0 Replies Latest reply on Dec 22, 2014 7:34 PM by liumin

    BLE RF Testing Specification Introduction

    liumin

      Basic RF Introduction

       

      Bluetooth devices operate in the unlicensed 2.4 GHz ISM (Industrial Scientific Medical) band. A frequency hop transceiver is applied to combat interference and fading.

      Bluetooth Smart technology operates in the same spectrum range (the 2.400 GHz-2.4835 GHz ISM band) as Classic Bluetooth technology, but uses a different set of channels. Instead of the Classic Bluetooth 79 1-MHz channels, Bluetooth Smart has 40 2-MHz channels. Within a channel, data is transmitted using Gaussian frequency shift modulation, similar to Classic Bluetooth's Basic Rate scheme, the bit rate is 1Mbit/s.

       

      Frequency Bands and Channel Arrangement

       

      The Bluetooth system operates in the 2.4 GHz ISM band. This frequency band is 2400 - 2483.5 MHZ.1.png

      Table 2.1: From”
      BLUETOOTH SPECIFICATION Version 4.1

       

       

      RF channels are spaced 2 MHz and are ordered in channel number k = 0, 2, 4, …,78 shown in Table2.1.

       

      RF Test item

       

      ·       TX

       

      1.   TRM-LE/CA/01/C Output Power

       

      For a BLE transmitter, the output power level at he maximum power setting shall be 0.01mW(-20dBm) to 10mW(+10dBm) as the below table 3.1 showing.

      1.png
      Table3.1: Power class from” BLUETOOTH
      SPECIFICATION Version 4.1”

       

      Test Condition

      • DUT transmits test packets with PRBS9
      • Packet length: 37
      • Frequency: Low, mid, high

       

      Pass Verdict

      • -20 dBm ≤ Pavg ≤ +10 dBm
      • PPK  ≤ Pavg + 3 dB

       

      2.   TRM-LE/CA/05/C Modulation Characteristics

       

      The Modulation is GFSK (Gaussian Frequency Shift Keying) with a bandwidth-bit period product BT=0.5. The Modulation index shall be between 0.45 and 0.55. A binary one shall be represented by a positive frequency deviation, and a binary zero shall be represented by a negative frequency deviation. The symbol timing shall be less than ±20 ppm.

      3.png

       

      Figure 2: From”
      BLUETOOTH SPECIFICATION Version 4.1”

       

      For each transmission, the minimum frequency deviation,Fmin = min{|Fmin+|,Fmin-}, which corresponds to 1010 sequence shall be no smaller than ±80% of the frequency deviation (fd) with respect to the transmit frequency Ft, which corresponds to a 00001111 sequence.

      In addition, the minimum frequency deviation shall never be smaller than 185kHz. The data transmitted has a symbol rate of 1 M/s.

      The zero crossing error is the time difference between the ideal symbol period and the measured crossing time. This shall be less than ±1/8 of a symbol period.

       

      Test Condition

      • For ∆f1avg
      • DUT transmits test packets with 37 octet packet
        payload
      • Sequence: 1111 0000
      • For ∆f2max and ∆f2avg
      • DUT transmits test packets with 37 octet packet
        payload
      • Sequence: 1010 1010
      • Frequency: Low, mid, high

      Pass Verdict

      • 225 KHz ≤ ∆f1avg ≤ 275 KHz
      • At least 99.9% of all ∆f2max frequency values
        recorded over 10 test packets must be greater than 185 KHz
      • (∆f2avg / ∆f1avg) ≥ 0.8

       

      3.   TRM-LE/CA/06/C Frequency offset and drift

       

      The deviation of the center frequency during the packet shall not exceed ±150 kHZ, including both the initial frequency offset and drift. The frequency drift during any packet shall be less than 50 kHZ. The frequency drift during any packet shall be less than 50 kHZ. The drift rate shall be less than 400 HZ/us.

      The limits on the transmitter center frequency drift within a packet are specified in the below table

      .

      2.png

      Figure
      3: From” BLUETOOTH SPECIFICATION Version 4.1”

       

      Test condition

      • DUT transmits test packets with 37 octet payload
      • Sequence: 1010 1010
      • Frequency: Low, mid, high

      Pass verdict

      • fTX – 150 KHz ≤ fn ≤ fTX + 150 KHz
      • | f0 – fn | ≤ 50 KHz
      • | f1 – f0 | ≤ 20 KHz and | fn – f(n-5) |
        n=6,7,8,…k ≤ 20 KHz

       

      ·       RX

       

      1.    RCV-LE/CA/01/C Receiver sensitivity

       

      The actual sensitivity level is defined as the input level for which a raw bit error rate (BER) of 0.1% is met.The receiver sensitivity shall be below or equal to –70dBm with any Bluetooth transmitter compliant to the transmitter specification.

       

      Test condition

      • DUT is set to receive at the frequency for
        testing
      • The tester transmits test packets with PRBS9 (37
        octets)
      • Frequency: Low, mid, high
      • Signal level: -70dBm

       

      Pass verdict

      • PER better than 30.8 % for a minimum of 1500
        packets transmitted by the tester

       

      2.    RCV-LE/CA/06/C Maximum input signal level

      Maximum input signal level is the maximum permitted signal level inputting for RX receiver. DUT works in the low, middle and high frequency channel, tester send power controlled signal level of -10dBm, while a row bit error rate(BER) of 0.1% is met.

       

      Test condition

      • DUT is set to receive at the frequency for
        testing
      • The tester transmits test packets with PRBS9 (37
        octets)
      • Frequency: Low, mid, high
      • Signal level: -10dBm

       

      Pass verdict

      • PER better than 30.8 % for a minimum of 1500 packets transmitted by the tester

       

       

      3.    RCV-LE/CA/07/C PER report integrity

       

      PER tests are based on counting the number of packets received by the EUT out of a series of consecutive test packet transmitted by the testers. The tester is performed with frequency hopping disabled.

      PER= (1-Number of packets received by the
      EUT passing CRC/Total number of packets transmitted by the test).100%

       

      Test condition

      • DUT is set to receive at the frequency for
        testing
      • The tester transmits test packets with PRBS9 (37
        octets)
      • Total number of packets transmitted by the
        tester shall be an even random number in the internal between 100 and 1500
      • Every alternating packet transmitted by the
        tester shall have an intentionally corrupted CRC value
      • Signal level: -30dBm

      Pass verdict

      • 50% ≤ PER ≤ 65.4% for each individual measurement