Amplifier in doherty configuration comprising a device for varying the working frequency and method thereof

An amplification system comprising:

• one or more circuits housing one or more respective amplifiers adapted to amplify one same signal,
• wherein the outputs of said amplifiers are combined together in order to increase the gain of said amplification system, and
• wherein said outputs of said amplifiers travel over a single delay line consisting of a constant-impedance transmission line, thereby allowing the operating frequency of said amplification system to be adjusted by acting upon a single adjustment point, said amplification system further comprising a device adapted to vary the electric length of said transmission line,
• wherein said device comprises a metallic body with an outer wall and an inner wall adapted to define a cavity, said walls being interrupted in a manner such as to define a slot, said cavity and said slot extending along at least a portion of the length of said device,
• wherein said cavity comprises a first portion having a first cross-section and a second portion having a second cross-section which is greater than said first cross-section, said second portion comprising a dielectric element with a cutout corresponding to said slot, said first and second portions extending in the longitudinal direction of said device and said transmission line being provided, inside said first portion and inside said second portion, in said cutout of said dielectric element, said dielectric element being adapted to occupy the cavity of said second portion, and comprising translating means integral with said metallic body and adapted to translate said dielectric element on said circuit in the longitudinal direction of said device.

A method for varying the operating frequency of an amplifier in Doherty configuration comprising:

• a circuit having a delay line consisting of a constant-impedance transmission line and a device adapted to vary the electric length of said transmission line, said method comprising:
• positioning said transmission line into a cavity of a device comprising a metallic body with an outer wall and an inner wall adapted to define said cavity, said walls being interrupted in a manner such as to define a slot, said cavity and said slot extending along at least a portion of the length of said device,
• wherein said cavity comprises a first portion having a first cross-section and a second portion having a second cross-section which is greater than said first cross-section, said second portion comprising a dielectric element with a cutout corresponding to said slot, said first and second portions extending in the longitudinal direction of said device and said transmission line being provided, inside said first portion and inside said second portion, in said cutout of said dielectric element, said dielectric element being adapted to occupy the cavity of said second portion;
• translating said device on said circuit in the direction of its length through translating means integral with said metallic body, so as to obtain the desired operating frequency.