WO2009062500A1 - Fsk receiver for a hearing aid and a method for processing an fsk signal - Google Patents
Fsk receiver for a hearing aid and a method for processing an fsk signal Download PDFInfo
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- WO2009062500A1 WO2009062500A1 PCT/DK2007/000493 DK2007000493W WO2009062500A1 WO 2009062500 A1 WO2009062500 A1 WO 2009062500A1 DK 2007000493 W DK2007000493 W DK 2007000493W WO 2009062500 A1 WO2009062500 A1 WO 2009062500A1
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- hearing aid
- receiver
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
- H04R25/55—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception using an external connection, either wireless or wired
- H04R25/554—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception using an external connection, either wireless or wired using a wireless connection, e.g. between microphone and amplifier or using Tcoils
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2225/00—Details of deaf aids covered by H04R25/00, not provided for in any of its subgroups
- H04R2225/51—Aspects of antennas or their circuitry in or for hearing aids
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2225/00—Details of deaf aids covered by H04R25/00, not provided for in any of its subgroups
- H04R2225/55—Communication between hearing aids and external devices via a network for data exchange
Definitions
- This application relates to hearing aids. More specifically, it relates to hearing aids comprising wireless receivers. Still more specifically the invention relates to hearing aids comprising frequency: shift: keying (FSK) receivers.
- FSK frequency: shift: keying
- a common signal source in a hearing aid is one or more microphones picking up acoustic sound signals occurring in the vicinity of the hearing aid.
- Another common signal source in hearing aids is a telecoil receiver.
- Such a receiver is usually embodied as a tiny coil configured to pick up electromagnetic base band (i.e. unmodulated) audio frequency signals from a telecoil transmitter surrounding the hearing aid comprising the receiver.
- the: art hearing aids are usually designed to accept more than one signal source for advanced functionalities for the purpose of amplifying, conditioning and reproducing them by virtue of the hearing aid circuitry.
- Some behind:the:ear (BTE) hearing aids have means for connecting external equipment to the hearing aid circuitry, such as FM:receivers, Bluetooth® receivers, cables etc.
- external equipment enables communication with the hearing aid in various ways; e.g. a cable connection is usually provided for the purpose of programming the hearing aid, a FM: receiver may be connected for use in public address situations where a speaker is wearing a microphone with a wireless FM transmitter, and a Bluetooth® receiver may be used for streaming audio signals from a mobile telephone or the like.
- Some newer hearing aid types also comprise internal wireless receivers. Most of these wireless receiver types draw their power directly from the hearing aid battery. Prolonged use of wireless receivers known in the art may lead to rapid depletion of the hearing aid battery necessitating frequent battery changes and adding to the cost of operation of the hearing aid. Receiver types having integral power supplies comprising a separate battery add to the weight, size and complexity of the receiver. A more power: efficient wireless receiver would thus be of great benefit to hearing aid users.
- an FSK transmitter receiver configuration, well:known to persons skilled in the art, is generally preferred.
- FSK signals may be demodulated in several different ways, each having different advantages, topologies and complexity.
- the demodulators can be subdivided into several categories: FM to AM demodulator types (e.g. Slope, Foster: Seeley and Ratio), PLL demodulators, Zero: crossing demodulators and Quadrature demodulators.
- FM to AM demodulator types e.g. Slope, Foster: Seeley and Ratio
- PLL demodulators Zero: crossing demodulators
- Quadrature demodulators Quadrature demodulators.
- One quadrature demodulator type well known in the art comprises a local oscillator and two signal branches denoted the in: phase branch and the quadrature branch, respectively, splitting the received signal into an in.phase (I) component and a quadrature (Q) component.
- I in.phase
- Q quadrature
- one component is assigned binary zero
- the other component is assigned binary one.
- a digital bitstream consisting of ones and zeroes is generated whenever the transmitter is active.
- Both branches are connected to a CPU, which completes the demodulation process.
- each branch comprises a multiplier, a filter and a decision device.
- the multiplier in the in: phase branch is connected directly to the local oscillator, whereas the multiplier in the quadrature branch is connected to a 90° phase: shifted version of the local oscillator.
- the information in the frequency: shift: keyed signal is then decoded and utilized according to its intended purpose.
- Such a FSK demodulator is, for instance, described in US 4 987 374, in the name of Burke.
- This demodulator comprises a local oscillator feeding a first and a second branch, each branch comprising a mixer and a detection stage.
- the mixer in the first branch mixes the incoming signal with the direct signal from the local oscillator, and the mixer in the second branch mixes the incoming signal with a 90° phase: shifted version of the signal from the local oscillator.
- FSK receivers according to the prior art work satisfactorily in a multitude of applications.
