Abstract:
New apparatus comprise a comprises an optical fiber based RF signal train generator for storing transient RF pulses and regenerating the identical replicas for analysis. The apparatus further comprise comprises an RF receivers receiver to process one stored pulse with a reference to other another stored pulse. The present invention drastically increases our abilities to investigate acoustical, electromagnetic, and optical transient phenomena.

Description:
This application is a continuation-in-part of application Ser. No. 18,388 filed Feb.  17, 1993, which was refiled as Ser. No. 08/439,284 on May 11, 1995 now U.S. Pat. No. 5,955,983,  and a continuation-in-part of Ser. No. 877,419 filed May 1, 1992 now U.S. Pat. No. 5,294,930 and a continuation-in-part of Ser. No. 787,085 filed Nov. 4, 1991 now U.S. Pat. No. 5,296,860. 
    
    
     TECHNICAL FIELD OF INVENTION 
     This invention relates to an apparatus which utilize utilizes an optical fiber loop based RF signal train generator to store transient pulses and regenerate their identical replicas for analysis. The present invention drastically increases our abilities to investigate acoustical, electromagnetic, and optical transient phenomena. 
     BACKGROUND 
     Interferometer is a widely used instrument. The constituents of interferometers may vary, but they all comprise these essential elements: a source, a splitter, two paths, and a detection apparatus. The source may generate acoustical, electromagnetic, and light wave, which is split into two paths by the splitter. The detection apparatus compares waves from the two paths, and determine determines their variational differences. Interferometer is a powerful instrument, which is capable of probing micro, meso, and macro systems. A system under test may be the source, the splitter, or an external system inserted into an interferometer path. We can infer the physical characteristics of the system under test from the observed variational differences. 
     An interferometer with a continuous wave source requires both the interferometer and system under test to be stable and stationary. Any random and vibrational motion will blur the variational differences, and mask the physical characteristics of the system under test. An interferometer with a short-pulsed source will freeze a transient natural event. However, with a conventional interferometer we are not able to decipher completely the variational difference created by a single transient event. Multiple pulses and events are needed, thus the short pulse and the transient event have to be exactly and repeatedly reproduced. This may not be possible with all transient events. 
     Digitizing receiver is another widely used instrument. It comprises a radio frequency (RF) receiver and a digitizer. In a receiving process, the RF receiver first converts an RF signal to an intermediate frequency (IF) signal, and then to a video signal. A digitizer converts the analog video signal to a digital signal. The capability of a digitizer depends on its sampling rate. Digitizers with sampling rate of 200 MHz are commercially available. Digitizers with sampling rate of 1 GHz have been reported. Depending on the capability of a digitizer, the down conversion to a video signal may not be needed and a digitizer may directly digitize a an IF signal. A down conversion will filter away many intrinsic traits of a transient event. Most radar receivers have IF frequency of 60 MHz. More sophisticated RF receivers have IF frequency of 10 GHz to preserve the intrinsic traits of subnanosecond RF pulses. It is still impossible for a digitizing receiver to completely capture the intrinsic traits of a single RF pulse with frequency of 10 GHz and pulse width of 1 GHz. Multiple pulses and events are again needed. 
     In light of the above, there is a need in the art for a new apparatus which are is capable of capturing the intrinsic traits of and determining the variational differences created by a random, chaotic, turbulent, or transient phenomenon. Furthermore it will reveal the physical traits of a single transient event without instability blurring. An interferoceiver with RF signal train generator will fulfill the needs to capture transient traits and to overcome the blurring. The physical principle for the new interferoceiver to capture an a transient event is the same as that for optical fiber based radars with an RF signal train generator. 
     THEORY OF INVENTION 
     The conventional method, which rests on the available technology. As the technology evolves, we are able to decipher a single transient event completely. The technology is the optical fiber RF delay loop based RF signal train generator. The information concerns the delay loop and generator can be found in the parent patent applications. With their help, a radar is able to determine the range and Doppler shift of a target with a single radar pulse. We will give a brief discussion here on the RF signal train generation. 
