Ka-band Microwave Research Articles

Micromorphology and electromagnetic properties of NiCuZn ferrites with Ba3Ti4Nb4O21 additives for Ka-band non-reciprocal microwave devices

Micromorphology and electromagnetic properties of NiCuZn ferrites with Ba3Ti4Nb4O21 additives for Ka-band non-reciprocal microwave devices

The characteristics of cloud macro-parameters caused by the seeder–feeder process inside clouds measured by millimeter-wave cloud radar in Xi'an, China

Abstract. The seeding effect of upper clouds on lower clouds affects the evolution of clouds, especially the seeding from upper ice clouds on lower stratiform clouds or convective clouds, which can stimulate the precipitation of lower clouds and even produce extreme precipitation. When seeders of the seeding cloud enter the feeding cloud, the interaction between cloud particles results in the change in macro- and micro-parameters of the feeding cloud. Based on the observation data of a ground-based Ka-band millimeter-wave cloud radar (MMCR) and microwave radiometer (MWR) in spring and autumn from 2021 to 2022, the seeder–feeder phenomenon among double-layer clouds in Xi'an, China, is studied. The study on 11 cases of seeder–feeder processes shows that the processes can be divided into three types by defining the height difference (HD) between the seeding cloud base and the feeding cloud top and the effective seeding depth (ESD). Through analysis of the reflectivity factor (Z) and the radial velocity (Vr) of cloud particles detected by the MMCR and on the retrieved cloud dynamics parameters (vertical velocity of airflow, Va, and terminal velocity of cloud particles, Vf), it is shown that the reflectivity factor and particle terminal velocity in the cloud are significantly enhanced during the seeder–feeder period for the three types of processes. But the enhancement magnitudes of the three seeder–feeder processes are different. The results also show that the impact of seeding on the feeding cloud is limited. The lower the height and thinner the thickness of the HD, the lower the height and thicker the thickness of the ESD. On the contrary, the higher the height and the thicker the thickness of the HD, the higher the height and the thinner the thickness of the ESD.

Facile preparation of polyvinyl chloride/activated carbon thin-film composites and study of their microwave absorption at Ka-band frequencies

Poly(vinyl chloride) (PVC) and activated carbon (AC) powders were hot-pressed into (PVC)100– x /(AC) x thin-film composites (TFCs), where x = 0.2–30 wt%. The nanostructure, morphology, and composition of AC were investigated by TEM, SEM, and EDX. The thermal stability and surface carbon-oxygen groups of the AC filler were determined by thermolysis in air and vacuum. The AC effect on the (PVC)100– x /(AC) x TFCs transparency to the electromagnetic radiation (EMR) was demonstrated at Ka-band microwave frequencies. Characteristically, the EMR reflection of the TFCs increases with the x value. For reduced EMR reflection, these TFCs should contain only 0.2 wt% AC.

A seven-channels microwave interferometer measurement system for measuring electron density distribution in hypervelocity transient plasma flow

