Signal Generation¶

An overview of the signal generation functionality available in this package, along with information about Tektronix signal generators.

Function Generation¶

A function is a limited set of common waveforms that are provided by default through the instrument. The simplicity of these waveforms allows for output parameters like waveform length and sample rate to be abstracted away. Frequency replaces these in order to provide signals that are easy to quantify and manipulate.

Arbitrary Function Generators (AFGs) utilize a phase increment process and a data lookup table to provide variable frequencies. The phase increment calculated is dependent on the waveform length and frequency requested. This has a side effect where the phase increment can be larger than one index in the lookup table. Functions bypass this issue by being simplistic enough that waveform length reduction does not have a detrimental effect on the end output.

Arbitrary Waveform Generators (AWGs) enforce one cycle per sample, allowing the output to be the same shape regardless of clock rate. The number of samples that occur during a second is referred to as a sample per second (S/s), a unit that determines the frequency of the waveform. With low frequency functions, AWGs are functionally identical to AFGs, besides offering more constrained amplitudes and offsets.

Class Structure¶

The AFG and AWG drivers both inherit from a shared, private mixin class that provides common functionality. Similarly, TekScope is responsible for the AFG internal to the scopes themselves, commonly referred to as an IAFG. All of these classes inherit SignalGeneratorMixin, which includes a list of methods that define common functionality throughout all signal generators.

Each signal generator class (AFG, AWG, and TekScope if the AFG license is installed) will contain a dictionary of source channel classes, which are defined on first access. Each of these source channel classes ( AFGSourceChannel, AWGSourceChannel, and InternalAFGChannel ) represents an output on the signal generator (or the IAFG in the case of an oscilloscope).

These source channel classes contain methods and properties that pertain to PI commands, which only apply changes to one output. For example: the afg.source_channel["SOURCE1"].set_amplitude() call, (see AFGSourceChannel.set_amplitude()), will change the amplitude only for source output 1.

SignalGeneratorMixin Methods¶

Each class has children which inherit the base abstracted methods. These methods are tailored to each signal generator, so the methods handle similarly, regardless of the different PI commands required.

source_device_constants is a property that holds information about what functions and memory sizes are allowed.

generate_function() is a method that allows the user to request a function from any source channel, provided an amplitude, frequency, and offset are supplied. Other key features include the ability to manipulate specific aspects of certain functions. Ramp waveforms can have their symmetry changed and duty cycle can be altered for pulse functions. The termination of the IAFG and any AFG can be specified using HIGHZ or FIFTY string literals. If the output needs to be inverted, the polarity can be changed on AFGs.

The setup_burst() method places the signal generator in a state for waveforms to be generated a set number of times. All parameters passed into the method are functionally identical to generate_function(), besides burst_count. burst_count specifies how many cycles of the waveform are to be generated.

generate_burst() writes a trigger to the signal generator, initiating the generation of a burst of waveforms.

get_waveform_constraints() will return a series of ranges that a waveform’s parameters must be within to be generated. These constraints can be used before generating a function to make sure that the parameters you will be supplying are not outside the bounds. The method only requires the desired waveform function (except on AWGs) to be provided. However, different aspects may need to be provided to get a more accurate representation of what can actually be generated. If no other inputs are provided, the smallest range of the attribute is chosen. For an AWG, the signal path affects the range of the offset and amplitude. Higher frequencies on AFGs will lower the upper bound of the amplitude, alongside which impedance is set.

set_waveform_properties() for AWGs is functionally identical to generate_function(), but does not turn the source channel off or on, nor will it stop or start an AWG.

Signal Generators¶

An overview of the different signal generators that are available in tm_devices. This includes:

• Features unique to each.
• Constraints for each waveform parameter.

TekScope Internal Arbitrary Function Generators¶

The TekScope series instruments are signal generators focused on waveform generation and operate on the Windows operating system. They accept communication through USB and TCPIP interfaces.

