rf design

I used to be a project manager/senior engineer at a VERY LARGE defense comtractor. I have also consulted at several LARGE defense companies. All you have to do is place milestones at appropriate places. This protects you and the supplier. If the milestone is met, payment is processed. If the contract is yanked, they (the supplier) get paid for their effort. Make sure that the project is well defined. This will reduce the number of UH OHs that usually appear just before a big demo. My projects came in on time and sometimes under budget. I learned to fight my battles with upper management before the project started. I had very little stress as we got closer to completion.

Dave

Joerg,

< There is another option... I like the last option you presented. I agree, an engineers reputation should be determined by the quality of their designs, but have found the pool of engineers with known reputations to be rather small. I have recently worked on designs that 'do-not-work' even after the initial design, and a design review by a 'reputable consultant'. Who's responsible? I guess it depends on the structure of the group you work with, or the details of some legal agreement.

Well, sir, I'd suggest that your past "bittens" are possibly of your own making

10 to 100 millihertz (mhz) are rather low frequencies. Perhaps you meant MEGAhertz, but that is not what the "specification" said.

LIkewise the gate signal between 50 nanoseconds to 1 milliSiemens. That doesn't make a lot of sense. And "some" L-band frequency is pretty vague...like from 1 to 3 Gigs.

Perhaps the bitten might be avoided by writing the specification so that a competent consultant can bid on it properly.

Jim

Sorry, I could go look it up, but what is L band in MHz or GHz?

Hello Rex,

Roughly 800-1500MHz, for most apps.

Regards, Joerg

Hello,

That is unlikely as the market for such a device would be small.

That can be done. But first it requires a detailed and finalized specification. Fixed price contracts are also an option but then the spec must be pretty much "cast in stone" and there needs to be a clause that handles diversions from the spec by the client.

Good consultants don't release designs that do not work properly. Else their reputation would be toast pretty soon ;-)

There is another option and sometimes that is better in the long run. If there is an engineer in-house who could do the job to some extent he or she could be paired up with a consultant. The consultant then suggests all the critical stuff or sometimes designs the nastiest sections, but always explaining what was done and why it was done that way. This will build up know-how where it should be (in house). Done it many times, even across a few thousand miles or an ocean.

Regards, Joerg

Hello,

Known reputation is a problem. How can you tell? That is what I ran into when looking for a consultant who could design for injection molding because that was clearly out of my realm. Got a few bruises there, too.

Calling former clients is one method. However, most contracts clearly prohibit the consultant from revealing the identity of clients. Sometimes that is because the group that needed the consultant was kind of embarrassed that they couldn't do it on their own. So they'd rather not have it broadcast. Other times the matter is just so confidential that the client doesn't want the slightest risk of divulgement. Both are very understandable but will put you in a dilemma figuring whether that consultant is really going to pan out for you.

I believe the best strategy is to enter into a mutual NDA and let the consultant make some suggestions. Many will offer an hour or so of discussion free of charge, just like some attorneys do. If you have knowledgeable folks sitting in (but who don't hedge an NIH syndrome...) they could then voice their opinions afterwards. Other times you might just want to send the docs over and have the consultant propose what he or she would do. When it comes down to the mat, invite the consultant. That's going to cost, of course, but you could still turn them down if uneasy about the person.

I have compiled some thoughts about this on our web site:

Regards, Joerg

snipped-for-privacy@msn.com wrote: snip

It will be hard if there isn't a person who has deep insight into the matter himself. Just like finding a good dentist or plumber is easier if you are familiar with the respective field, otherwise you will need some good luck. On the other hand a well educated and experienced person in that field will be always the better choice. If you are in doubt, it might be of advantage to hire two persons and compare their advices.

