IEEE Standard for Rectangular Metallic Waveguides and Their Interfaces for
Frequencies of 110 GHz and Above Part 1: Frequency Bands and Waveguide
Dimensions Part 2: Waveguide Interfaces
Work-to-date on choosing frequency bands and waveguide dimensions
At the P1785 Working Group meeting in Boston, MA, in June 2009, a subgroup was formed and tasked to look into potential series of frequency bands and waveguide dimensions for use in the IEEE standard being developed by the P1785 Working Group.
This subgroup communicated regularly (by email and teleconference) over a period of six months or so. The subgroup developed a series of potential schemes and a series of metrics to assess these schemes. These metrics were grouped under the headings “frequency bands”, “waveguide dimensions” and “related quantities”, as follows:
The frequency bands (i.e. the suggested lower and upper frequencies of each waveguide band) should:
Be memorable (i.e. use whole numbers);
Form two contiguous interleaved series (i.e. should not contain gaps or overlaps in the frequencies covered by each series);
Be easily extendable from lower frequencies to higher frequencies (i.e. mapping from one decade to the next);
Agree with the existing values for WR-10 to WR-03, as given in the MIL standard .
It was agreed that a ratio of 2:1 would be used to describe the relationship between the waveguide aperture width and height (i.e. the ratio of the broad- to narrow-wall dimensions). Therefore, it was only necessary to define the waveguide broad-wall dimension (called the ‘width’, by convention). The waveguide widths should:
Where appropriate, be effectively identical (within stated tolerances) to sizes WR-10 to WR-03, as given in the MIL standard );
Where appropriate, be very similar to sizes WR-2.8 to WR-1.0, as given in ;
In addition to the above, the waveguide scheme should provide, for all bands:
Relatively uniform fractional bandwidths;
Approximately constant k-factors (where k1 ≈ 1.25 and k2 ≈ 1.90); These k-factors are the multipliers used to establish the suggested minimum frequency, fmin, and maximum frequency, fmax, from the cutoff frequency, fc, for each waveguide band: fmin = k1 × f0; fmax = k2 × f0.
Similar ratios of cut-off frequencies (or, equivalently, waveguide widths) for adjacent bands.
The outcome from using these metrics to assess the potential schemes was that a short-list of three candidate schemes were identified and presented subsequently to the P1785 Working Group for discussion, followed by a vote. The outcome of the vote was that a preferred scheme has now been provisionally selected. A narrative summary of the Preferred Scheme and the other two short-listed schemes is given at:
There is also a spreadsheet that shows the performance of each scheme against the listed metrics. A paper  that gives a review of this overall process is also available.
Comments are now being invited on these three waveguide schemes. A survey has been set up to capture these comments. However, comments should be sent before 20th May 2010 since the P1785 Working Group will make a final decision on whether to accept the Preferred Scheme soon after this date.