When a hypersonic vehicle is flying in the near space region, the strong friction between the vehicle and the air can cause the air to ionize. As a result, the plasma sheath around the vehicle and the wake flow field behind it are formed, significantly affecting the electromagnetic (EM) scattering characteristics of the vehicle and resulting in the communication blackout. Therefore, the investigation of electron density distribution of the plasma sheath and wake flow field is of the great significance in the detection, communication, etc. of the hypersonic target. In order to meet the requirements for on-ground electron density distribution measurement of the transient plasma flow fields, the feasibility of measuring electron density profile with seven-channel microwave interferometer measurement system is demonstrated in this work. The wake plasma is modeled as a non-uniform multilayer medium, and the full-wave simulation software FEKO is used to calculate the phase-shift information of EM wave transmitting through non-uniform single-layered dielectric plate, uniform and non-uniform multi-layered dielectric plates. According to the simulation results, the dielectric constant of the substrate is retrieved and compared with the preset result. The retrieved results show that it is feasible that the dielectric constant distribution of non-uniform multi-layered dielectric plate is measured by utilizing the proposed microwave interferometer system with one transmission port and seven receptions. The amplitude-phase dynamic range analysis of the proposed Ka-band microwave measurement system is also carried out. The key technologies including large instantaneous amplitude-phase dynamic range and ray tracking inversion algorithm for two-dimensional (2-D) electron density distribution are also developed. Finally, the complete scheme of Ka-band seven-channel microwave interferometer measurement system is introduced. The system includes one lens antenna to generate the required plane wave and seven open-ended waveguide receiving antennas which are asymmetrically arranged to improve the lateral spatial resolution of the system. The system exhibits the amplitude dynamic range and the phase dynamic range of over 65 dB and 180° under 1 MHz IF bandwidth respectively. The plasma electron density distributions are measured by utilizing the proposed seven-channel microwave interferometer system in the ballistic range and multi-functional shock tube. The response time of the system is smaller than 1μs, satisfying the requirement for the two-dimensional distribution measurement of the transient plasma flow field generated by the ballistic range and multi-functional shock tube. The differences between experimental and numerical results are less than 0.5 order of magnitude, and the variations in transient plasma generated in both ballistic target and shock tube equipments are well detected. The measurement range of plasma electron density is 10<sup>10</sup>－10<sup>13</sup> cm<sup>–3</sup> and the spatial resolution is better than 15mm. In addition, the proposed ray tracing method is also used to invert the two-dimensional (2D) electron density distributions of both square layered model and cylindrical layered model under identical experimental state. The results are in consistent with each other, indicating that the proposed ray tracing method can be used in the inversion of 2D electron density distribution of plasma with different shapes.

Synthesis of CoFe2O4/mesoporous-carbon hybrid nanocomposite with enhanced microwave absorption in K and Ka-band

In the present investigation, CoFe2O4/mesoporous-carbon nanocomposites were synthesized using a facile hydrothermal method and demonstrate their dual band (K and Ka-band) microwave absorption properties, where radiation from high-resolution and close-range radars, space telescopes, and wireless point-to-point microwave communication systems populates. XRD results confirmed the pure phase formation of CoFe2O4 nanoparticles. Vibrating sample magnetometer shows a decrease in magnetization value for CoFe2O4/mesoporous-carbon nanocomposites that can be attributed to the increasing contents of non-magnetic mesoporous carbon. The reflection loss of the hybrid nanocomposite reached −31 dB at a matching thickness of 2.5 mm and effective absorption bandwidth was 4.4 GHz. The enhanced microwave absorption properties derive from the synergistic effect amid dielectric and magnetic loss of mesoporous-carbon and ferrite, respectively, and better impendence matching at their interface. In addition, the dielectric loss can be associated with polarization relaxation and mesoporous carbon conductivity and the magnetic loss arises from the natural resonance of ferrite materials. The high reflection loss and wide absorption bandwidth display that CoFe2O4/mesoporous-carbon nanocomposite having admirable microwave absorption performances can be a capable candidate for stealth technology and in advanced communication systems.

Simultaneous measurements of Ka-band microwave angle of arrival and Doppler frequency shift based on a silicon DPMZM.

We propose a system for the simultaneous measurements of Ka-band microwave angle of arrival (AOA) and Doppler frequency shift (DFS) based on a high-speed silicon dual-parallel Mach-Zehnder modulator (Si-DPMZM).. An echo signal drives a sub-MZM while the combination of a phase-delay echo signal and a transmitted signal drives the other sub-MZM. Two optical bandpass filters (OBPFs) are used to select the upper and lower sidebands of the Si-DPMZM output signal, detected by low-speed photodiodes, then generating two intermediate frequency (IF) signals. Thus, both AOA and DFS (with direction) can be obtained by comparing the powers, phases and frequencies of these IF signals. The estimation error of measured AOA is less than ±3° from 0 to ±90°. Meanwhile, the DFS at 30/40 GHz were measured with an estimated error of less than 9.8 × 10-10 Hz within ±1 MHz. In addition, the fluctuation of DFS measurement is less than 3 × 10-11 Hz within 120 minutes, indicating the high stability of the system.

