THE SUBMILLIMETER RANGE FOR PLANETARY SCIENCE

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The Submillimeter Range for Planetary Science

The submillimeter-wavelength range is the so-called Terahertz (THz) frequency range and it is usually associated with the electromagnetic spectrum of radiations from 1 mm of wavelength (300 GHz of frequency) to 0.03 mm of wavelength (10 THz of frequency). This frequency range has given rise to an intense scientific interest since at least the 1920s [Nich25], but the historical study of the millimeter and the submillimeter range starts in 1890s [Wilt84]. The research on THz science is far from being completed but a detailed summary of the development of this science can be found in [Sieg02]. The THz range remains an important technological challenge today. It has two important facets since the THz frequency range is difficult to reach by both electronic-based sources, when moving up from lower frequencies, and optics based sources, when moving down from upper frequencies. The present work is focused on the electronic-based devices for submillimeter applications. Very important advancements have been carried out in electronic-based devices and the THz range has spread out through diverse technological applications in which the absence of a compact high-efficiency and high-power THz sources is the common ground. The THz range is currently applied in the medical field [Tada04], [Pick06], in spectroscopy [Gopa98], [Encr04], [Shi04], [Hans07], [Luci10] and in THz imaging for multiple applications [Chan07], [Coop08], [Bryl09], [Coop14]. However, it is in atmospheric, planetary and astrophysics sciences as well where the development of THz technologies has been especially enhanced. The interest comes from the large amount of electromagnetic radiation in the THz and far Infra-Red (IR) ranges associated with observable universe that has attracted the attention of astronomers since the early stages of this science [Sieg02]. For example, the kinetic analysis of galaxy dust using the detection of high rotational transitions of the CO molecule lines which are redshifted to millimeter wavelengths [Cox02].
The spectroscopy has been especially important in the development of THz science which has also required the development of THz receivers. The detection of a frequency signal in electronic-based circuits usually consists of a preliminary stage conformed by a Radio Frequency (RF) antenna, which is able to capture a certain frequency range, an electronic device sensitive to those frequency signals and a Low Noise Amplifier (LNA). The first challenge found in THz science to develop THz receivers is the LNA since all solid-state transistors have a cutoff frequency from which the amplification capabilities of the device are dramatically degraded. The commercial THz amplification solid-state technology that has spread out during the last decades is able to rise to W-band (75 – 110 GHz) [IEEE std. 521-2002] using High Electron Mobility Transistors (HEMTS), metamorphic HEMTs (mHEMTs) and Heterojunction Bipolar Transistors (HBTs) mostly based on InP and GaAs semiconductor (SC) structures [Samo11]. Additionally, these devices allow THz amplifiers for broadband applications (bandwidth ~20 % of the center frequency) that can operate at room temperature. Commercial Monolithic Microwave Integrated Circuits (MMIC) amplifiers up to 100 GHz are commonly found up to W-band [Wang01], but higher frequency broadband amplifiers around 200 GHz [Wein99], [Deal07a], [Chio16], around 300 GHz [Deal07b], [Tess08] and even up to 600 GHz [Seo13], [Tess14], [Deal16] have already been demonstrated. A lot of narrowband amplifiers can be found even at higher frequencies using diverse technologies [Truce14]. However, most of these amplifiers are not commercialized and the technology is carefully controlled by the manufacturers or even restricted for military applications. This leads to lower frequency amplifiers up to W-band (75 – 100 GHz) that have been commonly commercialized. The application of this technique based on GaN amplifiers is providing higher output power at W-band during the last years [Mish08], [Sile08b], [Sche16], [Marti16] and it could eventually replace the actual GaAs and InP-based W-band amplifiers in a near future. The availability of a commercial W-band LNA has also been a prior objective that has encouraged significant research [Mei08], [Brye09], [Yang13], [Pepe15], [Zhan16]. This absence of commercial availability of higher frequency amplifiers has hampered THz detection, especially in room temperature direct detection applications at THz frequencies which is nowadays limited up to W-band [Hoef14], [Deco16].
The alternative technology that has placed itself in the THz detection field due to its sensitivity and high spectral resolution (1-100 MHz) at THz frequencies is the heterodyne detection technique. The development of a 1.2 THz heterodyne receiver is the subject of this work and the different motivations that have enhanced the accomplishment of this work are pointed out in this section.

