Microphone for capturing sound

Abstract

A microphone for capturing sound is disclosed. The microphone includes a sound head configured to receive a sound input and convert the sound input into an output signal, the output signal including an output voltage VCA, the output voltage VCA having a first nonlinearity at least at a sound pressure level (SPL) above a first threshold. The microphone includes a preamplifier configured to receive the output signal from the head and to generate an output voltage VPA, the output voltage VPA having a second nonlinearity for at least the first input signal level. The microphone is configured such that the sound head and the preamplifier produce a first non-linearity and a second non-linearity of similar amounts, respectively, and wherein the first non-linearity and the second non-linearity are inverted from each other so as to cancel each other and thereby linearize an output signal VMI of the microphone.

Description

Technical Field

[0001] The present invention relates to a microphone for capturing sound, wherein the microphone includes a microphone capsule and a preamplifier. Background Technology

[0002] For high-fidelity microphones used for purposes such as recording or measuring audio, it is desirable to maintain original sound quality even at extremely high sound pressure levels. A problem with traditional microphones is that they struggle to achieve good sound quality as sound pressure levels increase.

[0003] Therefore, a microphone is needed that can capture sound at very high sound pressure levels without distorting it. Summary of the Invention

[0004] A microphone for capturing sound is disclosed. The microphone includes a microphone capsule configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least above a first threshold sound pressure level (SPL).

[0005] The microphone includes a preamplifier configured to receive an output signal from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity with respect to at least a first input signal level.

[0006] The microphone is configured to cause the microphone capsule and the preamplifier to produce similar amounts of a first nonlinearity and a second nonlinearity, respectively, wherein the first nonlinearity and the second nonlinearity are out of phase with each other and thus cancel each other out, thereby linearizing the microphone's output signal V_MI.

[0007] The microphone can be a distortion-free microphone. A microphone includes a microphone capsule configured to receive sound input and convert it into an output signal. Therefore, the microphone capsule converts sound waves into a microphone signal. The output signal includes an output voltage V_CA. The output voltage V_CA exhibits a first nonlinearity at least above a first threshold sound pressure level (SPL). This is likely due to the transduction mechanism of the microphone capsule. Any change in the signal (i.e., the waveform of the signal) as it is passed from input to output can be considered distortion. Nonlinear distortion can refer to the situation where the output signal includes new frequency components not present in the input signal.

[0008] The output voltage V_CA may have a first nonlinearity or multiple nonlinearities at least at a sound pressure level (SPL) above a first threshold.

[0009] Nonlinearity can be defined as the property of mathematical functions or data that cannot be plotted on a straight line, and a system whose output is not proportional to its input.

[0010] Linearity can be defined as a property of a function or mapping where a linear function maps a real line to a line in a plane. The linearity of a mapping is closely related to scaling. Generally speaking, for functions with more than one dimension, linearity refers to the property of the function being compatible with addition and scaling, also known as the superposition principle.

[0011] Therefore, from a mathematical point of view, a linear function can produce an output that is always proportional to the input, amplified or reduced, plus a certain offset, including zero offset.

[0012] From an acoustic perspective, it might be slightly different because the offset (DC component) might not contain any acoustic information. Therefore, in acoustics, a linear system can provide an output where each spectral component of the output signal is proportional to the same spectral component of the input signal with a certain phase shift (often also called a delay), since real systems are likely always causal. This means that a linear system cannot or may not produce new spectral components.

[0013] The sound pressure level can be what's known as a high sound pressure level (SPL). Therefore, the nonlinearity of the microphone capsule may only be significant at high SPLs, and this nonlinearity may stem from asymmetric movement of the diaphragm. In the case of a condenser microphone, this asymmetric movement is caused by an electric field generated inside the capsule, which accumulates charge on the diaphragm and is then used to generate the capsule's output signal. If the microphone is condenser, the diaphragm may be located in front of the backplate or back electrode. The distance between the two may range from 20 µm to 50 µm. When the microphone is positioned at high SPL, diaphragm offset may be limited, at least when pushed towards the backplate. Furthermore, at high SPLs, the electric field generated inside the capsule may no longer be constant for large diaphragm offsets, as the electric field may be stronger when the diaphragm moves towards the back electrode and weaker when it moves away from the back electrode.

[0014] A microphone is a transducer that converts sound into electrical signals. Microphones can be used in many applications, but those most relevant to the types described here are in live and recorded audio engineering, recording, filmmaking, broadcasting, and television broadcasting. Microphones can be of different types, employing different methods to convert changes in air pressure of sound waves into electrical signals. A microphone can be a dynamic microphone, which uses a coil suspended in a magnetic field; or a microphone can be an electret or condenser microphone, which uses a diaphragm or diaphragm as a capacitor plate. Before a signal can be recorded or reproduced, the microphone capsule is connected to a preamplifier.

[0015] The microphone includes a preamplifier configured to receive an output signal from the microphone capsule and generate an output voltage V_PA. The output signal V_PA is provided to the next element in the measurement / recording chain of the microphone or other device. The preamplifier is coupled to the microphone capsule. The output voltage V_PA exhibits a second nonlinearity with respect to at least a first input signal level. The first input signal level can be defined as an input signal with a large amplitude, and the second nonlinearity of the output voltage V_PA may be due to the nonlinear behavior of electrical components used in the preamplifier circuitry. If the input signal from the microphone capsule is not high enough, i.e., does not have a large amplitude, the preamplifier may not produce nonlinearity. Therefore, other levels of input signals, such as those with low amplitudes, may not provide nonlinearity.