Modeling Phase Changing Property of VO2 for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

Vanadium dioxide (VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is characterized using the time-resolved microwave conductivity (TRMC) method for applications requiring reconfigurable microwave frequency selection. We demonstrate that TRMC is a flexible method for determining the microwave conductivity of thin film compounds of varied thicknesses that are both phase-changing and non-phase changing in nature. The method makes use of Ka-band microwave resonant waveguides to examine how thermally excited samples’ microwave conductivity changes in response to microwave-transmitted power through the system’s sensitivity factor. The sensitivity factor is illustrated by a study of incident waves (electromagnetic fields) on medium and waveguide perturbation analysis in VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin films. The TRMC measurements show a low regime in the microwave conductivity below the transition temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> ) of VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> occurs near 65°C; this is associated with the dielectric characteristics of the charge carriers and points to the presence of shallow trap electron states. Longer electron hops enhance charge mobility and, consequently, the barrier energy above <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> , where these states are thermally discharged, resulting in a high thermally triggered microwave conductivity regime. The activation energy may come from a variety of complex contributions, like polaronic self-localizations, as well as a dynamic disorder brought on by the thermal oscillations of VO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecules. The calculated conductance values are simulated in CST Studio as plane wave incidence on medium to ascertain the fields’ microwave transmission behavior and contrast it with the experimental results to validate the model. Additionally, using the derived conductivities, the characteristics of well-known materials like copper (Cu) were confirmed.

An All-Optical Ka-Band Microwave Long-Distance Dissemination System Based on an Optoelectronic Oscillator

We proposed an all-optical Ka-band microwave long-distance dissemination system based on an optoelectronic oscillator (OEO). In this system, a single tone with high spectrum purity and low phase noise is excited by an injection-locked OEO, and distributed to the remote site through the fiber loop of the OEO at the same time. The second harmonic of the reference signal modulates the round-tripping optical signal at the local site, which achieves the phase conjugator at the optical domain. At the remote end, the phase-conjugated signal is photomixed with the OEO signal to eliminated the phase offset. The proposed scheme improves the phase noise of the high frequency signal received at the remote site and reduces the photoelectric conversion loss. We demonstrated the transmissions of a 36 GHz frequency-quadrupled RF signal along a 6 km optical fiber loop, and the frequency stability is 1.069 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−14</sup> /1 s and 3.3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−16</sup> /1000 s. The single-sideband (SSB) phase noise of the received signal at the remote site is up to −130 dBc/Hz at 10 kHz offset frequency.

Beam dynamic study of a Ka-band microwave undulator and its potential drive sources

Microwave undulators (MUs) have great potential to be an alternative solution to permanent magnet undulators in a free electron laser (FEL) when shorter undulator periods are required. In this paper, the factors that affect the choice of the high-power drive sources were studied via a Ka-band cavity-type MU with a corrugated waveguide proposed for the CompactLight X-ray FEL. They include the technology of the high-power vacuum electronic devices, the quality factor of the MU cavity that was demonstrated by prototyping a short section of the MU structure, and the beam dynamic study of the electrons’ trajectories inside the MU. It showed that at high beam energy, a high-power oscillator is feasible to be used as the drive source. At low beam energy, the maximum transverse drift distance becomes larger therefore an amplifier has to be used to minimize the drift distance of the electrons by controlling the injection phase.

Inversion method of two-dimensional distribution of electron density in hypersonic model wake

The ballistic target uses a two-stage light gas gun to launch the model into a hypersonic state, and the model forms a plasma wake when flying at a hypersonic speed in the target chamber. In order to obtain the radial two-dimensional distribution of transient plasma electron density in the wake of hypervelocity model, a seven-channel Ka-band microwave interferometer measuring system is developed. In the transceiver system, a transmitting antenna achieves the plane wave irradiation plasma, and a seven-port array antenna is used to receive plane waves which are passing through the plasma: the antenna beam can completely cover the radial range of the wake. The shortest response time of measuring system is 1 s, and electron density measurement range of the interferometer measuring system is 10&lt;sup&gt;11&lt;/sup&gt;–10&lt;sup&gt;13&lt;/sup&gt;/cm&lt;sup&gt;3&lt;/sup&gt; . The plasma is often treated as layered medium in data processing of multichannel microwave interferometer. Taking into consideration the effect of refraction on the stratified interface in this work, the ray tracing (RT) method is used to establish the electromagnetic propagation model. Combined with the measurement data to construct the objective function, the genetic algorithm (GA) is used to invert the radial two-dimensional distribution of the electron density under different test conditions. The result shows good agreement with the numerical simulation under the same test state, which proves the the data processing method reliable. Then, the influence of the layered model on the calculation result is analyzed, which shows that the seven-layer model is suitable for the wake modeling under given experimental conditions, and thus maximizing the number of receiving channels and ensuring the accuracy. The RT method is used for the first time to achieve the two-dimensional distribution of electron density in the wake of hypervelocity projectile, and some rules of two-dimensional electron density distribution of the hypersonic model under given experimental conditions are realized.

