Model XC2100A-20
Rev D
narrowing the line before the interface pad will introduce a series inductance, which, when properly tuned, will
compensate for the extra capacitive reactance. If a thicker circuit board or one with a lower dielectric constant is used,
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 and 5dB couplers is different from that of the 10dB and 20dB couplers. The
test board for the 3dB and 5dB couplers has all four traces interfacing with the coupler at the same angle. The test
board for the 10dB and 20dB 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 & 20dB Test Board
Testing Sample Parts Supplied on Anaren Test Boards
3 & 5dB Test Board
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
Avg. Ins. Loss of Test Board @ 25°C
~ 0.07dB
~ 0.12dB
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.
Available on Tape
and Reel for Pick and
Place Manufacturing.
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Europe
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(800) 411-6596
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