Input arrangement for a low-noise amplifier pair
View Patent ↗An arrangement for processing the antenna signal of a radio receiver and for leading it to low-noise amplifiers LNA of parallel amplifier branches. On the transmission path of the receiver from the antenna to the amplifiers LNA, functionally different elements are combined into physically united elements, such as the conductors ( 432, 433 ) of the low-passing part of the antenna filter and the division conductors of the Wilkinson divider ( 430 ), and the conductor ( 441 ) of the phase-shifter and the inductive part (L 1 ) of the LNA matching circuit. Each physically united element is a conductor, which is insulated from the ground plane by air or a low-loss dielectric material. The arrangement reduces the number of lossy parts between the antenna and the amplifiers, and placing these parts on an ordinary circuit board is also avoided. For these reasons, inferior noise values compared to the prior art can be allowed for each LNA. In addition, the matching of the input impedance of the LNA becomes more accurate when no discrete coil is needed in it.
1. Input arrangement for a low-noise amplifier pair in a front stage of a radio receiver, which comprises as functional units a phase shifter, a first matching circuit and a first LNA belonging to a first amplifier branch, a second matching circuit, a second LNA and a second phase shifter belonging to the second amplifier branch, a bandpass filter, a low-pass filter, a divider, wherein on transmission path of the front stage from antenna to the first and the second LNA, at least parts belonging to a first and a second functional unit are physically united to a single element to reduce attenuation caused by said transmission path and to improve matching.
2. An arrangement according to claim 1 , where the divider is a Wilkinson type divider, which has an input line comprising an input conductor and a ground conductor, or ground, and a first and a second division line, each of which comprises a division conductor and ground conductor, the first functional unit being said low-pass filter and the second functional unit being said divider, in which case each division line of the divider is a low-pass filter at the same time.
3. An arrangement according to claim 2 , where the phase shifter is a transmission line comprising an upper conductor and a ground conductor, and the first matching circuit is implemented by an inductive element and, in addition, some parts belonging to a third and a fourth functional unit are physically united to a single element, which third functional unit is said phase shifter and the fourth functional unit is said first matching circuit, in which case the upper conductor and the inductive element form a united element.
4. An arrangement according to claim 3 , at least some of said conductors being micro strips on a surface of a relatively low-loss dielectric board.
5. An arrangement according to claim 2 , wherein, to form said low-pass filter, a division conductor comprises a conductor extending from its input to the output, the substantial characteristic of which is its inductance, and transverse enlargements of this conductor, the substantial characteristic of which is their capacitance in relation to the ground.
6. An arrangement according to claim 2 , said input conductor and division conductors being conductor strips substantially air-insulated from the signal ground.
7. An arrangement according to claim 2 , at least some of said conductors being micro strips on a surface of a relatively low-loss dielectric board.
8. An arrangement according to claim 1 , where the phase shifter is a transmission line comprising an upper conductor and a ground conductor, and the first matching circuit is implemented by an inductive element, the first functional unit being said phase shifter and the second functional unit being said first matching circuit, in which case the upper conductor and the inductive element form a united element.
9. An arrangement according to claim 8 , said united element formed by the upper conductor and the inductive element being a conductor strip substantially insulated from the signal ground.
10. An arrangement according to claim 8 , at least some of said conductors being micro strips on a surface of a relatively low-loss dielectric board.