Low loss radio frequency time delay arrangements

1 . An apparatus, comprising:

radio frequency (RF) switches mounted to a circuit board substrate and having RF connections to an RF input and an RF output;

tiers of the RF switches coupled in a cascaded mirrored pair arrangement for RF delay lines coupled as an array of selectable time delays;

the RF delay lines comprising conductive trace segments formed external to the RF switches and located underneath footprints of the RF switches on internal layers of a stackup of the circuit board substrate, and comprising vias at ends of the conductive trace segments that couple vertically through the stackup to connect to pads that mount to the RF connections of the RF switches; and

the stackup comprising the internal layers housing the conductive trace segments bounded by electrical ground layers.

2 . The apparatus of claim 1 , wherein a first tier of the RF switches are coupled in a mirrored pair arrangement to select among first RF delay lines;

wherein a second tier of the RF switches are coupled in the mirrored pair arrangement to select among second RF delay lines.

3 . The apparatus of claim 2 , wherein tier coupling RF switches in the cascaded mirrored pair arrangement comprise one among the first tier of the RF switches and one among the second tier of the RF switches.

4 . The apparatus of claim 1 , wherein the tiers of the RF switches comprise two ranks of the RF switches, with a first rank coupled through corresponding RF delay lines to a second rank.

5 . The apparatus of claim 4 , wherein tier coupling RF switches establish the cascaded mirrored pair arrangement by at least providing:

selectable connections between the RF input and the first rank of the RF switches;

selectable connections between the RF output and the second rank of the RF switches; and

selectable couplings among any of the RF switches of the second rank and any of the RF switches first rank.

6 . The apparatus of claim 1 , wherein the substrate comprises at least one among a glass-ceramic substrate and liquid crystal polymer substrate.

7 . The apparatus of claim 1 , wherein the RF switches comprise single-pole four-throw (SP4T) RF switches.

8 . The apparatus of claim 1 , wherein the RF switches comprise micro-electromechanical systems (MEMS) switches.

9 . A method, comprising:

coupling radio frequency (RF) switches to a circuit board substrate and having RF connections to an RF input and an RF output; and

providing tiers of the RF switches coupled in a cascaded mirrored pair arrangement for RF delay lines coupled as an array of selectable time delays;

forming the RF delay lines comprising conductive trace segments external to the RF switches and located underneath footprints of the RF switches on internal layers of a stackup of the circuit board substrate, and comprising vias at ends of the conductive trace segments that couple vertically through the stackup to connect to pads that mount to the RF connections of the RF switches; and

forming the stackup comprising the internal layers housing the conductive trace segments bounded by electrical ground layers.

10 . The method of claim 9 , comprising:

coupling a first tier of the RF switches in a mirrored pair arrangement to select among first RF delay lines;

coupling a second tier of the RF switches in the mirrored pair arrangement to select among second RF delay lines.

11 . The method of claim 10 , wherein tier coupling RF switches in the cascaded mirrored pair arrangement comprise one among the first tier of the RF switches and one among the second tier of the RF switches.

12 . The method of claim 9 , wherein the tiers of the RF switches comprise two ranks of RE switches, with a first rank coupled through corresponding RF delay lines to a second rank.

13 . The method of claim 12 , comprising:

establishing the cascaded mirrored pair arrangement by at least:

providing selectable connections between the RF input and the first rank of the RF switches;

providing selectable connections between the RF output and the second rank of the RF switches; and

providing selectable couplings among any of the RF switches of the second rank and any of the RF switches first rank.

14 . A system, comprising:

a multi-layer circuit board having footprints on a surface configured to carry radio frequency (RF) switches, with internal layers of the circuit board housing routed RF delay lines interspersed with electrical ground layers;

the RF switches arranged in a cascaded mirrored pair arrangement with RF connections that form a pathway between an RF input and an RF output by at least selecting among ones in an array of the RF delay lines; and

the RF delay lines comprising conductive trace segments formed external to the RF switches and located underneath footprints of the RF switches on the internal layers, and comprising vias at ends of the conductive trace segments that couple vertically through the multi-layer circuit board to connect to ones of the footprints that mount to the RF connections of the RF switches.

15 . The system of claim 14 , wherein first RF switches providing a first tier of RF delay lines are coupled in the cascaded mirrored pair arrangement;

wherein second RF switches providing a second tier of RF delay lines are coupled in the cascaded mirrored pair arrangement; and

wherein at least two RF switches selectively couple outputs of the first RF switches to inputs of the second RF switches to form a series coupling of tiers in the cascaded mirrored pair arrangement.

16 . The system of claim 14 , wherein the multi-layer circuit board comprises at least one among a glass-ceramic substrate and liquid crystal polymer substrate; and

wherein the RF switches comprise micro-electromechanical systems (MEMS) switches.