1. Introduction
The population of our planet is gradually increasing and has already exceeded 7 billion people. The information needs of the population are growing; at the same time, new technologies such as the Internet of Things (IoT), intelligent transport systems (such as Vehicular Ad hoc Network (VANETs)) and virtual and augmented reality are actively developing [
1]. The growth of data traffic and device connections will require data rates to increase by more than an order of magnitude [
2]. Responding to these requests, the International Telecommunication Union (ITU) decided to develop a new generation of 5G wireless communications with high transmission speeds (>10 Gbit/s) and ultralow response times (<1 ms). However, an increase in the transmission date rate is mainly possible due to the expansion of the band that the frequencies use. The requirements for 5G networks can only be implemented in the millimeter-wave frequency range [
3].
The advantages of millimeter waves (mm-waves) when used for radio communications have been well known for many years [
4]. The advantageous features of millimeter-wave radio waves are responsible for their widespread use in radar systems, remote sensing, navigation and communications. Interest in millimeter waves has increased due to the need to expand the radio frequency spectrum for commercial applications. Compared with previous generations, mm-wave 5G wireless communication systems have higher data rates and data transfer density, millisecond latency and enhanced spectral energy. The International Telecommunication Union (ITU) has specified a number of the mm-wave frequency bands for 5G [
5] wireless networks, but the 27.5–28.35 GHz band was proposed for wide usage in many countries and was licensed by the Federal Communications Commission (FCC) [
6].
Power consumption is one of the most significant technical barriers for practical mm-wave 5G wireless communications because multiple devices connected at the same time increase the power consumption of the base stations and data centers. Photonic technologies can be utilized in order to solve this problem. In data centers, chip-to-chip optical or electro-optical interconnects enable an increase in the bandwidth and capacity of those systems as well as a reduction in power consumption [
7,
8].
In a conventional 4G communication system, one or more passive antennas are used. Wireless 5G networks are based on active massive-element antenna systems that improve the capacity, efficiency and coverage of RF streams [
9] (
Figure 1).
To improve the bandwidth and data rate, the multiple-input multiple-output (MIMO) transceivers based on phased beamforming arrays are used [
10,
11,
12,
13]. Usually, active antenna systems consist of massive antenna arrays with integrated MIMO transceiver RF front-ends.
Figure 2 shows the design of a multichannel transmit RF front-end (RFFE) module for 5G MIMO transceivers. There is a symmetrical antenna array where each channel consists of a phase shifter, a driver amplifier and a power amplifier. The input splitter divides the RF signal into a number of channels. The symmetry of the RFFE module architecture allows for a balance between input and output losses and power consumption.
The performance and power consumption of millimeter-wave 5G communication systems are mainly dependent on the electrical parameters of using RF electronic components based on semiconductor monolithic integrated circuits, which are the key elements for mm-wave RF transmit/receive modules. The development of such elements is a difficult challenge.
A previous study presented the results of the development of a 28 GHz phase adjustable power amplifier monolithic microwave integrated circuit (MMIC) for 5G front-ends [
14]. It consisted of a 4-bit digitally controlled phase shifter and power amplifier. The MMIC was designed by Plextek RFI and fabricated by Win Semiconductors using a 0.15 µm GaAs pHEMT process. The main disadvantage of this MMIC is a low phase shift resolution of 22.5°, which results in reduced beamforming opportunities and low antenna gain.
In this study, the design approach for a 28 GHz single-chip transmit RFFE MMIC with high phase shift resolution (5.625°) for multichannel 5G wireless communications is presented, along with its electrical performance. The integrated circuit (IC) consists of a 6-bit digital phase shifter, a driver amplifier and a power amplifier and was designed using a 0.25 µm GaAs pHEMT process of JSC Micran (Tomsk, Russian Federation) for low-cost volume production.
3. Conclusions
Millimeter-wave wireless networks have attracted the most interest as 5G communication systems of the new generation (5G). The 27.5 to 28.35 GHz band was licensed for 5G wireless networks by the FCC. The performance and power consumption of millimeter-wave 5G communication systems mainly depend on the electrical parameters of the electronic RF components used inside RF transmit/receive modules.
The design approach for a 28 GHz single-chip transmit RF front-end MMIC is presented in this paper, along with its electrical performance. The IC includes a 6-bit digital phase shifter, a driver amplifier and a power amplifier. It was designed using a 0.25 µm GaAs pHEMT process for low-cost volume production. The output power P3dB and PAE are 29 dBm and 19.2% at 28 GHz. The phase shifter RMS phase and gain errors are 3° and 0.6 dB at 28 GHz. The fabricated single-chip RF front-end MMIC can be used in multichannel transmit 5G front-end modules based on phased antenna arrays.