Two-element Phased Array Research Articles

General Framework for Array Noise Analysis and Noise Performance of a Two-Element Interferometer With a Mutual-Coupling Canceler

This article investigates the noise performance of a two-element phased array and interferometer containing a recently introduced self-interference canceler, which in the context of this work acts as a mutual-coupling canceler. To this end, a general framework is proposed to permit noise analysis of this network and a large variety of other networks. The framework-based numerical analysis for a two-element-phased array shows that the addition of the canceler significantly increases the beam-equivalent noise temperature. For a two-element interferometer used in cosmology, this increase in noise temperature is still acceptable as the sky noise temperature in the 20-to-200 MHz band is high. When used in an interferometer, the canceler provides the ability to null mutual coherence at the interferometer output. The ability to provide matching to reduce the sensitivity of the null in mutual coherence to the phase of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol {90^{\circ }}$ </tex-math></inline-formula> hybrids in the canceler is discussed.

Chaos Time Delay Signature Suppression Assisted by a Phased Array With Four Different Waveguide Structures

We propose and demonstrate a chaos generation scheme that conceals the time-delay signature (TDS) by injecting the output of an external-cavity semiconductor laser (ECSL) into a two-element phased array (ECSL-TPA). We consider the case of the ECSL output with obvious TDS, and evaluate the performance of the ECSL-TPA with four waveguide structures in TDS suppression. The numerical results demonstrate that the ECSL-TPA allows for desired TDS suppression in wide parameter space regardless of the waveguide structures considered. However, different TDS behavior exists for these structures, which provides guidance for future design and optimization of the proposed ECSL-TPA. Additionally, the influence of some key parameters including the injection rate, frequency detuning, laser separation ratio, pump rate, linewidth enhancement factor, and frequency offset on TDS is systematically studied. Appropriate settings of these key parameters are beneficial for TDS suppression and thus optimizing optical chaos. The phased array can be extended to include a large number of elements and thus generates multiple independent chaotic signals with indistinguishable TDS in parallel, paying the way for chaos-based applications that require independent, high-quality chaos simultaneously.

An mm-Wave Scalable PLL-Coupled Array for Phased-Array Applications in 65-nm CMOS

A new two-element phase-locked loop (PLL)-coupled array for the implementation of millimeter-wave (mm-wave) and subterahertz (sub-THz) phased arrays is presented. This architecture avoids using lossy phase shifter to create the required phase shift between the adjacent elements in a phased-array system. The required phase shift is generated by utilizing a dual nested loop PLL. The two PLL loops work together to stabilize the frequency and create the required phase shift. Moreover, it can be scaled simply by adding more unit cells to the architecture. A 112-121-GHz two-element phased array is designed and fabricated in a standard 65-nm CMOS process. It consumes 147-mW power and provides a phase shift of 46.7° ranging from 58.53° to 105.2° at 117 GHz.

Mutual Inductance in Magnetic Resonance Two-Element Phased-Array Square Coils with Strip and Wire Conductors

Phased-array coils are extensively employed in Magnetic Resonance (MR) as transmitter and receiver radiofrequency (RF) coils due to their large field-of-view (FOV) and their high signal-to-noise ratio (SNR). Array elements have to be geometrically decoupled for mutual coupling minimization, to achieve coil performance maximization. This paper proposes an analytical method for the mutual inductance calculation between two square loops constituting a 2-element phased-array coil in dependence on the conductor cross-sectional geometry (flat strip and circular wire). Simulation accuracy was evaluated with workbench experimental measurements performed at 21 MHz frequency on two home-built array square coils.

ARRAY-FED BEAM-SCANNING PARTIALLY REFLECTIVE SURFACE (PRS) ANTENNA

A beam-scanning partially reflective surface (PRS) antenna is presented in this paper. By employing a reconfigurable feed network to a two-element phased array source, the PRS antenna can realize beam steering between −10◦ and 10◦ with respect to the broadside direction across an overlapped frequency range from 5.35GHz to 5.76GHz. Good agreement between the simulated and measured results is achieved, which validates its capability to be a good candidate for the modern communication systems.

Using Antenna Arrays to Motivate the Study of Sinusoids

Educational activities involving antenna arrays to motivate the study of sinusoids are described. Specifically, using fundamental concepts related to phase and simple geometric arguments, students are asked to predict the location of interference nulls in the radiation pattern of two-element phased array antennas. The location of the radiation nulls are then verified experimentally. The activities have been employed both in a freshman-level electrical engineering course and, in expanded form, a summer research experience for high school students. Details of the experiments are given, as are results of student assessment and suggestions for further development.

Radiation Characteristics of Two-Element Phased Array Using Rectangular Waveguide Sections with a Surface Wave Excitation

Radiation Characteristics of Two-Element Phased Array Using Rectangular Waveguide Sections with a Surface Wave Excitation

Coupling and decoupling theory and its application to the MRI phased array.

In classical MRI phased-array design, optimal coil overlapping is used to minimize coupling between nearest-neighbor coils, and low input impedance preamplifiers are used to isolate the relatively weak coupling between non-nearest neighbors. However, to make the complex sensitivities of phased-array coils sufficiently distinct in parallel spatially-encoded MRI, it is desirable to have no overlapping between coils. Also, if phased arrays are used as transmit coils in MRI, one can no longer rely on the low input impedance of the preamplifiers for decoupling. Here a coupling and decoupling theory is introduced to provide a better understanding of the relations between coupled and uncoupled signals in the MRI phased array, and to offer a new method for decoupling phased-array coils without overlapping the nearest coil pairs. The new decoupling method is based on the assumption that any n-element phased array can be decoupled by a 2n-port interface system between phased array and preamplifiers. The detailed analysis and the experimental results show that a four-port interface can be used to decouple a two-element phased array. Furthermore, the four-port interfaces can serve as building blocks to construct a 2n-port decoupling interface. This new method allows one to place the coil elements anywhere that could optimize parallel spatial encoding without concern for coupling between the coils. The method can also be used for phased-array transmit coils.

Master oscillator with power amplifiers: performance of a two-element cw HF phased laser array

The experimental performance of a two-element phased array of multiline cw HF chemical lasers in the master oscillator with power amplifier (MOPA) configuration has been measured. The mutual coherence of the two amplified beams was inferred from measurements of the visibility of interference fringes obtained when the beams were overlapped in the near field. When the optical path difference for the two beams was minimized, multiline visibilities of 0.90 +/- 0.02 were measured. White light interferometry was used to equalize the optical path lengths. Spectral mismatch between the master oscillator output and the amplifier's preferred gain distribution affected neither the amplification factor nor the mutual coherence of the amplified beams. The effect of spatial coherence of the master oscillator beam on these near field measurements and the eventual requirement of far field measurements to precisely optimize path lengths are discussed. Spectra data, amplification factors, and mutual coherence measurements are shown, and the resulting phased array far field performance is presented.