Advantages of using Parametric Amplifier over Microwave Amplifier

Hi ,

I would like to know the advantages of using a Parametric Amplifier over a Microwave Amplifier for RF transmission.


Regards,
rc

This ancient history and might be totally of beam, but. . . In the late 1960's TV went to the UHF band (420 -860 MHz), the output device was thermionic (a klystron), while it delivered 50kW of power it required .2 watts of modulated drive power. There were no transistor devices that could handle this power (!) so the technique was to use local oscillator of about 20W (fout/3 frequency) this then went through a varactor tripler to get about 5 watts at the output frequency. this then went into another varactor diode along with the video, to get .5W of fully modulated carrier.
Move forward 5 years, and the smaller stations went on air, these used valves, this time the local oscillator was offset from the carrier by 39.5 MHz. the final varactor diode then gave us 1 watt of modulated carrier, from a local oscillator pump of 5watts and and about .1 watt of video modulated IF (39.5). Is that what you mean by a parametric amplfier?, .1W in @ 39.5, 1 W out @ Fv.
The only advantage was that you could get power out at a level much higher then that available from transistors at that frequency. I guess its the same now, but the powers and frequencies have several 0's added to them
Frank

parametric amps were popular when transistors with high operating frequencies were not available. With the advent of modern transistors, parametric amps fell out of use.

But if you needed gain at, say, 300 GHz, it might be worth the hassle of doing a parametrically pumped diode amplifier.

Hi biff,

Accepted, but what is the advantage of using it over microwave amplifier?Afterall the same could have been done using microwave amplifier.

Correct me if i'm wrong.


regards,
rc

there are a lot of disadvantages! such as needing filtering structures around the non-linear device that is doing the amplifier function. You need an input port, and output port, and a pump port. Doing all of those properly and filtering out the pump frequency (to get high efficiency) mean you will necessarily have narrow band operation.

Also, the paramp can more easily oscillate spuriously than a FET amp will.

In some frequency ranges, you might have a better noise figure, or better residiual phase noise, with the paraamp.

They are fun to play with from a purely theoretical point of view. Controlling the input, output, and idler frequencies the device can see "magically" creates a negative resistance that you can use as an amplifier. There is a good (old) book by Penfield and Rafuse that goes over the basic equations of Varactor paraamp pumping.

I suppose that with all the new materials and semiconductors being recently developed, there might be some newly discovered material that could be used for a travelling wave paraamp design. Something like a an erbium doped fiber optic laser pumped amplifier, but made for microwave amplification. If possible, it might have a huge instantaneous bandwidth.

After reading the above, I would like to explain some basics.
A. a parametric amplifier is a class of microwave amplifiers.
B. I have made several parametric amplifiers , for 1296 MHz, for 4 GHz, etc. Now this technology is a history as MESFET and HEMT devices are better and easier to design.
C. The principle of a parametric amplifier is in Manley-Rowe theory about how electric power can be translated from one frequency to another (or the same) using a variable-reactance element.
Using the variable reactance, e.g. a varactor diode or a variable-inductance offered to reduce the resistive noise, so parametric amplifiers had much lower noise figure than semiconductor or vacuum-tube amplifiers till ~1980.
Read more in the "old books" if you wish; now the advantages of parametric amplifiers are overshadowed by modern semiconductor devices that need only DC current to operate. Parametric amplifiers had to be "pumped" by microwave power, usually at a higher than signal frequency.

Thanks jiripolivka, but would like to know from u the reason behind the non-linear character in case of paramps.I mean why does it shows a non-linear character ? Moreover would like to know if Optical Paramps are in use or not.

regards,
rc

Microwave and audio parametric amplifiers were used as low-noise amplifiers, to process low-level signals. Therefore their non-linearity probably never occurred in use.
In principle, Manley-Rowe theory holds for any frequency combination, and should apply also in optics. I am not aware about the application in optics but it is clearly possible.
In optical spectrum (frequencies above IR), however, quantum noise prevails above thermal noise, so low-noise amplification is usually not needed or not possible.

Hi Jiripolivka, I would like to go through the Manley-Rowe theory, but there are so much of it in internet that i find it confusing.Hence would like to have your guidence regarding the same.

Regards,
rc

Dear friend,

I am not sure if at this time the effort is worth of it, but in ~1960s there were some good books on paramp design. One was by Blackwell and Kotzebue, and in IEEE-MTT Transactions you can find many detailed descriptions of various paramps.
Today the best microwave amplifiers are designed with HEMTs, with noise figure often as good as that of earlier masers. I would not try making a paramp again!

Hi Jiripolivka, actually i want to study non-linearity of an electronic communication device and hence i chose paramps.But while going through ur advice i also don't find it worth to study paramp.But i'm not sure as which one can be worth studying the non-linear behaviour in present day devices.I'm not sure if HEMT shows such non-linear characters as paramps.ur advice plz.

All RF and other amplifiers are non-linear under "high-level" signals. This is characterized by 1-dB compression of their gain and otherwise.
The low-noise amplifiers typically saturate with lower-level signals than power amplifiers. There is a lot of books and literature on it for many devices, and on measurement methods, too.

Dear Jiripolivka, Can u give me some more details regarding the amplifiers and name of books which i can go through?

Thanking you.

Regards

It is tough to find the forgotten stuff. Try these:

Blackwell, Kotzebue, Semiconductor-diode parametric amplifiers, Prentice-Hall, Englewood Cliffs, N.J., 1961
De Jager, J.T.: IEEE Trans., MTT-12, pp. 459-467, July 1964, on Maximum Bandwidth of a Non-Degenerate Parametric Amplifier,


There were many interesting studies over 1960-1970. Go to a library and take some volumes of IEEE-MTT transactions. Parametric amplifiers were good till the first MESFETs arrived.

Now I do not see the purpose, paramps needed to be pumped by e.g. a 50 GHz, 100 mW pump if used at 4 or 12 GHz, they exhibited a negative resistance, so circulators were needed...
As a history study, fine. I would not try developing one again.

No Sir, i was asking for the new devices and not parametric amplifier related papers.I'm not looking forward towards paramps but those devices which replaced paramps (those particular names of RF amplifier devices) whose non-linearity and chaos can be worth studying.

Regards

Sorry for the misunderstanding!

There are many new low-noise wonderful structures now being used as well as developed. Google MESFET, HEMT, graphene field-effect transistor, etc.

I am now only an user, lucky to be able to find a flood of wonderful devices for low-noise amplifiers, from ~ DC up to >100 GHz. For commercial products, try Maxim, Analog Devices, RFHIC, RF MIcro Devices, Skyworks, and more. Every month someone introduces a new and better device.