It is foreseen that the commercial service of the fifth-generation (5G) of mobile communications will be launched on a worldwide scale starting in 2020. The application of the Internet of Things as an important part of the fifth-generation of mobile communication has a very broad development prospect [1]. At present, wireless sensors in IoT devices are facing two major problems: power consumption and transmission distance [2]. The server’s increasing demands are driven by various intelligent devices, such as smart meters, telemedicine, virtual reality, and autonomous driving, all of which include a lot of wireless sensor devices. With the growth of these mobile Internet services, the requirements for sensor power consumption have become increasingly higher. Currently, short-range wireless communication methods mainly include near-field communication (NFC), Bluetooth, and Zigbee, and most of these methods mainly work with frequency types such as S-band. A metasurface, composed of sub-wave-length resonators in 2-D plane [3–6], can provide a new way to control electromagnetics (EM) in terms of propagation modes, polarization, and wave-fonts [7–12], and recently an active anisotropic metasurface whose reflection phases can be electrically and independently tuned for two orthogonal polarized waves was reported [13]. Due to their unique EM properties, we propose a passive transmitter, using a reconfigurable metasurface design work in 2.4 GHz, to reduce the transmitter’s power consumption and to make the metasurface compatible with the standard IEEE 802.11ac. IEEE 802.11ac is a wireless networking standard in the 802.11 set of protocols (which is part of the Wi-Fi networking family), providing high-throughput wireless local area networks (WLAN) on the 2.4 GHz and 5 GHz band.

In this paper, a single layer reconfigurable metasurface has been presented with the aim of reducing power consumption. The proposed geometry consists of periodic metallic Patterns imprinted on the top of the dielectric substrate, where varactor diodes are mounted in the center of each unit cell. The reconfigurable metasurface has been constructed such that it can integrate two different characteristics (single band reflection and transmission) with independent control of the biasing states of the varactor diodes. In order to communicate with the passive transmitter a receiver has been designed with a software-defined radio (SDR) [14–18]. A software-defined radio is a radio communication system where components that have been traditionally implemented in hardware are instead implemented by means of software on a personal computer or an embedded system. While the concept of SDR is not new, the receiver in this paper only provided a method to verify this design. The varactors in the reconfigurable metasurface are controlled by the base band signal.

The remainder of this paper is organized as follows. Section 2 presents the proposed design concept for a passive transmitter, then describes the system composition and characteristics of power consumption. Section 3 discusses the theoretical investigation of this design and show the simulation results. Finally, concluding remarks and a comparison of the proposed passive transmitter to the traditional short-range wireless communication methods are presented in the last section.

To verify the performance of the proposed metasurface, Frequency domain simulations are performed using the CST studio and GNUradio software. In our Simulations, the unitcells are driven by the horizontal polarized wave from 1.5 GHz to 3 GHz. The reflection and transmission coefficient are shown in Figure 4 and Figure 5. As an illustrative example, we find that the reconfigurable metasurface worked at 2.4 GHz by adjusting the biasing voltage, and the EM resonance changes as expected.

Furthermore, we simulated the reconfigurable metasurface’s farfield properties. From the farfield simulation results, it can be intuitively seen that the main lobe of the reconfigurable metasurface covers half of the space and the amplitude of the backward radiation is very low. In this case, its farfield reflection properties can be well modulated.

Particularly, the reflectivity and phase difference of the two elements under the illumination of forward x-polarized incidence are depicted in Figure 6, respectively. It is clearly shown that the complete reflection with direction difference approximately approaching 180°, is well kept in 2.4   G H z . The transmitter is composed of 9 × 5 unitcells. Since the varactor diodes works at 0v and 28 V reverses the bias state, its reverse current is about 10   n A , the power consumption of a single structural unit is about 300   n W , and its total power consumption is less than 1   m W . The power consumption comparison of communication is shown in Table 1.

Based on the design proposed above, we can combine it into a new communication system. The reconfigurable metasurface whose biasing voltage are controlled by the base band signal plays the role of transmitter. The continuous wave radar designed by GNUradio is used as a receiver. In this communication system the transmitter does not radiate any EM wave, which is of great significance for EM silence. In IoT applications, a large part of the sensor data transmission is unidirectional, and the power is limited. The passive trans proposed in this paper may solve these problems.

In summary, we provided a theoretical framework for modulation, and simulated a prototype system tailored to the use of ambient commodity 2.4   G H z Wi-Fi signals. The proposed design is comprised of switchable active comments mounted across the metallic grids, and with base band control of the biasing conditions of the varactor diodes, the metasurface realized different modes of operation. For different biasing voltages the reconfigurable metasurface showed different electromagnetic characteristics, and then used these characteristics to achieve information transmission and reduced the power consumption of this kind of transmitter. At present, traditional short-range communication methods such as Bluetooth consume more than 10 mW. The passive transmitter based on a reconfigurable metasurface proposed in this article works in the reverse bias state of the varactor. The power consumption is therefore less than 1 mW and the distance of communication depends on the receiver’s resolution. It will also have applicational prospects in confidential communications. We believe that our passive transmitter, based on a reconfigurable metasurface, provides a fundamentally new view on wireless communication systems that can impact a wide range of future passive and IoT communication systems at radiofrequencies.