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liberal
Joined: 25 Nov 2004
Posts: 122
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 24 Mar 2005 4:38 Q:Directional Coupler |
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in two articles ,i have seen two similar directional couplers.but their coupled output and isolated output are different.it puzzles me!and how can i design a directional coupler.thank u.
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flatulent
Joined: 19 Jul 2002
Posts: 4877
Helped: 324
Location: Middle Earth
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24 Mar 2005 6:44 Re: Q:Directional Coupler |
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| In these parallel line couplers, the coupled power appears at the secondary coupled line in the end that is near the source of the power in the main line. The coupling depends upon the differential mode impedance and the common mode impedance. This is called odd and even modes in the RF world.
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biff44
Joined: 24 Dec 2004
Posts: 1835
Helped: 244
Location: New England, USA
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24 Mar 2005 15:11 Re: Q:Directional Coupler |
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The confusion is decades old. Waveguide coupler's coupled output port is farthest away from the input port. Conversely, microstrip or stripline coupled line's coupled output port is closest to the input port.
Any system level schematic symbol should rely on no assumptions in the reader's mind, and should always show an arrow or words depicting coupling direction.
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sergio mariotti
Joined: 22 Dec 2003
Posts: 467
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26 Mar 2005 12:25 Re: Q:Directional Coupler |
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Figure 1 show roughly the layout of a ustip/stripline coupler
Figure 2 show rougly both the layout of a waveguide coupler and a generic coupler.
Both pictures may be used in a block schematic, it's important to draw the arrow that decribe the coupled port.
Then, the correct displacement of the coupler will be choosed during the assembly procedure.
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burton
Joined: 12 Dec 2003
Posts: 198
Helped: 9
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22 Apr 2007 16:56 Re: Q:Directional Coupler |
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| Fig.2 shows the hybrid coupler, and Fig.1 shows the parallel coupled-lines or parallel coupled-waveguide coupler.
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Borber
Joined: 01 Jan 1970
Posts: 1561
Helped: 117
Location: Slovenia
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22 Apr 2007 18:22 Re: Q:Directional Coupler |
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| The first picture is only symbolic and second shows a kind of realization. Ports on both pictures are marked equal and correct.
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flyhigh
Joined: 12 Nov 2003
Posts: 561
Helped: 32
Location: somewhere over the rainbow
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23 Apr 2007 9:37 Re: Q:Directional Coupler |
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Hi,
Good comments above, just to add mine
Yeah, there is a kind of (unwritten?) convention that
port 1 is an input
port 2 is trough output
port 3 is coupled output
port 4 is isolated
I think that both pictures are schematics only without any reference to the internal realizations of the couplers, and the port assigments are in that sence correct.
The internal structures could be waveguide or planar lines, but one can manipulate the locations of the ports on schematics to simplify the drawing.
flyhigh
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g579
Joined: 01 Jan 1970
Posts: 476
Helped: 14
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23 Apr 2007 15:44 Re: Q:Directional Coupler |
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I think sergio mariotti's comments on Fig 1 and Fig 2 are interchanged. Fig 2 shows the strip/ustrip realization.
g579
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zorro
Joined: 06 Sep 2001
Posts: 380
Helped: 47
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23 Apr 2007 16:54 Q:Directional Coupler |
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Hi g579,
Probably you didn't realize that fig. 1 is the bottom gifure in liberal's post, and fig. 2 is the top one.
Sergio's comment is ok, in agreement with bif44.
Regards
Z
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23 Apr 2007 16:54 Ads |
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g579
Joined: 01 Jan 1970
Posts: 476
Helped: 14
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23 Apr 2007 21:27 Re: Q:Directional Coupler |
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Hi zorro,
You are absolutely right, I am sorry, I presumed that Fig 1 is the first and Fig 2 is the second fig.
I was mistaken. Sorry again. sergio marotti is right.
Regards
g
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HOHOH
Joined: 13 Feb 2002
Posts: 62
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25 Apr 2007 11:50 Re: Q:Directional Coupler |
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Hi~!.
The propagation of TEM mode and quasi-TEM mode is related to backward directional coupler and the progapation of TE mode and TM mode is related to forward directional coupler.
It's mean backward directional coupler has backward coupling and forward directional coupler has forward coupling.
Have a good time!
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