- the available power is only small, as is the case in hearing aids, the effective transmission range is very short, and reception errors, e.g. due to noise present in the signal, may severely corrupt the quality of the received signal.
- a wireless FSK receiver suitable for use in a hearing aid according to the invention has the features presented in claim 1.
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the total bitresolution i.e. the number of discrete symbols sent per data bit
- the invention in a second aspect, provides a wireless FSK receiver as recited in claim 7.
- the invention in a third aspect, provides a method as recited in claim 9. Further features and advantages appear from the dependent claims.
- Fig. 1 is a block schematic showing a prior art wireless FSK transmitter
- Fig. 2 is a graph showing a spectrum of the signal transmitted by the transmitter in fig. 1,
- Fig. 3 is a prior art wireless FSK receiver
- Fig. 4 is a vector diagram of the signals detected by the prior art wireless FSK receiver shown in fig. 3,
- Fig. 5 is a block schematic of an embodiment of a wireless FSK receiver according to the invention.
- Fig. 6 is a timing diagram of the five branches detecting a binary "0" prior to the clipping stage in the wireless FSK receiver shown in fig. 5,
- Fig, 7 is a vector diagram of the signals detecting a binary "0" from the wireless FSK receiver shown in fig. 5,
- Fig. 8 is a timing diagram of the five branches detecting a binary "1" prior to the clipping stage in the wireless FSK receiver shown in fig. 5,
- Fig, 9 is a vector diagram of the signals detecting a binary "1" from the wireless FSK receiver shown in fig. 5
- Fig. 10 is a timing diagram of the five branches detecting a binary "0" posterior to the clipping stage in the wireless FSK receiver shown in fig. 5,
- Fig. 1 1 is a timing diagram of the five branches detecting a binary "1" posterior to the clipping stage in the wireless FSK receiver shown in fig. 5,
- Fig. 12 is an embodiment of a wireless FSK receiver of an analog, differential configuration, according to the invention.
- Fig. 13 is a hearing aid with a wireless FSK receiver according to the invention.
- a Frequency: shift: keying (FSK) transmitter 1 according to the prior art is shown in fig. 1. It comprises a serial bit stream generator 2, an inverter 3, a first mixer or multiplier 5, a first local oscillator 4, a second mixer or multiplier 6, a second local oscillator 7, a summing node 8, an output stage 9, and a transmitter antenna 10.
- a data signal m(t) is generated by the serial bit stream generator 2 and split into two branches. The signal in the lower branch is mixed with the signal from the second local oscillator 7 in the second mixer 6, and the signal in the upper branch is inverted by the inverter 3 and mixed with the signal from the first local oscillator 4 in the first mixer 5. Due to the presence of the inverter 3 in the upper branch, only one of the mixers 5, 6 produce an output signal at any time.
- the signals from the local oscillators 4, 7 may be described as:
- the FSK transmitter thus outputs one of two frequencies, determined by the local oscillators 4 and 7, depending on whether m(t) is "0" or "1".
- Fig. 2 shows part of a frequency spectrum of a FSK signal generated by the FSK transmitter in fig. 1.
- the signals are located around f c + ⁇ f and f c : ⁇ f.
- Spectral content will be different with different modulation index values and different spectral content of m(t).
- An input stage of the wireless FSK receiver 11 comprises a receiving antenna 12, an amplifier 13, and a limiter 14.
- the FSK receiver 1 1 also has a first phase detection stage comprising a first local oscillator 15a, a first mixer 16a, a first low:pass filter 17a, a first limiter 18a, a second phase detection stage comprising a second local oscillator 15b, a second mixer 16b, a second low: pass filter 17b, a second limiter 18b, and a CPU interface 19.
- An FSK signal is picked up by the receiving antenna 12 and amplified by the amplifier 13 and conditioned by the limiter 14.
- the output of the limiter 14 is split into two branches and fed to an input of the first mixer 16a and an input of the second mixer 16b, respectively.
- the input signal is multiplied with the output signal from the first local oscillator 15a.
- the resulting output signals are fed to inputs of the first low:pass filter 17a and the output signals from the first low:pass filter 17a are fed to inputs of the first limiter 18a.
- the input signal is multiplied with the output signal from the second local oscillator 15b.
- the resulting output signals are fed to inputs of the second low:pass filter 17b and the output signals from the second low: pass filter 17b are fed to inputs of the second limiter 18b.
- the output signals from the first limiter 18a and the second limiter 18b are fed to the input of the CPU interface 19 for further processing.
- Fig. 4 is a vector diagram showing the vectors I (in:phase) and Q (quadrature: phase) of the signal received by the prior art receiver shown in fig. 3.
- the vectors I and Q are depicted on the unit circle and have a mutual phase difference of 90°.
