- VSWR = (1 + √ PRFL/PFWD) / (1 - √ PRFL/PFWD
- Online SWR Calculator From Forward and Reflected Power All our transmitters above 30W feature a simple Forward and Reflected power meter on the front panel. You can take the readings from this meter, place the readings measured in watts in the boxes below. Click Calculate and up will pop the answer directly in SW
- e equivalent values

Here's a simple VSWR calculator. Enter a value for VSWR (remember: VSWR should be a number larger than 1.0 or the results don't mean anything!). Enter VSWR: Calculate! Reflection Coefficient . Reflected Power (%) Reflected Power (dB) Mismatch Loss (dB) Where do these calculations come from? Well, start with the formula for VSWR: If we invert this formula, we can calculate the reflection. This RF calculator has been developed by Compliance Engineering as a resource for individuals involved in EMC and RF compliance measurements. The following table provides conversions for wavelength (from frequency), VSWR (from forward and reflected power) and various other useful conversions. Try our other EMC related calculator pages The **VSWR** definition states that the **VSWR** is equal to the maximum voltage on the line divided by the minimum voltage. The voltage fluctuations come about as a result of the voltage components from the **forward** **power** and the **reflected** **power** summing together. The sum voltages on a line that arise due to the standing waves **VSWR** = V max V mi This VSWR calculator will calculate return loss, mismatch loss, loss in percentage and the reflection coefficient. As an added bonus, the results are modifiable and can calculate the other values. VSWR (Voltage Standing Wave Ratio) is the measure of how efficiently RF power is transmitted and is expressed as a ratio of the maximum to minimum amplitude (or the voltage or current) of the.

Engineers use the reflection coeffcient to determine how much of the signal propagating on a line is reflected back to the source. Return loss is the measure of how much of the signal is lost when it is reflected back to the source, while matching loss is the loss incurred when there is a great mismatch between the line and the load. This calculator computes the VSWR, reflection coefficient. VSWR from Forward and Reverse Power. Radiated Magnetic Field from a Loop Antenna (Low Frequency, Close Proximity) Power Density & Field Level(Far Field) Power to Generate a Known Field(Far Field) Circular Waveguide Attenuation. Gain from Antenna Factor (50 Ω system) Radiated Power Conversions. EIRP (mW) EIRP (dBm) ERP (mW) ERP (dBm) dBuV/m at 3m. dBuV/m at 10m. Field Strength Conversions. V/m. Calculate VSWR, Return Loss, Reflection Coefficient, Match Efficiency, and Net Transmission Loss from an RF broadcast transmitters forward and reflected power readings. Free online calculators * VSWR to return loss conversion Convert VSWR This is an online conversion tool for converting between VSWR, return loss and reflection coefficient, which are different ways to express how well a load is matched to a source*.These parameters are often applied to antennas, RF filters and RF amplifiers such as LNAs and PAs. Return loss can be measured by using microwave and RF test.

calculate VSWR. Here are some formulae for determining Reflection Coefficient ( Ψ): ρ = i r E E Where Er = reflected voltage, Ei = incident voltage ρ = 1 2 1 2 Z Z Z -Z + Where Z1 and Z2 are the mismatched impedances in ohms ρ = fwd ref P P Where P ref = reverse power, P fwd = forward power Once the reflection coefficient has been calculated, it can be used to determine VSWR by the. (VSWR) Loss Calculator This calculator requires the use of Javascript enabled and capable browsers. 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. The calculator is designed to be fine tuned after the initial input ** The ratio of a sinusoidal signal reflected back from the load to the forward signal absorbed by the load in dB is called return loss**. The term 'forward power is synonymous with powered deliver to the load, or thru power. Thus with ~ 25% reflected power: u001au001a Return Loss = -10 x Log [ 74.88/25.12] = 6 d Enter the value for VSWR in the below calculator to find out the values for Reflection Co-efficient, Reflected Power in % and Return loss in dB and the mismatch loss in dB. Enter VSWR value other than 1 or 0 VSWR Calculator Calculates VSWR from forward and reflected power

