Showing papers on "L band published in 2019"

L -Band GHz Femtosecond Passively Harmonic Mode-Locked Er-Doped Fiber Laser Based on Nonlinear Polarization Rotation

Abstract: Via using an L -band optimized in-fiber polarizing grating device, a GHz L -band femtosecond passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation is first demonstrated. In total, 4.22 GHz pulses with the duration of 810 fs and super-mode suppression ratio (SMSR) of 32 dB are obtained under the pump power of 712 mW corresponding to 215th harmonic order. The central wavelength of 4.22 GHz pulses is 1581.7 nm with 10.1 nm 3 dB bandwidth. Furthermore, under this fixed pump power, higher harmonic orders can also be attained by rotating the polarization controllers properly. The highest repetition rate we obtained is 7.41 GHz with the SMSR of 20.7 dB.

Mobility, Thickness, and Hydraulic Diffusivity of the Slow-Moving Monroe Landslide in California Revealed by L-Band Satellite Radar Interferometry

Abstract: Active landslides cause fatalities and property losses worldwide. Landslide behaviors can be enigmatic in natural landscapes and therefore require high‐quality observations of their kinematics to improve our ability to predict landslide behavior. Here we use geodetic interferometric synthetic aperture radar (InSAR) observations to characterize the geometry and the spatio‐temporal deformation of the slow‐moving, deep‐seated Monroe landslide in northern California between 2007 and 2017. InSAR phase discontinuities show that the landslide is bounded by discrete strike‐slip faults at the lateral margins and segregated into distinct kinematic elements by normal and thrust faults. We find that the Monroe landslide has been moving consistently, with a maximum rate of about 0.7 m/year in the narrowest longitudinal center of the transport zone. The thickest landslide mass is estimated to be in a zone located between subsiding and the uplifting kinematic elements at the lower transport zone. The timing andmagnitude of the landslide displacement aremodulated by the intensity and duration of precipitation, aswell as the antecedent water content of the landslide mass. In addition, we use a one‐dimensional pore‐water pressure diffusion model to estimate the rainfall‐modulated pore‐water pressure changes and hydraulic diffusivity. We find hydraulic diffusivity values between 6:8−2:0 þ2:9×10 −5 m/s, which agrees with ground‐based measurements in this region. Displacement measurements on the hillslopes obtained from geodetic InSAR observations allow us to characterize the mobility, depth, and hydraulic diffusivity of slow‐moving landslides.

Modulation Format Dependent, Closed-Form Formula for Estimating Nonlinear Interference in S+C+L Band Systems

Abstract: A closed-form formula for the nonlinear interference estimation of arbitrary modulation formats in ultra-wideband transmission systems is presented Enabled by the proposed approach, the formula is applied to the entire S+C+L band (20 THz) and validated by numerical simulations with experimentally measured fibre data

Compact ${L}$ -Band Relativistic Magnetron With Diffraction Output of TEM Mode

Abstract: A compact ${L}$ -band relativistic magnetron (RM) with the diffraction output (DO) of the TEM mode is proposed. In this DO configuration, a ridged circular waveguide is used to replace the cylindrical waveguide to decrease its radial dimension. The RF field of the operating $\pi $ -mode is extracted from every resonator cavity and guided to the ridged circular waveguide. Even at the operating frequency of 1.55 GHz, the ridged circular waveguide can reduce the cutoff radius of the RF wave to 73 mm. The output RF field is further effectively converted to the TEM mode by a compact mode converter. Moreover, in the resonant system, a 10-cavity rising-sun slow wave structure (SWS) is applied to lower the phase velocity of the operating spatial harmonic and enhance the mode separation between the operating mode and the adjacent mode. The particle-in-cell (PIC) simulations demonstrate that the practical RM could output a relatively pure TEM mode at the frequency of 1.55 GHz, and its total efficiency is up to 60% with gigawatt radiation power for a diode voltage of 400 kV.

