The present disclosure provides systems and methods for identifying and reporting failures of an analog to digital (A/D) conversion system. The systems and methods may detect and report a problem of input circuitry of an A/D converter and/or an A/D converter itself. For example, an identifiable characteristic can be introduced into the input signal provided to an A/D converter. The A/D converter may output a digital value that includes the identifiable characteristic of the A/D converter input. A monitoring system may determine and/or report a change in, or a failure of, the A/D converter or input circuitry thereto, based on the identification, non-existence of, or variation in the identifiable characteristic in the digital output.

A DAC design uses a passive reconstruction filter. The reconstruction filter includes a notch filter and series peaking filter (low pass filter with peaking in the signal passband). The notch filter provides notch filtering at the DAC clock frequency. The peaking filter increases signal bandwidth while attenuating frequency contents at harmonics of the DAC clock frequency. The notch filter can be an LC notch filter with at least one notch inductor Ln and at least one notch capacitor Cn. The peaking filter can be a series peaking inductor Ls (shunted with a filter capacitor Cp). In a differential configuration, the passive reconstruction filter can be configured with LC notch filters (with Ln notch inductors), and the peaking filter can be Ls peaking inductors coupled in series to the LC notch filters. The Ln notch inductors, Ls peaking inductors can be mutually wound as single inductors. For an example direct conversion RF transmit chain, IQ signal paths are implemented with differential DAC designs including passive reconstruction filters.

A D/A converter for converting a digital input data to an analog output signal, includes: a modulator configured to generate a first data by -modulating the digital input data; a digital filter configured to generate a second data by smoothing the first data; and a D/A converter configured to convert the second data to the analog output signal.