**Note: All of our calculators allow SI prefix input. Return loss vs. Further calculator information is available in About our calculators. Impedance matching is an important part of RF system design; however, there is always be some degree of mis-matchlossinpractice. The mismatch leads to the reverberation of waves within the transducer, heating, low signal-to-noise ratio, and signal distortion. The following formula relates the return loss and VSWR. Under common mode driving (same magnitude, same polarity), the even mode impedance is the impedance of one transmission line in the pair. The gain uncertainty arises due to impedance mismatch between the device and another connected device (e. I have done the impedance calculations to figure out the track geometry needed for 100 ohm differential impedance and confirmed it with the board house. Routing around obstacles and accommodating components and vias on a PCIe board is especially important. e. Speaker impedance is measured in speaker ohms (Ω). A mismatch occurs when the impedance of connected components or devices does not match the characteristic impedance of the transmission line or system. for matching 60 ohms to 50 (Z1/Z2=1. I always try to tune my pcb antennas in length, so they operate in resonance, by cutting the antenna with a scalpel and then matching the tuned antenna to the transmitter. In AC circuits, the source should either equal the load or the complex conjugate of the load, depending on the goal. The bulk wave velocity , also called longitudinal wave velocity in isotropic solids, is related to Young’s modulus and Poisson’s ratio. 7. Figure 4: T1 is a 2:1 impedance matching transformer in the input circuit of the power splitter/combiner. In a 50-ohm system, each output would be connected to a 50-ohm impedance, thus offering a 25-ohm impedance to the input port. Enter VSWR, Reflection Coefficient, or Return Loss to calculate remaining values. 01. The excess power (in order to prevent a violation of ohm's law) is reflected back up the cable to the battery. The following formula relates the return loss and VSWR. Getting the Most Accurate Impedance Calculations. AN1275: Impedance Matching Network Architectures Reflection Coefficient, VSWR, and Impedance Matching S-parameters for the impedance matching network shown above. This study demonstrates how the acoustic impedance mismatch (AIM) and the work function of components decouple the TE parameters to. In the 2-way mode, the calculator uses the impedance of. Rex Frobenius. If VSWR is known, then the reflection coefficient (Γ), return loss (RL), and mismatch loss (ML) is calculated by using following formulas. To be more clear, consider a simple RF circuit consisting of source and load connected via transmission lines. The impedance of metallic surfaces is approximately 2 Ω. This application note supplies a free of charge software tool that can e. 155 dB. This is more relevant to Tx because of the power levels involved. For a specified timing mismatch on one substrate, one might prefer to use an alternative substrate with a smaller dielectric constant, which would increase the allowed length mismatch. – Microstrip lines are either on the top or bottom layer of a PCB. 295+j32. ZO *. Zis known as an impedance. Time Domain Reflectometer (TDR) impedance measurements are essential for ensuring signal integrity in your design. This impedance mismatch can cause problems, especially for tube amplifiers that use output transformers. An impedance vector consists of a real part (resistance, R) and an imaginary part (reactance, X). The impedance mismatch in transmission lines is the root cause of most reflections and power losses. In fact, the apparent contradiction in the definitions of a reflection coefficient and conjugate matching in the maximum power transfer theorem arises due to the way in which wave propagation is defined in the original formulation of S-parameters. The amount of reflected signal from the load is dependent on the degree of mismatch between the source. In theory an O-pad is a balanced Pi-pad, however if I use a calculator I always get negative resistance values for R3. These include discontinuities in the physical path of transmission which reduce the quality of the signal; improperly terminated lines; and sudden step discontinuities in impedance lines. appropriate mismatch range that reduces the difficulty of preparing medium with gradient change of acoustic impedance. This is extremely important as we will see. The larger impedance mismatch produces larger reflection and affects the signal integrity. . Thus, the impedance looking into the common or input port would present a mismatch in a 50-ohm system. This calculator converts the SWR across an impedance mismatch to loss. For a single-stage quarter-wave transformer, the correct transformer impedance is the geometric mean between the impedances of the load and the source: Z T = (Z L *Z S )^0. g. 452, or -7 dB return loss), indicating some remaining mismatch. , the mismatch loss will be 0. This. Primarily an L-matching network was designed with two. ZP= ZS x (Turns Ratio)2. But in the end the calculation for real