     Let us assume the single input RF pulse to the loop has the form 
     
       
         A(t−t i ) Exp{+j ωt},   (1)  
       
     
     where ω is the circular frequency of the RF pulse with a pulse profile A (t-t i ) centered at the time t i . Experimentally we can not decipher the intrinsic characteristics of a short RF pulse. It is the limitation imposed by the sampling rate and Nyquist theorem. RF pulses are transient. Media were not available to record a transient RF: pulse faithfully for the examination at a later time. Since the experimental means did not exist for completely deciphering a short RF pulse, we had to rely on the alternative alternate methods. These methods are only useful to those short RF pulses which can be reproduced exactly by their respective sources. We then examine a portion of each reproduced pulse. The information from the reproduced pulses are is aggregated to complete the deciphering of a short RF pulse. A sample oscilloscope uses such a method to decipher a short RF pulse. 
     Now the optical fiber RF delay loop provides an alternative alternate method. The delay loop causes the pulse delay of the input RF pulse. The pulse train emerged from the optical fiber delay loop can be expressed as                  ∑     i   =   1     N            A        (     t   -     t   i       )          Exp        {       +   j                   ω                 t     }         ,           (   2   )                                
     where N is the number of pulses in the train, τ the time delay of the loop, and t i =i×τ denotes the time delay of a an RF pulse emerged from the storage loop after looping i times. The delay caused by an optical fiber is a dynamical delay. RF pulse in the emerging train replicates the input RF pulse. By examining the copies of its replicas, a short RF pulse can be completely deciphered and repeatedly examined. It is impossible with a conventional digitizing receiver or interferometer. 
     A reference pulse is required in deciphering an RF pulse. It plays two roles. These are the triggering in a digitizing receiver and the referencing in an interferometer. The triggering instructs the digitizer when to sample. The referencing provides an interferometer with a basis in evaluating what a transient phenomenon has affected the probing pulse. An additional optical fiber RF delay loop has to be introduced in yielding a reference pulse train. An RF signal train generator comprises two identical optical fiber RF delay loops, which will fulfill the needs. We then examine each copy of the RF pulse replicas with the help from a copy of the reference pulse replicas. 
     Pulsed signals may be acoustical, electromagnetic, and optical. These pulse signals in their respective receivers and interferometers will be eventually converted to the electromagnetic pulse signals. Hence, RF signal train generators can be coupled with acoustical, electromagnetic, and optical signals to investigate their respective phenomena. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention, which has a board functional capability, advantageously satisfy the above identified needs in the art. Embodiments of the present invention will provide an interferoceiver which is versatile and sophisticated. Such an interferoceiver will capture the intrinsic characteristics of a transient event without the blurring from its instability. In particular, embodiments of the present invention comprise optical fiber RF delay loops for storing short pulses, and reproducing their identical replicas. 
     In preferred embodiments of the present invention, the interferoceivers are equipped with an RF signal train generator, digitizing and intra pulse coherent processing subsystems. As a result, a new interferoceiver will be able to freeze a transient event, and will have the functional capabilities of determining the statistical distribution, which describes the instability of random, chaotic, turbulent, and transient phenomena. As those of ordinary skill in the art will readily appreciate, in the light of intra pulse coherence, the instability blurring associated with multiple pulses will no longer be a problem, and external interferences from other sources will be drastically reduced. 
     In other embodiments of the present invention, the RF signal train generator, digitizing and intra pulse coherent processing subsystems are directly added to conventional digitizers and interferometers to upgrade their functional capabilities as well as removing multiple pulse requirements for these instruments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     A complete understanding of the present invention may be gained by considering the following detailed description in conjunction with the accompanying drawings, in which: 
     FIG. 1 shows a block diagram of an optical fiber RF delay loop for use in fabricating embodiments of the present invention; 
     FIG. 1a shows a block diagram of a tapped optical fiber RF delay line or a set of optical fiber RF delay lines for use in fabricating embodiments of the present invention;  
     FIG. 2 shows a block diagram of an RF signal train generator for use in fabricating embodiments of the present invention; 
     FIG. 2a shows a block diagram of data flow from RF receiver to a medium for use in fabricating embodiments of the present invention;  
     FIG. 3 shows a block diagram of an interferoceiver for use in fabricating embodiments of the present invention; 
     FIG. 4 shows a block diagram of an interferoceiver with a system under test inserted into a path for use in fabricating embodiments of the present invention; 
     FIG. 5 shows a block diagram of an interferoceiver with a system under test as the splitter for use in fabricating embodiments of the present invention; 
     FIG. 6 shows a block diagram of some sources for use in fabricating embodiments of the present invention; 
     FIG. 7 shows a block diagram of some RF receiver functions for use in fabricating embodiments of the present invention.  
