Ideally you don't want any of the amplifiers to "see" each other. In practice it is often difficult to achieve 20 dB isolation between all branches of the network, but that might be enough. The most common problem of poor isolation in a combiner is that spurious oscillations can occur. For July , this section was moved to a new page, find it here. Ideally, all of your power amplifier signals will add up coherently, and two plus two will equal four.
Now wake up to reality: your power-combined amplifier will have transmission phase errors, and these will cause you to lose power. It's your job to minimize this problem! Phase errors can occur within the power splitter, the individual amplifiers, or the power combiner itself. At Microwaves we call this term the "phase efficiency" of a power-combined power amplifier, but you can call it anything you want. Below is a plot that we generated using Excel, to compute loss in power versus RMS phase errors, in this case for a four-way combiner.
In computing degradation due to phase errors, be sure to convert power to voltage first. If anyone wants, we can supply the spreadsheet that did this calculation. Here are some data points that are "off the chart" for your contemplation: if RMS phase error is 45 degrees like two amps out by 90 degrees you lose 3 dB power, and half of your combined power goes to the isolation load.
At this point, you added two amplifiers together and got the same result as a single amplifier. Pretty stupid on your part. Also, if the RMS error was 90 degrees two amplifiers fighting each other at degrees out of phase, which is the absolute worst you can achieve if you tried , all of the power goes to the load and it goes up in smoke. Update August that curve above was generated by painstaking means of generating four signal voltages in Excel, varying the phase and totaling up the wave.
Doesn't it look familiar? It should, because it is approximated by a cosine-squared function. Let's take a look at an example where we calculate the RMS error of four amplifiers as we shift the phases apart. Below are the data on how we did this, A1, A2, A3 and A4 are the amplifiers, which all start out at 0 degrees phase. Then we gradually shifted first A1, then A2 toward 90 degrees, then A3 and A4 toward degrees. RMS phase error is calculated in the far right column. Now let's look at calculated phase efficiency versus RMS phase error, calculated both ways.
It doesn't fit exactly, but it's really close. The voltage model curve will change depending on how the phase errors occur. If they were "more random", the two curves might lie on top of each other, don't you think? And who really cares if the fit starts to go south after 30 degrees RMS? Engineers need to focus on what is important, not what is unimportant, if you want to be a valuable to your company or customers. Warning to plagiarists: let's pause here a moment and stake out the following claim: there is no other source of information that we can find that shows how SSPA phase efficiency fits a cosine-squared relationship with RMS phase error.
So when you go off and publish a paper that includes an important fact that you learned here, be sure to remember and cite us as your reference. We'll track you down and tell your boss, this has happened before Now let's put out some Microwaves rule of thumb! If you want to have less than 0. Power is the square of voltage. We'll clean it up someday when we are bored.
Thanks for the help, Parrish! What happens in an SSPA where many amplifiers are power combined, with uniform phase distribution? Another Rule of Thumb is appropriate:. The expected RMS phase error is X divided by the square-root of twelve. Of course, basing this calculation on just the waffle pak distribution ignores phase tolerance contributions of wirebonds and combiners, you are on your own to estimate these and recalculate the phase distribution.
If you don't understand and memorize rules and , you might want to pick a different career other than SSPAs Variations in amplitude also cause a loss in power in an SSPA. But it is not as epic as phase errors. Typically you will have all of your amplifiers in gain compression and they are likely to be within 1 dB of each other. The loss in efficiency at this point is just a percent or two much less than 0.
What style you pick has a big effect on second and third harmonics. Egan, this is a good book to buy if you want to move up the RF food chain. We'll summarize the outcomes according to Egan but skip the math. We also had some great help on this topic from Jack K. They have no effect on odd-order intermods and harmonics. If you need to combine more than two amplifiers, you need to make this decision.
The following figures were taken from U. Patent 4,,, Multichannel Combiner Divider , from a discussion under "prior art", to illustrate the first three cases. Thanks to Myron for correcting the patent number! Google now has the best patent search available on the web, in case you were wondering The coupled combiner seems simple enough, but each coupler needs a different coupling coefficient to be successful.
The bandwidth of the approach is limited, and often the loss is high, even when waveguide is used. If you opt to use this, we wish you luck! The coupling coefficients ignoring accumulating "real" losses need to follow the sequence:. A corporate combiner is shown below. This is a "third order" binary combiner, which combined eight sources coherent amplifiers.