complex impedance has to be doneIn general, to measure an output impedance, you just connect a known impedance across it and measure the drop in voltage level. $ = Gamma^2 = 10^{-RL/10}$ Power transmitted ratio for system 1 is 0. Part 1. It seems like the case for me, however it does not explain how to calculate the resistances. Those pairs connect via a dedicated FFC cable. Length-tuning structures and their effects on impedance. Finally, the impedance mismatch should be as small as possible. Speaker wire size quick guide. • As shown in Figure 1, traces should be 100-Ω(±5%) differential impedance of differential microstrip or differential stripline. This calculator converts the SWR across an impedance mismatch to loss. Impedance is an important parameter to characterize electronic circuits, components, and materials used to make components. Clearly, the power reflected back from the antenna to the source should be minimized as far as possible. The image below shows an example of an interconnect interfacing with a CMOS component and driven with a source. HIGHPASS Hi-Low MATCHING NETWORK LOWPASS Hi-Low MATCHING NETWORK. , real) cable will always appear lower than the true SWR. In this situation, 10% of the incident power is reflected back to the source while the balance of 90% is transmitted forward. Abstract. — Advertise Here —. We shall find wide application for this concept when finding the appropriate load/source impedance for an amplifier to meet a given noise or gain specification. LC Bias Tee Calculator. Rematching the load will increase it further still. When the differential via pair is very short, its impedance will not matter; the input impedance at the via pair will be the input differential impedance from Pair 2. 3). VR V R and IR I R reflections have an impedance ratio of (exactly) 50 ohms hence, they are compatible to flow back up the 50 ohm cable to the source. e. We can calculate the common-mode input impedance pretty quickly using the equations in the above post. From where your field E is 105 10 5 microvolt per meter, or 0. 2 nH inductance at 6 GHz using microstrip line with characteristic impedance (50~Omega) and phase velocity (0. When I connect an oscilloscope to a function generator use both oscilloscope cable (one connect to the scope and one connect to the. Low impedance headphones (less than 50 ohms) will generally work fine on low voltage devices like. 2: Matching Network Design With Complex Impedances. An impedance mismatch arises when data is fetched from or inserted into a database. Its expression has been defined as follows: Because the impedances are complex numbers, the reflection coefficient will be a complex number as well. 5)2= 500Ω. H. For a VSWR of 1. The 75--50 ohm mismatch will cause VSWR, hence peaks and valleys of the RF energy. The excess power (in order to prevent a violation of ohm's law) is reflected back up the cable to the battery. As both these parameters are similar, they can be interconverted. Differential. The RF budget analysis measurements will be performed 0 to 0. If you can't remember in which order the numerator is subtracted (did we just say "Z L-Z 0" or Z 0-Z L "?), you can always figure it. Of these causes, impedance lines with sudden step discontinuities are most common. 21∠56. 1. If we substitute Γ 1 = Γ 2 = -0. 0:1. berkeley. You have to multiply by 50 to convert the normalized impedance into ohms (assuming your S parameters were measured on a 50 ohm network analyzer). That optimum power is 50% of the total power when the impedance of the amplifier is matched to that of the speaker. The Smith Chart graphically maps S11=reflection coefficient= (ZL-Z0)/ (ZL+Z0) to Load Impedance (ZL), normalized to Z0 (source impedance = center of chart). antenna) and the rest of the system, power from the transmitter flows to the antenna and a fraction of the power is reflected back towards the transmitter. A power sensor with a return loss of –23 dB is connected to a calibration source with a return loss of –20 dB. This bank of capacitors is an important part of the PDN impedance. The possible values of PLF are: Calculating PLF. Thus, speaker impedance is a speaker’s opposition to current flow. 13dB, again another almost perfect match to the measured values. The coupling of waves between the piezoelectric generators, detectors, and propagating media is challenging due to mismatch in the acoustic properties. Secondary turns, N S: 1000. Figure 3. Impedance mismatches result in standing waves along the transmission line,. The wave impedance of an electromagnetic wave is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right angles to the direction of propagation). Note that the load can be a complex (real and imaginary) impedance. Now we can find the effective gain of the cascade. the impedance mismatch, which should be minimum to satisfy the desirable maximum power transfer theorem. EIRP Calculator. ferent methods for calculating the input impedance of microstrip antenna. g. 6c). This means an electric filed intensity expressed in dB relative to 1μV/m 1 μ V / m (one microvolt per meter). Impedance mismatch. Now, if I understand it correctly