- the phase deviation between the abscissa (0°) and the vector I is denoted ⁇ - 1 and represents the angular symbol resolution of the prior art receiver 1 1.
- noise and EMC interference present in the received signal may reduce the receiving capability of the prior art receiver 11 significantly, eventually to the point where information gets garbled, distorted or lost completely.
- the reception quality may be improved in several ways, for instance by increasing the transmitter power, decreasing the transmission distance, or improving the receiver selectivity.
- a block schematic of a wireless FSK receiver 20 according to an embodiment of the invention is shown in fig. 5.
- the wireless FSK receiver 20 is a single ended FSK receiver.
- An input stage of the wireless receiver 20 comprises a receiving antenna 12, an amplifier 13, and a limiter 14, similar to the input stage of the wireless receiver 11 of the prior art.
- the FSK receiver 20 comprises five identical demodulator branches, each demodulator branch comprising a local oscillator 15a, 15b, 15c, 15d, 15e, a mixer 16a, 16b, 16c, 16d, 16e, a low:pass filter 17a, 17b, 17c, 17d, 17e, and a limiter 18a, 18b, 18c, 18d, 18e, respectively.
- each of the limiters 18a, 18b, 18c, 18d, 18e, respectively, are connected to inputs of a look:up table block 28 comprising weights xi, x 2 , x 3 , X 4 , x 5 , weights yi, y 2 , y 3 , y 4 , y 5 , a first summer ⁇ x and a second summer ⁇ y , and an Arctan2: function 21.
- Each output of the limiters 18a, 18b, 18c, 18d, 18e of the wireless FSK receiver 20 feeds an input of the look:up table 28, and is split into two separate sets of branches which are weighted with x, and y,, respectively.
- the outputs from the weights xi, x 2 , X 3 , X 4 , and X 5 are summed in the first summer ⁇ x
- the outputs from the weights V 1 , y 2 , Y 3 , y » and ys are summed in the second summer ⁇ y.
- the outputs of the summers ⁇ x and ⁇ y are fed to the inputs of the Arctan2: function 21, and the output of the Arctan2: function 21 of the look:up table 28 is connected to the input of a differentiator 22.
- the Arctan2: function is explained in further detail in the following.
- the two:argument arcus tangent function used in this context is a variant of the arcus tangent function Arctan2(x,y) and is defined as:
- the output of the differentiator 22 is connected to the input of a low:pass filter 23, the output of the low:pass filter 23 is connected to the input of a comparator 27, and the output of the comparator 27 is connected to the input of a clock data recovery block 24.
- the clock data recovery block 24 is connected to a buffer 25 via a clock line C and a data line D.
- the output of the buffer 25 is connected to the input of a serial peripheral interface 26.
- the antenna 12 picks up a transmitted signal and the amplifier 13 amplifies the received signal to a signal level suitable for input to the limiter 14.
- the received signal is assumed to be a frequency: modulated, frequency: shift: keyed analog bit stream.
- the received signal is converted into a two: level digital bit stream by virtue of the limiter 14. This signal is then presented to the inputs of the first, second, third, fourth and fifth demodulator branches as described in the following.
- the first demodulator branch 15a, 16a, 17a, 18a converts and conditions a first part of the signal output by the limiter 14.
- the first local oscillator 15a and the first mixer 16a converts the received signal into a baseband signal.
- the first mixer 16a outputs a direct converted version of the transmitted signal for the first low:pass filter 17a, and the signals from the outputs of the first filter 17a are used as the input signals for the first limiter 18a, acting as a decision device in the first branch 15a, 16a, 17a, and 18a.
- the output of the first limiter 18a is a logical, digital level, which is used as argument for the weights xi and yi, summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look:up table 28.
- the second demodulator branch 15b, 16b, 17b, 18b converts and conditions a second part of the signal output by the limiter 14.
- the output signal from the second local oscillator 15b is shifted in phase by ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the second local oscillator 15b and the second mixer 16b converts the received signal into a baseband signal.
- the second mixer 16b outputs a direct converted version of the transmitted signal for the second low:pass filter 17b, and the signals from the outputs of the second filter 17b are used as the input signals for the second limiter 18b, acting as a decision device in the second branch 15b, 16b, 17b, and 18b.
- the output of the second limiter 18b is a logical, digital level, which is used as argument for the weights x 2 and y 2 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look: up table 28.
- the third demodulator branch 15c, 16c, 17c, 18c converts and conditions a third part of the signal output by the limiter 14.
- the output signal from the third local oscillator 15c is shifted in phase by 2 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the third local oscillator 15c and the third mixer 16c converts the received signal into a baseband signal.