The Heterodyne Detection

The heterodyne reception is a widespread technique in most of the THz applications developed for THz science since these kinds of receivers allow moving up on frequency beyond the 1 THz RF detection [Sieg02]. A general scheme of a heterodyne receiver for THz applications is shown in Fig. 1.1. A THz heterodyne electronic-based receiver requires a Radio Frequency (RF) mixer module sensitive to certain THz frequency ranges coming from a RF source. This mixer module needs to be pumped by a THz power source, so-called Local Oscillator (LO), able to yield a very precise frequency signal under W-band (with only some few tens of MHz wideband) that is then multiplied N times to increase the frequency up to the mixer requirement. A telescope and optical bench are usually used to increase the effective detection surface and focus the signal into the RF horn of the mixer. The RF signal at frequency fRF is mixed with the LO signal at frequency fLO by the mixing stage resulting in an Intermediate Frequency (IF) signal at frequency fIF= fRF – n•fLO, where n refers to the n-th harmonic of the LO frequency signal [Hayk08]. It is possible to differentiate between fundamental heterodyne receivers if n = 1 and sub-harmonic receivers if n ≥ 2. The heterodyne receiver developed in this work corresponds with the second kind with n = 2. These receivers are usually designed to generate an IF signal low enough to be amplified by commercial LNAs, i.e., the considered frequency of the LO signal (or its n-th harmonic) is similar to the detected RF frequency signal. Usually, no LNA is used in THz heterodyne receivers to amplify the captured RF signal by the RF antenna since there isn’t frequency LNAs able to efficiently work beyond W-band. This result in a LO input power which is usually much higher than the RF input power in these receivers. The principles of frequency mixing using non-linear devices can be found in [Man56], [Pant58], [Ebst67], [Sea69].

THz Frequency Mixers

The most critical element of the heterodyne reception is the frequency mixer and especially the non-linear devise used to efficiently mix the LO and the RF signal. Several technologies have been  studied in THz science for mixing applications but the most widespread devices are the Superconductor-Isolator-Superconductor (SIS), the Hot-Electron Bolometers (HEB) and the Planar Schottky Diodes (PSBDs). The SIS technology has proven to be the best device for mixing applications since frequency heterodyne receivers, with Single Side Band (SSB) noise temperature as low as 2 times the quantum noise limit (hf/k), have been demonstrated [Kerr99], [Koll02], [Chat08], [Maes10b], [Bill13]. Additionally, these mixers can perform a broadband IF band [Laur01], [Pan04] with low LO power requirements. However, the SIS mixers require cryogenic temperatures to work and they are limited up to 1.5 THz, mainly due to the disappearance of the superconductor properties [Karp07], [West13], [Zmui15]. The HEB has been placed itself as the alternative device that is able to replace the SIS beyond its frequency limit. The HEB are also required to be cooled down to 2 – 4 K but frequency receivers up to 4.7 THz have been demonstrated with DSB noise temperatures 10-20 times the quantum noise limit [Haje04], [Chat07], [Cher08], [Tret11], [Buch15]. HEB are able to provide the best performances using very low LO input power, hundreds of nW, which is possible to obtain with both electronic and optical based THz sources. The challenge of HEBs is the short IF bandwidth that it is possible to provide and the cooling system requirement. Regarding the PSBDs technology, it can provide frequency receivers with DSB noise temperature much higher than SIS and HEB, above 50 times the quantum noise limit, but it is able to work at room temperature. This results in extremely compact frequency mixers that do not require any cryogenic system [Chat07], [Maes10b]. Additionally, the performance of PSBD mixers is always improved down to 30-40 times the quantum noise limit when cooling down below 150 K [Pred84], [Schl14], [Treu16]. Very important efforts are focused now to develop frequency mixers based on Schottky technology that will overcome the SIS frequency limit in a near future [Treu16b]. The challenge of PSBD mixers is the high LO power requirements compared with HEBs and the higher noise provided as the frequency increases. This work is focused on the development of a 1.2 THz mixer based on PSBD technology. The PSBD technology has positioned itself as the most suitable option for space-borne applications that do not require the most sensitive receivers, like planetology or remote sensing of the Earth’s atmosphere, due to the compact low-weight receivers that can be achieved.

