Alexander B. Kozyrev

Linear tunable phase shifter using a left-handed transmission line

We demonstrate a compact, linear, and low loss variation hybrid phase shifter using a left-handed (LH) transmission line. For frequencies from 4.3 to 5.6 GHz, this phase shifter gives a nearly linear phase variation with voltage, with a maximum deviation of /spl plusmn/7.5/spl deg/. Within this frequency range, the maximum insertion loss is 3.6 dB, and the minimum insertion loss is 1.8 dB over a continuously adjustable phase range of more than 125/spl deg/, while minimum return loss is only 10.2 dB. Furthermore, this phase shifter requires only one control line, and it consumes almost no power.

Tunable transmission and harmonic generation in nonlinear metamaterials

We study the properties of a tunable nonlinear metamaterial operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators and wires where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We show that at higher powers the transmission of the metamaterial becomes power dependent, and we demonstrate experimentally power-dependent transmission properties and selective generation of higher harmonics.

Nonlinear magnetic metamaterials

We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission.

Wave propagation in nonlinear left-handed transmission line media

Using a one-dimensional system, we demonstrate a wide variety of wave propagation phenomena possible in nonlinear left-handed media. These include effective second-harmonic generation where the fundamental wave and the second-harmonic wave are badly mismatched. We also observe parametric instabilities accompanying intensive harmonic generation.

Nonlinear left-handed transmission line metamaterials

Metamaterials, exhibiting simultaneously negative permittivity e and permeability μ, more commonly referred to as left-handed metamaterials (LHMs) and also known as negative-index materials, have received substantial attention in the scientific and engineering communities [1]. Most studies of LHMs (and electromagnetic metamaterials in general) have been in the linear regime of wave propagation and have already inspired new types of microwave circuits and devices. The results of these studies have already been the subject of numerous reviews and books.This review covers a less explored but rapidly developing area of investigation involving media that combine nonlinearity (dependence of the permittivity and permeability on the magnitude of the propagating field) with the anomalous dispersion exhibited by LHM. The nonlinear phenomena in such media will be considered on the example of a model system: the nonlinear left-handed transmission line. These nonlinear phenomena include parametric generation and amplification, harmonic and subharmonic generation as well as modulational instabilities and envelope solitons.

Parametric amplification in left-handed transmission line media

We introduce active negative-index metamaterials based on left-handed nonlinear transmission line media and measure a greater than 10dB amplification of a weak signal wave at the output of the transmission line due to its parametric interaction with an intensive pump wave, by which energy in a pump wave at one frequency is transferred to the energy in a weak signal wave at another frequency.

Combined Left- and Right-Handed Tunable Transmission Lines With Tunable Passband and 0

We combine a right-handed (RH) and a left-handed (LH) nonlinear transmission line (NLTL) to realize a new frequency and phase-tunable bandpass filter (BPF). An RH NLTL is a voltage-controlled low-pass filter and an LH NLTL is a voltage-controlled high-pass filter, so combining both allows for simultaneous and independent control over the low and high cutoff frequencies of the passband. Also, by using the positive phase propagation of a RH NLTL and the negative phase propagation of an LH NLTL, control over the phase propagation in the passband can be achieved. In the fabricated circuit, the controllable low cutoff frequency is from 480 to 721 MHz and the high cutoff frequency is from 625 to 1005 MHz. Also, we note that whatever the passband is, the phase propagation close to the center frequency is 0deg

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We report the experimental observation of the self-generated stationary trains of envelope solitons in the left-handed nonlinear transmission line metamaterials. The trains of both bright or dark solitons, as well as switching between them, have been experimentally demonstrated in short transmission lines exhibiting strong and fast nonlinearity and strong anomalous dispersion, when pumped with a continuous wave signal.

Phase Shift

We demonstrate experimentally a mechanism of the soliton generation in nonlinear active metamaterials. Our meta-structure consists of a ring resonator formed by a microwave amplifier loaded with a left-handed transmission line. We demonstrate a variety of nonlinear effects not described by weakly nonlinear models, and study experimentally the systems spatiotemporal dynamics, including the generation of envelope solitons being realized only for the backward-wave regime.

Trains of envelope solitons in nonlinear left-handed transmission line media

We construct a synthetic left-handed transmission line with cascaded varactors and shunt inductors. By modulating dc bias, the capacitance of the varactors can be changed and modulation of the output phase state is possible. For frequencies from 4.7 to 6.4 GHz, a very linear phase variation versus voltages of over 200deg phase variation with low insertion-loss variation (plusmn0.5dB) is demonstrated. This circuit can also act as an efficient harmonic generator when a large signal is applied. Since the left-handed transmission line shows high-pass filter response, harmonics generated are not seriously attenuated. However, because this synthetic transmission line is a very dispersive medium, strong dispersions and instabilities may arise. The circuit size is determined by the diode size and lumped-element inductor, allowing it to be compact