Introduction to Radio Frequency RFID Testing For CE Certification of UHF RFID Equipment

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Previously, MORLAB has completed the testing and certification of several RFID products. Let's take a look at the RF test points of the next UHF band RFID.


At present, the UHF RFID operating frequency band used in Europe is between 865MHz and 868MHz, and the power does not exceed 2W. According to the R&TTE directive, the radio frequency test in the CE certification needs to refer to the harmonized standard EN302 208-2 for testing. Usually, a complete RFID system has two parts: RFID reader (Interrogators) and RFID electronic tags (Tags), and the tests of the two are also different.


The following is an introduction to the test of a scanner. The modulation method of this product is ASK, the power is 30±3dBm, and the effective working frequency points are: 865.7MHz, 866.3MHz, 866.9MHz, 867.5MHz.

The spectrum diagram under the working condition of the product

After a comprehensive evaluation of the customer's product by MORLAB engineers, the product is classified as a handheld RFID reader, and the following tests are required according to the standard:
1. Frequency error

Define f as the measurement frequency point in the normal working mode, fe as the frequency point with the maximum frequency drift amplitude, and the comparison between the two is the frequency error. When testing, you need to pay attention: first set the transmitter as a non-modulated carrier, use a frequency meter to measure and record each frequency point under various conditions, and then calculate according to the formula. The standard requires that the frequency error cannot exceed ±10ppm.

requency error =(f-fe)/f×106ppm

2. Frequency stability under low pressure

This test is mainly for battery-powered products to evaluate whether they can continue to work when they enter the extreme low-voltage power supply.

The test steps are as follows:

1. Set the transmitter to continuous transmission with non-modulated carrier, and correctly connect to the frequency meter.

2. Record various conditions, including frequency values ​​of extreme conditions.

3. Adjust the voltage of the power supply, continue to decrease from the extreme low voltage until 0, and record the condition of the transmitting frequency in the middle.

4. Record the operating voltage node when the transmission is stopped.

This test requires:

1. Under low voltage conditions, the operating frequency error does not exceed ±10ppm, and the transmit power is within the spurious limit.

2. The stop transmitting voltage must be lower than the operating voltage declared by the manufacturer.

Third, the test of the transmission power ERP

This test is similar to other RF product test ERP methods, divided into radiation mode test and conduction mode test. Usually the laboratory uses radiation mode to complete the test. Different from other RF products, the limit value is different:

1. Below 500mW erp, there is no restriction on the transmitter beam bandwidth.

2. For 500mW to 1000mW erp, the transmitter beam bandwidth does not exceed 180°.

3. For 1000mW to 2000mW erp, the transmitter beam bandwidth does not exceed 90°.

Refer to the following legal requirements:
The layout of the test is shown in the figure below:
Fourth, the emission spectrum

Define the average power of the carrier within the range of ±500KHz within the limit value. As shown below:
The test steps are as follows:

1. The transmitter works in the normal modulation mode, and the spectrum analyzer is equipped with an appropriate attenuator to sufficiently display useful signals.

2. Set the transmitter to keep working continuously, and each channel needs to be tested.

3. Set up the spectrum analyzer as follows:

a.Resolution bandwidth: 1 kHz.

b.Video bandwidth: Equal to the RBW.

c. Sweep Time: Auto.

d.Span: 1 MHz.

e.Trace mode: Max. hold sufficient to capture all emissions.

f.Detection mode: Average.

4. After the spectrum is stable, record the spectrum and make sure that its envelope is within the limit.

Five, spurious emissions

It is defined as the transmitter spurious emission outside the useful signal within ±500KHz of the main frequency signal, which is called out-of-band spurious emission.

The test is divided into two categories:

1. Products with external antenna ports:

a. Use the conduction method for spurious testing.

b. Use a simulated antenna instead of testing the radiation mode.

2. If there is no external antenna, it is a product with built-in antenna:

a. Use radiation to perform spurious testing.

The test of spurious emission requires the test working mode and standby mode, and the limits are different, as shown in the figure below:

6. Transmission time

It is defined as the period of continuous transmission of the transmitter, and the purpose is to verify whether it is effectively transmitting. By verifying the continuous launch time of the product and the stop launch time, it can be judged whether it meets the requirements in the standard. The continuous transmission time A cannot be greater than 4S, and the transmission gap B cannot be less than 100ms.

The test steps are as follows:

1. Arrange the EUT in a dark room according to the radiation test, and set the EUT on the channel with the highest power;

2. Prepare several (usually 3) typical labels and place them in the sensing area of ​​the EUT;

3. Place the sensor probe of the digital storage oscilloscope close to the antenna of the RFID transmitter to read the waveform;

4. Repeat the measurement several times and record the corresponding test waveform;

5. Take out the maximum launch time and launch gap and determine whether it meets the above restrictions.

Some application products (such as transmission device systems) also have some special requirements that need to be declared by the manufacturer:

a. If the RFID reader does not read the card within 20s, the transmitter will stop transmitting;

b. A trigger is needed to launch again;

c. The transmission after re-triggering shall comply with the transmission gap of 100ms before transmitting the original frequency of the same channel.

7. Receiver spurious

Defined as the spurious emission of the receiver, including harmonic radiation, parasitic radiation, intermodulation and frequency conversion, excluding out-of-band radiation. The requirements of this test are the same as those of emission spurious, and the test method is also the same.

The limit values ​​are as follows:

2 nW e.r.p. below 1 000 MHz;

20 nW e.r.p. above 1 000 MHz.

In the standard, it is also necessary to test the radiated power and stray power of the tags for tags (Tags) products. The above is an introduction to the RF radio frequency test of UHF UHF RFID products.

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