Image Rejection Ratio Research Articles

Reconfigurable microwave photonic mixer based on dual-polarization dual-parallel Mach–Zehnder modulator

Abstract We report a reconfigurable microwave photonic mixer with multiple functions and wide bandwidth. By changing the photodetection configuration, the mixer can be conveniently reconfigured to realize four functions: single-ended mixing, I/Q mixing, double balanced mixing and image rejection mixing. Furthermore, the filter-free system has a wide bandwidth and the ability to perform both frequency up-conversion and down-conversion. The proposed reconfigurable mixer is based on a dual-polarization dual-parallel Mach–Zehnder modulator (DP-DPMZM). The optical signal is modulated by the DP-DPMZM and split into two orthogonally polarized signals, which are combined by a 90° optical hybrid and detected by photodetectors. The experimental results show that the mixer has a wide bandwidth from 2 GHz to 30 GHz with a 30 dB spur suppression, and the image rejection ratio of the image rejection mixer is over 30 dB.

Coherent Optical RF Channelizer With Large Instantaneous Bandwidth and Large In-Band Interference Suppression

RF channelization is regarded as one of the most effective approaches to relieve the difficulty of processing wideband signals in microwave and millimeter-wave receivers. In this paper, a novel coherent optical RF channelizer with broad instantaneous bandwidth and large in-band interference suppression is proposed and demonstrated based on a multichannel photonic image-reject mixer (IRM). A Ku-band RF signal with an instantaneous bandwidth of 5 GHz is sliced into five consecutive subchannels with 1-GHz instantaneous bandwidth by the proposed channelizer. The in-band interference suppression, which relies on the image-rejection ratios of the IRM, is about 25 dB. To the best of our knowledge, the proposed channelizer achieves the highest in-band interference suppression in such wide instantaneous bandwidth.

A 1024-QAM Capable WLAN Receiver with -56.3dB Image Rejection Ratio Using Self-Calibration Technique

A 1024-QAM Capable WLAN Receiver with -56.3dB Image Rejection Ratio Using Self-Calibration Technique

Analysis of mismatch impact on image rejection ratio for passive polyphase filters

SummaryPassive polyphase filters (PPFs) are useful symmetric RC networks for processing analog quadrature signals. Passive polyphase filters are also used to implement differential‐quadrature or quadrature‐differential converters. The quality of these quadrature signals is essential to achieve good performance in modern communication systems. However, mismatch effects can produce notable degradation in the PPF frequency response, and this results in an important reduction in quadrature signal quality, being amplitude balance and phase offset notably affected. Both these errors could be summarized and evaluated together considering image rejection ratio as a figure of merit. This work deepens in the analysis of mismatch impact on PPF, studying image rejection ratio degradation for 2 PPF types, and a systematic method is proposed to obtain the worst case of mismatch in PPFs with any number of stages. It has been validated in a 65‐nm CMOS technology.

Multi-functional D-bandI/Qmodulator/demodulator MMICs in SiGe BiCMOS technology

AbstractThis paper presents the design and characterization of a D-band (110–170 GHz) monolithic microwave integrated direct carrier quadrature modulator and demodulator circuits with on-chip quadrature local oscillator (LO) phase shifter and radio frequency (RF) balun fabricated in a 130 nm SiGe BiCMOS process withft/fmaxof 250 GHz/400 GHz. These circuits are suitable for low-power ultra-high-speed wireless communication and can be used in both homodyne and heterodyne architectures. In single-sideband operation, the modulator demonstrates a maximum conversion gain of 9.8 dB with 3-dB RF bandwidth of 33 GHz (from 119 GHz to 152 GHz). The measured image rejection ratio (IRR) and LO suppression are 19 dB and 31 dB, respectively. The outputP1dBis −4 dBm at 140 GHz RF and 1 GHz intermediate frequency (IF) and the chip consumes 53 mW dc power. The demodulator, characterized as an image reject mixer, exhibits 10 dB conversion gain with 23-dB IRR. The measured 3-dB RF bandwidth is 36 GHz and the IF bandwidth is 18 GHz. The active area of both the chips is 620 µm × 480 µm including the RF and LO baluns. A 12-Gbit/s QPSK data transmission using 131-GHz carrier signal is demonstrated on modulator with measured modulator-to-receiver error vector magnitude of 21%.