[0016] The output voltage V_PA may have a second nonlinearity or multiple nonlinearities for at least the first input signal level.

[0017] The microphone is configured to produce a first nonlinearity and a second nonlinearity of similar magnitudes in the microphone capsule and the preamplifier, respectively. Therefore, the first nonlinearity of the microphone capsule and the second nonlinearity of the preamplifier are similar, such as substantially similar, such as corresponding to each other, such as approximately the same or approximately identical.

[0018] The first nonlinearity of the attack phase and the second nonlinearity of the preamplifier are out of phase with each other. For a sinusoidal signal, when the phase difference φ(t) is 180° (pi radians), the phases are opposite, and the signal is out of phase. Then, the signal has the opposite sign.

[0019] The nonlinear behavior of the microphone capsule is in opposite phase to the nonlinear behavior of the preamplifier in the system.

[0020] Since the first and second nonlinearities are similar, for example, identical but out of phase with each other, the nonlinearities cancel each other out, thus linearizing the microphone's output signal V_MI.

[0021] Therefore, the nonlinearity of the preamplifier (nl_PA) is similar to, for example, equal to, but opposite in phase with, the microphone advance nonlinearity (nl_CA). This will lead to the elimination of the nonlinearity, resulting in very low total harmonic distortion (THD) of the system output V_MI until the clipping point of the system.

[0022] Therefore, when the input signal level is high, the microphone capsule and preamplifier each produce nonlinearities. The microphone capsule and preamplifier are designed to compensate for and cancel each other's nonlinearities, thereby linearizing the microphone's output voltage.

[0023] This is an advantage of the new microphone compared to traditional microphone designs, as it can achieve pristine sound quality at extremely high sound pressure levels. When the sound pressure level exposed to a microphone increases, the output of a traditional microphone begins to be contaminated by acoustic nonlinearity from the capsule and electrical nonlinearity from the preamplifier. Traditionally, manufacturers have addressed this issue by linearizing the nonlinear behavior of the capsule and preamplifier separately. However, the extent to which the capsule can be linearized is limited before compromising other important microphone parameters such as sensitivity and frequency response, and the extent to which the preamplifier can be linearized is also limited before the complexity, size, and cost of the electronics influence the final product design. The new microphone solves this problem by avoiding linearization of the microphone's subsystems—namely, the capsule and preamplifier—and designing them to work together to cancel each other out. In this way, the new microphone goes beyond the classic engineering strategy of minimizing nonlinearity and is able to capture completely distortion-free sound at very high sound pressure levels.

[0024] In some implementations, the nonlinear cancellation effect between the microphone capsule and the preamplifier is associated with a sound pressure level (SPL) above a first threshold, where the first threshold is a high SPL, and where the SPL is between 110 dB SPL and 160 dB SPL. Therefore, the SPL can be a so-called high SPL, and the nonlinearity of the microphone capsule may only be significant at high SPLs. Therefore, the output voltage V_CA has a first nonlinearity at least at SPLs above the first threshold. Thus, the first threshold can be a SPL above approximately 110 dB SPL.

[0025] The sound pressure level can be between approximately 110 dB SPL and 160 dB SPL, such as between approximately 115 dB SPL and 160 dB SPL, such as between approximately 120 dB SPL and 160 dB SPL, such as between approximately 125 dB SPL and 160 dB SPL, such as between approximately 130 dB SPL and 160 dB SPL, such as between approximately 135 dB SPL and 160 dB SPL, such as between approximately 140 dB SPL and 160 dB SPL.

[0026] The sound pressure level can be between approximately 110 dB SPL and 160 dB SPL, such as between approximately 110 dB SPL and 155 dB SPL, such as between approximately 110 dB SPL and 150 dB SPL, such as between approximately 110 dB SPL and 145 dB SPL, such as between approximately 110 dB SPL and 140 dB SPL, such as between approximately 110 dB SPL and 135 dB SPL, such as between approximately 110 dB SPL and 130 dB SPL.

[0027] The output voltage V_CA can also have a first nonlinearity at sound pressure levels (SPL) below a first threshold.

[0028] In some implementations, the first input signal level includes an input signal with an amplitude higher than the second threshold. Therefore, the first input signal level can be defined as an input signal with a large amplitude. Thus, other levels, such as those for input signals with low amplitudes, may or may not provide nonlinearity of the signal.

[0029] In some implementations, the microphone is a condenser microphone, and the microphone capsule includes a diaphragm and a back electrode.

[0030] In some implementations, the microphone is an electret microphone, and the microphone capsule includes a diaphragm and a back electrode.

[0031] In some implementations, the microphone is a dynamic microphone, and the microphone capsule includes a diaphragm and a magnet.

[0032] A condenser microphone, also known as a condenser microphone or an electrostatic microphone, uses a diaphragm or septum that acts as one plate of a capacitor. Audio vibrations cause changes in the distance between the plates. Because the capacitance of the plates is inversely proportional to the distance between them, vibrations produce changes in capacitance. These changes in capacitance are used to measure the audio signal.

[0033] An electret microphone is a type of microphone whose diaphragm or septum forms a capacitor (capacitor) containing an electret. The electret can include a permanent electric dipole that provides a constant charge to the capacitor. Sound waves cause the diaphragm to move, changing the capacitance C, thus producing a corresponding voltage change across the capacitor. The constant charge of the electret eliminates the need for a polarized power supply that might be required with non-electret condenser microphones, although a preamplifier can be used to enhance the audio voltage signal. Preamplifiers may require a small amount of power and phantom power is often used in sound enhancement and studio applications. Electrets are stable dielectric materials with a permanently embedded charge and are durable due to their high resistance and chemical stability.

