Building and characterizing a DIY RF power sensor

powersensor1

Kerry Wong writes:

For the build, I followed LT’s reference design detailed in the datasheet. For the output filtering, I used a 2.2K/10pF output RC filter to limit the output bandwidth to around 3 MHz.
Since we are in the RF realm, board layout becomes much more critical than dealing with sub MHz circuits. But for the prototype, I used a piece of FR-4 PCB and routed a few islands for the power, input and output. This leaves us with a large contiguous ground plane which is critical in lowering ground inductance. The LC5534 chip is mounted on a trimmed adapter board, which is then glued onto the PCB’s ground plane. The wiring is kept as short as possible to minimize unwanted coupling. I used a BNC connector for the input. Since the maximum frequency LT5534 can handle is 3 GHz, a BNC connector should be sufficient. The BNC input is terminated right at the input. A RF rated surface-mount 47 Ohm resistor would have been ideal here but I used a nominal 50 Ohm (measured 47 Ohm) 1/16 W carbon film resistor instead as it’s the only kind I have on hand.

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