Diode for use at 35GHz - which one?

[Dderijken]

Diode for use at 35GHz

Which diode can I use for controlling the phase of
a microstrip patch antenna ???

Have heart a bout 3-bit diode ...
But, really never seen that ... ??

Any help in this question is greatly appreciated.

TIA,

 

[ash]

I saw them in pc power supply (at). But i don't know anything about them.

 

[Mazi3]

if you'll find PIN or varicap diode-they probably have only two very small pieces of golden foil instead of contacts-dimension is of course sub milimeter (0.5x0.5). (about AT power suply: LOL-35GHz), up to 12GHz you can use ordinary PIN diodes as BB833 or BB857... (if you need larger phase shift-cascoded).

Chip version for doing so is to have microstip wire and you can hold something over it, to slow down waves (piece of PTFE). for moving near and far you can use small motor.

 

[Dderijken]

Hi Ash and Mazi3 ... ...
Thanks for the infos ...
I appreciated that very much ....


Mazi3...

Can you tell me a little more about the
chip version of the diode for use at 35GHz

I must confest that ...I have never seen
it before .. Is there any site or links available
so that I can have a look of them ...

Via your post ...I think you are expert
in using diode to control the phase of the
Microstrip antenna ... so, Please take a
take a little time to explain on how can
I use diode to add a variable phase to
the microstrip antenna (or microstrip line)


Please post that in here so that other students can also learn ...

TIA, and have a Nice day ....
Regards,

 

[Mazi3]

Hi all!
I'm not an expert for such high frequencies, my work is (for now) only up to 2GHz. I've seen this diodes on pictures when i've been on UHF seminar. It was project-I-think it was called "converter for 47GHz".
How can I say... main problem is that there things are not cheap. One diode cost about $25, packaged about 50 in box, placed on some kind of jelly. You must glue them to PCB under microscop. Presenter said that he was probably the first person who solder it (picked them from jelly with spittled toothpick) But he waste 20 diodes to solder 4-6
Well with diode you can make phase shifts to build T network, microstrip wire as inductor and two diodes as capacitor. Then you must just apply the exact voltage for wanted phase shift. With frequency of 10GHz shifter had 10-15 silicone diodes for 360 degree phase shift. It act as tunable filter.
I think the most low cost and simple it would be to mechanicaly drive a small pise of insulator (maybe PTFE) over the microstrip wire? If the pice is near, then the waves are slowed down and vice versa.

 

[Dderijken]

1) Well with diode you can make phase shifts to build T network,
microstrip wire as inductor and two diodes as capacitor. Then you must
just apply the exact voltage for wanted phase shift....

2)I think the most low cost and simple it would be to mechanicaly drive a
small pise of insulator (maybe PTFE) over the microstrip wire? If the pice
is near, then the waves are slowed down and vice versa....

Wow ... Thanks a bunch ..buddy ...
That's what I want to learn more about ...
I like to learn those two techniques very much ...

Would you please provide me more infos:

Do you known any LINKS or any infos in how to built
the T-network phase shifter ...

Insulator over the microstrip wire ...???

Is there any practical BOOK or textbook teach about
techniques to make phase shifter ....
I try to find but ...failed to find one ...

If you (or anyone) know ...PLEASE let me know ...

Thanks You All in advance , and
Have a Nice day ...

 

[Mazi3]

I read some stuff in literature, but I don't remember the title.

electrical version is like this: lumped circuit line model,

1)--+--@@@@-+----(2
U U <- sorry this diode is used to be located under second +.
**************************** <- ground

If you can imagine, @@@@ is short wire that has some inductance,
U-s are two reverse polarized varicap diodes, 1,2 are ports.
with voltage applied on the upper line you can control
capacitance of diodes -> consequently you are controlinf the speed
of travelling the signal. (the lover the voltage, tha slower it travels)




second, mechanical is like that:

88888888 <- a piece of PTFE that travels up and down.

---------------------------------- <-microstrip wire
**********************************

so, nearer the insulator to the microstrip wire, the slower signals are travels

I think you can find some about lumped lines in Microwave handbook (at least two editions).

 

[Gemini1706]

I am a little bit confused about this discussion.

How a PIN diode will change the phase of RF? I beleive that PIN diodes are variable resistors, but varactors are capacitance varable didoes.

I know about phase-shifters with varactors and a bi-directional coupler, or varactors and a microstrip-line, but never heard of PIN-diode and microstrip line as a phase shifter. They are used as varaible attenuators.

Also, why the price is so high as claimed above? Is it because of very high power?
It looks like we are talking about different things..Maybe you are talking about high-power, or super-precision control.


Also, a phase-shifter does not change the speed of wave travel, it just adds more delay sorta-speak, but not speed-change.
Delay means that the wave-front will arrive later, but it is still traveling with the same speed as before.

I am confused...

Please, guys, clarify what you are talking about

Cheers.

 

[Gemini1706]

Hmmm... I guess I maybe getting it now

Did not see that 35GHz frequency

35 GHz Holy s_t...

Is it that much expensive to have those diodes at 35GHz.?

Is that it? I guess maybe..

 

[Dderijken]

Hi Mazi3 and Gemini1706 ... ......

Thanks, thanks and thanks very much ...
As I said before ...I'm just a newbie in this field ...
However, I enjoy to read EVERY word you wrote ...
(so PLZ write and continue to share your experiences ...)
It's very instructive to me .. through the discussions
I have learnt many things thanks to you .....(U got to believe this)...

