Digital radio frequency receiver
Frequency-multiplexed cellular telephone cell site base station and method of operating the same
Receiver for a digital radio signal Patent #: 5493721
ApplicationNo. 534773 filed on 09/27/1995
US Classes:370/484, Digital analysis or synthesis of a group329/341, Input signal converted to and processed in pulse form (e.g., pulse counter or digital type demodulator)370/497, Using particular filtering technique455/266Selectivity or bandwidth control
ExaminersPrimary: Olms, Douglas W.
Assistant: Phillips, Charles E.
International ClassH04J 001/05
AbstractDisclosed is an apparatus for digitizing an electromagnetic input signal having frequency components within at least first and second segregated frequency bands, particularly useful in a wireless communications system. The apparatus includes a filtering circuit arrangement for passing only frequency components of the input signal substantially within the first and second frequency bands, to provide a filtered signal having a spectrum with spectral components below a predetermined power level within a frequency gap between the first and second frequency bands. An analog to digital (A/D) converter samples the filtered signal at a sampling rate sufficient to provide a digitized output signal with a frequency spectrum corresponding to that of the filtered signal and also with a replica of spectral components of one of the frequency bands appearing within the frequency gap. Preferably, the sampling rate used is less than the Nyquist sampling rate for the composite frequency band extending from the lowest to highest frequencies of the two bands. This allows a single A/D converter to be employed to sample the filtered signal, even when a large frequency gap exists between the segregated bands. A single mixer stage can then be used in conjunction with the single A/D converter in a wireless communications receiver application.
Field of SearchInput signal converted to and processed in pulse form (e.g., pulse counter or digital type demodulator)
Including discrete semiconductor device
Including digital logic circuitry
Input signal split into plural signals
Including three or more terminal discrete semiconductor device
APPARATUS CONVERTIBLE TO ANALOG
Selectivity or bandwidth control
Band pass filter
With frequency conversion