A digital noise generator, wherein pseudo-random rapidly changing analog input voltages to a voltage controlled oscillator are used to generate corresponding rapidly changing discrete frequency outputs, is disclosed. Means are provided to delay the oscillator output by an amount at least equal to the rise time between each frequency change. The delayed and non-delayed oscillator outputs are electrically coupled through a switch that operates at times and at a rate to eliminate the rise time between frequency changes and thus improve the frequency spectrum.
A pseudorandom noise generator which operates in different modes is disclosed. The pseudorandom noise generator (10) includes circuitry (11,13) for providing a digital signal having a pseudorandom sequence at a selected clock rate; a modulation control circuit (15, 17, 20, 23) for selectively providing a modulation control signal that corresponds to either a non-filtered or filtered version of the digital signal, and for controlling the mode of operation of the noise generator; a modulation circuit (27, 29, 31, 33) responsive to the modulation control signal for providing a modulation signal; and a voltage controlled oscillator (VCO) (35) responsive to the modulation signal for providing a VCO output having a relatively constant output spectrum and high spectral containment for each mode of operation pursuant to control by the modulation control circuit and the modulation circuit.
Apparatus and a method are disclosed for synthesizing a pseudorandom communications signal having a smooth, flat, power spectrum. The system comprises frequency modulation circuitry for deriving a first analog signal from a digital encoding signal. The first analog signal is derived to have a substantially constant amplitude and a frequency varying in response to the amplitude of the digital encoding signal. Fourier transform circuitry is connected to the modulation circuitry and is operative to derive a second analog signal from the first analog signal. The resulting second analog signal is the fourier transform of the first analog signal, having a substantially constant power spectral density over the bandwidth of said second analog signal, and having an amplitude that varies in response to the amplitude of the digital encoding signal.
An apparatus for breaking the periodicity of the pseudorandom bit stream output from a linear sequence generator. The apparatus includes a ring oscillator which periodically corrupts the sequence of the generator. The level of the supply voltage applied to the logic elements of the ring oscillator is varied over time, thereby altering the oscillator output frequency. In a second embodiment, the temperature of the logic elements of the ring oscillator is varied over time, thereby also altering the oscillator output frequency. A system comprising four of the above-disclosed apparatus having different linear sequences and different corrupting influences, are multiplexed, wherein the multiplexing selection criterion is determined by a logical combination of the four linear sequences.
GBit/s transceiver with built-in self test features. A method is disclosed for testing the operation of a transceiver having a digital processing section and an analog section, each having a transmit portion and a receive portion, the analog portions adaptable to interface with an analog network. The transceiver is first configured to operate in a test mode. In the test mode, the transmit portion of the digital processing section is activated to generate data to be transmitted by the transmit portion of the analog section. The receive portion of the analog section and the receive portion of the digital processing section are operated to receive data. Thereafter, the parametrics of select portions of the receive portion of the digital processing section are examined during the receipt of data by the receive portion of the analog section and processing thereof by the receive portion of the digital processing section.
