Talk:Planar transmission line

Dielectric Lines

The article includes image line in its catalogue of formats. This is consistent with the definition of planar lines as flat, ribbon-shaped lines in the lede. The scope of the article might reasonably have been restricted to those lines constructed using PCB technology, but if dielectric strips are to be included, then all variants (rib-line, NRD etc.) ought to be mentioned. I only raise this issue because the article is a good-article nominee, and coverage of the subject is a good-article criterion. --catslash (talk) 00:26, 16 February 2017 (UTC)

I'm not convinced that NRD can be described as planar whereas at least one of my sources explicitly lists imageline as planar. Numerous sources actually seem to make a distinction, e.g "The hybrid integration technique of planar and NRD-guide circuits for millimeter-wave applications". I've no idea what rib-line is. Do you think it is prevalent enough to justify a section of its own? Feel free to add something if you have sources. SpinningSpark 12:39, 16 February 2017 (UTC)

Ah, here's a source [1] that discusses rib guide (I assume that is the same thing as rib-line) and other dielectric waveguides. Maybe I'll include these as a variants diagram. SpinningSpark 13:03, 16 February 2017 (UTC)

Citation format

I would like to upgrade the citations in this article to use the Harvard format and reflinks. It and WP:SFN. WP:CITEVAR requires that I ask first. Does anyone have an objection? 7&6=thirteen (☎) 15:50, 6 March 2017 (UTC)

Yes, I would object. I would have done it that way in the first place if I thought that it was any better. SpinningSpark 22:35, 6 March 2017 (UTC)

It is better for the readers.

But you are entitled to your opinion and your liberum veto. 7&6=thirteen (☎) 22:51, 6 March 2017 (UTC)

GA Review

This review is transcluded from Talk:Planar transmission line/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Mike Christie (talk · contribs) 23:59, 4 January 2018 (UTC)

I'll review this. Mike Christie (talk - contribs - library) 23:59, 4 January 2018 (UTC)

Just starting to look at this now. A couple of notes on the sources:

• You cite Franco De Flaviis under F in the bibliography and under D when citing him (footnote 4); should be consistent.
  • Fixed SpinningSpark 16:09, 8 January 2018 (UTC)
• The cites to Garg should make it apparent whether you're citing Garg 2001 or Garg 2013.
  • Garg (2001) is the only publication by Garg alone. The 2013 publications is referred to as Garg, Bahl & Bozzi. SpinningSpark 16:09, 8 January 2018 (UTC)

    D'oh. You're right, of course. Mike Christie (talk - contribs - library) 21:17, 8 January 2018 (UTC)

• You have both "Russer" and "Ruisser".
  • Fixed SpinningSpark 16:09, 8 January 2018 (UTC)
• Several works in the bibliography aren't cited; it looks as if most or all of them are by authors you mention in the text, so presumably they cover the material mentioned. Completely optional, but you might consider separating them into a "Further reading" section. The ones I think would be in that category are Barrett (both), Cohn, Connor, Grieg, King, Meier, Pengelly, Robertson, and Wen.
  • That's right, the uncited publications are largely (possibly entirely) the primary sources reporting the discovery of the discussed effect/device. These were not used directly as sources for the article, later secondary sources were used for that, but it is useful to include them for readers who want to look them up. I am not in favour of putting them in further reading; if was asked to recommend further reading for this subject I would not point anyone to the historic primary sources unless that was what was explicitly asked for. SpinningSpark 16:09, 8 January 2018 (UTC)

    Fair enough. Mike Christie (talk - contribs - library) 21:17, 8 January 2018 (UTC)

Other than that the sources and citations look fine.

