Samer Abielmona

Microwave Analog Real-Time Spectrum Analyzer (RTSA) Based on the Spectral–Spatial Decomposition Property of Leaky-Wave Structures

A novel analog real-time spectrum analyzer (RTSA) for the analysis of complex nonstationary signals (such as radar, security and instrumentation, and electromagnetic interference/compatibility signals) is presented, demonstrated, and characterized. This RTSA exploits the space-frequency mapping (spectral-spatial decomposition) property of the composite right/left-handed (CRLH) leaky-wave antenna (LWA) to generate the real-time spectrograms of arbitrary testing signals. Compared to digital RTSAs, it exhibits the advantages of instantaneous acquisition, low computational cost, frequency scalability, and broadband or ultra-wideband operation. The system is demonstrated both theoretically by a commercial full-wave simulator and an efficient Greens function approach and experimentally by a parallel-waveguide prototype including a metal-insulator-metal CRLH LWA, 16 patch antenna probe detectors circularly arranged around the LWA, and a digital oscilloscope performing analog/digital conversion and time-domain acquisition before the postprocessing and displaying of the spectrogram. The system is tested for a large diversity of nonstationary signals and generates, in all cases, spectrograms that are in excellent agreement with theoretical predictions. The fundamental tradeoff between time and frequency resolutions inherent to all RTSA systems is also discussed, and an interchangeable multi-CRLH LWA solution is proposed to handle signals with different time durations.

Compressive Receiver Using a CRLH-Based Dispersive Delay Line for Analog Signal Processing

A compressive receiver (CR) is presented utilizing a composite right/left-handed (CRLH) dispersive delay line (DDL) for analog signal processing applications. The CRLH DDL offers advantages such as arbitrary frequency of operation and wide bandwidth, filling a gap with competing DDL technologies. The presented CR system utilizes an impulse-driven CRLH DDL and mixer inversion for chirp generation required for real-time signal processing. At high frequencies, this eliminates frequency ramp generators. The CR is employed as a frequency discriminator and a tunable delay line with dispersion compensation. The simulation and experimental results fully validate the presented systems as proof-of-concept for high-frequency applications such as real-time Fourier transformers and signal analyzers.

Experimental Demonstration and Characterization of a Tunable CRLH Delay Line System for Impulse/Continuous Wave

A new tunable delay system is presented and demonstrated experimentally in this letter. This system, which incorporates a composite right/left-handed (CRLH) transmission line, two mixers, and a low-pass filter, achieves a tunable group delay for impulse and continuous-wave signals, controlled by a local oscillator. This group delay tunability follows from the dispersion property of the CRLH transmission line and is achieved without suffering from the drawbacks of conventional delay lines in terms of matching, frequency of operation, and planar circuit implementation. The realized prototype exhibits measured group delays tunable between 5.1 and 8.54 ns over a frequency range of 2-4.5 GHz.

Pencil-Beam Full-Space Scanning 2D CRLH Leaky-Wave Antenna Array

A novel pencil-beam, full-space scanning 2D composite right/left-handed (CRLH) transmission line (TL) leaky-wave antenna (LWA) array is proposed. The proposed array achieves the same performance of conventional phase array antennas in a simpler manner. Moreover, array elements are fed by a CRLH infinite-wavelength series power divider and therefore the separation between array elements and the number of array element can be extended arbitrary. The CRLH series power divider eliminates the requirement of complex and high loss feeding networks commonly found in conventional arrays. Experimental results of each system components are presented along with analytical and simulation results of the complete array system.

Highly Efficient Leaky-Wave Antenna Array Using a Power-Recycling Series Feeding Network

A highly efficient leaky-wave antenna (LWA) array using a power-recycling series feeding network is proposed. The input power to the antenna array is efficiently recycled within the array elements and completely leaked out before reaching the terminations. Consequently, the array achieves high radiation efficiency and gain while maintaining a reasonable length in the direction of wave propagation. Simulated and measured results validate the proposed concept.

CRLH zeroth order resonator (ZOR): Experimental demonstration of insensitivity to losses and to size

The experimental demonstration of the insensitivity to losses and size of the composite right/left- handed (CRLH) zeroth order resonator (ZOR) is reported for the first time. The prototypes used for this demonstration are implemented in metal-insulator-metal (MIM) technology, which exhibits simplicity of design, high compactness and immunity to spurious resonances.

Performance-Enhanced and Symmetric Full-Space Scanning End-Switched CRLH LWA

An end-switched composite right/left-handed (CRLH) electronically scanned leaky-wave antenna (eLWA) is presented. The input signal is routed to either end of the CRLH eLWA via a switch, with each end providing half-space scanning (-90° ≤ θ ≤ 0°) . The end-switching scheme, which is applicable to any two-port LWA, enables full-space coverage using any half-space scanning only LWA. Compared to a conventional single-ended CRLH eLWA, which scans the full-space requiring a complex design, large capacitance values, and tuning range, the end-switched scheme simplifies the design and relaxes the constraints on the varactors, which lowers their cost. The conventional CRLH eLWA also suffers from a large scanning loss due to its large scanning range and from low efficiency due to its requirement for large capacitance values, which exhibit high loss. The end-switched CRLH eLWA reduces the scanning loss due to its smaller scanning range, while improving the efficiency due to its low capacitance values.

Tri-band and dual-polarized antenna based on composite right/left-handed transmission line

Relaxing the composite right/left-handed (CRLH) balance condition enables arbitrary tri-band CRLH resonant devices. This paper presents a tri-band and dual-polarized antenna based on this principle. The proposed CRLH antenna operates in the transversally-polarized zeroth order (ZO) shunt mode (n = 0) and in the two longitudinally-polarized half-wavelength (HW) modes (n = plusmn1). Explicit synthesis formulas are given for the CRLH tri-band operation. A specific microstrip design using MIM (metal-insulator-metal) series capacitors and shunt stub inductors is demonstrated. In this design, the three resonant modes n = -1, n = 0 and n = +1 exhibited similar input impedances (allowing a simple feeding structure), radiation patterns and efficiencies/gains.

Carrier frequency tunable impulse/continuous wave CRLH delay line system

The concept of tunable group velocity in a CRLH transmission line has been presented and a new pulsed and CW CRLH-based tunable delay line system has been subsequently proposed. In these systems, the pulse delay can be controlled by externally tuning the carrier frequency of the input signal. This effect has been verified by circuit simulations. Such systems are expected to be easy to implement and are anticipated to lead to interesting UWB solution, such as pulse position modulators and wide variety of other pulsed and harmonic delay.

Novel power recycling schemes for enhanced radiation efficiency in leaky-wave antennas

Two novel power recycling schemes for enhancing the radiation efficiency of leaky-wave antennas are proposed and demonstrated both theoretically and experimentally. The first scheme enhances the radiation efficiency of a single leaky-wave antenna by feeding the energy remaining at the output of the antenna back into its input terminal via a rat-race hybrid coupler. In this manner, the power associated with each information symbol loops several times along the structure until all its energy has been fully radiated, leading ideally to a 100% radiation efficiency. This is the self-recycling scheme. The second scheme enhances the radiation efficiency of a leaky-wave antenna array by re-injecting the energy remaining at the output of the excited element into the adjacent elements of the array via a series feeding network, and possibly including phase-shifters for full-space pencil-beam scanning. This is the cross-recycling scheme.