# Radio System Architecture

The RSL15 system is built around a radio system architecture that supports the implementation of Bluetooth and other proprietary RF protocol stacks.

The most common use case for RSL15 devices is in applications that use Bluetooth technology.

The 2.4 GHz radio front-end is based on a low-IF architecture, and is comprised of the following building blocks:

- High performance single-ended RF port that alleviates the need for an external balun
- On-chip matching network with 50 Q RF input
- Low power LNA (low noise amplifier) and mixer
- PA (Power Amplifier) with up to +6 dBm output power for Bluetooth
- RSSI (Received Signal Strength Indication) with 60 dB nominal range in 1 dB steps (not considering AGC)
- Fully integrated ultra-low power frequency synthesis with fast settling time, featuring direct digital modulation in transmission (pulse shape programmable)
- Configurable direct access to streamed radio data, including ADC and RSSI data, or I/Q samples for signal phase measurements
- 48 MHz XTAL oscillator
- Fully-integrated FSK-based modem with programmable pulse shape, data rate, and modulation index
- Digital baseband (DBB) with link layer functionalities, including automatic packet handling with preamble and sync, CRC, and separate RX and TX 128-byte FIFOs
- 2.4 GHz radio front-end, containing a full transceiver with the following features:
  - IEEE 802.15.4 chip encoding and decoding
  - Manchester encoding
  - Data whitening
- Highly-flexible digital baseband — in terms of modulation schemes, configurability and programmability — supporting Bluetooth Low Energy technology, 802.15.4 OQPSK and DSSS, and proprietary protocols. This baseband allows for programmable data rates from 62.5 kbps up to 2 Mbps, and FSK with programmable pulse shape and modulation index.
- A simple baseband for direct packet handling for the 2.4 GHz radio front-end, which includes:
  - Automatic preamble and sync word insertion
  - Automatic packet length handler
  - Basic address check
  - Automatic CRC calculation and verification with a programmable CRC polynomial
  - Multi-frame support
- Time-of-Flight (ToF) — a proprietary mechanism that counts the number of system clock cycles between two configurable start and stop triggers

## RF Subsystem

The RSL15 2.4 GHz radio front-end implements the physical layer for the Bluetooth Low Energy standard, and for other standard, proprietary, and custom protocols. The modem is of the FSK type with a single-ended RF Port, which alleviates the need for an external balun.

The radio front-end operates in the worldwide deployable 2.4 GHz ISM band (2.4000 to 2.4835 GHz).

For more information about the RF front-end, see RF Front-End.

For HAL firmware information related to the RF front-end, see the RSL15 Firmware Reference: RFFE Radio Frequency Front End.

## Bluetooth Low Energy

RSL15 is Bluetooth 5.2 certified, with the following Bluetooth Low Energy features:

- Angle of Arrival (AoA) and Angle of Departure (AoD)
- Low Energy Long Range (LE Coded PHY)
- 2 Msym/s symbol rates (LE 2M PHY)
- Low Energy Advertising extensions
- High Duty Cycle Non-Connectable Advertising
- Low Energy Channel Selection Algorithm #2
- Advertising Channel Index
- GATT Caching
- HCI support for debug keys in Low Energy Secure Connections
- Sleep clock accuracy update mechanism
- ADI field in scan response data
- Host channel classification for secondary advertising
- Periodic Advertising Sync Transfer
- Backward compatibility and support for earlier Bluetooth Low Energy specifications including 5.1, 5.0, and 4.2

NOTE: 4.0 and 4.1 have been deprecated by the Bluetooth SIG.

The hardware enables implementation of custom protocols.

For more information about the Bluetooth baseband hardware, see Bluetooth Low Energy Baseband Controller. For more information about the Bluetooth stack, see the RSL15 Firmware Reference, and related 3rd party documentation provided from Riviera Waves for this product.

For HAL firmware information related to the Bluetooth baseband interface, see the RSL15 Firmware Reference: Baseband Interface.