Filter with electrically adjustable attenuation characteristic

A filter for selectively passing a passband of radio frequency signals, comprising:

• at least two reactively coupled coaxial resonators having inner and outer conductors,
• tuning means coupled to the inner conductor of at least one of said resonators for adjusting the range of frequencies passed by the filter,
• means for applying a control signal to said tuning means;
• and
• reactive means coupled to at least one of said resonators for attenuating over a range of frequencies outside the passband wherein the range of frequencies passed by the filter is adjusted by said tuning means in response to the control signal applied thereto.

A filter for selectively attenuating a range of radio frequency signals, including

• at least two inductively coupled coaxial dielectric resonators comprising inner and outer conductors,
• tuning means coupled to the inner conductor of at least one of said resonators for adjusting the range of frequencies attenuated by the filter, and
• means for applying a control signal to said tuning means,
• wherein the range of frequencies attenuated by the filter is adjusted by said tuning means in response to the control signal applied thereto.

A filter for selectively passing a passband of radio frequency signals, comprising:

• at least two reactively coupled coaxial dielectric resonators comprising inner and outer conductors;
• tuning means coupled to the inner conductor of at least one of said resonators for adjusting the range of frequencies passed by the filter;
• means for applying a control signal to said tuning means;
• and
• reactive means coupled to at least one of said resonators for attenuating over a range of frequencies outside the passband wherein the range of frequencies passed by the filter is adjusted by said tuning means in response to the control signal applied thereto.