Acoustic device and method for amplifying and imprinting information on an interrogating signal

Abstract

An acoustic transponder provides information related to the transponder when the transponder is receiving an acoustic interrogating signal. The transponder includes a power supply, an electronic circuit connected to the power supply, and one or more transducers receiving and emitting the acoustic signal. The electronic circuit includes a sequence generator. The transponder further includes an amplification and modulation unit, an extraction filter, and a suppression filter. The extraction filter is adapted to extract the received acoustic interrogating signal and suppress other signals prior to being input to the amplification and modulation unit which are configured to modulate the received acoustic signal according to a sequence generated by the sequence generator and to amplify the modulated signal. The suppression filter is adapted to suppress the received acoustic interrogating signal from the amplified and modulated signal. The amplified modulated signal is transferred through the one or more transducers of the transponder and/or through other transducer(s).

Claims

1. An acoustic transponder providing information related to the transponder when the transponder is receiving an acoustic interrogating signal, the transponder comprises a power supply, an electronic circuit connected to the power supply, and one or more transducers receiving and emitting the acoustic signal, the electronic circuit comprises a sequence generator, the transponder further comprising: an amplification and modulation unit, an extraction filter, and a suppression filter, wherein the extraction filter is adapted to extract the received acoustic interrogating signal and suppress other signals prior to being input to the amplification and modulation unit which are configured to modulate the received acoustic signal according to a sequence generated by the sequence generator and to amplify the modulated signal, wherein the suppression filter is adapted to suppress the received acoustic interrogating signal from the amplified and modulated signal, and wherein the amplified modulated signal is transferred through the one or more transducers the transponder and/or through other transducer(s).

2. The acoustic transponder according to claim 1, wherein the extraction filter is a hand-pass filter adapted to suppress signals other than the incoming acoustic interrogating signal.

3. The acoustic transponder according to claim 1, wherein the extraction filter is a combination of a. high-pass filter and a low-pass filter adapted to suppress signals other than the incoming acoustic interrogating signal.

4. The acoustic transponder according to claim 1, wherein the suppression filter is a band-stop filter adapted to pass the amplified modulated signal and suppress other signals.

5. The acoustic transponder according to claim 1, wherein the suppression filter is a combination of a high-pass filter and a low-pass filter adapted to pass the amplified modulated signal and suppress other signals.

6. The acoustic transponder according to claim 1, wherein the extraction filter and the suppression filter are combined into one filter unit.

7. The acoustic transponder according to claim 1, wherein the amplification and modulation unit is connected to a trigger unit adapted to activate the amplification and modulation unit only when the transponder receives an acoustic interrogating signal entering the transponder.

8. The acoustic transponder according to claim 1, wherein the amplifier is adapted to only amplify signals above a set amplitude level.

9. The acoustic transponder according to claim 1, wherein the amplification and modulation unit is adapted to imprint the transmitted signal with any type of static and/or dynamic information.

10. The acoustic transponder according to claim 1, comprising one or more amplifiers in the signal chain.

11. The acoustic transponder according to claim 1, comprising a directional coupler connected between the extraction filter and the suppression filter in the electronic circuit for connecting the transducer to the extraction filter and the suppression filter.

12. The acoustic transponder according to claim 1, wherein the extraction filter, suppression filter and the sequence generator are implemented in the electronic circuit as a digital solution comprising an amplifier connected to the transducer and a 1.sup.st anti-aliasing filter connected to a A/D converter that is connected to a digital filtering and modulation unit which is connected to a D/A converter that is connected to a 2.sup.nd anti-aliasing filter which is connected to the transducer and the 1.sup.st anti-aliasing filter.

13. A method for providing information related to a transponder when the transponder is receiving an acoustic interrogating signal, the transponder comprises a power supply, an electronic circuit connected to the power supply and one or more transducers receiving the acoustic signal, the method comprising: extracting the received acoustic interrogating signal and suppressing other signals, by means of an extraction filter, prior to being input to an amplification and modulation unit, suppressing the received acoustic interrogating signal from the amplified and modulated signal by means of a suppression filter, modulating the received acoustic signal according to a sequence generated by a sequence generator comprised in the electronic circuit and amplifying the modulated signal in an amplification and modulation unit comprised in the electronic circuit, suppressing the received acoustic interrogating signal from the amplified and modulated signal by means of a suppression filter, and transferring the amplified modulated signal through the one or more transducers of the transponder and/or through another transducer(s).

