Improve signal reception with antenna diversity using multiple high speed DACs

December 17, 2017 // By Clarence Mayott, Linear Technology
In modern wireless systems, numerous diversity techniques are used to maximize data throughput and improve transmission reliability. Time, frequency and code diversity techniques are used to transmit signals to multiple users simultaneously and to maximize the amount of data transmitted.

By transmitting at different times, on different frequencies, or with different binary sequences known as Gold codes, signals are produced so that they can be differentiated from each other and can be received error free. These techniques are widely known and have been perfected over decades of use.

These techniques can also be used with antenna diversity or spatial diversity. Antenna diversity involves using multiple antennas to transmit or receive a signal. Simple antenna diversity uses the antenna combination with the best performance to decode the signal. More complex versions of antenna diversity include MIMO (multiple input, multiple output) systems and beamforming applications, where multiple antennas are deployed at the transmitter and receiver to increase spatial diversity.

With multiple broadcasting antennas it is critical to have timing variation in the picosecond range between the digital to analog converters (DACs) on each channel. This requires DACs that can be synchronized together so that the transmitted data is broadcast simultaneously. With this criteria met, the system will be able to transmit identical data over multiple antennas to a common receiver, maximizing the likelihood of proper signal reception and minimizing the likelihood of dropping a signal from a transmitter.

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