Highly efficient dual-band GaN power amplifier utilising pin diode-based tunable harmonic load matching

Abstract: This study presents a tunable dual-band gallium nitride (GaN) power amplifier (PA) operating in L-band. The first band is aimed near the lower edge of the L-band, 1 GHz, and the second band is aimed near the upper edge of the L-band, 2 GHz, which is located around the second harmonic of the first band. A pin diode-based tunable load matching circuit is proposed and designed in order to present the optimum fundamental and harmonic load impedances to the transistor in both operating bands for maximum efficiency and output power. A method of controlling the tunable load matching circuit according to the input frequency is proposed by the design of a band-selective power detection circuit incorporated into the source matching circuit of the PA. The implemented PA delivers 41.5 dBm output power with 81.3% drain efficiency (DE) at 920 MHz and 41 dBm output power with 60.2% DE at 1720 MHz.

A 21 cm pilot survey for pulsars and transients using the Focal L-Band Array for the Green Bank Telescope

Abstract: Phased Array Feed (PAF) receivers are at the forefront of modern day radio astronomy. PAFs are currently being developed for spectral line and radio continuum surveys and to search for pulsars and fast radio bursts. Here, we present results of the pilot survey for pulsars and fast radio bursts using the Focal plane L-band Array for the Green Bank Telescope (FLAG) receiver operating in the frequency range of 1.3--1.5 GHz. With a system temperature of $\sim$18 K, the receiver provided unprecedented sensitivity to the survey over an instantaneous field of view (FoV) of 0.1 deg$^{2}$. For the survey, we implemented both time and frequency domain search pipelines designed to find pulsars and fast radio bursts that were validated by test pulsar observations. Although no new sources were found, we were able to demonstrate the capability of this instrument from observations of known pulsars. We report an upper limit on the rate of fast radio bursts above a fluence of 0.36~Jy ms to be 1.3 $\times$ 10$^6$ events per day per sky. Using population simulations, we show that the FLAG will find a factor of 2--3 more pulsars in same survey duration compared to its single pixel counterpart at the Green Bank Telescope. We also demonstrate that the new phased array receiver, ALPACA for the Arecibo telescope, will be a superior survey instrument and will find pulsars at a higher rate than most contemporary receivers by a factor of 2--10.

Database of Crustal Deformation Observed by SAR: Improving Atmospheric Delay Mitigation for Satellite SAR Interferometry and Developing L-Band Multi-Type Portable SAR

Abstract: Spaceborne synthetic aperture radar (SAR) and ground-based radar interferometers (GBRIs) can be used to detect spatially detailed crustal deformations that are difficult to detect by on-site observations, the Global Navigation Satellite System, tiltmeters, and so on. To make such crustal deformation information readily available to those engaged in evaluating volcanic activities and researching the mechanisms, we are preparing a database within the Japan Volcanological Data Network data sharing system to store crustal deformation detected by spaceborne SAR and GBRIs (Subtheme 2-1, Project B, the Integrated Program for Next Generation Volcano Research and Human Resource Development). In this study, we examined methods to reduce atmospheric delay noise in SAR interferometry using the numerical weather model and determined the methods for resampling the analytical values of the numerical weather model and estimating atmospheric delay to efficiently determine atmospheric delay. We show that the atmospheric delay can be estimated with higher accuracy by properly combining the isobaric surface and ground surface data of the mesoscale model (MSM) provided by the Japan Meteorological Agency. We are developing a multi-type portable SAR system as a GBRI system such that it would allow campaign observations whenever increased volcanic activities are observed and acquire crustal deformation with a higher temporal resolution than spaceborne SAR for storage in the database. This system employs L-band radar, which has a higher penetrability against vegetation. Two modes of observations are possible: ground-based SAR and car-borne SAR. The prototype was fabricated to conduct experiments necessary to develop a working model. The experimental observations was carried out around Asama volcano, and we confirmed that clear fringe was obtained.

Small-Size Wide-Band Low-Profile “Pixel Antenna”: Comparison of Theoretical and Experimental Results in L Band

Abstract: This paper presents a small (≈λ/2 × λ/2) low-profile (λ/10) planar antenna built to work on a very large frequency band (≥40%) for applications in Telecom, Radar, IoT, etc. is antenna is called a "Pixel Antenna" because it was first used as a pixel in an agile beam radiating surface. In this paper, the pixel antenna is used alone to design multiband or wide-band antennas keeping the same radiation pattern and polarization throughout the band. e working principle used to design the Pixel Antenna is deduced from the well-known EBG (electromagnetic band gap) antenna in its low-profile version which already has a bandwidth close to ≈20%. e aim of this present work is to double this bandwidth by simultaneously feeding two modes of the original EBG material. e theoretical and experimental results are compared for an L band application, exhibiting bandwidth from 1 GHz to 1.52 GHz (41%). In addition, good radiation patterns of pixel antenna stay constant over the entire useful band without any degradation of the antenna performance. is proposed antenna design can be used to obtain wide bandwidth for any chosen frequency band (S band, X band, C band, etc.) using frequency scaling.

