2017年全国少年乙组羽毛球比赛首次在唐山举办

On behalf of Eamon Nash.

We touched off this a little bit in the webcast. There is more to say about the topic. There are three approaches that we recommend.

1. Use a dual RF Detector. You can use a dual directional coupler that couples off forward and reverse power and apply the two coupler outputs to a dual log amp (or a dual rms detector that has a linear-in-dB transfer function). Depending on the power level being transmitted, the signals coming from the coupler may need to be attenuated further before applying them to the detectors (most RF detectors have a max input power that is in the -5 dBm to +5 dBm range). Dual RF detectors such as ADL5519 also have an internal differential amplifier. So the voltage from this diff amp will be proportional to the dB return loss.
2. Use a single Linear in V/V detector such as ADL5511 or ADL6010: In this case you also start with a dual directional coupler to sense the forward and reflected power. But then you connect an absorbtive Single Pole Double Throw Switch to the two coupler outputs and switch back and forth. You would connect the output of the rf detector to a low speed precision ADC and would sample the forward and reverse signal levels. As is explained in CN0387 (www.analog.com/cn0387), the return loss is a simple ratio calculation that requires no calibration.
3. Another option to look at is ADL5920 which is a dual detector with integrated dual directional coupler. This is essentially an integrated version of option 1 above. Be aware that the insertion loss of the integrated coupling mechanism (1-2 dB) is higher than at stand-alone directional couipler. Also the integrated coupler has a max power handling capability of +30 dBm