# Broadband Microstrip Antenna for 5G Wireless Systems Operating at 28 GHz
## 2 Characteristics of the 5G System  
The 5G network makes use of new technological solutions to meet the growing requirements of users. As a result, the new system will be able to handle an increasing number of devices, and to satisfy higher quality thresholds required by modern applications. It is an evolution of the 4G networks of today, which incorporates technologies capable of handling the rapidly increasing amount of transmitted data and facilitating data exchange between an ever-growing number of IoT devices. As is typical for the introduction of any next-generation network, it is expected that until its coverage and functionality can match or surpass existing 4G networks, the 5G network will need to coexist with such [1]. In addition to the existing usage scenarios of mobile networks, three additional scenarios are planned for the emerging 5G network, all of which will be of particular importance to users and will distinguish the 5G network from previous generations. The first new usage scenario is an enhanced mobile broadband (eMBB), which enables high-speed internet access (up to 1 Gbps) and will be the defining feature of this network as compared with existing networks, especially in the initial phase of its implementation. This advantage of the 5G system over legacy solutions will increase the efficiency and quality of communications in society. As an example, this will enable services based on the provision of high-resolution multimedia, attractive methods of communication (e.g., video, augmented and virtual reality), as well as smart city services (e.g., transmission of content from high-resolution cameras) [2; 3]. The second use of 5G networks is based on massive machine type communications (mMTC), where 5G will be able to support a very large number of connections from low-power devices, referred to as the Internet of Things (IoT), to the mobile network. These devices asynchronously exchange data, using the mobile network to communicate. This scenario assumes support for a large number of device types, with the reservation that these devices will use the mobile network in an occasional manner, exchanging small volumes of data [5]. The third use is referred to as ultra-reliable low latency communications (URLLC), which be a technology providing a minimum (1 ms) latency for data exchange over a mobile network for critical applications (e.g., drone control). In previous generations of mobile networks, latency values were longer and amounted to about 100 milliseconds for 3G networks, with about 30 milliseconds in case of 4G (LTE--Long Term Evolution) network [6]. According to the current state of standardization of the 5G network, it is intended to operate in three frequency bands, i.e., low, medium, and high. The use case of a particular band depends on its characteristics, which include two factors in particular, i.e., radio signal propagation and capacity of spectrum resources. The first factor is related to the physical properties of electromagnetic waves and determines the obtainable radio transmission range in changing weather conditions and radio signal coverage in hard-to-reach areas (e.g., interiors of buildings). The second factor is associated with the available amount of RF bands in a given frequency range, which can be used by 5G networks. It should be noted that high bandwidths also require a wide radio band, which, being a limited resource, is subject to rationing, and its use must also take into account RF communication applications other than 5G networks, such as TV broadcasts, radio communication for home automation equipment, etc. In a 5G system, the following three frequency bands are assumed to be used first [1; 2]:  
* From 694 to 790 MHz (700 MHz band);
* From 3400 to 3800 MHz (3.6 GHz band);
* From 27.50 to 28.35 GHz (28 GHz band). The 700 MHz band is characterized by good signal propagation and relatively low attenuation (absorption of signal by various obstacles), which helps cover large areas. Thanks to these characteristics, this band can be used for mMTC services.