Double Sideband Research Articles

Frequency-Modulated Chirp Signals for Single-Photodiode Based Coherent LiDAR System

In this paper, we investigate two categories of linear frequency-modulated chirp signals suitable for single-photodiode based coherent light detection and ranging (LiDAR) systems, namely, the frequency-modulated continuous-wave (FMCW) single-sideband (SSB) signal and the amplitude-modulated double-sideband (DSB) signal, and compare their achievable receiver sensitivity performance. The DSB signal requires a simpler transmitter design, as it is real-valued and can be generated using a single-drive Mach-Zehnder modulator (MZM), while the SSB signal, which is frequency/phase modulated, requires an in-phase and quadrature modulator (IQM)-based transmitter. A theoretical analysis of direct-detection (DD) beating interference (BI) especially the local oscillator (LO) beating with itself, known as LO-LO BI, is presented. Both Monte Carlo simulations and experimental demonstrations are carried out. Good agreement between simulations and experiments is achieved. In comparison with the SSB system, the DSB signal-based system is affected by laser phase noise-induced power fluctuation, and also suffers a significant sensitivity penalty due to nonlinear LO-LO BI. A spectral guard band for mitigating LO-LO BI is necessary for the DSB signal, achieved at the expense of requiring a larger electrical bandwidth. In system tests with a delay line of 385 m, the SSB signal outperforms the DSB signal with a 10 dB better receiver sensitivity in the case with a guard band, and 25 dB better sensitivity without a guard band.

Subharmonic single-balanced LMV with bottom LO injection

This paper proposes a subharmonic single-balanced RF receiver front-end (called LMV) where low noise amplifier is stacked on top of a differential voltage-controlled oscillator (VCO) to re-use the dc bias current. In this subharmonic (SH) LMV, the VCO itself plays the role of the single-balanced subharmonic mixer while generating an LO signal. This bottom LO SH LMV has good LO to IF and LO to RF leakage performances. Also, it can reduce the die size on a chip since it requires only one inductor for the VCO instead of two in the case of top LO LMV.Oscillating at around 2.4 GHz band, the proposed SH LMV is designed using a 65 nm CMOS technology and compared to the top LO SH LMV in terms of phase noise, conversion gain and double sideband noise figure. The SH LMVs consume about 160 μW dc power from a 1-V supply.

Effects of both the drive- and sense-mode circuit phase delay on MEMS gyroscope performance and real-time suppression of the residual fluctuation phase error

This work analyses circuit phase delay for carrier-modulation MEMS capacitive gyroscopes. The temperature-dependent circuit phase delay is a major source of gyroscope output drift, which deteriorates the gyroscope bias instability (BI) and angle random walk (ARW). Effects of both drive-mode and sense-mode circuit phase delay on gyroscope performance when using different signal extraction architectures are analyzed in detail. The online suppression method which combines the so-called modified double sideband (MDSB) extraction architecture in the gyroscope drive mode and closed-loop force-rebalance loop in the sense mode can eliminate the impact of residual fluctuation error of circuit phase delay in real time. When drive-mode circuit phase delay equivalently varies from −20° to 20°, using MDSB decreases the fluctuation of the open-loop zero-rate output (ZRO) by 70% compared to using double sideband (DSB) and by 99.7% with respect to using single sideband (SSB). Meanwhile, improvement for the closed-loop ZRO using MDSB is 92.48% and 94% compared to cases using DSB and SSB, respectively. Furthermore, when the equivalent circuit phase delay of the sense-mode alters from −20° to 20°, ZRO variation for the gyroscope with force rebalanced sense loop and quadrature stiffness nulling loop decreases by 80% in contrast to the case with open loop, which demonstrates the effectiveness of online suppression for circuit phase delay of both the drive-mode and sense-mode. Using the online suppression method, the gyroscope has achieved a BI of 0.16° h−1 and ARW of 0.011° (√h)−1. Furthermore, using the MDSB in the drive mode obtains the best stability compared to using the DSB and SSB as the temperature changes.

