Analysis of Wireless Product Testing Requirements in IC Certification

    IC is the abbreviation of Industry Canada, which is the abbreviation of the Canadian Department of Industry. IC stipulates the testing standards for analog and digital terminal equipment, and stipulates that wireless products sold in Canada must pass IC certification. Therefore, IC certification is a pass and a necessary condition for wireless electronic products to enter the Canadian market.

    According to the relevant requirements of the standard RSS-GEN formulated by IC and the standard ICES-003e, wireless products (such as mobile phones) must comply with the relevant EMC and RF limits and meet the SAR requirements in RSS-102. Taking the GSM850/1900 module or mobile phone with GPRS function as an example, the EMC test includes RE radiated interference and CE conducted interference tests. In the SAR evaluation, if the actual use distance of the wireless module is more than 20cm, the radiation safety can be evaluated in accordance with relevant regulations using a method similar to the MPE defined in the FCC. Here we take the GSM850/1900Mhz GSM mobile phone as an example to talk about the RF radio frequency project in IC certification.

1. Output Power

    According to the GSM protocol, the EUT (herein, GSM terminal equipment) can have its transmit power controlled by the base station. The base station issues commands to control its transmit power level through the downlink SACCH channel, and each power level differs by 2dB. When the EUT is far away from the base station and the signal is weakened, the base station can command the EUT to send a higher power up to 33dBm (GSM 850 power level 5) to overcome the signal loss caused by long-distance transmission or building shielding. When the mobile phone is very close to the base station and the signal is very strong, the base station can command the mobile phone to send a lower power, up to 5dBm (GSM 850 power level 15), to reduce the interference of the mobile phone to adjacent users on the same channel and extend the battery life of the mobile phone. This test is to verify whether the EUT meets the requirements in the protocol. During the certification test, it is only necessary to test whether the maximum transmit power meets the requirements (the limit of GSM850MHz is 33±3dBm, and the limit of GSM1900MHz is 30±3dBm).

    Test method: Set up as shown below, use CMU200 or Agilent 8960 to establish a link with EUT, and the spectrum analyzer can be R&S FSU or Agilent spectrum analyzer.

    Take the FSU spectrum of R&S as an example. The FSU spectrum settings are as follows:

 1. Before testing, add the path attenuation calibration value from EUT to FSU to FSU;

 2. Set RBW=1MHz, VBW=1MHz. The specific settings are: FSU/BW/RES BW MANUAL and FSU/BW/VIDEO BW MANUAL;

 3. Set FREQUENCY SPAN=40 MHz. The specific setting path is: FSU/SPAN/SPAN MANUAL;

 4. Set SWEEP TIME=AUTO. The specific setting path is: FSU/BW/SWEEP TIME MANUAL;

 5. The center frequencies in the 850 band are set to 824.2 MHz, 836.6 MHz, and 848.8 MHz; the center frequencies in the 1900 band are set to 1850.2 MHz, 1880 MHz, and 1909.8 MHz. The specific setting path is: FSU/FREQ/CENTER;

     6. Press the "MAX HOLD" key to call out the required graph. The specific setting path is: FSU/TRACE/MAX HOLD;
 
       7. If the peak is too high to be displayed, you can set the value of REF LEVEL POSITION to display the entire waveform. The specific setting path is: FSU/AMPT/NEXT/REF ​​LEVEL POSITION;

 8. Take a Peak value on the waveform. The specific operation is as follows: press the "MKR→" key of the FSU, and press "PEAK" in the pop-up selection key;

    The test results are shown in the figure:

2. Occupied Bandwidth and Transmitted Bandwidth

    Occupied bandwidth refers to the bandwidth corresponding to 99% of the total transmitted power energy centered on the center frequency of the specified channel. Occupied bandwidth can also be defined as: Occupied bandwidth refers to a bandwidth in which the average power transmitted below the lower frequency limit and above the upper frequency limit of this band is equal to 0.5% of the total average power of a given transmission. If the occupied bandwidth is too narrow, the information will be distorted, and if the occupied bandwidth is too wide, adjacent channel interference will occur. Depending on the modulation method, there are two methods that can be used to calculate the occupied bandwidth. They are the power percentage method and the power reduction -26dB method.

    Power percentage method: The frequency bandwidth that contains a certain percentage of the total transmitted signal power is defined as the occupied bandwidth.

    Power drop -26dB method: The occupied bandwidth can also be defined as the distance between the two frequency points on both sides of the frequency point where the signal peak power is located when the signal power drops by -26dB respectively.

    Test purpose: To verify that the EUT transmission does not occupy too much bandwidth and cause adjacent channel interference.

    Test steps (taking the power percentage method as an example):

    Connect as shown in Figure 1 (the spectrum analyzer is replaced with an Agilent spectrum analyzer). Using the Occupied Bandwidth option on the Agilent spectrum analyzer, we can also measure the occupied bandwidth. The result is as follows:

3. Conducted Spurious Emission

    Spurious emissions are emissions of one or more frequencies outside the necessary bandwidth, and their emission levels can be reduced without affecting the transmission of the corresponding information. Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and frequency conversion products. Generally, conducted spurious emissions refer to any spurious emissions caused by the antenna connector or power leads. Out-of-band emissions refer to any emission outside the generally recognized operating frequency range, which must be at least 43 + 10log(P) dB lower than the transmission power (P in watts). Taking the transmission power level of GSM1900 as +30 dBm to 0 dBm, a constant limit of -13dBm can be obtained.

    Test method: Connect as shown in Figure 1 (the spectrum analyzer can be replaced by an Agilent spectrum analyzer), first calibrate the path attenuation from the EUT to the receiver or spectrum analyzer, and add the corresponding compensation value to the receiver or spectrum analyzer, and then set up the model as shown in the screenshot below.

    The test results are shown in the figure:

    Frequency Stability

    Each channel of the transmitter has a nominal RF center operating frequency, denoted by f0. The maximum deviation between the actual operating frequency and the nominal operating frequency is Δf, and the frequency stability is defined as:

    In the formula, K is the frequency stability, expressed in ppm (parts per million). It is one of the important indicators for measuring the quality of communication equipment.

    Test method: Since the universal base stations Agilent 8960 and R&S both have frequency stability test functions, when testing, you only need to directly connect the EUT and the base station and use the base station for testing.

    Test conditions: The frequency stability test should be carried out at an ambient temperature of -30° to +50° as follows:

 Under normal working voltage, place it in -30 °C environment for half an hour and then measure the value, then place it in -20 °C temperature environment for half an hour and then test the value, and then increase the temperature by 10 °C every time until it reaches 50 °C, and then test the value;

 Under high voltage and low voltage conditions, the test steps are the same as those under normal working voltage;

    In addition to the RF test items detailed above, typical RF test items also include Band Edge, Radiated Spurious Emission (RSE), Effective Radiated Power (EIRP) and other test items. All test items and their defined test methods and requirements in IC certification are similar to those of FCC.