Signal Guide

Service Description Selection DECT

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

DECT Theory & Details
Communication
Typical Frequency Range:

1880 – 1900 MHz (Europe)

General:

Digital enhanced cordless telecommunications

Modulation: TDMA, GMSK, GFSK

Combination method. DECT uses MC (multi carrier): 10 RF channels; channel 10 at 1881.792 MHz; other channel numbers in decreasing order at 1.782 MHz intervals. DECT uses TDMA (time division multiple access) within a channel: 24 timeslots spaced 10 ms apart; 1 – 12 downlink, 13 – 24 uplink. DECT devices automatically look for the carrier that gives the best transmission quality (dynamic channel selection / allocation). DECT uses TDD (time division duplex) In full duplex mode for teleph-ony in 2 channels always separated by 5 ms and also on different frequencies. The bursts are GMSK or GFSK modulated (Gaussian minimum shift keying; Gaussian frequency shift keying). Up to 23 channels can be bundled for data transmissions. At least one channel must remain for the backward path.

DECT Measurement Examples
Spectrum
Overview of the DECT band from 1.88 – 1.9 GHz. All ten frequency channels are visible in the maximum value display (red); they are not necessarily all occupied at the same time. The bell shaped traces for GMSK/GFSK modulation are typical.
Spectrogram
Same frequency range as Spectrum. The device delivers a “snapshot” every 8 ms. All values within a spectrum are recorded simultaneously because the device captures the frequency range with a single FFT.
HiRes Spectrogram Full
The approx. 9.4 ms time span shown covers practically an entire DECT frame. The frequency span of 21.33 MHz covers the entire DECT frequency band. The record is gapless for both time and frequency. A busy burst can be seen at the start of the recording (circled red).
HiRes Spectrogram Zoom
Section from the same data as HiRes Spectrogram Full. The width of the frequency range shown remains at 21.33 MHz. The time axis, however, can be shifted as with a magnifier. The first busy burst is now highly resolved.
Persistence Spectrum
Based on the same data as HiRes Spectrogram Full. Shows the frequency of occurrence over about 9.4 ms in the entire DECT frequency band.
Magnitude
Time domain display based on the same data as HiRes Spectrogram Full. The bursts spaced at about 6 ms can be clearly seen. The display is without time gaps over the time span of approx. 9.4 ms. Longer recording times of up to 24 h and greater flexibility is possible in Scope mode.
Scope