These are typically arrays of “drop-in” filters, pre- and post-selected by PIN diode switch modules. Such switched filter packages may contain TTL compatible drivers or BCD decoders.
Representative specifications are:
Amplitude equalizers are lossy bandstop filters. Such filters are intentionally “Q-spoiled” to reduce the midband rejection to 5 to 10db. Thus, the equalizer presents a transfer function opposite in amplitude to that of an amplifier or bandpass filter. The equalizer also maintains a low VSWR over the entire band due to its absorptive characteristic.
Delay equalizers consist of coupled arrays of cavities or resonant networks connected to add delays “bumps” at certain points in a passband while not affecting the amplitude flatness. At low frequencies, the equalizers are bridged-tee LC circuits which are connected in series with the filter to be equalized.
Typical amplitude equalizer specifications are:
Our mechanically tunable bandpass and bandstop filters come in many version. At frequencies below 6 GHz, they are typically coupled coaxial cavities with a mechanically movable tuning spindle. Above 6 GHz, most units are coupled cylindrical cavities operating in a waveguide mode. Tuning is accomplished with a movable plunger. Most units are gang-tuned, gear coupled to a common shaft. Filters can be provided with direct-reading tape readouts, micrometers or calibration charts. Some coaxial units are available which tune with constant passband width.
Typical specifications are:
Isofilters are evanescent bandpass filters with isolators on input or output. Through this means, the filter presents a low VSWR even in the stopband region. We employ a technique whereby the filter is “plugged” into an isolator, thus avoiding the parasitic length between the two components.
A representative unit has the following characteristics:
