The ATA5835 integrates a transmitter that is capable of sending data with various options:
- Frequency bands 310 MHz to 318 MHz, 418 MHz to 477 MHz, 836 MHz to 928 MHz
- Data rates up to 80 kBits/s Manchester or 160 Ksym/s NRZ in buffered and transparent mode
- ASK or FSK modulation
- Transparent or buffered mode
- ASK shaping filter
- Gauss-shaping digital filter
This section describes the hardware blocks that are integrated to perform the transmit functionality. For detailed information on system and software flows, refer to the ATA5835 UHF ASK/FSK Transceiver User’s Guide (DS50003152).
The following figure illustrates the transmit data path:
The transmission data source can be selected either from a register bit, the transparent input pin 16 (TMDI), or the TX modulator that fetches the data from the DFIFO and SFIFO.
If ASK/OOK modulation is selected, the data stream is used to directly switch the power amplifier on and off. The transmitted carrier frequency is set by the PLL frequency synthesizer.
If FSK modulation is selected, the data stream is used to switch between two frequencies that are generated by the PLL frequency synthesizer. The power amplifier is constantly ON in this case. Power ramping (ASK shaping) can be used during on and off switching. To reduce the occupied bandwidth, a digital Gauss-shaping filter can be enabled. For data rates above 20 kHz Manchester or 40 kHz NRZ-coding, a digital preemphasis filter has to be enabled to compensate for the PLL loop filter.