I'll add notes below as I go through the article. Please revert any copyedits I make if I screw anything up. -- Mike Christie (talk - contribs - library) 20:35, 7 January 2018 (UTC)

Mike, many thanks for reviewing this. SpinningSpark 16:09, 8 January 2018 (UTC)

Just a reminder as I start posting notes that I am not at all knowledgeable in this area; I have some (decades-old) undergraduate physics, but my degree is in maths. I've read the article a couple of times, skimming to get the structure and basic sense, and have done some reading in the connected articles to try and bring myself up to speed. I don't think there's any point in an article like this in asking for definitions of elementary concepts, but I am not always going to be sure what counts as elementary.

• What's the asterisk for on "coplanar waveguide" in the lead? Is it just a typo? Is it intended to be replaced by the disconnected "[A]" at the foot of the lead?

  The footnote which is the target of the [A] is indeed intended to be the target of the *. [This edit] broke it. The edit could be fixed, but Spinningspark may prefer simply to revert it. --catslash (talk) 23:38, 8 January 2018 (UTC)

  I haven't seen that approach used before but I don't think it's forbidden so I've struck the comment. Mike Christie (talk - contribs - library) 12:28, 9 January 2018 (UTC)

• I think the "Stripline was the earliest form" sentence is out of place where it is in the lead, between the list of four forms and the description of the same four. How about starting the paragraph "The earliest form of planar transmission line was conceived during World War I by Robert M. Barrett. It is known as stripline, and is one of the four main types in modern use, along with microstrip, suspended stripline, and coplanar waveguide. All four of these..." or something like that?
  • Done (except it was WWII) SpinningSpark 01:07, 9 January 2018 (UTC)
• Many forms have a narrower bandwidth and in general they produce more signal distortion: it's not clear to me what the comparison is to -- narrower than what? More signal distortion than what? I think this must refer to those forms that can't support the same mode as a pair of wires, but it should be clear. The same is true of the last sentence of that paragraph, I think.
  • Correct, the comparison is between TEM mode (as found in a pair of wires) and non-TEM modes, but I was trying not to use that jargon in the lead. Attempted to clarify, but it's getting a bit clunky. Any suggestions welcome. SpinningSpark 01:07, 9 January 2018 (UTC)

    I tweaked it a bit; how does that look? Mike Christie (talk - contribs - library) 12:28, 9 January 2018 (UTC)

• Planar transmission lines can be used for much more than interconnecting components. They can also be used to construct components. Suggest "Planar transmission lines can be used for constructing components as well as interconnecting them" as more concise.
  • Done. SpinningSpark 01:07, 9 January 2018 (UTC)
• Lumped passive components are often impractical at microwave frequencies for this reason, or because the values required are impractically small to manufacture: I don't understand the "or" here; what's the difference between the two points? Isn't it just "...often impractical at microwave frequencies, because the values required..."?
  • No, the first point concerns the physical size of components compared to size of waves. The second point concerns the electrical value of a component. For instance, making a capacitor with a capacitance less than a picofarad is a design nightmare. The conductors connecting to it are going to have a stray capacitance way more than the component you are trying to connect in the circuit. SpinningSpark 01:07, 9 January 2018 (UTC)

    Are the two things connected? That is, if you were trying to build a component with a tiny capacitance, would you be doing so in order to make it small enough to fit into a lumped component? Also, why are lumped passive components specifically called out here? There's no mention of passive components in the body of the article, at least not using the word "passive". Mike Christie (talk - contribs - library) 12:28, 9 January 2018 (UTC)

    • The two things are indirectly connected in that smaller values generally lead to smaller physical sizes. However, the small value is not chosen in order to produce a small size. Rather, it is a consequence of smaller values are required at higher frequencies to produce the same impedance. This is true of capacitors and inductors, but not resistors. Passive components are explicitly mentioned because it is precisely those components that can be replaced by transmission line circuits. Perhaps this should be explained in the body of the article, but this was the kind of ground I had intended to cover in the redlinked distributed element circuit article (unless someone else like Catslash gets there first due to my current Wikipedia laziness) SpinningSpark 14:36, 9 January 2018 (UTC)

