flexible manner control the actual frequency response and the sensitivity of the capsule based on the known target curve. In this manner, the characteristics of the target device may be automatically adjusted within a wide range.
In principle, the invention may also be used for other components or modules that offer space for an additional memory element and that due to tolerances exhibit deviations from a target characteristic that may be corrected electronically. The memory element may also be more complex than the single wire memory element described above, so that it may store more data. The memory element may also use more connections, which however may be electrically separated from the rest of the circuit, as in the examples above. The stored data are individual values of the respective component or the respective module. It may be measurement values or deviations of measurement values from target values, as described above, or values that represent a classification (for example, for deviations of 0-1%, 1-2%, 2-3% etc.); the data may facilitate selection processes during production and/or enable an automatic calibration of the finished product.
Number | Date | Country | Kind |
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10 2018 132 486.3 | Dec 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/084943 | 12/12/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2020/126843 | 6/25/2020 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20030223611 | Hohjyo | Dec 2003 | A1 |
20080075306 | Poulsen | Mar 2008 | A1 |
20080219483 | Klein et al. | Sep 2008 | A1 |
20120230522 | Nowak | Sep 2012 | A1 |
20140266260 | Wurzinger et al. | Sep 2014 | A1 |
20140321664 | Huang | Oct 2014 | A1 |
20160344358 | Oliaei | Nov 2016 | A1 |
20190132693 | Walser | May 2019 | A1 |
20200154223 | Du | May 2020 | A1 |
Number | Date | Country |
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10 2012 203 741 | Sep 2012 | DE |
2004-007156 | Jan 2004 | JP |
20080045037 | May 2008 | KR |
WO 2017105548 | Jun 2017 | WO |
WO 2017143177 | Aug 2017 | WO |
Entry |
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Anonymous. “Model: CMC-4013-SMT-TR—Description: ELECTRET Condenser Microphone Additional Resources: Product Page : 3DModel : PCB Footprint” Nov. 28, 2016 (Nov. 28, 2016), Retrieved Mar. 6, 2020 from Internet Internet:URL:https://www.cuidevices.com/product/resource/cmc-4013-smt-tr.pdf XP055674518, pp. 1, 2, 5. |
International Search Report for PCT/EP2019/084943 dated Mar. 19, 2020. |
German Search Report for Application No. DE 10 2018 132 486.3 dated Sep. 23, 2019. |
Maxim Integrated Products, Inc.: Data Sheet for DS28E04 1-wire EEPROM, San Jose CA, USA, 19-6568; Rev 2; Jan. 17, 2017, https://datasheets.maximintegrated.com/en/ds/DS28E05.pdf [retrieved on Sep. 23, 2019. |
Office Action dated Mar. 28, 2023 issued in the corresponding Japanese patent application No. 2021-534796. |
Number | Date | Country | |
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20220030360 A1 | Jan 2022 | US |