Experimental Demonstrations of Matching Filter-Free Digital Filter Multiplexed SSB OFDM IMDD Transmission Systems

Matching filter (MF)-free digital filter multiplexed (DFM) single sideband (SSB) OFDM intensity modulation and direct detection (IMDD) dual-channel transmissions of 51.25Gbit/s over 25km SSMFs are experimentally demonstrated. It is shown that both transmission system impairments and digital filter characteristic variations can only lead to <1dB transmission performance degradations. Compared with the MF-free DFM-based double sideband (DSB) OFDM technique, the SSB technique has a similar receiver DSP complexity and provides almost twice the maximum signal transmission capacity. When compared with a conventional DFM technique incorporating a dedicated shaping and matching filter pair for each channel, the present SSB technique achieves a 10-fold reduction of receiver DSP complexity and 7.82Gbit/s of additional signal transmission throughput. We demonstrate these throughput and complexity advantages by modelling and measurement.

A Differential Voltage-controlled Oscillator as a Single-balanced Mixer

This paper proposes a low power radio frequency receiver front-end where, in a single stage, singlebalanced mixer and voltage-controlled oscillator are stacked on top of low noise amplifier and re-use the dc current to reduce the power consumption. In the proposed topology, the voltage-controlled oscillator itself plays the dual role of oscillator and mixer by exploiting a series inductor-capacitor network. Using a 65 nm complementary metal oxide semiconductor technology, the proposed radio frequency front-end is designed and simulated. Oscillating at around 2.4 GHz frequency band, the voltage-controlled oscillator of the proposed radio frequency front-end achieves the phase noise of ‒72 dBc/Hz, ‒93 dBc/Hz, and ‒113 dBc/Hz at 10KHz, 100KHz, and 1 MHz offset frequency, respectively. The simulated voltage conversion gain is about 25 dB. The double-side band noise figure is ‒14.2 dB, ‒8.8 dB, and ‒7.3 dB at 100 KHz, 1 MHz and 10 MHz offset. The radio frequency front-end consumes only 96 μW dc power from a 1-V supply.

A 1.5–40 GHz frequency modulated continuous wave radar receiver front-end

AbstractThis study presents an ultra-wideband receiver front-end, designed for a reconfigurable frequency modulated continuous wave radar in a 130 nm SiGe BiCMOS technology. A variety of innovative circuit components and design techniques were employed to achieve the ultra-wide bandwidth, low noise figure (NF), good linearity, and circuit ruggedness to high input power levels. The designed front-end is capable of achieving 1.5–40 GHz bandwidth, 30 dB conversion gain, a double sideband NF of 6–10.7 dB, input return loss better than 7.5 dB and an input referred 1 dB compression point of −23 dBm. The front-end withstands continuous wave power levels of at least 25 and 20 dBm at low band and high band inputs respectively. At 3 V supply voltage, the DC power consumption amounts to 302 mW when the low band is active and 352 mW for the high band case, whereas the total IC size is $3.08\, {\rm nm{^2}}$.

A 560 GHz Sub-Harmonic Mixer Using Half-Global Design Method

In this paper, a 560 GHz terahertz sub-harmonic mixer using a new half-global design method is reported. This method combines the advantages of the subdivision design method and the global design method, and greatly enhances the abilities of the optimization of matching variables while retaining the portability of the unit circuit. When the local oscillator (LO) frequency was fixed with 3 mW power at 280 GHz, average up-conversion double sideband (DSB) conversion loss of 8 dB with intermediate frequency (IF) power of −5 dBm was achieved.

Photonic-assisted FSK signal generation based on carrier phase-shifted double sideband modulation

An approach to generate high-speed and wideband frequency shift keying (FSK) signals based on carrier phase-shifted double sideband (CPS-DSB) modulation is proposed and experimentally validated. The core part of the scheme is a pair of cascaded polarization-sensitive LiNbO3 Mach–Zehnder modulators and phase modulators, whose polarization directions of the principal axes are mutually orthogonal to each other. A proof-of-concept experiment is carried out, where a 0.5 Gb/s FSK signal with the carrier frequencies of 4 and 8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of 8 and 16 GHz are generated successfully.

