Analysis of the zero-crossing times of angle-modulated signals provides a computationally efficient means of implementing a number of processing functions, including demodulation and spectral estimation. Unfortunately, sampling of a bandlimited signal is typically accomplished using uniformly spaced amplitude samples rather than detecting the zero-crossing times. This paper investigates the use of linear interpolation to estimate zero-crossing times from the uniformly-sampled data. The statistical properties of the error due to interpolation, additive Gaussian noise and'quantization are each considered separately as a function of the sampling interval.
A digital radio frequency memory (DRFM) is an electronic countermeasures device that samples and quantizes (analog to digital couversion) an incoming radar signal and produces (digital to analog conversion) a jamming signal from the sampled radar signal. An equation for the frequency spectrum of a signal produced by a DRFM is derived in this paper. The derivation of the equation assumcs the incoming radar signal has a finite duration and a single frequency, the ratio of the radar frequency, after heterodyning to baseband, to the sampling frequency is rational, and the components used in the DRFM are ideal.The quantization of the sampled values causes harmonics in the DRFM signal. The magnitude of the harmonics is a major concerii to the designers of DRFM systems, and an equation for predicting tlie magnituil(: of the harmonics is necessary for performance analysis. This equatioli provides an easy and fast method for determining how the magnilude of the harmonics is affected by the number of quantization levels (bit.s) i i i the analog to digital converter. radar signal is assumed to have a frequency in the center of the input bandwidth and a hand\vicltli much less than the input bandwidth Fiture 2 is a pictorial represi~iitation of tlie spectrum at the input of tlic. analog to digit.al converter v Y FILTER CO\ EKTER AND HOLD FILTER LOCAL OSCILLATOR
In this paper, we present a short tutorial description of noise figures for two-port linear transducers and entire receiver systems. Due to the long history of the use of noise figures to specify noise performance, numerous definitions have evolved. The relationships between the various noise figure definitions found in the literature are specified in this paper and tables are provided as a cross reference to the notation and naming conventions used in the references.
The purpose of this study is to verify that a digital single sideband modulator can he incorporated into a Digital Radio Frequency Memory (DRFM). The single sideband modulator is designed to use digital multiplying integrated circuits to produce the frequency shift rather than analog mixers. The circuit also employs a digital Hilbert transform filter to shift the phase of the incoming signal by 90 degrees. The circuit was tested with simulated S-band radar signals ranging from 3.012 to 3.038 GHz. The circuit, running in double sideband mode, proved its ability to shift the frequencies of the radar signals by frequencies in the range of-25 to +25 kHz. All the spurious outputs of the system were found to be more than 28 dB below the carrier.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.