Agilent 1955-01 free download

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HEWLETT-PACKARD JOURNAL TECHNICAL INFORMATION FROM THE -hp- LABORATORIES Vol. 6 No. 5 BLISHED BY THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA JANUARY, 1955 A Precision Wave Guide Attenuator Which Obeys a Mathematical Law FOR about a year and a half -hp- has been which collectively cover the range from 3.95 manufacturing a new type of direct-reading to 18 kmc. precision wave guide attenuator known as a Basically, the attenuator consists of three sec rotary attenuator*. This device is distinguished tions of wave guide in tandem. In each section a by the fact that its attenuation follows a predict resistive film is placed across the guide as shown able, mathematical law not re in Fig. 2. The middle section is a short length of lated to frequency. Other than round guide which is free to rotate axially with the cutoff attenuator which has respect to the two fixed end sections. The end several disadvantages in wave sections are rectangular-to-round wave guide guide use, this rotary attenuator is generally con transitions in which the resistive films are nor sidered to be the most accurate attenuator avail mal to the E field of the applied wave. The con able for wide band microwave applications. struction is symmetrical and the device is bi The attenuator has a calibrated range of 0 to directional. 50 db which is accurate within 2% of the db read When all films are aligned, the E field of the ing at any frequency in a wave guide band. This applied wave is normal to all films. No current accuracy is obtained directly from the calibrated then flows in the films, and no attenuation oc dial; no calibration charts are required. The curs. If the center film is now rotated to some VS WR of the attenuator is less than 1.15 and the angle 0, the E field can be considered to be split insertion loss is less than 1 db. into two components: E sin 9 in the plane of the Until recently, the rotary attenuator has been film, and E cos 9 at right angles to it. The E sin 9 produced only in 8.2-12.4 kmc