Wei-Chiang Lee

Design and measurement of a planar 9-way metamaterial power divider

A planar 9-way metamaterial power divider composed of positive refractive index (PRI) material with right-handed unit cells and zero refractive index (ZRI) material with left-handed unit cells is presented. A semi-circular interface is between PRI and ZRI materials. The infinite wavelength phenomenon in the ZRI material with an equal magnitude and phase distribution is experimentally verified via field and circuit measurements. They are shown in good agreement with simulation results.

Design and Power Performance Measurement of a Planar Metamaterial Power-Combined Amplifier

In this paper, a planar nine-way metamaterial power-combined amplifier implemented with microstrip grids, lumped capacitors and inductors, and power amplifiers is presented. The power-dividing/combining structure is a metamaterial lens composed of positive refractive index (PRI) material with right-handed unit cells and zero refractive index (ZRI) material with left-handed unit cells. A semi-circular interface is between PRI and ZRI materials. The infinite wavelength phenomenon in the ZRI material attains an equal magnitude and phase distribution to have an interconnection with the collinearly aligned amplifiers as a nine-way metamaterial power-combined amplifier with its input and output ports at the two focal points of a planar PRI–ZRI–PRI lens. An output power of 7.64 W with a combining efficiency of 85% is measured at 1.008 GHz. Through the field measurement to each unit cell, the dividing/combining phenomenon is experimentally verified and shown in a good agreement with simulation results. Furthermore, the graceful degradation characteristic of this power-combined amplifier is experimentally demonstrated.

A balanced-to-balanced power divider with common-mode noise absorption

This paper presents a balanced-to-balanced power divider (PD) with common-mode (CM) noise absorption for the first time. By properly adding the λ/4 transformers and resistors at the input-/output ports of back-to-back PD, the proposed balanced-to-balanced PD can achieve CM noise absorption while keeping its differential-mode (DM) characteristics. The measured results at 2.55 GHz show that reflection and transmission coefficients for CM operation are all less than -30 dB, while less than -30 dB and better than -4 dB for DM operation.

A Rigorous Proof on the Radiation Resistance in Generalized PEEC Model

This paper develops a theory on the proof of the radiation resistance in frequency-domain partial element equivalent circuit (PEEC) model. Specifically, the total power dissipated on the imaginary part of the complex inductance and capacitance derived from the PEEC model is found to be the total radiated or scattered power when the structure is internally excited by independent sources, or externally by incident waves, respectively. Accordingly, the imaginary part of the complex inductance and capacitance represents a radiation resistance network of the structure. Numerical simulations based on PEEC and commercial electromagnetic simulation tool are presented for comparison, and some physical implications are discussed.

Implementation and measurement of a microstrip square planar 36-way metamaterial power divider

Power divider has found many applications in antenna array, amplifiers, and microwave systems. In recent years, metamaterials that display left-handed (LH) propagation behavior have been extensively investigated and applied to microwave devices. These devices are mostly based on one-dimensional (1D) left-handed and right-handed (RH) transmission lines. One phenomenon that can be obtained from metamaterials is propagation with infinite wavelength, where the waves travel along a finite length structure with zero phase shift [1]. Infinite wavelength in 1D structure has been demonstrated in [1–3], and exploited in compact zero phase shifters [2] and power dividers [1], [3]. Recently, the 2D metamaterial structure with infinite wavelength is studied by properly arranging LH and RH unit cells in a checker-board tessellation to design a 20-way squared-shaped power divider [4, 5]. In this paper, a 36-way square-shaped 2D power divider using a novel structure with distinct RH and LH regions is implemented. Its RH and LH unit cells with zero phase shift are analyzed and designed. The experimental results of a 36-way square-shaped power divider are given.

Modeling of a Planar Metamaterial Power Divider/Combiner Using Transmission Matrix Method

This letter presents a circuit modeling approach to analyze the scattering parameter and spatial voltage distribution of a planar nine-way metamaterial power-divider/combiner structure. The analysis is based on the multi-input and multi-output transmission matrix method. Computation results of this nine-way metamaterial power divider/combiner are shown in good agreement with simulation results using commercial microwave circuit simulator and measurement results.

Experiments of device failures in a planar nine-way metamaterial power-combined amplifier

The degradation characteristic of a planar nine-way metamaterial power-combined amplifier with device failures is investigated in this paper. The power-divider/combiner design is based on the metamaterial lens structure and is composed of positive refractive index material and zero refractive index (ZRI) material. Nine 1-W power amplifiers are inserted in the ZRI material to attain a nine-way power-combined amplifier. Due to its uniform isolation characteristics of the metamaterial power divider/combiner, the graceful degradation performance of this power-combined amplifier is shown to be independent of the amplifier failure sequence and is experimentally demonstrated.

Measurements of a Planar Nine-Way Metamaterial Power-Combined Amplifier

In this paper, measurement results of a planar nine-way metamaterial power-combined amplifier are presented. The power-divider/combiner structure is a metamaterial lens composed of positive refractive index (PRI) material with right-handed unit cells and zero refractive index (ZRI) material with left-handed unit cells. Due to its uniform isolation characteristics, the graceful degradation performance of this power-combined amplifier is shown to be independent of the amplifier failure sequence. The power combining of nine 1-W amplifiers gives an output power of 7.64 W with a combining efficiency of 85% at 1.008 GHz, and the graceful degradation characteristic of this power-combined amplifier is experimentally demonstrated.

Measurement of a planar 9-way metamaterial power combined amplifier

In this paper, a planar 9-way metamaterial power combined amplifier is presented. The power divider/combiner structure is a metamaterial lens composed of positive refractive index (PRI) material with right-handed unit cells and zero refractive index (ZRI) material with left-handed unit cells. A semi-circular interface is between PRI and ZRI materials. Due to its uniform isolation characteristics of the power divider/combiner, the graceful degradation performance of this power combined amplifier is shown to be independent of the amplifier failure sequence. The power combining of nine 1 W amplifiers gives an output power of 7.64 W with a combining efficiency of 85% at 1.008 GHz, and the graceful degradation characteristic of this power combined amplifier is experimentally demonstrated.

Analysis and design of an active lens implemented by planar distributed metamaterials

In this paper, a distributed active lens with PRI/NRI materials is designed and measured. The unit cell of NRI material is analyzed using HFSS under periodic boundary condition to give the dispersion diagram of unit cell. The corresponding refraction index and LH mode frequency computed by circuit model and HFSS are also shown in a good agreement. A scanning arrangement is developed using an Agilent E8364B PNA and an Agilent 85024A active probe to record the S21 values for both the active and passive lenses. The focus and refocus phenomena are observed in the NRI material and the right side PRI material to demonstrate the negative refraction phenomenon. Moreover, the active lens with amplifiers embedded in the transmission path of the NRI material can compensate the imperfect match including dielectric loss, metal loss and impedance mismatch to clearly show the refocusing phenomenon in the right side PRI material.