Cellular Radio Frequency Research Articles

Power-Efficient CMOS Cellular RF Receivers for Carrier Aggregation According to RF Front-End Configuration

This article presents power-efficient radio frequency (RF) receiver designs, particularly for advanced long-term evolution cellular applications. The two proposed single-ended receiver architectures can fully support multiple-channel RF signals in advanced carrier aggregation (CA) scenarios with maximum design flexibility depending on the RF front-end module configuration and target applications. Two different low-noise amplifier (LNA) topologies are employed in receivers to achieve different bandwidth handling capabilities and linearity requirements. The first receiver architecture utilizes narrowband LNAs with a current-reusing technique using a 28-nm low-power complementary metal-oxide-semiconductor (CMOS) technology. The proposed receiver with this single-ended narrowband LNA can handle up to three carrier components (CCs) CA. The second receiver architecture shows wideband characteristics and employs current-efficient and high linear wideband LNAs. This proposed design can support up to five CC CA and is implemented in a 14-nm Fin field-effect-transistor CMOS technology. Moreover, frequency-band switchable transformers are utilized in both designs to realize size-efficient receivers. Both proposed receivers operate at a frequency ranging from 0.6 to 2.7 GHz. The implemented narrowband and wideband receivers have conversion gains exceeding 70 and 62 dB, and achieve noise figures of less than 3.5 and 5 dB during all CA scenarios, respectively. The proposed receivers operate at a nominal supply of 1.2 and 1.0 V for 28 and 14-nm CMOS technologies, respectively.

Backscatter Communications: Inception of the Battery-Free Era—A Comprehensive Survey

The ever increasing proliferation of wireless objects and consistent connectivity demands are creating significant challenges for battery-constrained wireless devices. The vision of massive IoT, involving billions of smart objects to be connected to the cellular network, needs to address the problem of uninterrupted power consumption while taking advantage of emerging high-frequency 5G communications. The problem of limited battery power motivates us to utilize radio frequency (RF) signals as the energy source for battery-free communications in next-generation wireless networks. Backscatter communication (BackCom) makes it possible to harvest energy from incident RF signals and reflect back parts of the same signals while modulating the data. Ambient BackCom (Amb-BackCom) is a type of BackCom that can harvest energy from nearby WiFi, TV, and cellular RF signals to modulate information. The objective of this article is to review BackCom as a solution to the limited battery life problem and enable future battery-free communications for combating the energy issues for devices in emerging wireless networks. We first highlight the energy constraint in existing wireless communications. We then investigate BackCom as a practical solution to the limited battery life problem. Subsequently, in order to take the advantages of omnipresent radio waves, we elaborate BackCom tag architecture and various types of BackCom. To understand encoding and data extraction, we demonstrate signal processing aspects that cover channel coding, interference, decoding, and signal detection schemes. Moreover, we also describe BackCom communication modes, modulation schemes, and multiple access techniques to accommodate maximum users with high throughput. Similarly, to mitigate the increased network energy, adequate data and power transfer schemes for BackCom are elaborated, in addition to reliability, security, and range extension. Finally, we highlight BackCom applications with existing research challenges and future directions for next-generation 5G wireless networks.

Can we estimate the cellular phone RF peak output power with a simple experiment?

Cellular phones are becoming increasingly useful tools for students. Since cell phones operate in the microwave bandwidth, they can be used to motivate students to demonstrate and better understand the properties of electromagnetic waves. However, since these waves operate at higher frequencies (L-band, from 800 MHz to 2 GHz) it is not simple to detect them. Usually, expensive real-time high frequency oscilloscopes are required. Indirect measurements are also possible through heat-based and diode-detector-based radio-frequency (RF) power sensors. Another didactic and intuitive way is to explore a simple and inexpensive detection system, based on the interference effect caused in the electronic circuit of TV and PC soundspeakers, and to try to investigate different properties of the cell phones’ RF electromagnetic waves, such as its power and modulated frequency. This manuscript proposes a trial to quantify these measurements, based on a simple Friis equation model and the time constant of the circuit used in the detection system, in order to show it didactically to the students and even allow them also to explore such a simple detection system at home.

LTE-A Implementation Scenarios

This paper covers most aspects of LTE Radio Frequency (RF) system planning; this study has been extended to cover different implementation scenario for LTE-Advance. It explains the parameters that comprise the 4G cellular RF Link Budget and the basic propagation models in order to perform a RF Planning for LTE. Cell coverage has been estimated for different spectrum band and bandwidth and different modulation and coding schemes (MCS).

Cellular RF in Munich Is Hot and “Cool” [MTT World

The southern German state of Bavaria (Bayern, in German) has traditionally been a major technology hub in Germany and Europe. Semiconductor companies recognized worldwide have large offices there. In addition to consumer application components, radio-frequency (RF) systems in general and mobile communications in particular have a golden spot there. ST Microelectronics, Texas Instruments, and TriQuint are among the semiconductor companies that have an international branch in Bavaria. The area has even attracted some mobile communication companies like Huawei (who has recently opened a big research center), Nokia-Siemens Networks, and Sony-Ericsson.

A Five-Band Reconfigurable PIFA for Mobile Phones

We describe the design of a small microelectromechanical systems (MEMS) switched planar inverted F antenna capable of operation in five cellular radio frequency bands. Both simulated and measured results are shown using MEMS devices fabricated in an industrialized process based on high-ohmic silicon. Results show that the antenna bandwidth (or size) and specific absorption rate can be significantly improved using such devices.

Effects of cellular phone use on ear canal temperature measured by NTC thermistors

The earlier studies using phantom models and human subjects concerning warming effects during cellular phone use have been controversial, partly because radiofrequency (RF) exposures have been variable. In this randomized, double-blind, placebo-controlled crossover trial, 30 healthy subjects were submitted to 900 MHz (2W) and 1800 MHz (1W) cellular phone RF exposure, and to sham exposure in separate study sessions. Temperature signals were recorded continuously in both ear canals before, during and after the 35-min RF exposure and the 35-min sham exposure sessions. Temperature was measured by using small-sized NTC thermistors placed in the ear canals through disposable ear plugs. The mean temperature changes were determined during a set cardiovascular autonomic function studies: during a 5-min controlled breathing test, during a 5-min spontaneous breathing test, during 7-min head-up tilting, 1-min before, during and after two consecutive Valsalva manoeuvres and during a deep breathing test. Temperatures in the exposed ear were significantly higher during RF exposures compared with sham exposure in both 900 and 1800 MHz studies with maximum differences of 1 x 2 +/- 0 x 5 degrees C (900 MHz exposure) and 1 x 3 +/- 0 x 7 degrees C (1800 MHz exposure). Temperatures in the RF-exposed ear were also significantly higher during the postexposure period compared with post-sham exposure period with maximum differences of 0 x 6 +/- 0 x 3 degrees C for 900 MHz and 0 x 5 +/- 0 x 5 degrees C for 1800 MHz. The results of this study suggest that RF exposure to a cellular phone, either using 900 or 1800 MHz with their maximal allowed antenna powers, increases the temperature in the ear canal. The reason for the ear canal temperature rising is a consequence of mobile phone battery warming during maximal antenna power use. The earlier published articles do not indicate that temperature rising in the ear canal has any significant contribution from the RF fields emitted from mobile phones.