Double Sideband Research Articles

Receive-diversity-aided power-fading compensation for C-band IM/DD OFDM systems.

A receive-diversity-aided power-fading compensation (RDA-PFC) scheme is proposed and demonstrated to eliminate the chromatic dispersion (CD)-induced power fading for C-band double-sideband (DSB) intensity modulation and direct detection (IM/DD) orthogonal frequency division multiplexing (OFDM) systems. By combining the responses before and after a dispersive element using a maximal-ratio combining (MRC) algorithm, the CD-induced power fading dips within the signal bandwidth of around 50 GHz can be effectively compensated for, which results in an up to 17.6-dB signal-to-noise ratio (SNR) improvement for the fading subcarriers after transmission over 10 km of standard single-mode fiber (SSMF). Using the 16 quadrature amplitude modulation (QAM) format, a diversity receiver with the proposed RDA-PFC scheme can support 170.6-Gbit/s OFDM signal transmission over a 10-km SSMF and reduces the bit error rate (BER) by more than an order of magnitude compared with a conventional receiver. Moreover, 208.1-Gbit/s adaptive bit and power loading OFDM signal transmission over a 10-km SSMF is realized by the proposed RDA-PFC scheme, which improves the capacity by 15.3% compared with the case without RDA-PFC at a BER of 3.8 × 10-3. The proposed RDA-PFC scheme shows great potential in CD-induced power-fading compensation for high-speed IM/DD OFDM systems.

Broadband Microwave Photonic Frequency Measurement Based on Optical Spectrum Manipulation and Stimulated Brillouin Scattering

In this article, a broadband frequency measurement system based on optical spectrum manipulation and stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated, which can implement wide-range and high-resolution frequency measurement, and generate corresponding broadband interference signals in some frequency bands, that is, it has versatility. Since the frequency range of the pump light to excite SBS is expanded based on the optical spectrum manipulation and high resolution is ensured by the narrow scattering spectrum of SBS, high-resolution spectrum measurement covering a wide frequency band is finally implemented. In addition, the double sideband pump light can be used as the source of electronic interference signal. In the experiments, the frequency measurement range of the proposed system is tested to be 0.03–44 GHz, and the resolution is up to 3 MHz. Furthermore, the frequency measurement and electronic interference sharing the same work band can be carried out in the ranges of 6.3367–7.8367 GHz and 20.36–22.16 GHz.

Heterodyne performance and characteristics of terahertz MgB2 hot electron bolometers

We have studied THz heterodyne detection in sub-micrometer MgB2 hot electron bolometer (HEB) mixers based on superconducting MgB2 films of ∼5nm (HEB-A), corresponding to a critical temperature (Tc) of 33.9 K, and ∼7nm (HEB-B), corresponding to a Tc of 38.4 K. We have measured a double sideband (DSB) receiver noise temperature of 2590 K for HEB-A and 2160 K for HEB-B at 1.6 THz and 5 K. By correcting for optical losses, both HEBs show receiver noise temperatures of ∼1600 K referenced to the front of anti-reflection (AR)-coated Si lenses. An intermediate frequency (IF) noise bandwidth of 11 GHz has been measured for both devices. The required local oscillator (LO) power is about 13 μW for both HEBs. We have also measured a DSB receiver noise temperature of 3290 K at 2.5 THz and 5 K but with an AR-coated lens optimized for 1.6 THz. Besides, we have observed a step-like structure in current voltage (IV) curves, which becomes weaker when the LO power increases and observable only in their differential resistance. Such a correlated structure appears also in the receiver output power as a function of voltage, which is likely due to electronic inhomogeneities intrinsic to the variations in the thickness of the MgB2 films. Different behavior in the IV curves around the low bias voltages, pumped with the same LO power at 1.6 and 5.3 THz, was observed for HEB-B, suggesting the presence of a high-energy σ-gap in the MgB2 film.

