Carsten Groen's (OZ9AAR) personal place

Dual RF Head - Ethernet, Web enabled
1 MHz to 10 GHz power sensor/SWR

Until now, I have made three different Dual RF Head devices:

1. Dual RF Head - Analog- Gives out analog voltages dependent on the RF input power
2. Dual RF Head - USB- Connects via USB-C to PC (virtual serial port), Windows application w. source available
3. Dual RF Head - M5- Attaches to a Tab5/CoreS3 touchscreen, used as a standalone power meter (or built in)

I decided to make a fourth version, the Dual RF Head - Ethernet. This version connects to your local network via Ethernet. The RF frontend of this device is exactly the same as the other three Dual RF Head versions, it covers from 1 MHz to 10 GHz and accepts a maximum of +10 dBm on its two inputs.

The Dual RF Head - Ethernet sends out data just as the Dual RF Head - USB does, as a simple ASCII string. The "Ethernet" version streams the data over a TCP/IP socket connection (you can have multiple clients). You can use the "Dual RF Head PC application" to show the data and to configure the device, or you can make you own software for this.

You can show live data using a normal web browser or using the Dual RF Head - USB application (or your own)

The device can be used as a FWD/REF power sensor, connect it to the FWD and REF ports of an directional coupler and the Dual RF Head Ethernet will calculate the forward and reflected (CW and peak) power as well as the VSWR value. The device can also be used as a simple "two channel milliwatt meter" with >50 dB dynamic range within ±1 dB.

The two RF inputs can measure from around -50 to +10 dBm with great linearity and resolution.

Connected directly to a power source, -50 dBm is the same as 10 Nanowatts! Connected to a directional coupler, you can measure several Kilowatts with the Dual RF Heads, all with a dynamic range of 60 dB (1:1000000)!

If you need a directional coupler for the Dual RF Head, take a look here.

The Dual RF Head - Ethernet senses, as do its "older brother", the original Dual RF Head, CW power. The Ethernet version on this page, will also try to find the peak (PEP) value of the signal and present that as the "peak" value. The peak value will be shown on the two bar graphs on the main window of the PC application. Enabling the "Peak hold" checkbox, also the digital (number) displays will show the peak value.

Currently, I now have three different "Dual RF Head" devices:

1. Dual RF Head - Analog - Gives out analog voltages dependent on the RF input power
2. Dual RF Head - USB - Connects via USB-C to PC (virtual serial port), Windows application w. source available
3. Dual RF Head - M5 - Attaches to a Tab5/CoreS3 touchscreen, used as a standalone power meter (or built in)
4. Dual RF Head - Ethernet - Connects via Ethernet to your local (or remote) network

I am able to deliver finished Dual RF Head - Ethernet devices for €225,- each plus shipping. Send me an email if interested, contact info on the CV/Contact page.

Devices delivered will be calibrated at a (by you defined) specific band/frequency (up to 3 GHz is as high as I can go, the device covers up to 8/10 GHz!).

Small demo:

Calibration in system:

Webbrowser access

Using a normal webbrowser, you can access the built-in webserver in the Dual RF Head - Ethernet device. You can either use the default webpage of the device, or you can even make your own, and upload that to the device (will de explained later on here on this page).

The device will reply with the current data as a JSON structure if you do a HTTP "GET" request on the file /dynamic.json (please note that the device ONLY supports HTTP and NOT HTTPS!). Details for all of this will be added soon to this page also.

Using the built-in webpage, you can monitor the forward and reflected power, as well as the SWR. The scales for the forward and reflected power will "autoscale". Using the checkbox "Peak / Average" you can switch between peak and average power, the switch "Dark theme" will enable dark theme to the layout. Both settings are persistent in the browser on your PC.

Selecting "Dark theme":

You can change the display from Watt to "dBm" using the "dBm/Watt" checkbox:

Background

This design is also heavily influenced by my original Dual RF Head,  Dual RF Head - USB and Dual RF Head - M5 projects.

All the designs are based on the same dual logarithmic sensor chip, the ADL5519 from Analog Devices. The chip is not exactly cheap, but it has some very nice features, primarily:

• Wide bandwidth: 1 MHz to 8 GHz (useable to 10 GHz)
  
• Dual-channel and channel difference output ports
  
• Integrated accurate scaled temperature sensor
  
• 62 dB dynamic range (±3 dB)
  
• >50 dB dynamic range with ±1 dB up to 8 GHz

Datasheet for ADL5519

I added 10 dB attenuators on both inputs, these ensures a better return loss on the two inputs (RL better than 20 dB on both inputs).

The analog signals from the ADL5519 device are measured by a 12 bit ADC inside a Cortex M4 processor (NXP LPC54628). This design uses an external 2.500V precision voltage reference for the ADC. The processor connects via 10/100 MBps Ethernet to your local network (supports both DHCP and fixed IP address). 

The device is powered via a 2.1mm DC plug (center pin is positive). Nominal voltage supply is 12VDC (absolute maximum is 14VDC!), current consumption is around 180 mA.

The design

The ADL5519 logarithmic sensor chip outputs five analog signals. These are OUTA, OUTB, OUTN, OUTP and TEMP.

OUTA/OUTB: These are the logarithmic outputs from the two channels, A and B. The output is very close to -22 mV/dB (higher RF input yields lower voltage).

OUTP/OUTN are outputs directly from the ADL5519, these are the sum and difference outputs (see datasheet for ADL5519).  

TEMP is "temperature" output. The ADL5519 measures the temperature and outputs an analog voltage based on the temperature.

These five analog values are read and processed by the processor inside the device. The processors firmware will take these analog values (CW) and filter them and then calculate FWD/REF/VSWR based on calibration factors.

