Image Sideband Research Articles

10-Gbps real-time wireless link over 1.5 km at 220-GHz band based on Schottky-diode transceiver and 16-QAM modulation

A wireless link working at 220-GHz band is proposed for point-to-point high-speed communication. The system is primarily composed of sub-terahertz transceivers and baseband data processing platforms. Subharmonic mixers based on Schottky diode are developed and measured with a double-sideband (DSB) noise temperature of lower than 1100 K from 205 GHz to 230 GHz. High-selectivity waveguide bandpass filters are designed to reject the image sideband noise from entering the receiver. Two 58-dBi Cassegrain antennas are used to compensate for the large energy losses contributed by free space path and atmospheric absorption. Besides, sub-THz amplifiers based on InP HEMT technology are developed to further increase the transmitting power. To improve spectrum efficiency, 16 quadrature amplitude modulation is adopted. Forward error correction is implemented by using Reed-Solomon codes to reinforce the reliability of signal transmission. An outdoor wireless link is finally established within 1.5 km, and a data rate of 10 Gbps is achieved in real-time mode with an EVM of 9.53% (BER 1.4×10-9). For demonstration, uncompressed ultra-HD videos are successfully transmitted. Note that any auxiliary electronic testing and measurement equipment is not required while communicating. It is believed that this article provides an effective and practical solution for future long-distance high-speed communication.

Experimental study of a phase-sensitive heterodyne detector

It is believed that the quantum behaviors of homodyne detectors and traditional heterodyne detectors can be fully understood in the context of the quantum theory of optical detection. According to the theory, a 3 dB extra quantum noise has been predicted in a traditional heterodyne detector, as a phase-insensitive device, due to the existence of the image sideband vacuum. However, regarding the noise performance of a phase-sensitive heterodyne detector, a fundamental dilemma inevitably arises: On one hand, the detector should suffer the 3 dB noise penalty caused by the image sideband vacuum, on the other hand, it, as a phase-sensitive device, should be noise free at the quantum level. We report on an experiment on the quantum noise performance of a phase-sensitive heterodyne detector with a bichromatic local oscillator. The results show that the studied detector is noise free, i.e., the quantum noise of the image sideband vacuum is absent in the observation. Revealing the mechanism for the absence of the image vacuum noise will be important for a full understanding of the origin of the quantum noise in optical detection.

Superconductor-Insulator-Superconductor Mixers for the 2 mm Band (129-174 GHz)

We present the design, construction and performance of backshort-tuned Single Side Band (SSB) and of fixed-tuned Double Side Band (DSB) Superconductor-Insulator-Superconductor (SIS) mixers covering the frequency range of 129-174 GHz (2 mm band). Receivers employing these SSB mixers have been continuously operated for astronomical observations on the six antennas of the IRAM Plateau de Bure Intereferometer (PdBI) since 2007 and on the IRAM 30 m Pico Veleta (PV) radio telescope since 2009. The DSB version of the mixer was employed in a prototype of a four-element focal plane array that was tested on the IRAM 30 m radio telescope. Both SSB and DSB mixers employ the same chip and are based on a wideband single ended probe transition from WR6 full-height waveguide to thin-film microstrip line and on a series array of two Nb/Al-AlOx/Nb junctions. The measured receiver noise for the four-element DSB mixer array pumped by a Gunn oscillator cascaded with a frequency doubler was in the range 25-35 K across the 135-168 GHz LO band. The PdBI and PV receivers equipped with the SSB mixers have measured noise temperatures in the range of 30 K to 60 K and an image sideband rejection below -10 dB over the 129-174 GHz RF band. The measurement results agree well with the predictions obtained through detailed simulations of the SIS receivers based on the standard theory of quantum mixing.

LTE-Advanced 표준을 지원하는 0.13-μm CMOS RF Front-end transmitter 설계

본 논문은 LTE-Advanced 시스템에 적용할 수 있는 2,500 MHz~2,570 MHz 대역 0.13-<TEX>${\mu}m$</TEX> CMOS RF front-end 송신기를 제안하며 I/Q 상향주파수변환기와 구동증폭기로 구성되어있다. 상향주파수변환기는 우수한 선형특성을 얻기 위해 공진회로를 부하로 사용하였으며 국부발진신호의 누설을 줄이기 위해 전류 보상회로를 사용하였다. 또한, 제안하는 구동증폭기는 높은 전류 효율과 우수한 선형특성을 확보하기 위해 Class AB 바이어스 상태로 설계되었다. 측정 결과 제안하는 RF front-end 송신기는 최대 +6 dBm의 출력 파워를 제공하며, +0 dBm 출력 시 이미지 신호 및 국부 발진 누설 신호와 40 dBc의 차이를 보인다. 제작된 칩은 1.2 V의 공급 전압으로부터 36 mA 전류를 소모한다. This paper has proposed a 2,500 MHz ~ 2,570 MHz 0.13-<TEX>${\mu}m$</TEX> CMOS RF front-end transmitter for LTE-Advanced systems. The proposed RF front-end transmitter is composed of a quadrature up-conversion mixer and a driver amplifier. The measurement results show the maximum output power level is +6 dBm and the suppression ratio for the image sideband and LO leakage are better than -40 dBc respectively. The fabricated chip consumes 36 mA from a 1.2 V supply voltage.