THz Local Oscillator

One of the most difficult challenges faced by the THz science community, which has not been addressed yet, is obtaining a powerful, efficient and compact THz source. The main challenge when reaching the THz range in electronic-based applications is associated to an electron transit time in the same order of the THz frequencies, hampering the proper functioning of electronic-based devices when moving up in frequency. Similarly, a THz laser based on an energy transition requires transition energy of the same order as the room temperature lattice vibrations in the material, hampering the proper functioning of optic-based devices when moving down in frequency. The development of electronic-based THz sources using solid-state oscillators has been pursued for several decades. One of the most promising THz oscillators above 100 GHz is based on InP Gunn devices, thoroughly studied by Dr. Carlstrom [Carl85] and Dr. Eisele in [Eise95], [Eise97], [Eise00], [Eise04], [Eise06], [Eise10] and by Dr. Khalid in [Khal07], [Khal13]. The Gunn diodes were widely used in the (sub)-millimeter heterodyne receivers in the past. However, Gunn diodes require phase locking, are difficult to tune and to use in broadband frequency applications. Gunn oscillators have been currently replaced by amplify-multiply chains. Interesting advancements have been carried out during the last years by Tokyo Institute of Technology in fundamental THz source based on Resonant Tunneling Diodes (RTDs) up to 1.46 THz [Feig14] and 1.92 THz [Maek16]. Regarding the optical based THz source, the Quantum Cascade Laser (QCL) technology has placed itself as the leading mid-infrared (mid-IR) source since it was proposed twenty years ago and it has shown itself to be the most suitable way to substantially reduce the frequencies even down to 1 THz [Will07]. However, the challenge faced by QCL sources is avoiding the cryogenic temperatures requirement that notably hampers this technology to spread out in the THz applications [Belk15]. Other techniques use crystals as coherent THz source [Shi02]. An intermediate technique that combines optical and electronic base devices is based on photo-mixers and it allows obtaining LO power sources suitable to pump SISs or HEBs based mixers. The photo-mixers can mix two laser beams at IR range to generate an electrical signal at required LO frequencies [Font07], but this technique usually requires cooling systems due to the low conversion efficiency of the photomixers and the high amount of power dissipated in the device. Low LO power sources can be provided by this technique.
The alternative electronic-based technology that has been able to place itself in the commercial applications at THz frequencies is based on frequency multiplication. The technique used in this work, which is able to provide the highest LO power electronic-based sources know nowadays, consists of a preliminary commercial Ultra Stable Oscillator (USO), at a single frequency of few tens or hundreds of MHz [Cand03], followed by a commercial Frequency Synthesizer [Tobi01] that is able to generate a broadband frequency window up to some tens of GHz [Jain09] using the reference given by the USO. The generated millimeter wavelength source can be amplified using available commercial amplifiers obtaining some hundreds of mW at E-band (60-90 GHz) and multiplied to move beyond 100 GHz. The multiplication chains usually consist of an assembly of frequency doublers and triplers in accordance with the desired output frequency signal and the available amplifier source [Sieg02]. It is based on the excitation, at a specific frequency f1, of a passive non-linear solid-state device whose response will contain the fundamental frequency f1 and its harmonics n f1 with n= 2, 3,…, ∞. Electronic-based frequency doublers and triplers usually consist of a waveguide system to lead the input and output frequency signals and a passive non-linear solid-state device mounted in a microelectronic chip. The microelectronic chip is designed to couple the input signal in a certain frequency and power range and it also couples the desired frequency harmonic generated by the non-linear device with the output waveguide system. The most important electronics-based device technologies used currently in the THz multiplication field are the Heterostructure Barrier Varactors (HBVs) and the PSBDs previously mentioned.
The LO source used in this work is also based on the second type of devices, i.e., the 1.2 THz receiver developed in this work is an all-solid state PSBD heterodyne receiver. The theoretical foundation of the so-called metal-semiconductor rectifiers started in 1931 when the band model of SCs was formulated [Wils31]. The fundaments of Schottky barrier diodes were proposed by W. Schottky in 1938 [Scho38] and H. A. Bethe formulated in 1942 [Beth42] the well-known thermionic emission theory that describes the electrons transport through the Schottky barriers. The HBVs were first introduced by Kollberg and Rydberg in [Koll89], [Rybd90] and they can only be used in odd harmonic multiplication due to the internal symmetry of the device. HBVs are suitable for frequency triplers [Salg03], [Vuku12] and especially useful in quintupler applications providing efficiencies higher than PSBDs [Bryl12], [Malk15]. Nevertheless, it is the Schottky technology which is widespread in millimeter and submillimeter applications, especially for ground-base and space-borne heterodyne applications since it is able to provide the highest efficiencies, output power and instantaneous bandwidth [Maes05a]. It is mainly because PSBDs can be used in different configurations to design both doublers and triplers as varactor mode, and it can also be used for mixing applications in varistor mode. It can work at room temperature, allowing PSBD based modules to be very compact and robust. They can easily pump frequency mixers based on HEB or SIS technologies. It has motivated the development of a wide range of PSBDs frequency broadband multipliers since the 1990s from 100 GHz to up to 2.7 THz [Eric93], [Schl01a], [Maes05a], [Maes06], [Maes08], [Maes10a], [Sile11a], [Maes12], [Treu14], [Sile15]. Different combinations of doublers and triplers in a multiplication chain based on PSBDs also allow the development of THz sources at different frequency ranges using the same millimeter source. A summary of the actual THz electronic and optic-based sources availability can be found in [Maes10b (Fig.1)] and [Will07], respectively.