Improved Weighted Volterra DFE for C-Band 100-Gbit/s PAM-4 Transmission Over 60-km SSMF

To cope with the nonlinear distortions and the chromatic dispersion (CD) induced power fading in double-side band (DSB) intensity modulation and direct detection (IM/DD) transmission systems, high-performance Volterra decision-feedback equalizers (VDFEs) are widely applied. However, similar as linear DFE, the VDFEs suffer from error propagation in the case of wrong decisions. In this letter, to reduce the error propagation probability of VDFEs, we propose and experimentally demonstrate a diagonally-pruned improved weighted VDFE (DP-IWVDFE) in a C-band 4-level pulse amplitude modulation (PAM-4) transmission system. By replacing the hard-decision output by the soft-decision feedback symbol based on a compressed sigmoid nonlinear function in DP-IWVDFE, the error propagation probability can be significantly reduced, which lowers the bit error ratio (BER) by a factor of around two as compared to the DP-VDFE. Besides, 100-Gbit/s PAM-4 transmission over 60-km standard single-mode fiber (SSMF) using DP-IWVDFE is realized with the achieved BER below 3.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 10^{-3}$ </tex-math></inline-formula> , achieving around 3.8-dB, 1.5-dB, and 1-dB improvements of the receiver sensitivity over the polynomial DFE (PDFE), improved weighted PDFE (IWPDFE), and DP-VDFE, respectively.

Lensless Short-Range Reflection-Mode Imaging at 275 GHz Using CMOS Concurrent Transceivers

Lensless short-range reflection-mode imaging through a cardboard cover is demonstrated at 275 GHz using a pair of concurrent complimentary metal–oxide–semiconductor transceiver pixels separated by ∼5 mm on a printed circuit board (PCB). This is the first such demonstration at frequencies above 100 GHz. The separation between the imaged object and pixels is ∼1 cm and the operation at 275 GHz allows the lateral resolution to be reduced to ∼2 mm due to a smaller wavelength. A concurrent transceiver pixel incorporating a transmitter with an effective isotropic radiated power of −18.9 dBm and a receiver with a double sideband noise figure of ∼51 dB in an area of 0.45 × 0.49 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is used. The reflected signals from a target must be greater than the transmitted signal directly coupled to the receiver, and this isolation between the transmitter and receiver limits the imager range and contrast. Full-wave electromagnetic simulations (ANSYS high-frequency structure simulator (HFSS)) of a PCB with a transmit and receive rectangular patch antenna with a separation of ∼5 mm show that ∼65 dB isolation at 275 GHz can be achieved. This should be sufficient to image a target with a radar cross section of 2 mm × 2 mm with a reflection coefficient of 0.1 that is 1-cm away. This work points to a path for incorporation of millimeter and submillimeter wave imaging in a handheld device.

Photonic-Assisted Scheme for Simultaneous Self-Interference Cancellation, Fiber Dispersion Immunity, and High-Efficiency Harmonic Down-Conversion.

A photonic approach to the cancellation of self-interference in the optical domain with fiber dispersion immunity and harmonic frequency down-conversion function is proposed based on an integrated, dual-parallel, dual-drive Mach-Zehnder modulator (DP-DMZM). A dual-drive Mach-Zehnder modulator (DMZM) is used as an optical interference canceller, which cancels the self-interference from the impaired signal before fiber transmission to avoid the effect of fiber transmission on the cancellation performance. Another DMZM is used to provide carrier-suppressed, local-oscillation (LO)-modulated, high-order double optical sidebands for harmonic frequency down-conversion to release the strict demand for high-frequency LO sources. By regulating the DC bias of the main modulator, the signal of interest (SOI) can be down-converted to the intermediated frequency (IF) band after photoelectric conversion with improved frequency-conversion efficiency, immunity to the fiber-dispersion-induced power-fading (DIPF) effect, and effective signal recovery. Theoretical analyses and simulation results show that the desired SOI in the X and K bands with a bandwidth of 500 MHz and different modulation formats can be down-converted to the IF frequency. The self-interference noise with the 2 GHz bandwidth is canceled, and successful signal recovery is achieved after a 10 km fiber transmission. The recovery performance of down-converted signals and the self-interference cancellation depth under different interference-to-signal ratios (ISRs) is also investigated. In addition, the compensation performance of DIPF is verified, and a 6 dB improvement in frequency conversion gain is obtained compared with previous work. The proposed scheme is compact, cost-effective, and thus superior in wideband self-interference cancellation, long-range signal transmission, and effective recovery of weak desired signals.

