What is the dynamic range requirement for a spectrum analyzer to measure spurious emissions?

What is the dynamic range requirement for a spectrum analyzer to measure spurious emissions? The dynamic range determines how far below the carrier the analyzer can detect spurious signals, and it must exceed the regulatory or specification spurious emission limit: (1) Spurious emission requirements: 3GPP 5G NR (TS 38.104, BS): spurious emissions must be ≤ -30 dBm in any 1 MHz band outside the operating band. For a +46 dBm (40W) base station: the dynamic range needed = 46 - (-30) = 76 dB in a 1 MHz measurement bandwidth. FCC Part 15 (unlicensed devices): spurious emissions ≤ -41.3 dBm/MHz (or stricter for some bands). For a +20 dBm Wi-Fi device: dynamic range needed = 20 - (-41.3) = 61.3 dB. ETSI EN 300 328 (2.4 GHz): spurious emissions ≤ -30 dBm below 1 GHz, ≤ -47 dBm above 1 GHz. (2) Spectrum analyzer dynamic range contributors: DANL (displayed average noise level): the noise floor of the analyzer. Determines the weakest signal that can be measured. DANL = -150 to -170 dBm/Hz for modern analyzers. In 1 MHz RBW: DANL = -150 + 60 = -90 dBm (entry-level) to -170 + 60 = -110 dBm (high-end). Phase noise: limits the ability to measure spurs close to the carrier. At 10 kHz offset: -100 to -120 dBc/Hz. At 1 MHz offset: -120 to -150 dBc/Hz. Distortion (TOI): the analyzer itself generates intermodulation products when driven by a strong signal. Third-order intercept (TOI): +10 to +25 dBm for most analyzers. Spurious-free dynamic range (SFDR): limited by the lesser of DANL, phase noise, and TOI. SFDR = (2/3) × (TOI - DANL) for third-order products. Example: TOI = +15 dBm, DANL = -150 dBm/Hz → SFDR = (2/3)(15+150) = 110 dB (in 1 Hz BW). (3) Practical measurement setup: for a +46 dBm BS: an external attenuator (20-30 dB) is needed to avoid overdriving the analyzer. This reduces the effective dynamic range by the attenuation value. To measure -30 dBm spurs from a +46 dBm carrier: use 20 dB external attenuation → carrier at +26 dBm at analyzer input. Need to see -30 dBm → dynamic range needed: 26 - (-30) = 56 dB at the analyzer input. This is well within the capability of any modern spectrum analyzer. For very stringent measurements (-90 dBc spurs): need 90 dB dynamic range → narrow RBW, long sweep time, and a high-performance analyzer.