Space missions and THz science

Some of the most important space missions where a millimeter or submillimeter instrument was proposed are summarized in this section. The common ground between these mission is the implementation of some of the different technological approaches used to define the technical specification of the SWI instrument. The development and implementation of these space missions summarized the background that has motivated the basis of JUICE-SWI project and this work

Ground-based millimeter and Sub-Millimeter Telescopes

The ALMA project [ALMA 2016] is the largest ground-based radio-telescope currently existing for millimeter and submillimeter astronomy interferometry and it is placed in the Atacama Desert, Chile. It consists of 54 antennas of 12 m diameter equipped with frequency receivers based on SIS mixers covering the 30-950 GHz [Brow04]. ALMA has operated since 2009 but it was inaugurated in 2013. ALMAs receivers are based on SIS mixers and the LO chain is mainly based on MMIC Schottky diodes multipliers [Brye05], [Morg05] that were developed by VDI. The W-band power amplifiers drivers are based on MMIC InP HEMTs technology [Samo05]. ALMA was develop to improve the performances and complement the already existing submillimeter telescopes such as the James Clerk Maxwell Telescope (JCMT) in Hawaii and interferometers as the Institut de Radio Astronomie Millimétrique (IRAM) in France. The JCMT [Murd00] is placed in Hawaii island and it is a single 15 m diameter dish dedicated to the detection of submillimeter radiation between 1.4 to 0.4 mm wavelengths. The IRAM [Maar87] was established in 1984 in Pico Veleta, Spain, and it is a 30-m millimeter radiotelescope. It had a complementary array of three 15-m antennas placed on Plateau de Bure Observatory, France, which has eventually been extended to six antennas and finally replaced by the current NOEMA project since 2014 with six additional 15-m antennas. The six array NOEMA project is expected to be completed in 2019, becoming the most powerful millimiter radiotelescope in the North Hemisphere [IRAM-2016].

Earth Observing System: AURA Satellite

The AURA satellite was launched on July 2004 as part of the NASA’s Earth Observing System (EOS) program. This science program is dedicated to monitoring the complex interactions that affect the globe. The AURA satellite is in a sun-synchronous orbit specifically dedicated to analyzing climate change by monitoring the interactions of the ozone and other chemical compounds with the radiation. AURA consists of four instruments dedicated to the analysis of the ozone and other greenhouse compounds from different aspects. The High Resolution Dynamics Limb Sounder (HRDLS) is dedicated to analyzing infrared emission, the Microwave Limb Sounder (MLS) to analyzing microwave emission, the Tropospheric Emission Spectrometer (TES) and the Ozone Monitoring Instrument (OMI).
The MLS instrument [Wate06] was one of the first important microwave space-borne instruments that enhanced the development of this technic. It is an on-board submillimeter instrument based in heterodyne reception in broad spectral regions centered at 118, 190, 240 and 640 GHz and 2.5 THz. All solid state technology was used for the local oscillators, excepting in the 2.5 THz, and MMIC amplifiers for the 118 GHz channel. All the frequency mixers were based in planar technology [Sieg93].