line A if more positive than line B, then the reciever outputs a logic. The goal of the test is to measure the complexity of the overall platform and whether the complexity grows or shrinks as you add more features in the future. In order to properly get right cascaded S21 from the Sxx of each individual block you have to take into the impedance mismatch loss into account, which includes. You need to make sure the trace impedances are matched in each section, and that the input. Outside the impedance bandwidth, the antenna reflects the input power due to impedance mismatch and results in poor radiation. The calculator can also be used to find the value of VSWR using any of the other values. The reason for this approach is due to the behavior of real electrical signals on a transmission line. Calculate the electrical length of a 4 m cable in units of ?/4. Most RF systems are built around 50 Ω impedance. Solution: First the VSWR figures are converted to reflection coefficient magnitudes: Then the mismatch uncertainty is: M u = ±200 (0. As both these parameters are similar, they can be interconverted. 5 + 12. This is consistent with the peak-to-peak variation of the power curve in Figure 4. In electrical engineering, impedance matching is the practice of designing or adjusting the input impedance or output impedance of an electrical device for a desired value. 0:1, 2. If Z = 0 Z and ZL = ZG (for real GZ) we have a matched load, maximum available power goes into the load i. 590 -j36. A classic example of an impedance mismatched circuitWave impedance. 0004) relative to other body tissues. This is impedance matching, and the optimal value is R = R IN. The reference impedance can be any impedance even complex impedance though. Hence, I am employing the "squiggly line technique" to minimize the length mismatch of. It is likely that each device in the transmission line will exhibit some small deviation from the standard 50 Ω characteristic impedance, and the net effect is the aggregate of these cascading mismatches. Improperly connected cables or poor supply filtering schemes are often perfect conduits for interference. frequency can be reduced to a single metric using an Lp norm. In the pair with larger spacing (10 mil), a 21 mil amplitude length. The value of PLF at no polarization mismatch is equal to 1, 100%, or 0dB. Γ=(Z L-Z 0)/(Z L +Z 0). You can check it by yourself by either plotting the function R/ (R IN + R)2 with R IN = 1 or checking if its derivative is null for R = R IN (that is if you remember how to calculate a derivative). González Hernández, Ana I. It'll tell you what capacitors and inductors you need to create a passive crossover design for either two speakers (a 2-way passive crossover) or three speakers (a 3-way passive crossover). frequency for : 0402 (1 mF), 0603 (10 mF), and 0805 (100 mF) Above resonance 0402 and 0603 have same high-frequency asymptotic behavior (ESL) 0805 package has ~1/2 the ESL of the 0402 package 2. Extron provides a series of audio calculators that sound system designers, engineers, and technicians frequently need to access, such as determining amplifier power requirements, converting between dBu and dBV or volts, or estimating the loss in sound pressure level with an increase in distance. In electrical and electronic engineering, there is a need to match the input resistance characteristic with that of the. It is a natural phenomenon that occurs for any type of transmission—whether it's electricity or data. Return Loss (dB) 3. Inside the length tuning section, we have something different. 5 GHz are due to the impedance mismatch. 6 to 7. 5 reflection coefficient: VSWR (voltage standing wave ratio, sometimes pronounced "viswar"), is the ratio of the maximum standing wave amplitude at one node to the minimum amplitude at another node in a system. For example, impedance matching typically is used to. I need to measure Z line impedance. 1, for system 2 is 0. Furthermore, once we know what the resistances are the value of Q is fixed. Disc Air Capacitor Calculator; Impedance Calculator : XL, XC; Inductors, Transformers. This can result in issues like ringing or impedance mismatch, resulting in interference or inadequate power transfer. There are different grades of 75 ohm cable and of 50 ohm cable. The receiver, which is on the motherboard, is a standard LVDS receiver, with 100Ω termination resistors. 2 nH inductor, which is (+jomega L =. Reflected power is not. This figure shows that the differential output equals 2 × R P in parallel with the effective value of R′O = 2(VOUT± FO – VO±)/IO±. 01. 7. Good enough, because the calculation for 15 m of typical coax with 6. A perfect match corresponds to Γ = 0, and a complete discontinuity (in which all the energy is. Critical length depends on the allowed impedance deviation between the line and its target impedance. Example Calculation. Calculator Index. Often, the desired value is selected to maximize power transfer or minimize signal reflection. 