The path loss that might be measured in a system however will not be this. A match is good if the return loss is high. The lowest value of the return loss and VSWR are found as -57. Calculate VSWR, Return Loss, etc. e. 6m RG-58C/U to vertical. Insertion loss is the amount of energy that a signal loses as it travels along a cable link. It's assumed that the source impedance is also complex. 5. This mix of web-based tools and downloadable Windows software was developed to help engineers design faster and more accurately. Step 4. Impedance Mismatch Calculator; VSWR from Forward and Reflected Power; Return Loss to VSWRVSWR Calculator. Poor VSWR can cause shadowing in a TV broa1) VSWR Calculation. g. In some systems this is not a trivial amount and points to the need for components with low VSWR. Measure the magnitude of the wave voltages at the coupled and isolated ports. 2 times the minimum voltage along that line, if the line is at least one half wavelength long. When a transmitted wave hits a boundary such as the one between the lossless transmission line and load (Figure 1), some energy will be transmitted to the. Keep in mind that some calculators for RF have hard-coded units; if the label says (nF), for example, there. This calculator computes the matched line loss for a transmission line using a model calibrated from data for the transmission line supplied to the calculator. In order to improve the VSWR, this calculator also has an extra input for adding an attenuator to improve or reduce the system VSWR. There is a mathematical equation to accurately calculate the VSWR of an RF system. 3% of the power back towards the transmitter. For example, a VSWR of 1. These calculators and. This calculator allows you to calculate the input impedance of a transmission line, as well as the VSWR, return loss, and mismatch loss at the input point. So a return loss of 20dB indicates a reasonably good match. Forward Power vs Return Loss Calculator RF calculators and converters. The formula and equations used by this calculator are also provided. Link Budget Calculator Determine the received signal strength (in dBm) given a systems amplifier gains, antenna gains and space loss. Yes, we did that without a calculator. from Forward and Reflected Power: Transmitter Forward Power : Watts: System Reflected Power : Watts: VSWR = Reflection Coefficient = Return Loss = dB: Match Efficiency = % Net. Note: The calculations for Total P1dB and NF use linear values. This is equal to a return loss of 14 dB or greater. 0 dB· Calculation of Free Space Path Loss and Link Budget · Calculation of T-Pad Attenuator and Stepper Motor · VSWR Return Loss and RMS Voltage calculations And that’s not all! Electronics Circuit Calculator is an all-encompassing color code calculator, a radio transmitter and a converter which offers a myriad of additional useful features. Antenna Downtilt and Coverage Calculator. This calculator converts between return loss (RL), voltage standing wave ration (VSWR), and reflection coefficient (Γ). 50:1, with a corresponding return loss of 3. VSWR Calculator The VSWR Calculator is a program for reflection unit conversion. The first one is a VSWR-to-Return Loss converter, where I input a number that every RF engineer and technician should have memorized for easy reference: 1. Because the reflection coefficient Γ < 1, then the return loss will have a positive dB value. 5:1 VSWR that appears on. 4. 954 dB actually represents a power gain. Alternatively, Generate R1 and R2 for a wanted attenuation. High return loss means low reflected power, so high return loss is good for a system. 1Here are some examples of the logarithmic scale, or loss in decibels: Return Loss & VSWR Table. com +1 (718) 934 4500 +1 (800) 654 7949. However, convention and some literature quote return loss as a negative value akin to an S (1,1) measurement on a Network. The VSWR is a measure of the efficiency of a transmission line and is used to determine how well the line is matched to the impedance of the. here is an online cascaded VSWR calculator using the RSS method. 4. Convert the load VSWR to load return loss per the following equation: RL Improved = 2*Attenuator + RL Load [dB] (where RL=Return Loss) Of course, the method can be reversed to predict the attenuator required to improve a load VSWR by a predetermined amount. To calculate the Return Loss, add 1 to the VSWR and divide the result by the VSWR minus 1. 707. 