Abstract: A test and measurement instrument including a time domain channel configured to process a first input signal for analysis in a time domain; a frequency domain channel configured to process a second input signal for analysis in a frequency domain; and an acquisition system coupled to the time domain channel and the frequency domain channel. The acquisition system is configured to acquire data from the time domain channel and the frequency domain channel. Time domain and frequency domain data can be time aligned.

Abstract: A test and measurement instrument including an input port configured to receive an input signal; a digitizer configured to digitize the input signal; a decimator coupled to the digitizer and configured to decimate the digitized input signal to generate a decimated input signal; a digital downconverter coupled to the digitizer and configured to frequency shift the digitized input signal to generate a frequency shifted input signal; and a memory configured to store the decimated input signal and the frequency shifted input signal.

Abstract: Embodiments of the invention include devices and methods for searching IQ-based time-domain traces for events, marking the events, and analyzing intervals of interest at or around the events on a display unit of a test and measurement instrument. The test and measurement instrument can include an input terminal to receive an RF signal, an ADC to digitize the RF signal, a digital downconverter to produce I (in-phase) and Q (quadrature) baseband component information from the digitized RF signal, an acquisition memory to acquire and store a record, a trace generation section to generate one or more IQ-based time-domain traces, and a search unit to scan the IQ-based time-domain traces for one or more events. The search unit can locate and mark the events for display on a display unit of the test and measurement instrument.

Abstract: A test and measurement instrument and method for receiving a radio frequency (RF) signal, digitizing the RF signal using an analog-to-digital converter, downconverting the digitized signal to produce I (in-phase) and Q (quadrature) baseband component information, generating one or more IQ-based time-domain traces using the I and Q baseband component information, and measuring and displaying a variety of measurement values of the IQ-based time-domain traces. The IQ-based time-domain measurement values can be automatically generated and displayed, and/or transmitted to an external device.

Abstract: Embodiments of this invention provide enhanced triggering capabilities such as frequency and phase triggering in a test and measurement instrument, such as a Real-Time Spectrum Analyzer (RTSA) or oscilloscope. A test and measurement instrument can include input terminals to receive RF signals, an ADC to digitize the RF signals, a digital downconverter to produce I and Q baseband component information, and a power detector to determine a power level using the I and Q information. A comparator compares the power level received from the power detector with a user-definable power threshold, and produces a logic signal for enabling one or more phase or frequency demodulators. The one or more demodulators produce IQ-based time-domain traces derived from the I and Q component information when the power level determined by the power detector exceeds the power threshold. Trigger circuitry is configured to trigger on an event responsive to a delayed trigger enable signal.

Abstract: A test and measurement instrument including a plurality of input ports; an acquisition system coupled to the input ports and configured to acquire frequency domain data from the input ports; a user interface configured to present frequency domain controls for at least two of the input ports; and a controller configured to adjust frequency domain acquisition parameters of the acquisition system in response to the frequency domain controls such that frequency domain acquisition parameters associated with a first input port can be different from frequency domain acquisition parameters associated with a second input port.

Abstract: An apparatus for measuring a parameter of a digitized signal including a digitizer to digitize an input signal into a digitized signal, a rasterizer to generate a raster image from the digitized input signal, a processor to receive the raster image, and a control interface to receive an input control signal indicating a request for a measurement. The rasterizer is responsive to the control signal to generate the raster image from the digitized input signal, and the processor is responsive to the control signal to generate a histogram from the raster image.

Abstract: Pre-trigger and post-trigger acquisition for a no dead time acquisition system, where the data being displayed does not include a related trigger event, has a variable record length buffer having a maximum record length equal to a maximum desired pre-trigger interval, and has a trigger FIFO and timer for delaying the related trigger event. The record length of the buffer is determined by the desired pre-trigger interval, and fast rasterizers access the oldest data that encompasses the desired pre-trigger data. A first trigger event in the trigger signal may be delayed by a desired post-trigger interval before the fast rasterizers begin drawing the waveform data that encompasses the desired post-trigger data.

Abstract: A signal acquisition system has a signal acquisition probe having probe tip circuitry coupled to a resistive center conductor signal cable. The resistive center conductor signal cable of the signal acquisition probe is coupled to a compensation system in a signal processing instrument via an input node and input circuitry in the signal processing instrument. The signal acquisition probe and the signal processing instrument have mismatched time constants at the input node with the compensation system providing pole-zero pairs for maintaining flatness over the signal acquisition system frequency bandwidth.

Abstract: A low capacitance signal acquisition system has a signal acquisition probe having a low capacitance input circuit coupled to a compensation amplifier in a signal processing instrument via a signal cable. The low capacitance input circuit, the signal cable and the signal processing instrument input have mismatched time constants with the compensation amplifier having feedback loop circuitry providing adjustable gain and pole-zero pairs for maintaining flatness over the low capacitance signal acquisition system frequency bandwidth.

