Patent Publication Number: US-8995672-B2

Title: System and method for microphone polarity detection

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure is generally directed at microphones and more specifically is directed at a method and system for microphone polarity detection. 
     BACKGROUND OF THE DISCLOSURE 
     Portable electronic device use has continued to increase over the years with new applications and functionality continually being incorporated within these devices. The introduction of these new applications and functionality require the devices themselves to be updated in order to handle new requirements associated with these applications and functionality. 
     In some portable electronic devices, a headset with a microphone is used to fully enhance the usability of these applications or functionality. In order to connect the headset with the device, the headset is typically connected via the insertion of a jack into a device port. 
    
    
     
       BRIEF DESCRIPTION OF THE DETAILED DRAWINGS 
       Embodiments of the present disclosure will now be described, by way of example only, with reference to the attached Figures, wherein: 
         FIG. 1  is a schematic diagram of a portable electronic device; 
         FIG. 2  is a more detailed schematic view of the portable electronic device; 
         FIG. 3  is a schematic diagram of a system for polarity detection of a microphone within a headset; 
         FIG. 4  is a schematic diagram of one embodiment of polarity detection; 
         FIG. 5  is a schematic diagram of another embodiment of polarity detection; 
         FIG. 6  is a flowchart outlining one method of detecting microphone polarity in a headset; 
         FIG. 7  is a schematic diagram of another embodiment of a system for polarity detection of a microphone within a headset; 
         FIG. 8  is a schematic diagram of an embodiment of polarity detection; 
         FIG. 9  is a schematic diagram of another embodiment of polarity detection; and 
         FIG. 10  is a flowchart outlining a second method of detecting microphone polarity. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following disclosure presents apparatus and techniques for handling polarity detection in microphones, typically within headsets for use with portable electronic devices. 
     Currently, portable electronic devices are designed to receive headsets that are designed to be compatible with the device in that the polarity of the microphone is known. Therefore, users are restricted to using headsets that are designed for a specific portable electronic device and the electronic device is unable to interact with other headsets. Therefore, headsets which are not implemented with the polarity that is being expected by the device may not be operational with the device. 
     By being able to determine the polarity of a microphone within a headset, portable electronic devices may be able to interact with any headset and is not limited to use with headsets which are specifically designed for the device. 
     Turning to  FIG. 1 , a schematic diagram of a portable electronic device, illustrated as a mobile communication device, is shown. The mobile communication device  10  has a body  12  which includes a display screen  14 , a keyboard/keypad  16 , a set of buttons  18  and a user-operated pointing or input device  20 , such as a trackpad or a trackball. The user-operated pointing or input device may also be a joystick, scroll wheel, roller wheel, mouse or touchpad or the like, or another button. The mobile communication device  10  also includes at least one port for receiving a jack, but this is not shown in  FIG. 1 . The device  10  further includes other parts which are not shown or described. The device may be sized to be held or carried in the human hand. 
     Turning to  FIG. 2 , the mobile communication device  10  further includes a controller, or processor,  30  which is connected to a chip  32  which is integrated within the communication device  10 . A signal generator, such as a voltage source,  33  is also connected to the chip  32 . The chip  32  includes a switch matrix and jack configuration detect portion  34  which is integrated with a port  36  for receiving a jack  38  associated with a cable  40 , such as a microphone/headset cable. The switch matrix  34  includes a plurality of individual input and output ports  42  for receiving and transmitting signals with corresponding wires  44  connected within the jack  38 . The pin port PIN 5  input detects the insertion of the cable by the opening or closing of a mechanical switch, when the plug or jack  38  is inserted. If pin port PIN 5  is broken or absent, it is possible to detect the insertion of the cable by detecting a capacitance of the cable itself. As will also be discussed below, one or more contacts (such as pin port and a signal line) can be connected. In this context, “connected” refers not necessarily to physical contact or proximity—although the contacts may be physically close to or touching one another—but to the electrical connection whereby a signal in one contact results in a signal in the other. Such electrical connection may be completed or broken by affecting a current path (e.g., with the switch matrix  34 ) rather than by changing the physical relationship of one contact to another. 