Study on Retrieval Method of Two-dimensional Distribution of Hypersonic Model Wake Electron Density

The ballistic range uses a two-stage light gas gun to launch the model into a hypersonic state, and the model form a plasma wake when flying at hypersonic speed in the target chamber. In order to obtain the radial two-dimensional distribution of transient plasma electron density in the wake of hypervelocity model, a seven channels Ka-band microwave interferometer measuring system was developed. In the transceiver system, one transmitting antenna to achieve plane wave irradiation plasma, and a seven-port array antenna is used to receive plane waves which passing through the plasma, the antenna beam can completely cover the radial range of the wake. Measuring system shortest response time and electron density measurement range of the interferometer measuring system are 1&lt;teshuzifu&gt;ms and 10&lt;sup&gt;11&lt;/sup&gt;-10&lt;sup&gt;13&lt;/sup&gt;/cm&lt;sup&gt;3&lt;/sup&gt; respectively. Plasma is often treated as layered medium in data processing of multichannel microwave interferometer, consider the effect of refraction on the stratified interface, in this work, the ray tracing(RT) method is used to establish the electromagnetic propagation model, combined with the measurement data to construct the objective function, and the genetic algorithm(GA) is used to invert the radial two-dimensional distribution of the electron density under different test conditions. The result shows that it is in good agreement with the numerical simulation under the same test state, which proves the reliability of the validity of the data processing method. Then, the influence of the layered model on the calculation result is analyzed, which shows that the seven-layers model is suitable for the wake modeling under given experimental conditions, maximizing the number of receiving channels and ensuring the accuracy. RT method is used for the first time to achieve the two-dimensional distribution of electron density in the wake of hypervelocity projectile, and some rules of two-dimensional electron density distribution of the hypersonic model under given experimental conditions are realized.

Land Surface Freeze/Thaw Detection Over the Qinghai–Tibet Plateau Using FY-3/MWRI Data

The spatial extent and duration of soil freeze/thaw (F/T) control water and heat exchange, the energy cycle, and climate change. Global warming causes permafrost thawing, which increases carbon emissions and in turn exacerbates climate change. Passive microwave remote sensing has been proven to be effective in monitoring land surface F/T. However, it was found that the applicability of existing passive microwave remote sensing-retrieved F/T products in large-scale areas (such as the Qinghai-Tibetan Plateau (QTP)) was influenced by some landscape factors, such as the arid climate type and terrain elevation gradient. FY-3 series satellites have accumulated nearly 10 years of passive microwave data, but there is little work based on FY-3 passive microwave data to see its potential in land surface F/T status monitoring. In this work, we proposed a dynamic method to determine the surface F/T status by combining the edge detection method and discriminant function algorithm from FY-3B X-and Ka-band microwave radiation imager (MWRI) data. Comparing the results against three F/T products based on in situ 5 cm soil temperature, we demonstrate that this algorithm performs best over different validation areas with an overall accuracy of 86.5%. More specifically, the new algorithm improved the accuracy of current F/T products in arid and semiarid regions from 73% to 90%. Additionally, the spatial distribution of frozen days over the QTP of 2018 based on the new algorithm has good consistency with the permafrost map. However, the accuracy is influenced by snowmelt and appears to be overestimated for thaw soil during the day. This algorithm performs well in QTP areas with complex topography and climate types and holds the promise of providing users with highly accurate F/T products on larger and even global scales.