--
ciao Ban
Bordighera, Italy

I read in sci.electronics.design that snipped-for-privacy@msn.com wrote (in ) about 'rf design', on Sat, 9 Apr 2005:

Any design work that I do contracts for (normally) EIGHT units:

One Engineering model, that may not be mechanically to drawings;

One prototype, that is to drawings apart from a list of agreed deviations (e.g. moulded parts won't be available);

Six pre-production samples, ***made and tested by the client from parts approved by me (so no purchasing the cheapest trash)***, so I can see that they are competent to make and test, and to show that the design is manufacturable.

Things CAN still go wrong after that, but then they can go wrong after

10 000 units have been built. For example, a manufacturer may 'improve' an IC out of all recognition. (8-O(

--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

You could look at Miteq for upconverters. Not sure what you're on about with the gate signal with programmable output amplitude (what's that doing to the upconverter output?). Anyway Miteq have L-band stuff, have a hunt.

Ken

This is a strange post.

Are you trying to figure out whether the technical spec's can be met or whether there is a methodology for finding good consultants?

From what you've said, the technical spec's don't sound problematic. I am aware of systems which very closely resemble what you describe. One point I'm not too sure about is whether you want the consultant to design the external gating signal, or just accept it. Either way, this part is easy, and could be done with an off-the-shelf RF switch which just takes a TTL input to control the switching.

--Mac

Mac, My post was not very clear. Let me try to clarify. The post was intended to as questions about two areas: (1) electronic design, and (2) business and legal arrangements. As I am new to this area I am trying to get some advice on both. (1) The electronic design would have to convert a programmable output of 10 MHz to 100 MHz to L band frequencies ( 1 GHz to 2 GHz ). The programmable output design is done - we do not have engineers that can handle the up-conversion part of the design. Also, there is a need to gate the L band output with about 1 ns resolution. The gate signal design that will be supplied to the L band output section is done - it is a digital signal with output levels programmable from 0 V to 5 V. (2) The business and legal concerns are about ways to ensure that the result of our business arrangement is working hardware.

Rex, The L band is 30 cm - 15 cm, or, 1 GHz - 2 GHz. Steve

Hello Steve,

What a consultant would have to know are details such as:

- Precision, stability of output frequency?

- Desired sideband rejection?

- Output signal level (dBm)?

- Output range freely programmable? If yes, in what steps?

- Required gating spectral purity?

- EMC concerns (for example if 2.4GHz or 5GHz gear is nearby)?

- Production cost budget?

Up-conversion in itself isn't such a big deal but probably something has to control the exact frequency range where you want to see your

10-100MHz signal converted to. The frequency stability of the oscillator will to a large extent determine the effort. Also, unless you can completely forego sideband rejection this scenario may require several conversions or at least I-Q techniques.

There is a lot of other stuff that needs to be known but which would have to be dealt with outside a public forum. A good consultant will always ask if a spec isn't complete. At an early stage of a concept that would be quite normal.

Usually that's no problem but it might help if you talk this over with someone who has done business with consultants before and whom you trust. It can also be someone with such experience from another technical discipline, like mechanical engineering.

Regards, Joerg

Well, there are still many details unspecified, but if you don't need high power, don't need ultra-high spectral purity or ultra-low phase noise, the design shouldn't be hard for an experienced microwave guy (which I am NOT).

The gating switch part should be easy, unless you need it to be tiny or really cheap, and you may opt to NOT have the contractor do the gating. Instead, just put an RF switch after the contractor-designed mixing / multiplying section. You can buy switches with TTL inputs. The switch will have some additional turn-on time (e.g., 10 ns), but it should be more or less constant, and can therefore be compensated for. (Or, if I correctly infer your application, you can just ignore the additional gating delay.)

I am sort of assuming that there is some linear relationship between the input and output frequency.

I.e., Fout = m * Fin + Fbase where Fout is the output frequency, Fin is the input frequency, and m and Fbase are constants.

As for how to find a good contractor, I don't really know, but it seems like Joerg's advice is pretty good. (Maybe Joerg could tackle the job?)

regards, Mac