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. For a RL of 1 dB, the mismatch loss is increased to 6. It is given by [. This VSWR calculator will calculate return loss, mismatch loss, loss in percentage and the reflection coefficient. But it is possible to select any other base if the operator chooses so. To calculate PLF, let Pr be the power received by an antenna and Pi be the. The reason for this approach is due to the behavior of real electrical signals on a transmission line. Your audio device and headphones need to have a complementary impedance in order for them to function properly. ; Bonatti,. Same thing for current. tors. Reflected power ratio for system 1 is 0. Use this calculator to get the value of mismatch Loss from the reflection coefficient. 3). The impedance value you calculate is the transmission line impedance the signal sees as it reflects off the mismatched load and travels on the line. Calculators. It also gives an estimate of the mismatched loss if the mismatch is specified. Impedance Mismatch: An object-relational impedance mismatch refers to a range of problems representing data from relational databases in object-oriented programming languages. Most engineers are aware of the issues associated with electric surges, which can generate high-frequency noise in a circuit. To use the calculator below, input a values into the fields and hit the enter key. g. Routing to pins, pads, components, and BGA breakout routing should be symmetric and length matched, with length tuning/mismatch applied near the source end of a link. Let’s use some of these numbers in the calculator. Critical length is longer when the impedance deviation is larger. TDR feeds a pulse onto the transmission line on a test coupon. 091) (0. So rather than setting impedance for every different frequency, the manufactures set the nominal impedance for a speaker, which is calculated from the lowest values of the impedance of that speaker, and mainly their average is set as the impedance. Zin = 50* (1 + S11)/ (1 - S11) Zout = 50* (1 + S22)/ (1 - S22) Where Zin and Zout are the impedances looking INTO the device. 05 that is free software and very famous among designers. To ensure maximum power transfer, we use a matching unit between the load and the source, such that the impedance of the load and matching unit put together is equal to the complex conjugate of the source impedance. In an attenuator, it is a measure of the deviation from 50 or 75 ohms of the component’s input and output impedances. 30 MB. In one typical RF application, VSWR is used to measure the amount of reflection due to impedance mismatch. Voltage Divider Calculator 1 (Fixed) Voltage Divider Calculator 2 (Adjusteable) Capacitors. 2 into Equation 4, the mismatch uncertainty works out to MU = 0. e. You can find out controlled impedance for a trace through these calculators. 3), we can think of a transistor as a non-linear voltage-to-current converter having an exponential characteristic. 2 into Equation 4, the mismatch uncertainty works out to MU = 0. Example [Math Processing Error] 6. 99 $ = 1-Gamma^2$. Some systems use 75 Ω; this latter value is more appropriate for high-speed digital signals. The relationship between impedance mismatch and reflection can be visualized on a Smith chart. Hence, the return loss is always lower than the ideal system (i. For a return loss of 10 dB, the mismatch loss is 0. But when I use the BNC cable connects to the FG, and the scope cable connect to the scope I got 2Vpp output with the same input. Upon arriving back at the source, part of the reflected wave is coupled back. Any mismatch caused by parasitics will produce reflections. This could modify the impedance match at the output; even though we might have some reflection and impedance mismatch, the bias tee is shifting its passband such that the load power can be increased. Let's match the impedance of the same signal since differential pair routing is completed when the impedance is matched properly. 6 inches - this is very easy to do; If you can access a differential impedance calculator, then use differential microstrips or coplanar differential microstrips (both with controlled impedance) and design to the 90 Ohm differential impedance spec;The impedance mismatch in transmission lines is the root cause of most reflections and power losses. Twisted pairs are used with balanced signals. 398Ω. C Value: pF C Value: pF. When the differential via pair is very short, its impedance will not matter; the input impedance at the via pair will be the input differential impedance from Pair 2. To start working with a Smith chart for impedance matching, we need to normalize our load component that requires impedance matching to the desired system impedance. First, if we have a common-mode voltage source the input impedance it "sees" looking. 