Requesting function generation on an IAFG will initially turn it off. The frequency, offset, function, impedance, and amplitude are set in the stated order. If the function is a SQUARE wave, the duty cycle is used to set how long the pulses are. Symmetry decides what direction the RAMP function skews. After all parameters are set, the source channel is then turned back on.

Setting up bursts of an IAFG involves setting it to burst mode and loading in a specified number of bursts.

IAFGs have access to the following functions, listed within SignalGeneratorFunctionsIAFG: SIN, SQUARE, RAMP, PULSE, PRNOISE, DC, SINC, GAUSSIAN, LORENTZ, ERISE, EDECAY, HAVERSINE, CARDIAC, ARBITRARY

MSO2, MSO4, MSO4B, MSO5, MSO5LP, MSO6, MSO6B, LPD6¶

Constraints¶

The amplitude and frequency range for the IAFG vary based on the desired function. These ranges are the same for each of the classes listed: MSO2, MSO4, MSO4B, MSO5, MSO5LP, MSO6, MSO6B, and LPD6

Sample rates are 250.0MS/s for ARBITRARY waveforms.

MSO5B¶

Constraints¶

The constraints for the MSO5B are identical to other tekscope models, except the upper frequency bound is doubled.

Arbitrary Function Generators¶

AFGs handle function generation identically to IAFGs except for the order in which the parameters are set.

All functions that are shared by each AFG exist within the AFG class.

Setting up bursts of the AFG involves setting the trigger on the device to external, so the burst does not activate on the internal trigger. Following this, the burst state is set to ON and mode set to TRIGGERED.

AFGs have access to the following functions, listed within SignalGeneratorFunctionsAFG: SIN, SQUARE, RAMP, PULSE, DC, SINC, GAUSSIAN, LORENTZ, ERISE, EDECAY, HAVERSINE, CARDIAC, NOISE, ARBITRARY

AFG3K, AFG3KB, AFG3KC¶

The AFG3K series instruments are function generating devices that also offer the capacity to generate arbitrary waveforms. They accept communication through USB, TCPIP and GPIB interfaces. These instruments have their own class representations, corresponding to the AFG3K, AFG3KB, and AFG3KC.

Constraints¶

The amplitude, offset, and frequency range for AFG3Ks are extremely varied, dependent on model number, frequency, and function. However, the sample rate of the entire AFG3K series is 250.0MS/s.

AFG31K¶

The AFG31K series instruments are function generating devices that also offer the capacity to generate arbitrary waveforms. They accept communication through USB, TCPIP, and GPIB interfaces. The AFG31K has its own class representation, corresponding to AFG31K.

Constraints¶

Arbitrary Waveform Generators¶

All functions that are shared by each AWG exist within the AWG class.

Function generation on AWGs is fundamentally different from AFGs. The AWG is stopped and the source channel being used is turned off. Predefined waveforms provided with the AWG are then loaded from the hard drive into the waveform list for the AWG5200 and AWG70K. The sample rate is not source dependent, instead, it is set through the parent class. The source channel provided has its waveform, offset, amplitude, and signal path set. These attributes can take a while to be set, though once complete, the source channels are turned back on and AWGCONTROL:RUN is sent to begin the transmission of the waveform.

The AWG class has some unique methods. generate_waveform() allows for a waveform name from the waveform list to be provided, instead of a function. The method is also distinctly different from the generate function as it relies on a sample rate being provided to generate the waveform. All functions that are generic to the AWG exist within the AWG class.

AWGs have access to the following functions, listed within SignalGeneratorFunctionsAWG: SIN, SQUARE, RAMP, TRIANGLE, DC, CLOCK

AWG5K/AWG7K¶

The AWG5K/7K series instruments are signal generators focused on waveform generation and operate on the Windows operating system. They accept communication through TCPIP and GPIB interfaces.

set_output_signal_path() is uniquely defined within the AWG5K and AWG7K classes, as it will set the value for AWGCONTROL:DOUTPUTx:STATE, which is a unique option not seen in the other AWGs.

set_offset() is conditioned to make sure that the AWG output signal path is not DIR, as the VISA query will time out otherwise.