     The wires or lines  44  within the jack  38  represent signal lines, such as audio lines, with one wire  44   a  representing a right audio or headphone line, one wire  44   b  representing a left audio or headphone line and then a pair of lines  44   c  and  44   d  providing a ground line and a microphone line. In an alternative embodiment, the jack may include only one audio line. In one embodiment, the ground line may be provided on the line  44   c  which is connected to pin port PIN 3  and the microphone line provided on line  44   d  which is connected to port pin PIN 4 . The ground line is also connected to a ground reference voltage. In this context, ground is not necessarily earth potential, and a “ground line” need not be electrically connected to the Earth. Rather, ground basically connotes a node that is maintained at a reference voltage that is substantially constant with respect to other voltages. 
     In one embodiment of microphone polarity detection, the detection is achieved by sending out a detection signal, such as a AC or a DC signal, on the microphone line or on the ground line and receiving a return signal on one of the audio headphone lines. In another embodiment, the detection signal may be transmitted over an audio line and then the return signal sensed over either the ground line or the microphone line. 
     If the detection signal is being transmitted over one of the ground or microphone line, while the detection signal is being transmitted, the other of the ground or microphone line is kept at a different potential and the sensing of the return signal is on an audio line. In other words. if the detection signal is transmitted on the ground line, the microphone line is held at a potential different than the detection signal and a return signal can be sensed on at least one of the audio lines. If the detection signal is transmitted on the microphone line, the ground line is kept at a different potential, typically no return signal will be sensed on either of the audio lines. Similarly, if a detection signal is transmitted on an audio line, while the microphone line is kept at a steady potential, a return signal, or pulse can be sensed on the ground line. However, if the detection signal is transmitted over an audio line, and the ground line is grounded, no return signal will be sensed on the microphone line. This will described in more detail below. 
     Turning to  FIG. 3 , a more detailed schematic diagram of a system for polarity detection of a microphone  300  within a headset is shown. As shown, the four wires, or lines  44   a  to  44   d  of the jack are connected to the ports  42  of the switch matrix  34 . The audio lines  44   a  and  44   b  are also connected to individual headphones  310  within the headset. Although shown with two headphones, the headset may include only one headphone. For the below description, where there is discussion of two headphones and therefore, two audio lines, the signals may be transmitted or sensed over a single audio line without affecting the apparatus or method of polarity detection. In other words, the headset may include only one headphone and one audio line but method of polarity detection may still be executed. Also, for headsets which include two headphones and two audio lines, the method of polarity detection may be executed using only one of the two headphones. 
     In the current embodiment, associated with each of the ports  42  connected to the audio lines  44   a  and  44   b , are detectors  54  which are communicatively connected to the output of the lines  44   a  and  44   b  to monitor return signals being transmitted over the wires in response to one or more detection signals being transmitted over the one of the microphone line  44   d  or ground line  44   c  (as will be discussed in further detail below). In one embodiment, the detector  54  may be implemented as a low pass filter and a rectifier. In another embodiment, the detector is a pre-amplifier followed by a threshold detector. In another embodiment, the detector is a demodulator followed by a lowpass filter and a threshold detector. In another embodiment, the detector is a threshold detector. In one embodiment, the threshold detector can be implemented using a fixed threshold comparator. In another embodiment, the threshold detector can be implemented via an analog-to-digital converter (ADC) and a fixed digital threshold. 
     The detectors may be discrete components within the portable electronic device but in other embodiments, they are implemented on the chip  32 . Each detector  54  is connected to a state machine  56 , which may be located on the chip  32  or within the processor  30 , to transmit signals representing the return signals or measurements recorded by the detectors  54 . The state machine  56  processes or transmits the results of the sensed return signal or transmits results based on the signals sensed by its associated detector  54  to the processor  30  so that the processor may determine the polarity of the microphone  300 . In general, the state machine  56  is a deciding circuit, which receives inputs from its associated detector  54 , decides what condition or conditions are indicated by those inputs (such as whether a particular state is present or absent), then transmits a signal to the processor  30  as a function of that decision. 
