Browsing by Subject "Sub-Nyquist sampling"

Now showing 1 - 8 of 8

Open Access
Compressive digital receiver: first results on sensitivity, dynamic range and instantaneous bandwidth measurements
(Institute of Electrical and Electronics Engineers Inc., 2019) Korucu, A. B.; Alp, Y. K.; Gök, G.; Arıkan, Orhan
In this work, sensitivity, one/two-signal dynamic range and instantaneous bandwidth measurement results of the recently developed Compressive Digital Receiver (CDR) hardware for Electronic Support Measures (ESM) applications, will be reported for the first time. Developed CDR is a compressive sensing based sub-Nyquist sampling receiver, which can monitor 2.25 GHz bandwidth instantaneously by using four ADCs (Analog-to-Digital Receiver) each of which has a sampling rate of 250 MHz. All the digital processing blocks of the CDR are implemented in Field Programmable Gate Array (FPGA) and they work in real time. It is observed that the sensitivity and dynamic range of the CDR changes with respect to input signal frequency. For 2.25 GHz bandwidth, the best and worst sensitivity values of the CDR are reported as -62 dBm and -41 dBm, respectively. One-signal dynamic range of CDR is measured as at least 60 dB for the whole band. The best and worst values of the two-signal dynamic rage values are observed as 42 dB and 20 dB, respectively.
Open Access
Degrees of freedom of optical systems and signals with applications to sampling and system simulation
(Optical Society of America, 2013) Oktem F.S.; Özaktaş, Haldun M.
We study the degrees of freedom of optical systems and signals based on space-frequency (phase space) analysis. At the heart of this study is the relationship of the linear canonical transform domains to the space-frequency plane. Based on this relationship, we discuss how to explicitly quantify the degrees of freedom of first-order optical systems with multiple apertures, and give conditions for lossless transfer. Moreover, we focus on the degrees of freedom of signals in relation to the space-frequency support and provide a sub-Nyquist sampling approach to represent signals with arbitrary space-frequency support. Implications for simulating optical systems are also discussed. © 2013 Optical Society of America.
Open Access
Linear canonical transforms, degrees of freedom, and sampling in optical signals and systems
(IEEE, 2014) Özaktaş, Haldun M.; Öktem, F. S.
We study the degrees of freedom of optical systems and signals based on space-frequency (phase-space) analysis. At the heart of this study is the relationship of the linear canonical transform domains to the space-frequency plane. Based on this relationship, we discuss how to explicitly quantify the degrees of freedom of first-order optical systems with multiple apertures, and give conditions for lossless transfer. Moreover, we focus on the degrees of freedom of signals in relation to the space-frequency support and provide a sub-Nyquist sampling approach to represent signals with arbitrary space-frequency support. Implications for simulating optical systems are also discussed.
Open Access
Online calibration of modulated wideband converter
(IEEE, 2016) Alp, Y. K.; Korucu, A. B.; Karabacak, A. T.; Gürbüz, A. C.; Arıkan, Orhan
In this work, we propose a new method for online calibration of recently proposed Modulated Wideband Converter (MWC), which digitizes wideband sparse signals below the Nyquist limit without loss of information by using compressive sensing techniques. Our method requires a single frequency synthesizer card, which can generate clean tones along the operation band of the system, rather than much expensive measurement instruments such as network analyser or vector spectrum analyser, which are not appropriate for online calibration. Moreover, low computational complexity of the proposed method enables its implementation on FPGA so that it can be embedded into the system. Hence, on each power on, the system can utilize self calibration without requiring any additional measurement instruments.
Open Access
Sıkıştırılmış algılama tabanlı sayısal almaç: ilk donanım uygulaması sonuçları
(IEEE, 2018-05) Korucu, A. B.; Çakar, O.; Alp, Y. K.; Gök, Gökhan; Arıkan, Orhan
In this work, first real hardware implementation results of CDR (Compressive Digital Receiver) are detailed. CDR is a digital receiver technology, which estimates frequency, amplitude, pulse-width etc. parameters of the incoming signal without ambiguity in frequency, by sampling the signal at rates far below the Nyquist limit based on compressive sensing theory. It is observed that the implemented hardware structure can resolve an instantaneous bandwidth of 2 GHz by using only two ADCs (Analog to Digital Converter) running at 200 MHz sampling frequency. It is argued that the CR system can be used as a digital receiver especially for Electronic Support Systems since it can monitor a wide spectrum by sampling at a very low rate.