- the third mixer 16c outputs a direct converted version of the transmitted signal for the third low:pass filter 17c, and the signals from the outputs of the third filter 17c are used as the input signals for the third limiter 18c, acting as a decision device in the third branch 15c, 16c, 17c, and 18c.
- the output of the third limiter 18c is a logical, digital level, which is used as argument for the weights X 3 and y 3 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look:up table 28.
- the fourth demodulator branch 15d, 16d, 17d, 18d converts and conditions a fourth part of the signal output by the limiter 14.
- the output signal from the fourth local oscillator 15d is shifted in phase by 3 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the fourth local oscillator 15d and the fourth mixer 16d converts the received signal into a baseband signal.
- the fourth mixer 16d outputs a direct converted version of the transmitted signal for the fourth low:pass filter 17d, and the signals from the outputs of the fourth filter 17d are used as the input signals for the fourth limiter 18d, acting as a decision device in the fourth branch 15d, 16d, 17d, and 18d.
- the output of the fourth limiter 18d is a logical, digital level, which is used as argument for the weights X 4 and y 4 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look:up table 28.
- the fifth demodulator branch 15e, 16e, 17e, 18e converts and conditions a fifth part of the signal output by the limiter 14.
- the output signal from the fifth local oscillator 15e is shifted in phase by 4 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the fifth local oscillator 15e and the fifth mixer 16e converts the received signal into a baseband signal.
- the fifth mixer 16d outputs a direct converted version of the transmitted signal for the fifth low:pass filter 17d, and the signals from the outputs of the fifth filter 17d are used as the input signals for the fifth limiter 18e, acting as a decision device in the fifth branch 15e, 16e, 17e, and 18e.
- the output of the fifth limiter 18e is a logical, digital level, which is used as argument for the weights X 5 and ys, summed in the summers ⁇ x and ⁇ y, to provide the inputs for the Arctan2: function 21 of the look: up table 28.
- the Arctan2: function 21 thus receives the summed, logical levels x, and y, from the five demodulator branches and uses the levels as arguments to the Arctan2: function 21.
- the Arctan2(x,, y,) function 21 thus derives the rotational vector ⁇ (t), which is used as the input for the differentiator 22.
- the output signal from the differentiator 22 is low:pass filtered in the low:pass filter 23, and the output signal from the low:pass filter 23 is passed to the comparator 27, which acts as a decision device for the demodulator.
- the output from the comparator 27 is used as input to the clock data recovery block 24.
- the clock data recovery block 24 extracts embedded clock pulses from the serial data signal presented to it by the low:pass filter 23, and presents the recovered clock pulses to the buffer 25 through the clock line C, and the serial data signals through the data line D.
- the embedded clock pulses are used by the serial parallel interface to resynchronize the buffered data signals.
- the buffer 25 collects a predetermined number of received data bits, and presents the data bits to the serial peripheral interface 26.
- the serial peripheral interface 26 is configured to fetch the buffered data before the buffer 25 is full.
- the wireless receiver 20 is capable of detecting the phase difference between individual digital symbols in the received data stream with greater accuracy than FSK receivers known in the prior art. Assuming that each of the five local oscillators 15a, 15b, 15c, 15d, 15e, outputs a signal LO,(t) given as:
- the demodulated signal u,(t) for each branch / ' in the FSK receiver 20 may be described as:
- the half: period of each curve u corresponds to the time period ⁇ / ⁇
- the order of the curves corresponds to the counterclockwise sequence of the five vectors uj, U 2 , u 3 , u 4 , and U 5 representing the five detected signals in the vector graph shown in fig. 7.
- the phase deviation is ⁇ /5 and represents the angular symbol resolution of the receiver 20 according to the invention.
- the half: period of each curve u corresponds to the time period ⁇ / ⁇
- the order of the curves correspond to the clockwise sequence of the five vectors U 5 , U 4 , U 3 , U 2 , and U] representing the five detected signals in the vector graph shown in fig. 9.
- the symbol resolution is finer than that obtained by the FSK receiver 11 of the prior art.
- a progressive sequence of the five detected vectors in the five branches corresponds to a detected, logical O'
- a regressive sequence of the five detected vectors in the five branches corresponds to a detected, logical T.
- This corresponds to a counterclockwise rotation as shown in the vector graph in fig. 7 when a '0' is detected and a clockwise rotation as shown in the vector graph in fig. 9 when a ' 1 ' is detected.
- M 1 is detected first, followed by U 2 , U 3 , M 4 , and M 5 . This tells the receiver that the signal vector ⁇ (t) is moving clockwise, and that a T is received.
- M 5 is detected first, followed by M 4 , M 3 , U 1 , and M 1 .
- M 4 is detected first, followed by M 4 , M 3 , U 1 , and M 1 .
