Local Oscillator Path Research Articles

Microwave Photonic Channelizer With Large Instantaneous Bandwidth Based on AOFS

The microwave photonic channelizer can convert the RF signal into the optical domain for transmission and procession, effectively avoiding the limitation of electronic bottleneck, and realizing the instantaneous reception of ultra-wideband signal or multi-frequency signals, which can be perfectly applied to radar system and electronic warfare. In this paper, a microwave photonic channelizer based on dual-output image-reject mixer is proposed, both the signal path and the local oscillator path are divided into three paths by using an optical coupler. An acousto-optic frequency shifter (AOFS) is used by the optical local oscillator to shift the frequency to the left and right and then enters the image rejection mixer with the signal path. Finally, a 6 GHz bandwidth RF signal is divided into six subchannels with a bandwidth of 1 GHz to achieve simultaneous reception. This scheme needs no optical frequency comb and doubles the channelization efficiency, the image rejection ratio of the sub-channels is about 22 dB, and the spurious-free dynamic range of the system can reach 103.2 dB·Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sup> .

2.4-GHz Low-Power Low-IF Receiver With a Quadrature Local Oscillator Buffer for Bluetooth Low Energy Applications

In this brief, a 2.4-GHz low-power single-quadrature low-IF Bluetooth low energy receiver employing a quadrature local oscillator (LO) buffer is presented for Internet of Things applications. The quadrature LO buffer, which consists of common-source amplifiers with capacitive degeneration, compensating resistors, compensating PMOS transistors and LC tanks, performs quadrature generation and supplies quadrature signals to a single-quadrature mixer, thus eliminating an additional circuitry for quadrature generation in the LO path and saving dc current consumption. The implemented receiver consists of a low-noise amplifier, a G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> -stage, double-balanced current-mode passive mixers, transimpedance amplifiers, an active- RC complex bandpass filter, and the quadrature LO buffer. Fabricated in a 65-nm CMOS process, the implemented receiver achieves a noise figure of 8.16 dB, a conversion gain of 54.5 dB, an image rejection ratio of 32.1 dB, and an input-referred third-order intercept point of -27.5 dBm. It draws a bias current of 2.5 mA from a nominal supply voltage of 0.8 V, and the active die area is 1.65 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

A 2.4-GHz Quadrature Local Oscillator Buffer Insensitive to Frequency-Dependent Loads for Bluetooth Low Energy Applications

In this letter, a 2.4-GHz quadrature local oscillator (LO) buffer insensitive to frequency-dependent loads is presented for Bluetooth low energy (BLE) applications. An LC tank is used as a load in the proposed buffer to provide a sufficient voltage gain and large voltage swing at the operating frequencies of BLE. Furthermore, the effect of the frequency-dependent impedance of the LC tank on the gain and phase mismatches is reduced by adding compensating transistors. The proposed buffer can provide accurate quadrature signals without additional circuitry in the LO path, minimizing the current consumption of the receiver. It is implemented in 65-nm CMOS technology. It achieved a voltage gain of 5.6 dB, a gain mismatch less than 0.3 dB, a phase mismatch less than 1.1°, and an output ${P} _{{1dB}}$ of 3 dBm. It draws an average current of 3.8 mA from a supply voltage of 0.8 V. The active die area is 0.55 mm2.

A Millimeter-Wave Wideband Frequency Conversion Module Based on Waveguide Switched Filters

A wideband frequency conversion module operating at millimeter-wave (MMW) band is proposed in this brief. By up-converting the input intermediate frequency (IF) of 6 GHz with the local oscillator (LO) signal of 13~17 GHz, it can generate the output radio frequency (RF) signal of 32~40 GHz. Firstly, to distinguish the exact position of RF signal from unwanted signal, the detailed spectrum simulation is performed based on the MMW mixer model. After that, some in-band interference signals of 2LO, 3LO-IF and 2LO+2IF overlap with the output RF range are found. To address the issue, a wideband filter is added in LO path to reject LO and 3LO. And more importantly, a switchable waveguide filter integrated in the module is designed to divide the whole RF working band into three sub-bands, thus guaranteeing the output spectrum purity. Through the final measurement, the RF signal power of 6.9~8.5 dBm and the spurious rejection level of 55 dB is obtained.