The reflected waves are the waves (currents) that are returning to the transceiver due to a mismatch (antenna not being 50-ohms Z). The ratio of the forward vs. the reflected power is called VSWR or SWR. This ratio is calculated by comparing the forward to the reflected waves. A meter will display this reflected power as SWR on the readout This is because reflected voltage from the short circuit is almost equal to the forward voltage. Refer Reflection Coefficient vs Return Loss vs VSWR to know about their relationship. Following equation or formula is used for VSWR to return loss converter and viceversa. Useful converters and calculators 215 Vineyard Court, Morgan Hill, CA 95037 | Ph: 408.778.4200 | Fax 408.778.4300 | info@markimicrowave.com 1‐ Reflected Power (%) = 100 * The forward and reflected power measured by directional couplers can be used to calculate SWR. The computations can be done mathematically in analog or digital form or by using graphical methods built into the meter as an additional scale or by reading from the crossing point between two needles on the same meter. The above measuring instruments can be used in line that is, the full power of. 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.In one typical RF application, VSWR is used to measure the amount of reflection due to impedance mismatch. **Note: All of our calculators allow SI prefix input

By making both forward and reflected power measurements, you can calculate the SWR with the following equation: I suggested that they make these measurements with a Bird 43 wattmeter , with the appropriate plug-in. Bird even has an application note, VSWR Measurements Using In-Line Power Meters on how to do this * The VSWR can be calculated with the reflection coefficient or with the forward power and the reflected power*. The reflection coefficient describes the power that is reflected from the antenna. The VSWR can be used to calculate the return loss and mismatch loss

VSWR Calculator Calculates VSWR from forward and reflected power. Enter Forward Power: watts Enter Reflected Power: watts VSWR = (1 + √ P RFL /P. 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. The calculator is designed to be fine tuned after the initial input. With the initial. A VSWR of 2:1 means that with 10,000 watts transmitted, about 1,111 watts is reflected back towards the transmitter. If 100 percent of the transmitted power is reflected, the VSWR is infinity. Return loss is another term used to describe the amount of power being reflected from the load. Return loss is expressed in terms of dB

* The reflected power forms a voltage wave that travels back on the line until reaching the generator*. This wave is seen as a voltage generator was added at the feed point (picture B). If we calculate the V2 voltage and I2 current we shall see that, due to the contribution of V load, they will not match I1 and V1 anymore. The generator will see a new impedance value Z2=V2/I2, this time not. The voltage standing wave ratio (VSWR) is defined. VSWR is a measure of the reflected power on a transmission line. VSWR is a function of the characteristic impedance of the transmission line and the impedance of the antenna. VSWR specs (specifications) are introduced, along with formulas for mismatch loss and return loss in relationship to VSWR

The minimum and maximum voltages are converted back to power values that then are used to calculate minimum and maximum values of VSWR and return loss. VSWR and Return Loss VSWR and return loss both are complex ratios of forward and reflected power. Rho, also a ratio of these powers, often is used as an interim step in computing VSWR. For example, with a forward power of 100 W and reflected. value will be ( 1 - r ). SWR, or more correctly VSWR, and they are related by the expression: VSWR = 1+ 1− However, it is not easy to see from this how to calculate the SWR from measured values of forward and reflected power. It must be remembered that the forward power, W F and reflected power, W R, are, of course, measured i Power measurements: Transmitter power output into nominal load (W): Forward power (W): Other measurements / estimates / details: VSWR calculator help. RF Transmission Line Loss Calculator. RF Two Wire Transmission Line Loss Calculator. VSWR nomographs (PDF - you need Acrobat Reader) Other tools. V1.02. Use at your own risk, not warranted for any purpose. Do not depend on any results. To use this calculator, enter one of the following data: the voltage standing waves ratio VSWR, the return loss RL, the reflection coefficient ρ, the power ratio ρ 2, the forward and reflected power P fwd and P ref; or the impedances Z c and Z l. Then click the Calculate button next to the value you just typed to compute the others Calculate VSWR from Forward and Reflected power. GitHub Gist: instantly share code, notes, and snippets