All-optical and broadband microwave fundamental/sub-harmonic I/Q down-converters.

Microwave I/Q down-converters are frequently used in image-reject super heterodyne receivers, zero intermediate frequency (zero-IF) receivers, and phase/frequency discriminators. However, due to the electronic bottleneck, conventional microwave I/Q mixers face a serious bandwidth limitation, I/Q imbalance, and even-order distortion. In this paper, photonic microwave fundamental and sub-harmonic I/Q down-converters are presented using a polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM). Thanks to all-optical manipulation, the proposed system features an ultra-wide operating band (7-40 GHz in the fundamental I/Q down-converter, and 10-40 GHz in the sub-harmonic I/Q down-converter) and an excellent I/Q balance (maximum 0.7 dB power imbalance and 1 degree phase imbalance). The conversion gain, noise figure (NF), even-order distortion, and spurious free dynamic range (SFDR) are also improved by LO power optimization and balanced detection. Using the proposed system, a high image rejection ratio is demonstrated for a super heterodyne receiver, and good EVMs over a wide RF power range is demonstrated for a zero-IF receiver. The proposed broadband photonic microwave fundamental and sub-harmonic I/Q down-converters may find potential applications in multi-band satellite, ultra-wideband radar and frequency-agile electronic warfare systems.

Microwave photonics reconfigurable mixer based on polarization modulator

A reconfigurable and stable mixer is proposed and demonstrated in this paper. It mainly consists of a dual-driven Mach–Zehnder modulator and a polarization modulator with several polarization controllers (PC) and polarizers (Pol). According to the theoretical analysis, different functions (such as single ended mixer, balanced mixer, I/Q mixer and image rejection mixer) can be realized by adjusting the PCs and Pols. The simulation results verify the possibility of multi-functions that realized by the reconfigurable mixer. In addition, another research on how the non-ideal parameters affect the image rejection ratio (ISR) and conversion efficiency of the mixer is also carried. The results show that both of them perform better as the extinction ratio gets higher. However, they are incurring a sharp decrease if the DC bias points deviate from the settled values. In the meantime, the results also indicate that the higher modulation indices lead to a better ISR. A 57.12 dB ISR can be achieved with conversion efficiency of − 9.53 dB.

A simple image-reject mixer based on two parallel phase modulators

A simple photonic microwave image-reject mixer (IRM) using two parallel phase modulators is proposed. First, a photonic microwave mixer with phase shift ability is achieved using two parallel phase modulators (PMs), an optical bandpass filter, three polarization controllers, three polarization beam splitters and two balanced photodetectors. At the output of the mixer, two frequency downconverted signals with tunable frequency difference can be obtained. By adjusting the phase difference as 90° and utilizing an electrical 90° hybrid, the useless components can be eliminated, and the image reject operation is realized. The key advantage of the proposed scheme is the usage of PM, which avoid the DC bias shifting problem and make the system simple and stable. A simulation is performed to verify the proposed scheme, a relative − 90° or 90° phase shift can be obtained between the two output ports of the photonic microwave mixer, at the output of the IRM, 60 dB image-reject ratio is obtained.

A High-Performance 650-GHz Sideband-Separating Mixer—Design and Results

We presented the design and experimental results of a new sideband-separating (2SB) mixer for 600-720 GHz (ALMA Band 9). Although designed following the classical quadrature hybrid architecture, the emphasis of the optimization was this time not placed on ultimate phase and amplitude balance in the hybrid, but on the reduction and active suppression of reflections and standing waves. It turns out that, once the phase and the amplitude are sufficiently balanced, the image rejection ratio (IRR) starts being dominated by unbalanced parasitic reflections in the signal path, and further perfection of the hybrid's balance is not the way toward higher IRR. Four operational waveguide blocks were produced. IRRs above 15 dB over the entire band were obtained, depending critically on mixer matching. The noise temperature was not more than 20-30 K above the value expected from the individual mixer devices. With the RF circuits optimized thus, the performance becomes limited by the IF system, where similar interference and standing wave problems seem to occur. These are exacerbated when, for compactness (i.e., in arrays), cryogenic isolators between the mixers and amplifiers are omitted. We show that, because of the high performance of the mixers, an IRR of 10 dB can still be obtained without isolators. When, on the other hand, highly matched amplifiers are used, we expect that the full image rejection performance can be achieved even in array receivers. These 2SB mixers are intended for the future 2SB receivers on the APEX (Chile) and LLAMA (Argentina) observatories and for deployment in any other observatory that would benefit from sideband separation in the 600-720-GHz band.