     As shown in  FIG. 4 , an example of polarity detection is shown. In this embodiment, the detection signal is transmitted over the microphone line  44   d  (or the line connected to pin port PIN 4 ) and the return signal is sensed on the one or both of the headphone or audio lines  44   a  or  44   b.    
     The detection signal, schematically represented by U 1  is either an AC signal or a DC signal while the ground line  44   c  is maintained at a different potential, schematically represented by U 2  where U 2  does not equal U 1 . 
     After the transmission of the detection signal over the microphone line, the return signal may be sensed by one of the detectors  54  connected to at least one of the audio lines  44   a  or  44   b . As disclosed above, in one embodiment, the detector  54  is integrated as part of the switch matrix  34 , or the chip  32 , but in another embodiment, may be located, or integrated within the headset. If the detector  54  is or detectors  54  are located within the headset, the headset communicates with the processor  30  to provide information concerning the return signal or signal(s) which are sensed. 
     As shown in  FIG. 5 , another example of polarity detection is shown. In this embodiment, the detection signal is transmitted over the ground line  44   c  (or the line connected to pin port PIN 3 ) and the return signal sensed over at least one of the audio lines  44   a  or  44   b.    
     The detection signal, schematically represented by U 1  is either an AC signal or a DC signal while the microphone line  44   d  is maintained at a different potential, schematically represented by U 2  where U 2  does not equal U 1 . After the transmission of the detection signal over the microphone line, the return signal may be sensed by one of the detectors  54  connected to at least one of the audio lines  44   a  or  44   b.    
     Turning to  FIG. 6 , a flowchart outlining a first method of microphone polarity detection is shown. In operation, from the cable point of view, voice signals are typically transmitted over the microphone line. However, when a jack is inserted into the port of the portable electronic device, it is not always known to which pin port, the microphone line is connected (from the portable electronic device point of view). The microphone line may be connected to either pin port PIN 3  or pin port PIN 4 . This may be problematic since signals can not be transmitted over the ground line and therefore a determination is required to see over which pin port the audio signals are to be transmitted, or, in other words, the pin port which is connected to the microphone line. In the example below, the portable electronic initially assumes that the microphone line  44   d  is connected to pin port PIN 4  and the ground line  44   c  is connected to pin port PIN 3 . However, depending on the results of the polarity detection, the opposite conclusion may be determined. 
     When the jack is inserted into the port, there is a line within the jack that corresponds with each of the pin ports  42  in the switch matrix  34 . Typically, pin port PIN 1  and pin port PIN 2  receive the audio lines  44   a  and  44   b  which are characterized as Left audio and Right audio while pin port PIN 5  is used for detecting the presence of the jack. With respect to pin ports PIN 3  and PIN 4 , one of these pin ports is connected to the ground line while the other is connected to the microphone line. 
     In one embodiment, the method is initiated once the insertion of the jack of the headset cable into the port is sensed  100  whereby the individual lines  44  are connected to associated pin ports. In one embodiment, this is achieved by detecting the presence of the jack  38  on pin port PIN 5  of the switch matrix and jack configuration detect portion  34 . Alternatively, internal device logic may assist in determining or may determine when the jack is inserted based on the capacitance of the cable itself or by the coupling between some of the lines  44 . In this configuration, it is possible to detect the insertion of the headset, even if the pin port PIN 5  is non-functional or not existent. 
