AnnaLyza VNA

Introduction

AnnaLyza VNA is a low-cost USB-based 2-port Vector Network Analyzer / Antenna Analyzer for the 2.4 GHz ISM band. The frequency range is 2200 to 2700 MHz.

The software requires Java 8 or later and has been tested under Windows 7 and 10. It has been reported to work under MacOS 10.12 and Ubuntu 18.04. You can test drive the software in a demo mode without the device to explore most functionality. The matching circuit editor is quite useful even in demo mode.

Specifications - ALV2227A2

Frequency Range	2200 MHz to 2700 MHz
Impedance	50 Ohms
Output Power	-18 dBm to -3 dBm (-7 dBm typical)
Input Power	Up to 0 dBm (+10 dBm absolute maximum)
Port Count	2
Port Isolation	45 dB
Noise Floor	-40 to -60 dB ¹
RF Connector	2x SMA
Data Connector	Mini USB
Supply Current	300mA max
Dimensions	115mm x 75mm x 30mm (4½" x 3" x 1¼")
Mass	90 grams (3.2 oz)
Operating Temperature	15°C to 25°C (60°F to 77°F) ²

¹ This device only has a single receiver, so measurements with the same output port can affect each other's accuracy (S11 affects S21 and vice versa; S22 affects S12 and vice versa). The error and noise levels are typically 40 dB below the input power on the opposite port, with a lower limit of -60 dB.

² The receiver is temperature stabilized when the device is operated in this range. The device will work from 5°C to 40°C (40°F to 105°F); however, the accuracy will be reduced. Depending on the ambient temperature the warm-up time is between 20 and 60 seconds.

Software Features

Smith chart and magnitude/phase chart with markers and configurable trace colors and visibility.
Full two-port SOLT calibration supported, but any subset is possible.
Adjustment of reference planes manually or by capturing an open or short circuit measurement.
Matching circuit editor that allows you to see in real time how the S11 and S22 measurements would change by adding a matching circuit.
Capture and hold the current measurement and show relative measurement.
Load and save measurements (saving to Touchstone format supported).

This is the initial release. More features are on the way.

Limitations of the current software version:

Measurements are fixed to 5 MHz steps in the range from 2200 to 2700 MHz.
The output power is not configurable and fixed to approximately -7 dBm.
The acquision sequence is not configurable. The device measures all 4 S-parameters on a single frequency before moving to the next frequency.
Loading of Touchstone files is not supported
It is not possible to save the configuration (trace colors, visibilities, marker frequencies). What can be saved is trace data, the calibration, and matching circuits.

Examples and Accuracy

This section shows some measurement examples to illustrate what kind of accuracy to expect. The errors largely result from uncompensated non-linearities in the VNA's receiver and cross-talk between signals in the VNA which are not captured by the error model.

Errors are going to be worse the further away the measurement is from a calibration point (short, open, 50 Ohms). Therefore, the worst errors can be observed on the top and bottom of the Smith chart.

For the figures below I performed a full two-port calibration with the following cables: 2 meter coax cable with approximately 2 dB loss on port 1; 0.4 meter coax cable with approximately 0.8 dB loss on port 2.

The first example is an S11 and S22 measurement with open circuit with a shorter length (calibration standards removed from the coax cables). The traces are near the top of the Smith chart, so they are at a point where the error is at a maximum.

Measurement Example 1: Region with worst accuracy. Click for full-size image.

The next example is another open circuit, this time longer than in the calibration setup (SMA M/F and F/M adapters added).

Measurement Example 2: Open circuit with different length. Click for full-size image.

The next example is with unterminated attenuators attached to the end of the cables. S11 is with a 2dB attenuator; S22 is with a 6dB attenuator.

Measurement Example 3: Unterminated attenuators. Click for full-size image.

The next example shows through measurements (S21, S12) with 2dB attenuator.

Measurement Example 4: 2dB attenuator. Click for full-size image.

The next example shows through measurements (S21, S12) with 30dB attenuator.

Measurement Example 5: 30dB attenuator. Click for full-size image.

The next example shows all four S-parameters with two types of antennas connected.

Measurement Example 6: Antennas. Click for full-size image.