Backscatter Antenna Beamforming Using Impedance Switching
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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 transmitting power is restricted, limiting their usability.
Innovation Solution
A wireless communication node employing multiple antennas with impedance matrices and switch controllers to generate beamformed signals through phase modulation of received RF signals, increasing the transmitting range without the need for power-hungry components like power amplifiers.
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 efficiency is improved, but transmitting power is reduced
Solution Approach 1:
The patent combines multiple antennas (A antennas) to work together in a coordinated manner, where each antenna contributes to the overall transmitted signal. By merging the signals from multiple antennas with constructive phase alignment, the system achieves power gain proportional to the number of antennas, resolving the contradiction between low power consumption and insufficient transmitting power.
Solution Approach 2:
The patent introduces the dimension of signal phase control across multiple antennas. By controlling the phase of each antenna's backscattered signal and aligning them constructively in the desired direction, the system transforms the problem from single-antenna isotropic radiation to multi-antenna directional beamforming, achieving higher effective transmitting power without increasing individual antenna power consumption.
2Power
If the number of antennas is increased to boost transmitting power, then transmitting power is improved, but device complexity is worsened
Solution Approach 1:
The patent employs a self-service approach where the system performs automatic beamforming training and phase alignment without requiring complex external control infrastructure. The device autonomously determines optimal beam directions and phase configurations through training sequences and feedback mechanisms, reducing the need for complex external control systems while managing multiple antennas.
Solution Approach 2:
The patent segments the beamforming control into independent per-antenna phase control units. Each antenna can be controlled independently with its own phase shifter, allowing modular expansion of the antenna array while maintaining manageable complexity. This segmentation enables scalable deployment where additional antennas can be added without fundamentally redesigning the control architecture.
3Length of stationary object
If beamforming is implemented to extend transmitting range, then transmitting range is improved, but device complexity is worsened
Solution Approach 1:
The patent implements feedback mechanisms where the receiving device provides feedback information about signal quality, channel conditions, and preferred beam directions to the transmitting device. This feedback enables the passive/semi-passive device to adjust its beamforming parameters dynamically, optimizing transmitting range while keeping the complexity manageable through adaptive rather than exhaustive control strategies.
Solution Approach 2:
The patent performs preliminary beamforming training before actual data transmission. During this training phase, the system pre-determines optimal beam directions and phase configurations based on channel conditions. This preliminary action allows the system to establish effective beamforming parameters in advance, extending transmitting range while avoiding the need for complex real-time adjustments during data transmission.
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, allowing for a power gain of up to 6 dB by aligning phases and doubling the number of antennas, while 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
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
Data Source
AI summary
A wireless communication node and method therein for generating beamformed signals by means of backscattering in a wireless communication network are disclosed. The wireless communication node receives a radio frequency signal at a plurality A of antennas. Each antenna is coupled to one of a number of impedance matrices by one of a plurality A of switches. The wireless communication node generates a first baseband signal based on data symbols to be transmitted in a baseband signal generator. 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.