Dual-Band Transmitter and Receiver With Bowtie-Antenna in 0.13 μm SiGe BiCMOS for Gas Spectroscopy at 222 - 270 GHz

This paper presents a transmitter (TX) and a receiver (RX) with bowtie-antenna and silicon lens for gas spectroscopy at 222-270 GHz, which are fabricated in IHP’s $0.13~\mu \text{m}$ SiGe BiCMOS technology. The TX and RX use two integrated local oscillators for 222 – 256 GHz and 250 – 270 GHz, which are switched for dual-band operation. Due to its directivity of about 27 dBi, the single integrated bowtie-antenna with silicon lens enables an EIRP of about 25 dBm for the TX, and therefore a considerably higher EIRP for the 2-band TX compared to previously reported systems. The double sideband noise temperature of the RX is 20,000 K (18.5 dB noise figure) as measured by the Y-factor method. Absorption spectroscopy of gaseous methanol is used as a measure for the performance of the gas spectroscopy system with TX- and RX-modules.

Asymmetric Millimeter-Wave Spectrum in Laser Mode Partition Noise Generated by Fiber Transmission

In this article, we report on the asymmetry of intensity noise spectrum at millimeter-wave (mm-wave) heterodyne carriers. Passively mode-locked laser diode (PMLLD) is employed for a low phase noise mm-wave photonic generation using direct detection. This optical source produces an excess intensity noise known by laser mode partition noise (LMPN) in which its spectrum usually appears as symmetric double side-bands around the beat-note. The propagation over a dispersive medium such as optical fiber can modify the spectral behavior and profile of the LMPN. This article explores the impact of fiber transmission on the distortions of the LMPN in optical and electrical spectrum. Experimental results reveal, for the first time, that the LMPN symmetry is converted to an asymmetric deformation on the generated beating carrier. The mathematical model and numerical simulation are presented to give hints for analyzing this phenomenon. The findings of the simulations and measurements demonstrate the main role of second- and third-order fiber dispersion on the LMPN profile.

Tunable optical single-sideband generation for OOK and PAM4 data channels using an optical frequency comb and nonlinear wave-mixing.

We experimentally demonstrate tunable optical single-sideband (SSB) generation using a tapped-delay-line (TDL) optical filter for 10 and 20 Gbit/s on/off-keying (OOK) signals and a 20 Gbit/s four-level pulse-amplitude-modulated (PAM4) signal. The optical SSB filter is realized by using an optical frequency comb, wavelength-dependent delay, and nonlinear wave-mixing to achieve the TDL function. Moreover, SSB tunability is achieved by adjusting the amplitude, phase, frequency spacing, and number of selected optical frequency comb lines. We show that the one-sideband suppression of a double-sideband (DSB) channel can be enhanced as the number of taps is increased; however, we do measure a ∼1.5% error-vector-magnitude penalty. Furthermore, we demonstrate that the chromatic-dispersion-induced penalty after 80 km standard-single-mode-fiber transmission of a 10 Gbit/s SSB OOK signal without chromatic dispersion compensation has been reduced by >3dB when compared to DSB.

A design of 210 to 235GHzfixed tuned mixer using planar Schottky diode

This paper presents the design of a fixed tuned 210 to 235 GHz subharmonic mixer (SHM). The mixer is designed using GaAs based planar antiparallel Schottky diode pair AP1/G2/0P95 from Rutherford Appleton Laboratory. 3D model of the Schottky diode is discussed and simulated to consider parasitic effects of the diode. Detailed design technique of each of its subsections as well as the integrated mixer circuit is presented. Nonlinear co-simulation of the designed mixer exhibits double sideband (DSB) conversion loss less than 9.2 dB over the frequency band 210 to 235 GHz with 4 dBm of local oscillator (LO) power while the area of the rectangular printed section is 4.224 × 0.35 mm.

Development of 340-GHz Transceiver Front End Based on GaAs Monolithic Integration Technology for THz Active Imaging Array

Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits.

Design of a Multipurpose Photonic Chip Architecture for THz Dual-Comb Spectrometers.

In this work, we present a multipurpose photonic integrated circuit capable of generating multiheterodyne complex Dual-Combs (DC) THz signals. Our work focuses on translating the functionality of an electro-optic tunable DC system into a photonic chip employing standard building blocks to ensure the scalability and cost efficiency of the integrated device. The architecture we analyze for integration is based on three stages: a seed comb, a mode selection stage and a DC stage. This final DC stage includes a frequency shifter, a key element to improve the final detection of the THz signals and obtain real-time operation. This investigation covers three key aspects: (1) a solution for comb line selection on GHz spaced combs using OIL or OPLL on photonic chips is studied and evaluated, (2) a simple and versatile scheme to produce a frequency shift using the double sideband suppressed carrier modulation technique and an asymmetric Mach Zehnder Interferometer to filter one of the sidebands is proposed, and (3) a multipurpose architecture that can offer a versatile effective device, moving from application-specific PICs to general-purpose PICs. Using the building blocks (BBs) available from an InP-based foundry, we obtained simulations that offer a high-quality Dual-Comb frequency shifted signal with a side mode suppression ratio around 21 dB, and 41 dB after photodetection with an intermediate frequency of 1 MHz. We tested our system to generate a Dual-Comb with 10 kHz of frequency spacing and an OOK modulation with 5 Gbps which can be down-converted to the THz range by a square law detector. It is also important to note that the presented architecture is multipurpose and can also be applied to THz communications. This design is a step to enable a commercial THz photonic chip for multiple applications such as THz spectroscopy, THz multispectral imaging and THz telecommunications and offers the possibility of being fabricated in a multi-project wafer.

Turbulence mitigation in a 28 GHz radio‐over‐free‐space optics link using an integrated Mach–Zehnder interferometer and a diversity combining receiver

The authors propose an integrated Mach–Zehnder interferometer and diversity combining receiver to mitigate the atmospheric turbulence-induced fading in a millimetre-wave (mmW) radio-over-free-space optics (RoFSO) link. They use a carrier frequency of 28 GHz as recommended for the fifth-generation wireless access networks and consider two optical mmW signal generation schemes, namely double-sideband (DSB) and single-sideband (SSB). In direct detection (DD)-based RoFSO, the link performance is limited by atmospheric turbulence. They show that the proposed Rx can overcome this detrimental effect, which is verified by investigation of a 10 Gb/s 16-quadrature amplitude modulation orthogonal frequency-division-multiplexing signal at 28 GHz over a 1 km free-space optics link under weak and strong turbulence regimes. For the DSB scenario, the proposed Rx offers improved error vector magnitudes of about 0.8 and 5.7%, and modulation error ratios of 1.3 and 4.9 dB under weak and strong turbulence regimes, respectively, compared with the DD receiver (DD Rx). For the SSB scenario under weak turbulence, the proposed Rx achieves a 4 dB improvement in the receiver sensitivity and four orders of magnitude enhancement in the bit error rate over the DD Rx. The proposed Rx can be integrated on a single chip for further cost reduction.

Theoretical and Experimental Investigations of Interleaved Carrier-Assisted Differential Detection

Self-coherent detection is a promising solution for extending the transmission reach for direct detection system. For these schemes, high carrier-to-signal power ratio (CSPR) is usually required to mitigate the inherent signal-signal beat interference (SSBI) induced from direct detection. Recently, carrier-assisted differential detection (CADD) receiver has been proposed to recover the optical field of complex-valued double sideband (DSB) signals via direct detection. Aiming at relaxing the high CSPR requirement for self-coherent detection systems, we propose an interleaved subcarrier loading scheme for double-sideband signals. At transmitter, only odd subcarriers are loaded with data while even subcarriers are left unused. By utilizing the CADD receiver, signal can be retrieved without the degradation of SSBI, which enables optical field recovery at low CSPRs. In this article, we first show by theory and simulation that the proposed scheme can work under lower CSPRs than the previous SSB self-coherent systems. Meanwhile, the electrical spectral efficiency of the proposed interleaved CADD is almost the same as SSB self-coherent systems. We also illustrate the process of parameter optimization for interleaved CADD, including optical delay, CSPR, and frequency gap. We successfully transmit 100-Gbps 16-QAM OFDM signals over 160-km uncompensated standard single mode fiber (SSMF) at 3.5-dB CSPR.

A Linearity Improvement Front End with Subharmonic Current Commutating Passive Mixer for 2.4 GHz Direct Conversion Receiver in 0.13 μm CMOS Technology