Low-Cost L-Band Receiving System Front-End for Irbene RT-32 Cassegrain Radio Telescope

Abstract: Abstract Irbene RT-32 radio telescope is one of the main instruments operated by Ventspils International Radio Astronomy Center (VIRAC), which is used for participation in VLBI and single-dish mode observations, including European VLBI Network (EVN) and other astronomy projects such as recently started research on small bodies of solar system, which involves weak spectral line detection at L-band. Since start of the operation as a radio telescope, single C-X band receiver has been available at RT-32, but regular demand for L-band frequencies has been received due to its importance in spectral line science. In case of RT-32 geometry, optimum dimensions of L-band feed antenna system are inconveniently large and its installation without significant feed cone rebuilding is complicated. While work is currently ongoing to redesign the feed cone for multiple receiver support and to develop high performance L-band feed system, temporal, compact and low-cost receiver has been built and installed laterally to secondary focus, which in sense of performance and functionality has been proven to be appropriate for most of the current needs. Receiver is based on small parabolic reflector allowing one to use a compact dual circular polarized horn antenna, which together with a Cassegrain antenna forms a three-mirror system. Front-end is uncooled that allows reducing operational and maintenance costs, while still providing acceptable noise performance. Practical tests show average overall sensitivity of 750 Jy at 1650 MHz in terms of system effective flux density (SEFD). The paper describes the development of the receiver and presents the main results of performance characterization obtained at Irbene RT-32.

The LNA Design for Future S Band Satellite Navigation and 4G LTE Applications

Abstract: A good design of LNA for S band satellite navigation receivers and 4G LTE wireless communication system has been implemented in this paper. Due to increased congestion in the present L band, the S Band frequency from 2483.5 - 2500 MHz has been allocated for the future satellite navigation systems. For this purpose ATF-34143 amplifier (pHEMT) having high electron mobility and fast switching response has been chosen due to its very low Noise Figure (NF). The amplifier has been designed having bandwidth of 8 GHz from 1.8 – 2.6 GHz. Because of the large bandwidth, the amplifier could serve many wireless communication applications including 4G LTE mobile communication at 2.1 GHz. The design was implemented using the micro strip technology offering extremely low noise figure of 0.312 dB and 0.377 dB for 2.1 GHz and 2.49 GHz respectively. The gain of the amplifier was low and found to be 10.281 dB and 9.175 dB. For the purpose of increasing the gain of an amplifier, the proposed LNA design was then optimized by using Wilkinson Power Divider (WPD). The Balanced LNA design using WPD offered very low noise figure of 0.422 dB and 0.532 dB respectively and the gain was considerably increased and was found to be 20.087 dB and 17.832 dB respectively against 2.1 GHz and 2.49 GHz. Simulations and measurements were taken in Agilent Advanced Design System (ADS) software. The suggested LNA can be used for a variety of wireless communications applications including the future S band satellite navigation systems.

An L -Band Brightness Temperature Disaggregation Method Using S -Band Radiometer Data for the Water Cycle Observation Mission (WCOM)

Abstract: The water cycle observation mission (WCOM) will build upon previous L and C band passive microwave soil moisture satellite missions. WCOM will consist of a passive microwave synthetic aperture radiometer operating at L , S , and C bands. The WCOM requirements for passive soil moisture are to estimate soil moisture in the top 5 cm of soil layer with an error less than 0.04 m3/m3, at 15-km resolution and with a 3-day revisit. A new set of algorithms for these multi-frequency platforms will need to be developed for estimating the data products at the desired resolution. To accomplish this, a brightness temperature (TB) downscaling methodology is developed that uses passive S -band TB (30 km) to downscale L -band TB (50 km) and to estimate soil moisture at a 30-km resolution, based on the linear relationships between the passive signals of L band and S band. To test this downscaling method, analysis was performed using PALS data from the Soil Moisture Experiments in 2002 (SMEX02). For this study, 4-km L -band observations were downscaled to 800 m. The root mean square errors between the downscaled TBL at 800 m with the observed TBL at 800 m are 2.63 and 1.60 K for H and V polarizations, respectively. The results also showed that it was possible to use these disaggregated TB to estimate soil moisture to meet the mission requirement of 0.04 m3/m3. These results showed that we can obtain higher resolution soil moisture from the L -band passive TB with a high accuracy ( S -band information.

