Spurious free dynamic range

[Dr. Dhiman Kakati]

Hi all,
I am giving here a reference…..

In the year 1990, A. J. Cooper developed a four channel Cordless Telephony (CT2) fiber/radio system and demonstrated over single mode fiber using subcarrier multiplexing techniques. “A spurious free electrical dynamic range of 51 dB” was achieved which is sufficient for a mobile range of approximately 100m. The use of subcarrier multiplexing simplifies the design of the radio transceiver and allows complex processing equipment to be located at the local exchange. In this network a Centre Station (CS) is connected to numerous functionally simple Base Stations (BSs) via an optic fiber. The main function of BS is to convert optical signal to wireless one and vice versa. Almost all processing including modulation, demodulation, coding, routing is performed at the CS. That means, RoF networks use highly linear optic fiber links to distribute RF signals between the CS and BSs.

I am not getting the meaning of the text inside the quotes, please anyone explain.

Regards

[Dr. Dhiman Kakati]

I have found the following for this topic helpful,

“Spurious-Free Dynamic Range (SFDR) is the strength ratio of the fundamental signal to the strongest spurious signal (i.e. error or fake signal) in the output. It is also defined as a measure used to specify analog-to-digital and digital-to-analog converters (ADCs and DACs, respectively) and radio receivers.

SFDR is defined as the ratio of the RMS value of the carrier frequency (maximum signal component) at the input of the ADC or output of DAC to the RMS value of the next largest noise or harmonic distortion component (which is referred to as a “spurious” or a “spur”) at its output. SFDR is usually measured in dBc (i.e. with respect to the carrier frequency amplitude) or in dBFS (i.e. with respect to the ADC’s full-scale range). Depending on the test condition, SFDR is observed within a pre-defined frequency window or from DC up to Nyquist frequency of the converter (ADC or DAC).

In case of a radio receiver application, the definition is slightly different. The reference is the minimum detectable signal level at the input of a receiver, which can be calculated through a knowledge of the noise figure and the input signal bandwidth of the receiver or the system. The difference between this value and the input level which will produce distortion products equal to the minimum detectable signal referred to the input of the system is the SFDR of the system. However, this procedure is mainly reliable for ADCs. in RF systems where output spurious signals are nonlinear function of input power, more precise measurement is required to take into account this non-linearity in power.”

regards,
Dhiman

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