- VSWR Voltage Standing Wave Ratio Calculator. Converts VSWR into dBm. VSWR :1 : Input Power [dBm] [W] Reflection Coefficient : Mismatch Loss [dB] Return Loss [dB] Reflected Power [dBm] [W] Output Power [dBm] [W] Share your thoughts. Nothing more to be seen below this point ? Maybe your browser blocks the facebook iframe. The webmaster does not read the comments regularly. Urgent questions shou
- Reflected Power Calculated from VSWR and Forward Power. Description Data Entry; VSWR: Fowrard Power: Reflected Power: Calculate
- Return Loss and Mismatch Loss Calculator Calculates the absolute load impedance, reflection coefficient, VSWR, return loss and mismatch loss of a load. Enter the source characteristic impedance and the load impedance then press Calculate below. This calculator uses JavaScript and will function in most modern browsers

Can someone refresh my memory on calculating VSWR from forward and reflected power? Just helped someone with some transmitter problems and had 15w reflected, 30w forward out of a 50w transmitter. Fixed the antenna and got 48ish Watts forward and 1 reflected. C. cabletech Member. Joined Apr 22, 2012 Messages 871 Location Puget Sound. Oct 31, 2012 #2 What type of radio & frrequency? What type of. These forward and reflected waves interfere with each other to produce standing waves along the transmission line. By looking at the maximum and minimum voltage amplitude of the standing wave, we can calculate the VSWR. Reflected power is not desirable as ideally all power from the transmitter should be absorbed by the load There are many ways in which the reflection coefficient can be calculated. Using the basic definition of the reflection coefficient, it can be calculated from a knowledge of the incident and reflected voltages. Voltages used for calculating the reflection coefficient Γ = V ref V fw are not real energy flows, but rather are calculated figures which represent the power that would be generated in a 50 Ω resistor if the forward and reflected waves were impressed upon it. Since there is no such resistor, there is no such power. Let's recap. What can be inferred from the forward and reflected power readings on our directional wattmeter and what cannot? 1. If the reflected. called the forward wave. In some cases, part of the voltage is reflected at the antenna and propagates back down the line in the reverse direction toward the transmitter, much like a voice echoing off a distant cliff. SWR is a measure of what is happening to the forward and reverse voltage waveforms and how they compare in size. Let's look at what happens when a trans-mitter is connected to.

The calculator converts between return-loss, VSWR, reflection coefficient, and mismatch loss. It also shows the percentage of forward to reflected power. Particularly, reflected power and mismatch loss help describe the need for the antenna (with its matching network) to provide a suitable return loss to the active electronics VSWR Calculator * Enter VSWR*, Reflection Coefficient, or Return Loss to calculate remaining values VSWR Just in case you don't care for mathematical equations, here's a little cheat sheet table to help understand the correlation of VSWR to the percentage of reflected power that will return. NOTES Here is a download of this cheat sheet: VSWR vs. Return Loss An article that explains VSWR This online VSWR Calculator is also very usefu The output power can be calculated by subtracting Mismatch Loss (in dB) from Input Power (dBm) to give output power (dBm

* The minimum VSWR is 1*.0. In this case, no power is reflected from the antenna, which is ideal. 3. How is VSWR calculated? The VSWR definition states that the VSWR is equal to the maximum voltage on the line divided by the minimum voltage. The voltage fluctuations come about as a result of the voltage components from the forward power and the. Enter Forward Power in Watts. Enter Reflected Power in Watts. This program is provided as-is. It is thought to be accurate but it is the responsibility of the user to verify the accuracy of the calculations when using this program in any official capacity or for the completion of any FCC forms or reports. Return to Home Page.

- In the FWD position the meter indicates the forward power traveling on the antenna cable, this is the power going from the transmitter to the antenna. In the REF position the meter indicates the reflected power traveling on the antenna cable, this is the power that has not been absorbed by the antenna returning back to the transmitter. To make an SWR reading the transmitter is switched on, the.
- Enter the value for VSWR in the below calculator to find out the values for Reflection Co-efficient, Reflected Power in % and Return loss in dB and the mismatch loss in dB. Enter VSWR value other than 1 or 0. The negative values in the mismatch loss field indicates the loss of signals. Code to add this calci to your websit
- es loss of forwarded radiation due to returned power Note that the loss can be compensated by high power #Damage the transmitter ! VSWR results from mismatched impedance ! To calculate the VSWR, first calculate the reflection coefficient: ! VWSR is represented as VWSR:1; e.g., 3:1 assu
- Optimal Mitre calculator Path loss calculator Phase Noise to Jitter converter PLL PFD Frequency calculator PLL loop filter calculator Potential divider calculator Propagation time calculator Gamma to Impedance converter Reactance calculator SFDR calculator Skin depth calculator Stripline Impedance calculator Smith charts VSWR/Return loss converte

