|All versions|{{download|http://www.emagtech.com/downloads/ProjectRepo/RFLesson12.zip RF Lesson 12}} }}
=== What You Will Learn ===
In this tutorial you will explore the operation of several generic RF devices in [[RF.Spice A/D]] including Wilkinson Power Divider, Branchline Coupler and Rat-Race Coupler.
[[File:RFTUT12 10.png|thumb|350px|Diagram of a Rat-Race Hybrid Coupler circuit.]]
In this part of the tutorial lesson, you will examine [[RF.Spice]]'s Rat-Race Hybrid . This is primarily used as a 180° coupler as shown in the opposite figure. In this case, Port 3 is used as the input. The power is delivered to the output ports 1 and 4. Port 2 is the isolated port and is terminated in a 50Ω resistor. The output ports 1 and 4 have a 180<sup>o</sup> phase difference and are both terminated in equal 50Ω resistive loads. Place and connect the parts according to following simple circuit:
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Run a Transient Test of this circuit with the [[parameters]] specified below:
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In this case, Port 1 acts as the input port, Ports 3 and 2 are the output ports and Port 4 is isolated. Run a transient test with the same sinusoidal waveform and test [[parameters]] as before. The figure below shows the four port voltage graphs. Note that in this case the two output ports are in-phase. This is expected from the scattering matrix given above.
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Run a Transient Test of this circuit with the [[parameters]] specified below:
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As another try, change the peak amplitude of the second voltage source V2 to 1.5V. Run a new Transient Test of the circuit with the same [[parameters]] and view the port voltage graphs as shown below. The following table shows the peak amplitudes of the four port voltage waveforms. The simulated results agree very well with the expected analytical results.
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