Built-in-Self-Calibration for I/Q Imbalance in Wideband Millimeter-Wave Gigabit Transmitters

This paper addresses the estimation and compensation of I/Q imbalance, one of the most prominent impairments found in wideband zero-intermediate frequency transceivers (TRxs). The I/Q imbalance encountered in this kind of TRx comprises not only frequency-selective gain and phase imbalance but also delay imbalance. Unless appropriate compensation is applied, the I/Q imbalance significantly degrades the performance of a communication system. This paper presents a novel compensation technique for transmitter I/Q imbalance based on built-in-self-calibration, a low cost and robust compensation technique that enables manufacturing as well as in-field calibration with low computational complexity. The method’s performance is evaluated in a TRx with 64-quadratic-amplitude modulation and 2 GHz of bandwidth implemented with real hardware. The measurements show that the proposed technique achieves an image rejection ratio greater than 35 dB in the entire 2 GHz bandwidth and an error vector magnitude lower than 3%.

Observational demonstration of a high image rejection SIS mixer receiver using a new waveguide filter at 230 GHz

Abstract A new sideband separation method was developed for use in millimeter-/submillimeter-band radio receivers using a novel waveguide frequency separation filter (FSF), which consists of two branch line hybrid couplers and two waveguide high-pass filters. The FSF was designed to allow the radio frequency (RF) signal to pass through to an output port when the frequency is higher than a certain value (225 GHz), and to reflect the RF signal back to another output port when the frequency is lower. The FSF is connected to two double sideband superconductor-insulator-superconductor (SIS) mixers, and an image rejection ratio (IRR) is determined by the FSF characteristics. With this new sideband separation method, we can achieve good and stable IRR without the balancing two SIS mixers such as is necessary for conventional sideband-separating SIS mixers. To demonstrate the applicability of this method, we designed and developed an FSF for simultaneous observations of the J = 2–1 rotational transition lines of three CO isotopes (12CO, 13CO, and C18O): the 12CO line is in the upper sideband and the others are in the lower sideband with an intermediate-frequency range of 4–8 GHz at the radio frequency of 220/230 GHz. This FSF was then installed in the receiver system of the 1.85 m radio telescope of Osaka Prefecture University, and was used during the 2014 observation season. The observation results indicate that the IRR of the proposed receiver is 25 dB or higher for the 12CO line, and no significant fluctuation larger than 1 dB in the IRR was observed throughout the season. These results demonstrate the practical utility of the FSF receiver for observations like extensive molecular cloud surveys in specified lines with a fixed frequency setting.

A 0.1–5.0 GHz SDR transmitter with current-mode power-mixer and self-calibration scheme in 65 nm CMOS

A 0.1–5.0 GHz software-defined radio (SDR) transmitter for private network wireless communication is presented. A V-I converter with the 3rd-order nonlinearity cancellation and current-mode power-mixers are introduced to improve the CIM3 performance. The complete self-calibration scheme is proposed to alleviate the non-ideal effects, including RF resonant frequency self-tuning, LO leakage and image rejection calibration, output power control. With the self-calibration, the transmitter obtains good robustness in RF operation frequency self-tuning and achieves the average LO leakage of −61 dBc and image-rejection ratio (IRR) of 58 dBc. Moreover, the system verifications have demonstrated 24.5 dBm Pout (output power) with 0.7% EVM, 20 dBm Pout with 1.6% EVM, 6.2 dBm Pout with 2.1% EVM for 905 MHz GSM, 905 MHz EDGE and 3.5 GHz LTE signals, respectively. This SDR transmitter has achieved comparable or even better performance in linearity, CIM3 and power consumption compared with the state-of-the-art reconfigurable transmitters.