[0034] A dynamic microphone includes a small, movable induction coil located in the magnetic field of a permanent magnet and attached to a diaphragm or diaphragm. When sound enters the microphone, the sound waves cause the microphone capsule to move. As the diaphragm vibrates, the coil moves within the magnetic field, generating a changing voltage across the coil through electromagnetic induction.

[0035] The components of a fixed plate and a movable plate are called elements or capsules. All of the microphone types described above can be high-fidelity recording microphones. Microphones produce high-quality audio signals and are used in laboratory and recording studio applications. Compared to other microphone types that struggle to achieve this and thus reduce output signal quality, this microphone's advantage lies in its ability to capture a wide frequency range of sound. Microphones require power, and can be connected to a power source, which can be provided as phantom power through the microphone input on the device, or by a small battery or other power source. Power may be needed to establish the voltage of the capacitor plates (e.g., for condenser microphones), and power may also be needed to power the microphone electronics. Depending on the method used to extract the audio signal from the microphone's transducer, the microphone can be a DC-biased microphone or a radio frequency (RF) microphone, etc.

[0036] In some implementations, the microphone is connected to a power source, and the power source is connected to a resistive load (RL). The microphone's preamplifier may be connected to the power source. The power source may be a positive power supply Vsupply. A resistor Rc may be connected as a load (i.e., the resistive load RL) to the positive power supply Vsupply.

[0037] In some implementations, the preamplifier includes an active element Q1.

[0038] In some implementations, the active element Q1 is a transistor.

[0039] In some implementations, the transistor is a junction field-effect transistor (JFET), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a bipolar junction transistor (BJT), such as an NPN BJT.

[0040] The advantage is that the active element Q1, as a transistor, can be a small and standard component, thus occupying very little space in the microphone and potentially being inexpensive and readily available. A smaller active element Q1 allows for a smaller microphone, which is advantageous for some applications. For other applications, such as pencil microphones from DPA microphones, the active element Q1 and therefore the microphone may not need to be very small.

[0041] A transistor is a semiconductor device used to amplify or switch electrical signals and power supplies. It is made of semiconductor material and can have two, three, or more terminals for connection to electronic circuits. The voltage or current applied to one pair of transistor terminals controls the current flowing through the other pair. Because the controlled (output) power can be higher than the controlled (input) power, a transistor can amplify signals.

[0042] Using different transistors (such as junction field-effect transistors (JFETs) or metal-oxide-semiconductor field-effect transistors (MOSFETs) or bipolar junction transistors (BJTs), such as NPN BJTs) may have different advantages. Different transistors may be advantageous for use with different advances, such as capacitors, electrets, moving coils, and circuit designs, such as use with different power supplies.

[0043] The circuit may include a resistor (RC) connected as a load to the positive power supply (Vsupply). Two resistors (RB1 and RB2) can establish a bias voltage for the base of the active element Q1 and for the resistor (RE) acting as local feedback for the active element Q1. Combined with the DC parameters of the active element Q1, resistors RC, RB1, RB2, and RE can establish the operating point (q) for the active element Q1. A microphone capsule can be connected between the base of Q1 and ground via RB1 and RB2.

[0044] The active element Q1 can be a bipolar junction transistor, such as an NPN BJT, which has several inherent nonlinearities built into its manufacturing process and technology. Relevant to this invention is the ohmic nonlinearity, i.e., the current-voltage relationship I. C -V CE The symmetry varies with different currents I B Changes in transmission characteristics.

[0045] For the load line (R) L Given an operation point (q) on ), the same positive (i) Bmax ) and negative (i Bmin Changes in base current will not produce equal positive (i) Cmax ) and negative (i Cmin Changes in collector current cause a change across the load line (R) L This produces a distorted output voltage (V_PA).

[0046] A microphone capsule can be exemplified as an electret microphone capsule, which can be shown as having a capacitance (C). MIC The capacitance of the charging capacitor changes as the diaphragm moves due to the sound pressure level (SPL), thus generating a changing voltage V_CA on the SPL.

[0047] An electret microphone can be viewed as a voltage generator connected in series with a capacitor. When the microphone capsule of the electret microphone is connected to the base of the active element Q1 of a common-emitter voltage amplification preamplifier, the changing voltage output V_CA flows through the resistor R of the preamplifier. in Generates a changing current (i) in i in A portion is modulating the base current (I) of the active element Q1, which is related to the changing SPL. b ).

[0048] The microphone capsule can be, for example, an electret microphone capsule, and it has a built-in nonlinearity (nl_CA) in its manufacturing. This produces a nonlinear output voltage V_CA compared to the sound pressure input. The preamplifier also has a built-in nonlinearity (nl_PA) through its topology.

[0049] This system can be nonlinear and feedback-based. The nonlinear performance of the microphone capsule is out of phase with the nonlinear performance of the preamplifier in this system.

[0050] By selecting the DC operating point (q) of the active element Q1 (given by its transfer characteristics), the load line (R) is selected. L The local feedback (K) causes equal nonlinearity (nl_PA) in the preamplifier 6, but is in opposite phase with the microphone advance nonlinearity (nl_CA), which will lead to the elimination of nonlinearity, resulting in a very low total harmonic distortion (THD) value in the system output (V_MI) until the clipping point of the system.

[0051] The loop gain T = A * K * nl_PA, where A is the gain or amplification of the active element Q1, and K is the local feedback.

[0052] Therefore, the voltage output V_PA of the preamplifier is the voltage output V_CA of the attack phase multiplied by the loop gain T, that is, V_PA = V_CA * T.

