WM490
The Tektronix WM490 is a series of waveguide mixers for 490-series spectrum analyzers, e.g., the 7L18, 492, and 494.
As described in Spectrum Analysis Utilizing Waveguide Mixers, the application note 26W-5360 states that whether a measurement is made at audio frequencies or millimeter wavelengths, the spectrum analyzer is used to measure amplitude vs. frequency. Typical measurements include spectral energy distribution or signature of the energy source. This can be as simple as measuring harmonic levels of a continuous wave source to a more complicated occupied bandwidth measurement of a digital microwave transmission system.
Actual spectrum analyzer measurements at millimeter wavelengths differ from lower frequency measurements in the transition from coaxial cables to waveguides. Most spectrum analyzers have an internal mixer upper frequency limit of 21 to 22 GHz, and utilize a type "N" RF input connector.
When the requirement measurement is above 22 GHz, some type of external mixing is required. Current techniques utilize harmonics of the spectrum analyzer first sweeping LO and an external harmonic waveguide mixer covering the designer frequency range. The mixers extend the frequency range of measurement up to as high as 325 GHz. Each mixer covers a separate frequency range, typically about two thirds of an octave.
Note: The MIL-F-39000/3C which describes flanges for double-ridge waveguide was cancelled without replacement on January 20, 2009.
| Model No. | Band Desig. | Freq Range (GHz) | Waveguide (EIA) | U-Type Flanges |
|---|---|---|---|---|
| WM490K | K | 18.8 to 26.5 | WR-42 | UG-595/U |
| WM490A | A | 26.5 to 40 | WR-28 | UG-599/U |
| WM490Q | Q | 33 to 50 | WR-22 | UG-383/U |
| WM490U | U | 40 to 60 | WR-19 | UG-383/U-M |
| WM490V | V | 50 to 75 | WR-15 | UG-385/U |
| WM490E | E | 60 to 90 | WR-12 | UG-387/U |
| WM490W | W | 75 to 110 | WR-10 | UG-387/U-M |
| WM490F | F | 90 to 140 | WR-08 | UG-387/U-M |
| WM490D | D | 110 to 170 | WR-06 | UG-387/U-M |
| WM490G | G | 140 to 220 | WR-05 | UG-387/U-M |
| 119-1728-00 *1 | J | 220 to 325 | WR-05 / WR-03 | 74-003 / 74-005 |
Notes: *1: G-J Band flange transition
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Specs of WM490 Mixers with 494
