MC13190FC Freescale Semiconductor, MC13190FC Datasheet - Page 18

• Manufacturer Part Number: MC13190FC
• Manufacturer: Freescale Semiconductor

Specifications of MC13190FC

• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Lead Free Status / Rohs Status: Compliant

Application Information
MC13190 makes it susceptible to frequency selective fading through the “notching” of the carrier causing
performance degradation in the envelope detector. These effects cannot be avoided so must be dealt with in
protocol design. Sufficient margin must be built into the link and redundancy into the protocol to reduce bit
error rate to an acceptable level.
3.6.3 Packet Structure
The 5 Mbps data rate that the MC13190 supports is high enough to allow multiple users to occupy the
same frequency channel using time division multiple access (TDMA) techniques. The protocol for
implementing the TDMA is left up to the system integrator and is heavily dependent on the number of
users per unit area, the amount of data to be transmitted per user per unit time and the method used to
detect the symbols.
The high level frame structure should allow for the total number of users required as well as the number of
retransmissions allocated to each user with a guard band between each packet to allow for the timing
uncertainty associated with each of the users clocks. The upper bound of the frame structure is determined
by the desired data throughput for each user and the latency of the data. If low latency is the primary design
goal, a short frame should be used.
The packets should be structured to provide for a robust synchronization between the transmitter and the
receiver as well as a means to deliver the payload reliably with some level of error detection or correction.
The packet should be designed with a preamble of at least 8 bits to allow for transceiver settling, a
synchronization code, a header, the payload, and the error detection overhead. A suitable form of error
detection could be an N-length CRC calculated and appended to the packet.
A common method of synchronization used in the industry is to transmit a length of a code that has been
designed to provide for fast acquisition of the codeword yet low probability of false detection. The ideal
code word has a very low autocorrelation side lobe. That is to say, when the codeword is shifted the
correlation value is very low. A Barker or Neuman-Hofman code could be used and are well documented
in most digital communication texts.
The MC13190 receiver outputs a waveform that has no timing associated with it. In other words, the
baseband symbol detector will need to determine the waveform timing in order to make the correct bit
decisions on the sampled waveform. Since the transmitted date is Manchester encoded, it is recommended
that the input waveform be at least 8X oversampled so that there are at least 4 samples per half of the
waveform. The correlation with the synchronization word should be performed on all samples of the
waveform, but it is recommended that the bit decisions be based only on the second half of the Manchester
encoded waveform since a transition is guaranteed at the middle of each transmitted bit. It should be noted
that an artifact of the MC13190 baseband filtering is some corruption of the first half of the Manchester
encode bit cycle as well. 8X oversampling should provide for adequate timing resolution of the bit edge
transitions to insure correct bit decisions if the packet length is not too long. The packet length will be
limited primarily by the accuracy of the reference clocks in the system. If the reference source has a
guaranteed stability of 50 ppm, then a worst case timing shift will be 100 ppm or up to 20 ps per 200 ns bit.
This would limit the packet length to 250 µs before the accumulated timing drift will begin to affect the
symbol detection. A method of coherent detection could be employed where a tracking loop is
implemented if longer packers are desired.
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MC13190 Advance Information
MOTOROLA