Open Access
Sıkıştırılmış algılama tabanlı sayısal almaç: ilk performans ölçümleri
(IEEE, 2019-04) Korucu, Ali Buğra; Alp, Yaşar Kemal; Gök, Gökhan; Arıkan, Orhan; Çakar, O.; Eroğul, O.
Bu çalışmada, ilk defa bir donanım üzerinde gerçeklenen SATSAÇ (Sıkıştırılmış Algılama Tabanlı Sayısal Almaç) sisteminin performansını tanımlayan duyarlılık, anlık dinamik alan ve bant genişligine dair ölçüm sonuçları paylaşılacaktır. Geliştirilen SATSAÇ sistemi, her biri 250MHz ile örnekleme yapan 14 bit çözünürlükte dört adet ADC (Analog to Digital Converter) ile Nyquist limiti altında örnekleme yaparak en az 2.25GHz’lik bir bandı, sıkıştırılmış algılama teknikleri ile anlık olarak gözlemleyebilmektedir. Yapılan ölçümlerde, SATSAÇ sisteminin duyarlılık ve dinamik alan değerlerinin frekans bandına göre değişiklik gösterdiği gözlemlenmiştir. 2.25GHz’lik bant boyunca, en iyi duyarlılık seviyesi -62dBm, en kötü duyarlılık seviyesi -41dBm olarak ölçülmüştür. Tüm bant boyunca tek-sinyal dinamik alan en az 60dB olarak ölçülmüş olup, iki-sinyal dinamik alan en iyi 45dB, en kötü 20dB olarak gözlemlenmiştir.
Open Access
Sparse delay-Doppler image reconstruction under off-grid problem
(IEEE, 2014-06) Teke, Oğuzhan; Gürbüz, A. C.; Arıkan, Orhan
Pulse-Doppler radar has been successfully applied to surveillance and tracking of both moving and stationary targets. For efficient processing of radar returns, delay-Doppler plane is discretized and FFT techniques are employed to compute matched filter output on this discrete grid. However, for targets whose delay-Doppler values do not coincide with the computation grid, the detection performance degrades considerably. Especially for detecting strong and closely spaced targets this causes miss detections and false alarms. Although compressive sensing based techniques provide sparse and high resolution results at sub-Nyquist sampling rates, straightforward application of these techniques is significantly more sensitive to the off-grid problem. Here a novel and OMP based sparse reconstruction technique with parameter perturbation, named as PPOMP, is proposed for robust delay-Doppler radar processing even under the off-grid case. In the proposed technique, the selected dictionary parameters are perturbed towards directions to decrease the orthogonal residual norm. A new performance metric based on Kull-back-Leibler Divergence (KLD) is proposed to better characterize the error between actual and reconstructed parameter spaces. © 2014 IEEE.
Open Access
Sub-band equalization of modulated wideband converter for improved dynamic range performance
(IEEE, 2017) Korucu, A. B.; Alp, Y. K.; Gök, Gökhan; Arıkan, Orhan
In this work, we propose a new method to improve the dynamic range performance of the Modulated Wideband Converter (MWC), which is multi-channel sampling system for digitizing wideband sparse signals below the Nyquist limit without loss of information by using compressive sensing techniques. MWC achieves high dynamic range assuming that subband frequency responses of the system are identical. However, in hardware implementations of MWC, the resulting sub-band frequency responses are not identical and dynamic range performance of the system drops significantly which makes it unusable in practical applications. Proposed method iteratively designs FIR filters for equalizing frequency responses of the all sub-bands. Obtained results from the extensive computer simulations of the MWC system show that proposed method improves the dynamic range performance of the MWC system significantly.