Vector Signal Generator Research Articles

A DDS-based integrated microwave source for fast frequency sweeping in quantum magnetic-resonance systems

Magnetic resonance is a fundamental method to manipulate qubits in spin-based quantum information processing. In such areas, the functionality of fast frequency sweeping is required to determine the resonance of the system. We provide a hardware-synchronized sweeping microwave source with a minimal latency in the sub-μs level based on the direct digital synthesizer technique. The output frequency can be up-converted to match the requirement for particular applications. We demonstrate this module in an optically detected magnetic resonance experiment for a nitrogen-vacancy center, and the spectrum is obtained much faster than conventional schemes with high resolution. Comparing with commercial vector signal generators, our module is highly integrated on a single board with a limited area, especially suitable for engineering of quantum sensors and devices in the future.

Implementation of real-time high-speed ultrasound communications through tissue

In this work, we propose a novel implementation of both a transmitter and receiver with field programmable gate arrays (FPGAs) to achieve real-time continuous high-definition (HD) video transmission through tissue, which can enable HD and higher frame rate wireless capsule endoscopy. We used a Texas Instruments AFE58JD48EVM 16 channel analog front end (AFE) evaluation board as the receiver connected to a Xilinx ZCU106 Zynq Ultrascale MPSoC development board in which we implemented a digital down converter (DDC), OFDM demodulator, maximum ratio combiner and low-density parity-check (LDPC) decoder. For the transmitter, we used an Analog Devices EVAL-AD9166 vector signal generator evaluation board, which has a built-in 4.3 dBm output power amplifier as a transmitter connected to another ZCU106 development board in which we implemented a LDPC encoder, OFDM modulator and digital up converter (DUC). The modulated signal was transmitted through a tissue-mimicking abdominal phantom using a 2-mm microcrystal transducer and received with a Sonic Concepts IP103 64 channel phased array at a center frequency of 3.2 MHz. We achieved the continuous transmission of up to over[OML1] 6 Mbps error free payload data rate after LDPC decoder which is used to carry HD video streams through ultrasound.

W-band simultaneous vector signal generation and radar detection based on photonic frequency quadrupling.

In this paper, we propose and experiment with a dual-functional system that can simultaneously implement vector signal generation and radar detection based on frequency quadrupling. In the experimental demonstration, a generated W-band quadrature-phase-shift-keying (QPSK) vector signal is transmitted wirelessly over 1 m with a bit-error rate (BER) below 3.8 × 10-3. A radar working in the W band is investigated with a range resolution of 0.94 cm. To the best of our knowledge, this is the first time that simultaneous QPSK vector signal generation and radar detection in the W band has been realized.

Broadband Measurement of Error Vector Magnitude for Microwave Vector Signal Generators Using a Vector Network Analyzer

A frequency-domain method is proposed for the broadband measurement of Error Vector Magnitude (EVM) for Vector Signal Generators (VSGs). The technique is based on frequency-swept narrowband acquisitions performed with a Vector Network Analyzer (VNA) by exploiting a stable (yet unknown) reference signal to obtain phase-repeatable measurements, eventually allowing to refer the residual distortion contribution of the analog VSG output to its digital input. The method leverages on the formulation of a novel measurement-based model, which accounts for the IQ imbalance effect and allows to separate it from the actual distortion within the VSG, ultimately yielding accurate broadband EVM measurements at microwave carrier frequencies without any time-domain waveform reconstruction, completely avoiding the use of broadband receivers and corresponding calibration.

Novel two-tone measurement of the nonlinearity and memory effects of mixers in different amplitude regions of large carrier signals.

The conventional two-tone test method cannot measure the amplitude and phase of IM3 products under different operating conditions. The nonlinearity and memory effects of mixers under different operating conditions have not been characterized in existing research. This paper presents a new two-tone measurement method for characterizing the nonlinearity and memory effects of mixers under the excitation of large carrier signals of different amplitudes. This new test method differs from the conventional two-tone test in that the two-tone test signal is superimposed on a large carrier signal. The role of the large carrier signal is to excite mixers into different operating conditions. The amplitude and phase of the IM3 product of the mixer could be measured to characterize the nonlinearity and memory effects under different operating conditions using this method. This novel method is based on a vector network analyzer (VNA) and signal generator (SG). Compared with the conventional method of only using a spectrum analyzer and SG, the VNA can remove the system error through a calibration algorithm to ensure the accuracy of the IM3 product measurement results. The measurement results, for the first time, demonstrated the nonlinearity and memory effects of mixers in different amplitude regions of a large carrier signal. These findings are advantageous and can facilitate further research to simplify the digital pre-distortion model of mixers under different operating conditions.