Microwave Instrument for Rosetta Orbiter (MIRO)

The Rosetta mission is a comet mission accepted by the ESA in November 1993 in the framework of the long-term program “Horizon 2000” [Glas07]. It consists of two mission elements, the ROSETTA orbiter and the PHILAE lander. ROSETTA was launched in March 2004 featuring the unprecedented assembly of 25 payload-experiments. The main scientific objectives of ROSETTA were the study of the origin of the solar system by studying comets. ROSETTA took contact with the comet 67P/Churyumov-Gerasimenko in summer 2014 and PHILAE lander was successfully deployed at the end of 2014. The mission was a complete success and it finished in September 2016 [ROSETTA-Mission-2016]. One of the ROSETTA instruments is the so-called Microwave Instrument for Rosetta Orbiter (MIRO). A precise description of MIRO and the molecules studied by it can be found in [Gulk07]. This is a heterodyne spectrometer working at two frequency ranges around 190 GHz and 562 GHz. The frequency mixer modules of MIRO are based on PSBD technology while the LO multiplication chain is a combination of different technologies. The LO source is based on InP Gunn devices to generate a LO signal around 95 GHz. This Gunn source is enough to directly pump the PSBD-based sub-harmonic mixer for the 190 GHz channel of MIRO, while a HBV-based frequency tripler is used to increase the frequency of the signal to pump the PSBD-based sub-harmonic mixer of the 562 GHz channel. This heterodyne receiver didn’t require any cooling system and it has successfully demonstrated the PSBD technology capabilities as mixer stage for space-borne front-end heterodyne detection.

HESHEL Space Observatory

The development of THz science has been especially encouraged by the atmospheric, planetary and astrophysics sciences which have enhanced and positioned the different available THz technologies as actual state-of-the-art. One of the first space missions that has enhanced the development of the heterodyne reception is the Far Infra-Red and Submillimeter Telescope (FIRST) mission led by the European Space Agency (ESA) in the “Horizon 2000” science plan. This telescope was expected to be put in a geostationary Earth orbit in late 2005 and featuring a payload of two instruments and at least 3 m telescope mirror [Pilb97]. The launch was delayed and the project was renamed as “HERSHEL”, in honor of Sir William Hershel who discovered the Infra-Red spectrum. The HERSHEL space observatory was finally launch in 2009 and it was the largest infra-red telescope launched until the mission ended in 2013. HERSHEL finally featured a 3.5 m telescope mirror and three instruments, the Photodectective Array Camera and Spectrometer (PACS), the Spectral and Photometric Imaging REceiver (SPIRE) and the Heterodyne Instrument of Far Infra-red (HIFI) [Pilb10]. It was the HIFI instrument which motivated an intense activity in THz heterodyne technology based on multiplication and mixing stages up to the desired frequency channels. HIFI is a set of 7 heterodyne receivers that are electronically tunable, covering a 0.48-1.25 THz range in five bands using SIS mixers and a 1.41-1.91 THz range in two bands using HEB mixers. A cryostat was included in the payload module of HERSHEL due to the cryogenic requirements of these technologies. Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères (LERMA) was involved in the development of the SIS mixer used in the first band between 480-640 GHz. The main interest of these frequency ranges was focused on water lines analysis, surveying the molecular complexity of the universe and observations of ionized carbon for redshift analysis. Each receiver had two LO multiplier chains completely based on planar Schottky diodes technology with their corresponding W-band amplifiers [Samo00]. The LO chain for each receiver development was strongly enhanced by JPL and some details can be found in [Pear00], [Pear03], [Maes06a]. The complete development of the LO chain based on Schottky diodes technology not only allowed high-power handling capability and an improved reliability and stability of the receivers, but it dramatically reduced the cryogenic system requirements of HIFI. Nevertheless, HERSHEL was operational during 3.5 years due to the limited cryogenic gas stock.
The success of HERSHEL-HIFI, together with ROSETTA-MIRO, has laid the basis of the space-borne THz science, where Schottky technology has demonstrated an important role. The progress made during the last two decades in the completion of such important scientific goals and the developed techniques have motivated a wide range of future space mission proposals. JUICE mission was elected in the framework of the ESAs “Cosmic Vision 2015-2025” program [ESA-Cosmic-Vision (2016)]. This work is focused on the development of a part of the sub-millimeter instrument of JUICE as described below.

