Method and system for propagation time measurement and calibration using mutual coupling in a radio frequency transmit/receive system

Abstract

A method and system use the mutual coupling property of multiple antenna elements for measuring differences in propagation time among various signal paths involving antenna elements in a radio frequency transmit/receive system. The method and system alleviate the need for external test equipment by using the same hardware used in standard operation of the transmit/receive system for performing propagation time measurement through the generation, mutual coupling, and acquisition of a specially selected reference signal. In an embodiment involving calibration of various signal paths to realize matched propagation times, the signal energy returned through these various paths during standard system operation arrives for acquisition more closely coincident in time, increasing the instantaneous bandwidth of the system.

1 . A method for measuring aspects of propagation times among various transmitting or receiving signal paths in a radio frequency transmit/receive system, comprising:
 generating a radio frequency reference signal;   transmitting the reference signal through a transmit side comprising at least one transmitting signal path comprising an antenna radiating element, which transmitting signal path and antenna radiating element are also usable for transmitting an operational signal;   receiving the reference signal through a receive side comprising at least one receiving signal path comprising an antenna receiving element, which receiving signal path and antenna receiving element are also usable for receiving an operational signal;   propagating the reference signal through a mutual coupling field from at least one said antenna radiating element to at least one said antenna receiving element;   wherein at least one of the transmit side or the receive side comprises a plurality of said transmitting signal paths or said receiving signal paths, respectively, as subject signal paths; and   processing the received reference signal to determine at least one characteristic of signal propagation time in relation to at least one of the subject signal paths.   
     
     
         2 . The method of  claim 1  wherein:
 the receive side comprises the plurality of receiving signal paths as the subject signal paths; 
 propagating the reference signal comprises propagating the reference signal from at least one antenna radiating element to at least two antenna receiving elements; and 
 at least two antenna receiving elements are disposed substantially along an equipotential surface of a mutual coupling field of at least one antenna radiating element. 
 
     
     
         3 . The method of  claim 1  wherein:
 the transmit side comprises the plurality of transmitting signal paths as the subject signal paths; 
 propagating the reference signal comprises propagating the reference signal from at least two antenna radiating elements to at least one antenna receiving element; and 
 an antenna receiving element is disposed at a point of substantially equipotential mutual coupling with respect to respective mutual coupling fields of at least two antenna radiating elements. 
 
     
     
         4 . The method of  claim 1 , wherein said processing comprises counting elapsed time. 
     
     
         5 . The method of  claim 1 , wherein said processing comprises ascertaining at least one component related to at least one heterodyned product of at least one reference signal instance. 
     
     
         6 . The method of  claim 1 , wherein the at least one characteristic comprises the absolute propagation time of a signal through at least one of the subject signal paths. 
     
     
         7 . The method of  claim 1 , wherein the at least one characteristic comprises the relative difference in signal propagation time between at least two of the subject signal paths. 
     
     
         8 . The method of  claim 1 , further comprising mixing a reference signal instance propagated through at least one of the subject signal paths with at least a reference signal instance fed from a generator of the reference signal. 
     
     
         9 . The method of  claim 1 , further comprising mixing a reference signal instance propagated through at least one of the subject signal paths with at least one reference signal instance propagated through another of the subject signal paths. 
     
     
         10 . The method of  claim 1 , wherein the reference signal comprises pulse compression modulation. 
     
     
         11 . The method of  claim 1 , further comprising adjusting propagation time of a signal through at least one of the subject signal paths based on a determination of at least one characteristic of propagation time of a signal in relation to at least one of the subject signal paths. 
     
     
         12 . The method of  claim 11 , wherein adjusting propagation time further comprises making one or more additional adjustments to the propagation time of a signal through at least one of the subject signal paths subsequent to a first adjustment and based on an additional one or more determinations of at least one characteristic of propagation time of a signal in relation to at least one of the subject signal paths made subsequent to a first determination. 
     
     
         13 . The method of  claim 11 , wherein the adjusting propagation time causes an instance of a signal propagating through one of the subject signal paths to complete its propagation through the system's signal path for said instance at substantially the same time as a signal instance propagating through another of the subject signal paths completes its propagation through the system's signal path for such other instance. 
     
     
         14 . A radio frequency transmit/receive system, comprising:
 an exciter capable of producing a radio frequency reference signal;   a transmit side comprising at least one transmitting signal path comprising an antenna radiating element, which transmitting signal path and antenna radiating element are usable for transmitting operational signals;   a receive side comprising at least one receiving signal path comprising an antenna receiving element, which receiving signal path and antenna receiving element are usable for receiving operational signals;   wherein at least one of the transmit side or the receive side comprises a plurality of said transmitting signal paths or said receiving signal paths, respectively, as subject signal paths, and wherein at least one antenna receiving element is disposed in proximity to at least one antenna radiating element permitting mutual coupling;   a signal receiver capable of acquiring a signal; and   analysis circuitry configured to determine based on a reference signal received from mutual coupling at least one characteristic of signal propagation time in relation to at least one of the subject signal paths.   
     
     
         15 . The system of  claim 14 , wherein the receive side comprises the plurality of receiving signal paths as the subject signal paths, and at least two antenna receiving elements are disposed substantially along an equipotential surface of a mutual coupling field of at least one antenna radiating element. 
     
     
         16 . The system of  claim 14 , wherein the transmit side comprises the plurality of transmitting signal paths as the subject signal paths, and an antenna receiving element is disposed at a point of substantially equipotential mutual coupling with respect to respective mutual coupling fields of at least two antenna radiating elements. 
     
     
         17 . The system of  claim 14 , wherein the analysis circuitry is configured to determine absolute propagation time through at least one of the subject signal paths. 
     
     
         18 . The system of  claim 14 , wherein the analysis circuitry is configured to determine relative difference in propagation times between at least two of the subject signal paths. 
     
     
         19 . The system of  claim 14 , further comprising a signal mixer disposed to mix a reference signal instance propagated through at least one of the subject signal paths with at least a reference signal instance propagated through another at least one of the subject signal paths. 
     
     
         20 . The system of  claim 14 , further comprising a signal mixer disposed to mix a reference signal instance propagated through at least one of the subject signal paths with at least a reference signal instance fed from the exciter. 
     
     
         21 . The system of  claim 14 , further comprising a propagation time adjustment control in communication with the analysis circuitry and also in communication with at least one propagation time adjustment mechanism disposed in a subject signal path, and capable of adjusting a propagation time of a signal through at least one subject signal path.