Recent Submissions

Now showing 1 - 5 of 10
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    Low Voltage High Performance CMOS Current Mode Four-Quadrant Analog Multiplier Circuit
    (Společnost pro radioelektronické inženýrství, 2022-05) Ettaghzouti, Thouraya; Khlaifia, Dalila; Zitouni, Naoufel; Hassen, Nejib
    This paper describes a new CMOS current mode four-quadrant analog multiplier circuit. The proposed design is based on a high performance squarer cell, whose main core is realized by the up–down topology trans-linear loop using flipped voltage followers (FVF). The simulation results are verified by TSPICE simulator based on the BSIM3v3 transistor model for TSMC 0.18 µm CMOS process available from level 49 MOSIS at 25◦C with ± 0.75 V supply voltage. The proposed multiplier offers improved characteristics compared to the multipliers previously exposed in the literature. It has a wide dynamic range. The total harmonic distortion is about 0.42% at 1 kHz with peak-to-peak input current of 40 µA. The −3 dB bandwidth is more than 850 MHz and a maximum power consumption is of approximately 105 µW.
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    A Simple Approach for Improving Bandwidth and Isolation of Wilkinson Power Divider
    (Společnost pro radioelektronické inženýrství, 2022-05) Nguyen Minh Giang; Luong Duy Manh
    A simple approach to improve both the bandwidth and isolation of the Wilkinson power divider for using in L-band satellite communications is presented in this paper. To enhance the bandwidth, a multi-section method based on the Chebychev impedance transformation is employed. In order to improve the isolation performance between output ports, the values of isolation resistors are carefully determined by using the iterative approximation method combined with an investigation procedure. In order to validate the proposed design, a two-way and eight-way power divider prototypes were fabricated and tested on a Rogers RO4003C material. Good agreements between simulations and measurements are obtained in a frequency range from 0.8 GHz to 2.2 GHz. The two-way power divider had a fractional bandwidth of 106% with an isolation of better than 30 dB. The eight-way power divider achieved the bandwidth and isolation of 109% and better than 24 dB, respectively. Both the power dividers exhibit the phase imbalance of less than 3 degrees, and amplitude imbalance of less than 0.02 dB. Compared with the other works, the proposed power dividers deliver broader bandwidth and improved isolation while still retaining good insertion loss, low phase and amplitude imbalance in the operation frequency range.
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    On Theoretical Accuracy of Meteorological Targets Measurement by Radar
    (Společnost pro radioelektronické inženýrství, 2022-05) Fiser, Ondrej; Kovalchuk, Maria
    We draw your attention to the fact that meteorological radar does not actually measure a commonly used quantity “radar reflectivity factor,” (which is not dependent on frequency) but a different quantity called “radar reflectivity.” We present the usual recalculation which is based on frequency dependency used by Rayleigh approximation of radar cross-sections (back scattering cross section of rain, cloud, fog drop). But this approximation is valid in Rayleigh region only. We concluded that for admitting error lower than 2 dB in the radar reflectivity factor determination we can use the “effective radar reflectivity factor” for frequencies up to 19 GHz only. Otherwise the error will increase. As we use (and present in this article) the Mie algorithm we can replace the Rayleigh frequency dependence estimation by more accurate radar reflectivity factor determination using the Mie scattering. The correction is presented in the form of “Correction function C” dependent on frequency and rain rate in the graphical form and polynomial approximation. Beside this we present the simplification of back scattering cross sections for Rayleigh and Optical regions and the borders values of size parameter for these regions. We added the meteorological radar equation derivation. This should support the radar measurement understanding.
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    Design of h¯-CPM-LFM Radar-Communication Integration Signal
    (Společnost pro radioelektronické inženýrství, 2022-05) Ye, Mingkun; Tang, Jun; Zhao, Yang; Su, Rongqing
    In light of the increasing requirement for the electromagnetic spectrum, the integration of radar and communication is widely concerned because of its equipment miniaturizing and high efficiency of spectrum. To address the issue that the communication information in integrated signals for radar and communication affects detection performance, A novel integrated signal is proposed in this paper. Inspired by the high communication efficiency of shaped octal phase-shift keying (S8PSK) and high spectral efficiency of the three-section integrated waveform k-LFM-CPM, we generate a new type of modulation ℎ¯-CPM by the introduction of a precoding method with low complexity and a time-varying modulation index h, h-CPM is used to encode communication data into LFM radar waveform to form a novel radar and communication integration waveform ℎ¯-CPM-LFM. Numerical results show that the designed waveform is at least 10 dB less spectrum extension than other integration waveforms when carrying large amounts of communication information and has excellent BER performance under the condition of strong out-of-band interference. Ambiguity function analysis shows that the waveform has excellent detection performance comparable to LFM.
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    Electromagnetic Energy Coupling Path and Protection Method of UAV Datalink against Broad-Spectrum High-Power Microwave Radiation
    (Společnost pro radioelektronické inženýrství, 2022-05) Wang, Yuming; Ma, Liyun; Chen, Yazhou
    To verify the adaptability of unmanned aerial vehicle (UAV) datalinks to the electromagnetic environment comprising broad-spectrum high-power microwave radiation, strong electromagnetic pulse (EMP) tests were conducted using ultra wideband (UWB) radiation source at different radiation field strengths and repetition frequencies. For UAV datalinks, interference, disturbance, degradation and other effects were found in the tests. The electromagnetic energy coupling path of the broad-spectrum high-power microwave radiation was determined by adjusting the test status of UAV datalink as well as by protecting its key parts. The radio frequency front end, power cable and terminal interfaces on the housing surface were found to be weak electromagnetic links. The methods of the protection of radio frequency front end and power cable against strong EMPs were proposed. In addition, protection effects obtained by using different protection modules of radio frequency front end as well as by applying power spike pulse suppressors were compared and validated.