Microwave Frequency Dividers With Reconfigurable Fractional 2/N and 3/N Division Ratios

Two microwave photonic signal processing structures, which are capable to realise microwave frequency division with a tunable integer or non-integer division ratio, are presented. They are based on applying an input RF signal to a Mach Zehnder modulator, which is biased to generate a carrier-suppressed double sideband (DSB) or single sideband (SSB) optical signal. The carrier-suppressed DSB optical signal consists of the upper and lower 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> order sidebands with a separation of two times the input RF signal frequency. The carrier of the SSB optical signal is suppressed by a fibre Bragg grating (FBG) connected to the modulator output. Hence the FBG output consists of the upper 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> order and lower 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> order sidebands with a separation of three times the input RF signal frequency. The carrier-suppressed DSB or SSB optical signal is injected into a semiconductor laser. The semiconductor laser is oscillated in the period-one state that generates a number of equally spaced frequency components, which are frequency locked by the injection light wave. Beating of these optical frequency components at the photodetector produces an RF signal with a frequency of 2/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> or 3/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> times the input RF signal frequency where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> can be between 3 and 6. Hence the 2/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> frequency divider can realise 2/3, 1/2, 2/5 and 1/3 frequency division operation, and the 3/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> frequency divider can realise 3/4, 3/5 and 1/2 frequency division operation. The proposed 2/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> and 3/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> frequency dividers have a very simple structure compared to the reported photonics-based microwave frequency divider that can realise both integer and non-integer frequency divisions. The frequency division ratio can be tuned by simply adjusting the forward bias current of the semiconductor laser subject to optical injection. Experimental results demonstrate the two proposed structures can realise microwave frequency division with a tunable integer and non-integer division ratio for different input RF signal frequencies of 10 to 18 GHz, and over 60 dB output signal-to-noise ratio performance. More than 27 dB suppression in the unwanted frequency components around the frequency divided signal is also demonstrated.

DCT-Based Air Interface Design for Function Computation

With the integration of communication and computing, it is expected that part of the computing is transferred to the transmitter side. In this paper we address the general problem of Frequency Modulation (FM) for function approximation through a communication channel. We exploit the benefits of the Discrete Cosine Transform (DCT) to approximate the function and design the waveform. In front of other approximation schemes, the DCT uses basis of controlled dynamic, which is a desirable property for a practical implementation. Furthermore, the proposed modulation allows to recover both the measurement and the function in a single transmission. Our experiments show that this scheme outperforms the double side-band (DSB) modulation in terms of mean squared error (MSE). This can also be implemented with an agnostic receiver, in which the function is unkown to the receiver. Finally, the proposed modulation is compatible with some of the existing transmission technologies for sensor networks.

Analytical Study and Noise Mitigation for Complex-Valued Optical DSB Transmission With Carrier-Assisted Differential Detection Receiver

A thorough analysis of the system model for complex-valued optical double-sideband (DSB) transmission with carrier-assisted differential detection (CADD) receiver under the influence of laser phase noise and fiber chromatic dispersion (CD) is presented. It is shown that the interaction of laser phase noise and CD leads to the phenomenon of phase-to-amplitude (P2A) noise and equalization-enhanced phase noise (EEPN). The achievable performance of the complex-valued optical DSB transmission with CADD receiver under the influence of EEPN and P2A noise is estimated by a closed-form expression, and it is verified by simulation that the results show an inaccuracy of less than 1 dB for a wide range of system parameters. In addition, in order to mitigate the EEPN and P2A noise, we propose a pre-decision aid-based simplified blind phase search (BPS) algorithm, commonly referred to as PDA-BPS algorithm. The PDA-BPS algorithm allows for reduced complexity by decreasing the number of symbols entering the BPS algorithm. Theoretical derivation and simulation verification illustrate that the PDA-BPS algorithm can achieve similar mitigation performance to the BPS algorithm with lower complexity. Specifically, under the condition that classification decision threshold R is equal to 0.25, the complexity can be reduced by 40%/16.6% with 1 MHz/7 MHz linewidth for 16-QAM and 29%/10.9% with 0.5 MHz/3 MHz linewidth for 64-QAM.

Port‐assignment modelling of anti‐parallel Schottky barrier diode and 0.3‐THz sub‐harmonic mixer design

This letter presents a new port-assignment model of an anti-parallel Schottky barrier diode (AP-SBD) and a 0.3-THz sub-harmonic mixer (SHM) as the application design. Using the proposed method, the AP-SBD is accurately modelled compared to conventional modelling methods. Because the characteristics of an AP-SBD have the greatest impact on mixer performance, an accurate modelling method for AP-SBD helps design SHMs with good performance. To verify the proposed modelling in the terahertz region, a 0.3-THz SHM based on the modelled AP-SBD is designed and assembled. The measurement result reveals that the optimal double-sideband (DSB) conversion loss of the mixer is 6.7 to 10.1 dB within 279 to 318 GHz when the fixed local oscillator (LO) signal is 6.4 dBm at 152 GHz. All measurement results confirm that the proposed methodology is concise and feasible for the design of terahertz SHMs.