3. The Voltage Standing Wave Ratio (VSWR) is defined as the ratio of the maximum amplitude to the minimum magnitude of the voltage standing wave at an input port of an antenna. Now let's look at the response. Return loss is related to both standing wave ratio (SWR) and reflection coef-ficient (Γ). Antenna efficiency doesn't cover reflected power due. 0:1). VSWR Calculator. Power to Voltage. This VSWR calculator will calculate return loss, mismatch loss, loss in percentage and the reflection coefficient. For those that want to think in terms of VSWR, a 20 dB return loss is equivalent to about a 1. Where, RL = Return loss in dB. voltage standing wave ratio. 0. These multiple solutions are possible because each contributor is a vector having both. Effects of Cable Loss in VSWR and Return Loss Measurements By Jim Norton Bird Technologies Group Applications Engineer 1 | Bird Technologies Group 866. VSWR. The following table provides conversions for wavelength (from frequency), VSWR (from forward and reflected power). To use this calculator to determine the effective VSWR/Return Loss of an attenuator/device combination, enter the attenuation, VSWR or Return Loss, and Gain of the device, then press the ‘Calculate button’. Stripline Calculator. Return loss and VSWR are two important measures of efficient power transmission and both of them can be interconverted to obtain the value. Stage: NF (dB) Gain (dB)The voltage standing wave ratio (VSWR) is defined. In some systems this is not a trivial amount and points to the need for components with low VSWR. The Tee attenuator consists of one series resistor at the input and two parallel, one of which is grounded while the other goes to output. S22 would be the reflected power radio 2 is attempting to deliver to antenna 2. Lower VSWR means lower reflection power (good impedance matching); thus, power transfers to load will be high. The component is said to have a loss of 25 dB. Transmission Line Type : Transmission Line Length : A Forward and Reflected Power to VSWR Calculator is a tool that helps to determine the Voltage Standing Wave Ratio (VSWR) of a transmission line by using measurements of the forward and reflected power. Measure S11 across the desired frequency range. A high return loss is desirable and results in a lower insertion loss . ZoA return loss of -40 dB is 1. A 2-port device has two distinctly interesting. Return loss is a measure in dB of the ratio of power in the incident wave to that in the reflected wave, and we define it to have a negative value. LDF4-50A, HELIAX ® Low Density Foam Coaxial Cable, corrugated copper, 1/2 in, black PE jacket Halogen free jacketing non-fire-retardant (General propose cable for outdoor use only) Find a Partner. 3 dB. VSWR is a function of the characteristic impedance of the transmission line and the impedance of the antenna. Cable impedance ohm. These are the standard set of equations for converting between VSWR, return loss, and reflection coefficient (Γ). Example 2. Return loss (RL) is the ratio of the reflected power to the incident power, in decibels (dB). 0:1,. This fundamental concept determines S-parameters for multi-port networks, which calculate parameters such as return loss, VSWR, and insertion loss. This is an ideal situation that rarely, if ever, is seen. If the power incident on a load is Pi P i and the power reflected by the load is Pr P r, then the return loss in decibels is [1, 2] RLdB = 10 log Pi Pr (7. Definition of VSWR. Calculate Effective Radiated Power (ERP) With Known Transmission Variables: Transmitter Output Power : W or kW. Lower VSWR is always desirable for a system. From a certain perspective 'Return Loss' is a misnomer. The input to the antenna will be 8,511 watts. Return loss can be measured by using microwave and RF test equipment such as a signal generator,. These measurements can be viewed as VSWR or Return Loss with the Site Master. Then click the "Calculate" button next to the value you just typed to compute the others. 794 Both these parameters are used to find a match between a source and load of a system. In the real world, a VSWR of 1. ZoThus, for this system, VSWR = 1:1 (i. VSWR to Return Loss Formula VSWR = (1 + 10-RL/20)/ (1 - 10-RL/20) Example Calculation A Return. reflection coefficient definition. Converts dB into VSWR. coefficient of Port 1 (also called return loss), and. (1) ea Flex Assy - 1. RL = 20 * log10 ( (VSWR + 1) / (VSWR - 1)) RL = 20 ∗ log10( (V S W R + 1)/(V S W R − 1)) Variables: RL is the Return Loss (dB) VSWR is the Voltage Standing Wave Ratio. Waveguide Calculators. Related Posts. 40) a common limit for sweeps with an antenna at the far end. November 2023. 2. Learn about voltage standing wave ratio (VSWR), return loss, and mismatch loss, which helps characterize the wave reflections in a radio frequency (RF) design. 5), which will give us 6. 