A G-Band 2-Pixel Heterodyne Receiver with Integrated Local Oscillator Chain

A 2-pixel heterodyne receiver working in the 173–205-GHz band is presented in this paper. This receiver prototype is mainly composed of two balanced Schottky-based quadrature mixers and an integrated local oscillator (LO) chain. Based on sub-harmonically pumped mixing and quadrature coupling schemes, the proposed receiver operates in double sideband (DSB) mode or single sideband (SSB) mode. With combination of an external intermediate frequency (IF) 3-dB quadrature hybrid, the receiver can furtherly operate in sideband separation (2SB) mode. E-plane Riblet short-slot couplers combined with probe transitions are firstly employed in the radio frequency (RF) and LO path to realize quadrature configuration simultaneously; detailed theoretical derivation on 2SB operation is also given. The 2-pixel receiver is fabricated and tested, the measured SSB conversion loss of each channel achieves 12–20 dB when pumped with 18 dBm of input power at Ku-band, and the imbalance of conversion loss is less than 2 dB between all the IF ports. The typical sideband rejection ratio (SRR) is 12–16 dB over the operation frequency band. The corresponding achievements are valuable in the follow-up focal plane array detection system.

Local Oscillator Phase Shifting and Harmonic Mixing-Based High-Precision Phased Array for 5G Millimeter-Wave Communications

This paper presents a 28-GHz low-cost high-precision phased array for fifth-generation millimeter-wave communications. The local oscillator (LO) phase shifting approach and the subharmonic mixing technique are adopted to achieve a full 360° phase-shifting range with up to 10-bit phase resolution and ultralow magnitude deviation. Each phased channel in this array contains a 1-bit 180° intermediate frequency phase shifter and a low-voltage varactor-tuned reflective-type phase shifter at LO path. The LO phase shifting is used to achieve fine phase shifting with low-magnitude variation. The subharmonic mixing enables lower phase range and lower operation frequency at the LO path. The measured root-mean-square phase error and magnitude variation are around 0.3° and 0.1 dB, respectively. The over-the-air phased array calibration and measurement are also performed. The eight-element phased array achieves +/−50° beam scanning angle and fine beam resolution less than 1° step. The gain flatness of the phased array is less than +/−1dB at 1-GHz signal bandwidth. The eight-element array achieves an effective isotropic radiated power of 41 dBm at 10-dB power backoff. The measured error-vector-magnitude is 1.72% with a 500-MHz orthogonal-frequency-division-multiplexing QAM-64 signal.

A Harmonic-Selective Multi-Band Wireless Receiver With Digital Harmonic Rejection Calibration

A 30-mW multi-band receiver based on harmonic selection is presented. The prototype receiver employs a 32-phase non-overlapping local oscillator (LO) and is capable of simultaneously receiving multiple wireless signals arbitrarily located between 600 MHz and 3 GHz. The receiver achieves 2.4-5-dB noise figure (NF) and tolerates as large as -10-dBm out-of-band blockers. Employing a digital harmonic rejection (HR) calibration to overcome phase and amplitude mismatches in the 32-phase LO and down-conversion paths, close to 80 dB of HR is measured.

Broadband lower-IF RF receiver based on microwave photonic mixer and Kramers-Kronig detection.

