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arxiv: 2606.25637 · v1 · pith:T3MVZWO7new · submitted 2026-06-24 · 🌌 astro-ph.IM

A Wideband Millimeter-wave Receiver at 120-350 GHz for LMT-FINER

Haoran Kang , Takafumi Kojima , Takeshi Sakai , Yoichi Tamura , Shun Ishii , Akio Taniguchi , Masato Hagimoto , Masato Kato
show 4 more authors
Taku Nakajima Tai Oshima Sho Masui Issei Watanabe
This is my paper

Pith reviewed 2026-06-25 20:13 UTC · model grok-4.3

classification 🌌 astro-ph.IM
keywords wideband receiverSIS mixermillimeter-wavesideband separationnoise temperatureFINERspectral scanning
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The pith

The 210-350 GHz receiver for FINER achieves approximately 100 K single-sideband noise temperature over most of the band in laboratory tests.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper presents the initial laboratory characterization of the 210-350 GHz receiver developed for the Far-Infrared Nebular Emission Receiver project on the Large Millimeter Telescope. The receiver employs high-critical-current-density superconductor-insulator-superconductor mixer technology to deliver a wide intermediate-frequency bandwidth of 3-21 GHz per sideband. Measurements indicate a single sideband receiver noise temperature of approximately 100 K across most of the radio-frequency band. Digital sideband separation was demonstrated using a wideband spectrometer array, yielding an image rejection ratio of around 20 dB. These performance metrics represent progress toward efficient wideband spectral scanning for high-redshift galaxy studies.

Core claim

The 210-350 GHz receiver achieves a single sideband noise temperature of approximately 100 K over most of the radio-frequency band, and digital sideband separation with an image rejection ratio of around 20 dB has been demonstrated using a wideband spectrometer array.

What carries the argument

High-critical-current-density superconductor-insulator-superconductor mixer technology that enables the wide 3-21 GHz intermediate-frequency bandwidth per sideband and per polarization.

If this is right

  • Provides approximately five times wider intermediate-frequency bandwidth than current ALMA specifications.
  • Supports highly efficient spectral-scanning capability on the Large Millimeter Telescope among northern-hemisphere facilities.
  • Facilitates identification of high-redshift galaxy candidates in the early universe.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Successful lab performance suggests the receiver could be scaled for dual-polarization operation across both 120-210 GHz and 210-350 GHz bands.
  • The digital sideband separation method may reduce hardware complexity compared to analog approaches in future wideband systems.
  • Installation on the telescope could enable new surveys that were previously limited by narrower bandwidths.

Load-bearing premise

The laboratory test conditions and calibration accurately represent the noise and sideband performance that will be obtained once the receiver is installed and operated on the Large Millimeter Telescope under actual observing conditions.

What would settle it

Direct measurements of the receiver noise temperature and image rejection ratio after installation on the Large Millimeter Telescope that deviate substantially from the laboratory values of 100 K and 20 dB would falsify the extrapolation to on-sky performance.

Figures

Figures reproduced from arXiv: 2606.25637 by Akio Taniguchi, Haoran Kang, Issei Watanabe, Masato Hagimoto, Masato Kato, Sho Masui, Shun Ishii, Tai Oshima, Takafumi Kojima, Takeshi Sakai, Taku Nakajima, Yoichi Tamura.

Figure 1
Figure 1. Figure 1: Measured double-sideband (DSB) receiver noise temperature of the 210–350 GHz mixer for Far-Infrared Nebular [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Representative single-sideband (SSB) receiver noise temperature of the FINER 210–350 GHz receiver system [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Image rejection ratio (IRR) of the FINER 210–350 GHz receiver system measured at an LO frequency of 246 [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
read the original abstract

