Abstract
This letter presents a novel concept of beam-steerable transponder based on antenna array and phased modulators. The steerability of the beam is achieved by optimally delaying the modulated reflected signal at each antenna element (i.e., changing the phase in frequency domain) with load modulation technique. In this manner, the reflected backscattered signal power can be maximized at one particular direction. The approach makes transponder to collect ambient waves from any direction and further modulate and redirect it to any other direction. The results obtained through experimentation proves the feasibility of omnidirectional transponder and pave way for future lower power smart devices. The transponder functions in the Wi-Fi frequency band of 2.4 GHz.
Highlights
M ODULATED backscatter method has rapidly become modus operandi for low-power wireless communication systems [Internet of Things, wireless sensor networks (WSNs)]
We can have a transponder that receives the ambient RF wave from any direction and further modulates and redirects it to any other direction depending on the backscatter receiver position
The modulated backscattered signal is proportional to the difference of the reflection coefficients |ρs − ρo| of the two load impedances [13]–[15]
Summary
M ODULATED backscatter method has rapidly become modus operandi for low-power wireless communication systems [Internet of Things, wireless sensor networks (WSNs)]. Isotropic transponders receive signals from all directions almost well and spreads the rescattered energy evenly across the sphere. The benefit of this approach is its simplicity. The previous literature has introduced methods to maximize backscattered power in monostatic case for instance by using the well-known Van Atta array [4] and PON array [5]. They are less common in low-power applications due to power hungry components [6], [7]. We explain the operation principle with an analytical model and experimentally demonstrate the concept with a novel transponder designed for the purpose
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