      I see the distinction, and I understand why the physical size prevents the components from being lumpable, if that's a word. For the point about electrical values, I'm not seeing why that's relevant in this sentence. Skipping the "for this reason" point we're saying "Lumped passive components may be impractical at microwave frequencies because the values required are impractically small to manufacture". I can see that a picofarad capacitor can't be built because of the stray capacitance issue, but why does that specifically affect the ability to treat passive components as lumped? Why isn't it a more general problem affecting circuits at these frequencies? Mike Christie (talk - contribs - library) 23:28, 11 January 2018 (UTC)

      • For the point about electrical values, I'm not seeing why that's relevant... It's relevant because the inability to (easily) manufacture a lumped component forces the choice of DE circuits.
      • ...why does that specifically affect the ability to treat passive components as lumped? It doesn't, although failure to lump may also be a problem at the same time. The point is that it forces the designer to move to DE circuitry.
      • Why isn't it a more general problem affecting circuits at these frequencies? It is. SpinningSpark 16:26, 12 January 2018 (UTC)

        I've struck this point, because now I understand there's nothing wrong with the sentence. I think it might help to add "component" before "values", and I'd like to find a way to recast the sentence so it's clearer the second problem doesn't only apply to passive components, but that's not necessary for GA. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• Whole circuits can be built this way, called distributed element circuits, particularly distributed element filters: The "particularly" threw me for a moment. I think "Whole circuits can be built this way, called distributed element circuits; the method is often used for distributed element filters" would be clearer, assuming that's the intended meaning. Could we just say "...often used for filters", since "distributed element" as a modifier is clearly implied here, retaining the link to distributed element filter from "filters"?
  • Done SpinningSpark 01:07, 9 January 2018 (UTC)
• This gives the planar technologies a big economic advantage over other forms: what other forms are being referred to? If I've understood the lead, we haven't mentioned any non-planar technologies to this point; could a "such as" be added here?

  Added ", such as coaxial cable". (I have seen antenna feed networks being manufactured in coax. A machine cut a set of lengths that were then hand soldered together. It was slow, laborious, error-prone and expensive) --catslash (talk) 00:00, 9 January 2018 (UTC)

I'm going to pause here for your replies just to make sure I'm not misunderstanding things too much to be useful. Mike Christie (talk - contribs - library) 22:26, 8 January 2018 (UTC)

Struck some points and left a couple of notes above. I should have time to return to this tonight. Mike Christie (talk - contribs - library) 12:28, 9 January 2018 (UTC)

Continuing the review:

• The exact mode is identified by a pair of indices counting the number of wavelengths or half-wavelengths along specified transverse dimensions (for instance TE10): I don't really follow this. I understand the idea of counting the number of wavelengths to give an index, but the example only has one number, instead of a pair of indices, and without an example waveguide geometry I don't know how to interpret it. Would a diagram be possible, showing a particular example?
  • Mode numbers rarely (if ever) go beyond a single digit. The convention in virtually every book I have ever seen is to omit the separating comma. TE₁₀ should properly be written TE_1,0 but it never is.

    Could we say, parenthetically or in a footnote, that the two indices are not separated by a comma? Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

  • The linked TEM mode article is actually a redirect to Transverse mode and covers more than TEM. It has some example diagrams which might help the reader but unfortunately none of them are for planar forms so are not appropriate here. I created those diagrams more or less freehand. Planar field patterns are more complex and would really need proper plotting tools to get right. Besides, the issue of transmission modes is a big can of worms and I feel we have already gone too deeply into it for an overview article. It's very hard to generalise the importance of modes without reducing it to a trite one sentence that explains nothing. SpinningSpark 17:02, 12 January 2018 (UTC)

