- Harmonic Trust Spectrum Modeling for Cognitive Radio Intrusion Detection
- Adaptive Entropy Prediction-based Lossless Compression for Efficient Data Transmission in Terrestrial and Underwater IoT Systems
- A Spatio-temporal Residual Attention Network with SNR-adaptive Weighting for MIMO-OFDM Channel Estimation
- Communication-efficient Embedded FFT Processing for Acoustic Telemetry in LPWAN-based Beehive Monitoring Systems
- FEC Hybrid Method Based on Reed–Solomon Codes for Transmitting Video Signal Over Limited Bandwidth and High Loss Rate Channels
- Dual Wide-band Microstrip Antenna for Wireless Communication Systems
- Network Threat Detection in IaaS Environments Based on Flow Log Data
- Machine Learning-based Automatic Modulation Classification for 5G-Advanced and 6G Waveforms: Robust Identification Under Realistic Channel Impairments
- Energy-delay Aware Data Collection in Mobile Sink-based Wireless Sensor Networks with Optimized Visiting Points and Two-level Data Aggregation
No. 1 (2002)
Published:
2002-03-30
Full Issue
ARTICLES FROM THIS ISSUE
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PHEMT transistor models for accurate CAD of MMIC amplifier
Abstract
Selected models of PHEMT transistors are presented for the popular Philips D02AH process. The models are based on a set of measurements of transistor parameters and have been verified against measurements of fabricated MMIC amplifiers. The usefulness of particular models for the CAD of microwave circuits is discussed.
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MOVPE InP based material for millimeter and submillimeter wave generation and amplification
Abstract
The potential of the MOVPE growth process for millimeter and submillimeter wave generation and amplification is presented. The increase in layer quality, the improved homogeneity and purity, the precision of mono-layers growth and wide spectrum III-V compounds makes MOVPE techniques very attractive for modern device applications. The characterisation results of the heterostructures dedicated for HBV varactors and 2-DEG transistors (HEMT) are described.
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The 100 W class A power amplifier for L-band T/R module
Abstract
In the paper a balanced high power amplifier with class A silicon bipolar transistors for L-band T/R module is described. The amplifier was designed for maximum power and minimum transmitance distortions. The obtained parameters of the amplifier are as follow: output power at 1 dB compression P1 dB > 49 dBm, linear gain |S21| > 10 dB, and transmitance deviations during the RF pulse: delta phase arg(S21)<0.90 deg. and Pout<0.2 dB.
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Photovaractor performance for optically controlled microwave circuits
Abstract
The photovaractor for optically controlled microwave circuits was designed and studied. The photovaractor module was fabricated as a planar p-i-n photodiode chip placed in a fibre optic matching receptacles. Study of C-V characteristics in the light illumination mode has shown that capacitance characteristics are strongly dependent on the light illumination power. These variations of the photovaractor diode capacitance are large enough to be used in optically controlled circuits such as oscillators, mixers and switchers.
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Optical-microwave transmission system with subcarrier multiplexing for industrial measurement systems
Abstract
We describe short-distance three-channel optical-microwave link with subcarrier multiplexing for transmission digital and/or analog data between different points of industrial measurement systems. The optical fiber link operates with Fabry-Perot laser at 1300 nm, multimode fiber and PIN photodiode receiver. From microwave point of view three carriers with frequencies 600 MHz, 800 MHz and 1000 MHz were chosen. The structure and main parameters of a link are reported and discussed.
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Microwave harmonic generation in fiber-optical links
Abstract
Optical transmission of microwave (MW) and millimeter-wave (MMW) signals has become an intensive research area in the last decade. There is a growing interest in optical processing of MW signals [1, 2], phased array applications [3] and wireless distribution of broadband data in fiber-fed MMW subscriber access systems [4 - 10]. This paper extends the existing models of MW/MMW optical links that are based on optical intensity [10, 11]. The model is suitable for estimating harmonic levels of the MW modulation signal generated in the optical path. Considering a MW fiber-optic link both the optical transmitter and the receiver are responsible for harmonic generation. Furthermore, the optical fiber itself inserted between the transmitter and receiver induces harmonics due to dispersion. Exact modelling of harmonic generation requires a calculation based on the optical field instead of on a purely intensity basis [12 - 14].
