Custom Search
Over 10000 Pages Indexed
Your Host
Click here to read about RF CafeKirt

... single-
what an
engineering website
should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5CCG (5th MOB):
My USAF radar shop

Hobby & Fun

Airplanes and Rockets:
My personal hobby website

Equine Kingdom:
My daughter Sally's horse
riding business website -
lots of info

•−•  ••−•    −•−•  •−  ••−•  •
RF Cafe Morse Code >Hear It<

Job Board

About RF Cafe©

RF Cafe E-Mail

phase array: steering problem, help? - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.

 Post subject: phase array: steering problem, help?
Posted: Tue Dec 23, 2008 2:46 pm 

Joined: Tue Dec 23, 2008 2:01 pm
Posts: 2
Location: Madrid

I've been working on a 1x8 linear phase array. The antenna system is working perfect, but I came across with a problem when making the algorithms for steering.

Imagine your phase shifters give a maximum of 400º shift for a particular frequency. Now suppose the required shifts for the eight elements are for example: 0 90 180 270 360 450 540 630º.

I programmed an algorithm that used the periodicity of the signal so those shifts are the same as: 0 90 180 270 360 90 180 270. I moduled all phase shifts to 360.

When testing the radiation pattern in a anechoic chamber, the result was disturbing. I got a maximum in the desired direction but the whole pattern was very smooth, with less lobes that it should have, much less directivity.

Then we used another algorithm that worked. Our phase shifter are switched lines shifters, so in this new algorithm we worked with temporal retards instead of thinking of degrees. The thing is... it works.

Then my question is, why doesn't it work moduling the shifts to 360? shouldn't the pattern be the same??

I'll be thinking about it,
thanks a lot in advance

i'll see you guys around, i'm new in this world (1 year working after finishing college) and i love these forum where you can share information and knowledge.

 Post subject: Phase Shifter
Posted: Fri Jan 16, 2009 4:09 pm 

Joined: Thu Jun 24, 2004 3:10 pm
Posts: 4
What frequency are you working? Type of phase shifter... MEMS?

 Post subject: phase array
Posted: Mon Jan 19, 2009 12:39 pm 

Joined: Tue Dec 23, 2008 2:01 pm
Posts: 2
Location: Madrid
i'm working from 2 to 6 GHz, and with switched lines.
if you can help me, I'd be glad to explain to you my doubt in more detail, although I think it's more or less clear my problem.


 Post subject: Re: phase array: steering problem, help?
Posted: Mon Jan 04, 2010 10:59 pm 

Joined: Tue Apr 11, 2006 8:13 pm
Posts: 34
I dont know if you were able to solve your problem. If you did, could you please post your finding? If not, I have a couple of questions/suggestions:

1. Can you compare the time delay (which worked) to the phase (which did not work).
2. You can measure the phase that is actually being set - measure the phase from the antenna element to the output of the combiner - and ensure that the phase relationship between adjacent elements is what you expect.

From your description, it appears the phase (and/or amplitude) relationship between the elements is not what you had calculated.

 Post subject: Re: phase array: steering problem, help?
Posted: Sat Jan 23, 2010 12:08 am 
User avatar

Joined: Wed Feb 22, 2006 3:51 pm
Posts: 106
If the antenna elements were isolated from each other, the phase shifter and the time delay approaches would in fact give the same result.


Antenna elements couple to each other, which changes the driving point impedance, and a transmission line further transforms the impedance.

Summary: Phase shifters can work, but you have to take inter-element coupling into account.

Good Luck!

 Post subject: Re: phase array: steering problem, help?
Posted: Sat Feb 06, 2010 10:23 am 

Joined: Wed Apr 08, 2009 11:07 am
Posts: 34
This is a trivial point, and I hessitate to bring it up. But you do realize that a "switched line" phase shifter, set into any one position, will have a wildly different phase shift at each and every frequency over the 2 to 6 GHz band. For instance, if you dialed in 180 degrees at 2 ghz, if you touched nothing but simply swept the frequency to 4 GHz, you should get 360 degrees out of it (I am assuming you de-embedded the measurement to right at the switches in the switched line phase shifter, and that the switched lines were all less than a wavelength in length).

If you use software that recognizes the actual time delay switched in for each of the switched lines, then that software will take into account the frequency and calculate the true phase shift at that one frequency.

Maguffin Microwave Consulting

 Post subject: Re: phase array: steering problem, help?
Posted: Sat Feb 06, 2010 10:33 am 

Joined: Wed Apr 08, 2009 11:07 am
Posts: 34
The more I think about this, the more I wonder what the absolute phase shift is of each of your 8 phase shifters, vs setting and frequency. A phase shifter chip, for instance, might have tight specifications for the relative phase shift from one setting to another. But if you measured the absolute phase shift of chip #1, vs. chip #7 that might have been manufcatured 6 months later, I think all bets are off!

Maguffin Microwave Consulting

Posted  11/12/2012
A Disruptive Web Presence

Custom Search
Over 10,000 pages indexed! (none duped or pirated)

Read About RF Cafe
Webmaster: Kirt Blattenberger

RF Cafe Software

RF Cascade Workbook
RF Cascade Workbook is a very extensive system cascaded component Excel workbook that includes the standard Gain, NF, IP2, IP3, Psat calculations, input & output VSWR, noise BW, min/max tolerance, DC power cauculations, graphing of all RF parameters, and has a graphical block diagram tool. An extensive User's Guide is also included. - Only $35.
RF system analysis including
frequency conversion & filters

RF & EE Symbols Word
RF Stencils for Visio

Product & Service Directory
Personally Selected Manufacturers
RF Cafe T-Shirts & Mugs

RF Cafe Software

Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel