无线门铃的FCC认证标准是怎样的?

　　无线门铃的英文名称是wireless door phone或wireless doorbell，又称无线遥控门铃或遥控门铃。常见无线门铃有不用电池的无线门铃、普通无线门铃及可视无线门铃。无线门铃是利用民用无线技术(315M、433.92M、Zigbee、WIFI、蓝牙、2.4G等)开发出来的一类门铃。一般的无线门铃有效传输距离约40米。无线门铃不需要布线，安装简单灵活，但是传输距离受传输距离和现场环境影响较大。有线门铃正好与之相反。普通无线门铃需要使用电池，需要及时更换电池。不用电池的无线门铃则依靠手按按钮发电技术供能，摆脱电池的限制。下面我们一起探讨一下无线门铃的FCC认证。

　　433.92M无线门铃的FCC认证依据标准是47 CFR Part 15 Subpart C，具体测试项目如下：

　　ClauseTest ItemRule

　　1Transmitter 20dB BandwithC.F.R.47 FCC Part 15：Section 15.231(c)

　　2Transmitter TimeoutC.F.R.47 FCC Part 15： Section 15.231(a)

　　3Transmitter Radiated Spurious

　　EmissionC.F.R.47 FCC Part 15：Section 231(b)& 15.209

　　1. Transmitter 20dB Bandwith

　　1) 限值

　　Section 15.231(c)：The bandwidth of the emission shall be no wider than 0.25% of the center frequency for devices operating above 70 MHz and below 900 MHz. For devices operating above 900 MHz. Bandwidth is determined at the points 20 dB down from the modulated carrier.可知，对于中心频率工作在433.92MHz的设备，其20dB Bandwith限值是1.08MHz。

　　2) 测试场景

　　3) 测试方法

　　A. The transmitter output(antenna port) was connected to spectrum analyzer.

　　B. Set spectrum analyzer's RBW and VBW to applicable value with Peak in Max Hold.

　　C. A PEAK output reading and 20dB BW function in spectrum analyzer were taken.

　　2. Time Measurement

　　1) 限值

　　Section 15.231(a)(1)：A manually operated transmitter shall employ a switch that will automatically deactivate the transmitter within not more than 5 seconds of being released.

　　2) 测试场景

　　3) 测试方法

　　A. The transmitter output(antenna port) was connected to spectrum analyzer.

　　B. Set the center frequency is 433.92MHz and set the span is 0Hz.

　　C. Set spectrum analyzer's RBW and VBW to applicable value with Peak.

　　D. Read the time from transmission to silent from the spectrum analyzer directly.

　　3. Transmitter Radiated Spurious Emission

　　1) 限值

　　Section 15.209(a)

　　Section 15.231(b)

　　2) 测试场景

　　3) 测试方法

　　A. In the frequency range of 9kHz to 30MHz, magnetic field is measured with Loop Test Antenna. The Test Antenna is positioned with its plane vertical at 1m distance from the EUT. The center of the Loop Test Antenna is 1m above the ground. During the measurement the Loop Test Antenna rotates about its vertical axis for maximum response at each azimuth about the EUT.

　　B. In the frequency range above 30MHz, Bi-Log Test Antenna (30MHz to 1GHz) and Horn Test Antenna (above 1GHz) are used. Test Antenna is 3m away from the EUT. Test Antenna height is varied from 1m to 4m above the ground to determine the maximum value of the field strength, the azimuth range of turntable was 0o to 360o, the receive antenna has two polarizations horizontal and vertical. When doing measurements above 1GHz, the EUT was placed within the 3dB beam width range of the horn antenna, and the EUT was tested in 3 orthogonal positions as recommended in ANSI C63.4 for Radiated Emissions and the worst-case data was presented.

　　注：1)中给出的限值是平均值(AV值)限值，而测试时使用的检波方式是峰值检波(PK值)，根据Section 15.231(b) (2) If average emission measurements are employed, the provisions in §15.35 for averaging pulsed emissions and for limiting peak emissions apply.

　　故有：

　　Emission_AV = Emission_PK +AV Factor

　　AV Factor=20lg(The duration of one cycle)/(Effective period of the cycle)