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Solving real-world challenges (Case Studies)

Linear Vector Signal Generator for X-band Communication


This paper presents a scheme of extending the operating frequency range of an existing vector signal generator with the help of frequency-doubler. Since the frequency doubler generates the second harmonic of the input signal, which is non-linear, its compensation is essential for a linear transmitter output. A neural network-based digital predistorter is presented to linearize the frequency doubler. For proof of concept, the X-band frequency has been selected in which an input frequency of 5.5 GHz is shifted to 11 GHz. The results are validated using the experimental setup with 5 MHz Long-Term Evolution signal and the corrected EVM is found to be 2.031%.

SDR Solution for Enhanced Quality Wider Bandwidth Communication


The chip-based implementation of transceivers paved the way for tremendous growth in software-defined radios (SDRs). Although software programming makes things reconfigurable, the limitation of hardware components cannot be avoided. These limitations translate to the problem of DC offset, local oscillator (LO) leakage and in-phase/quadrature-phase imbalance along with bandwidth limitation. This paper presents a digital intermediate-frequency-based method to expand the bandwidth of the multichannel SDR transmitter using a single LO configuration while avoiding RF imperfections. The proposed method is experimentally validated.

Characterization of Hardware Impairments in Software Defined Radio


The advancement in computing and silicon technologies has paved the way for modern software-defined radios (SDRs). However, due to the availability of several commercial SDR, it is difficult to choose the desired SDR platform with optimum configuration and characteristics. This paper presents the characterization of SDRs to find out the digital and analog impairments and test the limits of SDR. For validation and measurement, analog device AD9361 RF chip and Zed Board Xilinx Zynq-7000 all programmable system on a chip is used. We have also implemented Long-Term Evolution (LTE) on the testbed to validate the performance.

A Low-Cost Test Bench for the Characterization of Microwave Devices Using Modulated Envelope Signal


Thirst for efficient design and modeling of nonlinear microwave devices require accurate characterization of devices in the presence of modulated signals. Vector network analyzer, which is used for such characterization is a costly tool. This paper presents a low-cost test bed, which can characterize the microwave devices in the presence of wideband 4G/5G signals for the measurement of harmonics as well as in-band characteristics. Example case for the second harmonic along with the fundamental signal characterization has been reported.