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a block diagram of an optical fiber RF delay loop  100  for use in fabricating embodiments of the present invention. This is the same optical fiber RF delay loop as in the parent patent applications of optical fiber based radars and optical RF stereo. As shown in FIG. 1, the optical RF signals through optical fiber  121  are applied as input to switchable coupler  120 . Switchable coupler  120  switches the optical RF signals from optical fiber  121  into optical fiber loop  110 . Isolator  140  assures the optical RF signals in optical fiber loop circulating only in one direction. As the optical RF signals circulate the optical fiber loop  110 , the strength of optical RF signals reduces. The reduction is compensated by in-line optical amplifier (OA)  130  to keep the optical RF signals circulating in the loop again and again until switchable coupler  120  is closed. A portion of optical RF signals is switched from optical fiber loop  110  to optical fiber  122  and the remainder of optical RF signals will still circulate in optical fiber loop  110 . The steps repeat again and again. The closing of loop switch  150  will quench the circulation of optical RF signals in optical fiber loop  110  before admitting any new arrivals of optical RF signals from optical fiber  121 . Switchable coupler  120 , in-line optical amplifier  130 , isolator  140  and loop switch  150  are well known to those of ordinary skill in the art. 
     FIG. 1a shows a block diagram of a tapped optical fiber RF delay line or a set of optical fiber RF delay lines for use in fabricating embodiments of the present invention. The optical RF signals through optical fiber  121  are applied as input to taps or splitter  1120 . Taps or splitter  1120  splits the optical RF signals and applies the split optical RF signals as input to optical fiber RF delay lines  11111 ,  11112 , . . . ,  1111 n. These delay lines have different lengths. Taps or combiner  1121  combines the optical RF signals from the optical fiber RF delay lines  11111 , 11112 , . . . ,  1111 n, and applies the combined optical RF signals as input to optical fiber  122 . Taps, splitter, and combiner are well known to those of ordinary skill in the art.  
     FIG. 2 shows a block diagram of an RF signal train generator  200  for use in fabricating embodiments of the present invention. This is the same RF signal train generator as in the parent patent application of optical fiber based radars. RF signal train generator  200  comprises two identical optical fiber RF delay loops according to the present invention. As shown in FIG. 2, two temporally aligned RF pulses  210  and  220  are applied as inputs to their respective optical fiber delay loops  230  and  240 . So as not to loose clarity, optical fiber RF up and down converters, and low noise amplifiers have not been depicted in FIG.  2 . Loops  230  and  240  are identical and operated in a same manner thus respectively producing two pulse trains  250  and  260 . 
     As those of ordinary skill in the art will readily appreciate, embodiments of the present invention may not comprise an optical fiber RF storage subsystem as in comparison with optical fiber based radars for temporal alignment of two input pulses. The path length difference of two paths from a source to the RF signal train generator usually is small and can be simply adjusted through conventional RF means, which are known to those of ordinary skill in the art. However, if the need arises, one may introduce an optical fiber RF storage subsystem as well. Embodiment of the optical fiber RF storage subsystem is described in the parent patent application of optical fiber based radars. Furthermore, one may double one of the optical fiber delay loop in the RF signal train generator as the optical fiber RF storage subsystem. 