    OK; if it were easy to do a diagram it would have been helpful, but that's fine. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• For waveguide resonators a third index is introduced to the mode for wavelengths in the longitudinal direction: I don't follow this at all. I can see that we'd need a third index if we want to identify what's happening longitudinally, but why does that not apply to waveguides that are not resonators? And is it possible to link waveguide resonator to something explanatory? I have enough physics to get an idea of what could be meant here, but this is the first mention of resonance in the article, and it's neither linked nor explained.
  • I've wikilinked cavity resonator which is about the most relevant article we have for that passage. We also have resonator available if a you feel a more general article would be helpful.
  • why does that not apply to waveguides that are not resonators? A signal sent down a properly terminated line will never come back. The length of line is irrelevant; it is always the same result—nothing returns. For a resonator, the line is blocked causing the wave to be reflected back and it is this reflection that sets up the resonance. The length determines the resonant frequency. It's analogous to playing a note by blowing over the top of a bottle. SpinningSpark 18:13, 12 January 2018 (UTC)

    OK; I think the misunderstanding here is just my ignorance of the topic, so I've struck it. The link is helpful. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• The explanation of cutoff frequency seems backwards to me. I think it would be more natural for an uninformed reader to start by saying that multi-mode propagation is possible, but undesirable; then say that each mode has a cutoff frequency, then define dominant mode.
  • I don't agree. Cutoff frequency is an important phenomenon in its own right. It's the essential reason why waveguides are not used at low frequencies. It just so happens that it is also a handy way of suppressing multi-mode mode transmissions.
  • The point that multi-modes are possible should have already been clear before this point in the article. I've added that explicitly to the opening passage of the section. I've also noted that some devices actually make use of more than one mode. SpinningSpark 18:13, 12 January 2018 (UTC)

    That addressed what I was looking for. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• designing the enclosure to be too small to support frequencies as low as the operational frequencies of the circuit: is this the same as saying "...frequencies above the cutoff of the dominant mode"? If so I think it would help to find a way to say "dominant mode" here, in order to help the reader connect the concept from the previous paragraph with this.
  • is this the same as saying "...frequencies above the cutoff of the dominant mode"? No, the dominant mode here is TEM which goes all the way down to zero (DC) so all frequencies are above the cutoff frequency of the dominant mode. The cutoff frequency of the spurious modes has ended up greater than the operational frequency, but it has been done by making the enclosure small. So surely directly saying it is achieved by reducing the size of the enclosure is clearer to the reader. SpinningSpark 19:08, 12 January 2018 (UTC)
• I'm not sure why we mention circular TE and TM modes in coaxial cables at the end of that paragraph, unless it's just an illustrative aside, which is OK. If so, perhaps we could also add whether those modes can be suppressed in coaxial cables?
  • Illustrative aside. I thought the analogy to coax would be helpful because it is easy to imagine the outer conductor of a round cable acting as a circular waveguide. It is not quite so self-evident with planar formats. I've added a note on suppression in coax (at the risk of going too far aside here). SpinningSpark 19:08, 12 January 2018 (UTC)
• Alternatively, TSE{x} etc. can be written as TE{x} etc. to achieve the same result: we haven't used "TSE{x}" up to this point, so I'm not clear what is being explained here.
  • You're right, it's not helpful and I've taken it out. I was just trying to be comprehensive in listing all the alternative notation systems a reader might come across. SpinningSpark 19:45, 12 January 2018 (UTC)
• A general question: why is the description of the formats themselves left so late in the article? As I read I keep wanting to skip forward to find out what is meant by finline or microstrip. I do see that whichever you cover first will lead to questions about the later material, since the discussion of the formats makes reference to concepts currently explained earlier in the article.
  • Honestly, this is the section of this article I have really struggled with. It is much longer than I would like it to be, and you are right, ideally it should be later in the article. It is where it is because the formats all talk about the modes they support so defining mode first makes sense. Possibly, a solution is to move it down and wikilink on first use. Against that, there is the question of whether to wikilink in-article to modes that already have articles. Also, "General properties", "Modes", "Other important parameters" form a logical progression and work together. Even "Substrates" is part of a trans-format description. How does moving the "formats" section to just below "general properties" work for you? SpinningSpark 19:48, 12 January 2018 (UTC)

