Dirty Transmitter

NI Bluetooth Generation Toolkit 19.1 Help

Edition Date: October 2019

Part Number: 373432K-01

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The Bluetooth test specification document specifies the use of a non-ideal, or "dirty", transmitter, as a signal source for performing the receiver sensitivity tests. The dirty transmitter test parameters for basic Bluetooth packets are defined in Table 5.4 and Table 5.5 of the Bluetooth Test Specification, Radio Frequency Test Suite Structure (TSS) and Test Purposes (TP) specification 1.2/2.0/2.0+EDR/2.1/2.1+EDR/3.0/3.0+HS for single-slot and multislot packets. The dirty transmitter test parameters for enhanced data rate (EDR) packets defined in Table 5.9 of the Bluetooth Test Specification 1.2/2.0/2.0+EDR/2.1/2.1+EDR/3.0/3.0+HS. The dirty transmitter test parameters for low energy (LE) packets are defined in the following tables:

  • Table 6.2 of the Bluetooth Test Specification 4.0.0
  • Table 4.2 of Bluetooth Test Specification 4.2.0/4.2.2/4.2.3
  • Table 4.2, Table 4.6, Table 4.7, Table 4.10, and Table 4.11 of Bluetooth Test Specification 5.0.0

The dirty transmitter is implemented in the following two modes, the Standard Mode and the User Defined Mode.

  • The Standard mode applies all the standard dirty transmitter parameters.
  • The User Defined mode applies only the dirty transmitter parameters that are specified by the user.

Standard Mode

Let c be the number of consecutive packets per impairment set, p be the number of impairment sets, and u be the number of unique packets. The toolkit transmits the first c packets using the first impairment set, the next c packets using the second impairment set, and so on, until it uses the pth impairment set. If u >= c * p, this process is repeated until u packets are generated. If u < c * p, this process is repeated until u * (ceil(c*p/u)) packets are generated. After this, the toolkit periodically repeats the generation of these packets.

Note Note  While using the Generation Interactive Example for Bluetooth or CVI™, the number of unique packets must be a multiple of c * p. If the number of unique packets is not a multiple of c * p, you may see incorrect BER or PER results when you run the generator multiple times.

User Defined Mode

Use this mode to test the dirty transmitter for limited parameter sets. The following example is based on the number of unique packets, and the number of enabled dirty transmitter parameter sets.

Let x be the number of unique packets and y be the Dirty Tx Enabled Parameters Set [] enabled values in the array, then x = w * y + z, so each enabled parameter set is repeated w times, and the first set is repeated z times after w * y packets are generated.

Case one: z = 0, each enabled set is repeated w times, and the number of unique packets are exact multiples of the number of Dirty Tx Enabled Parameters Set [] size.

Case two: z ≠ 0, each set is repeated w times and the first enabled set is repeated z (remainder) times after w * y packets are generated.

If the number of unique packets is less than the number of enabled parameter set size, x < y, the first enabled parameter set is repeated x times.

Bluetooth Basic Rate

For single-slot packets, the dirty transmitter superimposes a synchronized sine wave frequency modulation (alternate packets switch phase between 0 and 180 degrees) with a deviation of ±25 kHz and a modulation frequency of 1.6 kHz to obtain the carrier frequency drift.

For multi-slot packets, the dirty transmitter superimposes a frequency modulation with a deviation of ±40 kHz and a synchronized sine wave modulation frequency (alternate packets switch phase between 0 and 180 degrees) of 500 Hz for three slot packets and 300 Hz for five slot packets to obtain the carrier frequency drift.

(Applicable to Standard Mode only) According to the Bluetooth test specification, the dirty transmitter changes the carrier frequency offset, modulation index, and symbol timing error for each 20 ms duration. The toolkits ceils this 20 ms duration for each impairment set, to an integral number of consecutive packets (c). For example, for a 3-slot basic rate packet, the number of consecutive packets per impairment set, c, is calculated as c = 20 ms/(slot duration * 3) = ceil (20 ms/(625 * 3 microseconds)) = 11. Thus, for 1-, 3-, or 5- slot packets, the toolkit uses each impairment set for 32, 11, or 7 consecutive packets (c). The test specification defines 10 impairment sets (p) for basic rate packets.

Bluetooth EDR

The dirty transmitter superimposes a frequency modulation with a deviation of ±10 kHz and a synchronized sine wave modulation period of 100 microseconds onto the signal, starting at the beginning of the differential phase-shift keying (DPSK) synchronization word, to obtain the worst-case transmitter carrier frequency stability. The frequency modulation alternately switches phase between 0 and 180 degrees for successive packets.

(Applicable to Standard Mode only) According to the Bluetooth test specification, the dirty transmitter changes the carrier frequency offset, modulation index, and symbol timing error for every 20 packets (c), and it defines 3 impairment sets (p) for Bluetooth EDR packets.

Bluetooth Low Energy

The dirty transmitter obtains a frequency drift over time by using frequency modulation with a deviation of ±50 kHz and a sinusoidal signal with a modulation frequency of 1250 Hz. The modulating signal is synchronized with the packets so that each alternating packet starts at 0 and 180 degrees of the modulating signal.

(Applicable to Standard Mode only) According to Bluetooth Test Specification 4.0, the dirty transmitter changes the carrier frequency offset, modulation index, and symbol timing error for every 50 packets (c), and it defines 10 impairment sets (p) for Bluetooth low energy packets. The test specification defines different sets of modulation index values for standard and stable modulation index types.

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