A Dual-polarized Broadband Planar Antenna and Channelizing Filter Bank for Millimeter Wavelengths

TL;DR

This paper presents a broadband dual-polarized planar antenna with integrated channelizing filters for millimeter wavelengths, enabling simultaneous multi-band and polarization measurements crucial for astrophysical observations.

Contribution

The work introduces a novel antenna and filter bank architecture that achieves broad bandwidth, polarization separation, and multiple sub-bands in a compact design for millimeter-wave astronomy.

Findings

Achieved 20-40% receiver efficiency.

Demonstrated high polarization isolation.

Successfully integrated multiple sub-bands with accurate positioning.

Abstract

We describe the design, fabrication, and testing of a broadband log-periodic antenna coupled to multiple cryogenic bolometers. This detector architecture, optimized here for astrophysical observations, simultaneously receives two linear polarizations with two octaves of bandwidth at millimeter wavelengths. The broad bandwidth signal received by the antenna is divided into sub-bands with integrated in-line frequency-selective filters. We demonstrate two such filter banks: a diplexer with two sub-bands and a log-periodic channelizer with seven contiguous sub-bands. These detectors have receiver efficiencies of 20-40% and percent level polarization isolation. Superconducting transition-edge sensor bolometers detect the power in each sub-band and polarization. We demonstrate circularly symmetric beam patterns, high polarization isolation, accurately positioned bands, and high optical efficiency. The pixel design is applicable to astronomical observations of intensity and polarization at millimeter through sub-millimeter wavelengths. As compared with an imaging array of pixels measuring only one band, simultaneous measurements of multiple bands in each pixel has the potential to result in a higher signal-to-noise measurement while also providing spectral information. This development facilitates compact systems with high mapping speeds for observations that require information in multiple frequency bands.