Effect of a non-uniform annular electron beam on the microwave characteristics in a coaxial structure Ka-band RKA output cavity

The influence of electron beam uniformity on the microwave characteristics of coaxial structure Ka-band RKA output cavity is investigated with particle-in-cell simulations. The electron beam non-uniformity is simulated in four different electron emission models: (1) continuous non-emission area, (2) spaced emission, (3) enhanced emission and (4) current density variation emission. The simulation results with the first emission model shows that the output power of Ka-band RKA decreases as the non-emission area increases, while the continuous non-emission area has little effect on the frequency and pulse width of Ka-band microwave; The simulation results with the second emission model shows that the output power of Ka-band RKA is related to the distribution of Z-component of electric field and excitation electric field strength in the beam–wave interaction gap. The more uniform the distribution of Z-component of electric field is, the greater the output power is. The stronger the excitation electric field is, the greater the output power is; The simulation results with the third emission model shows that the intense current density in local area will cause the reduction of output power. The higher the current density of the enhanced emission area is, the smaller the output power is; The simulation results with the fourth emission model shows that the fluctuation of current density during the steady-state phase will cause the fluctuation of microwave frequency and output power. The fluctuation amplitude of frequency and output power are positively related to the fluctuation amplitude of the current density. The larger the fluctuation amplitude of current density is, the greater the fluctuation amplitude of frequency and output power are. The faster the current density changes, the greater the fluctuation amplitude of frequency and output power are.

Satellite communication station for Ka and Q-bands

The article reveals the features of the organization of satellite communication systems in the remote and northern territories of Russia. The importance of providing broadband access to multimedia resources and the Internet is shown. The problems of development of an earth station of satellite communication Ka and Q-bands, providing broadband communication, are considered. Its architecture and operating principles are presented. To ensure the possibility of operation of the station in two frequency ranges, replaceable irradiation systems with a microwave path are used. The features of their manufacture are disclosed in detail. The results of experimental studies of irradiating systems with a microwave path are presented. The gain of the irradiating system with a microwave path of the Q-band in the composition with a parabolic mirror with a diameter of 1.2 m was 51.8 dB at the transmission frequencies, and 45 dB at the receiving frequencies. The gain of the irradiating system with the Ka-band microwave path was 47.8 dB at the transmission frequencies and 43.8 dB at the receiving frequencies. Thus, the use of the proposed earth station of satellite communication Ka and Q-bands will allow organizing satellite broadband communication in remote and northern territories of Russia.

L-Band Passive Microwave Data from SMOS for River Gauging Observations in Tropical Climates

The Global Flood Detection Systems (GFDS) currently operated at the European Commission’s Joint Research Centre (JRC) is a satellite-based observation system that provides daily stream flow measurements of global rivers. The system was initially established using NASA Advanced Microwave Scanning Radiometer—Earth Observing System (AMSR-E) Ka-band passive microwave satellite data. Since its initiation in 2006, the methodology and the GFDS database have been further adapted for data acquired by the Tropical Rainfall Measuring Mission (TRMM) GOES Precipitation Index (GPI), the AMSR2 sensor onboard the Global Change Observation Mission – Water satellite (GCOM-W1), and the Global Precipitation Measurement (GPM) GPM Microwave Imager (GMI) sensor. This paper extends the same flow monitoring methodology to low frequency (L-band) passive microwave observations obtained by the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) sensor that was launched in 2009. A primary focus is tropical climate regions with dense rainforest vegetation (the Amazon, the Orinoco, and the Congo basins) where high-frequency microwave observations from GFDS reveal a significant influence of vegetation cover and atmospheric humidity. In contrast, SMOS passive microwave signatures at the much lower L-band frequency exhibit deeper penetration through the dense vegetation and minimal atmospheric effects, enabling more robust river stage retrievals in these regions. The SMOS satellite river gauging observations are for 2010–2018 and are compared to single-sensor GFDS data over several river sites. To reduce noise, different filtering techniques were tested to select the one most suitable for analysis of the L-band time series information. In-situ water level (stage) measurements from the French Observation Service SO Hybam database were used for validation to further evaluate the performance of the SMOS data series. In addition to GFDS data, water stage information from Jason-2 and Jason-3 altimetry was compared to the microwave results. Correlation of SMOS gauging time series with in-situ stage data revealed a good agreement (r = 0.8–0.94) during the analyzed period of 2010–2018. Moderate correlation was found with both high frequency GFDS data series and altimetry data series. With lower vegetation attenuation, SMOS signatures exhibited a robust linear relationship with river stage without seasonal bias from the complex hysteresis effects that appeared in the Ka-band observations, apparently due to different attenuation impacts through dense forests at different seasonal vegetation stages.