- This tells the receiver that the signal vector ⁇ (t) is moving counterclockwise, and that a '0' is received.
- the signals U 1 , y,, x, and the function Arctan2(y,, X 1 ) are used to determine whether the rotation of the vector is clockwise, interpreted as a T, or counterclockwise, interpreted as a O'.
- m(t) 1
- the signals M may be described by the matrix A:
- the signal presented to the FSK receiver has either a positive or a negative slope, a positive slope corresponding to a clockwise rotation in the unit circle diagram and thus representing a binary T, and a negative slope corresponding to a counterclockwise rotation in the unit circle diagram and thus representing a binary O'.
- the FSK receiver 20 determines whether signal is rising or falling, i.e. the vector is moving clockwise or counterclockwise in the unit circle diagram, e.g. by taking the difference between two values of ⁇ (t) during one bit duration, determine if ⁇ (t) goes positive or negative within that bit duration period and thus decide if the transmitted symbol is a binary '0' or a binary T.
- the modulation index is defined as:
- ⁇ — — , where Af is the deviation frequency [Hz] , and DR is the data : rate [&/Ys/s] DR. If the resulting vector rotates with the angular velocity ⁇ :
- To is the period of the deviation frequency of the modulated signal. This implies that the resulting vector rotates ⁇ radians in the unit circle pr. bit.
- N is the number of branches in the system.
- the bit resolution represents the number of points in the unit circle per data bit. As the number of branches is increased, the bit resolution is increased proportionally as the number of detectable symbols representing each bit is increased, and, as a consequence, the detection of each bit is improved.
- this gives five distinct angular values for ⁇ (t) pr. bit, as opposed to just two distinct angular values in the receiver known in the prior art, i.e. a bit resolution of S - ⁇ resulting in a higher detection accuracy and thus a better noise immunity.
- FIG. 12 Another preferred embodiment 30 of a wireless FSK receiver according to the invention is shown in fig. 12.
- the wireless receiver 30 is a differential FSK receiver.
- Differential FSK receivers per se are known in the art, and they have several practical advantages over single ended FSK receiver implementations. From an architectural viewpoint, the differential implementation shows no significant differences over the single ended implementation, but in practice, the differential implementation has a better noise immunity.
- differential FSK receiver embodiment of the invention shown in fig. 12 is described in greater detail in the following.
- An input stage of the wireless receiver 30 comprises a receiving antenna 12 and an amplifier 13.
- An input limiter is not necessary in this implementation.
- the amplifier 13 is connected via a two: wire interface bus to two inputs of each of five mixers 16a, 16b, 16c, 16d, 16e, respectively.
- Five local square: wave oscillators 15a, 15b, 15c, 15d, 15e each comprise two outputs, where one output is connected to the input of a respective one among five inverters 29a, 29b, 29c, 29d, 29e, and one output is connected directly to an input of a respective one among the five mixers 16a, 16b, 16c, 16d, 16e.
- the outputs of the five inverters 29a, 29b, 29c, 29d, 29e are connected to yet another input of the five mixers 16a, 16b, 16c, 16d, 16e, respectively.
- the signals from the local square:wave oscillators 15a, 15b, 15c, 15d, 15e differ in phase increments of ⁇ /5.
- inverters 29a, 29b, 29c, 29d, 29e The purpose of the inverters 29a, 29b, 29c, 29d, 29e is to supply the mixers 16a, 16b, 16c, 16d, 16e, respectively, with a 180° phase: inverted version of the direct signal from the local oscillators 15a, 15b, 15c, 15d, 15e, respectively.
- the five mixers 16a, 16b, 16c, 16d, 16e each thus receives four separate signals for mixing, a real input signal and a phase: inverted input signal from the input stage 12, 13, a real local oscillator signal from each of the local square:wave oscillators 15a, 15b, 15c, 15d, 15e, respectively, and a phase: inverted local oscillator signal from each of the inverters 29a, 29b, 29c, 29d, 29e, respectively.
- the output signals from the five mixers 16a, 16b, 16c, 16d, 16e comprise five signal pairs with a phase difference of 36° between each signal pair for further processing.
- the signal pairs from the five mixers 16a, 16b, 16c, 16d, 16e are connected to the inputs of five band:pass filters 31a, 31b, 31c, 3 Id, 3 Ie, respectively.
- the outputs of the five band:pass filters 31a, 31b, 31c, 3 Id, 31e, also forming signal pairs, are connected to the inputs of five limiters 18a, 18b, 18c, 18d, 18e, respectively.
- the outputs of the five limiters 18a, 18b, 18c, 18d, 18e are connected to the inputs of a look: up table 28 comprising weights Xi, X 2 , X 3 , X 4 , X 5 , weights y ls y 2 , y 3 , y 4 , ys, a first summer ⁇ x and a second summer ⁇ y , and an Arctan2: function 21.