This is a very straightforward combiner to develop, however, the loss can pile up, with each additional split the final combiner needs to span an ever-increasing distance. Also, the isolation between each amplifier is not equal. Below is a radial combiner. This type of design is also not for the faint of heart, however, it offers the most bandwidth. Wilkinson's original concept was a radial combiner. Radial combiners often suffer from poor isolation, and they can have tricky line impedance requirements: if you are combining ten fifty-ohm networks, the impedance at the junction is just five ohms.
But they provide the least loss, and the highest bandwidth. Radial combiners made from waveguide are sometimes called "flower-petal mode transducers", and are a whole different ball game compared to "wired" radial combiners. We'll tell you how this combiner works, as soon as TriQuint forks over a check.
Unrelated to CAP's solution, this image came from US patent 5,,, High-efficiency, bi-directional spatial power combiner amplifier. In this combiner, a two-dimensional array of amplifiers is illuminated from a feed horn.
Each amplifier has two antennas at opposite polarization, vertical for input and horizontal for output for example. An ortho-mode transducer or circulator can be used to separate the input and output signals. By locating the input and output an the same side of the array, the inventors have solve the problem of heat sinking. For the spatial combiner, it is difficult to achieve uniform power split to each amplifier, and there is "spillover loss" associated with the illumination going outside the array.
Gain is low, in the case of the reflecting array above, you can't exceed the isolation of the two polarizations; you might need a second, smaller array to drive the first one. The bandwidth will be narrow, and it is hard to imagine that you could make such a combiner cheaply. Other than that, Mrs.
Lincoln, how was the play? The term "reactive" in this case means that no resistors are used to terminate the errors of an out-of-phase condition like they would in a Wilkinson structure. Reactive combiners can sometimes suffer from oscillations which are the result of the "odd mode" where adjacent amplifiers become degrees out of phase. Also, if one amplifier fails, you are in a world of hurt as it will surely pull down the other amplifiers.
This is by far the most popular amp combining method, when you only have two amplifiers to combine. Examples include the Lange, branchline, and overlay couplers. The input and output return losses of amplifiers are vastly improved when 90 degree combiner is used. The reflected power from the amps is dissipated in the load on the "isolated" port.
For an explanation of this, go to our page on quadrature couplers. Using quadrature combiners can provide an appreciable degree of immunity to load-pull effects, for example, when a solid-state power amplifier is connected to an antenna that has less than perfect impedance match. Learn about this phenomenon here! One great reason for quadrature combining is that you know longer have to worry about load-pulling your driver amplifier.
If your driver amp see such a mismatch, all bets on driving the SSPA to saturation are out the window. A balun can also serve as a degree combiner, often over very wide bandwidth. These provide isolation between the amplifiers, the classic example is the Wilkinson. The Wilkinson splitter also has a fairly wideband response and by adding more sections the bandwidth can be increased.
The Gysel is also a popular in-phase combiner. It offers a distinct advantage over the Wilkinson, in that the isolation loads are one-ports and can be pulled away from the splitter, such that much more power can be dissipated. If you broke into the transmitter floors inside the Empire State Building you might find an entire "herd" of Gysels combining redundant tubes that power up a score of commercial broadcasting systems!
By the way, you'd think that having a megawatt of RF power from one site might cause a little concern about health issues, compared to all the hype about handsets. What is the effect of a mismatched isolation load on the output impedance of an SSPA?
The answer is "it depends". For now, let's consider the effect in a two-way combiner that uses ideal quadrature couplers. Let's also assume that the output port sees a perfect match, while we allow the other ports to have reflection coefficients as numbered below, which can be assumed to be vector quantities.
This figure represents the initial condition when a signal of "Vin" is present at the output port. The phases through a coupled line are as follows: the through path gets degree phase shift, while the coupled path gets 0 degrees. Got that? Now let's look at the returning voltages after the first bounce.
This is part of the magic of a balanced amplifier. No matter how crappy the amplifiers are impedance matched, they cancel out at least on the first bounce. The signal at the output port leaves the system, as we are assuming that it the one port that is actually matched to fifty ohms. If the amplifiers are imperfectly matched, there can be substantial signal at the isolation load, for example, of rho2 and rho3 are 0.