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Lowering the uncertainty in fast noise measurement procedures
Abstract
To completely characterise the noise behaviour of a two port device, four noise parameters Fmin, Rn, Gopt and Bopt must be determined. This paper reports improvements in the uncertainty related to the above parameters, taking into account measurement errors due both to the limited instrument precision and connection repeatability. Results are reported for noise characterisation of 0.3 µm delta-doped HEMT devices by Alenia, demonstrating as the common hot-cold measurement procedure can result with an error confidence as low as 0.2% for all the noise parameters.
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A method for evaluation of uncertainties of noise parameter measurement
Abstract
The assessment of uncertainties of a two-port noise parameters measurement, presented in the paper, relies on modeling of sources of errors and an investigation of propagation of the errors through a measurement system. This approach is based on a simplified additive error model and small-change sensitivity analysis. The evaluated uncertainties agrees with those observed in experiments. This method may be implemented in automatic noise measurement systems for on-line uncertainty assessment and for optimization of the design of an experiment.
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Estimation of internal distribution of temperature inside biological tissues by means of multifrequency microwave thermograph
Abstract
The paper presents problems connected with thermal radiation of human bodies in microwave range in aspect of diagnosis breast carcinoma. A mathematical model of transmission thermal radiation through tissues is introduced and methods of measurement of temperature, depth and size of heat source, by means of multifrequency microwave thermograph [1-7], are described. Theoretical considerations are supplemented with presentation of result experiments.
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Whispering gallery resonator method for measurements permittivity
Abstract
The new method of measuring permittivity is described. The measurements are performed using whispering gallery mode open dielectric resonators. The accuracy is assured by applications of the mode matching method. Three resonant modes (HE511, HE611 and HE711) are used in measurement procedure. Accuracy of the method is much better than 0.3% for the relative permittivity having values from 20 to 50.
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Low order autoregressive models for FDTD analysis of microwave filters
Abstract
The forward-backward autoregressive (AR) model is applied to extract time signatures generated by the FDTD algorithm. It is shown that using simple techniques of model parameters selection one is able to reduce the model complexity for low and medium Q circuits.
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Propagation in rectangular waveguides with a pseudochiral Omega slab
Abstract
The transfer matrix approach is applied for analysis of waveguides loaded with a uniaxial pseudochiral Omega slab. In particular a pseudochiral parallel plate and rectangular guides are investigated. Based on the numerical analysis the influence of the pseudochirality on propagation characteristics and field distribution are examined. Other feature such as a field displacement phenomenon appearing in the both considered structures due to the pseudochirality is also discussed.
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Recognition of narrowband radio signals using autoregressive models and pattern comparison approach
Abstract
This paper presents an improved spectral recognition method for digitally modulated radio signals. It is based on a signal autoregressive (AR) model. Model poles are used as signal features for neural network based on recognition process. To reduce an influence of the signal noise and distortions introduced by the digital receiver, a nonlinear Z plane transformation is proposed.
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Optical gain in one-dimensional photonic band gap structures with n-i-p-i crystal layers
Abstract
The gain enhancement in a layered periodic photonic band gap structure containing active medium based on GaAs n-i-p-i superlattices separated by AlGaAs layers is analyzed. The dependences of extinction coefficient and refractive index on excitation level and wavelength are presented. Transmission characteristics of a probe light versus excitation level are calculated. It is shown that the threshold of generation can be essentially reduced if the wavelength of probe light falls to the band gap edge.
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New multimedia and telematic tools for asynchronous distance learning
Abstract
New tools of modern education, connected mainly with Internet, are described in the paper. Their characteristics, principles of application were discussed in succession. Evaluation trail of their usefulness was done. Possibilities of carrying on laboratory experiments and distance designing were described. Probe to foresee directions of further development of Internet tools in the educational process was done.
