Backscatter Antenna Beamforming for Longer IoT Transmission Range
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Solution Overview
Problem
Passive and semi-passive devices used for generating RF signals by backscattering face limitations in range due to low power of reflected waves, especially in unlicensed bands, where the transmitting power is restricted, resulting in limited usability.
Innovation Solution
A wireless communication node employing multiple antennas with adjustable impedance matrices and switch controllers to generate beamformed signals through co-phasing, which increases the transmitting range by aligning phases and doubling reflected power, while maintaining low power consumption without power-hungry components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If passive or semi-passive devices generate RF signals by backscattering, then power consumption is reduced, but the transmitting range is limited due to low reflected power
Solution Approach 1:
The patent combines multiple antennas (at least two antennas) into a single backscattering system to achieve beamforming. By merging the radiation patterns of multiple antennas and co-phasing their reflected signals, the system achieves constructive interference in specific directions, thereby extending the transmitting range while maintaining low power consumption through passive or semi-passive operation.
Solution Approach 2:
The patent applies beamforming to create directional signal transmission with enhanced power in specific directions rather than uniform omnidirectional transmission. By controlling the phase and amplitude of signals from multiple antennas, the system concentrates energy locally in desired directions, effectively extending range without increasing overall power consumption.
2Power
If the number of antennas is increased to extend transmitting range, then reflected power is doubled with up to 6 dB power gain, but device complexity increases
Solution Approach 1:
The patent divides the backscattering function across multiple independent antenna elements, each capable of reflecting RF signals. By segmenting the system into multiple antennas with individual impedance control, the patent achieves power gain through constructive interference while keeping each antenna element relatively simple in structure.
Solution Approach 2:
The patent employs dynamic impedance control through switch controllers that can adjust the impedance state of each antenna element in real-time. This dynamic adjustment enables beamforming and phase control, allowing the system to achieve higher reflected power in specific directions while maintaining flexibility in managing device complexity through software-controlled impedance switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the coverage and power efficiency of passive and semi-passive devices, achieving a power gain of up to 6 dB by doubling the number of antennas and maintaining low power consumption, suitable for IoT applications.
Implementation Method 1
The semi- or passive devices generate transmitting signals by using an antenna mismatched to the incoming RF carrier signal, thus reflecting or backscattering the incoming radio waves
Implementation Method 2
the received RF signal at each antenna is modulated by the first baseband signal and reflected
Implementation Method 3
Each switch controller is configured to generate a specific switch control signal for one of the plurality A switches by phase shifting the first baseband signal with an antenna specific phase
Implementation Method 4
The beamformed signals are thus generated by the plurality A of antennas by reflecting the modulated RF signals from each antenna
Data Source
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AI summary
A wireless communication node (130) and method therein for generating beamformed signals by means of backscattering in a wireless communication network are disclosed. The wireless communication node (130) receives a radio frequency signal at a plurality A of antennas (310). Each antenna is coupled to one of a number of impedance matrices (330) by one of a plurality A of switches (320). The wireless communication node (130) generates a first baseband signal based on data symbols to be transmitted in a baseband signal generator (340). The states of each switch are controlled based on its specific switch control signal such that each antenna impedance is selected among a number M of impedances, and thereby the received RF signal at each antenna is modulated by the first baseband signal with its specific phase and reflected. The beamformed signals are generated by the plurality A of antennas by reflecting the modulated RF signals from each antenna.