041:1 There is a large list of web based VSWR - return loss - reflection coefficient calculators available real-time via the here to go go to our main page on VSWR We offer an Excel spreadsheet that will help you visualize how voltage standing waves are created. Increasing return loss corresponds to lower SWR. Use the S11 value in the calculator above to find the equivalent VSWR. This is equivalent to VSWR 5. The VSWR Calculator is used extensively in RF engineering, telecommunications, and antenna design to optimize system performance, reduce signal loss, and prevent damage to RF equipment. 54-88 MHz -- Low VHF; 88-108 MHz -- FM;S11 then would be the reflected power radio 1 is trying to deliver to antenna 1. This VSWR calculator will calculate return loss, mismatch loss, loss in percentage and the reflection coefficient. A good VSWR to aim for is at least 1. In practice, the generally accepted frequency band limits for rectangular waveguide are between 125% and 189% of the lower cutoff frequency, in this case 8. RG-8 and RG-213 (50 ohm); and RG-11 (75 ohm) are about 0. Custom. 0:1 0 0 1. VSWR (voltage. 93 dB. An unfeasible VSWR of 50 reflects 92. Stripline Impedance calculator Smith charts VSWR/Return loss converter Wavelength calculator Wilkinson splitter designer. When you look at a graph of a return loss formula, the negative sign is often omitted and is sometimes used interchangeably with the S11 parameter. Calculates the resistor values, attenuation, minimum attenuation, impedance, reflection coefficient, VSWR and return loss of an impedance matching T attenuator. Return loss and insertion loss are both measurements of how a component or device affects the transmission of signals in a system. Click here to use the VSWR Calculator. , some amount of incident power will reflect the source in a practical system). Calculate VSWR, Return Loss, Reflection Coefficient, Match Efficiency, and Net Transmission Loss from an RF broadcast transmitters forward and reflected power readings. Now VSWR is 1. VSWR to Return Loss. The reflection coefficient is calculated from the VSWR and used to compute the mismatch loss in dB as shown below. 1 Return Loss. A low VSWR will minimize reflections from the antenna. Coupling to Direct Line Insertion Loss Conversion Table for Directional Couplers. Here Click here to learn more about VSWR. return loss (dB) (evaluated as neg. Skin Depth Calculator. Select operating frequency. The oscilloscope is a very powerful tool that has many functions. Unless you have a piece of slotted line-test equipment this is a hard definition to use, especially since the concept of voltage. In either case, the resulting VSWR is 1. Reflected Power. Mismatch Loss: Reflected Power Through Power (dB) Coefficient, Γ (dB) (%) (%) 1 17. Enter. 43 20. 00Watts Enter 1. Calculate! Where do these calculations come from? Well, start with the formula for VSWR: If we invert this formula, we can calculate the reflection coefficient (, or the return loss. Return loss vs. It varies from 1 to (plus) infinity and is always positive. com This calculator uses the following formulas for converting the values between the VSWR, return loss, reflection coefficient, and mismatch loss. everything RF has the big selection of get calculators for the RF and Microwave Industry. Same-day shipping if you order in the next hours!. Select operating frequency. VSWR Return Loss (dBm) VSWR Return Loss (dBm) VSWR Return Loss (dBm) VSWR. This general RF calculator provides path loss, VSWR and wavelength as well as conversions between many common measurements used in the wireless industry. Note, that in this conversion to return loss all phase information is lost. Các ứng dụng của VSWR: Các chức năng chính của VSWR : Truyền Antenna: Tỷ lệ sóng đứng điện áp (VSWR) là một chỉ báo về lượng không phù hợp giữa một ante nna và đường cấp dữ liệu kết nối với nó. Γ = (VSWR – 1)/(VSWR + 1) Return Loss (dB) = -20*Log 10 (|Γ|) Mismatch Loss (dB) = -10*Log 10 (1 – |Γ| 2) Conversion Tables. This calculator is specific to the circuit used in the RF Trap With Attenuators FLEXI-BOX. The online calculators are usable in pop-up mode for easy desktop. When creating PCB prototypes that conduct alternating current (AC) at radio frequency, designs must compensate for the effects of the current waves on the prototype material. SFDR Visualizer dB Path Loss with respect to dipole or isotropic antenna: Watts: dBw or dBm: microVolts: dBm: pforward (Watts) pref (Watts) Return Loss or a VSWR: return loss (dB) (evaluated as neg. 32 dB and 1. The VSWR is about 1. If VSWR is known, then the reflection coefficient (Γ), return loss (RL), and mismatch loss (ML) is calculated by using following formulas. Created Date: 10/21/2015 12:42:40 PM. RETURN RETURN RETURN RETURN RETURN LOSS VSWR LOSS VSWR LOSS VSWR LOSS VSWR LOSS VSWR (dB) (dB) (dB) (dB) (dB) return loss Vs. Like insertion loss, return loss is also generally described in decibels of power. You can assume power dissipation to be uniform, provided the assembly does not operate in high VSWR/return-loss conditions. 