[0053] In some implementations, the preamplifier includes a bias circuit and a feedback circuit coupled to the active element Q1. Therefore, both the bias circuit and the feedback circuit can be coupled to the active element Q1.

[0054] In some implementations, the bias circuit is coupled between the capsule and the active element Q1 of the preamplifier.

[0055] In some implementations, the preamplifier's bias circuitry and feedback circuitry are adjusted to counteract the initial nonlinearity of the attack phase.

[0056] In some implementations, a resistive load (RL) is coupled to the preamplifier.

[0057] In some implementations, a resistive load (RL) is coupled to the active element Q1 of the preamplifier.

[0058] In some implementations, the resistive load (RL) is coupled to the preamplifier via a feedback loop, which includes the feedback circuitry of the preamplifier.

[0059] In some implementations, the active element Q1 of the preamplifier is connected to a resistor RC, which is connected to a positive power supply (Vsupp). Resistors RB1 and RB2 of the preamplifier are configured as the base of the active element Q1, and resistor RE, acting as local feedback for the active element Q1, establishes a bias voltage. Alternatively, resistor RC can be connected to the positive power supply (Vsupp) as a load RL.

[0060] In some implementations, the microphone is connected between the base of the active element Q1 and ground between resistors RB1 and RB2.

[0061] In some implementations, the active element Q1 is configured to generate a distortion effect on the output voltage V_PA of the preamplifier, thereby providing a second nonlinearity. Due to the inherent nonlinearity built into the active element Q1, the active element Q1 can generate or provide a second nonlinearity.

[0062] In some implementations, the distortion effect caused by the active element Q1 makes the output voltage V_PA of the preamplifier different from the output voltage without the distortion effect, and wherein the distortion effect is more significant for positive or negative voltages, thereby providing a second nonlinearity.

[0063] In some implementations, the active element Q1 causes the preamplifier to provide a second nonlinearity due to a certain amount of distortion introduced by the resistive load (RL).

[0064] Due to the inherent nonlinearity built into the active element Q1, the active element Q1 can generate or provide a second nonlinearity. The resistive load RL can affect the amount of this second nonlinearity.

[0065] Therefore, a second nonlinearity is provided in the voltage output V_PA of the preamplifier, at least in part because the distortion of the resistive load RL is higher than that of the prior art.

[0066] In some implementations, the output voltage V_CA provided by the microphone capsule has a positive voltage that is greater than a negative voltage, or vice versa, thus providing a first nonlinearity. Because at high sound pressure levels (SPL) (e.g., SPL above a first threshold), the diaphragm of the microphone capsule is dragged more towards the back electrode, the output voltage V_CA provided by the microphone capsule will have a positive voltage that is greater than a negative voltage, or a negative voltage that is greater than a positive voltage. This provides the first nonlinearity. Whether the positive voltage is greater than the negative voltage or vice versa depends on the microphone capsule design. Typically, the back electrode of the microphone capsule will be located at the bottom, and the diaphragm will be located at the top, which will provide a positive voltage that is greater than a negative voltage. However, if the microphone capsule is designed with the back electrode at the top and the diaphragm at the bottom, this will change the polarity of the microphone capsule, and then the negative voltage will be greater than the positive voltage. Changing the polarity of the microphone capsule in an electret microphone by embedding a positive charge instead of a negative charge in the electret material may also be an option.

[0067] The first nonlinearity of the voltage output V_CA of the capsule cancels out the second nonlinearity of the voltage output V_PA of the preamplifier. Therefore, the distortion effect that provides the second nonlinearity caused by the active element Q1 is more significant for both positive and negative voltages, and whether the preamplifier is designed to provide a more significant distortion effect for positive or negative voltages depends on the polarity of the capsule, since the capsule provides a greater positive voltage than a negative voltage, or vice versa, as stated above.

[0068] According to one aspect, a method for capturing sound in a microphone is disclosed, the method comprising:

[0069] - Receives sound input in the microphone capsule and converts the sound input into an output signal, the output signal including an output voltage V_CA, the output voltage V_CA having a first nonlinearity at least at a sound pressure level (SPL) above a first threshold;

[0070] - The output signal is received from the microphone capsule in the microphone preamplifier and an output voltage V_PA is generated, the output voltage V_PA having a second nonlinearity at least with respect to the first input signal level;

[0071] - This causes the microphone and the preamplifier to produce similar amounts of a first nonlinearity and a second nonlinearity, respectively, wherein the first nonlinearity and the second nonlinearity are out of phase with each other and thus cancel each other out, thereby linearizing the microphone's output signal V_MI.

[0072] The present invention relates to various aspects, including the microphones described above and below, and the corresponding system and device components, all of which produce one or more of the benefits and advantages described in conjunction with the first mentioned aspects, and all of which have one or more embodiments corresponding to the embodiments described in conjunction with the first mentioned aspects and / or disclosed in the appended claims. Attached Figure Description

[0073] The above and other features and advantages will become apparent to those skilled in the art from the following detailed description of exemplary embodiments thereof with reference to the accompanying drawings, in which:

[0074] Figure 1 An exemplary circuit of a microphone is schematically shown.

[0075] Figure 2 The diagram schematically illustrates different currents I. B Exemplary current-voltage I C -V CE Transmission characteristics.

[0076] Figure 3 An exemplary circuit of a microphone is schematically shown.

[0077] Figure 4 An exemplary circuit of a microphone is schematically shown.

[0078] Figure 5 An exemplary circuit of a microphone is schematically shown.