     After the presence of the jack is sensed  100 , a detection signal, either AC or DC, is transmitted  104  over one of pin port PIN 3  or pin port PIN 4 . In accordance with various embodiments, the AC or DC signal is generated and transmitted by the signal generator  33 . The detection signal is then propagated through the cable  40 . The detection signal may be a sine wave or a square wave although other signals are contemplated. While the detection signal is transmitted over one of the lines connected to pin port PIN 3  or pin port PIN 4 , the other of the lines is connected to a known potential, such as a ground potential or ground reference voltage 
     The transmission of the detection signal may result in activity on the audio lines  44   a  and  44   b  in response to the signal, which is measured as a return signal or a measured output voltage. The return signal or signals transmitted over the audio lines (lines  44   a  and  44   b ) are then sensed  106  or read over pin port PIN 1  and/or pin port PIN 2  by the associated detectors  54 . In one embodiment, the audio lines  44   a  and  44   b  are kept in a high impedance (tri-state) mode when the return signal is sensed in order to minimally affect the measurement. In order for the signal to minimally disturb the user of the headset, a detection signal of low amplitude or signals that are outside the audible bandwidth may be used. 
     From these return signals, or measurements, the polarity of the microphone or headset may be determined. In order to determine if the signal has been transmitted over the ground line (from the portable electronic device point of view), a check is performed to determine if a particular return signal is sensed, or measured,  108  on one of the audio lines. If a particular return signal is sensed, it can be concluded  110  that a headset, or headphone and microphone combination, has been connected to the switch matrix  34 . In this embodiment, the particular return signal may be a signal which substantially corresponds to, substantially matches or is comparable in magnitude with the detection signal or a signal which is above a threshold with respect to the detection signal. 
     The polarity of the microphone can then be determined. As signals have a very good coupling to the audio lines through the ground line and the headphones themselves, if the particular return signal is sensed on one of the audio lines, it can be determined  111  that the line over which the detection signal was transmitted is the ground line. This determination may be achieved with the assistance of the state machines. In one embodiment of the state machine, if the return signals from both detectors  54  are above a certain threshold (with reference to the transmitted sensed signal), the state machine receives these signals and transmits a signal to the processor indicating if a condition was met, such as, but not limited to, if the particular return signal was sensed on an audio line. Alternatively, the state machine may transmit a signal indicating which of lines  44   c  or  44   d  is the ground line by confirming that the particular return signal was sensed. The state machine may also directly configure the switch matrix  34  to identify the ground and microphone lines without intervention from the processor. In other words, it may be determined that the output of the state machine corresponds to a 1 and therefore, it may be concluded that the detection signal was transmitted over the microphone line. Alternatively, it may be determined that the output of the state machine corresponds to a 0 and therefore, it may be concluded that the detection signal was transmitted over the microphone line. 
     The processor may then receive the status of the pin selection, or information concerning which pin port is connected to which line, by an interrupt or logic pin signaling an event or the processor can poll the electronic device or the chip  32  to ask for status, such as, but not limited to the status of the lines. In either case, the determination of the ground line (and therefore the microphone line) can either be made automatically by the state machine or by the processor if the particular return signal is sensed. 
     The polarity of the microphone the headset may then be stored in the processor, or other components, or the switch matrix automatically configured for correct ground connection, so that the signals from the device may be corrected transmitted to the headset. 
     Alternatively, if the particular return signal is not sensed, or measured, at  108 , another detection, or a second detection, signal is then transmitted  112  over the other of the line between pin ports PIN 3  and PIN 4 . The line over which the detection signal is not transmitted is set to a known potential, such as a ground potential by connecting the line to a ground reference voltage. Once again, the output of at least one of the audio lines is sensed  114  to determine if a particular return signal is sensed. A check is then performed to determine  116  if the particular return signal is sensed such that the output of the at least one audio line substantially corresponds with the detection signal. If the particular return signal is sensed, it can be determined  110  that a headset, or headphone and microphone combination, has been connected to the switch matrix  34  or device. The polarity of the microphone can then be determined  111  as discussed above. The polarity of the microphone within the headset is then stored in the processor, or other components, or the switch matrix is automatically configured for correct ground connection, so that the signals from the device may be corrected transmitted to the headset. 
     If the particular return signal is not sensed in any of the cases, it can be concluded  118  that no headset is connected. In this case, the cable that has been inserted into the jack may be, but is not limited to, a microphone without a headset, or a microphone extension cable. 