The Far-Infrared Nebular Emission Receiver (FINER) project is developing two wideband dual-polarization sideband-separating receivers covering 120-210 GHz and 210-350 GHz to efficiently identify high-redshift galaxy candidates in the early universe. Based on high-critical-current-density superconductor-insulator-superconductor mixer technology originally developed for the ALMA wideband sensitivity upgrade, the FINER receivers are designed to provide an intermediate-frequency bandwidth of 3-21 GHz per sideband and per polarization, approximately five times wider than the current ALMA specifications. After installation on the Large Millimeter Telescope, these receivers are expected to offer highly efficient spectral-scanning capability among (sub)millimeterwave facilities in the northern-hemisphere. This paper reports the initial laboratory characterization of the 210-350 GHz receiver. The measured single sideband receiver noise temperature is approximately 100 K over most of the radio-frequency band. Digital sideband separation was also demonstrated using a wideband spectrometer array (DRS4), achieving an image rejection ratio of around 20 dB in the initial tests. These results represent an important step toward the realization of a wideband spectral-scanning receiver system for FINER.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript reports the initial laboratory characterization of a 210-350 GHz wideband dual-polarization sideband-separating receiver developed for the FINER project on the Large Millimeter Telescope. Key results include a measured single-sideband receiver noise temperature of approximately 100 K over most of the RF band and demonstration of digital sideband separation using the DRS4 spectrometer array, achieving an image rejection ratio of around 20 dB. The design uses high-critical-current-density SIS mixers to achieve a 3-21 GHz IF bandwidth per sideband and polarization.

Significance. If the laboratory results are substantiated, the work represents a meaningful step toward wideband spectral-scanning receivers in the northern hemisphere, with an IF bandwidth approximately five times wider than current ALMA specifications. This could improve efficiency for identifying high-redshift galaxy candidates. The paper provides no machine-checked proofs or parameter-free derivations, but the direct laboratory measurements constitute a concrete, falsifiable data point for the community.

major comments (1)
  1. [Abstract and results section] Abstract and results section: The stated SSB noise temperature of ~100 K and IRR of ~20 dB are presented without accompanying details on the laboratory setup, Y-factor calibration procedure, hot/cold load temperatures, error analysis, or supporting raw data. This omission prevents verification that the measurements support the central performance claims.
minor comments (2)
  1. The manuscript would benefit from a brief comparison table of the achieved IF bandwidth and noise temperature against existing ALMA Band 6/7 receivers to quantify the claimed improvement.
  2. Clarify whether the digital sideband separation tests used the full 3-21 GHz IF bandwidth or a subset, and specify the spectrometer channelization.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their review and for identifying the need for greater transparency in the measurement details. We address the single major comment below and will revise the manuscript accordingly.

read point-by-point responses

  1. Referee: [Abstract and results section] Abstract and results section: The stated SSB noise temperature of ~100 K and IRR of ~20 dB are presented without accompanying details on the laboratory setup, Y-factor calibration procedure, hot/cold load temperatures, error analysis, or supporting raw data. This omission prevents verification that the measurements support the central performance claims.

    Authors: We agree that the current manuscript lacks sufficient detail on the laboratory procedures to allow independent verification of the reported ~100 K SSB noise temperature and ~20 dB image rejection. In the revised version we will expand the results section (and, if space permits, the abstract) to describe the cryogenic test setup, the Y-factor calibration method including the physical temperatures of the hot and cold loads, the error budget and uncertainty analysis, and references to the raw spectra or additional figures that support the quoted performance figures. revision: yes

Circularity Check

0 steps flagged

No significant circularity; claims are direct lab measurements

full rationale

The paper reports empirical laboratory measurements of SSB noise temperature (~100 K) and digital sideband separation performance (~20 dB IRR) using the DRS4 spectrometer. These are presented as initial characterization results with no derivations, parameter fits, self-citation chains, or reductions of predictions to inputs. The abstract and results sections frame the outcomes explicitly as measured data, with no load-bearing theoretical steps or ansatzes that could introduce circularity. This is a standard instrumentation report whose central claims stand on direct observation.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

This is an experimental instrumentation paper reporting laboratory measurements of receiver performance; there are no free parameters, mathematical axioms, or invented entities in the central claims.

pith-pipeline@v0.9.1-grok · 5793 in / 1147 out tokens · 22521 ms · 2026-06-25T20:13:49.473424+00:00 · methodology

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Reference graph

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