A High Performance Silicon Nitride Optical Delay Line With Good Expansibility

In this paper, based on the double strip silicon nitride platform, we designed and fabricated a low loss continuously tunable broadband optical delay line, which contains a 5-bit optical switched delay line and a single tunable optical ring resonator working at “off-resonance”. Optical double sideband modulation link measurement results show it can achieve continuous delay tuning of 395.5 ps and in-band delay fluctuations of about 4 ps and 1 ps were obtained in 8 GHz and 5 GHz working bandwidths, respectively. In addition, the proposed optical delay line has a low on-chip insertion loss of 3 dB and a very low optical loss delay ratio of 0.0022 dB/ps. Moreover, it's delay tuning range can be easily increased by cascading more thermo-optic switches. The delay bandwidth can be expanded by adopting the optical single sideband modulation or increasing the FSR of the optical ring resonator. This integrated tunable optical delay line with good overall performances and expand ability shows great potential for microwave photonic applications.

ФОРМИРОВАНИЕ ОДНОПОЛОСНОЙ КВАДРАТУРНОЙ ФАЗОВОЙ МАНИПУЛЯЦИИ РАДИОСИГНАЛОВ НА ПОДНЕСУЩИХ ЧАСТОТАХ В КОГЕРЕНТНОЙ ОПТИЧЕСКОЙ СИСТЕМЕ КОММУНИКАЦИИ

The coherent optical communication technology allows to create a transmission system overlong distances with high bandwidth. Higher order modulation formats such as Quadrature PhaseShift Keying (QPSK) provide high data rates in a simple, reliable and cost-effective manner. Thesemulti-bit modulation methods are transmitted as a symbol implementing simple in-phase andquadrature (IQ) modulation formats. To increase throughput in coherent optical systems, opticalsubcarrier multiplexing is used, when several radio signals are multiplexed on one optical carrier.This multiplexing is limited by double sideband, resulting in reduced received subcarrier powerand degraded carrier-to-noise ratio. To accumulate these effects, many ways of implementingoptical single sideband (OSSB) are proposed. The paper proposes an analysis of a coherent opticaltransmission system for generating single-sideband QPSK modulation using an optical I/Qmodulator and M-ary RF pulse shaping. The pseudo-random bit sequence generator generates a10 Gb/s modulation baseband signal. Each bit sequence is converted into an M-ary sequence ofsymbols from binary signals using phase shift keying (PSK). The M-ary pulse generator generatesa multi-level pulse shaping according to the sequence of M-ary input symbols. Electrical pulsesare applied to the electrodes of the electro-optical modulator according to the Mach–Zehnderinterferometer (MZM) scheme. The I/Q modulator operated at the quadrature operating point inboth the in-phase and quadrature branches, with an extinction ratio 60 dB and 3 V switching voltage.The light wave is emitted by a CW laser with a wavelength of 1550 nm.

Offset double sideband carrier assisted differential detection with field recovery at low carrier-to-signal power ratio.

Four system frameworks based on carrier assisted differential detection (CADD) receivers for offset double sideband (DSB) signal transmission, including offset DSB asymmetric CADD (offset DSB A-CADD), offset DSB symmetric CADD (offset DSB S-CADD), offset DSB parallel double delay asymmetric CADD (offset DSB PDD-A-CADD), and offset DSB parallel double delay symmetric CADD (offset DSB PDD-S-CADD) are proposed to reduce the requirement for carrier-to-signal power ratio (CSPR) and improve the spectral efficiency (SE) of the self-coherent detection. These frameworks accommodate signal-signal beat interference (SSBI) and efficiently solve the noise enhancement by placing a frequency gap as wide as the signal bandwidth in the middle of the left and right sideband signal. Massive theoretical derivation and simulation verification illustrated that compared with previous interleaved A-CADD, our system achieve field recovery under the condition of 0 dB CSPR with the improvement of SE by 5%, and the OSNR sensitivity is improved by 4.5 dB with 20% forward error correction (FEC) threshold. In addition, due to the devices' limited bandwidth (BW), the information-bearing signal is attenuated at the high-frequency region. And since SSBI has less influence on the signal in the high-frequency region, the frequency gap of the four offset DSB CADD schemes are compressed to utilize as much low-frequency resource as possible and improve the SE. Efficient compression of the frequency gap from 50% to 32.3% with 20% FEC threshold and 50% to 37.7% with 7% FEC threshold at 0 dB CSPR is achieved, and only a slight performance degradation is observed. At this time, the SE is improved by 22.7% and 17.3% with different FEC thresholds, respectively, compared with the 5% frequency gap interleaved A-CADD.