36Ω), the impedance is: Transformed through 25 feet of RG-8 coaxial cable to 111. In addition, the values of speaker impedances listed on the back of speaker boxes. This is the impedance matching calculator - a great tool that helps you solve problems with matching electronic elements within a. Let's look at a range of impedance mismatch from 50 ohms, for 50 to 100 ohms in the plot below. So if you have a 55 Ohm line and you terminate it with 50 Ohms, you're looking at about 5% reflection. The amount of reflected signal from the load is dependent on the degree of mismatch between the source impedance and the load impedance. This delay results in timing errors, data skew, clock, and data mismatches, and causes reliability issues. In figure (b), a two-port network was inserted between them. The VSWR is measured in a network analyzer by generating a sine wave signal and measuring the voltage at various points along the line. If you have a 10 Ω resistor, 2 mH inductor, and 500 μF capacitor, the impedance is 0. , refractive index, dielectric constant, and conductivity), sound waves are also reflected at the interface of two media. This calculator computes the matched line loss for a transmission line using a model calibrated from data for the transmission line types built in to the calculator. Losses In Transformer:. 2017 Return loss and impedance Detail: comment 30, KRn receiver differential input return loss • Now that COM is defined with a near-neutral termination and package impedance, receiver mismatch is the receiver designer's concern, not the standard's, unless it is very extreme, because the receiver interferenceVSWR varies from a ratio of 1, indicating a system with no impedance between components, to an absolute mismatch where VSWR is anything up to ∞. Some of the impinging energy will reflect to the source, with the amount dependent on the magnitude of the mismatch (Figure 2). Vinamra [ 10 ] studied the plate impact problem on layered medium by tracing all the ways propagating in the system and solving them to. The series representation of the circuit in Figure 1. The receiver, which is on the motherboard, is a standard LVDS receiver, with 100Ω termination resistors. Fill in the input field and select the input type and click the "calculate" button to show the values. The system impedance might be a 50 Ohm transmission line. S-parameters for the impedance matching network shown above. 1777939889323 I calculate it and I received a negative number how could it be? Kind regardsThe acoustic impedance is the product of acoustic velocity ρ of the wave propagating media. The total efficiency of an antenna is the radiation efficiency multiplied by the impedance mismatch loss of the antenna, when connected to a transmission line or receiver (radio or transmitter). 452, or -7 dB return loss), indicating some. Impedance. Calculate the input. The reduced values of the realized gain below 6. You have to multiply by 50 to convert the normalized impedance into ohms (assuming your S parameters were measured on a 50 ohm network analyzer). Thus, it gives us the total variation in the load power. 5. Impedance mismatch. , refractive index, dielectric constant, and conductivity), sound waves are also reflected at the interface of two media. It is the output power when a signal is concentrated into a smaller area by the Antenna. Twisted pairs are used with balanced signals. 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. The Smith Chart achieves this by superimposing a grid on S11 that maps load impedance. Object–relational impedance mismatch creates difficulties going from data in relational data stores (relational database management system [“RDBMS”]) to usage in domain-driven object models. 0. 8785 dB and phase at this point is 175. This reduction of signal, also called attenuation, is directly related to the length of a cable—the longer the cable, the greater the insertion loss. P802. But due to antenna bandwidth constraints such as those posed by wideband antennas such as LTE, a lower limit of 6 dB is the commonly. As the VSWR increases, the quality of the match deteriorates and more power is reflected back. 94dB: if we calculate the mismatch for the impedance being fed (note the reference impedance is 18. 83% is. In one typical RF application, VSWR is used to measure the amount of reflection due to impedance mismatch. The magnitude of the ripple will depend upon the severity of the impedance mismatch at the interface, and the period of the ripple over frequency will. Inside the length tuning section, we have something different. They follow a constant theme which is designed to make them simple and intuitive to use. Chen studied the effect of heterogeneity in the form of impedance mismatch, interface density, and thickness ratio on plane wave propagation through layered composites and on the wave structure. For an ideal system, reflected power is zero, so return loss is infinity (∞). 9 ohms of effective speaker load no matter the impedance of your headphones, even with three sets of low impedance headphones used simultaneously. Depending on the size of the gap and the distance to the plane, you may see an impedance discontinuity. Now, we have a termination resistor of about 100Ohms or 120Ohms. Normally, we expect the above circuit to have a gain of 10+7 = 17 dB; however, because of the mismatch loss, the actual gain can vary between 17 - 0. The shape of the reflected wave is also valuable since it reveals both the nature and magnitude of the mismatch. Then between two equal impedances looking in the direction of the source impedance Z S, the value of the series resistor, R1 is 4Ω and the value of the parallel resistor, R2 is 8Ω. 04 dB. An impedance mismatch in a circuit or along a transmission line will produce a reflection back to the source of the signal. Mediums in which the speed of sound is different generally. Hence, the return loss is always lower than the ideal system (i. Below 3 GHz, these two methods deviate significantly as 1201 increases above 70 n. Solution At the design frequency, the impedance looking into this section of line from the emitter should be equal to that of a 2. realizable impedance values by simply observing the unit circle. S21 is power gain. Source and load impedance circuit. 