Log-polar signal processing

Abstract

The invention relates to a method and an arrangement intended for radio communication systems and effective in digitalizing and subsequently processing numerically arbitrary radio signals. The signals are represented by composite (complex) vectors which have been subjected to disturbances in the system, such that information in the signals has been lost. This information is restored in its entirety when practising the present invention. For the purpose of solving this problem, the inventive digitalizing arrangement includes a multistage logarithmic amplifier chain (A) in which each stage is connected to a separate detector (D), the output signals of which are added in an adder. The adder output signals are then transmitted to a first A/D-converter (AD 1 ) for digitalizing and converting the amplitude components of the signal. At the same time, the undetected signal from the saturated output stage in the amplifier chain is transmitted to a second A/D-converter for digitalizing and converting the phase components of the signal. The digital values obtained on the outputs of the AD-converters (AD 1, AD 2 ) are applied to different inputs of a digital signal processor (MP) for numerical processing of the pairwise received digital values in a manner such as to restore the complete vector characteristic of the signal.

I claim:  
     
       1. A method for processing radio signals, that vary over a wide dynamic range, which comprises the steps of: 
       amplifying the radio signals in a plurality of serial stages;  
       detecting the output of each amplifying stage;  
       summing the detected outputs of each amplifying stage together to provide a signal proportional to the logarithm of the amplitudes of the radio signals;  
       generating signals proportional to the phase of the radio signals from the output of the last amplifying stage; and  
       processing the signals proportional to the logarithm of the amplitudes and the signals proportional to the phase of the radio signals, in order to generate restored digital signals representative of the radio signals.  
     
     
       2. A method according to claim  1  which further includes the step of delaying the detected output of each amplifying stage prior to their summation. 
     
     
       3. A method according to claim  1  which further includes the step of clipping the output of the last amplifying stage such that the output at the last amplifying stage appears as a square wave. 
     
     
       4. An apparatus for processing radio signals that vary over a wide dynamic range, which comprises: 
       means for amplifying the radio signals in a plurality of serial stages;  
       means for detecting the output of each amplified stage;  
       means for summing the detected outputs of said detecting means in order to provide a signal proportional to the logarithm of the amplitudes of the radio signals;  
       means for generating signals proportional to the phase of the radio signals from the output of the last stage of said amplifying means; and  
       processing means for processing the signals proportional to the logarithm of the amplitudes and the signals proportional to the phase of the radio signals, in order to provide restored digital signals representative of the radio signals.  
     
     
       5. An apparatus according to claim  4  which further includes means for clipping the output of the last amplifying stage such that the output of the last amplifying stage appears as a square wave. 
     
     
       6. An apparatus according to claim  4  which further includes an analog-to-digital converter for converting the signals proportional to the logarithm of the amplitudes to digital values. 
     
     
       7. An apparatus according to claim  6  which further includes an analog-to-digital converter for converting the signals proportional to the phase of the radio signals to digital values. 
     
     
       8. An apparatus according to claim  4  which further includes means for delaying the outputs of said detecting means prior to their application to said summing means. 
     
     
       9. An apparatus according to claim  8  which further includes an analog-to-digital converter for converting the signals proportional to the logarithm of the amplitudes to digital values. 
     
     
       10. An apparatus according to claim  9  which further includes an analog-to-digital converter for converting the signals proportional to the phase of the radio signals to digital values. 
     
     
       11. A method for processing radio signals, that vary over a wide dynamic range, which comprises the steps of: 
       amplifying the radio signals in a plurality of serial stages;  
       clipping the output of the last amplifying stage such that the output at the last amplifying stage appears as a square wave,  
       detecting the output of each amplifying stage;  
       summing the detected outputs of each amplifying stage together to provide a signal proportional to the logarithm of the amplitudes of the radio signals;  
       generating signals proportional to the phase of the radio signals from the output of the last amplifying stage, such that the generation of signals proportional to the phase is synchronous with the signal proportional to the logarithm of the amplitudes; and  
       processing the signals proportional to the logarithm of the amplitudes and the signals proportional to the phase of the radio signals, in order to generate restored digital signals representative of the radio signals.  
     
     
       12. A method for processing complex radio signals that vary over a wide dynamic range, comprising the steps of: 
       amplifying the radio signals in a plurality of sequentially saturating stages to produce a hardlimited output signal from the final stage;  
       detecting the output from each stage and summing the detected outputs to produce a log-amplitude value approximately proportional to the logarithm of an instantaneous amplitude of the complex radio signals;  
       converting the hardlimited output signal from the final amplifier stage to numerical values related to the cosine of the instantaneous phase and to the sine of the phase; and  
       processing the log-amplitude value and the cosine-related and sine-related values in order to produce numerical values representative of the real and imaginary parts of the complex radio signal. 
     