Abstract: A signal acquisition system has a signal acquisition probe having probe tip circuitry coupled to a resistive center conductor signal cable. The resistive center conductor signal cable of the signal acquisition probe is coupled to a compensation system in a signal processing instrument via an input node and input circuitry in the signal processing instrument. The signal acquisition probe and the signal processing instrument have mismatched time constants at the input node with the compensation system having an input amplifier with feedback loop circuitry and a shunt pole-zero pair coupled to the input circuitry providing pole-zero pairs for maintaining flatness over the signal acquisition system frequency bandwidth.

Abstract: A signal acquisition system has a signal acquisition probe having probe tip circuitry coupled to a resistive center conductor signal cable. The resistive center conductor signal cable is coupled to a compensation system in a signal processing instrument via an input node and input circuitry in the signal processing instrument. The signal acquisition probe and the signal processing instrument have mismatched time constants at the input node with the compensation system having an input amplifier with feedback loop circuitry and a compensation digital filter providing pole-zero pairs for maintaining flatness over the signal acquisition system frequency bandwidth.

Abstract: A test and measurement instrument including a plurality of digitizers, each digitizer configured to digitize an input signal to generate a digitized signal; a signal processor configured to combine at least two of the digitized signals from the digitizers into a combined signal; and a circuit configured to receive the combined signal.

Abstract: A mixed signal acquisition system for a test and measurement instrument allows configuring of the number of analog and digital channels in use. The instrument includes an analog input interface and an N-channel logic input interface for receiving an analog signal and an N-channel logic signal, respectively. An ND converter converts the analog input signal into an N-bit digital signal, and N latch circuits latch the N-bit logic signal. A multiplexer selects either the N-bit digital signal from the A/D converter, or the N-bit logic signals from the N latch circuits, and the selected signal at the output of the multiplexer is stored in an acquisition memory. By controlling the multiplexer selection, the number of analog channels and the digital channels can be controlled.

Abstract: A method of drawing a waveform image in a no dead time acquisition system, where consecutive drawing frames overlap, uses a master/slave relationship between two fast rasterizers. The master rasterizer draws a first display frame in response to a first trigger event in a trigger signal derived from an input signal. The slave rasterizer draws a second display frame in response to a subsequent trigger event in the trigger signal. The portion of the second display frame that duplicates data contained in the first display frame is either (a) suppressed when the first and second display frames are combined to form the waveform image or (b) displayed in a different shade/color.

Abstract: A simple, integrated control for pan and zoom of a display of data represented by a very long data record is in the form of a control knob having an outer ring for controlling pan and an inner knob for controlling a zoom factor. A zoom function is turned ON either by turning the inner knob (setting the zoom factor to a default value) or by (i) pressing an adjacent zoom or pan button or (ii) turning the outer ring (setting the zoom factor to a prior value when the zoom function was turned OFF). The zoom function may be turned OFF by turning the inner knob to set the zoom factor to 1× or by pressing the zoom button. The outer ring has individual positions divided into two groups: one group for controlling pan rate within a zoom window displaying a portion of the very long data record defined by a zoom box within a main window displaying the very long data record; and the other group for controlling pan rate of the zoom box within the main window for rapid movement from one end of the record to another.

Abstract: A waveform compression and display technique saves both a peak detected version (background version) and a decimated/lowpass filtered version (foreground version) of a sampled electrical signal. The two versions are displayed simultaneously overlaid together in a contrasting manner so as not to obscure information contained in either of them. The lowpass filtered version uses a series of simple lowpass filters with decimation to produce a single data stream from a plurality of data streams derived from the sampled electrical signal. The single data stream may then be subjected to additional filtering, such as a cascaded integrator-comb filter, to obtain a desired frequency bandwidth. When displayed, the peak detect pixels adjacent the decimated/lowpass filtered pixels may be adjusted in intensity so that the low frequency information of the lowpass filtered waveform is not lost, while the peak detect pixels further from the lowpass filtered pixels are intensified to highlight the high frequency information.

Abstract: A self-adjusting hold-off trigger circuit and method detects a threshold crossing between consecutive samples of a digitized input signal as edge events, identifies the crossing as a qualified trigger event if the crossing is in a desired direction based upon trigger criteria, and provides a trigger output when the qualified trigger event occurs greater than an approximate average or peak time after a preceding edge event.

Abstract: A noise rejection filter for a trigger circuit uses an algorithm that updates the filter output monotonically so long as the signal slope remains unchanged, maintains the filter output at a constant level when the signal slope changes but the difference between the sample value and the filter output is less than or equal to a hysteresis value, and changes the signal slope while updating the filter output when the difference is greater than the hysteresis value. This maintains the peaks of the input signal at the filter output. The noise rejection filter may be used in a trigger circuit prior to a comparator so that the trigger signal from the comparator accurately reflects the signal pulse width at a desired trigger level and trigger events are detected when the desired trigger level is near the peaks of the input signal.

Abstract: A method of drawing a waveform image in a no dead time acquisition system, where consecutive drawing frames overlap, uses a master/slave relationship between two fast rasterizers. The master rasterizer draws a first display frame in response to a first trigger event in a trigger signal derived from an input signal. The slave rasterizer draws a second display frame in response to a subsequent trigger event in the trigger signal. The portion of the second display frame that duplicates data contained in the first display frame is either (a) suppressed when the first and second display frames are combined to form the waveform image or (b) displayed in a different shade/color.