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RF is not 'black magic' – It's Synthesis, Optimization, Analysis and Realization.
The physics is no longer bewildering to me, as it was thirty years ago when I was thrust into the microwave business, but the rules and regulations can still be−
Let’s start with this five-letter acronym for “PCS-type Certification Review Board.” Nested within this acronym is another acronym for “Personal Communications Service.” Surfing over to their home page, “Welcome to PTCRB,” one is confronted by more acronymia. (By the way, ‘ptcrb’ is not found in acronymia.com’s dictionary at this writing.) I tried unsuccessfully to find out the rules for “obtaining PTCRB Certification on a mobile device” because I couldn’t provide the required company website on the Registration Page.
This TLA stands for “Radiated Spurious Emissions.” RSE are(is?) at the crux of the PTCRB certification. Finding their source(s) and mitigating them is exactly like the other stuff I love to do. Except finding out the rules, which is exactly like the stuff I hate.
Originally dubbed the “Cellular Telephone Industries Association,” but now calling themselves, “CTIA – The Wireless Association,” lets you browse their website. I found a Test Plan for Wireless Device Over-the-Air Performance there, but no mention of allowed RSE levels.
Time to change tactics… I decided to look at websites of companies who operate the equipment.
Sometimes I forget all the great engineering that came out of the old Bell Telephone Laboratories. So it was great to find this App Note: Antenna Fundamentals. (Maybe I liked it so much because it was like an advertisement for what I am good at doing!) I especially liked this quote:
A failure to meet FCC regulations or PTCRB radiated-spurious-emissions-conformance requirements due to a level of harmonic energy generated by the device is often blamed on the antenna. In truth, the antenna can often influence the level of the harmonics but does not generate these signals. An antenna almost never has gain at the harmonics of the intended band of operation. Provided the radio has acceptable harmonic performance, excessive harmonic generation is typically an interaction between the impedance of the antenna and the impedance of the final stage of the transmitter.
−ATT Antenna Fundamentals – Technical Brief, p. 34
This is a great Tech Brief, especially because it doesn’t push one type or brand of antenna over another, and it isn’t written to scare anybody into becoming a customer …but I still didn’t have my RSE answer.
(I don’t remember what the letters stand for, but it’s been a trade magazine for a long time. I emailed the editor, so maybe he’ll get back to me on this.) Bleary-eyed, I clicked on a link to their article, Cellular Carrier Certification Requirements and scanned down the page… Bingo!
Note that PTCRB limits follow ETSI limits, not FCC limits.
(European Telecommunications Standards Institute) After all that, I really appreciated their website: The first link on their homepage was Standards. It still took a while to get to the right document, but at last I believed I had found it:
ETSI standard ETSI EN 301 502 V10.1.1 (2012-01)
Table 4.2.5-1: Spurious Emissions Measurements outside the transmit band
Frequency offset outside
relevant transmit band
Maximum power limit
9 kHz to 1 GHz
≥ 2 MHz
≥ 5 MHz
≥ 10 MHz
1 GHz to 12,75 GHz
≥ 2 MHz
≥ 5 MHz
≥ 10 MHz