999+j16. All signals that travel on a transmission line are waves, whether they are harmonic analog. 2%) = ±3. The transmission line input impedance is related to the load impedance and the length of the line, and S11 also depends on the input impedance of the transmission line. Incidentally, if you increase the return loss, it will correlate to a lower SWR. Chapter VI covers power transfer, signal flowgraph analysis and mismatch uncertainty, along with the remaining uncertainties of power instrumentation and the calculation of overall uncertainty. 6706. Because the phase affects the impedance and because the contributions of. 011. Nominally most speakers are rated at 4Ω, 6Ω, 8Ω, or 16Ω by the manufacturers. 99. The term is used by analogy with the electrical engineering term "impedance managing," where the optimal design is in most cases to have the input. 1. 5 GHz, where 1201 = 93 Cl, the Probe-Tip and Ratio methods report E~ eff = 7. Before the length-tuning section, the odd-mode impedance of the traces in each pair is 50 Ohms, so the differential impedance of each pair is 100 Ohms. 4 GHz (radar systems. Use this tool to calculate the load impedance from S11, the input reflection coefficient. Application Note File. The explanation is simple. Switch on your low-frequency generator, set it to 1 kHz (or use the audio output of your PC), add a 1-kΩ resistor to emulate a high-output impedance, and connect a 4-Ω loudspeaker. It looks possible, but is not something I've tried. First, if we have a common-mode voltage source the input impedance it "sees" looking into the INA134 is RIN(N) in parallel with RIN(P) (You can imagine tying the two inputs together and then applying a voltage source to them). Simple circuit showing characteristic impedance Z o and the. So this measurement typically measures how close to 50 Ohms the antenna impedance is. In this part, we jump into the RF aspect of low noise amplifiers by. If we consider the base emitter voltage, V BE, as the input and the collector current, I C, as the output (figure 11. This is consistent with the peak-to-peak variation of the power curve in Figure 4. S11 Linear to dB. 1. Also, I think that you can ignore impedance mismatch if the traces are short enough (such as a so called. Impedance matching is an important part of RF system design; however, in practice there will likely be some degree of mismatch loss. However, getting an accurate interconnect impedance calculation is the starting point for ensuring accurate signal transfer between a driver and receiver. Normally, this equation is derived while assuming the electromagnetic wave is a plane wave, and most treatments only consider what happens between the transmission line and the load component. V out = Z 2 /(Z 1 +Z 2)*V in. Your relay is single line with characteristic impedance of 50 Ohms. To use the calculator, select your drive voltage units from the dropdown, enter your two known values into the appropriate fields, click calculate, and the converted power, drive voltage, or speaker. 46 dB. Example Calculation. Impedance mismatch. Waterhouse, "Design of probe-fed stacked patches," in IEEE Transactions on. e. For example, the THS4509 performs best with R F in the range of 300 to 500 W. Every PDN has impedance, both resistive and capacitive components. 02 Amps. Could you explain using these numbers how to find R and jR. be used to add or subtract an arbitrary number of power, to convert power and voltage units from the linear to the logarithmic. 54 dB. Let’s calculate the noise figure by just considering the effect of the drain current. e. This speaker crossover calculator will help you design a set of amazing sounding speakers. 02 Amps. VSWR Reduction by Matched Attenuator: By inserting a matched (nominal system impedance) attenuator in front of a mismatched load impedance, the mismatch "seen" at the input of the attenuator is improved by an amount equal to twice the value of attenuator. So, it is an impedance mismatch condition and it can be overcome by using an impedance matching transformer with its impedance transformation ratio of. Four 8 ohm cabs connected to your amp will present a 2 ohm load. On the other hand, the prime consideration for an audio reproduction circuit is high. Load Resistance: Load Reactance: Desired Q: Frequency: Please send comments and questions to John Wetherell at [email protected] other cases, the input impedance of the antenna or load is not 50 ohms by design, or there is some imaginary part of the impedance (i.