     RF receiver (RFR)  30  uses direct digitizing and coherent receiving methods to process pulse trains  250  and  260  from RF signal train generator  200 . These methods are well known to those of ordinary skill in the art. The direct digitizing method uses one train as triggering pulses to instruct the digitizer to sample the respective pulses of the second train. The triggering is systematically delayed in sampling the sequential pulses of the second train. The direct digitizing method yields the intrinsic structure of the initial pulse, which generates the second pulse train. The coherent receiving method, based on the intra pulse coherence, uses the pulses of one train as reference to process variational differences of their respective pulses of the second train. The mechanism to achieve intra pulse coherence was proposed in the parent patent application of optical fiber based bistatic radar. The coherent receiving method yields the relative amplitudes and phases, or the relative frequency differences between RF pulses  210  and  220 . Furthermore, RFR  30  will correlate pulse trains  250  and  260  to achieve a precise determination of their variational differences. The manner in which RFR  30  processes RF pulse trains is well known to those of ordinary skill in the art. As those of ordinary skill in the art will readily appreciate, RF signal train generator  200  of the present invention virtually mimics multiple pulses for RFR  30  to decipher the information contained in RF pulses  210  and  220 . 
     As those of ordinary skill in the art will readily appreciate, embodiments other than the specific architecture shown in FIG. 2 may be fabricated to provide the RF signal train generator. The optical fiber may vary its electrical length under external controls as a variable delay line. The optical fiber RF delay loop may be replaced by a tapped optical fiber RF delay line or by a set of optical fiber RF delay lines, as shown in FIG. 1a. 
     FIG. 2a shows a block diagram of data flow from RF receiver to a medium for use in fabricating embodiments of the present invention. After processing, RF receiver  30  produces a data stream  301 . The data stream  301  is then sent to medium  302 . 
     FIG. 6 shows a block diagram of some sources for use in fabricating embodiments of the present invention. Source (   610   )  for an interferoceiver may be acoustical  (   601   ) , electromagnetic  (   602   ) , mechanical  (   603   ) , infrared  (   604   ) , optical  (   605   ) , nuclear  (   606   ) , or other types.   
     FIG. 7 shows a block diagram of some RF receiver functions for use in fabricating embodiments of the present invention. RF receiver (   30   )  for an interferoceiver has one or many capabilities including those of amplitude and phase measurements  (   31   ) , relative amplitude and phase determination  (   32   ) , frequency measurement  (   33   ) , relative frequency difference determination  (   34   ) , correlation  (   35   ) , and signal delay determination  (   36   ).  
     FIG. 3 shows a block diagram of an interferoceiver for use in fabricating embodiments of the present invention. As shown in FIG. 3 the interferoceiver is comprised of source  310 , splitter  320 , converters  323  and  324 , RF signal train generator  200 , and RF receiver  30 . Source  310 , splitter  320 , converters  323  and  324  are well known to those of ordinary skill in the art. 
     During an operation, source  310  generates acoustical, electromagnetic, or optical signals for transit along path  311 . Splitter  320  uses the signals from path  311  as input and outputs two split signals. Furthermore, splitter  320  applies two split signals to two paths  321  and  322  for transit to converters  323  and  324 . Converters  323  and  324  then use the signals from paths  321  and  322  as inputs and convert them respectively to optical RF signals. Converters  323  and  324  may simply pass through these signals, if conversions are not needed. Converters  323  and  324  further apply optical RF signals respectively from paths  321  and  322  to optical fiber paths  325  and  326  for transit to RF signal train generator  200 . RF signal train generator  200  uses optical RF signals as input and outputs two pulse trains with respective to optical RF signals from paths  325  and  326 . RF signal train generator  200  further applies two pulse trains respectively to optical fiber paths  327  and  328  for transit to RFR  30 . RFR  30  uses pulse trains from optical fiber paths  327  and  328  as inputs to process these two pulse trains. 
     RFR  30  may further comprise phase shifters and delay lines for processing transient signals from source  310 . Furthermore, as is well known to those of ordinary skill in the art, RFR  30  will yield the spectrum of the signals, transient and intrinsic characteristics of source  310 , and turbulence characteristics of the media surrounding source  310 . 
     As those of ordinary skill in the art will readily appreciate, embodiment of interferoceiver  300  will leads to investigation of many transient and nonrepeatable signals in acoustics, electromagnetism, and optics. Those signals in acoustics are the blasts, explosions, thunders, etc . . . . Those signals in electromagnetism are electromagnetic pulses from lightning, violent electromagnetic discharge, electromagnetic pulse of opportunity, electromagnetic pulses emitted by nuclear blasts and celestial objects, etc . . . . Those signals in optics are the lights emitted by atoms and molecules in a turbulent media of burning, discharge, plasma, lightning, etc . . . . Furthermore, all the above mentioned signals are well know to those of ordinary skill in the art. 