    After thinking about it I don't think a change is needed. It's a bootstrapping problem; you have to start somewhere, and this organization does work. Mike Christie (talk - contribs - library) 13:39, 13 January 2018 (UTC)

• Is there a possible link for "loss tangent", perhaps to dielectric loss?
  • dielectric loss is already linked and loss tangent merely redirects to it. Although a second link in this case wouldn't hurt. SpinningSpark 19:45, 12 January 2018 (UTC)
• Should "plated through holes" be hyphenated: "plated through-holes"? I see the hyphenation in the target article and it would make it easier to parse for a reader unfamiliar with the term.
  • Don't ask me, I'm no good with things like that. Logically, it makes sense as it is a through hole that has been plated. However, a more common hyphenation (including in the Wikipedia article) is "plated-through hole". Arguably, a hole that has been plated through is also correct. "Plated-through-hole" is also pretty common, as is no hyphenation at all. SpinningSpark 20:57, 12 January 2018 (UTC)

    Striking since it's not an issue for GA. "Plated through-holes" makes the most sense to me, but since there's variation in the literature I won't try to impose a preference. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• FYI, the {{delta}} template, with no parameters, gives a much nicer-looking delta than the default font: δ instead of δ.
  • done.
• Why is the section heading "Suspended stripline" but the related main article "air stripline"? You say "suspended stripline is a type of air stripline"; so there are other types of air stripline?
  • Yes, as the air stripline article explains, there is more than one form. This article concentrates on the printable forms, the overwhelming form used in manufacturing today. Any one of the sections could be expanded with more obscure or historic forms, but the overview article should concentrate on the main forms and let the subsidiary articles deal with some of the less common. SpinningSpark 21:30, 12 January 2018 (UTC)
• The idea of two conductor stripline is to compensate for air gaps between the two substrates: The diagram for stripline makes it seem that the strip conductor is embedded in one of the ground planes so that it is flush with the surface. From that, the description of two conductor stripline made me think it would be stripline in which both ground planes had a strip conductor, flush with the surface. The picture of two conductor stripline shows the conductor is not flush in either ground plane, though. What am I missing?
  • I don't think you can be reading the diagrams right. First of all, the strip is not embedded in the ground plane, it is embedded in the dielectric. See the colour key on the first diagram. Secondly, the usual method of embedding the strip is to make two separate boards with the srip on just one of them, then sandwich them together. The strip is not flush with the surface of either board, but is slightly proud of the one it is printed on, and when fully assembled, proud of the blank one as well. Two conductor stripline has a strip printed on both boards, again both proud of their respective dielectric. SpinningSpark 21:58, 12 January 2018 (UTC)
• The bilateral structure can also be used to couple two independent lines across their broad side. This gives much stronger coupling than side-by-side coupling: I don't understand what's meant by "coupling" here. Is there a linkable article?
  • I've linked coupling (electronics), but not exactly a wonderful article. SpinningSpark 22:17, 12 January 2018 (UTC)
• There's no discussion of B and D in the "Coplanar variants" section.
  • CBCPW is already discussed in the paragraph above. I have added a sentence on embedded coplanar strips. SpinningSpark 00:14, 13 January 2018 (UTC)
• Any reason why there's no diagram for SIW ridge waveguide? You have a diagram for everything else.
  • Partly, it was diagram exhaustion by the time I got to it. An article can become overloaded with diagrams and we can't possibly document the entire zoo of variants in an overview article. Partly, its because the source cited did not provide a diagram to refer to. This would be a subject to expand on if the ridge waveguide article ever gets written. SpinningSpark 00:14, 13 January 2018 (UTC)
• Just checking: is "Jameison" a typo? It's usually "Jamieson".
  • Typo, and there was also a name missing altogether SpinningSpark 00:14, 13 January 2018 (UTC)
• As far as I can see the abbreviation "MIC" used in the history section is not introduced above; similarly for MMIC.
  • They are introduced in the substrates section. SpinningSpark 00:43, 13 January 2018 (UTC)