[0079] Figure 6 An exemplary circuit of a microphone is schematically shown.

[0080] Figure 7a and Figure 7b An exemplary curve is schematically shown, illustrating the variation of total harmonic distortion (THD) [%] with sound pressure level [dB SPL].

[0081] Figure 8a , Figure 8b and Figure 8c Exemplary outputs of the preamplifier are schematically shown in two scenarios. Detailed Implementation

[0082] Various embodiments are described below with reference to the accompanying drawings. The same reference numerals refer to the same elements throughout. Therefore, the same elements will not be described in detail with reference to each drawing. It should also be noted that the drawings are intended only to facilitate the description of embodiments. They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. Furthermore, the illustrated embodiments do not need to have all the aspects or advantages shown. Aspects or advantages described in conjunction with specific embodiments are not necessarily limited to that embodiment and may be practiced in any other embodiment even if not so shown or so explicitly described.

[0083] Figure 1An exemplary circuit of a microphone is schematically shown. Microphone 2 is used to capture sound. Microphone 2 includes a microphone head 4 configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least at a sound pressure level (SPL) above a first threshold.

[0084] Microphone 2 includes a preamplifier 6 configured to receive an output signal V_CA from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity at least with respect to the first input signal level.

[0085] Microphone 2 is configured to cause the microphone capsule 4 and preamplifier 6 to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, and the first and second nonlinearities are out of phase with each other, thus canceling each other out, and thereby causing the microphone's output signal V_MI (see...) Figure 4 Linearization.

[0086] Preamplifier 6 can be implemented by an active element Q1, which can be a transistor, such as an NPN bipolar junction transistor (BJT) configured in a common-emitter voltage amplification topology, e.g. Figure 1 As shown.

[0087] Figure 1 Further illustrated, the circuit topology may include a resistor (RC) connected as a load to the positive power supply (Vsupply). Two resistors (RB1 and RB2) are configured to establish a bias voltage at the base of the active element Q1 and as a resistor (RE) acting as local feedback for the active element Q1. Combined with the DC parameters of the active element Q1, resistors RC, RB1, RB2, and RE can establish an operating point (q) for the active element Q1. A microphone capsule 4 can be connected between the base of the active element Q1 and ground, between RB1 and RB2.

[0088] The active element Q1 can be a bipolar junction transistor, such as an NPN BJT, which has several inherent nonlinearities built into its manufacturing process and technology. Relevant to this invention is the ohmic nonlinearity, i.e., the current-voltage relationship I. C -V CE The symmetry varies with different currents I B Changes in transmission characteristics, see Figure 2 .

[0089] Figure 2 The diagram schematically illustrates different currents I. B Exemplary current-voltage I C -V CE Transmission characteristics. As mentioned above, regarding... Figure 1The active element Q1 can be a bipolar junction transistor, such as an NPN BJT, which has several inherent nonlinearities built into its manufacturing process and technology, and relevant to this invention is the ohmic nonlinearity, i.e., the current-voltage I... C -V CE The symmetry varies with different currents I B Changes in transmission characteristics.

[0090] Figure 2 As shown, for the load line (R) L Given an operation point (q) on ), the same positive (i) Bmax ) and negative (i Bmin Changes in base current will not produce equal positive (i) Cmax ) and negative (i Cmin Changes in collector current cause a change across the load line (R) L This produces a distorted output voltage (V_PA).

[0091] Figure 3 An exemplary circuit of a microphone is schematically shown. Microphone 2 is used to capture sound. Microphone 2 includes a microphone head 4 configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least at a sound pressure level (SPL) above a first threshold.

[0092] Microphone 2 includes a preamplifier 6 configured to receive an output signal V_CA from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity at least with respect to the first input signal level.

[0093] Microphone 2 is configured to cause the microphone capsule 4 and preamplifier 6 to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, and the first and second nonlinearities are out of phase with each other, thus canceling each other out, and thereby causing the microphone's output signal V_MI (see...) Figure 4 Linearization.

[0094] exist Figure 3 In the example, microphone capsule 4 is shown as an electret microphone capsule, which can be depicted as having a capacitance (C). MIC The capacitance of the charging capacitor changes as the diaphragm moves due to the sound pressure level (SPL), thus generating a changing voltage V_CA on the SPL.

[0095] An electret microphone can be viewed as a voltage generator connected in series with a capacitor. When the microphone capsule 4 of the electret microphone is connected to the base of the active element Q1 of the preamplifier 6 in a common-emitter voltage amplification topology, the changing voltage output V_CA passes through the resistor R of the preamplifier 6. in Generates a changing current (i)in i in A portion is modulating the base current (I) of the active element Q1, which is related to the changing SPL. b ).

[0096] Figure 4 An exemplary circuit of a microphone is schematically shown. Microphone 2 is used to capture sound. Microphone 2 includes a microphone head 4 configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least at a sound pressure level (SPL) above a first threshold.

[0097] Microphone 2 includes a preamplifier 6 configured to receive an output signal V_CA from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity at least with respect to the first input signal level.

[0098] Microphone 2 is configured to cause the microphone capsule 4 and preamplifier 6 to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, and the first and second nonlinearities are out of phase with each other, thus canceling each other out, and thereby causing the microphone's output signal V_MI (see...) Figure 4 Linearization.

[0099] Microphone capsule 4 can be, for example, an electret microphone capsule, and it has a built-in nonlinearity (nl_CA) in its manufacturing process. This produces a nonlinear output voltage V_CA compared to the sound pressure input. The preamplifier 6 also has a built-in nonlinearity (nl_PA) through its topology.