Shared-aperture dual-band orthogonally polarised antenna array for L-band and S-band applications

Abstract: In this work, a novel dual-band orthogonally polarised, the shared-aperture array is proposed for the L-band and S-band frequencies. An elliptical monopole antenna is used as a radiating element in the proposed array. In this design, the common inter-element spacing is used for both the bands. Owing to this, L- and S-band arrays have the same number of elements. The L-band radiators are closely placed and designed taking the mutual coupling into account. The S-band antenna follows the traditional array design process. The inter-band coupling is reduced by using a metallic ridge in the reflector of the array. This array can be used in the dual-band radar applications. The proposed methodology offers the modular, low-profile and low-cost solution for a large array. To verify the proposed concept, a prototype array of 4 × 4 elements for each band has been fabricated and tested.

Multi-Beam Frequency Tunable Antenna based on Plasma-Nested Helix

Abstract: A frequency tunable antenna supporting multiple beams based on plasma technology is presented in this letter. Key components of the proposed antenna are an axial mode helical antenna and a nested plasma column antenna inside the helix. The antenna has the potential to operate in the frequency range of VHF (200-400 MHz), with a broadside radiation pattern and L band (900-1500 MHz) with an end fire radiation pattern. The proposed structure has the ability to restrict its performance in the only L band frequency range. The radiation characteristics are analyzed and investigated using the finite integral technique.

FAST Detects Multiple Bursts in L-band from FRB 121102

Abstract: Tracking observations of FRB 121102 were carried out with the newly commissioned Five-hundred-meter Aperture Spherical radio Telescope (FAST). We used the FAST L-band Array of 19-beams (FLAN), which has a FWHM of 2.95' for individual beams and a 26' footprint.

Impact of Permittivity Patterns on Fully Polarimetric Brightness Temperature Signatures at L-Band

Abstract: This study investigates the sensitivity of L-band (1.41GHz) polarimetric brightness temperature signatures to oriented permittivity patterns, which can occur for example in the case of row and interrow soil moisture differences in agricultural fields. A field experiment and model simulations are conducted to verify the effects of such patterns on all four Stokes parameters. We find that for an artificial target resembling idealized model conditions, permittivity patterns lead to systematic brightness temperature modulations in dependency of the azimuthal look angle. For the specific field setup, modulations reach amplitudes of ∼ 4K and mostly affect h-polarized brightness temperatures as well as the first, second, and third Stokes parameters. Simulations of soil moisture patterns under idealized model conditions indicate even higher amplitudes (up to 60K for extreme cases). However, the effects occur only for permittivity layer widths of up to 8 cm (given the observing wavelength of 21 cm), which is lower than the row and interrow widths typically observed in agricultural settings. For this reason, and due to the idealized model geometry investigated here, future studies are needed to transfer the findings of this study to potential applications such as the sensing of oriented soil moisture patterns. Particular interest might lie in radiometry and reflectometry in lower frequency ranges such as P-band, where according to the threshold established here (8/21 wavelengths), permittivity layer widths of up to ∼ 45 cm could be observed.

6 kW L-band pulsed MBK with broad frequency band of 15%

Abstract: $L$ -band MBK with frequency band of 15% and output power of $\pmb{6}\mathbf{kW}$ that employs the new technology of decreasing cavity sizes was designed at VDBT. Two samples of MBK were fabricated and successively tested. The diameter of MBK is no more than a half of wavelength.

An L-Band Bandpass Filter with Narrow Bandwidth and Miniature Based on LTCC Technology

Abstract: In this paper, in order to meet the requirements for miniaturizing a microwave frequency conversion module, an L-band filter with narrow band and high out-of-band rejection is designed based on LTCC technology. The values of each element in the simplified schematic diagram are used with Chebyshev type function being the prototype, and the shapes and layout of the elements are reasonably designed for effectively utilizing the electromagnetic coupling effect inside the structure. The actually processed filter has a bandwidth of 20 MHz, and its out-of-band rejection reaches 39 dB and 42 dB at 1GHz and 1.6 GHz, respectively.