     FIG. 4 shows a block diagram of an interferoceiver with a system under test inserted into a path for use in fabricating embodiments of the present invention. As shown in FIG. 4, interferoceiver  400  is comprised of source  410 , splitter  420 , converters  423  and  424 , RF signal train generator  200 , and RF receiver  30 . Source  410 , splitter  420 , system under test  430 , converters  423  and  424  are well known to those of ordinary skill in the art. 
     During an operation, source  410  generates acoustical, electromagnetic, or optical signals for transit along path  411 . Splitter  420  uses the signals from path  411  as input and outputs two split signals. Furthermore, splitter  420  applies two split signals to two paths  421  and  422  for transit to converters  423  and  325 . Signal of path  422  transits through system under test  430 . Intrinsic charateristics of system under test  430  is random, chaotic, turbulent, or transient. As those of ordinary skill in the art will readily appreciate that signal of path  422  will interact with system under test and be tainted with the intrinsic characteristics of system under test  430  after the transit. Then converters  423  and  424  use the signals from paths  421  and  422  as inputs and convert them respectively to optical RF signals. Converters  423  and  424  may simply pass through these signals, if conversions are not needed. Converters  423  and  424  further apply optical RF signals respectively from paths  421  and  422  to optical fiber paths  425  and  426  for transit to RF signal train generator  200 . RF signal train generator  200  uses optical RF signals as input and outputs two pulse trains with respect to optical RF signals from paths  425  and  426 . RF signal train generator  200  further applies two pulse trains respectively to optical fiber paths  427  and  428  for transit to RFR  30 . RFR  30  uses pulse trains from optical fiber paths  427  and  428  as inputs to process signal train from path  428  by using signal train from path  427  as a reference. As is well known to those of ordinary skill in the art, the reference signals from splitter  420  through path  421 , converter  423 , path  425 , RF signal train generator  200 , path  427  to RFR  30  are protected from external contamination and interference. 
     As those of ordinary skill in the art will readily appreciate, embodiment of interferoceiver  400  is well suited for investigating random, chaotic, turbulent, or transient features of emitting source  410  and system under test  430 . The observed intrinsic traits and variational differences contain information on both emitting source  410  and system under test  430 . With a known and pulsed source  410 , the processing of signal train from fiber optical path  428  by RFR  30  yields the intrinsic characteristics of the random, chaotic, turbulent, or transient traits within system under test  430 . As those of ordinary skill in the art will further appreciate, a coincident circuit may be needed to coordinate the source pulse with a transient event from system under test  430 . Furthermore, RFR  30  will separate stable traits of system under test  430  from its random, chaotic, turbulent, or transient features. The method of separation is well known to those of ordinary skill in the art. 
     As those of ordinary skill in the art will readily appreciate, embodiment of interferoceiver  400  with a pulsed ultrasonic source  410  will lead to diffraction tomography for unstable systems. An unstable motion leads to Doppler shift disturbances in diffraction fields and tomographic image blurring. Embodiment of interferoceiver  400  will further lead to ultrasonic imaging of unstable objects and of fetus. As it is well known to those of ordinary skill in the art, RFR  30  through Fourier transformation and moving center correction will remove Doppler shift disturbances and sharp ultrasonic images of these systems. 
     As those of ordinary skill in the art will appreciate, embodiment of interferoceiver  400  with a pulsed electromagnetic source  410  will use solid means of coaxial cables and wave guides to transit its electromagnetic signals. For example, a single pulse from the pulsed electromagnetic source  410  will lead to the determination of location and speed for a fly in a transverse electromagnetic cell. As is well known to those of ordinary skill in the art, a conventional methods will only able to determine the location of a fly at rest from a single electromagnetic pulse. 
     As those of ordinary skill in the art will readily appreciate, embodiment of interferoceiver  400  may use a an electromagnetic pulse from lightning as a source and cloud layers as system under test  430 . RFR then will provide a detailed information concerning the structures of these layers. 
