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   Visit Us at IMS 2008
   
     June 15 - 20, 2008
      Visit Booth # 932

Call: 603.644.2326
Fax: 603.647.6889

1000 East Industrial Park Drive
Manchester, NH 03109

info@ionbeammilling.com
 

The Lange Coupler is a four port interdigitated structure developed by Dr. Julius Lange in 1969. The couplers are widely used as power combiners and splitters in microwave amplifiers as well as in mixers and modulators. The coupling is derived from closely spaced transmission lines, such as microstrip lines. Typically the number of conductors or fingers (N) is even. The geometry for N=4 is shown below, accordingly:

The length of the fingers (L) is set by the center frequency (f0) of the filter. The device is relatively broadband, with flat frequency response around f0.

The finger length is equal to the quarter wavelength (λs) of f0 in the substrate.

The coupler is usually designed for 3dB of coupling between the input port (1) and the coupled (2) and direct port (4). The phase angles of the coupled signals are 90 degrees out of phase with the input near the design frequency. For such a splitter, the theoretical maximum coupling is -3dB in each channel (half power). These coupling characteristics are most sensitive to conductor spacing (s) and the metal thickness (t) for a given number of fingers (n).

Lange couplers with 4, 6, and 8 fingers have been processed in production quantities with performance variations under +/-2%.

Our ability (standard process) to realize (s), (w), (l) tolerances of +/- 1 micron is a testimonial to our anisotropic etch process.