A Low-Power NB-IoT Transceiver With Digital-Polar Transmitter in 180-nm CMOS

A fully integrated 750~960 MHz wireless transceiver (TRX) is presented for single-tone NB-IoT applications. Effective design methodologies and techniques, from the system level to circuit level, are proposed to address various design challenges while achieving low-power consumption. The TRX consists of a low-IF receiver with 180-kHz signal bandwidth, a digital polar transmitter with 3.75-kHz signal bandwidth, and a fractional-N frequency synthesizer. Passive current mixer is employed in the receiver to improve the linearity and avoid the sensitivity degradation due to 1/ ${f}$ noise. Automatic I/Q imbalance calibration is integrated to improve image rejection ratio (IRR) with the aid of external FPGA. The transmitter is implemented in the digital polar architecture to improve the narrow-band spectrum purity, integrated with an inverse Class-D digital power amplifier (DPA) to achieve high output power and efficiency. A Class-C voltage-controlled oscillator with automatic frequency control assisted the dynamic gate biasing technique is used in the fractional-N PLL frequency synthesizer. Two prototypes are implemented in 180-nm CMOS. By optimizing analog baseband configuration in the receiver and utilizing the revised thermometer-coding and binary-coding-based array placement in the DPA, the receiver achieves 4.0-dB noise figure, 48-dB IRR, and 60-dB PGA dynamic range, and the DPA outputs 23.2dBm maximum saturation power with 44.5% PAE. Furthermore, the transmitter system verifications demonstrate 3.87% error-vector magnitude (EVM) for 891 MHz $\pi $ /4-DQPSK signals at 18.87-dBm output power with −40-dBc out-of-band rejection. The transmitter achieves a dynamic range from −35 to 20 dBm when the demodulation EVM threshold of the system is set to 10%.

Image-Free Microwave Photonic Down-Conversion Approach for Fiber-Optic Antenna Remoting

For commercial and military applications, it is highly desired to acquire broadband radio frequency (RF) signals from remotely located receiving antennas to the central office (CO) for centralized signal processing such as down-conversion. In this paper, a photonic approach for image-free microwave frequency down-conversion is proposed for antenna remoting scenarios. The RF signal is captured by the phase modulator (PM) at remote antenna unit and transmitted over a long fiber link to the CO for performing frequency down-conversion. In analog, with the Hartley architecture in the electronic domain, two in-phase (I) and quadrature (Q) intermediate frequency (IF) components are generated by using an electro-optic polarization modulator (PolM) and two polarizers. To achieve large image rejection ratio (IRR), the digital post-processing technique is introduced to accurately compensate the amplitude and phase imbalances between the I and Q IF signals. In the experiments, a 2-km single-mode fiber link is inserted between the PM and PolM. As the local oscillator signals are set as 35 and 3 GHz, two target sinusoidal signals at 35.5 and 3.1 GHz are applied with two image signals, a sinusoidal signal at 34.5 GHz and a broadband RF signal centered at 2.9 GHz, respectively. Then, both real-time analog and off-line digital processing methods are used to process the generated I and Q IF signals for image rejection, yielding an IRR over 45 and 60 dB respectively, when the sinusoidal image signal is applied. The distortions from the broadband 2.9-GHz image RF signal are also effectively suppressed by using the two processing methods. The proposed approach is capable of covering a wide frequency range from 5 to 40 GHz.

In-Phase and Quadrature Timing Mismatch Estimation and Compensation in Millimeter-Wave Communication Systems

The emerging millimeter-wave (mm-wave) MIMO systems are subject to strong radio frequency (RF) distortions and their compensation is crucial to realize such systems. In the existing literature, several estimation and compensation schemes have been proposed for RF distortions, such as carrier frequency offset, phase noise, and in-phase and quadrature amplitude and phase imbalance (IQI). However, in-phase and quadrature timing mismatch (IQTM) is largely ignored. This paper investigates the effect of the IQTM on mm-wave system performance and reveals that IQTM causes a specific image rejection ratio characteristic, which is substantially different from the regular frequency-dependent IQI and it substantially prolongs the effective channel length. If not compensated, the IQTM can degrade system performance significantly. As a solution to this IQTM problem, this paper proposes novel pilot designs for transmit and receive IQTM estimation, and develops corresponding estimators, transmission protocol, and compensation schemes. MIMO averaging is also proposed, which substantially enhances the IQTM estimation performance. Simulation results show that our proposed pilot designs and estimators offer an efficient solution to the IQTM problem.