By "substantial" we mean relative to the signal that entered. This is likely a small signal, so we are not talking about any real power. There are other considerations for sizing that load for power which we will address somewhere else. Reverse isolation versus frequency for different supply voltages.
Antennas may be tuned in a similar manner without using large signals that might cause interference with others. A low power generator is connected to port 1, the antenna to port 2, and some form of power or signal level indicator to port 3. The signal level at port 3 is proportional to the transmission loss and should be minimized by tuning the antenna matching network. A time domain reflectometer is easily realized by applying a fast square wave or pulse to port 1 and connecting the device or cable under test to port 2.
Breaks in the cable or other high impedance anomalies will reflect pulses with the same polarity as the input whereas shorts or lower impedances will reflect inverted pulses. Remember the inversion from one port to the next. A clean test signal is necessary for good results. The active circulator brings many of the features of its big brother, the microwave ferrite circulator, down to the lower RF frequencies. Although the active version obviously lacks the power handling capabilities of typical circulators, the small signal applications abound.
Open navigation menu. Close suggestions Search Search. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Uploaded by yel Document Information click to expand document information Date uploaded Aug 09, Did you find this document useful? Is this content inappropriate? Report this Document. Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. UT Dallas Syllabus for ee Basic Electronics - Introduction to Operational Amplifiers.
Jump to Page. Search inside document. In fact, a pad terminated with an open or -5 0 5 10 15 20 Input Power, dBm Figure 4. Reynaldo Perez. Shrishail Bhat. Saragadam Naga Shivanath Rau. Lucas Ernesto Caetano Ernesto.
Thanhha Nguyen. Isaac Cohen. Luiz Gustavo. Professr Professr. Vincent Kennedy. Fremont Navarro Gottlieb. Roberto Carlos Vallejo Morales. Theoretical Limitations on the Broadband Matching. Vedran Ibrahimovic. Juan-Wian Coetzer. Prmjit Mhla. Alvin Rymash. Rashmi Samant. Mustafa Nasser. More From yel Popular in Nature.
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Figure 2. But if the load is removed at port 2 then the 1 VDC will "reflect in phase and constructively add to give 2 volts at port 2 and the reflected 1 VDC will appear at port 3 as -1 VDC due to the op-amp inversion.
Now if port 2 is shorted then the 1 VDC will reflect out of phase" and will destructively add to give 0 VDC at port 2 an unusual way to describe why a short gives 0 VDC. As Figures one through three show, this inexpensive amp delivers impressive performance at 5 VDC, even better performance near the absolute maximum rating at 6. Operating above maximum ratings is not recommended. A better choice would be to select a faster, more powerful op-amp or use sockets.
Stable, low inductance precision resistors are required for optimum results. The The resistor values shown may be scaled to build a circulator with a different characteristic impedance. For example, a 75 ohm circulator would use resistors 1. It is interesting to note that a circulator could be built with a different characteristic impedance at each port. Bypass capacitors must be connected to both power supply pins of each opamp to the ground plane.
The prototype uses 0. With the signal source connected to port 1, the amplifier's input or output to port 2, and a signal analyzer to port 3, the amplifier is tuned for maximum return loss by adjusting for minimum signal at port 3. A high return loss is synonymous with a good VSWR since a well matched amplifier will "return", as a reflection, very little of the input signal. Low level signal sources may also be adjusted for 50 ohm output impedance in a similar way. Simply adjust the frequency of the test signal until it is close to the carrier then tune the source for minimum reflection.
Again, the reflected signal appears at the next port. If the source's amplitude is too high for the circulator's op-amps to handle just add an accurate attenuator. The circulator's accuracy is sufficiently high to "see" the return loss of a source through a small pad. Remember, the test signal passes through the pad twice and is attenuated each time so the return loss will seem better than it actually is by twice the attenuator value.
In fact, a pad terminated with an open or. Figure 4. Distortion versus input power for different supply voltages. Figure 5. Reverse isolation versus frequency for different supply voltages. Antennas may be tuned in a similar manner without using large signals that might cause interference with others.
A low power generator is connected to port 1, the antenna to port 2, and some form of power or signal level indicator to port 3. The signal level at port 3 is proportional to the transmission loss and should be minimized by tuning the antenna matching network.
A time domain reflectometer is easily realized by applying a fast square wave or pulse to port 1 and connecting the device or cable under test to port 2. Breaks in the cable or other high impedance anomalies will reflect pulses with the same polarity as the input whereas shorts or lower impedances will reflect inverted pulses.
