High/low-impedance transmission-line and coupled-line filter networks for differential phase shifters

Two compact and simple to design differential phase shifter topologies, based on high/low-impedance transmission-line sections and open-ended coupled-line sections, are presented for the first time. The basic circuit theory for single section topologies is reviewed, leading to design equations and graphs for direct circuit synthesis. Balanced topologies and multiple section designs are also proposed improving the performance and feasibility of the phase shifters. Two planar microstrip single section differential phase shifter hybrids, at a centre frequency of 12 GHz and a 45 and 135° phase difference have been designed and manufactured. The designs have a simulated 0.5 dB amplitude and 1° phase imbalance over more than 25 and 40% bandwidth, respectively. Experimental results verify the circuit performance and feasibility of the proposed differential phase shifters

Effect of idler terminations on the conversion loss for THz Schottky diode harmonic mixers

Efficient and reliable frequency converters, preferably operating at room temperature, are critical components for frequency-stabilizing terahertz sources. In this work, we present the analysis of optimum configurations for Schottky diode-based x4, x6, and x8 harmonic mixers operating at 2.3 THz, 3.5 THz, and 4.7 THz respectively. Detailed large-signal analysis of the two basic single-ended Z- and Y-mixers was carried out using a standard Schottky-diode model. For each case, the conversion loss was minimized by finding optimal embedding impedances at RF, LO, and IF frequencies. The analysis shows that the Y-mixer has less conversion loss at a low LO pump power. However, the Z-mixer provides reduced loss with increasing harmonic index and pump power due to the associated power dissipation in idler circuits. The results provide preliminary design guidelines for room- temperature frequency converters and their use in phase-locked loop applications

A 183-GHz Schottky diode receiver with 4 dB noise figure

Atmospheric science based on space-borne\ua0millimeter wave measurements require reliable and state-of-the art\ua0receivers. In particular, the water vapor line at 183.3 GHz\ua0motivates the development of sensitive mixers at this frequency.\ua0Traditional assembly techniques employed in the production of\ua0Schottky diode receivers involve flip-chip mounting and soldering\ua0of discrete dies, which prohibit the implementation of reliable and\ua0repeatable production processes. In this work, we present a\ua0subharmonic 183 GHz mixer implementing a repeatable assembly\ua0method using beamlead Schottky diodes. The mixer was\ua0integrated with a InP HEMT MMIC low noise intermediate\ua0frequency amplifier resulting in a record-low receiver noise\ua0temperature of 450 K at 1 mW of local oscillator power measured\ua0at room-temperature. The measured Allan time was 10 s and the\ua0third order local oscillator spurious power was less than -60 dBm.\ua0The proposed assembly method is of particular importance for\ua0space-borne missions but also applicable to a wide range of\ua0terahertz applications

A 3.5-THz, x6-Harmonic, Single-Ended Schottky Diode Mixer for Frequency Stabilization of Quantum-Cascade Lasers

Efficient and compact frequency converters are essential for frequency stabilization of terahertz sources. In this paper, we present a 3.5-THz, x6-harmonic, integrated Schottky diode mixer operating at room temperature. The designed frequency converter is based on a single-ended, planar Schottky diode with a sub-micron anode contact area defined on a suspended 2-$\mu$m ultra-thin GaAs substrate. The dc-grounded anode pad was combined with the radio frequency E-plane probe, which resulted in an electrically compact circuit. At 200 MHz intermediate frequency, a mixer conversion loss of about 59 dB is measured and resulting in a 40 dB signal-to-noise ratio for phase locking 3.5-THz quantum-cascade laser. Using a quasi-static diode model combined with electromagnetic simulations, good agreement with the measured results was obtained. Harmonic frequency converters without the need of cryogenic cooling will help in the realization of highly sensitive space and air-borne heterodyne receivers.Comment: Submitted to IEEE-TS

Low noise 874 GHz receivers for the international submillimetre airborne radiometer (ISMAR)

We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the international submillimetre airborne radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials leads to a reduction in a noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%-9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5 and side lobe levels below 20 dB. The return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to be 750-1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below 25 dB and are dominated by the external waveguide interface