     As those of ordinary skill in the art will appreciate, embodiment of interferoceiver  400  with a continuous wave (CW) laser source  410  and a an electromagnetic pulse sensor as system under test  430  will lead to the capture of a single electromagnetic event. Furthermore, RFR  30  will provide a detailed information concerning transient traits and electromagnetic spectrum of the event. 
     As those of ordinary skill in the art will further appreciate, embodiment of interferoceiver  400  with a pulsed laser source  410  will lead to light scatterings by atoms, molecules, microorganisms, medium fluctuations, plasmas, and particles suspended in chaotic media, and many others. As is well known to those of ordinary skill in the art, the scattered lights are affected by the initial positions and velocities of micro objects and statistical properties of media. As is well known to those of ordinary skill in the art, motion of micro objects and turbulence of media will lead to Doppler frequency shifts in scattered lights. As those of ordinary skill in the art will appreciate, RFR  30  through Fourier transformation will reveal the Doppler spectra associated with the motion and turbulence, and their statistical distributions. As those of ordinary skill in the art will appreciate, embodiment of interferoceiver  400  will provide a much better tool than conventional methods in revealing intrinsic characteristics of atoms, molecules, microorganisms, medium fluctuations, plasmas, and particles suspended in chaotic media, and many others. 
     As those of ordinary skill in the art readily appreciate, embodiment of interferoceiver  400  with a pulsed laser source  410  will lead to lidars and laser velocimeters. Conventional lidars, which are based on pulsed lasers, only measure the ranges of reflecting objects. Conventional laser velocimeters, which are based on CW lasers, only measure the Doppler shifts from seeded particles. Lidars and laser velocimeters of the present invention, with a help of optical fiber RF storage subsystems, will have both the ranging and Doppler capabilities. As those of ordinary skill in the art will further appreciate, the distinction between lidars and laser velocimeters disappears in the teaching of the present invention. With a subnanosecond pulse source, we will be able to locate constituents in a large reflecting assembly and measure their individual Doppler shift frequencies. As those of ordinary skill in the art will readily appreciate, the teachings from the parent patent applications of optical fiber based bistatic radar and optical RF stereo will lead to the embodiments for fabricating optical fiber based bistatic lidar and optical light stereo. 
     As those of ordinary skill in the art will further appreciate, the incident and scattered laser pulses may be unsuitable for direct feeding to optical fibers. A second laser can be deployed to down convert the incident and scattered laser pulses to RF signals, then with the help of optical fiber RF converters to up convert the RF signals to optical RF signals for transit through optical fibers to RF signal train generator. The processes of down and up conversions of laser pulses are well known to those of ordinary skill in the art. 
     FIG. 5 shows a block diagram of an interferoceiver with a system under test as the splitter for use in fabricating embodiments of the present invention. As shown in FIG. 5 interferoceiver  500  is comprised of source  510 , system under test  530 , converters  523  and  524 , RF signal train generator  200 , and RF receiver  30 . Source  510 , converters  523  and  524  are well known to those of ordinary skill in the art. 
     During an operation, source  510  generates acoustical, electromagnetic, or optical signals for transit along path  511 . System under test  530  uses the signals from path  511  as input, interacts with the signals, and outputs two split signals. Furthermore, system under test  530  applies two split signals to two paths  521  and  522  for transit to converters  523  and  524 . Then converters  523  and  524  use the signals from paths  521  and  522  as inputs and convert them respectively to optical RF signals. Converters  523  and  524  may simply pass through these signals, if conversions are not needed. Converters  523  and  524  further apply optical RF signals respectively from paths  521  and  522  to optical fiber paths  525  and  526  for transit to RF signal train generator  200 . RF signal train generator  200  uses optical RF signals as input and outputs two pulse trains with respective to optical RF signals from paths  525  and  526 . RF signal train generator  200  further applies two pulse trains respectively to optical fiber paths  527  and  528  for transit to RFR  30 . RFR  30  uses pulse trains from optical fiber paths  527  and  528  as inputs to process signal train from one path by using signal train from the other path as reference. 
     As those of ordinary skill in the art will appreciate, for example, embodiment of interferoceiver  500  with a pulsed laser source  510  will lead to the correlation of scattered lights in a light scattering process. The correlation yields the Doppler shift difference between two scattered lights. The mechanism of Doppler shift difference determination was proposed in the parent patent application of optical RF stereo. RFR  30  through Fourier transformation will reveal the spectra of the Doppler shift difference associated with the motion of micro objects and turbulence of media, and their statistical distributions. 
