Distributed logarithmic amplifier and method

A logarithmic amplifier having at least one stage comprising:

• a substrate having a principal surface with first and second opposed ends and first and second sides extending between the ends;
• a first transmission line extending at least part way between the ends with an input located in proximity to the first end, wherein the first transmission line is located approximately centrally between the sides and has multiple nodes spaced apart there along;
• second and third transmission line extending at least part way between the ends having combined outputs located in proximity to the second end, wherein the second transmission line is located in proximity to a first side and the third transmission line is located in proximity to the second side and wherein the second and third transmission lines have multiple nodes spaced apart there along;
• amplifier elements spaced apart longitudinally along the substrate between the ends and coupled transversely between the first transmission line and the second transmission lien and between the first transmission line and the third transmission line, each element of a first portion of the amplifier elements being coupled between a node of the first transmission line and a node of the second transfusion line, and each element of a second potion of the amplifier elements being coupled between a node of the first transmission line and anode of the third transmission line, and wherein transconductances of some of the first and second portions of the amplifier elements are not substantially the same.

A monolithic logarithmic amplifier comprising:

• a semiconductor substrate having opposed ends and opposed sides extending between the ends
• a first transmission line means on the substrate and having an input for receiving a signal to be logarithmically amplified and comprising lumped elements having N nodes spaced apart along a first line extending part way between the ends of the substrate, wherein the first line divides the substrate into two portions, a first portion lying on a first side of the first line and a second portion lying on a second side of the first line;
• a second transmission line means on the substrate and having an output and comprising lumped elements with N nodes spaced apart along a second line extending part way between the ends of the substrate, wherein the second line is located on the first portion of the substrate;
• a third transmission line means on the substrate and having an output and comprising lumped elements with N nodes spaced apart along a third line extending part way between the ends of the substrate, wherein the third line is located on the second portion of the substrate;
• N amplifying elements coupled between nodes of the first and second transmission lines, a first of the N amplifying elements being coupled between a first node of the first transmission line and a first node of the second transmission line, a second of the N amplifying elements being coupled between a second node of the first transmission line and a second node of the second transmission line, and the Nth of the N amplifying element being coupled between the Nth node of the first transmission line and the Nth node of the second transmission line;
• N other amplifying elements coupled between nodes of the first and third transmission lines, a first of the N other amplifying elements being coupled between a first node of the first transmission line and a first node of the third transmission line, a second of the N other amplifying elements being coupled between a second node of the first transmission line and a second node of the third transmission line, and the Nth of the N other amplifying element being coupled between the Nth node of the first transmission line and the Nth node of the third transmission line;
• combiner means having an output from whence a logarithmic output signal is obtained and having a first input coupled to the output of the second transmission line and a second input coupled to the output of the third transmission line;
• and
• wherein at least some of the N amplifying elements coupled to nodes of the first transmission line have different gains and compressions than the corresponding other amplifying elements coupled to the same nodes of the first transmission line.

A method for logarithmically amplifying signals comprising:

• providing an input signal to an input transmission line having nodes sequentially distributed there along;
• coupling a portion of the input signal appearing at sequential nodes of the input transmission line to input of first and second sets of multiple amplifying elements to be amplified and appear at outputs of the multiple amplifying elements wherein signal appearing at outputs of the first set of multiple amplifying elements are coupled to spaced apart nodes of a first output transmission line and signals appearing at outputs of the second set of multiple amplifying elements are coupled to spaced apart nodes of a second output transmission line, so that signals passing through the input transmission line, the first set of multiple amplifying elements and the first output transmission lien experience low gain and high compression and so that signals passing through the input transmission line, the second set of multiple amplifying elements and the second output transmission line experience high gain and low compression;
• coupling signals appearing at the output of the first transmission line to a first input of a combiner, wherein the combiner has an output port and coupling signals appearing at the output of the second transmission line to a second input of the combiner;
• and
• extracting the logarithmically amplified signal at the combiner output port.