Table of contents :

INTRODUCTION 
1 THE SUBMILLIMETER RANGE FOR PLANETARY SCIENCE 
1.1 THE HETERODYNE DETECTION
1.1.1 THZ FREQUENCY MIXERS
1.1.2 THZ LOCAL OSCILLATOR
1.1.3 SPACE MISSIONS AND THZ SCIENCE
1.2 THE JUICE PROJECT BASELINE
1.2.1 THE SUBMILLIMETER WAVE INSTRUMENT (SWI)
1.3 DESIGN AND OPTIMIZATION OF PSBD-BASED MMIC MODULES
1.4 STRUCTURE AND OBJECTIVES OF THIS PHD WORK
PART 1: PLANAR SHOTTKY BARRIER DIODES MODELING
2 ANALYTICAL MODEL OF PLANAR SCHOTTKY BARRIER DIODES 
2.1 THE TWO-DIMENSIONAL MONTE CARLO SIMULATOR
2.1.1 PSBD STRUCTURE IN MONTE CARLO SIMULATIONS
2.2 THE CURRENT TRANSPORT AND CAPACITANCE MODEL IN PSBDS
2.2.1 BUILT-IN VOLTAGE AND BARRIER HEIGHT RELATIONSHIP
2.2.2 ANALYTICAL MODEL OF CURRENT TRANSPORT IN PSBDS
2.2.3 RESISTANCE MODEL OF PSBDS
2.2.4 CAPACITANCE ANALYTICAL MODEL IN PSBDS
2.3 THE ANALYTICAL MODEL IN HARMONIC BALANCE SIMULATIONS
2.3.1 SINGLE VARACTOR PSBD SIMULATIONS FOR DOUBLERS
2.3.2 ANTIPARALLEL VARISTOR PSBDS SIMULATIONS FOR MIXERS
2.4 CONCLUSIONS
PART 2: THE JUICE-SWI PROJECT
3 A POWER-COMBINED 300 GHZ FREQUENCY DOUBLER
3.1 THE 300 GHZ FREQUENCY DOUBLER CHIP
3.1.1 DESCRIPTION OF THE VIRTUAL DEVICE
3.1.2 DESCRIPTION OF THE MECHANICAL BLOCK
3.1.3 EXPERIMENTAL RESULTS
3.1.4 EXPERIMENTAL COMPARISON BETWEEN PSBD PHYSICAL MODELS
3.2 A POWER-COMBINED 300 GHZ FREQUENCY DOUBLER
3.2.1 QUADRATURE HYBRID COUPLER
3.2.2 DESCRIPTION OF THE MATCHING NETWORK DESIGN
3.2.3 MECHANICAL BLOCK DESIGN: DC CIRCUIT
3.2.4 EXPERIMENTAL RF PERFORMANCE
3.2.5 COMPARISON WITH ADS-HFSS INDIVIDUAL SIMULATIONS
3.3 CONCLUSIONS
4 A 600 GHZ FREQUENCY DOUBLER 
4.1 TWO-ANODES 600 GHZ TWO ANODES FREQUENCY DOUBLER
4.1.1 VIRTUAL DEVICE
4.1.2 MECHANICAL BLOCK
4.1.3 EXPERIMENTAL DEVICE
4.1.4 SIMULATIONS OF THE TWO-ANODES 600 GHZ FREQUENCY DOUBLER
4.1.5 EXPERIMENTAL COMPARISON WITH COMBINED SIMULATIONS OF THE 300 GHZ POWER-COMBINED AND 600 GHZ DOUBLERS
4.2 A 600 GHZ FOUR ANODES FREQUENCY DOUBLER
4.2.1 OPTIMIZATION OF THE PSBDS PROPERTIES
4.2.2 VIRTUAL DESIGN IN ADS-HFSS
4.2.3 VIRTUAL ADS-HFSS COMPARISON BETWEEN THE 600 GHZ TWO AND FOUR ANODES DOUBLERS
4.2.4 COMPARISON WITH ADS-HFSS INDIVIDUAL SIMULATIONS
