Coherent power combining via wavefront multiplexing on deep space spacecraft

Abstract

An apparatus includes a demultiplexing device, a bank of filters, a wavefront processor, and an optimizer. The demultiplexing device demultiplexes M data streams into N wavefront signals which include P pilot signals, N, M, and P being positive integers and N>M. The bank of filters filters the N wavefront signals using filter weights. The wavefront processor, having N input ports and N output ports, performs an N-to-N wavefront demultiplexing transform on the N wavefront signals at the N input ports and outputs N wavefront demultiplexed signals at the N output ports such that each of the N wavefront demultiplexed signals is a linear combination of the N wavefront signals. The N wavefront demultiplexed signals include P recovered pilot signals. The optimizer updates the filter weights using performance indices based on the P recovered pilot signals and known pilot signals corresponding to the P pilot signals.

1 . An apparatus comprising:
 a demultiplexing device configured to demultiplex M data streams into N wavefront signals, the N wavefront signals including P pilot signals, N, M, and P being positive integers and N>M;   a bank of filters configured to filter the N wavefront signals using filter weights;   a wavefront processor having N input ports and N output ports and configured to perform an N-to-N wavefront demultiplexing transform on the N wavefront signals at the N input ports and outputting N wavefront demultiplexed signals at the N output ports such that each of the N wavefront demultiplexed signals is a linear combination of the N wavefront signals, the N wavefront demultiplexed signals including P recovered pilot signals; and   an optimizer configured to update the filter weights using performance indices based on the P recovered pilot signals and known pilot signals corresponding to the P pilot signals.   
     
     
         2 . The apparatus of  claim 1  wherein the optimizer comprises:
 an optimizing processor configured to update the filter weights by calculating the cost function using the performance indices, determining gradients of the cost function with respect to the filter weights, and calculating new filter weights based on the gradients. 
 
     
     
         3 . The apparatus of  claim 1  further comprising:
 a redundancy remover configured to remove redundant signals from the demultiplexed M data streams to provide the N wavefront signals. 
 
     
     
         4 . The apparatus of  claim 1  further comprising:
 a time domain multiplexer configured to multiplex N-P wavefront demultiplexed signals without the P recovered pilot signals into a recovered data stream. 
 
     
     
         5 . The apparatus of  claim 1  wherein the bank of filters includes a finite impulse response (FIR) filter having the filter weights as FIR coefficients. 
     
     
         6 . The apparatus of  claim 1  wherein the M data streams are generated using a wavefront multiplexing transform. 
     
     
         7 . The apparatus of  claim 5  wherein the wavefront multiplexing transform is one of a Fast Fourier transform, a Hartley transform, a Hadamard transform, or a Walsh-Hadamard transform. 
     
     
         8 . The apparatus of  claim 6  wherein the wavefront demultiplexing transform is an inverse or complementary of the wavefront multiplexing transform. 
     
     
         9 . The apparatus of  claim 8  the wavefront demultiplexing transform is an inverse of one of a Fast Fourier transform, a Hartley transform, a Hadamard transform, or a Walsh-Hadamard transform. 
     
     
         10 . The apparatus of  claim 1  wherein the wavefront processor restores orthogonality of the N wavefront demultiplexed signals. 
     
     
         11 . A method comprising:
 demultiplexing M data streams into N wavefront signals, the N wavefront signals including P pilot signals, N, M, and P being positive integers and N>M;   filtering the N wavefront signals using filter weights;   performing an N-to-N wavefront demultiplexing transform on the N wavefront signals and outputting N wavefront demultiplexed signals such that each of the N wavefront demultiplexed signals is a linear combination of the N wavefront signals, the N wavefront demultiplexed signals including P recovered pilot signals; and   updating the filter weights using performance indices based on the P recovered pilot signals and known pilot signals corresponding to the P pilot signals.   
     
     
         12 . The method of  claim 11  wherein updating comprises:
 calculating the cost function using the performance indices; 
 determining gradients of the cost function with respect to the filter weights; and 
 calculating new filter weights based on the gradients. 
 
     
     
         13 . The method of  claim 11  further comprising:
 multiplexing N-P wavefront demultiplexed signals without the P recovered pilot signals into a recovered data stream. 
 
     
     
         14 . The method of  claim 11  wherein filtering comprises filtering using a finite impulse response (FIR) filter having the filter weights as FIR coefficients. 
     
     
         15 . The method of  claim 1  wherein the M data streams are generated using a wavefront multiplexing transform. 
     
     
         16 . The method of  claim 5  wherein the wavefront multiplexing transform is one of a Fast Fourier transform, a Hartley transform, a Hadamard transform, or a Walsh-Hadamard transform. 
     
     
         17 . The method of  claim 6  wherein the wavefront demultiplexing transform is an inverse or complementary of the wavefront multiplexing transform. 
     
     
         18 . A receiver system comprising:
 a receiving antenna configured to receive M receiving signals from M parallel subchannels, the M receiving signals corresponding to an original data stream;   a down converter to convert the M receiving signals to M baseband signals;   an analog-to-digital converter configured to convert the M baseband signals into M data streams; and   a data recover device configured to recover the original data stream from the M data streams, the data recover device comprising:
 a demultiplexing device configured to demultiplex the M data streams into N wavefront signals, the N signals including P pilot signals, N, M, and P being positive integers and N>M; 
 a bank of filters configured to filter the N wavefront signals using filter weights; 
 a wavefront processor having N input ports and N output ports and configured to perform an N-to-N wavefront demultiplexing transform on the N wavefront signals at the N input ports and outputting N wavefront demultiplexed signals at the N output ports such that each of the N wavefront demultiplexed signals is a linear combination of the N wavefront signals, the N wavefront demultiplexed signals including P recovered pilot signals; and 
 an optimizer configured to update the filter weights using performance indices based on the P recovered pilot signals and known pilot signals corresponding to the P pilot signals. 
   
     
     
         19 . The receiver system of  claim 19  wherein the optimizer comprises:
 an optimizing processor configured to update the filter weights by calculating the cost function using the performance indices, determining gradients of the cost function with respect to the filter weights, and calculating new filter weights based on the gradients. 
 
     
     
         20 . The receiver system of  claim 19  wherein the data recover device further comprises:
 a time domain multiplexer configured to multiplex N-P wavefront demultiplexed signals without the P recovered pilot signals into the recovered original data stream.