Smart noise generator

• US 4,247,946 A
• Filed: 12/19/1979
• Issued: 01/27/1981
• Est. Priority Date: 12/19/1979
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: RCA Corporation (General Electric Company)
• Inventors: Mawhinney, Daniel D.
• Primary Examiner(s): Ng, Jin F.
• Application Number:
  US06/105,109
• Time in Patent Office: 405 Days
• Field of Search: 455/1, 455/264, 455/258, 455/263, 343/18 E, 331/1 R, 331/11, 331/14, 331/78
• US Class Current: 455/1
• CPC Class Codes: G01S 7/32 Shaping echo pulse signals; Deriving non-pulse signals from echo pulse signals

Abstract

A frequency memory system having a smart noise component is receptive of an RF burst signal of a given frequency and of relatively short duration for determining the frequency and storing a signal of amplitude indicative of the given frequency and for producing by means of a voltage controlled oscillator (VCO) a signal at the given frequency of relatively long duration. The stored signal and a signal for amplitude corresponding to the actual frequency produced by VCO are utilized to produce an error signal to correct any error in the frequency of the signal produced by the VCO relative to the given frequency. Since the VCO is not capable of immediately accurately tracking the input frequency, a smart noise generator produces a signal of random amplitude which is added to the error signal to cause the VCO to produce at least a frequency component of its output signal which is equal to that of the input RF burst signal.

Claims

1. A system for generating a relatively long duration output RF signal at the same frequency as a received relatively short duration input Rf signal having a leading edge and lasting at least until time T thereafter, comprising in combination:

first means responsive to said input signal for generating a first output signal of amplitude corresponding to the frequency of said input RF signal;

second means responsive to said first means first output signal for producing a first output signal corresponding to the amplitude of said first means first output signal until a time t after receipt by said first means of said input RF signal leading edge and for thereafter producing a second output signal corresponding to the amplitude of said first means first output signal at time t, where t≦

T;

third means responsive to said first and second signals produced by said second means for producing said output RF signal, the frequency of which is ideally identical to the frequency of said input RF signal but, due to system tolerance, is usually not identical thereto;

fourth means responsive to said output RF signal from said third means after time, t, for applying said output frequency signal, rather than said input frequency signal, to said first means for causing it to produce a second output signal the amplitude of which corresponds to the frequency of said output RF signal; and

error correcting means responsive to first means second output signal and second means second output signal for producing a difference signal and wherein said third means is responsive to said difference signal for correcting the frequency of said output RF signal to the frequency of said input RF signal.

2. The combination as set forth in claim 1, wherein said first means comprises a discriminator means responsive to said input RF signal for providing an output voltage signal, the amplitude of which corresponds to the frequency of said input signal.

3. The combination as set forth in claim 1, wherein said third means comprises an amplifier means coupled to receive signals from said second means and a voltage controlled oscillator coupled to said amplifier means for producing said output RF signal of frequency corresponding substantially to the voltage amplitude of input signal received at said amplifier means.

4. The combination as set forth in claim 1, wherein said error correcting means comprises a summing junction to which is applied the output signal from said first means and the output signal from said second means, said error correcting means also including an error amplifier responsive to the difference in amplitude of said signal supplied to said summing means for producing an error output signal, said error amplifier output signal being coupled to said third means in addition to said signals from said second means.

5. The combination as set forth in claim 1, further including means producing an alternating voltage signal of random period, and wherein said error correcting means is also responsive to said random period signal for producing said difference signal, said random period signal being of such amplitude to cause said error correcting means to produce said difference signal of such amplitude as to cause said third means to produce, after time t, said output RF signal having a frequency component equal to the frequency of said input RF signal.

6. The combination as set forth in claim 5, wherein said means producing said alternating voltage signal of random period comprises a noisy diode producing a white noise and an operational amplifier means for amplifying said white noise produced by said noisy diode.

7. The combination as set forth in claim 1 , wherein said RF input signal where a leading edge, and where said system further includes a timing means responsive to said leading edge of said input signal for producing a pulse at time t, thereafter and wherein said pulse at time t, is applied to said second means for causing it to produce said second output signal.

8. The combination as set forth in claim 7, wherein said fourth means comprises a normally opened switch means responsive to said pulse from said timing means for closing and wherein said output RF signal from said third means is coupled to one terminal of said normally opened switch means, said first means also comprising a limiter means coupled to receive said RF input signal and coupled to a second terminal of said switch means for receiving said output RF signal when said switch means is closed and for receiving said input RF signal when said switch means is opened.

9. The combination as set forth in claim 1, or 7, wherein said second means is a track and hold means which tracks said first means first output signal until said time t, and which thereafter hold the signal tracked at time t.

10. A system for generating a relatively long duration of output RF signal at the same frequency as a received relatively short duration input RF signal, having a leasing edge and lasting at least until time T, after said leading edge, comprising in combination:

first means responsive to said input signal for generating a first output signal of amplitude corresponding to the frequency of said input RF signal;

second means responsive to said first means first output signal for producing a first output signal corresponding to the amplitude of said first means first output signal until a time t after receipt by said first means of said input RF signal leading edge and for thereafter producing a second output signal corresponding to the amplitude of said first means first output signal at time t, where t≦

T;

third means responsive to said first and second signals produced by said second means for producing said output RF signal, the frequency of which is ideally identical to the frequency of said input RF signal, but which, due to system tolerance is usually not identical thereto;

fourth means responsive to said output RF signal from said third means after time t, for applying said output frequency signal, rather than said input frequency signal to said first means for causing it to produce a second output signal the amplitude of which corresponds to the frequency of said output RF signal;

fifth means producing alternating voltage signal of random period and given amplitude;

summing means responsive to said first means second output signal and second means second output signal and alternating voltage signal of random period for producing an error signal which is the difference of the first and second means output signals altered by the value of said random period signal; and

wherein said third means is also responsive to said error signal for producing said output RF signal, which, after some time, which is greater than time T, is identical to said input RF signal and which after time t, produces said output RF signal having a component value which is identical to the frequency of said input RF signal.