Acoustic telemetry system using passband equalization

Abstract

An embodiment includes a method comprising receiving an acoustic signal that is modulated along a jointed tubing. The method also includes performing equalization over a passband of the acoustic signal to generate an equalized signal.

1 . A method comprising: 
 receiving an acoustic signal that is modulated along a jointed tubing; and    performing equalization over a passband of the acoustic signal to generate an equalized signal.    
   
   
       2 . The method of  claim 1 , wherein receiving the acoustic signal that is modulated along the jointed tubing comprises receiving the acoustic signal having multiple passbands, wherein one of the multiple passbands includes more than one symbol.  
   
   
       3 . The method of  claim 2 , wherein receiving the acoustic signal that is modulated along the jointed tubing comprises receiving an acoustic signal wherein a first symbol in the one of the multiple passbands is modulated along the jointed tubing based on a first modulation operation that is different from a second modulation operation used to modulate a second symbol in the one of the multiple passbands.  
   
   
       4 . The method of  claim 1 , further comprising: 
 receiving a swept frequency signal;    performing a Fourier transform of the swept frequency signal; and    selecting the passband based on gain and phase versus frequency characteristics.    
   
   
       5 . The method of  claim 4 , further comprising determining the equalization over the passband of the acoustic signal.  
   
   
       6 . The method of  claim 5 , wherein determining the equalization over the passband of the acoustic signal comprises: 
 determining an impulse response in the passband based on the gain and the phase versus the frequency characteristic over the passband of the acoustic signal; and    determining initial coefficients of the equalization of the passband of the acoustic signal.    
   
   
       7 . A method comprising: 
 receiving an acoustic signal along a jointed tubing, wherein the acoustic signal includes multiple passbands that are caused by joints in the jointed tubing; and    equalizing each of the multiple passbands within the acoustic signal, independent of equalizing of other of the multiple passbands, to generate an approximately undistorted signal.    
   
   
       8 . The method of  claim 7 , wherein the multiple passbands are non-overlapping.  
   
   
       9 . The method of  claim 7 , further comprising demodulating the approximately undistorted signal to generate a demodulated signal.  
   
   
       10 . The method of  claim 9 , further comprising detecting one or more symbols within one or more of the multiple passbands of the demodulated signal.  
   
   
       11 . The method of  claim 9 , wherein demodulating the approximately undistorted signal comprises demodulating one of the multiple passbands using at least two different types of demodulations.  
   
   
       12 . The method of  claim 7 , wherein receiving the acoustic signal comprises receiving the acoustic signal having more than one symbol in one of the multiple passbands.  
   
   
       13 . A method comprising: 
 receiving data;    encoding the data into a number of symbols; and    modulating, in a channel, the number of symbols into at least one passband of an acoustic signal, wherein the at least one passband is caused by the channel.    
   
   
       14 . The method of  claim 13 , wherein modulating the number of symbols into at least one passband of the channel comprises modulating the number of symbols into at least one passband along a jointed tubing.  
   
   
       15 . The method of  claim 14 , wherein modulating the number of symbols into at least one passband along the jointed tubing comprises modulating the number of symbols into at least one passband, which is caused by at least one joint in the jointed tubing, along the jointed tubing.  
   
   
       16 . The method of  claim 13 , wherein modulating the number of symbols into the at least one passband comprises: 
 modulating, based on a first type of modulation, a first symbol of the number of symbols into a first passband of the at least one passband; and    modulating, based on a second type of modulation, a second symbol of the number of symbols into the first passband of the at least one passband.    
   
   
       17 . An apparatus comprising: 
 a passband equalizer to receive an acoustic signal that is to be modulated along a channel, wherein the acoustic signal includes one or more passbands caused by a characteristic of the channel, the passband equalizer to equalize the one or more passbands.    
   
   
       18 . The apparatus of  claim 17 , wherein the channel includes a jointed tubing for downhole drilling operations.  
   
   
       19 . The apparatus of  claim 18 , wherein the characteristic of the channel includes a characteristic of one or more joints of the jointed tubing.  
   
   
       20 . The apparatus of  claim 17 , wherein the passband equalizer is to equalize the one or more passbands independent of equalization of other of the one or more passbands.  
   