14. The method according to claim 13, by using same transducer(s) for both receiving and transmitting signals.

15. The method according to claim 13, by using different nsducer(s) for receiving and transmitting signals.

16. The method according to claim 13, wherein the modulation is performed by using amplitude modulation with two or more modulator states.

17. The method according to claim 13, wherein the modulation is performed by using phase modulation with two or more modulation states.

18. The method according to claim 13, wherein the modulation is performed by using quadrature amplitude modulation with four or more modulation states.

19. The method according to claim 13, wherein the modulation is performed by changing the amplitude and/or phase of the amplified signal in accordance with information bits entering the modulator.

20. The method according to claim 13, wherein the modulation is performed by using amplitude modulation and letting the amplification and modulation unit enter an active or idle state in accordance with information bits entering the modulator.

21. The method according to claim 13, wherein modulation is provided by switching the input of the amplification and modulation unit between two or more amplitude and/or phase shifted versions of signal output from the extraction filter (32).

22. The method according to claim 13, by letting a trigger unit comprised in the electronic circuit activate the amplification and modulation unit when receiving an input signal above a set threshold level for a set minimum of time.

23. The method according to claim 13, by letting a trigger unit comprised in the electronic circuit activate the amplification and modulation unit when receiving an input signal according to a set signal.

24. The method according to claim 23, by letting the set signal be an input signal that is above a set threshold level within a minimum time duration.

25. The method according to claim 23, by letting the set signal be an input signal that is above a set threshold level for a certain percentage of time within a minimum time duration.

26. The method according to claim 13, by feeding a locally generated signal to the amplification and modulation unit in addition to or instead of the signal extracted from the transducer(s) comprised in the transponder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The following figures are used for explaining the present invention in the following detailed description:

(2) FIG. 1 shows different modules comprised in the acoustic transponder;

(3) FIG. 2 shows a block diagram of a basic transponder;

(4) FIG. 3 shows a block diagram of a transponder with a trigger unit for power;

(5) FIG. 4 shows a block diagram of a transponder comprising sensors;

(6) FIG. 5 shows a block diagram of a transponder comprising a directional coupler;

(7) FIG. 6 shows a block diagram of a transponder implemented as a digital solution.

DETAILED DESCRIPTION OF THE INVENTION

(8) The acoustic transponder according to the invention will now be described in detail with reference to the figures.

(9) FIG. 1 shows an embodiment of the invention comprising different modules comprised in the acoustic transponder 10.

(10) The transponder 10 comprises a power supply 20, an electronic circuit 30 connected to the power supply 20 and one or more transducers 40 receiving the acoustic signal. The electronic circuit 30 comprises at least a sequence generator 50 and an amplification and modulation unit 60.

(11) In the embodiment shown in FIG. 1 the electronic circuit 30 further comprises an extraction filter 32 and a suppression filter 34. The extraction filter 32 acts as an interrogating receiver only passing recognizable signals.

(12) When the acoustic transducer 40 receives acoustic energy, the energy is converted into electric energy. The received acoustic signal from the transducer 40 is fed through the extraction filter 32 before being modulated and amplified by means of the sequence generator 50 and the amplification and modulation unit 60. The modulation performed is according to a sequence generated by the sequence generator 50.

(13) The amplification and modulation unit 60 can be implemented in different ways. One implementation is an amplifier followed by a mixer. The signal from the extraction filter 32 is first amplified before being input to a mixer adding a sequence from the sequence generator 50. Another implementation is to provide a mixer followed by an amplifier. In this configuration a sequence from the sequence generator 50 is added to the signal from the extraction filter 32 before being amplified. In yet another embodiment, amplifiers are provided both before and after a mixer.

(14) Binary phase-shift keying (BPSK) modulation can be provided by inputting a sequence in the mixer while switching between the interrogation signal received from the extraction filer 32 and an inverted version of this signal. Other modulation types are possible, e.g. selecting between different phase shifted versions of the interrogating signal in the mixer.