- the look: up table 28 and the downstream subsequent blocks in fig. 12 are configured in a manner similar to that of the wireless receiver 20 shown in fig. 5.
- the signals Upstream from the five limiters 18a, 18b, 18c, 18d, 18e, the signals are considered to be analog. Downstream from the five limiters 18a, 18b, 18c, 18d, 18e, the signals are considered to be digital. This strategic placement of the five limiters 18a, 18b, 18c, 18d, 18e, posterior to the mixers 16a, 16b, 16c, 16d, 16e, also aids in keeping power consumption low, as digital switching in the base band requires less power than digital switching at high frequencies such as the FSK transmission frequencies.
- the first demodulator branch 15a, 29a, 16a, 31a, 18a converts and conditions a first part of the signal output by the preamplifier 13.
- the first local oscillator 15a converts the received signal to a baseband signal.
- the first mixer 16a outputs a direct converted version of the transmitted signal for the first band:pass filter 31a, and the signals from the outputs of the first band:pass filter 31a are used as the input signals for the first limiter 18a, acting as a decision device for the first branch 15a, 29a, 16a, 31a, 18a.
- the output of the first limiter 18a is a logical, digital level, which is used as argument for the branches X 1 and yi, summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look:up table 28.
- the second demodulator branch 15b, 29b, 16b, 31b, 18b converts and conditions a second part of the signal output by the preamplifier 13.
- the second local oscillator 15b converts the received signal to a baseband signal.
- the second local oscillator 15b is shifted in phase by ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the second mixer 16b outputs a direct converted version of the transmitted signal for the second band:pass filter 31b, and the signals from the outputs of the second band:pass filter 31b are used as the input signals for the second limiter 18b, acting as a decision device for the second branch 15b, 29b, 16b, 31b, 18b.
- the output of the second limiter 18b is a logical, digital level which is used as argument for the branches X 2 and y 2 , summed in the summers ⁇ x and ⁇ y, to provide the inputs for the Arctan2: function 21 of the look: up table 28.
- the third demodulator branch 15c, 29c, 16c, 31c, 18c converts and conditions a third part of the signal output by the preamplifier 13.
- the third local oscillator 15c converts the received signal to a baseband signal.
- the third local oscillator 15c is shifted in phase by 2 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the third mixer 16c outputs a direct converted version of the transmitted signal for the third band:pass filter 31c, and the signals from the outputs of the third band:pass filter 31c are used as the input signals for the third limiter 18c, acting as a decision device for the third branch 15c, 29c, 16c, 31c, 18c.
- the output of the third limiter 18c is a logical, digital level which is used as argument for the branches X 3 and y 3 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look: up table 28.
- the fourth demodulator branch 15d, 29d, 16d, 3 Id, 18d converts and conditions a fourth part of the signal output by the preamplifier 13.
- the fourth local oscillator 15d converts the received signal to a baseband signal.
- the fourth local oscillator 15d is shifted in phase by 3 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the fourth mixer 16d outputs a direct converted version of the transmitted signal for the fourth band:pass filter 3 Id, and the signals from the outputs of the fourth band:pass filter 3 Id are used as the input signals for the fourth limiter 18d, acting as a decision device for the fourth branch 15d, 29d, 16d, 3 Id, 18d.
- the output of the fourth limiter 18d is a logical, digital level which is used as argument for the branches X 4 and y 4 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look:up table 28.
- the fifth demodulator branch 15e, 29e, 16e, 3 Ie, 18e converts and conditions a fifth part of the signal output by the preamplifier 13.
- the fifth local oscillator 15e converts the received signal to a baseband signal.
- the fifth local oscillator 15e is shifted in phase by 4 ⁇ /5 when compared to the output signal from the first local oscillator 15a.
- the fifth mixer 16e outputs a direct converted version of the transmitted signal for the fifth band:pass filter 3 Ie, and the signals from the outputs of the fifth band:pass filter 3 Ie are used as the input signals for the fifth limiter 18e, acting as a decision device for the fifth branch 15e, 29e, 16e, 3 Ie, 18e.
- the output of the fifth limiter 18e is a logical, digital level which is used as argument for the branches X 5 and y 5 , summed in the summers ⁇ x and ⁇ y , to provide the inputs for the Arctan2: function 21 of the look: up table 28.
- the received signals are amplified by the input amplifier 13 and presented to the five branches as differential analog signals.
