  We present the design, fabrication and measured performance of a hierarchical
sinuous-antenna phased array coupled to superconducting transition-edge-sensor
(TES) bolometers for millimeter wavelengths. The architecture allows for
dual-polarization wideband sensitivity with a beam width that is approximately
frequency-independent. We report on measurements of a prototype device, which
uses three levels of triangular phased arrays to synthesize beams that are
approximately constant in width across three frequency bands covering a 3:1
bandwidth. The array element is a lens-coupled sinuous antenna. The device
consists of an array of hemispherical lenses coupled to a lithographed wafer,
which integrates TESs, planar sinuous antennas and microwave circuitry
including band-defining filters. The approximately frequency-independent beam
widths improve coupling to telescope optics and keep the the sensitivity of an
experiment close to optimal across a broad frequency range. The design can be
straightforwardly modified for use with non-TES lithographed cryogenic
detectors such as kinetic inductance detectors (KIDs). Additionally, we report
on the design and measurements of a broadband 180-degree hybrid that can
simplify the design of future multichroic focal planes including but not
limited to hierarchical phased arrays.
