Abstract: An apparatus and method for measuring the properties of a DUT characterized by a signal gain applied to an input signal to that DUT and a DUT noise spectrum introduced by that DUT is disclosed. An apparatus includes first and second measurement channels and a controller. The first and second measurement channels are characterized by gains and noise spectrums that are different for the different channels and generate first and second measurement signals. The controller measures an average value of a product of the first and second measurement signals when an input signal is applied to the input of the DUT, the controller providing a measure of the signal to noise ratio of the output of the DUT, independent of the noise spectrums in the first and second measurement channels. Four channel embodiments reduce the amount of calibration needed to measure the gain and noise spectrum of the DUT.

Abstract: One or more of the programmable RF receivers or other devices in the network may be programmed to determine whether one or more defining characteristics associated with a particular RF transmitter or transmitter type are present in RF data. The one or more defining characteristics are used to detect the use of an RF transmitter or transmitter type.

Abstract: An apparatus and method for measuring the properties of a DUT characterized by a signal gain applied to an input signal to that DUT and a DUT noise spectrum introduced by that DUT is disclosed. An apparatus includes first and second measurement channels and a controller. The first and second measurement channels are characterized by gains and noise spectrums that are different for the different channels and generate first and second measurement signals. The controller measures an average value of a product of the first and second measurement signals when an input signal is applied to the input of the DUT, the controller providing a measure of the signal to noise ratio of the output of the DUT, independent of the noise spectrums in the first and second measurement channels. Four channel embodiments reduce the amount of calibration needed to measure the gain and noise spectrum of the DUT.

Abstract: A system and method are provided which coordinate the actions of a plurality of devices via scheduling occurrence of the actions based on synchronized local clocks of the devices. Thus, a plurality of devices are communicatively coupled via a communication network, and the devices have their local clocks synchronized to a high degree of precision, using IEEE 1588, NTP, or some other technique for synchronizing their local clocks. “Time bombs” can be scheduled on the devices to coordinate the occurrence of actions between the devices in accordance with the detonation times set for the respective time bombs. In certain embodiments, not only the detonation time, but also the respective action to be triggered upon detonation is programmable for each device. The time bombs implemented on the various devices can be used to coordinate the operations of the various devices with a high degree of temporal precision.

Abstract: A number of RF receivers are connected in a network. The network is used to transmit communications, data, or both to and from the RF receivers and to synchronize the RF receivers to a common time. Digitized RF data is time-stamped and stored in memory. A trigger circuit in one or more RF receivers determines whether a trigger criterion or criteria has been met. When a trigger criterion or criteria has been met, some or all of the RF receivers in the network transmit select digitized RF data to a central processing device. The central processing device processes the select digitized data to detect if a signal is present.

Abstract: Two or more receivers in a plurality of receivers are selected and the signal data from each receiver obtained. A cross-correlation of signal data is computed for each receiver paring in the selected receivers. The results of each cross-correlation are then combined and mapped into a graphical indicator function. The graphical indicator function generates a visual representation of location information using the results of each cross-correlation computation. The visual representation is then displayed to a user. Additional location information may also be simultaneously displayed with the visual representation or upon command.

Abstract: A network of RF devices is connected to a central processing device and a common network clock. The central processing device and the RF devices exchange timing information in order to synchronize the network of RF devices to a common time defined by the common network clock.

Abstract: A correction processor connected to an oscillator uses precision timing signals propagated over a digital network to generate an error signal. IEEE-1588 time synchronization protocols produce precision time signals which are converted to precision interval signals. The correction processor uses the precision interval signals to count pulses of the oscillator. A correction circuit compares the counter output with a predetermined value and generates an error signal may be used to correct the oscillator or may be propagated to consumers of the oscillator. An arbitrary reference oscillator may be used to generate the precision timing signals propagated on the network, to slave other oscillators to it. The precision of the reference oscillator may be deliberately overstated to insure it is used as a master.

Abstract: A system and method are provided which add, via an add-on module, synchronization functionality to an instrument that does not otherwise support such synchronization functionality. Various synchronization techniques may be supported by the synchronization module. For instance, in certain embodiments the synchronization module supports message-based synchronization techniques and/or time-based synchronization techniques. Accordingly, in certain embodiments, the add-on module supports synchronization with another device (e.g., another instrument or another add-on module coupled to an instrument) via synchronized local clocks (e.g., IEEE 1588) and messaging over a communication network. In certain embodiments, the add-on module additionally or alternatively supports the use of “time bombs” to trigger scheduled actions on the instrument with which the synchronization module is interfaced.

Abstract: Location of an emitter using leaky cables. A two-channel receiver determines the location of an emitter by measuring the phase and/or amplitude difference between emitter signals received by leaky cables. In one embodiment, two leaky cables having different propagation velocities are used. In a second embodiment also suitable for use with fiber optic cables, two cables having the same propagation velocity are used, but have different lengths, the extra length being taken up by serpentine patterns or loops. A single cable in a loop may also be used. The leak points on the cables may be passive, or may be controlled RF switches.

Abstract: Network aware oscillator synchronization via a computer network. A correction processor connected to an oscillator uses precision timing signals propagated over a digital network to generate an error signal. IEEE-1588 time synchronization protocols produce precision time signals which are converted to precision interval signals. In one embodiment a correction processor uses the precision interval signals to count pulses of the oscillator. A correction circuit compares the counter output with a predetermined value and generates an error signal. The error signal may be used to correct the oscillator, as in a voltage controlled oscillator. Or, the error signal may be propagated to consumers of the oscillator. This error signal, for example, may be used to correct an instrument display. An arbitrary reference oscillator may be used to generate the precision timing signals propagated on the network, slaving other oscillators to it.