    Oops. Mike Christie (talk - contribs - library) 13:36, 13 January 2018 (UTC)

• I don't know if the sources have anything to say on this, but it's interesting that imageline was introduced in 1952 but is still "largely experimental".
  • Seems to be one of those things that academics love to play with and write papers on, but it has not caught on with the manufacturers as it doesn't yet work very well in practice. This could well change with the current rapid rise in optical electronics. Its still a developing field and hard to say what direction it will take. But given the heavy investment in planar forms of manufacturing that already exist, some kind of planar format is likely to prove popular through familiarity if nothing else. I might also mention that coaxial cable was invented by Heaviside in 1880 but didn't see any real use until the 1930s. Sometimes it takes a long time for these things to be taken up. SpinningSpark 00:43, 13 January 2018 (UTC)
• related by a reciprocal function: might be simpler to say "inversely related".
  • Done. SpinningSpark 00:43, 13 January 2018 (UTC)

That's everything I can see. Mike Christie (talk - contribs - library) 11:58, 12 January 2018 (UTC)

convenience heading

I'm going to go ahead and pass this for GA; there are a couple of remaining minor points, but they're not issues for GA.

• I think a footnote explaining that the indices are not comma-separated would be helpful.
  • Done with an in-article note. SpinningSpark 14:21, 13 January 2018 (UTC)
• The two-conductor stripline diagrams and the text still seem to me slightly out of sync. (Yes, I forgot the key; I meant dielectric in my comment above.) Your explanation in the notes on this page makes everything clear, but the diagrams are slightly inconsistent with each other and the text doesn't clarify the point I was asking about. In the stripline A diagram the metal line appears to be flush, but at any rate there is certainly no air space between the upper and lower dielectric. In D there's an air gap that is not that different in size from the ones shown in B and C, but the description makes it sound as if the whole point of D is to eliminate air gaps. Based on your comments above I think I now understand what's really going on, but the text and images aren't working together at this point.
• I've redone the diagram to more realistically show the gaps on the D diagram. The diagram is not accurately to scale, it is just a diagram. The strips in reality are much thinner, more like kitchen foil, but have been enlarged to make the structure clear. SpinningSpark 15:17, 13 January 2018 (UTC)

  The revised diagram makes it much clearer; I think that's a big improvement. Mike Christie (talk - contribs - library) 18:28, 13 January 2018 (UTC)

Other than that I think everything is fine; in some cases I misunderstood the article, from a lack of expertise. I hope my ignorance hasn't made this review too painful; thanks for an educational experience. Mike Christie (talk - contribs - library) 13:47, 13 January 2018 (UTC)

Quasi-TEM modes - radiation

This section says that it is an inhomogeneous medium or the consequent quasi-TEM propagation that causes radiation at discontinuities. Of course it is true that microstrip (inhomogeneous) will radiate at discontinuities while stripline (homogeneous) will not. However, stripline can be made with different dielectrics above and below the strip, resulting in quasi-TEM propagation, but it cannot radiate. Furthermore, if the materials in this stripline are lossless, and if the line is nicely via-fenced so that energy cannot escape through other modes, then any discontinuities must present a purely reactive load (by conservation of energy). Conversely, discontinuities in microstip will radiate (a little), even if the substrate dielectric constant is unity.

