Ole Jagielski

Compact Agile Antenna Concept Utilizing Reconfigurable Front End for Wireless Communications

The conventional full-duplex radio communication systems require that the radio transmitter (Tx) is active at the same time as the radio receiver (Rx). The Tx and the Rx are using separate dedicated frequency bands and the Tx-Rx isolation is ensured by duplex filters. However, increasing number of frequency bands crave for multiband and multimode operation, which either require agile duplexers or a bank of narrow-band filters with a switch. While practical agile duplexers are not available, a bank of narrow-band filters with a switch is bulky and incurs switching loss. This paper proposes an approach that separates the Tx and Rx chain throughout the front end (FE). The complexity of the FE is reduced dramatically by replacing the duplex filters with tunable filters and closely integrating the tunable antennas in the FE, providing filtering which can be used to lower requirements for the tunable filters. For this purpose, very small narrow-band antennas are designed, which can cover 1710-2170 MHz by using tunable capacitors. Simulations and measurements of the antenna concept are carried out in the proposed FE architecture, serving as a proof of concept.

Aspects of High-Q Tunable Antennas and Their Deployment for 4G Mobile Communications [Antenna Applications Corner]

Tunable antennas are very promising for future generations of mobile communications, where broad frequency coverage will be increasingly required. This article describes the design of small high quality factor (high-Q) tunable antennas based on microelectromechanical systems (MEMS) that are capable of operation in the frequency ranges of 600-960 MHz and 1,710-2,690 MHz. Some aspects of high-Q tunable antennas are investigated here through experimental measurements, and the results are presented.

SAR Study of Mobile Phones as a function of Antenna Q

High-Q tunable antennas are good alternatives to low-Q passive antennas because the antenna size can be smaller while covering the required long-term evolution (LTE) frequency bands. However, among other things, specific absorption rate (SAR) can become a challenge due to the relative high current density associated with high-Q antennas. The higher energy stored in the electric and magnetic near-field components can result in higher SAR. Hence, SAR study of high-Q antennas is necessary which, if not addressed, might not comply with the SAR safety guidelines. In this paper, SAR as a function of antenna Q is investigated numerically as well as experimentally at two distinct frequencies (720 and 1700 MHz). It is found that SAR increases as a function of antenna Q when no losses are considered. But when losses are included, there is no more a clear trend between SAR and antenna Q. Thus, the final SAR values depend on total losses of the mock-up (MU).

Tunable Design for LTE Mobile-Phones

Antenna volume has become a critical parameter in mobile phone antenna design, as broader bandwidths are required for high connectivity between users. Shrinking the antenna size affects its efficiency, if one does not sacrifice bandwidth. This paper proposes an architecture to address the need for small and wide-band antennas. The study focuses on the low-frequencies (700 MHz - 960 MHz) in order to address a tough scenario for small platforms. A tunable design of the front-end and the antennas of the mobile phone is proposed and investigated. Operation is achieved on all low-bands with an efficiency of -3 dB at 700 MHz.