Method and apparatus for modulation synthesis

• US 3,890,620 A
• Filed: 01/14/1974
• Issued: 06/17/1975
• Est. Priority Date: 11/08/1971
• Status: Expired due to Term

• Current Assignee: Wilcox Electric Incorporated
• Original Assignee: Coulter J. Roland, Donald J. Toman
• Inventors: Toman, Donald J., Coulter, J. Roland
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Blum, T. M.
• Application Number:
  US05/430,272
• Time in Patent Office: 519 Days
• Field of Search: 343/107,18R,18M,109,1SA 332/9R,11R 325/39
• US Class Current: 342/413
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

Digital sample point values signifying various modulation levels required at successive points in time are stored in a digital memory and read out in timed sequence and applied to modify a carrier wave in a manner such as to be recognized as modulation by a receiver.

Claims

1. Apparatus for synthesizing the production of a modulated radio carrier wave comprising storage means for continuously storing the same group of digital values corresponding to a plurality of different sample points signifying various modulation levels required at successive points in time to suggest the presence of a modulation signal wave form, means for reading out said sample point values in timed sequence, a source of carrier waves, means for transferring and means for applying said point values to modify the carrier waves to produce a modified carrier which is recognizable by a receiver as a carrier modulated by a repetitive wave form modulation signal, said means for applying said point values to modify the carrier wave comprising a gating device operable to gate the carrier on and off for periods proportional to the sample point values to thereby establish a pulse duration modulated carrier signal, a plurality of antenna elements arranged in an array, and switching means operable in synchronism with said gating device to switch the carrier to different antenna elements in said array for the successive individual periods when the carrier is on to thereby provide a composite scanning beam signal from all of the elements of said array.

2. Apparatus as claimed in claim 1 wherein there is provided means for modifying the sample point values to insert additional signal information therein prior to application to said carrier wave modifying means, said means for modifying the sample point values being operable in synchronism with said switching means and said gating device to provide distinctive modulation signals for the combination of successive carrier wave pulses applied to each antenna element.

3. Apparatus as claimed in claim 2 wherein said sample point value modification means comprises means for storing and reading out a second plurality of different sample point values in step with the reading out of the first mentioned plurality of sample point values, and means for combining individual point values of the second plurality of sample point values with the individual point values of the first mentioned plurality of sample point values to provide the combined sample point values.

4. Apparatus as claimed in claim 2 wherein said modifying means comprises means for multiplying each sample point value by a scale factor.

5. Apparatus as claimed in claim 3 wherein said combining means comprises an adder.

6. Apparatus as claimed in claim 5 wherein said modifying means includes at least one multiplier for multiplying each member of said first mentioned plurality of sample point values by a first scale factor and for multiplying the corresponding member of the second plurality of sample point values by a second scale factor which is a complement of said first scale factor before addition of each p;

air of individual members of said first and second plurality of sample point values.

7. Apparatus as claimed in claim 1 including at least one register-counter means for storing each sample point value after it is read out of said storage means, said register-counter means being operable to count down to zero over a period determined by the digital sample point value stored therein commencing with a clock signal, said register-counter means being connected to control said gating device to provide a first gating stage during the counting down operation of said register-counter means and to provide a second gating state after the counting down operation has been completed to thereby gate the carrier on and off.