Need Some basic information about waveguides

[Ejaz484]

Hi,
Iam designing a rectangular waveguide for signal propagation in Q-band. In that will it be any difference if i connect my WR-22 wave guide to multi hole coupler as the front view shown in below pic



Will there will be any difference in propagation of signal in both the cases??

I know that width should be double of the breadth of waveguide. But here will it makes any difference??

 

[jiripolivka]

The wr-22 waveguide covers 33 to 50 GHz band which is named Q-band. I do not understand the picture you show. The multi-hole couplers have the coupling holes in the wider guide sides (or narrow sides) but I do not know the arrangement shown in your picture.

Both waveguides must use TE10 propagation mode which is dominant. Typical standard waveguides do use the width twice the height but in couplers this may change. The height affect waveguide impedance, the bandwidth is given by the width.

 

[Ejaz484]

Actuyally what I mean is, Iam having a circular multi-hole coupler with 6 holes long the axial line of direction of propagation of RF signal. I want to connect this WR-22 at those holes. Can u tell which can be the best method to connect it. In that fig. I showed two ways to connect WR-22 to that multi hole couple output. One is WR-22 width along the axis and other its height along the axis(rotating case 1 90 deg)

And one more think I want to know. The diameter of each hole of multi hole coupler is 1mm. So what frequency range of signals can be transmitted to that hole. Can u please give me relation between the diameter of hole and its transmitting frequency range?

And how the distance between the two holes will matter in that multi hole coupler. By my understanding it is for selecting different modes of transmitting RF signal. If I am wrong can u please tell me the correct relation??

 

[jiripolivka]

Actuyally what I mean is, Iam having a circular multi-hole coupler with 6 holes long the axial line of direction of propagation of RF signal. I want to connect this WR-22 at those holes. Can u tell which can be the best method to connect it. In that fig. I showed two ways to connect WR-22 to that multi hole couple output. One is WR-22 width along the axis and other its height along the axis(rotating case 1 90 deg)

And one more think I want to know. The diameter of each hole of multi hole coupler is 1mm. So what frequency range of signals can be transmitted to that hole. Can u please give me relation between the diameter of hole and its transmitting frequency range?

And how the distance between the two holes will matter in that multi hole coupler. By my understanding it is for selecting different modes of transmitting RF signal. If I am wrong can u please tell me the correct relation??

I have used many wideband couplers, mostly 10-dB, but I have not designed any particular one.
Please refer to Matthaei, Young, Jones: Microwave filters and couplers, an excellent design book.
Wideband couplers I know were multi-hole type but hole diameters varied along the device. Some used elliptical holes etched in a foil making the coupling thin wall between the guides.

Typically, hole diameter, number and distance determines the value of coupling loss and directivity. In low-coupling loss couplers (3...7 dB), there is even a long narrow slot in the coupling wall.

To my knowledge, designing a good waveguide coupler is quite tricky. This is why good ones are sold for a reasonable price. Check e.g. Aerowave, Agilent and Cernex for good couplers.