Engineering Flat Gain Tunable Raman-Parametric Hybrid L-Band Amplifier for Narrow Band Multi-Channel Terabits System

Abstract: Abstract We present a model of a Raman-parametric hybrid amplifier for flat gain amplification of narrowband Dense Wavelength Division Multiplexed (DWDM) terabits capacity system. In the proposed configuration Raman pump has been cascaded with one – pump parametric amplifier. While Raman amplifier typically uses a long length single mode fiber as a gain medium, the Fiber Optical Parametric Amplifiers (FOPA) uses a small length of Highly Non-Linear Fibers (HNLF). This allows for maximum optimization of the gain achieved using Raman as well as parametric processes. We focus on the signal degradation due to non-linear crosstalk arising because of multi-pump configuration, in particular, due to the generated idlers within the operational bandwidth. As the channel spacing is reduced, fiber non-linearities increase significantly. The dilemma to use the fewer number of high powered pumps Vs, the use of increased number of relatively low powered pumps has been investigated for DWDM system. The optimization of the pump powers has been evaluated in terms of signal degradation, gain, gain variation and OSNR. It has been demonstrated that a maximum gain of 45.38 dB for 96×40 Gbps, 25 GHz system is attainable up to 200 km of transmission distance while maintaining OSNR>18 dB using the proposed hybrid. No gain compensation or gain optimization technique has been used. The findings of this work establish flat gain in narrowband DWDM systems is achievable through proper optimization of pump wavelengths and their powers.

A High-Order L-Band HTS Filter for Sensitive Detecting

Abstract: In this paper, a new high-temperature superconducting (HTS)-based microwave radiometer with an improved sensitivity is presented. The cryogenic receiver front end consists of an HTS filter and a cryogenic low noise amplifier (LNA). The cryogenic receiver front end shows an ultra-low noise figure and can suppress radio frequency interference (RFI) effectively. The proposed HTS filter works at a center frequency of 1.4135 GHz with a bandwidth of 25 MHz. The measured mid-band insertion loss, side band steepness, and out-of-band attenuation of the HTS filter are 0.14 dB, 35 dB/MHz, and 80 dB, respectively. The noise figure of the cryogenic LNA is about 0.27 dB at a temperature of 77 K. Compared with other total power radiometers, the proposed radiometer has a lower receiver noise temperature, which can improve the sensitivity with a short integration time of the satellite-based salinity meter. In addition, since the bandwidth of the salinity meter is fixed and the integration time of satellite-based equipment is limited, such a low receiver noise temperature can increase the flexibility of future satellite payload configuration program.

Measurements and model for the satellite-to-aircraft channel in L-band

Abstract: Wireless radio transmission from a satellite-based emitter to a receiver located on an aircraft is of interest for many applications such as internet access for passengers, air traffic management or positioning by global navigation satellite systems especially when a worldwide service shall be granted. In particular, the last two mentioned applications are related to the safety of life requiring realistic and accurate channel models for software-based system testing. State-of-the-art channel models for the satellite-to-aircraft case lack of accuracy in terms of modelling all propagation impairments. In this contribution, the authors describe airborne propagation experiments using Global Positioning System signals for channel sounding, the data evaluation and the derived channel model.

A Novel Broadband Dual Circularly Polarized GNSS Antenna

Abstract: In this paper, an innovative antenna for positioning, surveying and navigation is described. It receives both the right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) signals simultaneously and with high isolation. The antenna covers all GNSS (Global Navigation Satellite Systems) frequencies in L band, shows excellent performance in open-sky environments and clearly detects signals which have been corrupted by diffraction and reflections. There are no such products on the market at the present time.

Quantum communication method and related apparatus

Abstract: In the embodiments of the present disclosure, a transmit apparatus generates a to-be-processed optical signal and a quantum optical signal, where the to-be-processed optical signal includes at least a classical optical signal; and the transmit apparatus couples the to-be-processed optical signal and the quantum optical signal, to obtain a coupled optical signal, and sends the coupled optical signal. Because a wavelength of the classical optical signal is in an L band and/or a C band and a wavelength of the quantum optical signal is in an S band, a wavelength in the band of the classical optical signal is greater than a wavelength in the band of the quantum optical signal.

