Devices ======= Concepts ~~~~~~~~ Mixed Signals ------------- Mixed-signals describe nonlinear time-variant systems: - Nonlinear-Systems: Produce *nonlinear distortion*, described by *analog signals* w.r.t freq :math:`X(f)` - Time-Variant Systems: Produce *memory*, described by *digital signals* w.r.t time :math:`x(t)` - Time-Variant Nonlinear-Systems: Require *envelope signals* w.r.t time, freq :math:`x(t, f)` .. raw:: html

Signal Transforms
To \ From:	Envelope	Frequency	Time	Switching
Envelope	= tf.tf( )	= ff.tf( )	= tt.tf( )	= ft.tf( )
Frequency	= ff.ff( )	= ff.ff( )	= ff.ff( )	= ff.ff( )
Time	= tt.tt( )	= tt.tt( )	= tt.tt( )	= tt.tt( )
Switching	= ft.ft( )	= ft.ft( )	= ft.ft( )	= ft.ft( )

The signals describe a nonlinear time-variant system as follows: * **Envelope**: Raw data capture. * **Frequency**: Frequency Spectrum waveform centered around each harmonic of a carrier frequency. * **Time**: Sub-Sampled waveform where each digital sample (:math:`\tau_t`) contains analog sub-samples (:math:`\tau_f`). * **Switching**: Analog switching behaviour computed over a slice of bandwidth (BW). Units ----- To simplify data storage and manipulation, each mixed-signal is recorded in **base-linear** units: - Voltage: [:math:`V`] - Current: [:math:`A`] - Impedance: [:math:`\Omega`] - Power [:math:`\sqrt{W}`] This ensures that all variables can be converted from base linear units to decibels (dB) using :py:class:`rW2dBW ` Objects ------- An **Object** (such as an device) contains properties (such as signals). An object may also control the display, sweep limits, and optimization limits of each property using the following metadata: 1. :code:`obj.info` of type :py:class:`AttributeInfo `, which contains: * :py:class:`Info ` metadata for each object property. 2. :code:`obj.__info__()`, a magic method that dynamically initializes the :code:`self.info` metadata. Devices ------- A **Device** :py:class:`AbstractDevice ` is an **Object** that contains: 1. :code:`DeviceClass.firmware_map`, a static dictionary that contains supported device firmware information. 2. :code:`device.handles`, a dictionary of device handles (any type) that *uniquely* describes a remote connection to the physical device(s). 3. :code:`device.connect_handles()`, connects the device and stores device references in :code:`self.handles`. 4. :code:`device.preset()`, presets the device each time a *unique* connection is made. 5. :code:`device.disconnect_handles()`, disconnects the device and removes device references from :code:`self.handles`. 6. :code:`device.info` contains display, sweep limit, and optimization limit meta-data. Programming ~~~~~~~~~~~ Adding a Device Driver ---------------------- 1. Select the device(s) that best describe the instrument you want to control. Here are some common examples: .. raw:: html

`LF Source`

DC Supply

AWG

DAC

`LF Receiver`

Multimeter

Oscilloscope

ADC

`LF ZTuner`

Open/Short Circuit

Varactor

Active Load

`RF Source`

Signal Generator

VSG

AWG

Pulse Generator

SRD

`RF Receiver`

VNA

VSA

Power-Meter

Oscilloscope

Sampling Scope

`RF ZTuner`

50 Ohms

Passive Load

Active Load

2. Select the device modulation complexity. For example, an RFSource can be inherit the following classes: a. :py:class:`NoRFSource (easy) ` b. :py:class:`NoRFSourcePulsed (harder) ` c. :py:class:`NoRFSourceModulated (hard) ` 3. Write the driver. .. tip:: It's usually best to copy from previous drivers. .. tip:: Store configuration data in a config file. .. tip:: Complex instruments may require multiple drivers. Some high-end VNAs may contain: * LF Source * LF Receiver * RF Source * RF Receiver Avoid repetition by programming *common* functionality in shared functions, such as: * preset() * arm() * trigger() .. warning:::: Realtime parametric sweeps reduce I/O bottlenecks by serializing a sweep into a really long time-domain signal. This implies that a signal :math:`x(t, f)` does not always contain the same dimensions along the time-axis. Avoid referencing the following time-domain settings in the device drivers: * Settings().time * Settings().t_stop * Settings().t_points 4. Register the driver by: a. Place the source code file in the following search path: .. code-block:: bash sknrf/device/instrument//* b. Place the config file in the following search path: .. code-block:: bash sknrf/data/config/device/instrument//* 5. Test the driver as follows: .. raw:: html

* Select the driver * Modify the Address * Verify the firmware versions match * Test the driver * Load the driver * Run a Single Measurement * Plot the results. API --- The following is a minimal example of how to connect to an instrument: .. code-block:: python from sknrf.device.base import AbstractDevice from sknrf.device.instrument.lfsource.base import NoLFSource AbstractModel.init() dev = NoLFSource()