How To Measure VSWR Using A Rigol DSA800 Series Spectrum Analyzer
How to Measure VSWR using a Rigol DSA800 Series Spectrum Analyzer The purpose of this document is to provide step-by-step instruction on measuring the VSWR (Voltage Standing Wave Ratio) of a passive RF component. The VSWR can be used to judge the quality of impedance matching for cables and other passive devices. It is also mainly used to determine the efficiency of antennas to radiate power. A perfectly matched antenna/cable system will have a VSWR 1. In reality, VSWR's are typically in the 1.1 to 1.2 range. Higher VSWR's indicate a greater degree of impedance mismatch. For antenna user's this indicates less efficiency. Required Equipment To measure the VSWR, you will need the following: Rigol DSA800 series of Spectrum Analyzer with a tracking generator (-TG part number) (Optional) RIgol VSWR-DSA800 (You can calculate the VSWR manually using the return loss measurement calculations at the end of this document) Coaxial Directional Coupler or Rigol model VB1000 VSWR bridge with impedance match for component being tested Antenna or other component to test Impedance matched coaxial cable to connect coupler to the tracking generator. Depending on the Directional Coupler design, you may need another cable or adapter to connect it to the DSA. Test Steps for Analyzers that have the Rigol VSWR-DS800 option installed 1. Clean all connectors with a lint free swab and electronics contact cleaner. Make sure to remove any contamination, dirt, or metallic flakes in and around mating surfaces. 2. Connect the Rigol VB1000 series VSWR bridge or other directional coupler to the DSA. The Rigol VB1000 series can be attached to the analyzer as shown below: RIGOL – Uncompromised Performance. Unprecedented Value PAGE 1
If you are using another direction coupler or bridge, please see the connection instructions for the specific model you are using to ensure proper connections. NOTE: Leave the DUT connection of the coupler open at this time. This will provide 100% reflection and be used to minimize the effects of the cabling, adapters, and coupler. 3. Configure the DSA frequency span for the DUT by pressing the FREQ key on the DSA display and setting the Start and Stop frequency. Press FREQ Start Freq Use Keypad or scroll wheel to enter start frequency and select units. Press FREQ Stop Freq Use Keypad or scroll wheel to enter stop frequency and select units. RIGOL – Uncompromised Performance. Unprecedented Value PAGE 2
4. Set the tracking generator output amplitude level to a value that is appropriate for your DUT Press TG set TG level RIGOL – Uncompromised Performance. Unprecedented Value PAGE 3
5. Enable the tracking generator. This will begin sourcing an RF source that will sweep from the start frequency to the stop frequency Press TG TG On 6. Enable the VSWR automatic measurements (valid for instruments that have the VSWR-DSA800 option installed) Press MEAS VSWR ON RIGOL – Uncompromised Performance. Unprecedented Value PAGE 4
7. Normalize the output with no DUT connected to the DUT port on the VB1000 series bridge or directional coupler. Press MEAS SETUP CAL OPEN 8. Connect the DUT and associated cabling 9. Enable VSWR measurements Press VSWR The Yellow trace represents the return loss vs. frequency The Purple trace represents the full reflection from the VSWR bridge with no DUT connected (Cal Open) The Green trace represents the calculated VSWR curve for the DUT 10. Adjust the Ref Level to show the full range of the green VSWR curve 11. You can select markers (1,2,3, or 4) and move them to specific peaks to read out the specific VSWR value for each peak on the green curve as shown in the following picture: RIGOL – Uncompromised Performance. Unprecedented Value PAGE 5
RIGOL – Uncompromised Performance. Unprecedented Value PAGE 6
Test Steps for Analyzers without the Rigol VSWR-DS800 option installed 1. Clean all connectors with a lint free swab and electronics contact cleaner. Make sure to remove any contamination, dirt, or metallic flakes in and around mating surfaces. 2. Connect the Rigol VB1000 series VSWR bridge or other directional coupler to the DSA. The Rigol VB1000 series can be attached to the analyzer as shown below: If you are using another direction coupler or bridge, please see the connection instructions for the specific model you are using to ensure proper connections. NOTE: Leave the DUT connection of the coupler open at this time. This will provide 100% reflection and be used to minimize the effects of the cabling, adapters, and coupler. 3. Configure the DSA frequency span for the DUT by pressing the FREQ key on the DSA display and setting the Start and Stop frequency. RIGOL – Uncompromised Performance. Unprecedented Value PAGE 7
