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Microstrip Rat-Race Coupler (Aggregate): MRRCOUP2



MRRCOUP2 models a microstrip rat-race coupler (180o hybrid). MRRCOUP2 is a general model; it allows arbitrary lengths and widths of feeding lines and sections of the ring lines.



Name Description Unit Type Default
ID Name Text TL1
W1 Width of feeding line at ports 1 and 2 Length W[1]
W2 Width of the feeding line at port 3 and 4 Length W[1]
W3 Width of the line connecting ports 1 and 2 Length W[1]
W4 Width of the line connecting ports 1,3 and 2,4 Length W[1]
W5 Width of the line connecting ports 3 and 4 Length W[1]
L1 Length of the line connecting ports 1,3 and ports 2,4 Length L[1]
L2 Length of the line connecting ports 1 and 2 (about 3/4 w/len) Length L[1]
L3 Length of the line connecting ports 3 and 4 Length L[1]
MSUB Substrate definition Text MSUB1[2]

[1] User-modifiable default. Modify by editing the default.lpf file in the root installation directory. See the “The Layout Process File (LPF)” for details.

[2] Modify only if the schematic contains multiple substrates. See “Using Elements With Model Blocks” for details.

Parameter Details

L1. Line connecting ports 1,3 and line connecting ports 2,4 have the same length L1.

L2. Full length of line connecting ports 1 and 2.

L3. Full length of line connecting ports 3 and 4.

Parameter Restrictions and Recommendations

  1. MRRCOUP2 uses MCURVE and MTEE (microstrip arc line and microstrip T- junction) models, so all limitations of these models apply to MRRCOUP2.

  2. For equal split 3 dB coupler (equal power split and 180o phase shift between ports 3 and 4):



    L1=L3eff/4; (quarter of effective wavelength)


    W3,W4, and W5 provide characteristic impedance of corresponding lines equal to √2 times the characteristic impedance of feeding lines.

Implementation Details

MRRCOUP2 implies that a coupler is mirror symmetrical relative to the horizontal axis (see the "Topology" section).


This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.

Recommendations for Use

Feeding lines at ports may have different characteristic impedances. This is provided by proper choice of width parameters W1, W2 (see the "Topology" section).

To ensure the specified power split, matching, isolation and phase shift between branched lines, parameters may be derived in accordance with the recommendations in Reference [1]. However, you may set parameters to values of your choice or use them for circuit optimization.

NOTE:The MRRCOUP element is considered obsolete due to errors in port numbering; MRRCOUP2 is recommended for use.


[1] Mongia, R., Bahl,I.J., and Bhartia P., RF and microwave coupled-line couplers, Artech House, Norwood, MA, 1999, pp. 260-264

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