This is what I have been told ( I understand it ..but not really sure)

When a field incidents on the surface of a patch, (see attached figure)
this field induces a current on the surface of the patch, the current
will flow along the strip to the diode and reflected back ...
So, if the diode is placed at different positions along the strip we will have
have different delayed phases.
This works ... but not really flexible ...

My question is :

Is there any device (pin-diode, varactor or whatsoever) that can vary
the phase delay by means of bias voltage ....so that I can vary the
phase delay as I want ??? ...

Have you any idea ....??? .. to really this ....??? ...

Anyone else ... ??? any idea ??? ... Please jump in ...

TIA and,
awaiting for your reaction ....
Regards,

 

[Gemini1706]

Ok. I can describe what I use at 2-3GHz (not 35GHz, but maybe it still appies):

1>--------------------------<2
| Coupler |
3| ---------------- |4
| |
VarC<-- VarC<-------
| | | |
GND | GND |
| |
| |
Choke Choke
| |
--------------------------------------< DC Control Voltage

The coupler (with ports 1, 2, 3, 4) is a bi-directional coupler.
If the diode is a varacator (VarC as above), then this is a phase shifter where RF signal comes in from port 1 and output is port 2.
If diode is PIN (instead of VarC), then this is a VVA (Voltage Variable Attenuator).

It is called in general a reflective VVA (or phase shifter if used VarC), because signal comes in port 1, couples to port 4, then it will see the VarC with different C value according to the DC control, then the wave refelcts back to port 2.

Hence, the output signal is actually a reflected signal from port 4 and 3, but not a direct through signal from port 1. That is why it is called reflective. There are other type called absorptive, based on FET devices, and do not use a coupler.

The Choke is an inductor to isolate the DC control signal from the RF waves. usually a cap to ground is added to the choke for increased isolation.

You can go to SkyWorks Inc website (Alhpa industries):
http://www.alphaind.com/

and in the technical library->Application Notes, you will find tons of App Notes about PIN diods, Varactors, Phase shifters, VVAs, relfective, absorptive...etc. It is a nice read.


Now, I am not sure how much of this is relevant at 35GHz? I have no idea, but I guess the same (or similar) techniques apply...

Hope that helps...

Cheers...

 

[Gemini1706]

Oh man, the diagram is messed up , I think the website deletes all un-neccessary spaces.

Anyway, VarC1 is connected to port 3, VarC2 is connected to port 4. VarC1 is also connected to the DC control (to bias the diode) through a Choke, and similarly VarC2.

You can go to the above mentioned website, you will find better diagrams..

Cheers...

 

[Dderijken]

I'll check that site and come back to you
when I have problem ... ...

Pzzzziiizzzz ..Thank a bunch ...buddy ... whistle only otherwise ..I'll be banned ...

 

[Mazi3]

I think, there is no difference between varicap or pin diode at such high frequency. But if they are designed for such frequency, you must know they are probably made in small quantities, not in large volume like BAT14...
That's why they are not cheap. In design you should use only 2-4 single diodes

When the GSMs are to be designed for this frequency, then they'll be cheap...
More than 100GHz are things becoming strange. You can treat the radiation in similar way as light. Don't forget to absorption in air (oxygen at 60GHz, there exists a few bands lower than and a lot of higher than)

Don't use ordinary coil (for biasing) at this frequency, build simple filter with microstrip wire lambda/4 of length (appcad is enought accurate) as narrow as you can. Then put a "half cake" object with radius lambda/4 for a capacitor....

 

[Dderijken]

Hi Mazi3 and Gemini007 ... ...

I'm looking for a shorten way to learn to design MMIC ...
is this possible for a physic-student ??? (I'm not in EE-discipline)...

I like to learn to design MMIC milimeter-wave components ...
(diodes, phase shifters, filters, amplifiers, circulators, etc...)
But don't known where to start from ........
can you give me a hint ... ....

1)... I need a practical book with detailed examples ..
.......(the best way to learn is starting with examples., IMHO. )
........Can you or anyone else ...recommend me such a book ???...

2)... Which software is the common one to be used for this job ...??? ...

3)... If you also have any site with such design infos .. please post it
here so that other members can also benefit ...

TIA,
Best regards,

 

[Mazi3]

well, first MMICs are Microwave Monolitich Integrated Circuits.

So, for designing you have to know a lot of things :twisted: : physics of matter, procedures about manufacturing the ICs, building a transistor, (For Si I've seen a lot of books, for new materials as InP... there is not a lot of it ).
Then about VF components (how to build a tranzistor again!), then comes the filter, impedance matching,.. finaly: knowlege of IC design program, VF simulator,...
and then you must have somebody to pay for building of something. :?
But when you'll become master in these things, you'll be quite rich 8O

Go to library; find a book about designing IC, theory about microwave circuits, dinamical electromagnetism (static too!!), chemistry,... a whole bunch (and unless you are from some kind of "rich" country, you find this in one library, elsewhere you should buy some books on your own)

 

[Basskiller]

I can give you the info of a 3 bit phase shifter that works at 35Ghz +- 3Ghz, I have just tested them out my self. I am working on HDI T/R with HPA, swithes, LNA's and phase shifters. They are a bit lossy about 7 to 9db, but you have 0, 90, 180 and 270 degs.

Tryquen is work on a 4 bit phase shifter but it won't be ready for about 09-2003

I will get you the info tommorow!

Basskiller