Method and apparatus for mapping printed circuit fields

• US 5,028,866 A
• Filed: 05/30/1990
• Issued: 07/02/1991
• Est. Priority Date: 05/30/1990
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Wiese, Richard W.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Nguyen, Vinh P.
• Application Number:
  US07/530,780
• Time in Patent Office: 398 Days
• Field of Search: 324/158 F, 324/158 P, 324/72.5, 324/95, 324/158 R, 343/703, 455/67, 455/226, 455/115, 340/600, 340/825.34
• US Class Current: 324/763.01
• CPC Class Codes: G01R 31/304 of printed or hybrid circuits G01R31/305 - G01R31/315 take precedence
• CPC Class Codes: G01R 31/315 by inductive methods

Abstract

An electromechanical XY carriage sweeps a magnetic or electrical field probe across a circuit board line by line to acquire field strength data as a function of probe position relative to the board. Colored field maps are produced. The carriage is controllable to obtain very high resolution data. A magnetic probe includes a single loop oriented parallel to the board or a loop oriented perpendicular to the board and selectively parallel to or perpendicular to the x axis of the carriage. Different field maps are produced by different probe orientations and each provides information regarding the circuit traces which carry rf currents.

Claims

1. A method of analyzing an electromagnetic field emanating from a printed circuit board having circuit elements generating such field comprising the steps of:

electrically energizing the circuit elements to produce an electromagnetic field adjacent the board,

sensing the field components in a first direction along a prescribed path to generate a first set of data representing varying field strength along the path,

sensing the field components in a second direction normal to the first direction along the said prescribed path to generate a second set of data representing varying field strength along the path,

displaying the first and second sets of data to provide first and second maps illustrating field strength patterns, and

comparing the patterns of the maps to determine the sources of the electromagnetic fields.

2. The method as defined in claim 1 including the steps of;

sensing the field components in a third direction normal to the first and second directions along the said prescribed path to generate a third set of data representing varying field strength along the path, and

displaying the third set of data to provide a third map illustrating field strength patterns, whereby all three maps are compared to determine the sources of electromagnetic fields.

3. A method of mapping an electromagnetic field emanating from a printed circuit board having components and circuit paths giving rise to such field comprising the steps of:

electrically energizing the circuit on the printed circuit board with radio frequency energy to produce an electromagnetic field adjacent the circuit board,

moving a sensor through said field in a prescribed path to generate varying sensor outputs by repetitively traversing the sensor parallel to an axis of the board and indexing the sensor in a direction normal to the axis after each traverse to cover the board area,

acquiring field data by sampling the sensor outputs along the path,

displaying the sampled data in accordance with strength to provide a map illustrating field strength patterns.

4. A method of mapping an electromagnetic field emanating from a printed circuit board having components and circuit paths giving rise to such field comprising the steps of:

electrically energizing the circuit on a printed circuit board with radio frequency energy to produce an electromagnetic field adjacent the circuit board,

moving a directional magnetic field sensor oriented for sensitivity to magnetic field components normal to the board surface through said field in a prescribed path to generate varying sensor outputs,

acquiring field data by sampling the sensor outputs along the path,

displaying the sampled data in accordance with strength to provide a map illustrating field strength patterns.

5. The method as defined in claim 4 including the step of superimposing an outline of the components on the map.

6. The method of claim 4 including the step of limiting the acquired field data to a given frequency range whereby the map represents the field strength distribution for said field range.

7. A method of mapping an electromagnetic field emanating from a printed circuit board having components and circuit paths giving rise to such field comprising the steps of:

electrically energizing the circuit on the printed circuit board with radio frequency energy to produce an electromagnetic field adjacent the circuit board,

moving a directional magnetic field sensor through said field in a prescribed path that is a series of parallel straight lines spaced across the area of the circuit board to generate varying sensor outputs, said sensor being oriented for sensitivity to magnetic field components normal to said straight lines and parallel to the board surface,

acquiring field data by sampling the sensor outputs along the path,

displaying the sampled data in accordance with strength to provide a map illustrating field strength patterns.

8. A method of mapping an electromagnetic field emanating from a printed circuit board having components and circuit paths giving rise to such field comprising the steps of:

electrically energizing the circuit on the printed circuit board with radio frequency energy to produce an electromagnetic field adjacent the circuit board,

moving a directional magnetic field sensor through said field in a prescribed path that is a series of parallel straight lines spaced across the area of the circuit board to generate varying sensor outputs, said sensor being oriented for sensitivity to magnetic field components parallel to said straight lines.

acquiring field data by sampling the sensor outputs along the path,

displaying the sampled data in accordance with strength to provide a map illustrating field strength patterns.

9. A method of mapping an electromagnetic field emanating from a printed circuit board connected to a harness and having components and circuit paths giving rise to such field comprising the steps of:

electrically energizing the circuit on the printed circuit board with radio frequency energy to produce an electromagnetic field adjacent the circuit board by inductively coupling radio frequency energy into the harness to simulate the effect of external radio frequency fields on the circuit board,

moving a sensor through said field in a prescribed path to generate varying sensor outputs,

acquiring field data by sampling the sensor outputs along the path,

displaying the sampled data in accordance with strength to provide a map illustrating field strength patterns.

10. Apparatus for mapping the electromagnetic field emanating from a printed circuit board connected to a harness comprising:

inductor means for coupling radio frequency energy into the harness to cause said field to emanate from the printed circuit board,

a sensor responsive to the electromagnetic field to generate output signals representing field strength,

electromechanical means supporting the sensor for sweeping the sensor in a pattern passing through the field,

receiver means for acquiring data represented by the output signals, and

display means coupled to the receiver means for mapping the signal in a field strength pattern.