Abstract: An N-element noise model of a receiver is created, with the number of noise elements (N) determined by the equation N=(number of variable gain components+1). The components in the model are grouped into domains with each noise element associated with a domain. The domains are defined so that the noise contributions of the components within each domain are independent of the receiver gain state. A noise value is computed for each noise element. Each noise value is determined with reference to a particular point in the model, and is computed in a reference state. Input-referred noise values are calculated using each noise value and the current gain state data for the receiver. A composite input-referred noise value is computed using the input-referred noise values and subtracted from a measurement signal to reduce noise in the signal. The composite noise value can automatically be re-calculated for any receiver gain state.

Abstract: A method of using a vector network analyzer (VNA) for coordinated Voltage Standing-Wave Ratio (VSWR) and Time Domain Reflectometry (TDR) measurement includes configuring the VNA for identifying discontinuities correlated to a VSWR lobe. In some embodiments, the method includes identifying a largest VSWR lobe in a frequency band of interest, using phase data associated with an S11 scattering parameter to find the correct electrical delay required to align Low Pass Step Transform data, and configuring the Low Pass Step Transform span and center time to align coherent inductive and capacitive discontinuities relative to grid lines of a TDR display. In some embodiments, the method is automated.

Abstract: A high speed, synchronous, programmable frequency divider is disclosed. The divider is composed of a cascade of conventional programmable counters, each of which receives some portion of an externally supplied integer N, such that the divider produces one output pulse for every N periods of a supplied clock signal. Although conventional frequency dividers are substantially slower than the speed of their individual counters, a divider according to this invention, however, will operate at very nearly the same speed. The improved performance is achieved through (a) individually choosing the timing of the clock signal applied to each circuit of the divider, and (b) introducing a delay circuit, typically a shift register, in a feedback path. A method for determining the values of the clock timing variations and for determining an optimum number of flip-flops in the shift register is given. A divider according to the invention may be optimized either for maximum speed or for best design margins at a given speed.

Abstract: A spectrum analyzer for measuring the frequency spectrum of a pulsed input signal includes a synthesized local oscillator for providing an oscillator signal. The local oscillator is responsive to a digital control input signal to sweep the frequency of the oscillator signal from a start frequency to a stop frequency wherein the values of the start and stop frequencies are determined by the control signal. The oscillator is further responsive to the control signal to stop sweeping the oscillator signal. The oscillator signal is mixed with the pulsed input signal and filtered to determine the peak voltage of a predetermined frequency component of the mixed input signal. A data processor is provided for providing the control signal to the local oscillator. The data processor is adapted to adjust the control signal so that the start frequency of the oscillator is equal to its previous stop frequency minus a predetermined frequency difference.

Abstract: Time/frequency skew between a plurality of simultaneously operated swept instruments is minimized by sharing a common master clock signal among the instruments and resetting the phases of internal clocking signals in each instrument to known states. Once reset, the clocking signals in each of the instruments operate in tandem. Consequently, the triggering latency period among all the instruments is uniform and subsequent triggered sweeps begin at substantially the same instant, providing accurate sweep tracking among a plurality of instruments.