A Single-PLL UWB Frequency Synthesizer Using Multiphase Coupled Ring Oscillator and Current-Reused Multiplier

A single phase-locked loop (PLL) frequency synthesizer for a mode-1 multiband orthogonal frequency-division multiplexing (MB-OFDM) ultrawideband (UWB) system is realized in 0.13-mum CMOS. A current-reused multiply-by-1.5 circuit and a multiphase coupled ring oscillator are adopted to reduce the power consumption. For a 4.488-GHz signal, the measured image sideband is -40 dBc. The measured switching time from 3.342 to 4.488 GHz is 1.5 ns. The area is 0.85times0.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the power is 31.2 mW for a 1.2-V supply voltage.

A Compact All-Fiber LPG-AOTF Frequency Shifter on Single-Mode Fiber and Its Application to Vibration Measurement

We demonstrate a compact, all-fiber frequency shifter by cascading a CO2-written long-period grating with a flexural acoustic-wave-induced microbending grating on a single-mode fiber. Carrier and image sideband suppressions of 30.0 and 28.1 dB, respectively, are measured. An all-fiber vibrometer based on this frequency shifter capable of nanometer resolution at frequencies up to megahertz is also demonstrated.

The distribution of ND2H in LDN 1689N

Finding tracers of the innermost regions of prestellar cores is important for understanding their chemical and dynamical evolution before the onset of gravitational collapse. While classical molecular tracers, such as CO and CS, have been shown to be strongly depleted in cold, dense gas by condensation on grain mantles, it has been a subject of discussion to what extent nitrogen-bearing species, such as ammonia, are affected by this process. As deuterium fractionation is efficient in cold, dense gas, deuterated species are excellent tracers of prestellar cores. A comparison of the spatial distribution of neutral and ionized deuterated species with the dust continuum emission can thus provide important insights into the physical and chemical structure of such regions. We study the spatial distribution of the ground-state 335.5 GHz line of ND2H in LDN1689N, using APEX, and compare it with the distribution of the DCO+(3--2) line, as well as the 350 micron dust continuum emission observed with the SHARC~II bolometer camera at CSO. While the distribution of the ND2H emission in LDN1689N is generally similar to that of the 350 microns dust continuum emission, the peak of the ND2H emission is offset by ~10'' to the East from the dust continuum and DCO+ emission peak. ND2H and ND3 share the same spatial distribution. The observed offset between the ND2H and DCO+ emission is consistent with the hypothesis that the deuterium peak in LDN1689N is an interaction region between the outflow shock from IRAS16293--2422 and the dense ambient gas. We detect the J = 4 - 3 line of H13CO+ at 346.998 GHz in the image side band serendipitously. This line shows the same spatial distribution as DCO+(3--2), and peaks close to the 350 mic emission maximum which provides further support for the shock interaction scenario.

Single sideband modulator, a key component of Tore-Supra heterodyne reflectometers

Although single sideband modulation offers a simple solution to active heterodyne devices and is common in devices working over 150 GHz, it has been scarcely used for reflectometers. For a few years, large bandwidth (12–20 GHz), high performance single sideband modulators (SSBM) have been available. For higher frequency application, a sideband rejection around −25 dBc seems necessary to ensure that the image sideband amplitude remains low after a frequency multiplier. A SSBM provided by Miteq Company presents high enough rejection levels to be assembled with frequency multipliers. Based on this SSBM, we developed a simple microwave scheme suitable for all Tore-Supra reflectometers—from 50 to 155 GHz, dedicated either to density profile reconstruction or to density fluctuation measurements. Compared to the double sideband modulator previously used, SSBM offers higher signal to noise ratio and enables fixed frequency measurements, paving the way for new measurement techniques.

Measurements of the sideband conversion gain ratio of a millimeter-wave heterodyne sub-harmonic mixer using a fourier transform spectrometer

A Fourier transform spectrometer, based on a Martin-Puplett polarisation rotation interferometer and using broad-band blackbody noise sources, has been used to study the sideband response i.e., conversion gain, of a room temperature Schottky diode sub-harmonic mixer operating at 300 GHz. The technique enables the response of the mixer to be characterised and preferentially tuned to one sideband, thereby improving the rejection of unwanted spectral components which can be present in the mixer image sideband.