Analysis of the Flux Density and Back EMF in Eccentric Permanent Magnet Machines Based on 2-D Air-Gap Modulation Theory

In this article, the unified 2-D air-gap field modulation (AFM) model is established to analyze the flux density and back electromagnetic force (EMF) in both rotor-permanent magnet (PM) and stator-PM machines under eccentricity. For the temporal distribution of flux density, the static eccentricity (SE) causes amplitude unbalance, while the dynamic eccentricity (DE) leads to sideband harmonic components. The sideband harmonic is commonly regarded as a double-sideband (DSB) modulation effect, but it may be a single sideband (SSB) modulation effect in some specific cases, which is analytically and experimentally proved in this article. More importantly, a quantitative description of how eccentricity influences the phase back EMF is provided, which is only qualitatively expressed in the existing literature. A standardized analysis process is also given, which can be used for different machine topologies. The aforementioned conclusions are validated by the simulations and experiments on two prototyped machines, namely, an 18-slot 20-pole (18s/20p) surface-mounted PM (SPM) machine and a 12s/10p flux-switching PM (FSPM) machine.

Stimulated Brillouin Scattering Based Image-Reject Microwave Signal Harmonic Down-Converter

We propose and demonstrate a photonic microwave signal harmonic down-converter with image rejection capability via stimulated Brillouin scattering (SBS). A dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM) is driven by a radio frequency/image (RF/IM) signal and a local oscillation (LO) signal to realize equivalent phase modulation and 4th-order double sideband modulation respectively. The optical carriers from the two arms of the DP-DPMZM can cancel out each other after polarization combining, thereby increasing the useful optical signal power in photodetection. Since the beating notes between the IM-modulated signals and LO-modulated 4th-order sidebands interfere destructively, the down-converted IM signals disappear naturally, which makes the down-converted image parts be suppressed in optical domain. By using an SBS-based dual-band microwave photonic filter to suppress the RF modulated -1st-order sideband and amplify the +1st-order sideband, destructive interference can be broken. Therefore, the RF signal over frequency range of 21-28 GHz can be down-converted to intermediate frequency (IF) band, and the image rejection ratio (IRR) can be also improved to more than 55 dB. Under -160 dBm/Hz noise floor, the SFDR is 105.1 dB·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> .

Comparing the performance of 850 GHz integrated bias-tee superconductor-insulator-superconductor (SIS) mixers with single- and parallel-junction tuner

We present and compare the design and performance of two 850 GHz radial probe fed superconductor-insulator-superconductor mixers, where the antenna is aligned perpendicular to the E-Plane of the input full-height rectangular waveguide connected to a multiple flare-angles smooth-walled horn. Both designs are comprised of 0.5 µm2 hybrid niobium/aluminium-nitride/niobium-nitride tunnel junction, fabricated on top of a niobium titanium nitride ground plane with an Al wiring layer. The entire superconducting circuit is supported with a 40 µm thick quartz substrate. The major difference between the two designs is the method used to cancel out the parasitic junction capacitance for broadband performance. The first design utilises two identical junctions connected in parallel with a short transmission line to convert the capacitance of one junction into the equivalent inductance of the other junction, commonly known as the twin-junction tuning scheme; whilst the second design employs an end-loaded scheme with only one tunnel junction. We found that both methods offer similar radio frequency performances, with close to 2× the double sideband quantum noise temperature, but the twin-junction design is more resilient to fabrication tolerances. However, the end-loaded design offers a much better intermediate frequency (IF) bandwidth performance, made possible by the sub-micron and high current density tunnel junction technology. The improved IF performance is important for many millimetre (mm) and sub-mm observatories, such as future upgrades of Atacama Large Millimetre/sub-mm Array receivers, as well as forthcoming space-borne far-infrared missions. Therefore, we conclude that the single-junction mixer design is the preferred option for THz applications, as long as the fabrication error can be minimised within a certain limit.

Photonic scheme for broadband frequency response measurement of PDs.

