XC3500M-20S Datasheet, PDF (8/21 Pages) Anaren Microwave – 20dB Directional Coupler

Model XC3500M-20S
Rev A
the interface pad will have less capacitive reactance than the Anaren test board. In this case, a wider section of line
before the interface pad (or a larger interface pad) will introduce a shunt capacitance and when properly tuned will
match the performance of the Anaren test board.
Notice that the board layout for the 3dB couplers is different from that of the 10dB couplers. The test board for the
3dB couplers has all four traces interfacing with the coupler at the same angle. The test board for the 10dB couplers
has two traces approaching at one angle and the other two traces at a different angle. The entry angle of the traces
has a significant impact on the RF performance and these parts have been optimized for the layout used on
the test boards shown below.
10 dB Test Board
3 dB Test Board
Testing Sample Parts Supplied on Anaren Test Boards
If you have received a coupler installed on an Anaren produced microstrip test board, please remember to remove the
loss of the test board from the measured data. The loss is small enough that it is not of concern for Return Loss and
Isolation/Directivity, but it should certainly be considered when measuring coupling and calculating the insertion loss
of the coupler. An S-parameter file for a “Thru” board (see description of “Thru” board above) will be supplied upon
request. As a first order approximation, one should consider the following loss estimates:
Frequency Band
800 - 1000 MHz
1700 – 2300 MHz
2300 – 2700 MHz
3300 – 3800 MHz
Avg. Ins. Loss of Test Board @ 25°C
~ 0.07dB
~0.12dB
~0.15dB
~0.17dB
For example, a 1900MHz, 10dB coupler on a test board may measure –10.30dB from input to the coupled port at
some frequency, F1. When the loss of the test board is removed, the coupling at F1 becomes -10.18dB (-10.30dB +
0.12dB). This compensation must be made to both the coupled and direct path measurements when calculating
insertion loss.
The loss estimates in the table above come from room temperature measurements. It is important to note that the
loss of the test board will change with temperature. This fact must be considered if the coupler is to be evaluated at
other temperatures.
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