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XC1500A-20S

Rev B

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.

54606-0003

Rev.B w=66.0

10 & 20dB 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

Avg. Ins. Loss of Test Board @ 25

C

410 – 500 MHz

~ 0.4dB

800 – 1000 MHz

~0.06dB

1700 – 2300 MHz

~0.14dB

2300 – 2700 MHz

~0.155dB

3300 – 3800 MHz

~0.20dB

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.