(15) By providing the amplifier(s) with an enable control, amplitude modulation (AM) of the signal is possible.

(16) The sequence generator 50 is a logic circuit that feeds the amplification and modulation unit 60 with a bit stream, that is imprinted on the interrogating acoustic signal. The logic may be implemented in a custom logic circuit, a FPGA/CPLD, a microcontroller, or a combination of these technologies. The generated sequence may comprise some known bits, used by the interrogating receiver to search for the signal from the transducer, some predefined or programmed identification bits, and possibly some bits from a sensor (ref. FIG. 4), that will vary dynamically with the sensor data.

(17) The amplified and modulated signal is then transferred via the suppression filter 34 through the one or more transducers 40 of said transponder 10. The amplified and modulated signal may also be fed through a transducer other than the transducer 40 receiving the acoustic signal.

(18) The extraction filter 32 is adapted to extract a received acoustic interrogating signal and to supress other signals prior to being input to the amplification and modulation unit 60. The resulting output from the extraction filter 32 will be the interrogating signal, with possible minor additive noise impairments.

(19) The suppression filter 34 is adapted to pass the signal imprinted with information from the amplification and modulation unit 60, and further to suppress the original interrogating signal. This will avoid a signal loop made by the extraction filter 32 and the amplification and modulation unit 60 with loop gain higher than one, which might lead to self-oscillations. The extraction filter 32 may be a passive filter or a combination of passive and active filters. An active filter section might be combined with the amplifier in the amplification and modulation unit 60.

(20) FIG. 2 shows a simple block diagram of one embodiment of the acoustic transponder 10 according to the invention. The electronic circuit 30 comprises a sequence generator 50 connected to an amplification and modulation unit 60. Signals from the sequence generator 50 is fed to the amplifier and modulation unit 60. In this way, acoustic signals received by the transducer 40 and extracted by the extraction filter 32 are modulated according to a sequence generated by the sequence generator 50. The modulated signal, which is a signal imprinted with information defined by the sequence, is then sent through a suppression filter 34, that is separating the original interrogating signal by only passing the amplified and modulated signal. The resulting signal is then sent to one or more transducers 40 converting the signal to acoustic energy. In this configuration, a power supply 20 is powering all components comprised in the electronic circuit 30. The transducer(s) 40 used can be the same as the one receiving the original interrogating signal, or other transducer(s).

(21) FIG. 3 shows a transponder diagram of another embodiment of the invention. A trigger unit 70 is connected to the power supply 20. In a simple embodiment, a trigger can be a simple rectifier, followed by a low pass filter and a comparator. By adding a trigger unit 70 in the electronic circuit 30, power can be saved by only providing power to the amplification and modulation unit 60 when an interrogating signal is detected.

(22) In one embodiment, the sequence generator 50 is also powered and activated only when an interrogating signal is present. By including a trigger unit 70, the acoustic transponder 10 can be in a sleep mode until woken up, thereby activating all circuits when a specific interrogation signal is detected. In this way, minimal power is drawn when the transponder is inactive.

(23) FIG. 4 shows yet another embodiment of the invention where one or more sensors 80 are included. By connecting sensors 80 to the sequence generator 50, the transponder 10 can convey sensor data, by letting the sequence generator 50 imprint a bit stream of received sensor data into to the interrogating signal that is amplified and modulated before being emitted. Different types of sensors may be used, e.g. sensors for measuring temperature, pressure, salinity etc.

(24) FIG. 5 shows a basic block diagram of an embodiment of the acoustic transponder 10 comprising a directional coupler 36. Instead of wiring the transducer 40, the extraction filter 32 and the suppression filter 34 together, a directional coupler (also called hybrid) can be used to give reduced coupling between the transmitted and the received signal.

(25) FIG. 6 shows an example of implementation of a digital solution of the acoustic transponder according to the invention.

(26) In this implementation, the extraction filter and the suppression filters as well as the modulator described above can is implemented in the digital domain. In practice, there will be amplifiers and filters before and after A/D and D/A converters. The figure shows anti-aliasing filters before the A/D converter and after the D/A converter. These may be implemented as low-pass filters, or bandpass filters. By using bandpass filters, it is possible to undersample the signal to minimize digital computation load.