Band Edges Requirement FCC边带测试理解

Test Requirement:      FCC Part15 C section 15.247
In any 100 kHz bandwidth outside the frequency band in which the spread spectrum or digitally modulated intentional radiator is operating, the radio frequency power that is produced by the intentional radiator shall be at least 20 dB below that in the 100 kHz bandwidth within the band that contains the highest level of the desired power, based on either an RF conducted or a radiated measurement, provided the transmitter demonstrates compliance with the peak conducted power limits. If the transmitter complies with the conducted power limits based on the use of RMS averaging over a time interval, as permitted under paragraph (b)(3) of this section, the attenuation required under this paragraph shall be 30 dB instead of 20 dB. Attenuation below the general limits specified in Section 15.209(a) is not required.

In addition, radiated emissions which fall in the restricted bands, as defined in Section 15.205(a), must also comply with the radiated emission limits specified in Section 15.209(a) (see Section 15.205(c)).

Frequency Band:        2400 MHz to 2483.5 MHz
Test Method:              ANSI C63.10: Clause 6.9 & DA 00-705

测试时将频谱分析仪设置相关好曲线参考单位Unit、参考Trace reference、 衰减Attenuation等参数使其曲线能到仪表合理显示范围内外，最重要的一个是设置RBW也就是标准里面提及的100KHz解析度、以及合适的VBW值……

其一是传导杂散测试法：测试其频段2400MHz~2483.5MHz以外以的点（一般是指其上下边带如2400MHz以前频率的点与2483.5MHz以后频率的点）的以100KHz RBW解析度用RMS检波器测试出来的点应该比频段2400MHz~2483.5MHz内主波功率至少要有20dB的衰减。

其二是辐射杂散测试法：在第一点所测试到的杂散点，如果该杂散点的频率是落在15.205章节中所规定限制带宽中，那这个杂散频率点的PK和AV值就必须符合15.209的限值（即：PK-74dBuV, AV-54dBuV），这就是为什么常常在测试中需要测试2390MHz这个频点，且也并不是只有边带附近可用20dB衰减，只要不是在限制带宽内的频点，都可以用相对20dB衰减量来判定该杂散点是否满足要求。

是啊，因为15.247是针对发射功率相对较大的产品，所以对谐波跟杂散的限值也放宽了，低于主频功率20dB就行了。15.249的产品发射功率相对较小，可以看到这章节的谐波压得很低，跟15.209一样

当然不管哪个章节限制频带内的点都要满足15.209

Helen.ma 发表于 2015-4-19 14:58
当然不管哪个章节限制频带内的点都要满足15.209

Helen 多谢！