Investigation of a cross-band relativistic Cherenkov oscillator based on the cathode adjustment

The mechanism and realization of a cross-band relativistic Cherenkov oscillator based on the cathode adjustment are presented. The device adopts coaxial dual-annular cathode to emit the inner and the outer electron beams, independently. When the inner annular cathode is extended and the outer annular cathode is retracted, the electron beams are emitted from the inner cathode and interact with the internal electromagnetic structure to generate Ka-band microwaves. On the contrary, the outer electron beams interact with the external electromagnetic structure to generate X-band microwaves. Thus, the cross-band microwave generation can be achieved only by adjusting the protrusion and retraction of dual-annular cathode. By the particle-in-cell (PIC) method, the physical process of beam-wave interaction in the device is studied, and the high efficiency internal-external double electromagnetic structures are designed. Simulation results show that the X-band microwave with a power of 1.50 GW and a frequency of 8.55 GHz is generated, corresponding to an efficiency of 32%. Meanwhile, the Ka-band microwave with power of 650 MW and frequency of 31.80 GHz is generated, corresponding to efficiency of 28%.

Enhanced Microwave Absorption Properties of Doped M-Type Barium Hexagonal Ferrites in Ka-band Frequencies

The present study reports the microwave absorption characteristics of La3+-Na+ substituted barium hexaferrites with chemical composition: Ba(1−2x)LaxNaxFe10CoTiO19 and Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 (0.00 ≤ x ≤ 0.25) respectively in Ka-band frequencies. The electromagnetic characteristics such as complex permittivity, complex permeability, and microwave absorption properties were studied using Vector Network Analyzer in 26.5–40.0 GHz frequency band. Dielectric properties showed almost constant variation with increase in frequency. Magnetic permeability spectra observed wavy variation with frequency. Comparing the electromagnetic properties of two series, it is observed that Co–Ti–Mn series observes higher values of electromagnetic properties in comparison to Co–Ti series. For composition x = 0.15 of Ba(1−2x)LaxNaxFe10Co0.5TiMn0.5O19 series, −55.33 dB reflection loss at 30 GHz frequency with −10 dB absorption bandwidth around 3.51 GHz has been observed. Thus, these materials can be employed as effective absorbers for Ka-band microwave absorbers.

К вопросу о физической природе рассеяния микроволнового излучения Ка-диапазона на взволнованной водной поверхности

К вопросу о физической природе рассеяния микроволнового излучения Ка-диапазона на взволнованной водной поверхности

Ka-band microwave photonic ultra-wideband imaging radar for capturing quantitative target information.

Extracting precise target characteristics from microwave image is needed and calls for high-resolution microwave imaging radar systems. In this paper, a Ka-band ultra-wideband microwave photonic (MWP) imaging radar is developed and experimentally demonstrated. In the transmitter, continuous ultra-wideband linear frequency modulation (LFM) wave is generated based on optical frequency sextupling technique. In the receiver, a combination of optical frequency mixer with fiber delay lines and electric analog-to-digital converter (ADC) is capable of receiving target echoes and imaging targets with different distances. The maximum instantaneous bandwidth of the transmitted waveform is measured to be 10.02 GHz and corresponding range resolution is calibrated to be 1.68 cm. Out-field tests with demonstrator working at synthetic aperture radar (SAR) or inverse synthetic aperture radar (ISAR) mode are carried out. Different targets such as an unmanned aerial vehicle (UAV), airliner and Leifeng pagoda are imaged. Based on corresponding high-resolution microwave images, quantitative information of the targets can be identified, which shows the great potential of the radar demonstrator for various remote sensing applications.

Large power microwave nonlinear effects on multifunction amplifier chip for Ka-band T/R module of phased array radar

Nonlinear effects of large power millimeter wave on critical chips for the T/R module of phased array radar is experimental studied and analyzed in this paper. A multifunction amplifier chip is selected for our experiments. A solid continuous wave (CW) source and a large power pulsed magnetron are both employed to generate the Ka-band microwave. The input-output characteristics, the degradation and destroy threshold of the chips are obtained through a series of experimental tests. At last, the results are given by figures and analyzed theoretically.