[0100] Figure 4 A system with nonlinearity and feedback is shown. The nonlinear performance of the microphone capsule 4 is out of phase with the nonlinear performance of the preamplifier 6 in the system.

[0101] By selecting the DC operating point (q) of the active element Q1 (given by its transfer characteristics), the load line (R) is selected. L The local feedback (K) causes equal nonlinearity (nl_PA) in the preamplifier 6, but is in opposite phase with the nonlinearity (nl_CA) in the microphone capsule 4, which will lead to the elimination of nonlinearity, resulting in a very low total harmonic distortion (THD) value in the system output (V_MI) until the clipping point of the system.

[0102] In addition, such as Figure 4 As shown, the loop gain T = A * K * nl_PA, where A is the gain or amplification of the active element Q1, and K is the local feedback.

[0103] Therefore, the voltage output V_PA of preamplifier 6 is the voltage output V_CA of the attack phase multiplied by the loop gain T, that is, V_PA = V_CA * T.

[0104] Figure 5 An exemplary circuit of a microphone is schematically shown. Microphone 2 is used to capture sound. Microphone 2 includes a microphone head 4 configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least at a sound pressure level (SPL) above a first threshold.

[0105] Microphone 2 includes a preamplifier 6 configured to receive an output signal V_CA from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity at least with respect to the first input signal level.

[0106] Microphone 2 is configured to cause the microphone capsule 4 and preamplifier 6 to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, and the first and second nonlinearities are out of phase with each other, thus canceling each other out, and thereby causing the microphone's output signal V_MI (see...) Figure 4 Linearization.

[0107] exist Figure 5 In the diagram, microphone capsule 4 is exemplified as a condenser microphone for capturing sound. Preamplifier 6 can be implemented by an active element Q1, which can be a transistor, such as an NPN bipolar junction transistor (NPN-BJT) configured with a common-emitter voltage amplification topology.

[0108] Figure 5 Furthermore, the circuit topology may include a resistor (RC) connected to the positive power supply (Vsupply). Two resistors (RB1 and RB2) are configured to establish a bias voltage at the base of the active element Q1 and as a resistor (RE) acting as local feedback for the active element Q1. Combined with the DC parameters of the active element Q1, resistors RC, RB1, RB2, and RE can establish the operating point (q) for the active element Q1. The microphone capsule 4 can be connected between the base of the active element Q1 and ground between RB1 and RB2.

[0109] In addition, an output capacitor Cout is connected between the active element Q1 and the resistor (RC), and a resistive load RL is connected before the output.

[0110] In Figure 5 The documentation also includes exemplary types (such as active component Q1 being a 1N4401 type) and exemplary values ​​for different components, such as voltage source Vsupp being 15V and output capacitor Cout being 50U.

[0111] Figure 6 An exemplary circuit of a microphone is schematically shown. Microphone 2 is used to capture sound. Microphone 2 includes a microphone head 4 configured to receive sound input and convert the sound input into an output signal. The output signal includes an output voltage V_CA. The output voltage V_CA has a first nonlinearity at least at a sound pressure level (SPL) above a first threshold.

[0112] Microphone 2 includes a preamplifier 6 configured to receive an output signal V_CA from the microphone capsule and generate an output voltage V_PA. The output voltage V_PA has a second nonlinearity at least with respect to the first input signal level.

[0113] Microphone 2 is configured to cause the microphone capsule 4 and preamplifier 6 to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, and the first and second nonlinearities are out of phase with each other, thus canceling each other out, and thereby causing the microphone's output signal V_MI (see...) Figure 4 Linearization.

[0114] exist Figure 6 In the diagram, microphone capsule 4 is exemplified as a condenser microphone for capturing sound. Preamplifier 6 can be implemented by an active element Q1, which can be a transistor, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) configured with a common-emitter voltage amplification topology.

[0115] Figure 6 Furthermore, the circuit topology may include a resistor (Rdrain) connected as a load RL to the positive power supply (Vsupply). Two resistors (Rgate1 and Rgate2) are configured to establish a bias voltage at the base of the active element Q1 and as a local feedback resistor (Rsource) for the active element Q1. Combined with the DC parameters of the active element Q1, resistors Rdrain, Rgate1, Rgate2, and Rsource can establish the operating point (q) for the active element Q1. A microphone capsule 4 can be connected between the base of the active element Q1 and ground between Rgate1 and Rgate2.

[0116] Figure 7a and Figure 7b An exemplary curve is schematically shown, illustrating the variation of total harmonic distortion (THD) [%] with sound pressure level [dB SPL]. The sound pressure level range in the figure is from 110 dB SPL to 145 dB SPL.

[0117] The curves show that the THD performance of a microphone varies greatly depending on the electrical properties of the preamplifier. Total Harmonic Distortion (THD) is a measure of the distortion that produces harmonic components (integer multiples of the fundamental frequency) in a nonlinear system. THD is usually expressed as a percentage of the fundamental frequency. THD is a measure of signal purity and is also the percentage of unwanted distortion in a signal.

[0118] Figure 7a The THD performance of the preamplifier electronics is shown, without considering the nonlinearity introduced by the attack capsule. The dark curves represent the prior art. The light curves represent the present invention. From Figure 7a As can be seen, the preamplifier electronics of the prior art are extremely linear (dark curve). This contrasts with the present invention, in which the new preamplifier electronics are nonlinear (light curve).

[0119] exist Figure 7a In the study, the results showed that THD ranged from 0.001% to 30%, and... Figure 7b In the figure, the THR results are shown to be 0.1% to 30%. The difference in dynamic range in the figure is due to the extreme linearity of the preamplifier used in the prior art.