A broadband lower- intermediate-frequency (IF) radio frequency (RF) receiver with low cost and complexity based on a microwave photonic mixer and Kramers-Kronig (KK) detection is proposed and experimentally demonstrated. The feasibility of the proposed RF receiver is verified by comparing the error vector magnitude (EVM) performance of a down-converted IF signal with and without KK detection. EVM is measured as a function of IF carrier frequency, input local oscillator (LO) power, input RF power, and the coupling ratio between RF and LO paths. With KK detection, EVM can be improved by more than 9.5% when the IF carrier frequency is close to half of the signal bandwidth. This implies that a lower IF frequency can be down-converted with good EVM and that a low-speed photodetector and a low sampling rate analog to digital converter can be used for wideband RF signal reception.

A Fully Packaged 130-GHz QPSK Transmitter With an Integrated PRBS Generator

This letter presents a fully packaged 130-GHz QPSK transmitter (TX) with an on-package Vivaldi antenna for high-density dielectric waveguide (DWG) chip-to-chip and board-to-board interconnects. The TX chip contains a multiplier chain for the local oscillator path, up-conversion mixers, and a two-stage power amplifier. For testing, the chip also includes two $2^{7} - 1$ sequence-programmable high-speed pseudo-random bit generators, each capable of generating 18 Gb/s (limited by test equipment) at energy efficiency of 0.7 pJ/bit. The fully packaged TX achieves a data rate of 36 Gb/s over a 1-m-long DWG link, leading to energy efficiency of 6 pJ/bit.

Phase Noise in Full-Duplex Radios Using Off-the-Shelf Oscillators

This letter analyzes the effect of phase noise (PN) on digital non-linear self-interference (SI) cancellation for low delay spread non-linear SI channels typical of small form factor in-band full-duplex (IBFD) radios in indoor environments. Use of a shared local oscillator (LO) between the transmit and receive radios is assumed, and it is shown that, in theory, un-cancelled SI due to PN can be reduced by optimizing the relative delay between receive LO path and SI channel. Simulations and measurements from hardware IBFD transceivers using realistic LO phase noise characteristics demonstrate that, for these devices/environments, in practice LO phase noise does not limit digital cancellation when using shared local oscillators.

A fully integrated CMOS 60-GHz transceiver for IEEE802.11ad applications

A fully integrated 60-GHz transceiver for 802.11ad applications with superior performance in a 90-nm CMOS process versus prior arts is proposed and real based on a field-circuit co-design methodology. The reported transceiver monolithically integrates a receiver, transmitter, PLL(Phase-Locked Loop) synthesizer, and LO (Local Oscillator) path based on a sliding-IF architecture. The transceiver supports up to a 16QAM modulation scheme and a data rate of 6 Gbit/s per channel, with an EVM (Error Vector Magnitude) of lower than −20 dB. The receiver path achieves a configurable conversion gain of 36∼64 dB and a noise figure of 7.1 dB over 57∼64 GHz, while consuming only 177 mW of power. The transmitter achieves a conversion gain of roughly 26 dB, with an output P1dB of 8 dBm and a saturated output power of over 10 dBm, consuming 252 mW of power from a 1.2-V supply. The LO path is composed of a 24-GHz PLL, doubler, and a divider chain, as well as an LO distribution network. In closed-loop operation mode, the PLL exhibits an integrated phase error of 3.3° rms (from 100 kHz to 100 MHz) over prescribed frequency bands, and a total power dissipation of only 26 mW. All measured results are rigorously loyal to the simulation.