405 inch. This ratio represented in dB is called as Return Loss. RF Calculators. Load return Loss Var4. It is specified in decibels (dB) relative to a short circuit (100 percent rejection). 5:1 is considered ideal in the RF field, and. Calculates the resistor values, attenuation, minimum attenuation, 'impedance', reflection coefficient, VSWR and return loss of a matching Pi attenuator. In summary, return loss is the loss of signal power due to signal reflection or return by a discontinuity in a fiber-optic link or transmission line. This is an online calculator that calculates VSWR based on Reflection Coefficient. As an added bonus, the results are modifiable and can. If the antenna reflects 250 watts the VSWR at the antenna will be 1. 예를 들어 Return loss가 10dB 정도라면, VSWR은 2:1 이하가 되어서 입력매칭이 비교적 잘된 경우로 평가하며, Return loss가 14 dB 정도가 되면 VSWR은 1. This can be built into a FLEXI-BOX and a transmission line (50 Ohm track) PCB is available which easily adapts for this circuit with one simple trimming. VSWR Calculator. This online reflection coefficient to return loss calculator calculates the return loss (dB) by entering the reflection efficient Γ (= value. 01. VSWR is defined as the ratio of the maximum voltage to the minimum voltage in standing wave pattern along the length of a transmission line structure. Note: VSWR values were used to calculate the other two related values (rounded to 3 significant places). 50 from 6 votes. Here's a simple VSWR calculator. The following equation is especially useful when using a directional power meter. Enter values for R1 and R2 to calculate attenuator loss and impedance. 0:1, 2. Stripline Impedance calculator Smith charts VSWR/Return loss converter Wavelength calculator Wilkinson splitter designer. A01TKL_ RF Inductor by Coilcraft →. Figure 2: VSWR Measurement Principle The return loss at the input and output ports can be calculated from the respective reflection coefficients as follows: Input return loss (RL IN) is a scalar measure of how close the actual input impedance of the network is to theVSWR to Return Loss . ← Conducted RF Environments With Real RF Devices Vs. Pi Attenuator Calculator. For five t-line sections each having a VSWR of 1. SINAD to ENOB Calculator. Stripline Impedance calculator Smith charts VSWR/Return loss converter Wavelength calculator Wilkinson splitter designer. VTX Power in mW. Return Loss (dB) VSWR. B at a level of -32 dBm. VSWR: RL (dB) 1. Two wire line Two wire line calculator, Twin Lead cable: VSWR calculator v = 1 / √ E r (where E r is the diëlectric constant of the medium), for air E r is +/- 1: VSWR - return loss - reflection coefficient vonversions between VSWR - return loss - reflection coefficientVoltage Standing Wave Ratio (VSWR) is defined as the ratio of the maximum to the minimum voltage on a loss-less line. See the vswr table below to see a numerical mapping between reflected power, s11 and VSWR. Interactive Tools & Calculators. 1) RL dB = 10 log P i P r. VSWR is a measure of the reflected power on a transmission line. 0708,min,max = =VSWR Return Loss Calculator Find VSWR. Return Loss and Mismatch Loss Calculator. A high VSWR indicates poor transmission-line efficiency and reflected energy. 43 20. 0:1). Return Loss is the amount of power that is lost in the signal returned/reflected by a discontinuity in a transmission line. The reflection coefficient is also known as s11 or return loss. Reflection -3dB: half of the RF energy is being reflected, and thus half of the energy is being received by the device. VSWR / Return Loss Calculator: IRA Calculator: Wavelength (TEM) Calculator: Link Budget Calculator **Note: All of our radio frequency calculators allow SI prefix input. VSWR Return Loss Calculator. And S12 is the power from radio 2 that is delivered through. 0 or the results don't mean anything!). The return loss & VSWR is related by the following formula, from which we can calculate return loss for a given VSWR. VSWR (pronounced "viswar"), or the Voltage Standing Wave Ratio, is the ratio of the maximum standing wave amplitude at one node to the minimum amplitude at another node in a system. February 14, 2018 IZ2UUF Antenna 6. Balanced Attenuator Calculator. A calculator designed to compute the VSWR, reflection coefficient, return loss and matching loss in a transmission line T-Pad Attenuator Calculator This calculator helps you determine the values of the resistors R1 and R2 to be used for a T-pad attenuator. 