This letter presents a 28 GHz switched five-beam antenna system based on a rectangular waveguide and a reconfigurable semiconductor circuit (RSC) with slots. Surface p-i-n diodes are used to close or open slots in order to achieve required configuration of an aperture. The RSC with a modified WR28 waveguide composes a reconfigurable radiating structure (RRS), which provides three beams directed toward 0°, 30°, and 45°. Beam switching is achieved by reconfigurable arrangement of a set of slots. Complementary RRSs connected to the electromechanical RF switch is used to generate remaining -30° and -45° beams. The gain of each generated beam is similar because different numbers of slots are opened, i.e., three, five, and nine slots for beams directed toward 0°, 30°, and 45°, respectively. Aperture of the antenna is controlled by a unit composed of high-current operational amplifiers. Measured results validate the performance of designed millimeter-wave reconfigurable antenna.

In this letter, a novel architecture for a time-modulated antenna array (TMAA) based on single-pole double-throw (SPDT) switches is presented. The proposed TMAA has lossless switching network because there is no power loss during the off state. In addition to improved efficiency, this TMAA provides beam-scanning capabilities. Moreover, the proposed TMAA has a constant instantaneous directivity, which is favorable for some applications. The architecture has been implemented as an aperture-coupled patch antenna array and verified as a smart antenna in a digital wireless communication system.

This paper presents a design of a time modulated antenna array (TMAA) with substantially wider bandwidth and higher efficiency than have been already presented in the literature. The TMAA is designed for 5.4–5.8 GHz frequency band. More than 50 MHz of channel bandwidth is achieved by utilization of ultra fast microwave switches, digital delay lines with 60 ps step, and fast control circuitry. The efficiency is improved by alternate switching between array elements instead of switching between the array element and a matched load. Moreover, a mathematical derivation of optimal switching sequence is given. The beam-steering at the first sideband frequency was obtained with a 1 degree step in a range from –50 to 50 degrees. The TMAA has been evaluated by means of the radiation pattern measurements at different sideband frequencies.

The Internet of Things (IoT) denotes a concept of connected devices that communicate seamlessly over the Internet. The wireless connectivity between IoT nodes and the Internet gateways can be realized in unlicensed frequency bands upon the low-power wide-area network (LPWAN). It is foreseen that due to a massive introduction of IoT devices the unlicensed bands will experience an increased interference level which will negatively affect the communication performance. Therefore, adaptive solutions should be considered to obtain robustness. This letter presents a time-modulated antenna array (TMAA) for LPWAN receivers and demonstrates its interoperability with a commercial of-the-shelf LoRa device. According to the conducted experimental investigation, whereby the beam-steering is obtained over the sidebands inherently generated by the TMAA, both the received signal strength and the signal-to-noise ratio (SNR) are improved by means of the progressive delay applied to the time modulation functions.

In this paper, an adaptive antenna system (AAS) based on a time-modulated antenna array (TMAA) and population-based metaheuristic algorithm is presented. The algorithms is driven by the signal-to-noise ratio measurements and provides real-time adaptation of the antenna pattern. This paper also addresses the issue of multi-band reception with a TMAA, demonstrating that the sidebands generated from frequency-diverse signals can overlap and interfere. The effectiveness of the AAS as part of a wireless communication system is presented in three different experimental scenarios that consider gradually or rapidly changing conditions as well as the interference caused by the reception of two signals with different carrier frequencies.

This paper presents results of investigation on the radiation pattern generated with two-element Time Modulated Linear Array with single SP4T microwave switch. Utilization of SP4T switch instead of multiple SPST switches reduced an amount of power dissipated in matched loads and increased total efficiency. Due to the pulse-delay approach the null of radiation pattern has been continuously steered in a wide range of angles.