[0120] Figure 7b The diagram illustrates the THD performance when the preamplifier electronics and microphone are connected together. The dark curve represents the prior art. The light curve represents the present invention. Figure 7b As shown, for an SPL of up to approximately 136 dB SPL, the new preamplifier electronics and capsule have lower THD than existing technologies, which is an advantage.

[0121] Figure 8a , Figure 8b and Figure 8c Exemplary outputs of the preamplifier are schematically shown in two scenarios. The simulation was performed using a 500 Hz pure tone. The sound pressure level was 133 dB SPL. The signal-to-noise ratio (SNR) was 40 dB.

[0122] Figure 8a The input signal [V] is shown as a function of time [ms]. The dark curve represents a linear input. The light curve represents a nonlinear input. It can be seen that at higher sound pressure levels (e.g., 133 dB SPL here), the electric field inside the capsule does not remain approximately constant. This means the diaphragm begins to move asymmetrically and produces larger oscillations, which become more pronounced as the diaphragm moves toward the back electrode, resulting in a positive output voltage greater than a negative one.

[0123] Figure 8b and Figure 8c The amplitude spectrum [dB] is shown as a function of frequency [Hz].

[0124] Figure 8b As shown, for a linear input (i.e., without a nonlinear advance diaphragm), when the input signal of the preamplifier (light dashed line) is completely linear (i.e. without higher harmonics), the preamplifier circuitry produces distortion at the output (dark solid line) in the form of higher harmonics, which in this case is mainly second harmonics, see 1 kHz.

[0125] Figure 8c As shown, for a nonlinear input (i.e., a diaphragm with a nonlinear advance), when the input signal (light dashed line) already contains nonlinearity (i.e., higher harmonics), for example, due to the asymmetrical movement of the diaphragm from the advance at high sound pressure levels, the circuitry of the preamplifier is canceling out these nonlinearities and thus providing a linearized output signal (dark solid line).

[0126] Note that due to noise, the minimum achievable THD in this simulation is 0.1%.

[0127] Although specific features have been shown and described, it should be understood that they are not intended to limit the claimed invention, and it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the claimed invention. Therefore, the specification and drawings should be considered in an illustrative rather than restrictive sense. The claimed invention is intended to cover all alternatives, modifications, and equivalents.

[0128] project:

[0129] 1. A microphone for capturing sound, the microphone comprising:

[0130] - A microphone, configured to receive sound input and convert the sound input into an output signal, the output signal including an output voltage V_CA, the output voltage V_CA having a first nonlinearity at least at a sound pressure level (SPL) above a first threshold;

[0131] - A preamplifier configured to receive an output signal from a dial and generate an output voltage V_PA, the output voltage V_PA having a second nonlinearity at least with respect to a first input signal level;

[0132] The microphone is configured to cause the microphone capsule and the preamplifier to generate similar amounts of a first nonlinearity and a second nonlinearity, respectively, wherein the first nonlinearity and the second nonlinearity are out of phase with each other and thus cancel each other out, thereby linearizing the microphone's output signal V_MI.

[0133] 2. The microphone according to any of the preceding projects, wherein the nonlinear cancellation effect between the microphone capsule and the preamplifier is related to a sound pressure level (SPL) above a first threshold, wherein the first threshold is a high SPL, and wherein the SPL is between 110 dB SPL and 160 dB SPL.

[0134] 3. The microphone according to any of the preceding items, wherein the first input signal level includes an input signal with an amplitude higher than the second threshold.

[0135] 4. The microphone according to any of the preceding items, wherein the microphone is a condenser microphone or an electret microphone and the microphone capsule includes a diaphragm and a back electrode, or wherein the microphone is a dynamic microphone and the microphone capsule includes a diaphragm and a magnet.

[0136] 5. A microphone according to any of the preceding items, wherein the microphone is connected to a power source, and wherein the power source is connected to a resistive load (RL).

[0137] 6. The microphone according to any of the foregoing items, wherein the preamplifier includes an active element Q1, wherein the active element Q1 is a transistor, and wherein the transistor is a junction field-effect transistor (JFET), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a bipolar junction transistor (BJT), such as an NPN BJT.

[0138] 7. The microphone according to any of the preceding items, wherein the preamplifier includes a bias circuit and a feedback circuit coupled to the active element Q1.

[0139] 8. A microphone according to any of the preceding items, wherein the bias circuit is coupled between the microphone capsule and the active element Q1 of the preamplifier.

[0140] 9. A microphone according to any of the preceding items, wherein the bias circuit and feedback circuit of the preamplifier are adjusted to counteract the first nonlinearity of the attack.

[0141] 10. A microphone according to any of the preceding items, wherein a resistive load (RL) is coupled to a preamplifier, and wherein a resistive load (FL) is coupled to an active element Q1 of the preamplifier.

[0142] 11. The microphone according to any of the preceding items, wherein a resistive load (RL) is coupled to a preamplifier via a feedback loop, the feedback loop including the feedback circuit of the preamplifier.

[0143] 12. A microphone according to any of the preceding items, wherein the active element Q1 of the preamplifier is connected to a resistor RC, wherein the resistor RC is connected to a positive power supply (Vsupp), and wherein resistors RB1 and RB2 of the preamplifier are configured to establish a bias voltage at the base of the active element Q1 and a resistor RE acting as local feedback for the active element Q1.

[0144] 13. The microphone according to any of the preceding items, wherein the active element Q1 is configured to generate a distortion effect of the output voltage V_PA of the preamplifier, thereby providing a second nonlinearity.

