MC13190FC Freescale Semiconductor, MC13190FC Datasheet - Page 17

• 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
3.6 Protocol Considerations
3.6.1 Manchester Encoding
As mentioned earlier, the MC13190 has been designed for use with protocols that employ Manchester
encoding. The basic principle of this coding technique is that each data bit is encoded as a transition as
opposed to a level. This results in two half-bits as shown in Figure 12. A data 1 bit is encoded as a high-
low transition while a data 0 bit is encoded as a low-high transition. Each data bit then has a transition
which facilitates data clock recovery. The half-bits are the transmitted and received symbols so each data
bit results in two channel symbols.
M
1
1
0
0
1
0
1
Data Bits
τ
= 200 ns
B
Channel Bits
τ
B
= 100 ns
2
Figure 12. Manchester Encoding of 5 Mbit Data
At 5 Mbps a data bit is 200 ns long. The channel bits are then 100 ns each but because of the encoding
algorithm there can be two half-bits in sequence when a data bit transition occurs. This is also the
maximum number of half bits that can occur in sequence.
Although the active filters in the MC13190 transmitter are designed for a specific data rate and Manchester
encoding, there is nothing to prevent the application from using other rates or encoding in just the
transmitter.
The transmitter uses slope control and low-pass filtering to control the bandwidth of the baseband signal.
These filters assume a 100 ns Manchester encoded half-bit with a tightly controlled duty cycle. TX_DATA
is dc-coupled so there is no limit on the length of the data bit. A data 1 or 0 can be maintained indefinitely.
If the pulse length at TX_DATA is much shorter than 100 ns, the slope control will not allow the
modulator to peak and the modulation index will decrease.
The receive filters are hard-wired for 5 Mbps Manchester encoded data as shown in Figure 12 and cannot
be changed by the user. These filters have bandpass response to maximize the performance of the receiver.
The receiver is ac-coupled. Using Manchester encoded data rates outside the range of 4 to 6 Mbps will
result in less than optimum performance. If the rate is too high or low, the data will fall out of the receiver
passband and performance will degrade quickly.
3.6.2 Channel Considerations
The 2.4 GHz band is a noisy environment prone to multipath fading. Noise takes many forms but, at 2.4
GHz, microwave ovens and other users predominate. Multipath fading occurs when the same signal arrives
at the receiver at different times. Not only can multipath impact the absolute signal level but it can also
result in frequency selective fading and intersymbol interference. The AM modulation scheme used in the
MOTOROLA
MC13190 Advance Information
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