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CC2400-RTR1 数据表(PDF) 53 Page - Texas Instruments |
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CC2400-RTR1 数据表(HTML) 53 Page - Texas Instruments |
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53 / 84 page ![]() CC2400 SWRS042A Page 53 of 83 46 System Considerations and Guidelines 46.1 SRD regulations International regulations and national laws regulate the use of radio receivers and transmitters. SRDs (Short Range Devices) for license free operation are allowed to operate in the 2.45 GHz bands worldwide. The most important regulations are EN 300 440 and EN 300 328 (Europe), FCC CFR47 part 15.247 and 15.249 (USA), and ARIB STD-T66 (Japan). The CC2400EM reference design complies with EN 300 440. If frequency hopping is to be used at 1 Mbps data rate, GFSK should be selected to keep the bandwidth below 1 MHz. The CC2400 complies with EN 300 440 class 2 if the band spacing is 2 MHz or more. It complies with EN 300 440 class 1 if the channel and band spacing is 10 MHz or more. Please note that compliance with regulations is dependent on complete system performance. It is the customer’s responsibility to ensure that the system complies with regulations. 46.2 Frequency hopping and multi- channel systems The 2.400 – 2.4835 GHz band is shared by many systems both in industrial, office and home environment. It is therefore recommended to use frequency hopping spread spectrum (FHSS) or a multi- channel protocol because the frequency diversity makes the system more robust with respect to interference from other systems operating in the same frequency band. CC2400 is highly suited for FHSS or multi- channel systems due to its agile frequency synthesizer and effective communication interface. Using the packet handling support and data buffering is also beneficial in such systems as these features will significantly offload the host controller. Due to the low-IF I/Q receiver and the on- chip complex filtering, the image channel will be significantly rejected. This is important for all 2.4GHz systems. 46.3 Data burst transmissions The high maximum data rate of CC2400 opens up for burst transmissions. A low average data rate link (say 10 kbps), can be realized using a higher over-the-air data rate. Buffering the data and transmitting in bursts at high data rate (say 1 Mbps) will reduce the time in active mode, and hence also reduce the average current consumption significantly. 46.4 Continuous transmissions In data streaming applications the CC2400 opens up for continuous transmissions at 1 Mbps effective data rate. A typical application is digital audio systems. As the modulation is done with an I/Q up- converter with LO I/Q-signals coming from a closed loop PLL, there is no limitation in the length of a transmission. (Open loop modulation used in some transceivers often prevents this kind of continuous data streaming and reduces the effective data rate.) 46.5 Crystal drift compensation A unique feature in CC2400 is the very fine frequency resolution using the MDMCTRL.MOD_OFFSET[5:0]. This feature can be used to compensate for frequency offset and drift. The compensation affects both the receiver and the transmitter of the device being compensated. I.e. the received signal of the device will match the receiver’s channel filter better. In the same way the center frequency of the transmitted signal will match the ‘external’ transmitter’s signal. Initial adjustment can be done using this frequency programmability. This eliminates the need for an expensive TCXO and trimming in some applications. The frequency offset between an ‘external’ transmitter and the receiver is measured in the CC2400 and can be read back from an internal register (FREQEST.RX_FREQ_OFFSET[7:0]). |
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