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RF Components: Equalizers

Understanding Linear Slope Equalizers

NEGATIVE SLOPE: Attenuation decreases linearly with frequency. (See Fig. #1.) Negative Slope Equalizers are primarily used for compensating the gain slope in systems where large amounts of cabling may cause excessive loss at higher frequencies over the operating band. Refer to the coaxial cable manufacturers' specifications for attenuation v/s frequency curves, as it applies to a particular system's accumulative cable length.

POSITIVE SLOPE: Attenuation increases linearly with frequency. (See Fig. #2.) Positive Slope Equalizers are primarily used for compensating the gain variation in systems where long lengths of waveguide may cause excessive loss at the lower frequencies.

HOW TO SPECIFY: Certain parameters must be defined prior to ordering these equalizers. The following is a listing of those parameters along with a brief definition and a method for determining your specifications.

ATTENUATION: Does the maximum attenuation occur at the lowest or highest operating frequency? This will determine whether the slope is negative or positive. This parameter must be specified.

INSERTION LOSS: (See Figures #1 and #2.) The insertion loss of these devices is the sum of both absorptive and reflective losses measured at the frequency opposite that of maximum attenuation. This parameter is specified as a maximum and is referred to as the relative zero attenuation point. Therefore, the specified attenuation level is relative to the insertion loss. A typical method for approximating insertion loss would be to take 10% of the maximum attenuation and add 0.25 dB to that value. For example, if specifying insertion loss of a 10 dB Negative Slope Equalizer, the approximate level of insertion loss would be 1.25 dB maximum, at the highest operating frequency. In most cases it will be less than the approximated value.

VSWR: This parameter is dependent on many factors such as attenuation level, number of sections, bandwidth, operating frequency range, size, configuration, and adjustability requirements; however, input and output VSWR's under most circumstances, should not exceed 2:1.

LINEARITY: Linearity is defined as the deviation in dB from the best fit straight line through the measured curve. This deviation is generally less than ±7% of the maximum attenuation level. For example, if specifying linearity of a 10 dB octave bandwidth Negative Slope Equalizer, the approximate linearity envelope would be ±0.7dB. This may vary slightly with bandwidth and frequency.

ADJUSTABILITY: MICA can provide user-friendly adjustments which will allow you to vary the maximum attenuation. This adjustment range is typically specified as ±15% of the maximum attenuation level. For example, with a maximum attenuation of 1.0 dB adjustability would be 8.5-11.5 dB. Extended adjustability can be established; however, some tradeoffs such as degradation in VSWR and linearity may be necessary. A special feature which will allow adjustment for maximum attenuation to relative zero can also be provided on a limited basis.

CONNECTORS: MICA provides SMA (F) as standard connectors, but other SMA series connectors can be provided on request. TNC and type "N" connectors are not recommended, but can be made available depending on your performance requirements and standard waveguide bands. (Specify flange type when ordering.)

SIZE: Design and size criteria can only be established after determination of all applicable specifications and can then be quoted and outline drawings provided for a detailed mechanical layout.

ATTENUATION LEVEL: Available from 0.5 dB to 40 dB.

FIXED TUNE: These equalizers can be preset and sealed at the factory when field adjustment is not required.

FIELD ADJUSTABILITY: Attenuation can be made adjustable to compensate for system level variations. Adjustability levels are typically ± 15% of nominal setting.

POSITIVE SLOPE OPTIONS: Same as that for the Negative Slope Equalizers; however, the maximum attenuation will occur at the highest operating frequency. (See Fig. #2)
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