Electronically Tuned Local Oscillators for the NOEMA Interferometer

We present an overview of the electronically tuned local oscillator (LO) system developed at the Institut de RadioAstronomie millimetrique (IRAM) for the superconductor–insulator–superconductor (SIS) receivers of the NOrthern Extended Millimeter Array interferometer (NOEMA). We modified the frequency bands and extended the bandwidths of the LO designs developed by the National Radio Astronomy Observatory (NRAO) for the Atacama Large Millimeter Array (ALMA) project to cover the four NOEMA LO frequency ranges 82–108.3 GHz (Band 1), 138.6–171.3 GHz (Band 2), 207.7–264.4 GHz (Band 3), and 283–365 GHz (Band 4). The NOEMA LO system employs commercially available MMICs and GaAs millimeter MMICs from NRAO which are micro-assembled into active multiplied chain (AMC) and power amplifier (PA) modules. We discuss the problem of the LO spurious harmonics and of the LO signal directly multiplied by the SIS mixers that add extra noise and lead to detections of unwanted spectral lines from higher order sidebands. A waveguide filter in the LO path is used to reduce the higher order harmonics level of the LO at the output of the final frequency multiplier, thus mitigating the undesired effects and improving the system noise temperature.

Polarization-beam-splitter-less integrated dual-polarization coherent receiver.

Conventional dual-polarization coherent receivers require polarization beam splitters for either the signal or the local oscillator path. This severely hinders monolithic integration, since integrated polarization splitting devices often exhibit stringent fabrication tolerances. Here we propose a dual-polarization monolithically integrated coherent receiver architecture that completely avoids the use of polarization splitting elements. Polarization management is instead achieved by adequately engineering the birefringence of the interconnecting waveguides. The resultant receiver is highly tolerant to fabrication deviations and thus offers a completely new route for monolithic integration of dual-polarization receivers without any type of active tuning.

Performance comparison of an all-fiber-based laser Doppler vibrometer for remote acoustical signal detection using short and long coherence length lasers

All-fiber laser Doppler vibrometer systems have great potential in the application of remote acoustic detection. However, due to the requirement for a long operating distance, a long coherence length laser is required, which can drive the system cost high. In this paper, a system using a short coherence length laser is proposed and demonstrated. Experimental analysis indicates that the multi-longitudinal modes of the laser cause detection noise and that the unequal length between two paths (local oscillator path and transmission path) increases the intensity and the frequency components of the noise. In order to reduce the noise, the optical length of the two paths needs to be balanced, within the coherence length of the source. We demonstrate that adopting a tunable optical delay to compensate the unequal length significantly reduces the noise. In a comparison of the detection results by using a short coherence laser and a long coherence laser, our developed system gives a good performance on the acoustic signal detection from three meters away.

Experimental study on the Gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers

In this paper, we present a fully fiber-based one-way quantum-key-distribution (QKD) system implementing the Gaussian-modulated coherent-state (GMCS) protocol. The system employs a double Mach-Zehnder interferometer (MZI) configuration in which the weak quantum signal and the strong local oscillator (LO) go through the same fiber between Alice and Bob, and are separated into two paths inside Bob's terminal. To suppress the LO leakage into the signal path, which is an important contribution to the excess noise, we implemented a scheme combining polarization and frequency multiplexing, achieving an extinction ratio of 70 dB. To further minimize the system excess noise due to phase drift of the double MZI, we propose that, instead of employing phase feedback control, one simply let Alice remap her data by performing a rotation operation. We further present noise analysis both theoretically and experimentally. Our calculation shows that the combined polarization and frequency multiplexing scheme can achieve better stability in practice than the time-multiplexing scheme, because it allows one to use matched fiber lengths for the signal and the LO paths on both sides of the double MZI, greatly reducing the phase instability caused by unmatched fiber lengths. Our experimental noise analysis quantifies the three main contributions to the excess noise, which will be instructive to future studies of the GMCS QKD systems. Finally, we demonstrate, under the ``realistic model'' in which Eve cannot control the system within Bob's terminal, a secure key rate of $0.3\text{bit}∕\text{pulse}$ over a 5km fiber link. This key rate is about two orders of magnitude higher than that of a practical Bennett-Brassard 1984 protocol QKD system.