Remember the inversion from one port to the next. A clean test signal is necessary for good results. The active circulator brings many of the features of its big brother, the microwave ferrite circulator, down to the lower RF frequencies.
Although the active version obviously lacks the power handling capabilities of typical circulators, the small signal applications abound. Open navigation menu. Close suggestions Search Search. Skip carousel. Carousel Previous.
Carousel Next. What is Scribd? Uploaded by yel Document Information click to expand document information Date uploaded Aug 09, Did you find this document useful? Is this content inappropriate? Report this Document. Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. UT Dallas Syllabus for ee Basic Electronics - Introduction to Operational Amplifiers.
Jump to Page. Search inside document. In fact, a pad terminated with an open or -5 0 5 10 15 20 Input Power, dBm Figure 4. Reynaldo Perez. Shrishail Bhat. Saragadam Naga Shivanath Rau. Lucas Ernesto Caetano Ernesto. Thanhha Nguyen. Isaac Cohen. Grundfos circulators would get stuck over the summer when they sat idle for several months.
In the past, I have returned what I Thought was a defective pump only to find out at the supply house that there was a small screw cap to access the rotor with a pocket screw driver to give the rotor a spin. The pump would run fine the rest of the season. Is this a good thing, Yes if you know about it? If you have trouble with the pump next season, you may just need to give it a push!
It looks like you're new here. If you want to get involved, click one of these buttons! Visit HeatingHelp. Click here to Find a Contractor in your area. Here are the website rules, as well as some tips for using this forum. Need to contact us? New Boiler can't maintain temperature in house. Hi all. I am a homeowner, not a professional. Forgive any errors I make in explaining what's going on! The previous system was getting old and we were facing constant breakdowns.
Our old system heated the house well, we could set the temperature to whatever we wanted and in a couple hours, it would be there. I worry with colder temperatures it will not be able to keep temperature at all. We turned the system on at 66F in the house and after almost 24 hours we only just got to 70F in the house. Old system would have taken hours for this. As the built-in circulator runs, the supply water can simply bypass the zones through the low loss header and go straight to the returns.
Since we do not have additional circulator pumps, I'm thinking to tell the contractor to remove the low loss header. The other option would be request he install a circulator pump as indicated in the installation guide, but that seems like it might be unnecessary if we remove the low loss header.
Any opinions on this? Youngplumber Member Posts: January 7 edited January 7. We installed your exactly what your talking about minus the zone valve one zone. We put a circulator in the secondary circut to deliver hot water to the emitters and let the low flow header and built in circulator do its own job. I do belive you need a circulator on the secondary piping also for your system to work properly. Edit: sorry the secondary circut and piping needs circulator.
I originally typed that wrong. Jamie Hall Member Posts: 15, January 7. Low loss header? No secondary circulating pump the CH pump? What was the installer thinking? The purpose of that setup -- with the pump -- is to be able to deliver a nearly constant flow of water to the radiation, at a temperature which allows the radiation to heat the house, while the boiler operates at a flow -- sometimes more, sometimes less -- which allows it, in turn, to operate as efficiently as it can.
If you want to get the best efficiency and operation that that new boiler can produce -- and why not? Get someone in there who knows what he or she is doing and set it up properly. Hoffman Equipped System all original except boiler , Weil-Mclain , 2. Jamie Hall said:. HomerJSmith Member Posts: 1, HomerJSmith said:.
Also, it is interesting because the radiators throughout the house DO get hot. Hot enough that I cannot touch the copper piping for more than a few seconds. Just the intensity of the heat coming off the emitter parts is not there. I have to assume with more flow through them that the intensity of the heat would increase?
An emitter at isn't going to emit much. And the temperature difference from end to end is indicative of relatively little flow. Coupled with the boiler hitting setpoint But we knew that Jersey Shore. EdTheHeaterMan said:. Add a note that says "Please show me where this circulator is" If you still have the final payment due, Don't pay it until you are satisfied.
January 8. He the installer turned it into a gravity job LOL. January 8 edited January 8. The Taco F draws only 0. I see no problem using that pump. If you feel better with the ECM pumps you may want to ask the installing contractor about it. But I would provide the Taco F as my go-to bulletproof part for zone valve systems. They do fail from time to time rarely But I have had good luck with them because I always installed them the way the factory recommends.
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