   
       21 . The apparatus of  claim 17 , wherein the passband equalizer is to generate an approximately undistorted signal, wherein the apparatus further comprises a demodulator to receive the approximately undistorted signal and to generate a demodulated signal.  
   
   
       22 . The apparatus of  claim 21 , further comprising a data detector to recover one or more symbols in one or more passbands from the demodulated signal.  
   
   
       23 . The apparatus of  claim 21 , wherein the demodulator is to demodulate the approximately undistorted signal based on at least two different types of demodulations.  
   
   
       24 . The apparatus of  claim 23 , wherein the at least two different types of demodulations are selected from the group consisting of a quadrature amplitude demodulation, a multi-pulse block correlation demodulation, a frequency shift key demodulation and a phase shift key demodulation.  
   
   
       25 . The apparatus of  claim 17 , wherein the acoustic signal includes more than one symbol in one of the one or more multiple passbands.  
   
   
       26 . An apparatus comprising: 
 a passband encoder to encode the data into a number of symbols; and    a modulator to modulate, along a jointed tubing, the number of symbols into at least one passband of an acoustic signal, wherein the at least one passband is caused by at least one joint in the jointed tubing.    
   
   
       27 . The apparatus of  claim 26 , wherein the modulator is to modulate a first symbol of the number of symbols in a first passband of the at least one passband, the modulator to modulate a second symbol of the number of symbols in a second passband of the at least one passband.  
   
   
       28 . The apparatus of  claim 27 , wherein the modulator is to modulate the first symbol in the first passband based on a first type of modulation, the modulator to modulate the second symbol in the second passband based on a second type of modulation, wherein the first type of modulation is different from the second type of modulation.  
   
   
       29 . The apparatus of  claim 28 , wherein the first type of modulation and the second type of modulation are selected from the group consisting of a quadrature amplitude demodulation, a multi-pulse block correlation demodulation, a frequency shift key demodulation and a phase shift key demodulation.  
   
   
       30 . The apparatus of  claim 26 , wherein the modulator is to modulate a first symbol and a second symbol of the number of symbols in a single passband of the at least one passband.  
   
   
       31 . The apparatus of  claim 30 , wherein the modulator is to modulate the first symbol based on a first type of modulation, the modulator to modulate the second symbol based on a second type of modulation, wherein the first type of modulation is different from the second type of modulation.  
   
   
       32 . A system comprising: 
 a jointed pipe;    a modulator to modulate at least one symbol in at least one passband of an acoustic signal along the jointed pipe, wherein the at least one passband is caused by a characteristic of the jointed pipe; and    a passband equalizer to receive the acoustic signal and to equalize the at least one passband.    
   
   
       33 . The system of  claim 32 , wherein the characteristic of the jointed pipe includes a characteristic of at least one joint in the jointed pipe.  
   
   
       34 . The system of  claim 32 , wherein the passband equalizer is to equalize the at least one passband independent of equalization of other of the at least one passband.  
   
   
       35 . The system of  claim 32 , wherein the passband equalizer is to generate an approximately undistorted signal, wherein the system further comprises a demodulator to receive the approximately undistorted signal and to generate a demodulated signal.  
   
   
       36 . The system of  claim 35 , wherein the modulator is to modulate a first symbol of the at least one symbol based on a first type of modulation and is to modulate a second symbol of the at least one symbol based on a second type of modulation, wherein the first type of modulation is different from the second type of modulation.  
   
   
       37 . The system of  claim 32 , wherein the acoustic signal includes more than one symbol of the at least one symbol in one of the at least one passband.  
   
   
       38 . The system of  claim 32 , wherein the at least one passband includes two or more passbands, wherein the two or more passbands are non-overlapping.  
   
   
       39 . A machine-readable medium that provides instructions, which when executed by a machine, cause said machine to perform operations comprising: 
 receiving an acoustic signal that is modulated along a jointed tubing; and    performing equalization over a passband of the acoustic signal to generate an equalized signal.    
   
   
       40 . The machine-readable medium of  claim 39 , wherein receiving the acoustic signal that is modulated along the jointed tubing comprises receiving the acoustic signal having multiple passbands, wherein one of the multiple passbands includes more than one symbol.