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Analysis of Ionospheric Scintillations using Wideband GPS L1 C/A Signal Data
A non-real-time GPS receiver has been developed and
tested for use in scintillation analysis. The receiver consists
of a digital storage receiver and non-real-time software
acquisition and tracking algorithms. The goal of
this work is to shed light on the behavior of strongly
scintillating signals: signals which cause conventional
GPS receivers to lose carrier lock.
The receiver collects wideband GPS L1 digital data sampled at 5.7 MHz using an RF front-end and stores it
on disk for post-processing. It processes the data off-line
to determine carrier signal amplitude and phase variations
during scintillations. The main processing algorithms
are traditional code delay and carrier frequency
acquisition algorithms and special signal processing algorithms
that effectively function as a delay-locked loop
and phase-locked loop. The tracking algorithms use
non-causal smoothing techniques in order to optimally
reconstruct the phase and amplitude variations of a
scintillating signal. These techniques are robust against
the deep power fades and strong phase fluctuations
characteristic of scintillating signals.
To test the receiver, scintillation data were collected
in Cauchoeira Paulista, Brazil, from December 4 to 6,
2003. The data set spans several hours and includes
times when one or more satellite signals are scintillating.
The smoothing algorithm has been used to determine
the carrier amplitude and phase time histories
of the scintillating signals along with the distortion of
the pseudorandom noise (PRN) code’s autocorrelation
function. These quantities provide a characterization
of scintillation that can be used to study the physics of
scintillations or to provide off-line test cases to evaluate
a tracking algorithm’s ability to maintain signal lock
during scintillations.Aerospace Engineering and Engineering Mechanic
DSP Linearization for Millimeter-Wave All-Digital Receiver Array with Low-Resolution ADCs
Millimeter-wave (mmWave) communications and cell densification are the key
techniques for the future evolution of cellular systems beyond 5G. Although the
current mmWave radio designs are focused on hybrid digital and analog receiver
array architectures, the fully digital architecture is an appealing option due
to its flexibility and support for multi-user multiple-input multiple-output
(MIMO). In order to achieve reasonable power consumption and hardware cost, the
specifications of analog circuits are expected to be compromised, including the
resolution of analog-to-digital converter (ADC) and the linearity of
radio-frequency (RF) front end. Although the state-of-the-art studies focus on
the ADC, the nonlinearity can also lead to severe system performance
degradation when strong input signals introduce inter-modulation distortion
(IMD). The impact of RF nonlinearity becomes more severe with densely deployed
mmWave cells since signal sources closer to the receiver array are more likely
to occur. In this work, we design and analyze the digital IMD compensation
algorithm, and study the relaxation of the required linearity in the RF-chain.
We propose novel algorithms that jointly process digitized samples to recover
amplifier saturation, and relies on beam space operation which reduces the
computational complexity as compared to per-antenna IMD compensation.Comment: 2019 IEEE 20th International Workshop on Signal Processing Advances
in Wireless Communications (SPAWC
Testing high resolution SD ADC’s by using the noise transfer function
A new solution to improve the testability of high resolution SD Analogue to Digital Converters (SD ADC’s) using the quantizer input as test node is described. The theoretical basis for the technique is discussed and results from high level simulations for a 16 bit, 4th order, audio ADC are presented. The analysis demonstrates the potential to reduce the computational effort associated with test response analysis versus conventional techniques
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