A 5.2 GHz CMOS I/Q Modulator With Integrated Phase Shifter for Beamforming

This paper presents the design of an I/Q modulator with integrated phase shifter for beamforming. It is targeted at 802.11a WLAN. An efficient beamforming architecture with a linearly controlled 360deg phase shifting range is proposed for linear transmitters. The phase shifting takes place in the local oscillator path at three times lower frequency than the carrier. The phase shifters are implemented as vector modulators in an efficient way by utilizing a current reuse technique. All control currents are provided by a single current steering digital to analog converter by means of time multiplexed sample and hold circuits. The circuit, implemented in 0.25 mum CMOS technology, has a 1 dB output compression point of -7.1 dBm and consumes 61 mA. It has a phase shifting resolution of 10deg with a differential accuracy of 2deg.

A fully integrated 24-GHz phased-array transmitter in CMOS

This paper presents the first fully integrated 24-GHz phased-array transmitter designed using 0.18-/spl mu/m CMOS transistors. The four-element array includes four on-chip CMOS power amplifiers, with outputs matched to 50 /spl Omega/, that are each capable of generating up to 14.5 dBm of output power at 24 GHz. The heterodyne transmitter has a two-step quadrature up-conversion architecture with local oscillator (LO) frequencies of 4.8 and 19.2 GHz, which are generated by an on-chip frequency synthesizer. Four-bit LO path phase shifting is implemented in each element at 19.2 GHz, and the transmitter achieves a peak-to-null ratio of 23 dB with raw beam-steering resolution of 7/spl deg/ for radiation normal to the array. The transmitter can support data rates of 500 Mb/s on each channel (with BPSK modulation) and occupies 6.8 mm /spl times/ 2.1 mm of die area.

Chirp-pulse-compression three-dimensional lidar imager with fiber optics

A coherent three-dimensional (angle-angle-range) lidar imager using a master-oscillator-power-amplifier concept and operating at a wavelength of 1.5 microm with chirp-pulse compression is described. A fiber-optic delay line in the local oscillator path enables a single continuous-wave semiconductor laser source with a modulated drive waveform to generate both the constant-frequency local oscillator and the frequency chirp. A portion of this chirp is gated out and amplified by a two-stage fiber amplifier. The digitized return signal was compressed by cross correlating it with a sample of the outgoing pulse. In this way a 350-ns, 10-microJ pulse with a 250-MHz frequency sweep is compressed to a width of approximately 8 ns. With a 25-mm output aperture, the lidar has been used to produce three-dimensional images of hard targets out to a range of approximately 2 km with near-diffraction-limited angular resolution and submeter range resolution.

Internal calibration techniques for quadrature receiver mismatch errors

The performance of systems requiring the use of quadrature receivers is significantly degraded in the presence of mismatch errors between the In-phase (I) and Quadrature (Q) branches. This paper discusses the mismatch problem and introduces promising solutions. These solutions are independent of communication format, which improves the generality and flexibility of the techniques. Current literature emphasizes estimation of either local oscillator (LO) mismatch or frequency dependent path mismatch using an external calibration signal. This paper develops techniques to estimate both LO mismatch and path mismatch using internally generated calibration signals derived from the system local oscillator. Once the mismatch errors are obtained, LO mismatch can be corrected by analog adjustment and path mismatches are corrected digitally.

A 5-GHz-band multifunctional BiCMOS transceiver chip for GMSK modulation wireless systems

This paper reports the first multifunctional 0.4-/spl mu/m BiCMOS-based transceiver chip developed for 5-GHz-band Gaussian minimum-shift keying modulation wireless systems. The chip integrates a low-noise radio-frequency amplifier, a down-mixer, and an intermediate-frequency (IF) amplifier in the down-converter path; an IF amplifier, a limiter, an up-mixer, and a buffer amplifier in the up-converter path; and a frequency doubler and a local oscillator amplifier in the local oscillator path. The chip featuring gain attenuation as well as standby mode operation uses a single 2.6-5.2-V bias voltage and dissipates 56 mW in receive mode and 66 mW in transmit mode. The transceiver chip size is 3.0/spl times/2.4 mm/sup 2/.