Multichannel frequency and phase variable radio frequency simulator

• US 5,598,437 A
• Filed: 07/16/1993
• Issued: 01/28/1997
• Est. Priority Date: 07/16/1993
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated
• Inventors: Gourse, Stanley J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US08/092,610
• Time in Patent Office: 1,292 Days
• Field of Search: 375/67.52, 364/718, 364/721, 328/14, 328/63, 328/155, 332/16 R, 332/117, 332/144, 307/262, 307/269, 327/106
• US Class Current: 375/308
• CPC Class Codes: H04L 27/2039 using microwave technology
• CPC Class Codes: H04L 27/2092 with digital generation of the modulated carrier (does not include the modulation of a digitally generated carrier)

Abstract

A multichannel frequency phase variable signal source is described having particular application in the simulation of an emitter environment for testing interferometer receivers. An improved direct digital frequency synthesizer produces phase information for initiating the operation of a related frequency synthesizer at a different phase point from those of the remainder of the synthesizers forming the multi channel source. An improved direct digital frequency synthesizer is described for varying this phase information.

Claims

1. A multi-output frequency and phase variable signal source having selectively variable phase relationships between outputs for simulating a complex wavefront, comprising:

a plurality of first frequency synthesizers each operating at the same output frequency, and

a plurality of second direct digital frequency synthesizers, each of which supplies selectively variable phase shift information to a respective one of said first frequency synthesizers for initiating its operation at a phase differing from that of the others of said first frequency synthesizers thereby producing a plurality of outputs from said first synthesizers at the same frequency and at predetermined differing phases, said second direct digital frequency synthesizers each comprising;

a. phase accumulator means including a phase register for receiving a clock signal and digital information corresponding to a frequency of operation and synchronously producing a digital output corresponding to a predetermined value of a sinusoid at a phase designated by the digital output, and including a first adder having inputs for receiving, respectively, a digital word corresponding to a frequency and the phase register digital output, the output of said first adder being coupled to an input of said phase register,

b. memory means for storing predetermined values of a sinusoid at phases designated respectively, by phase addresses corresponding to the digital output from said phase accumulator means,

c. means for producing a second digital word corresponding to a predetermined phase shift for producing a phase address output used to select an address in the memory means containing the sinusoidal value for the waveform at the point indicated by the desired phase shift input,

d. second adder means for receiving the digital output from said phase accumulator means and said second digital word corresponding to a predetermined phase shift, the output of said second adder means supplying to said memory means an address therein shifted by a value corresponding to said second digital word and

e. digital to analog converter means for producing an analog waveform output corresponding to the value selected by the phase address output supplied to said memory means, the output from said digital to analog converter means being supplied to said first frequency synthesizer connected, respectively, to the second direct digital frequency synthesizer for producing a predetermined phase of operation thereof.