A dedicated low profile antenna for geodesic applications is presented. This type of antenna requires mitigation of multipath signals to achieve sub-centimeter level of precision. Typically, bulky and heavy choke ring structures have been used to reduce the effects of multipath interference. The antenna presented here consists of a low temperature co-fired ceramic (LTCC) patch antenna immersed in an electromagnetic bandgap (EBG) substrate. The EBG substrate reduces the effects of multipath by blocking the propagation of surface waves. The result is an antenna showing good multipath rejection and a stable phase center. The advantage of printed EBG substrates is that they can be realized in a low-weight, low-price, and low-profile fashion. First prototypes have been manufactured and tested, and its performance has been compared to that of a more classical choke ring antenna.

This paper presents a detailed and systematic investigation of the reproducibility of specific absorption rate (SAR) measurements using textile antennas and their simulation accuracy. The ability to accurately predict the SAR is very important for practical textile antenna designers since certified SAR measurements are costly. To that goal, the SAR values of a range of textile antennas operating in various bands of the IEEE 802.15.6 and 802.11 standards are evaluated. The selected textile antenna topologies for the evaluation differ in terms of the bandwidth behavior (broadband, dual band, and ultrawideband). They are chosen to be distinct, have been fabricated using an array of conductive textiles, and are benchmarked against similar structures made from a flexible conductor. SAR values are evaluated at three different frequencies, i.e., 2.45, 5.2, and 5.8 GHz, respectively, using a commercial electromagnetic solver and a certified experimental setup. Factors affecting the SAR behavior are presented and discussed. Results indicate that antennas without a rear ground plane are producing almost three times the SAR of textile antennas that feature a full ground plane. The results of this paper point out that the repeatability of the measurements is about 10% and that the agreement between simulations and measurements is on the order of about 17%.

An analog/digital hybrid delay-locked-loop (DLL) phase conjugator (PC) for use in retrodirective array (RDA) applications is proposed, implemented, and measured. Compared with previous phase-locked-loop PC solutions, the proposed DLL PC has a number of unique features that make it superior to previous solutions in many applications. These features include: 1) the ability to hold the phases of conjugated outputs even when input pilots disappear; 2) the ability to track the changing rate of phases of input pilots even when the pilot signals with dynamic phases disappear for a short period of time, i.e., the implemented RDAs can constantly track a moving target for retransmission even when the incoming pilots are not available due to deep channel fading or time division duplex operation; 3) the DLL PC can be flexibly configured as the voltage-controlled phase shifters for the use in traditional phased beam-steering arrays; 4) the DLL PC can indicate direction of arrival of the incoming signals without recourse to any baseband algorithms; and 5) the DLL PC is unconditionally stable. The operation of the DLL PC is articulated in this paper, and prototypes are built and their performance and functions are tested. In addition, a K-/Ka-band RDA demonstrator for satellite communications, based on the proposed DLL PC architecture, is implemented and measured, validating the "retro-direct" functionality over a wide view angle. To the best of our knowledge, this is the first time that a DLL has been used for PC, and it is the first time that a K-/Ka-band RDA based on this technology has been experimentally demonstrated.

This investigation aims at determining the Specific Absorption Rates (SARs) of textile antennas for on-body biomedical telemetry applications. The dual-band antennas are designed to operate at 2.4 GHz and 5.2 GHz with unidirectional radiations and broad bandwidths. Fractal Planar Inverted-F Antennas (F-PIFAs) are fabricated using different materials to assess factors influencing SAR levels. Simulations and measurements indicated a maximum SAR and uncertainty of 0.6 W/kg and 10%, respectively.

This paper describes the specific development of a high-data-rate 57-64-GHz point-to-multipoint wireless local-area network communication system and the worldwide first installation of such a system into an aircraft cabin mock-up. All of the system components, from the RF-chip-set, the low-temperature cofired ceramic integrated antennas, and RF modules to the baseband processor, the medium access control, and the application software were purpose-designed for a wireless backbone for in-cabin communication. The integration aspects of these system components into a passenger aircraft cabin mock-up (ceiling and passenger seat-integration) as well as successful system performance tests were carried out and are reported here.