# Talk:Waffle-iron filter

The current version (for me, http://en.wikipedia.org/w/index.php?title=Waffle-iron_filter&oldid=461587287) says "Circular teeth will handle about 1.4 times the power capability of square teeth without arcing". I suspect that a factor of "about 1.4" is actually "square root of 2" (1.4142…) as this ratio happens to occur quite often, but without a reference I cannot be sure. -- Whitepaw (talk) 12:47, 20 November 2011 (UTC)

I believe the figure was arrived at experimentally and is not connected with a root-2 relationship. SpinningSpark 20:12, 20 November 2011 (UTC)

This review is transcluded from Talk:Waffle-iron filter/GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Dolphin51 (talk · contribs) 23:51, 18 December 2011 (UTC)
I will review this one.  I think it is a high-quality article and will not require much to reach GA status.Dolphin (t) 23:51, 18 December 2011 (UTC)

SpinningSpark has given us a high-quality article and two high-quality images to support it.
I have made some minor tweaks for clarification.  Please check that my tweaks did no damage.  See my diff.


### The lead
Use of the red link waveguide filter in the opening sentence detracts significantly from the appearance of this article.  I suggest that until an article titled Waveguide filter exists, these two words should link to Waveguide and Filter (signal processing).
I don't agree with you on this.  This is entirely consistent with WP:REDLINK and is precisely the situation in which redlinks should be used.  Waveguide filters are a very important application of electronic filtering and most definitely should have an article.  In my opinion it is a major ommission from our set of filter articles.  It is on my to do list and I will be creating an article at some point if someone else does not get there first.
Filters with an analogous design are now appearing in photonics, but at a much smaller scale, due to the higher frequency, and can be incorporated into integrated circuits. This sentence is clumsy.  If it is necessary to say but at a much smaller scale, due to the  higher frequency these ideas should probably go into a separate sentence.
Done.
The third para talks about design techniques but doesn’t clarify that this refers to techniques for design of WI filters.  Readers might get the impression it is techniques for design of circuits/systems that incorporate WI filters.
Done.
SpinningSpark 11:02, 24 December 2011 (UTC)


### Description
… both a wide, low insertion loss, passband and a wide (sometimes very wide) stopband … This expression is clumsy. I suggest it should be refined, possibly by splitting the existing sentence into two sentences.
Do you have a suggestion?  The form is X is used when both condition A and condition B are required.  Splitting the sentence will lose the sense of simultaneous requirements which it was meant to impart. SpinningSpark 11:10, 24 December 2011 (UTC)
The sentence Waffle-iron filters are used where both a wide, low insertion loss, passband and a wide (sometimes very wide) stopband are needed should be made more encyclopedic. I suggest re-wording to something like one of the following:
Waffle-iron filters are used where a wide stopband and a wide passband with low insertion loss are needed.
Waffle-iron filters can be used where a very wide stopband and a wide passband with low insertion loss are needed.
Waffle-iron filters are used where a wide passband, low insertion loss, and a wide stopband are needed.
Waffle-iron filters are used where a wide passband and wide stopband are needed.  In these filters, the passband has a low insertion loss and the stopband can be much wider than in other types of filters.
Dolphin (t) 12:30, 24 December 2011 (UTC)


### Operation
At the first appearance of TEn0 modes, TM modes and TEM modes I suggest linking to Transverse mode#Types of modes.
Done
end matching sections.  Should that be end-matching sections?
Done
SpinningSpark 11:15, 24 December 2011 (UTC)


### Design
The article uses the concept of impedance matching but I can see no link to Impedance matching or explanation of the concept.
Dolphin (t) 07:37, 19 December 2011 (UTC)
Done


### Multiple unit filters
The following sentence is clumsy: In many cases a two-unit design can be reduced to a single unit if tapering of the teeth size is allowed, while still maintaining the same wide stopband.  What do you think of the following alternative syntax?
If tapering of the teeth is allowed, a two-unit design can be reduced to a single unit with the same wide stopband.
Done, with retention of the conditional clause.


