Signal Guide

Service Description Selection Bluetooth

Here you will find information about the selected service, along with measurement examples.

Bluetooth Theory & Details
Communication
Typical Frequency Range:

2400 – 2483.5 MHz (ISM-Band)

General:

Bluetooth is used for short distance communications between devices such as computers, peripherals, mobile phones, and PDAs. The communication method was developed in the 1990s by the Bluetooth Special Interest Group (SIG), a working group of five industrial companies, and first standardized by IEEE in 2002 (IEEE 802.15). Bluetooth version 4.1 was announced by Bluetooth SIG on December, 4th 2013.

Modulation: GFSK, DPSK, DQPSK

For 1 Mbit/s: GFSK (+/-140 kHz hub)
For 2 Mbit/s: π/4-DQPSK (Bluetooth version 2.0 onwards)
For 3 Mbit/s: 8-DPSK (Bluetooth version 2.0 onwards)
Transmitting and receiving combines TDD (time division duplex) and FDD (frequency division duplex). Frequency hopping with hops of 1 or 2 MHz after every timeslot. Timeslots spaced at 625 µs. 366 µs of the timeslot are used for a burst. The last timeslot is correspondingly truncated for multislot packets.

Bluetooth Measurement Examples
Spectrum
Every second channel is used in Inquiry mode (when searching for other Bluetooth devices in the vicinity). Thus, a search burst appears every 2 MHz with a gap around 2.42 GHz. The maximum value curve (red) retains all bursts that occurred consecutively.
Spectrogram
This operating mode only gives random “hits” with Bluetooth.
HiRes Spectrogram Full
Overview measurement. Shows bursts spaced at 1 ms which hop by 2 MHz. These hops are regular in Inquiry mode, whereas they are quasi random during operation, the sequence repeating periodically by 227.
HiRes Spectrogram Zoom
Section from HiRes Spectrogram Full. Shows an individual burst, length 366 µs at position -0.6 ms.
Persistence Spectrum
Light density display obtained from the same data as the HiRes Spectrogram Full. Shows the six bursts with position and the same frequency as in the examples above. Shows everything that occurred during the captured Time Span.
Magnitude
Obtained from the same data as the HiRes Spectrogram Full. Shows the six bursts as in the example above. The time sequence is captured exactly, the frequency assignments can be taken from the previous images.
Scope
Shows all the channels that are within the measurement channel bandwidth (CBW) of 32 MHz. The gaps indicate that the signal was outside the CBW at times, or was not transmitted.