The section also says that the resistive component of the impedance presented by a discontinuity results in radiation. Radiation is surely a logical consequence of the resistance (if the materials are lossless), but it is like saying that it is the heat in your brake-discs that slows you down - it violates common notions of causality. [Fixed] --catslash (talk) 00:03, 14 January 2018 (UTC)

I agree on the causality issue. The resistance is a measure of the radiation, not the cause of it. What you say on inhomogeneous stripline makes sense, but I would like a reference before changing anything. Modes that cause "sideways" radiation are a known issue in stripline and these too will show up as a resistive element to components. Yes, perfectly fenced stripline cannot radiate. Another case is boxed stripline, also completely shielded. Perhaps the solution is to add the qualifier "...most quasi-TEM..." to indicate there are edge cases without making the modes section more of a tome than it already is. SpinningSpark 16:13, 14 January 2018 (UTC)

Stripline circuit

I just want to respond here to some of the points raised about the striplinemicrostrip circuit in the article at the peer review. This was the lead image, but is currently in the "General properties" section. As I said at the peer review, a detailed description of the minutia of the circuit would be inappropriate. Firstly, because it would be tangential to the article, and secondly because it was uploaded without a detailed description so adding such a description would be WP:OR. But for what it's worth, here is my understanding of the points raised.

• "what are the light vs dark parts? Conductor vs substrate?" In this circuit, the conducting lines are darker than the insulating substrate. The substrate is unusually bright probably because it is a ceramic.
• "What parts are the planar transmission line and what parts are not?" The planar transmission lines are all the dark lines on the ceramic substrates. Everything else is either discrete components or not planar.
• Are the screws important?" I don't believe the screws are important electrically. They are there merely to fix the parts together. Rows of screws or holes often have something to do with screening in circuits such as this (see via fence) but in this case they are a result of the construction of the device. The circuit is built of four separate pieces of ceramic substrate. Underneath the ceramic is another board, probably a more traditional glass-epoxy board. The ceramic substrates are fixed on to the underlying board with clips retained by the screws. It was probably constructed this way because the device is a prototype or one-off. Ceramic is difficult to drill. It needs special drills and takes a long time. Clips are more convenient for a prototype. A production unit would probably be made on a single piece of ceramic with the necessary holes for fixing down.
• "Why are wires mixed in with the planar patterns?" The only wires I'm seeing are in the top left-hand corner. These are providing connections between the planar lines and external connections (mostly power connections, I think). The only other wires I can see are the windings of two very small choke inductors near the transistor.
• "What is the size of the wave relative to the size of planar elements?" The thick line in the centre shaped like half a swastika is a stub bandpass filter. Each arm is likely a half wavelength (since the ends are open circuit rather than short circuit). The absolute size of the wave is not possible to determine without either a scale reference in the picture or knowledge of the operating frequency. However, the whole device is going to be tens of centimetres across.

Hope that's helpful, SpinningSpark 18:05, 1 August 2018 (UTC)

Could the underlying embossed surface be metal? It looks a little shiny and there seems to be a dent in it just above the left-hand board. Also, if it was metal it would provide ground-plane continuity of sorts behind the two bridges linking the lower board.

The stub comprising the top-left limb of the swastika appears to be grounded very close its end, which would modify the response considerably. --catslash (talk) 23:01, 1 August 2018 (UTC)

Well the bottom line is that we have no hard information. I had noticed the grounding link (if that is what it is) but couldn't explain its function. It is reminiscent of impedance matching arrangements used on inverted-F antennae and helical resonators. SpinningSpark 18:45, 2 August 2018 (UTC)

FA preparation

I've finally got back on this one after letting it moulder in the compost heap of my to do list for months. I think I have now addressed all the points that came out of the peer review except for a couple of things. One is field pattern diagrams, which I am working on now. The other was a comment by user:Mark Viking to the effect that "the planar format fits in well with the manufacturing methods" should be replaced by "the planar format is easy to manufacture". I haven't done that because that is not the point, at least, it is not entirely the point. The great advantage of the planar form is it can be made by the same process as a pcb. Components made of planar transmission lines can be made in the same manufacturing step as the pcb traces. Essentially, the cost of these components is zero - or no additional cost. That is more than just being "easy" to make. SpinningSpark 22:17, 28 November 2018 (UTC)