reflection coefficient Calculator: The reflection coefficient is the ratio of reflected wave to incident wave at point of reflection. This value varies from -1 (for short load) to +1 (for open load), and becomes 0 for matched impedance load Voltage Standing Wave Radio (VSWR) o Determines loss of forwarded radiation due to returned power . n Note that the loss can be compensated by high power Damage the transmitter . o VSWR results from mismatched impedance o To calculate the VSWR, first calculate the reflection coefficient

- VSWR Calculator. Measured Forward Power: Watts: Measured Reflected Power: Watts: Cable Type: Frequency: MHz: Cable Length: metres: Cable Loss = dB: Measured VSWR = ratio: RL dB: VSWR at antenna = ratio: RL dB: Power into/at antenna = watts: Power reflected from/at antenna = watts: Notes: Maximum Power rating for RG213 cable is 250 watts taking into account environmental de-rating. The limit of.
- How To Calculate Dissipated & Reflected Powers Reflection coefficient = r = = = 0.5 V S 50 100 W Transmitter 150 Load (Antenna) P FORWARD 141 V RMS 150R L-50 R L +50 •With a 150 ohm load at the end of a 50 ohm lossless transmission : Reflected power = r2 x P FORWARD = 0.25 X P FORWARD-50 150+50 Power transferred to the antenna= (1-r2) x P FORWARD = 0.75 X P FORWARD P REFLECTED P OUT P.
- VSWR calculated as 3.12:1. (Note: the dashboard no longer looks exactly like this — see photo posted in 11/24/18 update above for the latest version.) The system monitors and will remotely display forward RF power, reflected RF power, SWR/VSWR, and the heatsink temperature. I am considering adding monitoring of the key line. The purpose of doing that would be to be able to remotely.

The forward (or incident) signal mixes with the reverse (or reflected) signal to cause a voltage standing wave pattern on the transmission line. The ratio of the maximum to minimum voltage is known as VSWR, or Voltage Standing Wave Ratio. A VSWR of 1:1 means that there is no power being reflected back to the source continuously measure forward and reflected power and calculate actual VSWR. They are designed for use in ana-log and digital systems and employ low-loss, high-directivity couplers in conjunction with high- sensitivity detectors and built-in microprocessors. An LCD display allows direct viewing of forward power, re-flected power, and VSWR. An RS485 bus is provided for remote control and. Reflected power and VSWR Metering. A Front-panel view of my FT-817. SPOILER ALERT: The SWR indication on the FT-817 - and many other HF radios - cannot and should not be directly correlated with VSWR readings, but like the power output meter it is a relative indicator of the antenna match that the radio is experiencing. The number of bars (or dots) on the display cannot readily be.

Sometimes **VSWR** is called SWR to avoid using the term voltage and to instead use the concept of **power** waves. This in turn leads to a mathematical definition of **VSWR** in terms of a reflection coefficient. A reflection coefficient is defined as the ratio of **reflected** wave to incident wave at a reference plane. This value varies from -1 (for a shorted load) to +1 (for an open load), and becomes 0. Reflected Reflected Power 5 6 7 +-4 1K 12 13 14 1.1K +13.5 VDC +8 VDC 1 uF To +4 VDC Foldback Treshold 7808 390 ½ W SWR LED Radio Shack 276-0017 100K Forward 100K + 10K-3 1.21M 10 9 8 1 uF 1.0 uF Latch Relay1 +12 VDC 100 17 mA 1 16 +-Latch Relay1 13 8 6 9 4 11 0.1 uF To SWR Shutdown 5.1K Reset To +8 VDC 5.1K 2N3501 2N3501 2N3501 1N3600 2N3501. Pasternack's VSWR/Return Loss Calculator will find VSWR, Return Loss, Mismatch Loss, and the Reflection Coefficient given any one of the listed input types The power reflected back from an antenna is specified using either the voltage standing wave ratio (VSWR) or the reflection coefficient (also referred to as return loss). Poor VSWR can cause shadowing in a TV broadcast system as the signal reflected off the antenna reflects again off the power amplifier and is then rebroadcast. In wireless communications systems, shadowing will produce multi.

