Abstract: Compact ground-plane antennas having a plurality of sub-elements disposed in a radially symmetric pattern above a ground-plane. Each sub-element is similarly shaped and has a total lenght of approximately one-quarter wavelength at the corresponding operating frequency. The present antennas exhibit a significant reduction in size and improved current sharing to permit better control of the antenna characteristics; in particular the antenna patterns and drive point impedance.

Abstract: An analog to digital converter converts an analog input signal to at least two digital output signals as follows. An analog feedback signal is subtracted from the analog input signal to produce a difference signal. The difference signal, then, is integrated to produce an integrated signal which is quantized to produce the digital output signals in response to respective control signals each having a predetermined frequency and being offset in phase from each other. Finally, the digital output signals are converted into the analog feedback signal. Such analog to digital converter uses components operating at a lower frequency than the sampling frequency fs without loss of dynamic range.