     
       13. A method according to claim  12  in which the converting of the hardlimited output signal includes using an analog-to-digital converter. 
     
     
       14. A method according to claim  12  in which the cosine-related and the sine-related values are digital values. 
     
     
       15. A method according to claim  12  in which the log-amplitude value is generated as a digital value. 
     
     
       16. A method according to claim  12  in which the processing of the hardlimited output signal includes quadrature sampling. 
     
     
       17. An apparatus for processing a complex radio signal that varies over a wide dynamic range, which comprises: 
       means for amplifying the radio signal in a plurality of sequentially saturating stages and producing a hardlimited output signal from the final stage;  
       means for detecting the output from each stage and producing detected output signals;  
       means for converting the detected output signals to produce a log-amplitude value approximately proportional to the logarithm of an instantaneous amplitude of the complex radio signal;  
       means for converting the hardlimited output signal from the final stage in order to extract values containing instantaneous phase information such that the extracted values are produced substantially synchronously with the log-amplitude value; and  
       processing means for processing the extracted values together with the log-amplitude value in order to provide digital values representative of the complex radio signal. 
     
     
       18. An apparatus in accordance with claim  17  in which the extracted values are related to the cosine and to the sine respectively of the instantaneous phase of the radio signal. 
     
     
       19. An apparatus in accordance with claim  17  in which the processing means computes an antilogarithm of the log-amplitude value. 
     
     
       20. An apparatus in accordance with claim  18  in which the processing means computes an antilogarithm of the log-amplitude value and mathematically combines it with the cosine-related and sine-related values. 
     
     
       21. An apparatus for processing a complex radio signal that varies over a wide dynamic range, which comprises: 
       means for amplifying the radio signal in a plurality of sequentially saturating stages and producing a hardlimited output signal from the final stage;  
       means for detecting the output from each stage and producing detected output signals;  
       first means for converting the detected output signals to produce a first log-amplitude value approximately proportional to the logarithm of an instantaneous signal amplitude of the complex radio signal;  
       second means for converting the hardlimited output signal from the final stage in order to extract values containing instantaneous phase information; and  
       processing means, responsive to said first and second converting means, for determining a second log-amplitude value representative of the instantaneous amplitude of the radio signal at the same instant the extracted values are representative of the instantaneous phase of the radio signal and for combining the determined second log-amplitude value with the extracted values in order to provide digital values representative of the complex radio signal. 
     
     
       22. An apparatus in accordance with claim  21  in which the extracted values are related to the cosine and the sine respectively of the instantaneous phase of the radio signal. 
     
     
       23. An apparatus in accordance with claim  21  in which the processing means computes an antilogarithm of the log-amplitude signal. 
     
     
       24. An apparatus in accordance with claim  22  in which the processing means computes an antilogarithm of the log-amplitude value and multiplies it with the cosine-related and sine-related values. 
     
     
       25. A method of processing a radio signal comprising: 
       amplifying said radio signal using a chain of progressively saturating amplifiers each including detectors in order to produce detected signals related to the logarithm of the signal amplitude of the radio signal and a saturated output signal from the last amplifier in the chain of amplifiers that preserves preserving phase information of the radio signal;  
       sampling and digitizing said detected signal and said saturated output signal using analog-to-digital converters in order to produce corresponding numerical sample values; and  
       numerically processing said numerical sample values in order to produce complex numerical samples representing said radio signal. 
     
     
       26. A method according to claim  25  in which the complex numerical samples are produced in cartesian representations having a real and imaginary part. 
     
     
       27. A method according to claim  25  in which the complex numerical samples are produced in polar representations having a radius and angle. 
     
     
       28. A method according to claim  27  in which the complex numerical samples in polar representations are subjected to a polar to cartesian transformation. 
     
     
       29. An apparatus for processing a radio signal comprising: 
       receiving means for converting said radio signal to a suitable intermediate frequency signal;  
       amplifying and detecting means, having a plurality of stages, for amplifying the intermediate frequency signal to produce a detected signal related to the amplitude of the intermediate frequency signal and to produce a saturated output signal from the last stage of the amplifying and detecting means;  
       analog-to-digital converting means for sampling and digitizing the detected output signal and the saturated signal to produce corresponding numerical samples; and  
       digital signal processing means to process the numerical samples in order to obtain complex numerical samples representative of the radio signal. 
     
     
       30. An apparatus according to claim  29  in which the complex numerical samples are produced in cartesian representations having a real and imaginary part. 
     
     
       31. An apparatus according to claim  29  in which the complex numerical samples are produced in polar representations having a radius and angle. 
     
     
       32. An apparatus according to claim  31  in which the complex numerical samples in polar representations are subjected to a polar to cartesian transformation.