Abstract: In an exemplary embodiment, a multi-rate data conversion circuit receives digital data at varying data rates, receives a data rate input corresponding to the digital data and converts the digital data to a converted output based upon the data rate input. A direct digital synthesis circuit receives the converted output and synthesizes a modulated output signal based upon the converted output. A multi-rate converter receives the digital data, the data rate input and a clock signal and converts the digital data to converted digital data. A multi-rate digital data filter receives the converted digital data and produces a filtered digital output. An output scaler receives the filtered digital output and produces a scaled and filtered digital output. Finally, an adder combines the scaled and filtered digital output with a center frequency input and produces the converted output.

Abstract: A multi-rate data modulation circuit includes a multi-rate data conversion circuit and a modulator such as a direct digital synthesis circuit. The multi-rate data conversion circuit receives digital data at varying data rates, receives a data rate input corresponding to the digital data and converts the digital data to a converted output based upon the data rate input. The direct digital synthesis circuit receives the converted output and synthesizes a modulated output signal based upon the converted output. The multi-rate data conversion circuit may include a multi-rate converter, a multi-rate digital data filter, an output scaler and an adder. The multi-rate converter receives the digital data, the data rate input and a clock signal and converts the digital data to converted digital data. The multi-rate digital data filter receives the converted digital data and produces a filtered digital output. The output scaler receives the filtered digital output and produces a scaled and filtered digital output.

Abstract: Received signals preferably have a stable frequency spectrum over a frequency span derived from a resolution bandpass filter. Furthermore, the frequency span has a plurality of discrete frequency measurements across the frequency span. It is desired to determine which of the discrete frequencies correspond to peaks in the frequency spectrum. Each peak is integrated to initially determine which of the peaks are from narrowband continuous wave signals by comparing the aspect ratio of the peaks with the aspect ratio of a resolution bandpass filter. Those peaks which fail the aspect ratio test are discarded from the frequency spectrum. The remaining peaks are then fitted to a second order polynomial curve to finally determine whether they are due to narrowband continuous wave signals. The peaks which do not fit the curve are labeled as broadband.

Abstract: A test method and apparatus to aid a site operator in discriminating between signals measured at different times, as well as enabling a level of automation which is appropriate using state-of-the-art instrumentation for performing EMI measurements, such as open-site EMI measurements. Preferably, discrimination between the two signals is based on the two signals being separated by at least a frequency E defined as:E=2(frequency span/N)+K * RBWwhere:E=possible frequency error of a signal; frequency span=frequency range swept by a measuring receiver, for example, a spectrum analyzer;N=number of points measured;RBW=resolution bandwidth of a resolving bandpass filter of the measuring receiver; andK=constant less than or equal to one to account for unknown signal characteristics.With the specific application to open-site EMI measurements, preferably signals are allowed to be falsely detected as separate signals in order to take into account unknown signal characteristics, i.e., 1 RBW.fwdarw.K * RBW.