Low Phase Shift, High Frequency Attenuator

A radio frequency attenuator circuit including:

• (a) an In port and an Out port;
• (b) a bypass path coupled to the In port and the Out port, and including a plurality of serially-connected first distributed transmission line elements, and a plurality of first shunt switches each having an OFF capacitance COFF and each coupled between a respective one of the plurality of first distributed transmission line elements and a reference voltage;
• and
• (c) at least one attenuation path coupled to the In port and the Out port, each attenuation path including a plurality of serially-connected second distributed transmission line elements, a plurality of second shunt switches each having an OFF capacitance COFF and each coupled between a respective one of the plurality of second distributed transmission line elements and the reference voltage, and at least one attenuator element serially connected to the plurality of second distributed transmission line elements;
• wherein the first distributed transmission line elements are configured to essentially tune out the OFF capacitances COFF of the plurality of first shunt switches and the second distributed transmission line elements are configured to essentially tune out the OFF capacitances COFF of the plurality of second shunt switches.

A method for attenuating a radio frequency, including:

• (a) providing a circuit with an In port and an Out port;
• (b) providing a bypass path coupled to the In port and the Out port, and including a plurality of serially-connected first distributed transmission line elements, and a plurality of first shunt switches each having an OFF capacitance COFF and each coupled between a respective one of the plurality of first distributed transmission line elements and a reference voltage;
• and
• (c) providing at least one attenuation path coupled to the In port and the Out port, each attenuation path including a plurality of serially-connected second distributed transmission line elements, a plurality of second shunt switches each having an OFF capacitance COFF and each coupled between a respective one of the plurality of second distributed transmission line elements and the reference voltage, and at least one attenuator element serially connected to the plurality of second distributed transmission line elements;
• wherein the first distributed transmission line elements are configured to essentially tune out the OFF capacitances COFF of the plurality of first shunt switches and the second distributed transmission line elements are configured to essentially tune out the OFF capacitances COFF of the plurality of second shunt switches.

A radio frequency attenuator circuit including:

• (a) an In port and an Out port;
• (b) a bypass path including (i) a plurality of serially-connected first distributed transmission line elements, each first distributed transmission line element having an associated first shunt switch having an OFF capacitance and being configured for selectively coupling its associated first distributed transmission line element to a reference voltage, and (ii) first and second quarter-wave transmission line elements respectively coupled between the plurality of first distributed transmission line elements and the In and Out ports;
• and
• (c) at least one attenuation path, each attenuation path including (i) a plurality of serially-connected second distributed transmission line elements, each second distributed transmission line element having an associated second shunt switch having an OFF capacitance and being configured for selectively coupling its associated second distributed transmission line element to a reference voltage, (ii) at least one attenuator element serially connected to the plurality of second distributed transmission line elements, and (iii) first and second quarter-wave transmission line elements respectively coupled between the plurality of second distributed transmission line elements and the In and Out ports;
• wherein each first distributed transmission line element is configured to tune out the OFF capacitance of its associated first shunt switch and each second distributed transmission line element is configured to tune out the OFF capacitance of its associated second shunt switch.