An integrated wideband multifunctional antenna using a microstrip patch with two U-slots

In this paper a multifunctional microstrip antenna is designed, fabricated and experimentally verified for operation in AWS, GSM, WiMAX and WLAN bands. This microstrip patch antenna has two U-shaped slots to achieve the dual wideband operation required to meet these specifications. The dimensions and locations of the U-slots are designed appropriately. The thick substrate used here helps in integrating the antenna with the existing aircraft panel material while achieving wide bandwidths. Experimental results of this single feed antenna indicate that it meets all current requirements for in-cabin wireless communication needs.

PLL with secondary loop control for self tracking antennas

This paper shows a simple, yet highly effective, tracking phase locked loop circuit which has applications for self steered antenna arrays. The tracking PLL has been demonstrated to accurately phase track signal levels as low as -120 dBm, making it suitable for applications such as SATCOM ground terminals. The implementation is simple requiring a low Q voltage controlled oscillator, a downconverting mixer and a PLL circuit.

Pilot Tone Actuated Antenna Array Pattern Reconfiguration

A new strategy for remote reconfiguration of an antenna array far field radiation pattern is described. The scheme uses a pilot tone co-transmitted with a carrier signal from a location distant from that of a receive antenna array whose far field pattern is to be reconfigured. By mixing the co-transmitted signals locally at each antenna element in the array an IF signal is formed which defines an equivalent array spacing that can be made variable by tuning the frequency of the pilot tone with respect to the RF carrier. This makes the antenna array factor hence far field spatial characteristic reconfigurable on receive. For a 10 x 1 microstrip patch element array we show that the receive pattern can be made to vary from 35 to 10 degrees half power beam width as the difference frequency between the pilot and the carrier at 2.45 GHz varies between 10 MHz and 500 MHz carrier.

Design Method for Circularly Polarized Fabry-Perot Cavity Antennas

A new class of circularly polarized (CP) Fabry-Perot cavity antennas is introduced that maintain the simplicity of a linearly polarized primary feed and a single cavity structure. The proposed antennas employ a double-sided partially reflective surface (PRS), which allows independent control of the magnitude and phase responses for the reflection and transmission coefficients. In conjunction with an anisotropic high-impedance surface (HIS) ground plane, this arrangement allows for the first time a single cavity antenna to produce a specified gain in CP from a linearly polarized primary source. A design procedure for this class of antennas is introduced. The method exploits a simple ray optics model to calculate the magnitude and phase of the electric field in the cavity upon plane wave excitation. Based on this model, analytical expressions are derived, which enforce the resonance condition for both polarizations at a predetermined PRS reflectivity (and hence predetermined antenna gain) together with a 90 degrees differential phase between them. The validity of the concept is confirmed by means of an example entailing an antenna with gain of approximately 21 dB at 15 GHz. Full-wave simulation results and experimental testing on a fabricated prototype are presented and agree well with the theoretical predictions.

The Influence of the User in Body-Centric Antennas and Propagation at 3–6 GHz—A Rician K-Factor Approach

We investigate whether the presence of a human body in wearable communications should be considered as part of the radiating structure or as part of the local radio environment. The Rician $K$ -factor was employed as a quantitative measure of the effect of the user's body for five environments and two mounting locations. Presented empirical results indicated that the environment had a greater impact on the $K$-factor values than the position of the transmit antenna for the ultrawideband signals used, confirming that the human body should be considered primarily as part of the overall radiating system when the antenna is worn on the body. Furthermore, independent variations also existed in the $K$-factor values for the differing antenna-body mounting positions, indicating that as the position changed, then the radiating effects and the contribution from the body changed. This is significant for ensuring body-antenna systems are accurately modeled in system-level simulations.

Indoor off–body communications at 5.8 GHz with multiple antennas at the base station: a statistical characterization using the Nakagami–m fading model

In this paper we investigate the first and second order characteristics of the received signal at the output ofhypothetical selection, equal gain and maximal ratio combiners which utilize spatially separated antennas at the basestation. Considering a range of human body movements, we model the model the small-scale fading characteristics ofthe signal using diversity specific analytical equations which take into account the number of available signal branchesat the receiver. It is shown that these equations provide an excellent fit to the measured channel data. Furthermore, formany hypothetical diversity receiver configurations, the Nakagami-m parameter was found to be close to 1.

Characterisation of nonlinear distortion and intermodulation in passive devices and antennas

The paper presents a conceptual discussion of the characterisation and phenomenology of passive intermodulation (PIM) by the localised and distributed nonlinearities in passive devices and antennas. The PIM distinctive nature and its impact on signal distortions are examined in comparison with similar effects in power amplifiers. The main features of PIM generation are discussed and illustrated by the example of PIM due to electro-thermal nonlinearity. The issues of measurement, discrimination and modelling of PIM generated by nonlinearities in passive RF components and antennas are addressed.

Millimeter-wave Beam Scanning Antennas using Liquid Crystals

Two Liquid crystal-based reflectarrays that operate at 100 GHz and 125 GHz are presented. The first prototype (100 GHz) is used to validate the modeling and the design procedure proposed for this class of antenna. Experimental validation of the beam scanning is carried out by measuring the received power in a quasi-optical test bench, which is able to rotate the receiver in the horizontal plane. These results are used to design a second prototype antenna (125 GHz) which exhibits 2D beam scanning capabilities with a large bandwidth and scanning range that is sufficient for radar and communications applications.

Wearable antennas for medical monitoring systems

A wearable silver nano particle inkjet printed antenna suitable for wireless biomedical sensing is presented. The performance is evaluated on a synthetic variable layered phantom test-bed, representative of human tissue for operation in the 868/915 MHz, and 2400 MHz industrial, scientific and medical frequency bands. Antenna radiation efficiency measurements on the phantom were compared with antennas prototyped with copper. Total radiation efficiencies up to ???6.5 dB are reported, with less than 0.5 dB difference in performance between copper and silver nano particle variants, showing promising application for low-cost disposable wireless sensing.

Passive Intermodulation in Distributed Circuits with Cascaded Discrete Nonlinearities

The principle aspects of passive intermodulation (PIM) characterisation in distributed printed circuits with cascaded lumped nonlinearities are presented. Mechanisms of PIM generations have been investigated experimentally and modelled using the formalism of X-parameters. The devised equivalent circuit models are applied to the analysis of microstrip lines with distributed and cascaded lumped sources of nonlinearity. The dynamic measurements have revealed that PIM generation rates in straight and meandered microstrip lines differ and significantly deviate from those expected for the respective discrete sources of nonlinearity. The obtained results indicate that multiple physical sources of nonlinearity contribute to PIM generation in printed circuits. Finally, it is demonstrated that the electrical discontinuities can have significant effect on the overall PIM response of the distributed passive circuits and cause PIM product leakage and parasitic coupling between isolated circuit elements.