Press FREQ Start Freq Use Keypad or scroll wheel to enter start frequency and select units. Press FREQ Stop Freq Use Keypad or scroll wheel to enter stop frequency and select units. 4. Set the tracking generator output amplitude level to a value that is appropriate for your DUT Press TG set TG level RIGOL – Uncompromised Performance. Unprecedented Value PAGE 8
5. Enable the tracking generator. This will begin sourcing an RF source that will sweep from the start frequency to the stop frequency Press TG TG On 6. Open the Normalize menu Press TG Normalize RIGOL – Uncompromised Performance. Unprecedented Value PAGE 9
7. Store the open calibration (no DUT connected Full reflection) trace Press Stor Ref Normalize ON The trace should now be a flat line at the top (0dBm) of the display. This indicates that any reflections and losses are “normalized” and removed from the trace. NOTE: You can also view the normalized reference trace (Light Blue trace) by setting Ref Trace View. RIGOL – Uncompromised Performance. Unprecedented Value PAGE 10
8. Connect the DUT of interest to the coupler input (IN). Now, parts of the trace should drop below 0dBm. 9. Select a marker to identify your location on the trace. Press Marker Normal 10. You can use the scroll wheel to manually mark the minimum, activate the marker table, or you can use the Peak Minimum function to find the lowest spot on the trace automatically. Press Peak Min Search RIGOL – Uncompromised Performance. Unprecedented Value PAGE 11
The minimum value displayed on the DSA is the return loss of the DUT. Record this value in dB. The VSWR can be calculated by the following: a Return Loss (dB) r Reflection coefficient of the DUT s VSWR r 10 (-0.05 * a) s (1 r ) / (1- r ) Find more information online DSA800 Family Information page For more information on our spectrum analyzers or other products please go to rigolna.com or contact us directly at applications@rigoltech.com or call us toll free at 877-4-RIGOL-1. Rigol Technologies USA 10200 SW Allen Blvd, Suite C Beaverton, OR 97005 877.474.4651 RIGOL – Uncompromised Performance. Unprecedented Value PAGE 12
The VSWR can be used to judge the quality of impedance matching for cables and other passive devices. It is also mainly used to determine the efficiency of antennas to radiate power. A perfectly matched antenna/cable system will have a VSWR 1. In reality, VSWR's are typically in the 1.1 to 1.2 range.
VSWR at the Input of a Lossy Line Because of the losses in a transmission line,! the measured VSWR at the input of the line is! less than the VSWR measured at the load end of ! the line. VSWR Input a ρ a ρ Example 250 feet of RG-8X @ 30 MHz (ML 2.0 dB x 2.5 5.0 dB) with a VSWR at the load of 6:1 ρ 0.71 a 3.16 VSWR Input 1.58
Antenna Noise Bridge from Palomar, MFJ, or from plans in the ARRL Handbook Spectrum analyzer with a tracking generator and an external directional coupler or RF bridge . MFJ-269t. MFJ-202Bt. 23. Measuring VSWR. Directional Couplers RF Bridges. 24. Measuring VSWR. VSWR can be measured using a VSWR meter or directional watt
VSWR mobilefish.com In an ideal situation when no power is reflected back, (Z L Z S) the VSWR 1.0 or as commonly expressed as a ratio of 1:1. The higher the impedance mismatch, the higher the VSWR value. If Z S Z L than power is reflected back, for example VSWR 1.4 or 1.4:1. An antenna with a VSWR 1.4 is considered to be an excellent .
of your transmit signal going to the antenna and the amount of signal reflected back by the antenna. A VSWR meter measure P out, P reflected and VSWR. How are there related ? The best VSWR is 1:1. This means that 100% of the signal is going to the load (0% reflected) At VSWR 2:1, 11% of the power is reflected
VSWR Measurement in 75 Systems Using the R&S FSH3-TV TV Analyzer Application Note The voltage standing wave ratio (VSWR) is one of the parameters in RF systems that measures the impedance mismatch. Under ideal conditions, when the load is perfectly matched to the source, the VSWR will be 1. A mismatch in the system causes reflections that will .
to 100 ohm, the VSWR is equal to 2 as shown by simula- tion at . Figure 2(b), and for a load 200 ohm the VSWR goes to 4. This confirms that when the load changes and it differs from the line's characteristic impedance . Z. 0, VSWR also changes because of reflected waves [7,8]. The second scenario, as in . Figure 3, considers a gate-
- VSWR of 1:1 is obtained when the load is perfectly matched to source impedance VSWR Measurement Principles: As shown in Figure 2 the reflection properties of Circulator can be described by S-parameters. An RF vector network analyzer (VNA) can be used to measure the reflection coeffici
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