Greetings Everyone!
Can anyone provide a formula for the transmission loss of a waveguide at frequencies BELOW it's normally useful range? I would like to construct a high-pass filter to reject the fundamental frequency of a transmitter, but allow the passage of the second and higher harmonics. I am assuming a coax transmitter output, with the coax connected to a 6dB attenuator and then a coax/waveguide transition. Then a section of straight waveguide, perhaps 18" long, followed by another waveguide/coax transition. The coax would then be connected to an attenuator and a spectrum analyzer. (The purpose of the 6dB attenuator is to limit fundamental power reflected to the transmitter to a maximum of 10% of the forward power. At the fundamental, the waveguide should yield a terrible impedance discontinuity, reflecting most of the forward power.) If I choose a waveguide which would normally just support the relatively lossless transmission of the second harmonic, how many dB of loss could I expect at 1/2 the second harmonic frequency (the fundamental frequency)? The variables which I would know are the frequencies involved, the physical width and height of the waveguide, and the length of the waveguide. A second question would be what is the effect of the length of the waveguide? Do I only need to provide a certain minimum length, or will loss be strongly proportional to waveguide length? Is it possible that the coax/waveguide transitions alone will provide enough waveguide length? To give you a better perspective, imagine that a 4.5 GHz 100 Watt transmitter is connected to X-band (WR-90 guide? normally used from 8 GHz to 12.5 GHz) waveguide. What would the transmission loss be at 4.5, 5, 6, 7, 8, and 9GHz? Thanks in Advance, Ed -------------------------- Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: [email protected] Date: 09/25/1998 Time: 09:29:20 -------------------------- --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
