Frequency Scaling Algorithm Research Articles

Some Aspects of Improving the Frequency Scaling Algorithm for Dechirped SAR Data Processing

The frequency scaling algorithm (FSA) was proposed to process the synthetic aperture radar (SAR) data acquired via the dechirp-on-receive approach. Some aspects of improving the FSA are investigated in this paper, based on which an extended FSA (EFSA) is presented. The general purpose of the EFSA is to reduce the effect of range spectrum shift of the intermediate processing results, which occurs during the scaling operation in the FSA, so as to achieve a more effective utilization of the processed bandwidth. The EFSA is implemented through time shifting the scaling and the inverse scaling functions used in the FSA and also the adjustment of the scaling factor. The derivation of the EFSA is detailed in this paper. Point target simulation in squinted imaging geometry indicates that the presented algorithm is more suitable for large-squint applications.

Nonlinear Frequency Scaling Algorithm for High Squint Spotlight SAR Data Processing

This paper presents a new approach for the squint-mode spotlight SAR imaging. Like the frequency scaling algorithm, this method starts with the received signal dechirped in range. According to the geometry for the squint mode, the reference range of the dechirping function is defined as the range between the scene center and the synthetic aperture center. In our work, the residual video phase is compensated firstly to facilitate the following processing. Then the range-cell migration with a high-order range-azimuth coupling form is processed by a nonlinear frequency scaling operation, which is different from the original frequency scaling one. Due to these improvements, the algorithm can be used to process high squint SAR data with a wide swath and a high resolution. In addition, some simulation results are given at the end of this paper to demonstrate the validity of the proposed method.

Bistatic Spotlight SAR Processing Using the Frequency-Scaling Algorithm

This letter derives the bistatic point target spectrum for the translational invariant case. Based on the derived spectrum and the linear approximation of the bistatic range cell migration factor, a bistatic frequency-scaling algorithm (FSA) is proposed for spotlight synthetic aperture radar data processing. This algorithm leads to a very precise and efficient processing since it performs the focusing in the frequency domain and no interpolation is required in the whole processing chain. In addition, it is shown that the case considered in the monostatic FSA is a specialization of the more general one considered in this letter. Finally, simulation results are provided to illustrate the validity of the presented approach.

Modified Frequency Scaling Algorithm for FMCW SAR Data Processing

This paper presents a modified frequency scaling algorithm for frequency modulated continuous wave synthetic aperture radar (FMCW SAR) data processing. The relative motion between radar and target in FMCW SAR during reception and between transmission and reception will introduce serious dilation in the received signal. The dilation can cause serious distortions in the reconstructed images using conventional signal processing methods. The received signal is derived and the received signal in range-Doppler domain is given. The relation between the phase resulting from antenna motion and the azimuth frequency is analyzed. The modified frequency scaling algorithm is proposed to process the received signal with serious dilation. The algorithm can effectively eliminate the impact of the dilation. The algorithm performances are shown by the simulation results.

A Chirp Transform Algorithm for Processing Squint Mode FMCW SAR Data

Frequency-modulated continuous-wave (FMCW) synthetic aperture radar (SAR) is a lightweight cost-effective high-resolution airborne imaging radar. In squint case, the frequency scaling algorithm, which is suitable for processing nonchirped raw data, cannot be used directly in FMCW SAR data processing because of low system sampling frequency. On the other hand, the continuous antenna motion of FMCW SAR can cause serious distortions in the reconstructed images. In this letter, an improved algorithm called the chirp transform algorithm is proposed. When the effects of the residual video phase are negligible, the algorithm uses a chirp transform to perform the time scaling operation to alleviate the sampling frequency problem. It requires only fast Fourier transforms and multiplications. The range cell migration introduced by the continuous motion is also compensated completely in range-Doppler domain. The algorithm performances are analyzed and are supported by point target simulation experiments.

Improving fairness, throughput and energy-efficiency on a chip multiprocessor through DVFS

Recently, a single chip multiprocessor (CMP) is becoming an attractive architecture for improving throughput of program execution. In CMPs, multiple processor cores share several hardware resources such as cache memory and memory bus. Therefore, the resource contention significantly degrades performance of each thread and also loses fairness between threads. In this paper, we propose a Dynamic Frequency and Voltage Scaling (DVFS) algorithm for improving total instruction throughput, fairness, and energy efficiency of CMPs. The proposed technique periodically observes the utilization ratio of shared resources and controls the frequency and the voltage of each processor core individually to balance the ratio between threads. We evaluate our technique and the evaluation results show that fairness between threads are greatly improved by the technique. Moreover, the total instruction throughput increases in many cases while reducing energy consumption.

Improved nonlinear frequency scaling algorithm for squint FMCW SAR

An improved nonlinear frequency scaling algorithm is proposed to process squint frequency modulated continuous wave synthetic aperture radar data. The algorithm uses a decimation technique to decrease the bandwidth of the signal introduced by the frequency scaling operation, effectively removing the range frequency aliasing. Simulated results show the validity of the algorithm.

An analytical model for predicting the remaining battery capacity of lithium-ion batteries

Predicting the residual energy of the battery source that powers a portable electronic device is imperative in designing and applying an effective dynamic power management policy for the device. This paper starts up by showing that a 30% error in predicting the battery capacity of a lithium-ion battery can result in up to 20% performance degradation for a dynamic voltage and frequency scaling algorithm. Next, this paper presents a closed form analytical expression for predicting the remaining capacity of a lithium-ion battery. The proposed high-level model, which relies on online current and voltage measurements, correctly accounts for the temperature and cycle aging effects. The accuracy of the high-level model is validated by comparing it with DUALFOIL simulation results, demonstrating a maximum of 5% error between simulated and predicted data.

The Frequency Scaling Algorithm and interferometric Spotlight SAR processing

Synthetic Aperture Radar (SAR) is a well-established technique for air- and spaceborne high resolution imaging. This paper demonstrates the phase preservation of the new Frequency Scaling Algorithm for Spotlight SAR data processing and investigates differences between Stripmap and Spotlight illumination. The algorithm performs the range cell migration correction for non-chirped raw data without interpolation by using a novel frequency scaling operation. The azimuth processing is based on a spectral analysis approach that is made highly accurate by azimuth scaling. In almost all processing stages, a subaperture approach is introduced for efficient azimuth processing. The maximum scene size for air- and spaceborne spotlight parameter examples is estimated. A method is proposed, which shows how to process Stripmap mode raw data in the Spotlight mode. Point target simulations and real raw data processing, including the generation of Spotlight interferograms prove the phase preservation of the Frequency Scaling Algorithm. The same SAR Stripmap raw data set of DLR's airborne system is processed in Stripmap and in Spotlight mode and the resulting detected images and interferograms are compared to each other. The differences due to the different range of squint angles used for the azimuth focusing are discussed.

Spotlight SAR data processing using the frequency scaling algorithm

This paper presents a new processing algorithm for spotlight SAR data processing. The algorithm performs the range cell migration correction for non-chirped raw data without interpolation by using a novel frequency scaling operation. The azimuth processing is based on a spectral analysis approach which is made highly accurate by azimuth scaling. In almost all processing stages, a subaperture approach is introduced for efficient azimuth processing. In this paper, the complete derivation of the algorithm is presented. A very useful formulation for non-chirped SAR signals in the range Doppler domain is also proposed where the residual video phase is expressed by a chirp convolution. The algorithm performance is shown by several simulations. A spotlight image, which has been extracted from stripmap raw data of the experimental SAR system of DLR, shows the validity of the frequency scaling algorithm.