2023/1

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Generation of Slot Index Tables for Time-Hopping Pseudolites with the Constructed Congruence Codes
(Společnost pro radioelektronické inženýrství, 2023-04) Hu, Y.; Yu, B; Deng, Z; Yu, W
The time-hopping (TH) pulsed pseudolite (PL) can be used to enhance the performance of global navigation satellite systems (GNSS), and the slot index table (SIT) is an important part to form this PL signal. In this paper, a new method to generate SITs for multiple PLs is proposed. The general process of the proposed method is that first different time-hopping slot index (THSI) base matrices are generated based on the constructed congruence codes, and then by combining several different THSI base matrices to constitute a new matrix, the SIT for a PL is formed. Further by changing the combined matrices, different SITs for different PLs can be generated. During this process, two critical factors that affect the performance of the given method, i.e., the collision or hit property of the generated THSI base matrix and the correlation property of the formed SIT, are analyzed in detail. The simulations given at the end of this paper show that compared with many other similar schemes, the SITs given by the proposed method can obtain better correlation performance and detection performance in the receiver, and these results also imply that the proposed method offers a more effective way to design this kind of PL signal.
SAMPLE Dataset Objects Classification Using Deep Learning Algorithms
(Společnost pro radioelektronické inženýrství, 2023-04) Turcanik, M.; Perdoch, J.
The main topic of the article is automatic target classification of the synthetic aperture radar images based on the dataset composed of measured and synthetic data. The original contribution of the authors is their own topology of the convolutional neural network (CNN) with 1, 2, 3, and 4 tiers. The original convolutional neural network is used to classify radar images from the Synthetic And Measured Paired and Labeled Experiment (SAMPLE) dataset which consists of SAR imagery from publicly available datasets and well-matched synthetic data. The presented topologies of the CNN with 1, 2, 3, and 4 tiers were analyzed in 3 different scenarios: trained on the basis of real measured data and tested by synthetic data, trained on the basis of synthetic data, and tested by real measured data, and in the last case training and testing sets were formed by combining real measured and synthetic data. Based on the results of testing we could not use the proposed convolutional neural network trained with real measured data to classify synthetic radar images and vice versa (the 1st and the 2nd scenarios). The only last scenario with a combination of real measured and synthetic data in the training, validation, and testing data sets generates excellent results. The authors also present some confusion matrices, which can explain the reasons for the misclassification of radar images of military equipment. Comparing achieved results with another SAMPLE dataset classification results we can prove the usability of proposed and tested CNN structures for automatic target classification of the synthetic aperture radar images. The classification accuracy of the original convolutional network is 96.1%, which is better than the results of the other research so far.
Two-Dimensional Frequency Domain Second-Order Keystone Transform for Weak Target Integration Detection Based on Bistatic Radar Configuration
(Společnost pro radioelektronické inženýrství, 2023-04) Lei, Z.; Rao, X.; Jin, P.; Yi, H.; Hu, J.
In this paper, a novel coherent integration algorithm, i.e., two-dimensional frequency domain second-order keystone transform (FDSOKT), is proposed to detect a weak maneuvering target based on bistatic radar configuration. To eliminate range migration and Doppler frequency migration, the radar echoes are transformed into two-dimensional frequency domain firstly, and then a series of rescaling transforms, matched filter functions and compensation functions are performed respectively. With the elimination of the couplings between range frequency and azimuth frequency caused by radial velocity and acceleration, the energy of the echoes is focused in two-dimensional time domain, which improves the detection performance of weak target. In addition, to deal with Doppler ambiguity, different Doppler ambiguity cases are discussed and could be solved well. At last, some simulation experiments are provided and the effectiveness of FDSOKT is proved by the results.
A Low-Cost Dual-Band RF Power Amplifier for Wireless Communication Systems
(Společnost pro radioelektronické inženýrství, 2023-04) Luong, D. M.; Trinh, Q. K.; Nguyen, T. A.
This paper presents a design of a low-cost concurrent dual-band power amplifier operating at 1.8 GHz and 2.6 GHz. The design combines the signal splitting and second harmonic suppression techniques. The power amplifier aims at achieving the high-efficiency while rejecting unwanted output mixing products when operating in the dual-band mode. These advantages are obtained by using a harmonic termination technique combining with a signal splitting method. The designed amplifier is tested at both small- and large-signal performance through simulations and measurements. The designed amplifier delivers 10.2 dB Gain, 41.2 dBm Pout, and PAE of 40.2 % at 1.8 GHz and 10.1 dB Gain, 41.1 dBm Pout, and PAE of 38.7 % at 2.6 GHz. The second harmonic suppression for 1.8 GHz band is 49 dBc while the second harmonic for the 2.6 GHz is nearly total suppression. In addition, by using the proposed circuit, the unwanted mixing products can be significantly reduced improving linearity performance.
A Compact Band-Notched UWB MIMO Antenna with Enhanced Isolation Using Comb Shaped Decoupling Element
(Společnost pro radioelektronické inženýrství, 2023-04) Chatterjee, S.; Rana, S.; Sanyal, R.
A compact 37mm × 26 mm two element multiple-input-multiple-output (MIMO) antenna is presented for ultra wide band (UWB) system application with band notched characteristics. The proposed antenna comprises two semi trapezoidal shaped monopole radiating elements. The band rejection feature around 3.5 GHz has been achieved by incorporating the open ended quarter wavelength spiral shaped slot resonator on the patched surface. In order to realize the enhanced isolation, comb shaped symmetrical stub arrangement are embedded at the U shaped etched periphery to the stepped ground plane between the monopole radiators. This novel design approach leads towards isolation enhancement better than 20 dB throughout the UWB spectral range (3.1 -10.6 GHz) with peak isolation near about 46 dB. The Envelope Correlation Coefficient is significantly lower than 0.005 in entire operating range except the WiMAX rejection band.

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