- the differential signals are converted, i.e. folded, down in frequency from the transmission frequency to the base band frequency, in the mixers 16a, 16b, 16c, 16d, 16e, respectively, by the signals from the local square: wave oscillators 15a, 15b, 15c, 15d, 15e, respectively, and the inverted square: wave signals from the inverters 29a, 29b, 29c, 29d, 29e, respectively.
- the down: converted signals from the mixers 16a, 16b, 16c, 16d, 16e, respectively, are band: limited in the band:pass filters 31a, 31b, 31c, 3 Id, 31e, respectively, and the band:limited signals from the band:pass filters 31a, 31b, 31c, 3 Id, 31e, respectively, are limited by the five limiters 18a, 18b, 18c, 18d, 18e, respectively, and thus converted into logical levels presented to the summation points ⁇ x and ⁇ y , respectively via the weights x, and y,, respectively.
- the summation points ⁇ x and ⁇ y present their outputs to the Arctan2: function 21 of the lookrup table 28.
- the subsequent blocks, the differentiator 22, the low:pass filter 23, the decision block 27, the clock data recovery block 24, the buffer 25, and the serial peripheral interface 26, have a similar configuration and functionality as in the embodiment shown in fig. 5.
- the embodiment of the wireless FSK receiver 30 shown in fig. 12 further benefits from the fact that the limiting of the received signal is performed in the base band, i.e. posterior to the conversion stages comprised of the mixers 16a, 16b, 16c, 16d, 16e, respectively. This further reduces the current consumption of the wireless FSK receiver 30, resulting in prolonged battery life, even during prolonged continuous operation of the receiver 30 according to the invention.
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Neurosurgery (AREA)
- Otolaryngology (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
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Abstract
Description
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Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN200780101511A CN101855879A (en) | 2007-11-12 | 2007-11-12 | Fsk receiver for a hearing aid and a method for processing an fsk signal |
CA2705382A CA2705382C (en) | 2007-11-12 | 2007-11-12 | An fsk receiver for a hearing aid and a method for processing an fsk signal |
AU2007361114A AU2007361114B2 (en) | 2007-11-12 | 2007-11-12 | FSK receiver for a hearing aid and a method for processing an FSK signal |
PCT/DK2007/000493 WO2009062500A1 (en) | 2007-11-12 | 2007-11-12 | Fsk receiver for a hearing aid and a method for processing an fsk signal |
JP2010532433A JP4939656B2 (en) | 2007-11-12 | 2007-11-12 | FSK receiver for hearing aid and method for processing FSK signal |
EP07817889A EP2223487B1 (en) | 2007-11-12 | 2007-11-12 | Fsk receiver for a hearing aid and a method for processing an fsk signal |
DK07817889.4T DK2223487T3 (en) | 2007-11-12 | 2007-11-12 | FSK receiver for a hearing aid and method for processing an FSK signal |
AT07817889T ATE519307T1 (en) | 2007-11-12 | 2007-11-12 | FSK RECEIVER FOR A HEARING AID AND METHOD FOR PROCESSING A FSK SIGNAL |
US12/777,652 US8498434B2 (en) | 2007-11-12 | 2010-05-11 | FSK receiver for a hearing aid and a method for processing an FSK signal |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/DK2007/000493 WO2009062500A1 (en) | 2007-11-12 | 2007-11-12 | Fsk receiver for a hearing aid and a method for processing an fsk signal |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/777,652 Continuation-In-Part US8498434B2 (en) | 2007-11-12 | 2010-05-11 | FSK receiver for a hearing aid and a method for processing an FSK signal |
Publications (1)
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WO2009062500A1 true WO2009062500A1 (en) | 2009-05-22 |
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Family Applications (1)
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PCT/DK2007/000493 WO2009062500A1 (en) | 2007-11-12 | 2007-11-12 | Fsk receiver for a hearing aid and a method for processing an fsk signal |
Country Status (9)
Country | Link |
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US (1) | US8498434B2 (en) |
EP (1) | EP2223487B1 (en) |
JP (1) | JP4939656B2 (en) |
CN (1) | CN101855879A (en) |
AT (1) | ATE519307T1 (en) |
AU (1) | AU2007361114B2 (en) |
CA (1) | CA2705382C (en) |
DK (1) | DK2223487T3 (en) |