Due to mismatches in impedance within the connector, some of the signal is reflected. The ratio of the input to the reflected signal is called the Voltage Standing Wave Ratio (VSWR). This ratio can also be measured in dB, and expressed as Return Loss Reflected Power Measurement The challenge in reflected power measurements is that the coupler must distinguish between a high forward power signal and a much lower reflected power signal (Fig. 3b). In contrast to forward power measurements, a smaller reflected power will require more directivity to achieve the same measurement certainty. If the incident power and the reflected power are expressed in 'absolute' decibel units, (e.g., dBm), then the return loss in dB can be calculated as the difference between the incident power P i (in absolute decibel units) and the reflected power P r (also in absolute decibel units), = () Optical. In optics (particularly in fiberoptics) a loss that takes place at discontinuities of refractive.

- Forward power in watts: PREFLECTED = Reflected power in watts: P%REFLECTED = Reflected power percentage of the forward power in percent . Convert Forward And Reflected Power to VSWR: VSWR = (1 + SQRT(PREFLECTED / PFORWARD)) / (1 - SQRT(PREFLECTED / PFORWARD)) Convert VSWR to Reflected Power percentage : P%REFLECTED = (VSWR - 1)² / (VSWR + 1)² ´ 100. By you entering the website, you must.
- VSWR Mismatch Errors: Both amplitude and phase errors are introduced when mismatched impedances are present at an electrical interface. 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. Upon arriving back at the source, part of the reflected wave is coupled back to the source and the rest is.
- g signal to the same reflected signal.

SWR (Standing Wave Ratio) affects the power output of your radio. The following table shows the effect of SWR for a transmitter with 4 watts of transmitted power. The formula: Power in Watts x ((SWR-1) x (SWR-1)) В ((SWR+1) x (SWR+1)) = Loss of Power in Watts * ERP = Percentage of Effective Radiated Power This tutorial defines VSWR and explains how it is calculated. Finally, an antenna VSWR monitoring system is shown. A similar version of this article appeared in the October 2012 issue of Power Systems Design magazine. VSWR Definition . Voltage standing wave ratio (VSWR) is defined as the ratio between transmitted and reflected voltage standing waves in a radio frequency (RF) electrical.

The forward and reflected power measured by directional couplers can be used to calculate SWR. The computations can be done mathematically in analog or digital form or by using graphical methods built into the meter as an additional scale or by reading from the crossing point between two needles on the same meter Specifically, a directional coupler measures forward and reflected power as well as VSWR and return loss. It is also a key component in power meters, antenna monitors and analyzers. The directional coupler works by providing two samples of the quantities in the transmission line. One sample is derived from coupling to the electric field in the line, where the other sample is derived from. The return loss then is simply the forward power minus the reverse power measured. With older spectrum analyzers without trace math the easiest way to get a quick, reasonably accurate measurement across the frequency band set up is shown in the diagram below. To calibrate, connect reflected path of the coupler to the spectrum analyzer and terminate the coupler output with a calkit short. Reflected power will be coupled into the the frequency-sensitive nature of the VSWR pattern between the direct and reflected signals will affect the apparent amplitude versus frequency response of the system. Using Equation (15.10), the peak-to-peak change in amplitude response can be calculated to be (15.13) ripple (dB -pk) = 20log [(1 + 10-R / 20) (1-10-R / 20)] This ripple will occur at. simultaneously monitors forward and reflected power on up to four transmission lines and continuously updates Voltage Standing Wave Ratio (VSWR) calculations. The Plus-X VSWR takes immediate action to interrupt transmitter RF output if a user-defined threshold is exceeded for either reflected power or VSWR depending on which parameter the user prioritizes for setting a fault. Plus-X VSWR can.

