Three-device setup
From this release, a third SDR device can be configured in the Devices tab in Settings to extend the functionality of the Satsagen VNA:

Set three devices by clicking on the corresponding radio button, next click the RX/2 device tab, and set the SDR device you want to use as the third device.
Finally, in the SNA/VNA Mode tab, select the VNA item from the Mode list and Dual RX-Device from the Dual Port Interface list.

With the above configuration, the VNA will use the third device as a second receiver, and it will be available for S11 and S21 measurements in real time without manually switching the DUT connections.
The mandatory conditions for the correct functioning of the three-device configuration are:
- A common reference clock source (the CLK Source in the above image). Alternatively, the external clock source is connected only to the first device, and the reference to the other two is provided with a daisy chain connection.
- Devices 1 and 3 designated to the RX role must have two synchronized RX channels, so with the current version 0.9.3.3, only Pluto rev. C/D devices are compatible.
- Device 2, designated as TX, can also have only one TX channel, but this requires two ports, TX+ and TX-, or the addition of a splitter. Several devices are compatible with the TX device, including Pluto and the PLL synthesizers LMX2595, ADF4251, and others.
LMX2595 support
By connecting an LMX2595 board to Satsagen, the application can function as a Generator/sweeper and Tracker in SNA/VNA operations from about 100MHz up to and beyond 20GHz with an output power capable of achieving more than sufficient dynamic range for the characterization needs of filters and other DUTs.
Satsagen with an LMX2595 as TX device, and an ADALM-PLUTO as RX device in fifth harmonic mode, can provide approximately 40dB of dynamics at 24 GHz!

To improve measurements above 20GHz, a cavity filter should be used to reduce the fundamental of the LMX2595 (at frequencies above 15 GHz, an internal chip doubler is activated) because it can become “important” and saturate the first stages of the RX device. Two coupled guide transactions can be used as a filter.

Support for boards with the LMX2595 PLL synthesizer is provided via a USB interface consisting of an Arduino microcontroller or a Raspberry Pi Pico. See the page relating to this multifunction interface USBDAALBFER for the schematics, sources, and binaries that can be used.
Some tips for using this PLL board:
- Using a Raspberry Pi Pico (and Pi Pico 2) is preferable because the input and output work at the same 3.3V level as the LMX2595, so there is no need for voltage level adaptation components. Furthermore, uploading the firmware to the Pi Pico can be reduced to simply copying the binary file provided here onto the Pi Pico disk, which is activated by holding down the button and inserting the USB into the PC, so there is no need to equip yourself with the Arduino compilation environment.
- On some LMX2595 boards from China, part of the connector pin silkscreen is on the back of the board:

- The LMX2595 5V power supply should be supplied via a dedicated USB port or with a separate power supply, as the board during operation can reach absorption peaks of 400mA and more, therefore, it is not recommended to power it via the 5V pin of the microcontroller, whether it is an Arduino or a Raspberry.
- The GND connection between the LMX2595 board and the microcontroller is also important to ensure correct SPI operation. It should be done with short connections and using more GND pins on the microcontroller near the pins dedicated to the SPI.
- Finally, metal containers are recommended for the LMX2595 board and the receiving device (ADALM-PLUTO).
Stand-alone startup of PLL synthesizers
From this version, there is a function that allows you to program the Arduino or Pico interface combined with a supported PLL synthesizer, such as the LMX2595 just seen, for stand-alone use, that is, the interface and the PLLs can function as CW generators at a fixed frequency and power simply by powering them, even disconnected from Satsagen. This feature can be useful if a temporary local oscillator is needed for our down-converter or up-converter projects.
To use the above functionality, follow these steps:
- Start the application with the devices connected
- Start the Generator and set the desired frequency and power
- By keeping the Generator ON, click on the Save the Generator state to the device menu under Settings -> Device stored settings.
You can turn off Satsagen and disconnect the interface and PLL devices from the PC now. If the interfaces with the PLLs are powered via USB or with a separate power supply, they will automatically start at the preset frequency and output power, without the aid of Satsagen as a driver.
To reset the above setting on the interface, so that it no longer starts automatically and stops the PLLs from working as stand-alone CW generators, repeat the above procedure with the Generator turned OFF:
- Start the application with the devices connected
- Leave the Generator turned OFF and click on the Save the Generator state to the device menu under Settings -> Device stored settings.
You can turn OFF Satsagen now and disconnect the interface and PLL devices from the PC; the stand-alone operation setting has been reset.
Harmonic Extended Filter
In SNA scans with tracking generator, especially in harmonic mode, we noticed the presence of unwanted “peaks”, for example around 24 GHz, due to the combination of the high RX Gain setting required and the presence of harmonics of the RX local oscillator falling right in the IF range.
From this version of Satsagen, you can activate an EF filter, similar in operation to the one already present in the Spectrum Analyzer, also for TSA/SNA operations, by clicking on the EF button in the central panel of the application:

The EF filter will eliminate the above artifacts during the scan by taking two separate readings for each point, slightly shifting the frequency of the RX local oscillator. The filter will compare the pair of readings, eliminating signals present at the same frequency on only one of the two readings, an unmistakable sign of artifacts due to the RX local oscillator.
On the other hand, using the EF filter will cause a slight slowdown in SNA scans.