This paper examines and analyzes the existing standards NB-IoT, LoRA, Wi-Fi HaLow (802.11ah) used in wireless networks of Low-power Wide-area Network (LPWAN). Also, the paper reviews main applications of wireless networks of three different standards. The main features of these standards are analyzed, their pros and cons are determined.

Miniaturization of microwave devices such as couplers, filters, switchers etc. is an important practical problem due to the tendency of integration of portable and small high-frequency electronics. This article is dedicated to the investigation of the central frequency influence on the miniaturization efficiency of a microstrip branch-line coupler. Simulation of couplers with central frequencies of 1000, 1500, 2000, 2500 and 3000 MHz was made to obtain transmission coefficients. Analysis of the simulation results is conducted.

The cylindrical Luneburg lens under analysis has a radially inhomogeneous layered structure. The influence of the number of layers on lens radiation parameters is investigated. Four types of lenses discretization are considered. For each type antenna directivity is analyzed. Radiation patterns of three-layered Luneburg lens and 3-w ave length outer radius are shown. To calculate radiation patterns and antenna gain a model based on cylindrical Green's functions for layered inhomogeneous cylindrical structures was used. A model of equivalent radial lines, in which voltages and currents are associated with the spectral components of the electromagnetic field, is used for the analysis. In addition, for the solution transfer and boundary matrices are used and boundary conditions are modeled by end loads. The optimal method of cylindrical Luneburg lens layer's permittivity and thickness choice is suggested.

A miniaturized branch-line coupler based on lowpass microstrip filters instead of conventional transmission lines is presented in this paper. The design of proposed couplers is performed using lowpass filter of 5th, 7th and 9th order. This is done to achieve a compact circuit layout in microstrip implementation. Prototypes with these proposed structures, operating at 2 GHz frequency, have been designed and implemented using microstrip technology.

This article is dedicated to the new procedure of synthesizing microwave devices which provides size reduction of conventional microstrip structures. In the proposed method traditional transmission lines are replaced with microstrip lowpass filters having the same phase response on the frequency of interest. As an example the usage of this procedure is shown on miniaturization of a branch-line coupler with the central frequency of 2 GHz. Area occupied by the compact coupler is about 3 times less than of the conventional one.