双频功分器设计

Dual Frequency T-Junction Power Divider Laboratory Objective:
Design, optimize, build, and test a 3 dB T-Junction power divider
1. Review the text and design a 3-dB T-junction power divider using microstrip line
(Pozar, 2nd Ed., Section 7.2, pp. 359-362). The power divider should have a center frequency of 2.5 GHz. You will first use HPADS to perform your design.
2. HPADS design.
A. Design your 3dB power splitter as described in Pozar assuming an ideal lossless
line. Design the quarter-wave transformer sections for the output ports,
calculating the impedance and the lengths. (this was done in HW#7)
B. Build your schematic using microstrip lines. Your substrate - specified using
MSUB - is a 30 mil GML 1000 Gil Laminate substrate with relative permittivity of 3.20 and a loss tangent of 0.001. The conductor is copper (75.710× S/m). Use MLIN for the uniform microstrip lines, MSTEP for any abrupt changes in line widths, MBEND for bends, and MTEE for the split. Use Linecalc to determine the width of the 50 ohm microstrip line, and the lengths and widths of microstrip lines. Make sure that the proper widths are used in MTEE for each port connection.
C. Add 1 inch of 50 ohm line to the input and output ports to allow the soldering on
the connectors and accurate measurement. Also, note that there are some physical constraints to the project. First, the circuit must fit on a 3" × 3" board (This
should not present a problem). Secondly, the two output ports will have to be tied to two band pass filters of a WLAN. Thus, you should try to maintain sufficient distance between the two output ports (about 2" is sufficient). To realize this, the QWT's should run orthogonal from the T a sufficient distance and then turn
parallel to the input port through mitered 90 degree bends (note that the mitered bend reduces capactive loading) Both output ports should then exit the same side of the board. An example divider is illustrated above.
D. Save the circuit and simulate the S-parameters with HPADS. Note: this is a
three-port network and has nine S-parameters describing its operation. Decide
which parameters are important for your design and prepare to plot them from 2-3 GHz.
E.Optimize the quarter wave transformers:
Based on the simulation, determine where your design deviates from the optimal.
You can adjust line lengths and possibly widths to optimize your design to 2.5
GHz. Eventually, you will actually be operating the T-splitter at 2.4 and 2.6 GHz.
Thus, it is important that its response is centered at 2.5 GHz, and that the insertion loss is minimal.
F.When you are satisfied with the response of the circuit, double check to see that
the parameters in parts A-E above are met. The next step is to generate a layout.
You can do this by clicking Layout - Generate Layout. Save the layout and email this to the instructor to generate the mask.
Measure your circuit:
1.Fabricate your circuit using the PC Board Etching process from the masks based on
your circuit provided by the instructor.
2.Solder on edge mounted SMA connectors to your circuit board.
3.Calibrate the network analyzer from 2-3 GHz (if necessary).
4.Attach port one of the circuit to the forward channel cable. Attach one of the two
output ports to the reverse channel cable of the Network Analyzer. Note that the third port will have to be terminated into a 50 ohm matched impedance to take the two port S-parameters. Use the 50 ohm SMA load to do this.
5.View the different parameters on the Network analyzer for this port pair. Save the
data to a PC formatted disk.
6.Switch the output port and the matched load and view the S-parameters again. Save
this data to a PC formatted disk as well.
7.Plot your network analyzer results against your HPADS results on the same graph.
8.Draw conclusions: How well matched are all of your ports? Was the power divided
as expected? What losses were observed? Explain the loss mechanisms and other parasitic effects that deteriorate the performance from the ideal?。