### High power
“For instance” and “on the other hand” are not encyclopedic expressions.  Presumably it is Matthaei who described the 2 MW filter. What do you think of the following alternative statement?
Matthaei describes a 1.2-1.64GHz passband filter with rounded teeth and a power-handling capability of 1.4 MW, and a similar filter with circular teeth that can handle 2 MW.
Why is for instance unencyclopaedic? It indicates a specific example, as opposed to a definitive limit. WP:WTW actually uses the expression in its own text.
Paralleling filters with power dividers and then combining their outputs can provide even greater power handling.  What do you think of the following alternative statement?
Connecting filters and power dividers in parallel and then …
That's not what it means.  The filters are connected in parallel by means of of power dividers.  They are not connected in parallel with the power dividers.  The example diagram with amplifiers in the power divider article should make this clear.  Reworded slighty.


### Photonics
The following sentence is clumsy: Filter structures exist in photonics that are analogous to the waffle-iron filter but operate at a much higher frequency and are much smaller.  What do you think of the following alternative syntax?
Filter structures that are analogous to the waffle-iron filter are used in photonics but operate at a much higher frequency and are much smaller than those used in electronics.
Dolphin (t) 02:25, 23 December 2011 (UTC)
Done
SpinningSpark 13:15, 24 December 2011 (UTC)


### The lead
There may be a misunderstanding of my comments about the red link waveguide filter.  I'm not saying Wikipedia doesn't need an article about waveguide filters.  I'm saying that until such an article exists, it would be better for these two words to link to Waveguide and Filter (signal processing) than to have no link to further information.  (As soon as the article Waveguide filter exists, you can amend this article to show the new link.)
The words waveguide filter are not used in an incidental fashion, or in some relatively minor part of the article.  They are the kernel of the opening sentence, explaining what a waffle-iron filter is.  The article begins by saying A waffle-iron filter is a type of waveguide filter ...  The red link is satisfactory for readers who already know what a waveguide filter is; but it is unsatisfactory for readers who don't.  A red link is perfect for reminding you and a small number of other Users that this topic is work-in-progress and we need a new article on waveguide filters, but it is hopeless at providing information to hundreds of readers who don't know what a waveguide filter is.  Good articles are not work-in-progress.  The expectation is that they will be read by a large number of readers, most of whom will be learning about the topic for the first time. Ordinary articles become good articles by providing valuable information that is easily assimilated and well organised. Dolphin (t) 13:07, 24 December 2011 (UTC)

There is no misunderstanding, I believe the redlink should stay because of the importance of the potential article.  Removing redlinks because the article does not yet exist is not a valid reason for removal according to both WP:REDLINK and WP:LINK.
Legitimate red links should not be resolved by simply removing the bracket. If a red link is within the context of the article, and it is a topic with the potential to eventually be a neutral, verifiable and encyclopedic article, then the link should be kept. Such links do not have an expiration date, beyond which they must be "fixed". Red links should be removed only if they point to articles that are unlikely ever to be created, such as the names of book chapters, or if they would have little significance in the context of the present article even if they were created.
Another reason for retaining redlinks such as this is that the new article, when created, will automatically link to the right place.  There is no need to keep notes for the future on what links should be changed when whatever is created (and bear in mind it might not be me doing the creating).
Filter (signal processing) is already linked and waveguide can easily be linked also.  There is no need to link the compound waveguide filter.  Furthermore, WP:LINK disapproves of this practice: When possible, avoid placing links next to each other so that they look like a single link.  In short, what I have done is entirely supported by guidelines and is not contrary to any of the GA criteria. SpinningSpark 13:37, 24 December 2011 (UTC)
Thanks for explaining your viewpoint.  My thoughts at the moment are that the primary purpose of the article Waffle-iron filter is to explain what a waffle-iron filter is.  At present it does so in terms of the waveguide filter, a subject about which Wikipedia has no information.  (I have checked a couple of dictionaries and neither contains an entry on waveguide filter.)  This situation is sufficient for the article to be promoted to C-class, and probably even to B-class, but with respect to the standards expected of good articles this article fails to explain what a waffle-iron filter is.  The Wikiproject Electronics is presently sponsoring 8 articles that have GA status.  I have checked them all and not one of them relies on a red link anywhere in the lead section.
As soon as Wikipedia has an article on waveguide filters, or the article contains an explanation of what a waveguide filter is, it should be a formality for Waffle-iron filter to be promoted to Good Article.
I am happy to promote Waffle-iron filter to B-class but not to Good Article until it adequately explains what a waffle-iron filter is. I will make my decision in 24 hours or so.
You may have missed my suggestions in this edit. Dolphin (t) 12:29, 25 December 2011 (UTC)
I request you seek a second opinion. SpinningSpark 12:59, 25 December 2011 (UTC)
Thanks for creating the new article Waveguide filter.  If you address the suggestions I made in this edit I think we will be finished. Dolphin (t) 06:37, 27 December 2011 (UTC)
Is your objection to the phrase "sometimes very wide"? If so, that could be made more specific with Waffle-iron filters are used where both a wide, low insertion loss, passband and a wide stopband (sometimes covering several octaves) are needed. SpinningSpark 12:35, 27 December 2011 (UTC)
I challenged this sentence because of its clumsy syntax.  It looks like about three sentences merged into one.  It uses the word both and then offers not two but three different qualities - wide passband, low insertion loss, and wide stopband.  (And four different qualities if we include very wide stopband.)  The expression sometimes very wide in brackets looks like the stub of a sentence plonked into the middle of another sentence that is already overflowing with different ideas.  My suggestions are an attempt to retain all your ideas but to find syntax that looks more like an encyclopedia and less like my handwritten notes from student days.
For example, consider the expression wide, low insertion loss, passband.  The noun is passband and the other four words are all adjectival even though low insertion loss, on its own, is not an adjective.  Four adjectives and two commas to support one noun makes for difficult syntax.  Hence my suggestion that the adjectival bits should be dispersed to something like a wide passband with low insertion loss so that insertion loss can function as a noun in its own right and is no longer being used as an adjective to support the noun passband.  (A brown dog with a floppy left ear is easier to read than A brown floppy left eared dog.) Dolphin (t) 04:53, 28 December 2011 (UTC)
Low insertion loss is a desired quality of the passband only.  I have constructed this as one sentence because it is the combination of all these qualities together that make waffle-irons attractive.  Splitting the sentence loses this idea.  It seems now that this has have nothing to do with the original accusation of "unencyclopedic" - it is all straightforwardly factual. SpinningSpark 09:53, 28 December 2011 (UTC)
Waffle-iron filters are used where both a wide passband with low insertion loss, and a wide (sometimes very wide) stopband are needed