     Turning to  FIG. 7 , a more detailed schematic diagram of another embodiment of apparatus for the polarity detection of a microphone  300  within a headset is shown. As shown, the four wires, or lines  44   a  to  44   d  are connected to the ports  42  of the switch matrix  34 . The audio lines  44   a  and  44   b  are connected to individual headphones  310 . As with the previous embodiment, there may be only one headphone and therefore only one audio line. In the current embodiment, associated with each of the ports  42  connected to the microphone line  44   d  and the ground line  44   c  are detectors  54  which are communicatively connected to the output of the lines  44   c  and  44   d  to monitor return signals being transmitted over the wires in response to one or more detection signals transmitted over one of audio lines  44   a  or  44   b  (as will be discussed in further detail below). Each of the detectors  54  may be implemented in any of the manners discussed or via any detection circuitry or components. The detectors can be discrete components within the portable electronic device but may also be implemented on the chip  32 . Each detector  54  is connected to a state machine  56 , which may also be located on the chip  32  or within the processor  30 , to transmit signals representing the sensed return signals, or measurements recorded by the detectors  54 . The state machine  56  transmits signals representing the conditions met by the return signal sensing by its associated detector  54  to the processor  30  so that the processor can determine the polarity of the microphone  300 . Alternatively, the state machine may transmit a signal indicating which of the microphone line and the ground line (from the point of view of the portable electronic device) is the actual ground line or the actual microphone line. 
     As shown in  FIG. 8 , an example of polarity detection is shown. In this embodiment, the detection signal is transmitted over one of the audio lines, such as the left audio line  44   a  and the return signal is sensed on the microphone line  44   d  (from the point of view of the portable electronic device). 
     The detection signal, schematically represented by U 1  is either an AC signal or a DC signal while the other audio line  44   b  is maintained at a different potential or tri-stated, schematically represented by U 2 . The ground line  44   c  (or the line that is not being sensed for the particular return signal), is driven to a known potential, schematically represented by U 3 , such as a ground potential. 
     After the transmission of the detection signal over the left audio line, the particular return signal may be sensed by the detectors  54  connected to the microphone line to assist in determining the polarity of the microphone  300  within the headset. In another embodiment, the detection signal may be transmitted over the right audio line  44   b  with the potential of the left audio line  44   a  held at the same potential level or tri-stated. 
     As shown in  FIG. 9 , another example of polarity detection is shown. In this embodiment, the detection signal is transmitted over one of the audio lines, such as the left audio line  44   a , and the return signal sensed on the ground line  44   c  (from the point of view of the portable electronic device). 
     The detection signal, schematically represented by U 1  is either an AC signal or a DC signal while the other audio line  44   b  is maintained at a different potential or tri-stated, schematically represented by U 2 . The microphone line  44   d  (or the line that is not being sensed for the particular return signal), is driven to a known potential, schematically represented by U 3 , such as a ground potential. 
     After the transmission of the detection signal over the audio line, the particular return signal may be sensed by the detector  54  connected to the ground line to assist in determining the polarity of the microphone  300  within the headset. In another embodiment, the detection signal may be transmitted over the right audio line  44   b.    
     Turning to  FIG. 10 , a flowchart outlining another method of microphone polarity detection is shown. In operation, from the cable point of view, voice signals are typically transmitted over the microphone line. However, when a jack is inserted into the port of the portable electronic device, it is not always known to which PIN port, the microphone line is connected (from the portable electronic device point of view). The microphone line may be connected to either pin port PIN 3  or pin port PIN 4 . This may be problematic since signals can not be transmitted over the ground line and therefore a determination is required to see over which pin port the audio signals are to be transmitted, or, in other words, the pin port which is connected to the microphone line. In the example below, the portable electronic initially assumes that the microphone line  44   d  is connected to pin port PIN 4  and the ground line  44   c  is connected to pin port PIN 3 . However, depending on the results of the polarity detection, the opposite conclusion may be determined. 