AWG5K, AWG5KB, AWG5KC¶

The AWG5K series instruments have their own class representations, corresponding to the AWG5K, AWG5KB, and AWG5KC.

Constraints¶

The AWG5K series offers an upper sample rate range from 600.0MS/s to 1.2GS/s depending on the model number. Sending AWGControl:DOUTput[n] 1 or using DIR in set_output_signal_path() will reduce the maximum amplitude to 0.6V. This occurs by bypassing the internal amplifier, which reroutes the DAC directly to the differential output.

AWG7K, AWG7KB, AWG7KC¶

The AWG7K series instruments have their own class representations, corresponding to the AWG7K, AWG7KB, and AWG7KC.

Constraints¶

The AWG7K series instruments function identically to the AWG5K series, excluding the higher sample rate, lower amplitude, and offset range. The model number conveys information about the unit, with the second and third numbers indicating the maximum sample rate in Gigahertz allowed on the unit.

The AWG7K also includes varying options that directly affect these ranges, such as option 02 and option 06. These options will enforce the output signal path to always go directly from the DAC to the differential output.

AWG5200¶

The AWG5200 series instruments are signal generators focused on waveform generation which operate on Windows. They accept communication through USB, TCPIP, and GPIB interfaces.

The AWG52000 has its own class representation, corresponding to AWG5200.

set_output_signal_path() is uniquely defined within the AWG5200 as it has special output signal paths.

load_waveform() inherently has an operation complete check, as attempting to run overlapping commands while loading a waveform can lead to unintended behavior.

Constraints¶

The AWG5200 does not have a sample rate range dependent on the model number. Instead, it refers to which option is installed to provide the range of the sample rate. Option 25 on the devices provides a maximum rate of 2.5GS/s, whereas option 50 allows a maximum rate of 5.0GS/s. If option DC is provided, the DCHB signal output path amplitude range will be increased to have a maximum of 1.5V. The DCHV signal path increases this range further to 5.0V by including another amplifier.

Sequential, Blocking and Overlapping Commands:¶

The AWG5200’s programming commands are separated into three separated categories: Sequential, Blocking, and Overlapping. The type of command is important to consider, as using them in an incorrect order can lead to unintended results.

Sequential commands function as standard PI commands. They will not start until the previous command has finished. These commands tend to be fast and will allow for quick response times even if they are queued in the input buffer.

Blocking commands are very similar to Sequential commands. The main difference between Sequential and Blocking is that Blocking commands often take longer to execute.

Some commands can perform data analysis on another thread; these are referred to as Overlapping commands. They allow any command to be started while they are being executed. They cannot begin if the previous command was blocking or sequential, or if the operation complete status register is not set.

AWG70KA, AWG70KB¶

The AWG70K series instruments are signal generators focused on waveform generation. These instruments operate on the Windows operating system, and they accept communication through USB, TCPIP, and GPIB interfaces.

set_output_signal_path() is uniquely defined within the AWG70KA and AWG70KB classes. By default, it will first attempt to set the output signal path to DCA. If this fails (implying an MDC4500-4B is not connected), then a direct signal path will be set.

set_offset() is conditioned to make sure that the AWG output signal path has a DCA, as the VISA query will time out otherwise.

Constraints¶

The AWG70K signal generator is a special case where only the direct signal output path is allowed (unless option AC is installed). This means the amplitude is limited, and offset is not allowed to be set by default. However, there is a secondary device that allows for DC amplification, the MDC4500-4B. The MDC4500-4B provides the ability to utilize DC offset and large range of amplitude on an AWG70K.

Just like the AWG5200, the frequency is dependent on the option installed (150, 225, 216, 208). The first number in the option provides the number of source channels the AWG70K has; the next two numbers indicate the sample rate in Gigahertz.

Sequential, Blocking and Overlapping Commands:¶

The AWG70K also supports the Sequential, Blocking, and Overlapping commands mentioned in the AWG5200 section.