Abstract: Location of an emitter using leaky cables. A two-channel receiver determines the location of an emitter by measuring the phase and/or amplitude difference between emitter signals received by leaky cables. In one embodiment, two leaky cables having different propagation velocities are used. In a second embodiment also suitable for use with fiber optic cables, two cables having the same propagation velocity are used, but have different lengths, the extra length being taken up by serpentine patterns or loops. A single cable in a loop may also be used. The leak points on the cables may be passive, or may be controlled RF switches.

Abstract: In a response calibration method, a stimulus signal having a non-zero bandwidth is coupled to a receiver through a signal path that introduces distortion to the stimulus signal. The receiver acquires a first digital representation of the stimulus signal at an output of the signal path with the receiver adjusted to a first spectral position, and acquires a second digital representation of the stimulus signal at the output of the signal path with the receiver adjusted to a second spectral position that is shifted from the first spectral position by a predetermined frequency offset. The frequency response of the receiver when the receiver adjusted to the first spectral position is equated to the frequency response of the receiver when the receiver is adjusted to the second spectral position.

Abstract: The response of a receiver is calibrated using frequency-shifted stimulus signals. A source provides a stimulus signal that has a non-zero bandwidth and an adjustable spectral position. A signal path coupled between the source and the receiver introduces distortion to the stimulus signal. The receiver acquires a first digital representation of the stimulus signal at an output of the signal path with the stimulus signal adjusted to a first spectral position and acquires a second digital representation of the stimulus signal at the output of the signal path with the stimulus signal adjusted to a second spectral position that is shifted from the first spectral position by a predetermined frequency offset. A processor, designates the distortion introduced to the stimulus signal by the signal path to be equivalent at the first spectral position and the second spectral position.

Abstract: Display of signals containing inter-symbol interference (ISI). An input signal is modeled as comprising an ideal signal plus ISI plus error. In a first embodiment of the invention, an error signal and an ideal signal are derived from the input signal. The ideal signal is combined with the error signal producing an ideal signal with errors. In a second embodiment of the invention, a first signal comprising the ideal signal plus ISI plus error is derived. A second signal comprising only ISI is derived, and subtracted from the first signal, producing a signal containing the ideal signal plus error.

Abstract: The response of a receiver is calibrated using frequency-shifted stimulus signals. A source provides a stimulus signal that has a non-zero bandwidth and an adjustable spectral position. A signal path coupled between the source and the receiver introduces distortion to the stimulus signal. The receiver acquires a first digital representation of the stimulus signal at an output of the signal path with the stimulus signal adjusted to a first spectral position and acquires a second digital representation of the stimulus signal at the output of the signal path with the stimulus signal adjusted to a second spectral position that is shifted from the first spectral position by a predetermined frequency offset. A processor, designates the distortion introduced to the stimulus signal by the signal path to be equivalent at the first spectral position and the second spectral position.

Abstract: In a response calibration method, a stimulus signal having a non-zero bandwidth is coupled to a receiver through a signal path that introduces distortion to the stimulus signal. The receiver acquires a first digital representation of the stimulus signal at an output of the signal path with the receiver adjusted to a first spectral position, and acquires a second digital representation of the stimulus signal at the output of the signal path with the receiver adjusted to a second spectral position that is shifted from the first spectral position by a predetermined frequency offset. The frequency response of the receiver when the receiver adjusted to the first spectral position is equated to the frequency response of the receiver when the receiver is adjusted to the second spectral position.

Abstract: Error display in a multiple carrier modulation format. In a multiple carrier modulation format such as OFDM, displaying error spectrum plots and error time plots. The error spectrum plot shows a set of bar graphs arranged by carrier, each bar graph showing error points for that carrier collected over a plurality of symbol times. The error time plot shows errors over all carriers plotted as a symbol time series. Average errors in both plots may be indicated, and connected to show trends.

Abstract: Power levels for a code-division multiple access (CDMA) signal with layered orthogonal codes are displayed. When displaying power levels for multiple code layers, a power level for each active code channel is displayed using a bar. A width of the bar indicates in which code layer each active code channel is active. A color of the bar also can be used to indicate in which code layer each active code channel is active. For example, a power level for each active code channel is displayed using a hollow bar and a power level for each inactive code channel is displayed using a line. Alternatively, a power level for each inactive code channel is displayed using a hollow bar and power level for each active code channel is displayed using a solid bar. When displaying a power level for a single code layer, a power level for each active code channel in the single code layer is displayed using a hollow bar, and a power level for each code channel which is inactive in the single code layer is displayed using a line.

Abstract: A narrowband spectrum analyzer separates and analyzes a chosen segment of a periodic signal. The signal to be analyzed is digitized by an A/D converter. A gate generator is configured to trigger on a particular portion of the signal waveform and to identify the beginning and end of the chosen segment. Over the interval of the segment, the gate generator produces a digitized gate sequence. The envelope of this sequence may be rectangular or, preferably, may be that of a particular window function. The digitized signal is multiplied by the gate sequence and the multiplier output is then furnished as a train of gated segments to a signal processor for narrowband (high resolution) spectrum analysis. The length of the train is chosen to enable the signal processor to provide the desired resolution. Provision is made for removal of any DC component in the chosen segment before multiplication to reduce the possibility of aliased spectral terms in the processor output.