If you are offering Waffle-iron filters are used where both a wide passband with low insertion loss, and a wide (sometimes very wide) stopband are needed, I can accept that.  Paste it into the article and I think the GA process is about done.Dolphin (t) 11:45, 28 December 2011 (UTC)
That's the same as I wrote isn't it? If not, I can't see the change.  Anyway, it will do - now in. SpinningSpark 12:20, 28 December 2011 (UTC)
Thanks for that.  It is exactly the same as you wrote at the end of this edit. Dolphin (t) 22:53, 28 December 2011 (UTC)


### Conclusion
Prose: Good
Style: Complies
Verifiable: Complies via citations and references
Broad: Sufficiently broad coverage of a very specialised topic
Focused Very focused
NPOV: Complies
Stable: Very stable
Images: Checked
Overall: Pass
Dolphin (t) 23:02, 28 December 2011 (UTC)

This bit:

Incident signals containing TM modes above a certain frequency can generate modes which propagate along the longitudinal slots with the slots themselves acting as waveguides. The point at which this can start to happen is the frequency at which the height of the slot is greater than half the free-space wavelength of the signal. If this frequency is above the required stopband of the filter the effect is of no consequence. Otherwise, steps outside the filter are needed to suppress these modes and can be incorporated into the end-matching sections.
isn't entirely clear to me. In this mode, is the E field going from one side of the slot to other? If so, then given that the bottom of the slot is a short, and the top is open, then shouldn't this mode start to propagate when the depth of the slot is greater than a quarter of the the free-space wavelength. Also, why does this couple to TM modes in the main guide more than TE modes? - or is it assumed that TE0n modes have been suppressed? You have my applause for your work on this article by the way. --catslash (talk) 00:36, 29 December 2011 (UTC)

I got it from Matthaei et al. who do not give any calculations but I am prepared to take their word for it.  If you ping me an e-mail I will send you a copy of the page if you like. SpinningSpark 09:04, 29 December 2011 (UTC)
...but the answer appears to be that Matthaei takes the slot depth as the distance from the "ceiling" of the filter to the "floor".  That is, he is considering the slot cut in the top set of corrugations and the bottom set as a single slot whereas you are considering just one of these sets.  In Matthaei's version, of course, both the top and the bottom of the slot are a short, hence half-wavelength modes. SpinningSpark 10:51, 29 December 2011 (UTC)