     ADVANTAGES AND OBJECTIVES 
     Embodiments of the present invention will provide advanced means to upgrade conventional digitizing receivers and interferometers than those furnished by the prior art. As those of ordinary skill in the art will further appreciate, embodiments of the present invention provide added upgrades to the existing digitizing receivers and interferometers without modification, which in turn will be more cost effective and will not interrupt their normal operation. 
     Embodiments of the present invention will enhance the functional diversities of conventional digitizing receivers and interferometers. In addition, the use of RF signal train generators makes it possible for digitizing receivers and interferometers to completely decipher a single transient event without instability blurring. Furthermore, embodiments of the present invention enable digitizing receivers and interferometers to determine intrinsic traits and Doppler spectrum of a single RF pulse. 
     Embodiments of the present invention will be able to reveal many hidden mechanisms governing many statistical phenomena. For instance, Doppler spectra of a chaotic medium and a turbulent flow could not be directly observed. Statistical properties of the Doppler spectra now can be systematically investigated. As those of ordinary skill in the art will appreciate, embodiments of the present invention will lead to better understandings of the chaotic media and turbulent flows. 
     As those of ordinary skill in the art will readily appreciate, averaging with respect to multiple pulses will smear many critical information concerning the system under test. Embodiments of the present invention use a single pulse rather than multiple repetitive pulses. The embodiment will make digitizing receivers and interferometers more versatile and sophisticated in exposing many critical information. As those of ordinary skill in the art will still further appreciate, embodiments of the present invention will lead to better understandings of random, chaotic, turbulent, or transient phenomena. 
     Embodiments of the present invention will be able to sharpen ultrasonic images. Furthermore, embodiments of the present invention will be able to separate the images of stationary constituents from that of moving constituents. As those of ordinary skill in the art will equally appreciate, optical fiber based radars will also sharpen synthetic aperture radar (SAR) images, and separate SAR images of stationary constituents from that of moving constituents. 
     Embodiments of the present invention will be able to reveal intrinsic traits of an active system. Intrinsic traits of an active system is are inherited, like imperfection in a diamond. As those of ordinary skill in the art will equally appreciate, optical fiber based radars and passive RF systems will provide excellent means in revealing the unintended modulation on pulse by active and passive objects. 
     Embodiments of the present invention will be advantageous to disclose internal constituents of a system and to reveal their characteristics. As those of ordinary skill in the art will equally appreciate, optical fiber based radars and passive RF system systems possess excellent means in suppression of clutter returns and of multiple path interferences. 
     Embodiments of the present invention, as shown in FIG. 2a, will lead to more effective means in deciphering a transient event than a fast digitizer under development or a group of parallel digitizers. A fast digitizer creates a massive data stream in a very short time interval. It is difficult for a medium to receive such a data stream. 
     Embodiments of the present invention will be advantageous in destructive testings, for example, automobile collision tests. Transient signals from various sensors will be thoroughly analyzed by interferoceivers. Embodiments of the present invention will provide better understandings as well as reducing the costs in destructive tests. 
     Quantum mechanics is a mechanics of coherent. Many interesting coherent phenomena implicated by Einstein, Podolsky, and Rosen paradox are still waiting for us to discover. Embodiments of the present invention will provide us new tools for us to discover these interesting phenomena. 
     SUMMARY, RAMIFICATIONS, AND SCOPE 
     Those skilled in the art readily recognize that embodiments of the present invention may be made without departing from its teachings. For example, the interferoceivers may have many designs as well as different variations. The source of an interferoceiver may play the role of a splitter as well. Two signals at different angle perspectives from a source are sent directly to the RF signal train generator. An interferoceiver may compare two sequential events from a source with the help from an optical fiber RF storage subsystem to temporally align these two events. Such a comparison leads to inter pulse coherence. The mechanism to achieve inter pulse coherence was proposed in the parent patent application of optical fiber based radars. Thus the scope of the invention should be determined by appended claims and their legal equivalent, rather by the examples presented here.