     In one embodiment, when the jack is inserted into the port, there is a line within the jack that corresponds with each of the pin ports  42  in the switch matrix  34 . However, there may be embodiments where the headset includes only one headphone and therefore, one of pin port PIN 1  or pin port PIN 2  may not be used. Typically, pin port PIN 1  and pin port PIN 2  receive the audio lines  44   a  and  44   b  which are characterized as audio lines while pin port PIN 5  is used for detecting the presence of the jack. With respect to pin ports PIN 3  and PIN 4 , one of these pin ports is connected to the ground line while the other is connected to the microphone line. 
     In one embodiment, the method is initiated once the insertion of the jack of the headset cable into the port is sensed  200  whereby the individual lines  44  are connected to associated pin ports. Some methods of sensing of the presence of the jack are discussed above. 
     After the presence of the jack is sensed  200 , a detection signal, either AC or DC, is transmitted  204  over one of the audio lines pin port PIN 3  or pin port PIN 4 . In one embodiment, the AC or DC signal is generated and transmitted by the signal generator  33 . The detection signal is then propagated through the cable  40 . The detection signal may be a sine wave or a square wave although other signals are contemplated. 
     The transmission of the detection signal may result in activity, in the form of a return signal on microphone line  44   d  or the ground line  44   c  in response to the detection signal, which is measured as a return signal, or measured output voltage. In one embodiment, while the ground line (or line connected to pin point PIN 3 ) is held at a known potential, such as a ground potential, the return signal transmitted over the microphone line is sensed  206  or read over pin port PIN 4  by the associated detector  54 . The microphone line  44   d  is kept in a high impedance (tri-state) mode when the measurements are taken in order to minimally affect the measurement. 
     From these return signals, or measurements, the polarity of the microphone or headset can be determined. In order to determine which line the detection signal has been transmitted over, a check is performed to determine if a particular return signal is sensed  208  on the microphone line  44   d  (or the line connected to pin port PIN 4 ). If a particular return signal is sensed, it can be concluded  210  that a headset, or headphone and microphone combination, has been connected to the switch matrix  34 . In this embodiment, the particular return signal may be a signal which substantially corresponds to, substantially matches or is comparable in magnitude with the detection signal or above a threshold with respect to the detection signal. 
     If the particular return signal is sensed on the microphone line  44   d , it can be determined  211  that this line is in fact the ground line and the ground line (from the initial assumption of the portable electronic device) is the microphone line. As discussed above, this determination may also be performed with the state machine  56 . The polarity of the microphone within the headset is then stored in the processor, or other components, or the switch matrix is automatically configured for correct ground connection, so that the signals from the device may be corrected transmitted to the headset. 
     Alternatively, if the particular return signal is not sensed at  208 , another detection, or a second detection signal is then transmitted  212  over one of the audio lines  44   a  or  44   b . The output of the ground line (from the viewpoint of the portable electronic device) or the line connected to pin port PIN 3 , is then sensed  214 . A check is then performed to determine  216  if the particular return signal is sensed on the ground line. If the particular return signal is sensed, it can be concluded  210  that a headset, or headphone and microphone combination, has been connected to the switch matrix  34 . The polarity of the microphone can then be determined  211  as discussed above whereby the line connected to pin port PIN 3  is the ground line and the line connected to pin port PIN 4  is the microphone line. If the particular return signal is not sensed in any of the cases, it can be concluded  218  that no headset is connected. In this case, the cable that has been inserted into the jack may be, but is not limited to, a microphone without a headset, or a microphone extension cable. 
     In an alternative embodiment, detectors  54  may be associated with each of the lines and depending on which line the detection signal is transmitted, the detector for specific lines may or may not be activated for the sensing of the particular return signal or the polarity detection. 
     In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. However, it will be apparent to one skilled in the art that some or all of these specific details may not be required in order to practice the disclosure. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the disclosure. For example, specific details are not provided as to whether the embodiments of the disclosure described herein are as a software routine, hardware circuit, firmware, or a combination thereof. 
     The above-described embodiments of the disclosure are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the disclosure, which is defined solely by the claims appended hereto.