If the forward power of 40dBm and the reverse power of 20dBm are known, then we can calculate the return loss. It is 20dB. If the output power of the base station is known to be 20W and the return loss is 16dB, then we can calculate that the reflected power is 0.5W. Usually, we take 16-24dB as a measure of return loss Measuring forward and reflected power in an RF signal chain. Directional couplers have the valuable characteristic of directivity—that is, the ability to distinguish between incident and reflected RF power. As the incident RF signal travels through the forward path coupler on its way to the load (Figure 2), a small proportion of the RF power (usually a signal that is 10 dB to 20 dB lower. If the forward and reflected wave coincide, the vector sum (the amplitude of the resultant wave) is effectively double the height of either of them. An excellent animation of the vector sum of forwarding and reflected waves can be found here. The most commonly used SWR measurement is Voltage SWR or VSWR Hello, I am trying to understand how this program calculates forward and reflected power. At least I understand that VSWR ratio is calculated this way = (Vforward + Vreflectef) / (Vforward - DIRECTIVITY ERROR FIRST ORDER APPROXIMATION 1.1 VSWR Coupler Directivity 30 dB Forward Power 20 kW Reflected Power (Expected) 45.3 W Max Reflected Power 65.3 W Min Reflected Power 25.3 W Max VSWR 1.12 Min VSWR 1.07 Table 2 While the above discussion will serve well as a first order approximation, it is important to understand that the samples of energy collected by a directional coupler will.

So the reflected power at the meter is now 12dB less than the forward power. OK so the SWR of a 12 dB return loss can be worked out from this: Where the power ratio of 12 dB is Log(12/10) or 0.079, so we get 1 + (square root of 0.079) divided by 1 - (square root of 0.079) which is 1.67 VSWR & SWR - what's the difference ? calculate the value of current since I = V / Z. Measuring Forward & Reflected Power Measurement of RF power flowing in a coaxial transmission line is performed with an item known as a Directional Coupler. In amateur circles this is normally known as a SWR Meter. Lab grade Narda microwave Directional Coupler. 1 to 12.4 GHz Bruene Bridge SWR meter. Determine how to calculate the effect of VSWR on Return Loss. Understand the applications for the equation of VSWR on return loss in electronics . 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. Transmission lines often contain two different conductors to optimize.

REFLECTED power reading is that amount of power which was not initially absorbed by the antenna and has been sent back down the feedline. At the transmitter end it encounters the transmitter output circuitry and is re-reflected back towards the antenna. This happens because you do, in fact, have a VSWR greater than 1:1 as seen by the. Swr And Reflection Coefficient : Return Loss Calculator Mismatch Loss Vswr Northeast Rf - Sometimes vswr is called swr to avoid using t.. The common notion that 'forward power'=Vf^2/Zo and 'reflected power'=(ρ*Vf)^2/Zo where Zo is assumed to be purely real is an approximation that is invalid when Xo≠0 as in the lossy line cases above. Any argument about conservation of energy based invalid assumptions is itself invalid. Summary. It is possible to have ρ>1. VSWR calculated from ρ is singular where ρ=1, and will.

The table converts between return-loss, VSWR, reflection coefficient, and mismatch loss.It also shows the percentage of forward to reflected power.Particularly, reflected power and mismatch loss help describe the need for the antenna (with its matching network) to present a suitable return-loss to the active electronics Site VSWR (S VSWR) Measurements. Site Voltage Standing-Wave Ratio (S VSWR. VSWR is a ratio that measures the voltage variances between forward and reflected power. VSWR is the ratio of the peak amplitude of a standing wave to the minimum amplitude of a standing wave, as seen in this picture. In a nutshell, there are many reasons why VSWR should be paid attention to on a wireless transmitter site. Some of them are: VSWR is a good measure of the overall health of the. Since the reflected power will always be less than or equal to the incident power on the antenna, (OUTP-OUTN) will always be positive. VSWR is calculated using the equation . VSWR = (10 (RL/20) +1)/ (10 (RL/20)-1) Let's consider an example. During calibration, we first apply two equal input powers. This yields a differential output voltage of. Im trying to use ad8302 for vswr measurement along with a dual bidirectional coupler. Ad8302 is basically a logarithmic detector which would amplify the difference between two inputs. The incident and reflected power is coupled using a directional coupler and given to ad8302.Here one input (incident power coupled)is constant and other (reflected power , coupled) is varying according to load