Longer Range Backscatter Communications for IoT
Wireless communication technologies have gained widespread adoption, forming the foundation of the Internet of Things (IoT). The IoT offers versatile, accurate, cost-effective, and energy-efficient solutions for a diverse range of applications. Within this network, backscatter communication plays a significant role. Expanding the operational range of backscatter systems holds the potential to unlock new application possibilities.
One of the limitations faced by the backscatter system is the presence of phase noise. A powerful method for phase noise cancellation is Range Correlation. To achieve maximum suppression of phase noise, it is crucial to match time delays between correlated signals. However, in backscatter communication, the transmission delays through free space may not remain fixed if the reading distance changes. To address this challenge, an interpolation method with several fixed taps and controlled weights is developed for generating desired delays.
The contribution of this Doctoral Thesis mainly consists of three parts.
- Phase noise suppression is fulfilled by using the range correlation effect at the receiver side. The possibility of extending the operational range with a spatially separated structure using a common local oscillator is also demonstrated. This approach allows for a potential range increase of up to 50 times.
- A delay matching block using interpolation methods is developed for optimum range correlation that maximise phase noise suppression. This three-tap block can generate arbitrary delays within its specified range and can be conveniently integrated into existing backscatter systems. When applied prior to range correlation, this block successfully suppresses phase noise by over 50dB at 100kHz offset.
- Special transmission lines are designed for shrinking the size of the delay matching block for easier deployment. The delay-to-length ratio is largely increased by 17 times.