We report a scheme to measure the broadband frequency response of photodetectors (PDs) with the capacity of self-calibration. The optical carrier at f 0 is modulated through one modulator, and this modulator is driven by a microwave signal with a fixed frequency f 1 to produce the carrier-suppressed double sideband optical signals f 0-f 1 and f 0+f 1. The frequency interval of the optical signals is 2f 1. Subsequently, the two optical signals are sent to another modulator driven by a swept microwave signal f m. Two pairs of carrier-suppressed double sideband signals with a high signal-to-noise ratio are generated. The frequencies of these signals are f 0-f 1-f m,f 0-f 1+f m, f 0+f 1-f m, and f 0+f 1+f m. After the PD under test, the frequency response can be extracted from the amplitude of the microwave signals at 2f 1, 2f 1-2f m, and 2f 1+2f m. Two PDs in our laboratory are experimentally characterized from 0.1 to 40GHz with a resolution of 100MHz. Compared with the traditional vector network analyzer swept method, the proposed method extends the measurement range from f m(max) to 2f 1+2f m(max) and has the capacity of self-calibration to eliminate the influence caused by the modulator frequency response on the measurement results.

A Comparison of Off-Chip Differential and LC Input Matching Baluns in a Wideband and Low-Power RF-to-BB Current-Reuse Receiver Front-End

A wideband and low-power RF-to-baseband (BB) current-reuse receiver (CRR) front-end is proposed, and its performance is verified using two matching networks, one with an LC balun and on-chip biasing inductor, CRR1, and another with a differential balun and without on-chip biasing inductor, CRR2, requiring less area. The transimpedance amplifier (TIA) and low-noise transconductance amplifier (LNTA) share the bias current from a single supply to reduce power consumption. It employs both an active-inductor (AI) and a 1/f noise-cancellation technique to improve the NF and RF bandwidth performance. A passive mixer is utilized for RF to BB conversion, which does not require any DC power and voltage headroom. Both CRR1 and CRR2 are fabricated in TSMC 130 nm CMOS technology on a single die and packaged using a QFN48. CRR1 occupies an active area of 0.54 mm2. From 1 to 1.7 GHz, it achieves a conversion gain of 41.5 dB, a double-sideband (DSB) NF of 6.5 dB, S11&lt;−10 dB, and an IIP3 of −28.2 dBm, while the local-oscillator (LO) frequency is at 1.3 GHz. CRR2 occupies an active area of 0.025 mm2. From 0.2 to 1 GHz, it achieves an average conversion gain of 37 dB, an average DSB NF of 8 dB, and an IIP3 of −21.5 dBm while the LO frequency is at 0.7 GHz. Both CRR1 and CRR2 consume 1.66 mA from a 1.2 V supply voltage.

Photonic Integrated Frequency Shifter Based on Double Side Band Modulation: Performance Analysis

In this research, we present an analysis of a photonic integrated frequency shifter as a stage for a THz dual comb generator. We studied the performance of the PIC by simulating it with standard building blocks, and aimed toward an improvement of the output signal quality. We revised two approaches of the PIC by simulating two modes of generating a double side band modulation suppressed carrier (DSB-SC) with a Mach Zehnder modulator structure (MZM). One approach was using a single Electro-Optic Phase Modulator (EOPM) on an MZM structure (SE-MZM), and the other one was using Double EOPM (DE-MZM). We found a cleaner spectrum with the DE-MZM, since this structure is usually applied to reduce the chirp effect in optical communication systems. We obtained 23 dB of side mode suppression ratio SMSR with one filter, and 44 dB of SMSR with a two-stage filter. In the case of DE-MZM, we obtained a clean tone on intermediate frequency (IF) free of spurious sidebands and comb in IF frequency with 10 dB more power compared to SE-MZM.

Complexity curtailed MLSE equalizer based on a compact look-up-table for C-band DSB IM/DD transmission.

Chromatic dispersion appears to be a major performance limiting problem in optical intensity modulation direct detection (IM/DD) transmission systems, especially for a double-sideband (DSB) signal. We propose a complexity-reduced look-up-table based maximum likelihood sequence estimation (LUT-MLSE) for DSB C-band IM/DD transmission based on pre-decision-assisted trellis compression and a path-decision-assisted Viterbi algorithm. To further compress the size of the LUT and reduce the length of the training sequence, we proposed a finite impulse response (FIR) and LUT hybrid channel model for the LUT-MLSE. For PAM-6 and PAM-4, the proposed methods can compress the size of the LUT into 1/6 and 1/4, and reduce the number of multipliers by 98.1% and 86.6% with slight performance degradation. We successfully demonstrate a 20-km 100-Gb/s PAM-6 and a 30-km 80-Gb/s PAM-4 C-band transmission over dispersion-uncompensated links.