High Gain Wideband Air Strip-Line Fed Antenna For High Power Applications

Abstract: This paper introduces a high power and wideband antenna in L band microwave frequencies. In the antenna configuration, an air suspended stripline (SSL) is used as dielectric medium to have maximum power handling capability. The proposed antenna is inspired from a fork like monopole shape The antenna structure is made from aluminum sheets to have the advantage of low cost. The antenna structure and the excitation transition from coaxial cable to SSL were designed. The antenna functionality was validated using 3D simulation. The results indicate that the antenna is a wideband antenna with good matching properties, omnidirectional pattern, and high radiation efficiency over the frequency band (1.4 GHz to 5 GHz).

Verification of the results of numerical simulations of a high power pulsed L-band magnetron in experimental conditions

Abstract: Kubara Lamina is working on the development of a new type of pulsed-power magnetron with megawatts output power operating in the L-band. An important part of the design work are computer simulations of electromagnetic interactions with an electric charge. In order to get the most reliable results, the task was carried out with the help of specialized calculation software from two independent producers - CST Studio Suite and MAGIC Tool Suite. The results obtained with the help of both programs were similar, but there were differences between them resulting from the specific features of the software. The differences concerned the time needed to create an electron spokes in the interaction area between the cathode and anode of the tube as well as the threshold voltage at which the generation of high frequency oscillation began. On the basis of numerical simulations, the optimal geometrical dimensions of individual details were obtained and the magnetron prototype was created. The tube was subjected to laboratory tests under dynamic conditions. To ensure proper input power parameters, a dedicated impulse modulator powered from supercapacitors batteries was constructed. The energy of the electromagnetic wave generated during the dynamic operation of the device was absorbed in the waveguide ended with high power load. The test results obtained under the experimental conditions allowed to verify the structure of the model designed using simulation software. Tests in the available power range of the power supply confirmed very good compatibility of the tube parameters with the results of electromagnetic simulations. An additional advantage of carrying out the simulation was the shortening of the design process, because the first model of the device already worked in accordance with the technical assumptions.

Design of L-band Linear Phased array with Dual Polarized Dipole Antenna

Abstract: This paper presents a L-band linear phased array antenna with 9 dual-port dipoles and printed baluns for polarization diversity. The polarization of the antenna (dual-port dipole) can be reconfigured from linear to circular by changing the input phases of each element. The design satisfies some targeted specification such as a gain of 13 dB and a steering coverage of 90° in the complete bandwidth of 1.1 GHz to 1.3 GHz. To validate the simulated results, the linear array is manufactured and measured results are compared with simulated ones. The antenna array performance in terms of active reflection, radiation pattern, side lobe levels (SLL) and steering coverage has been analyzed.

Modernized Solar Radio Spectrograph in the L Band Based on Software Defined Radio

Abstract: The paper presents the concept, implementation, and test operation of a modernized solar radio spectrograph for an investigation of the solar emission and solar bursts in radio frequency bands. Besides having a strong diagnostic significance for studying the flare energy release, the solar radio bursts can also cause strong interference for radio communication and navigation systems. The current spectrograph for the Ondrejov observatory (Astronomical Institute of Czech Academy of Sciences) was modernized by using a direct-conversion receiver connected to a field-programmable gate array (FPGA) for the fast Fourier transform (FFT) spectrum estimation and put into the test operation. The higher time and frequency resolution and lower noise in comparison with the existing analog instrument were reached by the implementation of the latest optimal signal processing methods. To reduce the costs for such modernization, the operating frequency range was divided into four sub-bands of bandwidth 250 MHz, which brings another benefit of greater scalability. The first observations obtained by the new spectrograph and their comparison with the analog device are presented in the paper with future steps to put the spectrograph into the regular operation.

Forest vegetation Interaction with L-band Satellite Signals

Abstract: A method for calculating the electro-physical parameters of forest vegetation cover interacting with the signals of navigation satellites in the frequency bands 1.2-1.6 GHz is proposed. A technique for the experimental measurement of linear attenuation coefficient of satellite signals on test areas of canopies was developed, taking into account their calibration at the input. The proposed forest vegetation model describes the group of crowns as a system of quasi spherical "capsules", located chaotically in the air matrix. The scattering and penetration cross sections and the coefficient of linear attenuation of radio waves were calculated using the approximation of anomalous diffraction for crowns and the results of solving the diffraction problem for trunks. The effects of multiple scattering were taken into account.