Looks like that would only cover one specific configuration with matching
patterns on opposite sides of the board, connected at the center of the
spiral pattern.  Not a spiral on one side with a straight terminal trace
on the other, or some other configuration.

On Thu, 30 Nov 2000, Robert Rolf wrote:

> Here is the patent you'd be infringing.
> Given that you're in ZA?? you _may_ get away with infringing it
> for a short while. (I seem to recall that US patents are now good for
> 20 years instead of 17)
>
> It never ceases to amaze me what 'prior art' the patent office
> will grant patents for. I KNOW I saw this technique used in some
> RF test equipment from the late 60's, so why was a patent granted?
>
>
> http://www.delphion.com/details?pn=US04494100__
>
> Inventors:
> Stengel; Robert E. , Pompano Beach, FL
> Nejdl; Charles W. , Ft. Lauderdale, FL
> Applicant(s):  Motorola, Inc., Schaumburg, IL
>
> Issued/Filed: Jan 15, 1985/ July 12, 1982
>
> A planar inductance element includes a generally flat substrate of
>                      electrically insulating material. First and second
> substantially flat
>                      spiral coils, having respective inner and outer
> ends, are disposed on
>                      opposite sides of the substrate. The coils are
> spiraled in the same
>                      direction as viewed from one side of the substrate
> with one coil
>                      spiraling out and one spiraling in. The inner ends
> of the coils are
>                      joined through the substrate to couple the coils in
> series. The outer
>                      ends of the coils provide terminals for the
> inductor. The
>                      means/methods are disclosed for discretely and
> progressively
>                      trimming the inductor.
>
>
> Werner Soekoe wrote:
> >
> > Mark,
> >
> > You have totally confused me now. I don't have the feintest idea what the
> > ohms/mm is all about. But lets put it this way. I will be using the
> > oscillator circuits in transmitters and receivers. The one will transmit at
> > +- 100MHz (FM Band) and the other at approxiamately 280 MHz.
> >
> > What can you tell me about this?
> >
> > Thanx
> > Werner
> > WernerS@fsl.gov.za
> >
> > ----- Original Message -----
> > From: "Mark Hull" <technical@EMSAFRICA.CO.ZA>
> > To: <PICLIST@MITVMA.MIT.EDU>
> > Sent: Thursday, November 30, 2000 12:37 PM
> > Subject: [EE]: Coil Imprinted on PCB
> >
> > Hi Werner
> >
> > What frequency are you working at?
> > Most PCB coil calculations work in impedance terms as in ohms / mm when at
> > RF frequencies.
> > You then just have to zigzag the track to fit into the space you're using.
> >
> > Below RF you have to use conventional components.
> >
> > Cheers
> > Mark
> > -------------------------------------------------------------------
> > Mark Hull
> > Engineering/Technical
> > EMS (Africa) (Pty) Ltd
> > PO Box 1026, Melville, 2109, South Africa
> > Ph +27 11 482 4470 Fax +27 11 726 2552

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