1. Return loss can be converted to mismatch loss and the calculator also gives an intuitive sense of the impact by providing the forward and reflected power ; Related Posts. The table below converts between VSWR, return loss, reflection coefficient, mismatch loss, reflected power and through power. Return lossHome / Blog Posts / VSWR, Return Loss, Insertion/Transmission loss vs. 특히 Return loss와 VSWR의 대략적 값의 관계정도는 암기해두는게 편리할 때가 많다. VSWR Return Loss Calculator VSWR is the voltage standing wave ratio it used to measure the all-types waves (example: antenna waves) during transmission. Cable and antenna analyzers allow operators to measure return loss/VSWR, cable loss, distance-to-fault (DTF) measurements, reflection measurement, antenna isolation measurement, impedance, etc. For example, an antenna with a VSWR of 2:1 would have a reflection coefficient of 0. main article I used several examples of SWR based on a resistive load. It is the ratio between transmitted and reflected waves. This is an ideal open or short circuit, equivalent to VSWR=infinite. Cell Site Commissioning and Maintenance. The resonance calculator, based on user-supplied values of inductance (in nH) and capacitance (in pF), calculates a resonance frequency (in GHz) for the combination of electrical values. Stripline Impedance calculator Smith charts VSWR/Return loss converter Wavelength calculator Wilkinson splitter designer. In some systems. be used to add or subtract an arbitrary number of power, to convert power and voltage units from the linear to the logarithmic. An example of this would be a. A table of convenient values are presented at the bottom. When an ideal match is not encountered by the incident (forward) wave, part of it is coupled to the load and part is reflected back to the source. WhatsApp. 1) (2. Title:. Return loss is a meas-ure of how well devices or lines are matched. Marki Microwave's Tools is a collection of free online applications for RF analysis and synthesis that are easy to use and mobile-friendly. Given a certain level of heat generation within an assembly, thermal dissipation occurs through three primary mechanisms. Return Loss and Mismatch Loss Calculator Calculates the absolute load impedance, reflection coefficient, VSWR, return loss and mismatch loss of a load. Facebook. 7. In addition, the calculation takes into account the effect of signal attenuation in the transmission line. 54 dB (11% of your transmitter power is reflected back). Return loss (RL) is the ratio of the reflected power to the incident power, in decibels (dB). Step 1. As an example, F1=750 MHz and F2=850 MHz for a typical cellular frequency band. Many antenna specification sheets list the VSWR and some list the return loss, but many do not. 00Watts = 1. Assuming the systems have no internal loss. Stripline Impedance calculator Smith charts VSWR/Return loss converter Wavelength calculator Wilkinson splitter designer. These calculators help with unit conversions, VSWR calculations, attenuator design, antenna design, radars, and various other basic calculations that are often required. The return loss is the ratio of the power of the. VSWR to Return Loss. The return loss of a system is defined as the ratio of incident power to reflected power and is measured in dB. By entering the values given above into the VSWR calculator, we see that the probable assembly-chain VSWR of: 1. R/F Calculators and Conversion Tools VSWR / Return Loss Calculator Find VSWR (Voltage Standing Wave Ratio), Return Loss, Mismatch Loss, and the Reflection Coefficient given any one of the listed input types. The flexible types (9913F and LMR-400UF) are preferred, particularly for rotatable antennas. 79. Voltage standing wave ratio (VSWR), or often given as just standing wave ratio (SWR), is the ratio between the transmitted and reflected voltage standing waves at a signal chain element incident node. The VSWR value range from 1. VSWR, or the Voltage Standing Wave Ratio, is the ratio of the maximum standing wave amplitude at one node to the minimum amplitude at another node in a system. g. Upon arriving back at the source, part of the reflected wave is coupled back. w (mm) t (um) Er: h1 (mm) h2 (mm) Impedance: Notes: *Comparisons show minimal differences to ADS linecalc and Polar Instruments Quicksolver industry standard tools. Please Support RF Cafe by purchasing my ridiculously low−priced products, all of which I created. As it can be seen from the above equation, VSWR is always a real and positive number with a minimum value of 1. On the other hand, you calculate VSWR by using the maximum and minimum voltage levels of the standing wave pattern on a transmission line. 333, a mismatch loss of 0. 