Low-Cost RFin–RFout Predistorter Linearizer for High-Power Amplifiers and Ultra-Wideband Signals

2018 ◽  
Vol 67 (9) ◽  
pp. 2069-2081 ◽  
Author(s):  
Karan Gumber ◽  
Meenakshi Rawat

The relevance of the problem follows from the consideration of the consequences of such serious road pavement defect as delamination. Also, the validity of the problem stems from the fact that the use of modern pulsed GPR provides low-cost monitoring of roads. This becomes possible when obtaining primary GPR data during the movement of the laboratory car with the speed of the transport stream, and, in addition, due to the exclusion of such labour-intensive operations as coring or cutting sections of pavement. The purpose of the work is to analyze various processing methods for ultra-wideband signals of pulsed GPR to study the capabilities of signal processing methods and algorithms to increase the reliability of detection of delamination. Materials and methods. During the investigation of the processing model and experimental data, first of all, modern theoretical methods of signal processing and computer modelling were used. Results. The factors determining the differences and characteristic features of pulsed signals of GPR, which can be used to detect delamination, as a violation of contact between layers, or to detect the presence of thin layers in a multilayer medium, are established and analyzed. Conclusions. The proposed approach to the formulation of the problem, together with the theoretical analysis and the results of numerical modelling, made it possible to justify the possibility of increasing the reliability of the non-destructive quality control of various structures and the effective detection of critical defects using GPR methods.


Algorithms ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 157
Author(s):  
Rahmat Ullah ◽  
Tughrul Arslan

Microwave imaging systems are currently being investigated for breast cancer, brain stroke and neurodegenerative disease detection due to their low cost, portable and wearable nature. At present, commonly used radar-based algorithms for microwave imaging are based on the delay and sum algorithm. These algorithms use ultra-wideband signals to reconstruct a 2D image of the targeted object or region. Delay multiply and sum is an extended version of the delay and sum algorithm. However, it is computationally expensive and time-consuming. In this paper, the delay multiply and sum algorithm is parallelised using a big data framework. The algorithm uses the Spark MapReduce programming model to improve its efficiency. The most computational part of the algorithm is pixel value calculation, where signals need to be multiplied in pairs and summed. The proposed algorithm broadcasts the input data and executes it in parallel in a distributed manner. The Spark-based parallel algorithm is compared with sequential and Python multiprocessing library implementation. The experimental results on both a standalone machine and a high-performance cluster show that Spark significantly accelerates the image reconstruction process without affecting its accuracy.


Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 780
Author(s):  
Kazunori Takahashi ◽  
Takashi Miwa

The paper discusses a way to configure a stepped-frequency continuous wave (SFCW) radar using a low-cost software-defined radio (SDR). The most of high-end SDRs offer multiple transmitter (TX) and receiver (RX) channels, one of which can be used as the reference channel for compensating the initial phases of TX and RX local oscillator (LO) signals. It is same as how commercial vector network analyzers (VNAs) compensate for the LO initial phase. These SDRs can thus acquire phase-coherent in-phase and quadrature (I/Q) data without additional components and an SFCW radar can be easily configured. On the other hand, low-cost SDRs typically have only one transmitter and receiver. Therefore, the LO initial phase has to be compensated and the phases of the received I/Q signals have to be retrieved, preferably without employing an additional receiver and components to retain the system low-cost and simple. The present paper illustrates that the difference between the phases of TX and RX LO signals varies when the LO frequency is changed because of the timing of the commencement of the mixing. The paper then proposes a technique to compensate for the LO initial phases using the internal RF loopback of the transceiver chip and to reconstruct a pulse, which requires two streaming: one for the device under test (DUT) channel and the other for the internal RF loopback channel. The effect of the LO initial phase and the proposed method for the compensation are demonstrated by experiments at a single frequency and sweeping frequency, respectively. The results show that the proposed method can compensate for the LO initial phases and ultra-wideband (UWB) pulses can be reconstructed correctly from the data sampled by a low-cost SDR.


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