Both the calculated values and the raw measured values will be output via a (or multiple, up to 8) TCP/IP socket connection(s) and can be read by a suitable application, one possibility is the "Dual RF Head PC application".

Frequency sweep, 1 MHz to 3 GHz

Below is a graph showing the mV reading on IN A for both -10 dBm and -40 dBm input levels. Measurements are taken at:

1, 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 2600, 2700, 2800, 2900 and 3000 MHz.

The error seen here will be removed once you do a calibration of the device for the frequency (band) you will be using the Dual RF Head on (sensitivity rises with frequency).

Frequency sweep, 100 MHz to 3 GHz

Below is a sweep taken from 100 MHz to 3 GHz for 10 different power levels (from -40 to +5 dBm). This is done in increments of 100 MHz.

The X axis is frequency in MHz, Y axis is voltage in mV (approx 21  mV/dB) and the different traces are for the different power levels from -40 to +5 dBm in increments of 5 dB.

Below the graph are the raw data.

Frequency sweep, 1 MHz to 96 MHz

Below is a sweep taken from 1 MHz to 96 MHz for 10 different power levels (from -40 to +5 dBm). This is done in increments of 5 MHz.

The X axis is frequency in MHz, Y axis is voltage in mV (approx 21  mV/dB) and the different traces are for the different power levels from -40 to +5 dBm in increments of 5 dB.

Below the graph are the raw data.

PC Tool

Data from the Dual RF Head can be visualized in a simple PC application. The application will show power (fwd/ref/swr) and it can also log the data measured to a CSV file that later can be opened in f.ex Microsoft Excel. The application is also used when configuring the Dual RF Head and when new firmware needs to be downloaded to the microcontroller.

You can also choose to use the data from the Dual RF Head directly, the device emits data as a serial ASCII device (see "Data format" below).

Using the PC Tool, you can show the power from the FWD/REF port in either Watt or dBm. Clicking on one of the two digital displays will change between Watt and dBm. If the "Attn. Pfwd=>Ant(dB)" is set to a value different from 0 in the settings, clicking on the "Pfwd" bargraph will switch between Pant (power at antenna) and Pfwd (power measured directly).

(when power gets lower than 6 dB below the "Power min forward", the device will show this is "0")

When you start the program it will default to use "Dual RF Head - USB.cfg" as configuration file. When starting the program you can define another CFG file to use instead. This makes it easy to start the program with different configurations.

The project/source code is available for the application (C# project), please contact me.

The PC application can be downloaded from the Dual RF Head - USB page.

Settings in the application. Calibration is done using the same method as the Dual RF Head uses.

Update of firmware

Using the PC Tool, it is possible to update the firmware in the device.

Make sure the device is connected to the PC, the IP address port is selected in "Settings".

Make also sure that the Dual RF Head currently is delivering data to the PC.

Then select the menu item "Settings -> Update firmware". The firmware will be fetched from a server on the Internet and transferred to the Dual RF Head device.

Data format

The data from the Dual RF Head - Ethernet is sent as a simple <CR> terminated text string over a TCP/IP socket connection (supports max 8 simultaneous clients) and/or you can access it via HTTP requests as a JSON structure.

New data are sent from the device approximately 20 times per second.

The string contains all the data, both the raw ADC measured voltages, internal temperature, the forward (A port) and reflected (B port) calculated values (in Watt and dBm).

These values are calculated according to the calibration done.

The string received from the device:

CNT=4463, VERS=0.12, FWD=51.62 W, Peak FWD=200.88 W, REF=0.01 W, Peak REF=0.01 W, SWR=1:1.03, FWD=47.13 dBm, Peak FWD=53.03 dBm, REF=11.09 dBm, Peak REF=11.09 dBm, Vfwd=974.7 mV, Vref=1767.0 mV, TEMP=17.2, OUTP=602.6 mV, OUTN=2140.5 mV*7727

The fields:

1. CNT=4463
   1. This is an incrementing value (approx. 21 sets of data per second)
2. VERS=0.12
   1. Version number of the firmware in the connected Dual RF Head device
3. FWD=51.62 W
   1. The power in Watt on port A 
4. Peak FWD=200.88 W
   1. Peak power on port A in Watt (reset after 2 seconds)
5. REF=0.01 W
   1. The power in Watt on port B 
6. Peak REF=0.01 W
   1. Peak power on port B in Watt (reset after 2 seconds)
7. SWR=1:1.03
   1. Calculated VSWR value
8. FWD=47.13 dBm
   1. Power in dBm on port A (-99.99 means at least 8 dB below min. calibrated)
9. Peak FWD=53.03 dBm
   1. Peak power in dBm on port A (reset after 2 seconds)
10. REF=11.09 dBm
    1. Power in dBm on port B 
11. Peak REF=11.09 dBm
    1. Peak Power in dBm on port B (reset after 2 seconds)
12. Vfwd=974.7 mV
    1. Raw voltage (filtered) measured on port A from ADL5519
13. Vref=1767.0 mV
    1. Raw voltage (filtered) measured on port B from ADL5519
14. TEMP=17.2
    1. Temperature of the ADL5519 chip in degrees Celsius (filtered)
15. OUTP=602.6mV
    1. The voltage on the OUTP signal (filtered) from ADL5519
16. OUTN=2140.5 mV
    1. The voltage on the OUTN signal (filtered) from ADL5519
17.  *7727
    1. CRC16 (4 digit HEX) of the data from start until (excluding) the "*". C# checksum algorithm here

Downloads

You will find the Windows PC application on the page of the Dual RF Head - USB.