17. See the quick-reference table below for all compatible SI prefixes. A resistive load is the easiest to visualize, calculate and understand, but it’s not the most common type of. (GHz) Nut Attach Attach /Pin in (mm) in (mm) lb (g)The VSWR is about 1. Note: Equation 1 below uses linear power units (mW/W), while Equation 2 uses dBm/dBW. Reflected power ratio for system 1 is 0. Figure 6. VTX Power in mW. Frequency : MHz. The online calculators are usable in pop-up mode for easy desktop access and functionality. PI Attenuator Calculator. Assuming the systems have no internal loss. In this Inside Wireless episode we will look at Voltage Standing Wave Ratio (VSWR), |S11|, and Return Loss. 5. Noise Conversion Calculator. This calculator is designed to give the efficiency loss of a given antenna, based on the input of VSWR (voltage standing wave ratio) and other subsequent factors. Enter values for R1 and R2 to calculate attenuator loss and impedance. Directivity, on the other hand, is the level of the signal which appears at Port 4 and is undesired. Power handling may be limited by the connector choice. Mismatch can be specified as: the VSWR at the load end of. Đây còn được gọi. U. The calculator can be particularly useful when designing a system or testing worst-case impedance scenarios. The calculator is designed to be fine tuned after the initial input. There is also a selection of suitable connectors. For example, an antenna with a VSWR of 2:1 would have a reflection coefficient of 0. Add to My Products Lists. Loss factor. The voltage standing wave ratio (VSWR) is defined. There is an equivalent definition for VSWR, which can also be expressed in terms of the Return Loss (RL). The first-factor ohmic loss is an unavoidable loss as it is a property of. This impedance mismatch can be with a device inserted in the line or with the terminating load. If you don't want to go through complicated equations to understand the relationship between VSWR, mismatch loss, s11/gamma and would like a calculator to do it for you, check out our VSWR. As an added bonus, the results are modifiable and can calculate the other values. This ratio represented in dB is called as Return Loss. Then, take the logarithm base 10 of the result and multiply it by 20. The relationship between composite return loss and individual return loss in the constructive condition of identical mismatches is that the composite VSWR is the the square of the individual VSWRs. A power meter may also be used to calculate cable loss. 54dB. Author: yuuki. How to improve the Return Loss of an amplifier. RF power conversion (such as dBi and dBm to Watts), attenuation, frequency, wavelength, VSWR/return loss, torque,. The usual function of a transmission line is to convey power from a source to a load with minimal loss. The antenna accepts a certain amount of energy delivered to it by the transmission line (characterized by S11, VSWR, or return loss), and Antenna Efficiency characterizes the amount of energy lost ‘in’ the. Just enter an value and click calculate. Unused stages should be zeroed. 200mW. 19. But for a practical transmission system with load, there will be a small impedance mismatch that will lead to a small amount of incident power reflected back to the source. VSWR is defined as the maximum voltage of the standing wave (E max) to the minimum voltage of the standing wave (E min ). This is a measurement of how much energy is either radiated or is dissipated in heat, due to resistive or dielectric losses. 405 inch. 4) The reflection coefficient is calculated from the characteristic impedance of the transmission line and. Matching Pi Attenuator Calculator. 1060. so you need to calculate both. Conversion Formulas. I hope this adds to the knowledge of the. 예를 들어 Return loss가 10dB 정도라면, VSWR은 2:1 이하가 되어서 입력매칭이 비교적 잘된 경우로 평가하며, Return loss가 14 dB 정도가 되면 VSWR은 1. The table shows the effects of combining two components in terms of their maximum VSWR and return loss. directly calculate and display the resulting VSWR value. If you don't have Excel you can. This is the most efficient scenario. Enter Input Value Output. To help the engineers conducting VSWR sweeps, Lou developed the PIM and. Matching T Attenuator Calculator. VSWR is defined as the maximum voltage of the standing wave (E max) to the minimum voltage of the standing wave (E min ). 4569.