Advanced Schottky Diode Receiver Front-Ends for Terahertz Applications

This thesis treats the development of high frequency circuits for increased functionality of terahertz receiver front-ends based on room temperature Schottky diode technology. This includes the study of novel circuit integration schemes, packaging concepts as well as new measurement and characterisation techniques.As the main result, a novel broadband waveguide integrated sideband separating (2SB) receiver topology for future Earth observation submillimetre wave instruments is proposed. The 2SB receiver topology has an inherent low RF and LO port voltage standing wave ratio (VSWR) and high sideband ratio (SBR). It is based on subharmonic (x2) Schottky diode double sideband (DSB) mixers with embedded IF low noise amplifiers (LNA\u27s) and LO and RF 90 degree waveguide hybrids. Access to the IF IQ-paths makes it possible to implement phase and amplitude imbalance compensation schemes. Sideband separation is done in the analog domain by the use of an IF 90 degree hybrid or in the digital domain by using an IQ-correlator spectrometer. The use of embedded LNA\u27s reduces the IF losses and leads to a low ripple and broadband response.Measured results on a prototype 2SB receiver operating in the 320 GHz to 360 GHz frequency range show an untuned SBR of 15 dB over the whole band and mixer noise consistent with the optimal performance of a DSB mixer. The LO return loss is measured to be approximately 15 dB (broadband) and the RF return loss is estimated to have similar performance. A 340 GHz DSB receiver with an embedded custom designed 3-15 GHz LNA has also been developed. By co-simulation of the mixer and LNA using a simple mixer noise model it is shown that accurate prediction of the receiver noise response is possible. The DSB receiver exhibits ultra low noise over the 12 GHz IF bandwidth, with a minimum input receiver noise temperature of 870 K (DSB).Two novel differential line phase shifters based on stepped impedance and coupled-line filter structures are proposed. The filters have a minimum lateral distribution making them well suited for use in submillimetre wave circuits. A method for TRL-calibration of terahertz monolithic integrated circuits (TMIC\u27s) is also proposed and demonstrated. The method allows for embedded S-parameter characterisation of waveguide integrated TMIC devices and circuits

Advanced Schottky Diode Receiver Front-Ends for Terahertz Applications

This thesis treats the development of high frequency circuits for increased functionality of terahertz receiver front-ends based on room temperature Schottky diode technology. This includes the study of novel circuit integration schemes, packaging concepts as well as new measurement and characterisation techniques.As the main result, a novel broadband waveguide integrated sideband separating (2SB) receiver topology for future Earth observation submillimetre wave instruments is proposed. The 2SB receiver topology has an inherent low RF and LO port voltage standing wave ratio (VSWR) and high sideband ratio (SBR). It is based on subharmonic (x2) Schottky diode double sideband (DSB) mixers with embedded IF low noise amplifiers (LNA\u27s) and LO and RF 90 degree waveguide hybrids. Access to the IF IQ-paths makes it possible to implement phase and amplitude imbalance compensation schemes. Sideband separation is done in the analog domain by the use of an IF 90 degree hybrid or in the digital domain by using an IQ-correlator spectrometer. The use of embedded LNA\u27s reduces the IF losses and leads to a low ripple and broadband response.Measured results on a prototype 2SB receiver operating in the 320 GHz to 360 GHz frequency range show an untuned SBR of 15 dB over the whole band and mixer noise consistent with the optimal performance of a DSB mixer. The LO return loss is measured to be approximately 15 dB (broadband) and the RF return loss is estimated to have similar performance. A 340 GHz DSB receiver with an embedded custom designed 3-15 GHz LNA has also been developed. By co-simulation of the mixer and LNA using a simple mixer noise model it is shown that accurate prediction of the receiver noise response is possible. The DSB receiver exhibits ultra low noise over the 12 GHz IF bandwidth, with a minimum input receiver noise temperature of 870 K (DSB).Two novel differential line phase shifters based on stepped impedance and coupled-line filter structures are proposed. The filters have a minimum lateral distribution making them well suited for use in submillimetre wave circuits. A method for TRL-calibration of terahertz monolithic integrated circuits (TMIC\u27s) is also proposed and demonstrated. The method allows for embedded S-parameter characterisation of waveguide integrated TMIC devices and circuits

STEAMR Receiver Chain

We report on the development of the STEAMR radiometer system, including the front-end receivers, LO multipliers and the back-end spectrometer system. STEAMR constitutes the submillimeter wave limbsounder on board PREMIER, one of three ESA Earth Explorer Core missions that have entered a feasibility study phase. The STEAMR instrument is based on a linear array of 14 heterodyne receivers operating in the 320 GHz to 360 GHz band processing over 260 GHz of instantaneous IF bandwidth. Thereto, eight of the fourteen receivers are to be sideband separating (2SB) and a novel waveguide based topology with integrated LNA’s has been developed.An overview of the receiver system is presented together with a conceptual design optimized to meet the scientific goals of the instrument. Preliminary results on critical receiver components such as front-end mixers, LO chains and the back end spectrometer are presented and different alternatives for realization are discussed

Optimisation and Design of a Suspended Subharmonic 340 GHz Schottky Diode Mixer

A fixed tuned subharmonic 340 GHz GaAs Schottky diode mixer design is presented. The mixer consists of a 3 mil quartz substrate that is suspended in a LO and RF reduced height waveguide splitblock, and uses a coaxial connector for the IF interface. It has been designed for the VDI SC1T2-D20 antiparallell diode chip that is flip-chip mounted on the circuit. The performance of three types of RF stop filter topologies have been evaluated and will be presented