ISM 868 MHz, 433 MHz and 315 MHz FSK Transmitter – Preliminary Data Sheet

ASCell3911

Rev. A, February 2000

Page 4 of 13

Austria Mikro Systeme International AG

Note: CRYSTAL and RANGE are bits of the control information.

1.2 Microprocessor Clock

Note: CRYSTAL is one bit of the control information.

1.3 Modulation

The SC3011 uses FSK modulation with a frequency deviation of

≈60 kHz at a gross data rate

from 18,25 kbit/s for the 868,300 MHz ISM band.

In the transmitter, the data from the pulse interference resistant protocol encoder is first trans-

formed into a complex base-band signal in the sin/cos block. After filtering it is shifted up to RF in

an I/Q based direct conversion transmitter.

1.4 Burst interference Resistant Protocol Encoder

In order to avoid disturbance due to pulsed interferes, e.g. GSM phones, the net data block is

encoded with a special protocol. Up to two simultaneous GSM disturbers can be handled by

adding redundancy to the FSK data in a suitable manner.

The 128 bits of a message (net data block) are put into a transmission sequence that alternates

a synchronization packet and data packet at transmission as shown in Figure 2.

To form a data packet, the 128 bit net data the information is split in 16 bytes where a bytenum-

ber and a parity is added to generate 14 bit words. Therefore the 128 bits of net data are ex-

panded to the 224 bit long (gross) data packet. The synchronization packet is simple 0101-

sequence of 252 bit.

Transmission Protocol

W

Word Pattern in Data Packet

Data Packet

W

SYNC

0-1-Sequence

Bit Pattern for SYNC

0 1 0 1 0 1 . . .

. . . 0 1 0 1 0 1

Data Packet

W

SYNC

0-1-Sequence

12.28 ms

13.81 ms

Figure 2:

Transmission protocol of the ASCell3911.