[0145] 14. A microphone according to any of the preceding items, wherein the distortion effect caused by the active element Q1 causes the output voltage V_PA of the preamplifier to differ from the output voltage without the distortion effect, and wherein the distortion effect is more significant for positive or negative voltages, thereby providing a second nonlinearity.

[0146] 15. A microphone according to any of the preceding items, wherein the active element Q1 causes the preamplifier to provide a second nonlinearity due to a certain amount of distortion introduced by the resistive load (RL).

[0147] 16. A microphone according to any of the preceding items, wherein the output voltage V_CA provided by the microphone capsule has a positive voltage greater than a negative voltage, or vice versa, thereby providing a first nonlinearity.

[0148] List of reference numerals

[0149] 2 microphones

[0150] 4. Attack

[0151] 6. Preamplifier

[0152] V_CA output voltage signal of the tone capsule

[0153] V_PA preamplifier output voltage signal

[0154] V_MI microphone voltage output signal

[0155] SPL sound pressure level

[0156] RL resistive load

[0157] JFET (Junction Field-Effect Transistor)

[0158] MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)

[0159] BJT (Bipolar Junction Transistor)

[0160] Q1 Active components

[0161] RC resistor

[0162] V supply power supply

[0163] RB1 resistor

[0164] RB2 resistor

[0165] RE resistor

[0166] Cmic condenser microphone capsule

[0167] nonlinearity of nl_CA attack

[0168] Nonlinearity of nl_PA preamplifier

[0169] T-loop gain

[0170] A. Gain / Magnification

[0171] K Local Feedback

[0172] Cout Output capacitor

[0173] Rgate1 resistor

[0174] Rgate2 resistor

[0175] Rdrain resistor

[0176] Rsource resistor

[0177] THD (Total Harmonic Distortion)

Claims

1. A microphone for capturing sound, the microphone comprising: - A microphone, configured to receive sound input and convert the sound input into an output signal, the output signal including an output voltage V_CA, the output voltage V_CA having a first nonlinearity at least at a sound pressure level (SPL) above a first threshold; - A preamplifier configured to receive the output signal from the dial and generate an output voltage V_PA, the output voltage V_PA having a second nonlinearity at least with respect to a first input signal level; The microphone is configured to cause the microphone capsule and the preamplifier to generate similar amounts of the first nonlinearity and the second nonlinearity, respectively, wherein the first nonlinearity and the second nonlinearity are out of phase with each other and thus cancel each other out, thereby linearizing the microphone's output signal V_MI.

2. The microphone according to any one of the preceding claims, wherein, The nonlinear cancellation effect between the microphone and the preamplifier is related to a sound pressure level (SPL) above a first threshold, wherein the first threshold is a high SPL, and wherein the SPL is between 110 dB SPL and 160 dB SPL.

3. The microphone according to any one of the preceding claims, wherein, The first input signal level includes input signals with an amplitude higher than the second threshold.

4. The microphone according to any one of the preceding claims, wherein, The microphone is a condenser microphone or an electret microphone, and the microphone capsule includes a diaphragm and a back electrode, or the microphone is a dynamic microphone, and the microphone capsule includes a diaphragm and a magnet.

5. The microphone according to any one of the preceding claims, wherein, The microphone is connected to a power source, and the power source is connected to a resistive load (RL).

6. The microphone according to any one of the preceding claims, wherein, The preamplifier includes an active element Q1, wherein the active element Q1 is a transistor, and wherein the transistor is a junction field-effect transistor (JFET), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a bipolar junction transistor (BJT), such as an NPN BJT.

7. The microphone according to any one of the preceding claims, wherein, The preamplifier includes a bias circuit and a feedback circuit coupled to the active element Q1.

8. The microphone according to any one of the preceding claims, wherein, The bias circuit is coupled between the dial and the active element Q1 of the preamplifier.

9. The microphone according to any one of the preceding claims, wherein, The bias circuit and the feedback circuit of the preamplifier are adjusted to counteract the first nonlinearity of the attack.

10. The microphone according to any one of the preceding claims, wherein, The resistive load (RL) is coupled to the preamplifier, and the resistive load (FL) is coupled to the active element Q1 of the preamplifier.

11. The microphone according to any one of the preceding claims, wherein, The resistive load (RL) is coupled to the preamplifier via a feedback loop, the feedback loop including the feedback circuit of the preamplifier.

12. The microphone according to any one of the preceding claims, wherein, The active element Q1 of the preamplifier is connected to a resistor RC, wherein the resistor RC is connected to a positive power supply (Vsupp), and wherein resistors RB1 and RB2 of the preamplifier are configured to establish a bias voltage at the base of the active element Q1 and at the resistor RE which acts as local feedback for the active element Q1.

13. The microphone according to any one of the preceding claims, wherein, The active element Q1 is configured to generate a distortion effect on the output voltage V_PA of the preamplifier, thereby providing the second nonlinearity, and / or wherein, The distortion effect caused by the active element Q1 makes the output voltage V_PA of the preamplifier different from the output voltage without the distortion effect, and wherein the distortion effect is more significant for positive or negative voltages, thereby providing the second nonlinearity.

14. The microphone according to any one of the preceding claims, wherein, The active element Q1 causes the preamplifier to provide the second nonlinearity due to a certain amount of distortion introduced by the resistive load (RL).

15. The microphone according to any one of the preceding claims, wherein, The output voltage V_CA provided by the tone capsule has a positive voltage that is greater than a negative voltage, or vice versa, thereby providing the first nonlinearity.

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