4.2.5 EXPERIMENTAL COMPARISON WITH COMBINED SIMULATIONS OF THE 300 GHZ AND
THE 600 GHZ FOUR ANODES DOUBLER
4.3 CONCLUSIONS
5 A 600 GHZ FREQUENCY RECEIVER 
5.1 QUALITATIVE DESCRIPTION OF THE DEVICE
5.1.1 IF ADAPTER CIRCUIT
5.2 ANALYSIS OF THE PSBDS IMPEDANCE MATCHING IN THE 600 GHZ MIXER
5.3 ANALYSIS OF THE PSBDS PERFORMANCES
5.3.1 ANALYSIS OF THE CM
5.3.2 ANALYSIS OF THE
5.3.3 IMPROVEMENT OF THE 600 GHZ SUBHARMONIC MIXER PERFORMANCE
5.4 CONCLUSIONS
6 A 1.2 THZ SUB-HARMONIC BIASABLE FREQUENCY MIXER 
6.1 OPTIMIZATION OF THE PSBDS PROPERTIES
6.1.1 ANALYSIS OF THE
6.1.2 ANALYSIS OF THE
6.2 DESCRIPTION OF TWO DIFFERENT 1.2 THZ MIXER CHIP DESIGNS
6.2.1 IN-CHANNEL AND OUT-CHANNEL DESIGNS OF THE CHIP
6.2.2 LO ANTENNA AND HAMMER FILTER
6.2.3 DC GROUND STRUCTURE
6.2.4 RF FILTER AND ANTENNA
6.3 MECHANICAL BLOCK: IF AND DC CIRCUITS
6.3.1 IF CIRCUIT
6.3.2 DC CIRCUIT
6.4 THEORETICAL COMPARISON IN ADS-HFSS SIMULATIONS
6.4.1 CONVERSION LOSS AND NOISE TEMPERATURE OF THE RECEIVER
6.4.2 NOISE IN SCHOTTKY MIXERS
6.4.3 NOISE TEMPERATURE IN ADS SIMULATIONS
6.4.4 SIMULATED CONVERSION LOSS IN THE 1.2 THZ MIXER CHIPS
6.4.5 SIMULATED NOISE TEMPERATURE IN THE 1.2 THZ MIXER CHIPS
6.4.6 ANALYSIS OF THE BIAS PERFORMANCES AND THE RLC EQUIVALENT CIRCUIT
6.4.7 CONCLUSIONS
6.5 EXPERIMENTAL DEVICE
6.5.1 I-V CHARACTERISTICS OF THE DIODES
6.5.2 THE Y-FACTOR FOR EXPERIMENTAL MEASUREMENT
6.5.3 RF RESULTS OF THE 1.2 THZ RECEIVER AT 300 K
6.5.4 RF RESULTS OF THE 1.2 THZ RECEIVER AT 160 K
6.6 COMPARISON WITH ADS-HFSS INDIVIDUAL SIMULATIONS
6.7 SIMULTANEOUS SIMULATION OF THE 600 GHZ DOUBLER AND THE 1.2 THZ MIXER
6.7.1 SIMULTANEOUS SIMULATIONS WITH THE 600 GHZ TWO ANODES DOUBLER
6.7.2 SIMULTANEOUS SIMULATIONS WITH THE 600 GHZ FOUR ANODES DOUBLER
6.7.3 SIMULTANEOUS SIMULATIONS OF THE 1.2 THZ MIXER WITH HIGHLY DOPED PSBDS
6.8 UPDATED EXPERIMENTAL STATUS OF THE 1.2 THZ RECEIVER
6.8.1 LOCAL OSCILLATOR CHAIN
6.8.2 I-V CHARACTERISTICS OF THE NEW SET OF PSBDS 1.2 THZ CHIPS
6.8.3 UPDATED RESULTS OF THE 1.2 THZ RECEIVER AT 150 K
6.9 CONCLUSIONS
7 CONCLUSIONS AND PERSPECTIVES 

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