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RF Communication Circuits
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Michiel Steyaert, Wouter De Cock, Patrick Reynaert
The radio frequency (RF) front-ends are the interface between the antenna and the digital modem of the wireless transceiver. They have to detect very weak signals (μV) that come in at a very high frequency (10 GHz), and at the same time transmit high-power levels (up to several watts) at the same high frequencies. This requires high-performance analog circuits, like filters, amplifiers, and mixers that translate the incoming modulated data between the antenna and the A/D conversion and digital signal processing. Consumer electronic markets are mainly driven by low-cost and low-power consumption. This makes the RF front-ends the bottleneck for future wireless applications. Low-cost and low-power are both linked to high integration level. A high level of integration renders a significant space, cost, weight, and power reduction. A higher degree of integration requires less discrete components reducing the bill of materials cost. Keeping signals on chip greatly reduces power consumption since less I/O drivers are needed. Many different techniques to obtain a higher degree of integration have been presented over the years [2–5]. This chapter introduces and analyzes some advantages and disadvantages and their fundamental limitations.
Smart Antenna System Architecture and Hardware Implementation
Published in Lal Chand Godara, Handbook of Antennas in Wireless Communications, 2018
Another important issue is the location of the RF bandpass filter near the LNA. In all RF front-end subsystems, noise and unwanted signals having their frequencies fallen within the image-frequency band must be removed by filtering. Although in some receivers, the RF filter is placed ahead of the LNA, such a configuration would not protect the receiver from the LNA noise in the image-frequency band. Therefore, a better solution would be to place the filter between the LNA and the mixer, because the high gain of the LNA would ensure that losses associated with the filter would have less impact on the receiver noise. In practice, however, the problem is more complicated if commercial IC components are used. The reason is that it may be more convenient for manufacturers to integrate the LNA and the mixer into one single IC. On the other hand, to reduce cost, they may not provide a means for the insertion of the external RF filter.
Design and Simulation of Adaptive Cognitive Radio Based on Software-Defined Radio (SDR) Using Higher-Order Moments and Cumulants
Published in Ibrahiem M. M. El Emary, Anna Brzozowska, Shaping the Future of ICT, 2017
Ahmed Abdulridha Thabit, Hadi T. Ziboon
The architecture for a generic cognitive radio transceiver is shown in Figure 17.4a. As shown from the figure it consists of the radio frequency (RF) front-end and the baseband processing unit. A control bus is used in controlling each component to make the radio adaptive to the RF environment. The RF front-end first amplifies the received signal, then mixes it to a lower band and, finally, the analog signal is converted to a digital signal. The baseband processing unit modulates or demodulates and encodes or decodes the signal depending on whether a signal was transmitted or received. The baseband signal processing unit is like to common transceivers; however the RF front-end is specifically designed to accommodate the need of the cognitive radio. CR transceiver is required to be able to sense over a wide spectrum range and preferably in real time. The RF hardware is needed to be able to tune in to any part of the frequency spectrum. The main components of the cognitive radio RF front-end, shown in Figure 17.4b, are as follows [17]: RF filter—Selects the desired operating band by bandpass filtering the received RF signal.Low noise amplifier (LNA)—Amplifies the received signal without adding a remarkable amount of noise.Mixer—Mixes the received signal with the locally generated RF and then converts it to the baseband or the intermediate frequency (IF).Voltage-controlled oscillator (VCO)—Generates a signal at a specific frequency depending on the control voltage. The generated signal is then used to convert the incoming signal frequency to the baseband or intermediate frequency.Phase locked loop (PLL)—Ensures the signal of the VCO is locked accurately on the specific reference frequency.Channel selection filter—Selects the desired channel and rejects adjacent channels.Automatic gain control (AGC)—Keeps the gain or output power level of an amplifier constant over a large range of input signal levels.Analog-to-digital converter (ADC)—Converts the analog input signal to a digital signal.
Design of a broadband frequency-tunable planar filtering power divider
Published in Electromagnetics, 2023
Honggang Hao, Huan Xu, Qinxuan Ling, Yunrui Wang, Bing Wang
In recent years, the research of RF microwave technology is developing rapidly toward integration and multi-function, researchers are paying more and more attention to having multi-functional integrated components or circuits. As two core passive microwave devices, filter and power divider are typically used in the RF front-end circuit. The integrated design of the two devices can not only diminish the power loss of the RF module circuit but also reduce the overall device size. At present, some designs (Qi, Jia, and Xiao 2020; Xu et al. 2019; Zhang et al. 2021, 2021, 2022; Zhuang et al. 2020) have achieved satisfactory performance of the FPD, such as low loss, high-frequency selectivity, wide-stopband suppression, and broadband isolation. However, in modern systems engineering, multi-frequency and functional integrated devices are more needed.
A Multiband E-Shaped Substrate Integrated Waveguide-Based Antenna for X, Ku, K-Band Applications
Published in IETE Journal of Research, 2021
In response to the rapidly growing satellite market and modern communication technologies, the demand for low-profile, high-gain multiband antennas (MBAs) has risen considerably. These antennas eliminate the need for multiple antennas for various applications in X, Ku, K-bands. Also, they enable the vast use of radar communication and satellite communication to sense multiple targets [1]. Since several bands are merged into a single antenna, these MBAs limit the size and weight of RF front-end modules in communication systems [2]. At the present period of time, transmission and reception of information using bidirectional links in emergency conditions are growing vastly facilitating communication between warships during any pandemic, news coverage during natural disasters, outside TV broadcasting from the remote locations, electronic news gathering (ENG) or satellite news gathering (SNG) for producing the live television broadcast such as live sports coverage and live news broadcast from the locations where a wired network is not installed [3]. For such a communication system, there is a rigorous requirement of a portable and light weight MBA that can serve multiple purposes.
A tri-band filter with controllable frequency and transmission zeros using dual-stubs loaded resonators
Published in Electromagnetics, 2021
Yuanmo Lin, Min-Hang Weng, Ping Zhang, Ru-Yuan Yang
In recent years, wireless communication system has developed rapidly. Related communication systems are applied to the technology products generally. According to the distinct applications, more communication protocols are presented to satisfy the different demands, such as Global System for Mobile Communications (GSM), Wireless Local Area Network (WLAN), and Worldwide Interoperability for Microwave Access (WiMAX) markets (Hong and Lancaster 2001). In the radio frequency (RF) front-end module of a wireless communication system, the filter is an important key passive component, which is located at the back of the antenna and the front of the low-noise amplifier. It is used to filter signals and pass unnecessary signals (Weng, Wu, and Su 2007). With the increased development of wireless communication technology, the research of bandpass filter (BPF) has become an important development direction.