How To Measure Pulsed RF on Remote Control

In this picture, the pulsed RF output of a remote control to a garage door opener is measured with Oscium’s WiPry-Combo and displayed using an iPhone. First, confirm that the device is in power meter mode (versus spectrum mode). The time scale is set to display two pulses – the minimum necessary to use WiPry-Combo's built-in signal statistics and automated measurement features. The trigger level is set high enough that WiPry-Combo is triggering strictly on the intended waveform and not another spurious signal.

Radiated or Conducted Measurements? 

This is a conducted measurement so the only RF power sampled is coming from the remote control; no radiated emissions from other nearby sources can influence the measured power. For measuring waveform characteristics like Pulse Width and Duty Cycle, a conducted measurement is more accurate than a radiated measurement. However, if the objective was to measure transmit power over the air and at a distance, the setup must be a radiated measurement to account for the transmission loss.

Oscium Enables RF test equipment on iOS Platform

In order to replicate this setup, users will need the following pieces of equipment, or suitable substitutions, in addition to an iPhone, iPod touch, or iPad, and the WiPry-Combo iOS Test accessory.

RF “Sniffer” Probe: The sniffer probe in the picture is made from a piece of wire and a short length of semi-rigid coaxial cable. The cable’s inner conductor is exposed (just long enough to touch the RF traces) by cutting away the outer conductor and the insulation. The piece of wire is soldered to the outer conductor and extended so that it will make contact with the circuit board when probing the RF trace. An additional female-to-female in-series adapter may be necessary, depending on the termination of the sniffer probe, to mate the probe with the RF cable.

Coaxial RF Cable: This kind of measurement is easier to make with thinner, light weight cable that is flexible enough to allow adequate movement for probing. Bulky and stiffer cables make it difficult to put the probe in a proper position to make measurements. Other cable characteristics to keep in mind are power handling, frequency rating, the type of connectors, and insertion loss (usually given in dB/foot vs. frequency by the manufacturer).

Between series adapter: In this case, the between series adapter is an SMB to SMA that is included in Oscium’s conducted measurement kit. The operating frequency and power handling rating of the connector are consistent with WiPry-Combo’s frequency and power specifications.

Attenuator (optional): If the device tested was a powerful transmitter, say +20 dBm output, it would be necessary to use an external attenuator in the setup. The attenuator would be inserted in the RF path between the RF probe, measuring the output power of the device, and the input port to WiPry-Combo. The software application includes provisions that will correct the measured RF power for line loss attributed to the external attenuator.