TDA5250D2 Datasheet, PDF (80/97 Pages) Infineon Technologies AG – ASK/FSK 868MHz Wireless Transceiver

confidential
TDA 5250 D2
preliminary
Applications
In the following figures the RF power level shown is the average power level.
These investigations have been made on an Infineon evaluation board using a
data rate of 4 kBit/s with manchester encoding and a data filter bandwidth of
7 kHz. This is the standard configuration of our evaluation boards. All these
measurements have been performed with several evaluation boards, so that
production scattering and component tolerances are already included in these
results.
Regarding the data filter bandwidth it has to be mentioned that a data rate of
4 kBit/s using manchester encoding results in a data frequency of 2 kHz to
4 kHz depending on the occurring data pattern. The test pattern given by the
AMIQ is a pseudo random binary sequency (PRBS9) with a 9 bit shift register.
This pattern varies the resulting data frequency up to 4 kHz.
The best sensitivity performance can be achieved using a data filter bandwidth
of 1.25 times the maximum occuring data frequency.
The IQ filter setting is depending on the modulation type. ASK needs an IQ filter
of 50kHz, 50kHz deviation at FSK recommend a 100kHz IQ filter and 100kHz
deviation were measured with a 150kHz IQ filter
A very practicable configuration is to set the chip-internal adjustable IQ filter to
the sum of FSK peak deviation and maximum datafrequency. Concerning these
aspects the bandwidth should be chosen small enough. With respect to both,
the crystal tolerances and the tolerances of the crystal oscillator circuit of
receiver and transmitter as well, a too small IQ filter bandwidth will reduce the
sensitivity again. So a compromise has to be made. For further details on chip
tolerances see also Section 4.2.7
Wireless Components
4 - 40
Specification, July 2002