WO (1) | WO2009062500A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012092973A1 (en) | 2011-01-07 | 2012-07-12 | Widex A/S | A hearing aid system with a dual mode wireless radio |
WO2012116721A1 (en) | 2011-02-28 | 2012-09-07 | Widex A/S | Hearing aid and a method of driving an output stage |
US9706315B2 (en) | 2013-02-07 | 2017-07-11 | Widex A/S | Transceiver for a hearing aid and a method for operating such a transceiver |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US8503962B2 (en) * | 2007-06-29 | 2013-08-06 | Silicon Laboratories Inc. | Implementing a rotating harmonic rejection mixer (RHRM) for a TV tuner in an integrated circuit |
US7756504B2 (en) | 2007-06-29 | 2010-07-13 | Silicon Laboratories Inc. | Rotating harmonic rejection mixer |
JP5913617B2 (en) * | 2011-11-25 | 2016-04-27 | ヴェーデクス・アクティーセルスカプ | Automatic FSK tuning circuit and method for hearing aids |
CN106227291A (en) * | 2016-07-26 | 2016-12-14 | 中国科学院自动化研究所 | The implementation method of arctan function based on stagewise look-up table and realize device |
US10084625B2 (en) | 2017-02-18 | 2018-09-25 | Orest Fedan | Miniature wireless communication system |
US20180315453A1 (en) * | 2017-04-28 | 2018-11-01 | Tymphany Worldwide Enterprises Limited | Audio integrated circuit |
US10770928B2 (en) * | 2017-06-06 | 2020-09-08 | Apple Inc. | Wireless charging device with multi-tone data receiver |
EP3506655A1 (en) * | 2017-12-29 | 2019-07-03 | GN Hearing A/S | A hearing instrument comprising a magnetic induction antenna |
Citations (2)
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US4529941A (en) | 1982-11-29 | 1985-07-16 | Arthur D. Little, Inc. | FSK Demodulator utilizing multiple-phase reference frequencies |
US20050105653A1 (en) | 2003-11-19 | 2005-05-19 | Oki Electric Industry Co., Ltd. | FSK signal detector |
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US4987374A (en) * | 1989-10-05 | 1991-01-22 | Burke Dennis E | FSK demodulator |
FR2711027B1 (en) * | 1993-10-05 | 1995-11-17 | Ebauchesfabrik Eta Ag | Phase shift and amplitude correction circuit. |
WO2000028664A2 (en) * | 1998-11-12 | 2000-05-18 | Broadcom Corporation | Fully integrated tuner architecture |
DK1867207T3 (en) * | 2005-01-17 | 2008-10-13 | Widex As | An apparatus and method for operating a hearing aid |
-
2007
- 2007-11-12 EP EP07817889A patent/EP2223487B1/en active Active
- 2007-11-12 WO PCT/DK2007/000493 patent/WO2009062500A1/en active Application Filing
- 2007-11-12 JP JP2010532433A patent/JP4939656B2/en not_active Expired - Fee Related
- 2007-11-12 AU AU2007361114A patent/AU2007361114B2/en active Active
- 2007-11-12 AT AT07817889T patent/ATE519307T1/en not_active IP Right Cessation
- 2007-11-12 CN CN200780101511A patent/CN101855879A/en active Pending
- 2007-11-12 DK DK07817889.4T patent/DK2223487T3/en active
- 2007-11-12 CA CA2705382A patent/CA2705382C/en active Active
-
2010
- 2010-05-11 US US12/777,652 patent/US8498434B2/en active Active
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4529941A (en) | 1982-11-29 | 1985-07-16 | Arthur D. Little, Inc. | FSK Demodulator utilizing multiple-phase reference frequencies |
US20050105653A1 (en) | 2003-11-19 | 2005-05-19 | Oki Electric Industry Co., Ltd. | FSK signal detector |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2012092973A1 (en) | 2011-01-07 | 2012-07-12 | Widex A/S | A hearing aid system with a dual mode wireless radio |
US9344816B2 (en) | 2011-01-07 | 2016-05-17 | Widex A/S | Hearing aid system and a hearing aid |
WO2012116721A1 (en) | 2011-02-28 | 2012-09-07 | Widex A/S | Hearing aid and a method of driving an output stage |
US8837758B2 (en) | 2011-02-28 | 2014-09-16 | Widex A/S | Hearing aid and method of driving an output stage |
US9706315B2 (en) | 2013-02-07 | 2017-07-11 | Widex A/S | Transceiver for a hearing aid and a method for operating such a transceiver |
Also Published As
Publication number | Publication date |
---|---|
CN101855879A (en) | 2010-10-06 |
EP2223487B1 (en) | 2011-08-03 |
ATE519307T1 (en) | 2011-08-15 |
US8498434B2 (en) | 2013-07-30 |
AU2007361114B2 (en) | 2011-09-08 |
JP2011503980A (en) | 2011-01-27 |
JP4939656B2 (en) | 2012-05-30 |
EP2223487A1 (en) | 2010-09-01 |
CA2705382A1 (en) | 2009-05-22 |
US20100220878A1 (en) | 2010-09-02 |
AU2007361114A1 (en) | 2009-05-22 |
CA2705382C (en) | 2014-11-18 |
DK2223487T3 (en) | 2011-09-12 |
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