Study of Passive CMOS Mixers Effects on Image Rejection Ratio

In this brief, modeling and simulation of quadrature passive mixers are analyzed, focusing on the impact they have on the image rejection ratio (IRR). For this purpose, a 65-nm CMOS technology is used.

Large Bandwidth Photonic Microwave Image Rejection Mixer With High Conversion Efficiency

A photonic microwave image rejection mixer (IRM) with large operating frequency range and high conversion efficiency is presented in this paper. The scheme is achieved by using a photonic microwave phase shifter, which is based on a polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM). Thanks to the large operating frequency range of the photonic microwave phase shifter, the operating frequency of the proposed IRM can extend to 40 GHz. Besides, the system has high conversion efficiency, owing to the suppression of the optical carrier and application of balanced photodetector. To verify the scheme, an experiment is performed. Experimental results demonstrated large operating frequency range (5–40 GHz) and high image rejection ratio (40 dB) of the mixer. Compared with the conventional photonic microwave mixer, a 19-dB improvement of conversion efficiency is realized in the experiment.

A 10-b Fourth-Order Quadrature Bandpass Continuous-Time $\Sigma \Delta $ Modulator With 33-MHz Bandwidth for a Dual-Channel GNSS Receiver

A fourth-order quadrature bandpass continuous-time sigma–delta modulator for a dual-channel global navigation satellite system (GNSS) receiver is presented. With a bandwidth (BW) of 33 MHz, the modulator is able to digitalize the downconverted GNSS signals in two adjacent signal bands simultaneously, realizing dual-channel GNSS reception with one receiver channel instead of two independent receiver channels. To maintain the loop-stability of the high-order architecture, any extra loop phase shifting should be minimized. In the system architecture, a feedback and feedforward hybrid architecture is used to implement the fourth-order loop-filter, and a return-to-zero (RZ) feedback after the discrete-time differential operation is introduced into the input of the final integrator to realize the excess loop delay compensation, saving a spare summing amplifier. In the circuit implementation, power-efficient amplifiers with high-frequency active feedforward and antipole-splitting techniques are employed in the active RC integrators, and self-calibrated comparators are used to implement the low-power 3-b quantizers. These power saving techniques help achieve superior figure of merit for the presented modulator. With a sampling rate of 460 MHz, current-steering digital–analog converters are chosen to guarantee high conversion speed. Implemented in only 180-nm CMOS, the modulator achieves 62.1-dB peak signal to noise and distortion ratio, 64-dB dynamic range, and 59.3-dB image rejection ratio, with a BW of 33 MHz, and consumes 54.4 mW from a 1.8 V power supply.

Residual Self-Interference Analysis for Full-Duplex OFDM Transceivers Under Phase Noise and I/Q Imbalance

In this letter, we investigate the detrimental effects of phase noise (PN) and in-phase/quadrature (I/Q) imbalance (IQI) on full-duplex OFDM transceivers. In particular, we derive a closed-form expression for the average residual self-interference (SI) power and show its functional dependence on the parameters of the radio- frequency impairments and channel taps’ power. Moreover, for perfect digital-domain cancellation, we show that the effects of PN and IQI can be approximately decoupled for small PN and IQI levels and the average residual SI is linearly proportional to the I/Q image rejection ratio and PN 3-dB bandwidth. Our numerical simulations validate the accuracy of the derived closed-form expressions and our findings.

Modular 2SB SIS Receiver for 600–720 GHz: Performance and Characterization Methods

A modular sideband-separating (2SB) receiver for 600–720 GHz has been built and tested. The used modular design allows to characterize all the parts separately, including testing of the superconductor–insulator–superconductor (SIS) junctions individually in a double-sideband mode before building them in to the 2SB assembly. The developed 2SB mixer has a single sideband noise temperature below 380 K in the entire operating band and reaches a level of 200 K in the best point. At the same time, the image rejection ratio (IRR) was demonstrated to be better than 11.5 dB over the entire band. However, we have found a discrepancy between the observed and expected performance. To investigate this problem, we have developed and applied methods to characterize RF and intermediate frequency imbalances of a fully assembled 2SB mixer using the SIS junction properties. As result, the IRR of our mixer was found to be limited by the RF imbalance, which is caused by complex standing waves created by reflections from the SIS junctions, the RF hybrid and the RF absorption load.