24 GHz serrodyne frequency translator using a 360/spl deg/ analog CPW MMIC phase shifter

A 360/spl deg/ analog CPW MMIC phase shifter is presented for the first time. The compact MMIC employs eight multilayer 3 dB quadrature couplers and was fabricated using low cost GaAs foundry processing techniques. The phase shifter was required to implement a narrow band serrodyne frequency translator at 24 GHz. With an arbitrary, small-shift, frequency translation of +5 KHz, the measured results demonstrated a carrier suppression of 30 dB and an image sideband suppression of 13 dB. This was achieved with a simple linear sawtooth signal, providing 22% of under-modulation. In addition, a 0 dB conversion loss was achieved and almost no control power was required.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Accuracy improvements in homodyne vector NWA with binary switched phase shifters

A nonideal single-sideband modulator using a cascade of binary switched phase shifters as part of a homodyne vector network analyser can operate with an improved image sideband suppression by means of a proper switching-time variation.

In-line acousto-optic frequency shifter in two-mode fiber

An in-line two-mode fiber frequency shifter that uses double conversion in two independent acousto-optic interaction regions is proposed and successfully implemented. Light remains guided in the first-order mode after being shifted in frequency, which provides for easy splicing to single-mode fibers. Net shifts can be up or down in frequency and can be made very small (a fraction of a hertz) by operating in the difference mode. The high acoustic bandwidth (tens of kilohertz) of the single-conversion approach is maintained while image sideband and carrier suppression are potentially improved.

Noise parameters of SIS mixers

It has been shown that low-noise receivers can be constructed at millimeter wavelengths by using mixers containing superconducting tunnel junctions as the nonlinear elements. This is possible because of both the low intrinsic noise of these devices and their potential for high conversion gain. Here, the quantum theory of mixing is used to derive the full-noise parameters and small-signal parameters of sinusoidally pumped SIS (superconductor-insulator-superconductor) junctions. These are then put into a form that allows the theory of two-port linear networks to be brought to bear, allowing calculation of such useful parameters as minimum noise temperature, optimum source impedance, available (or exchangeable) gain at minimum noise, and stability factor. These quantities are properties of the pumped junction that do not depend on the source or load impedance, but do depend on the terminations at the image and harmonic sideband frequencies. The harmonic sidebands are taken to be shorted, and the image termination dependence is studied. Numerical results are presented for both ideal (BSC theory) and practical (measured current-voltage characteristic) junctions. The noise parameters of the cascade connection of an SIS mixer and a (noisy) IF amplifier are considered, leading to a specification of the optimum coupling network between the two. It is noted that the SIS mixer is usually not unconditionally stable, but that oscillation can be avoided by careful design of the IF coupling network. >

Fiber-optic frequency shifter using a grating acoustic scanner

A fiber-optic single-sideband frequency shifter using a grating acoustic scanner has been demonstrated. By using the surface-wave-to-bulk-wave conversion mechanism of a LiNbO(3) scanner, a traveling acoustic bulk wave with a frequency of approximately 42 MHz was generated and was incident at an angle upon an optical fiber. This angle is adjustable by changing the surface-wave frequency to produce phase-matched coupling between two polarization modes or two spatial modes of light in the fiber. An optical coupling efficiency of approximately 70% and carrier and image sideband suppression of 18 and 35 dB, respectively, were realized.

Dual sinusoidal modulation scheme for directional laser Doppler velocimeter

A dual sinusoidal modulation scheme introducing directional sensing of a laser Doppler velocimeter (LDV) employing a semiconductor laser source is described. With this technique using direct current modulation a single-sideband Doppler shift of 8.5 MHz with an image sideband suppression of 29dB is demonstrated.

All-fiber acousto-optic frequency shifter

An all-fiber-optic frequency shifter is demonstrated that uses mode coupling between the LP(01) and LP(11) modes by a traveling acoustic flexural wave guided along the optical fiber. The input and output leads of this frequency shifter are single-mode fibers. Unity mode-conversion efficiency for cw operation is achieved at 8-MHz frequency shift with about 0.25 W of electrical input power. Carrier and image sideband suppression of 15 and 35 dB, respectively, are demonstrated.

A Very Low-Noise Single-Sideband Receiver for 200-260 GHz

A cryogenic Schottky diode mixer receiver has been built for the 230-GHz region with true single-sideband operation and a receiver noise temperature as low as 330 K. Local oscillator power is provided by a frequency tripler, with LO injection and sideband filtering accomplished through quasi-optical interferometers. The image sideband is terminated in a cryogenic load with an effective temperature of 33 K. The IF bandwidth is 600 MHz with nearly flat noise, and the RF band is nearly flat over 50 GHz using backshort tuning of the mixer.

Quasioptical band-rejection filter at 100 GHz

We describe a tunable Fabry–Perot type filter which has application to radio astronomy in the frequency band 80–110 GHz. The filter causes image sideband suppression when used with a heterodyne spectral line receiver having an intermediate frequency of 4.75 GHz. The transmission loss in the signal sideband is about 0.4 dB, while the image sideband rejection is more than 15 dB; there appears to be little if any problem with scattering or distortion of the antenna radiation pattern.