Direct conversion receiver (DCR) architecture is a promising candidate in the radio frequency (RF) front end because of its low power consumption, low cost and ease of integration. However, flicker noise and direct current (DC) offset are large issues. Owing to the local oscillator (LO) frequency, which is half of the RF frequency, and the absence of a DC bias current that introduces no flicker noise, the subharmonic passive mixer (SHPM) core topology front end overcomes the shortcoming effectively. When more and more receivers (RX) and transmitters (TX) are integrated into one chip, the linearity of the receiver front end becomes a very important performer that handles the TX and RX feedthrough. Another reason for the requirement of good linearity is the massive electromagnetic interference that exists in the atmosphere. This paper presents a linearity-improved RF front end with a feedforward body bias (FBB) subharmonic mixer core topology that satisfies modern RF front end demands. A novel complementary derivative superposition (DS) method is presented in low noise amplifier (LNA) design to cancel both the third- and second-order nonlinearities. To the best knowledge of the authors, this is the first time FBB technology is used in the SHPM core to improve linearity. A Volterra series is introduced to provide an analytical formula for the FBB of the SHPM core. The design was fabricated in a 0.13 μm complementary metal oxide semiconductor (CMOS) process with a chip area of 750 μm × 1270 μm. At a 2.4 GHz working frequency, the measurement result shows a conversion gain of 36 dB, double side band (DSB) noise figure (NF) of 6.8 dB, third-order intermodulation intercept point (IIP3) of 2 dBm, LO–RF isolation of 90 dB and 0.8 mW DC offset with 14.4 mW power consumption at 1.2 V supply voltage. These results exhibit better LO–RF feedthrough and DC offset, good gain and NF, moderate IIP3 and the highest figure of merit compared to the state-of-the-art publications.

High Power Efficiency and Dynamic Range Analog Photonic Link with Suppressed Dispersion-Induced Power Fading

An analog photonic link (APL) based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) is proposed and experimentally demonstrated. The proposed APL can suppress the nonlinearity of modulator, compensate the power fading induced by dispersion (PFID), and improve the power efficiency of link, leading to large dynamic range. The PFID and the nonlinearity are suppressed by adjusting the phase of optical carrier (OC) and polarization controller (PC), respectively. In addition, by optimizing the optical carrier to sideband ratio (OCSR) in the DP-DPMZM, the output RF power and the power efficiency of link can be significantly improved while the total optical power received by the photodetector (PD) remains constant. An experiments are performed to demonstrate the feasibility of the APL. The results show that an spurious free dynamic range (SFDR) of 103.2 dB·Hz4/5 for 13.73 GHz is achieved after compensating PFID and nonlinearity, which is 32 dB higher than that of a conventional double sideband (DSB) assisted APL. After OCSR optimizing, the output RF power achieves 13-dB improvement, and the SFDR is further raised to 114.1 dB·Hz4/5.

An active coaxial line phase reference distribution system

The phase reference distribution system (PRDS) provides high accuracy and low drift reference signals for other subsystems in particle accelerators. We proposed an active coaxial line phase reference distribution method to relax the requirements of the RF components. A low jitter reference signal is transmitted over the coaxial line as the forward signal; at the far end, an asymmetric double sideband suppressed carrier signal (DSB-SC) is generated and phase locked to the forward signal as ”reflected” signal. A demo system with 7 clients distributed in ∼30 meters line was developed in Tsinghua Thomson Scattering Source (TTX). The test results show 54fs RMS jitter and 82fs/158fs peak–peak drift (in 24 h/7 days) while the external reference phase drifts ∼80ps.

Performance Improvement of a Down-Conversion Active Mixer Using Negative Admittance

This paper presents a down-conversion active mixer with improved performance for direct conversion receivers in wireless local area networks. The effect of negative admittance on the Gilbert cell mixer performance is investigated in terms of flicker noise, conversion gain, and linearity. The proposed negative admittance is implemented using a modified negative capacitance connected in parallel to a negative resistance, which exhibits a high degree of freedom to achieve high negative capacitance along with low negative resistance. The proposed mixer is designed and simulated using TSMC 0.18 µm CMOS technology in Cadence Spectre-RF at the input frequency of 2.4 GHz and intermediate frequency of 10 MHz. Post-layout simulation results show using the negative admittance can improve the flicker noise more than 16.7 dB at the frequency of 1 kHz. The proposed mixer exhibits a conversion gain of 19.3 dB and a flicker noise corner frequency of 5 kHz. The double-side band noise figure is 7.57 dB at the output frequency of 10 MHz, and the third-order intermodulation intercept point (IIP3) is − 7.5 dBm. The power dissipation is 13.6 mW from the power supply of 1.8 V. Moreover, the linearity of the proposed mixer can be enhanced by choosing the proper values for transconductance of switching quad and negative resistance so that it achieves the IIP3 of + 7.9 dBm with the conversion gain of 7.6 dB.