A novel bidirectional RoF link with compensated SBS and RB for 16-QAM OFDM based mm-wave downlink and uplink vector signal generation and transmission on a single fiber

A novel bidirectional RoF link with compensated SBS and RB for 60 GHz OFDM-based 16-QAM downlink and uplink vector signal generation and co-propagation over a single fiber is proposed. At the central station (CS), 60 GHz optical mm-wave is generated and modulated in the optical single-sideband modulation (OSSB) technique by the 16-QAM OFDM downlink vector signal. At the base station (BS), the 60 GHz downlink signal is detected by a high-speed photodetector (PD). The 60 GHz electrical mm-wave signal is transmitted to the user end by an antenna. The uplink carrier is extracted from the unmodulated sideband of the mm-wave downlink vector signal. This reduces the complexity of BS and makes it free from the laser source. The 16-QAM OFDM-based mm-wave uplink signal is received from the user end through an antenna and down-converted to a 10 GHz uplink vector signal. The uplink signal modulates the extracted blank carrier in the OSSB technique. The uplink and downlink vector signals are co-propagated through the standard single bidirectional fiber. Although the carrier reuse over a single fiber reduces the fiber capacity by half, it generates non-linear backscattering such as Rayleigh Backscattering (RB) and Stimulated Brillouin Scattering (SBS). A theoretical analysis is made on the backscattered power and its effect on the fiber transmission. The compensation of SBS by maintaining the SBS threshold and mitigation of RB is carried out by appropriate modulation technique. In addition, downlink and uplink signal with different data rate is transmitted through the compensated bidirectional RoF link, and the transmission performance is analyzed. Based on the analysis, the theoretical model for simultaneous downlink and uplink signal transmission over a single fiber is proposed and verified by the software simulation. The compensated bidirectional RoF link shows up a better performance up to 75 km with negligible power penalty.

QAM Vector mm-Wave Signal Generation Based on Optical Orthogonal Polarization SSB Scheme By a Single Modulator

Millimeter-wave (mm-wave) has become an attractive technique in the fifth generation (5G) because it meets the demand of explosive increase in data traffic. In this study, we propose and demonstrate the generation of quadrature amplitude modulated (QAM) vector mm-wave signal employing optical orthogonal polarization single sideband (SSB) modulation, which employs a single polarization-division multiplexing MachZehnder modulator (PDM-MZM). Based on our scheme, there is no inter-band crosstalk and inter-polarization signal-signal beat interference (SSBI). In our scheme, the two sub-modulators in PDM-MZM both work within their linear modulation range. After PDM-MZM, the two optical SSB signals are orthogonally polarized. By using an interleaver (IL), the low sideband (LSB) and upper sideband (USB) optical signals in the two polarization directions are extracted respectively. In addition, IL also suppresses the unwanted components of the opposite orthogonally polarized signal. We demonstrate the generation of two independent 28 GHz 12 Gbaud quadrature-phase-shift-keying (QPSK) and 6 Gbaud 16-ary quadrature amplitude modulation (16-QAM) signals. 65 km single-mode fiber (SMF) transmission is achieved with the bit-error-rate (BER) below 20% forward-error-correction (FEC) soft-decision threshold of 2.4 102 without dispersion compensation. We also demonstrate the generation of two independent 28GHz 1 Gbaud 64-QAM signals and transmission SMF over 10-km with the BER below 20% FEC soft-decision threshold of 2.4 102. Since the LSB and USB signals are on opposite polarization sides, the inter-band crosstalk and the inter-polarization SSBI can be significantly reduced. Because SSB modulation scheme is deployed, our proposed QAM vector signal generation system is robust to fiber dispersion.

A Performance Evaluation Framework for Direction Finding Using BLE AoA/AoD Receivers

Bluetooth low energy (BLE) has been significantly contributed to the Internet of Things applications due to its advantages, such as low power consumption and scalability. To further expand its applications, BLE has adopted the Angle of Arrival (AoA) and the angle of departure (AoD) to improve the accuracy in direction finding (DF). The AoA/AoD is calculated using the phase difference (PD) between slots in the received BLE data. The PD performance of BLE receiver (RX) in all directions should be evaluated in detail because it directly determines the accuracy of AoA/AoD. In the traditional test method, the reference PD is converted by an antenna array with switches, which is inaccurate due to the conversion errors and path mismatches. Moreover, because of the mechanical rotation of the turntable, the test processing is very time consuming. This article proposes a BLE test waveform generation method that directly includes the reference PD. A commonly used vector signal generator (VSG) is the only required instrument in the evaluation. The compact test setup not only eliminates the requirement of antenna array, switch, turntable, and anechoic chamber but also eliminates the measurement errors caused by these devices. After creating and downloading all BLE test waveforms with reference PD in the range of −180° to 180° by user-defined steps, the PD performance of BLE RX can be quickly evaluated by switching the test waveforms using commands or running them in the sequence mode. Furthermore, three enhanced test cases with automatic test procedures are proposed to evaluate the detailed PD accuracy of BLE RX under the low signal-to-noise ratio (SNR), carrier frequency offset, and modulation frequency deviation environments. Experimental results show that the PD error of the proposed method is 0.19°, and it needs 360 ms to evaluate the PD accuracy of CC2640R2F in all directions in 1° steps.

W-band Millimeter-Wave Signal Generation Based on Frequency Quadrupling and Nonlinearities Tolerant Modulation

In this article, we present a W-band (3, 1) millimeter-wave vector signal generation based on frequency-quadrupled modulation and nonlinearities tolerant modulation by one Mach–Zehnder modulator (MZM). Despite the phase changes, the constellation and sequence of the received (3, 1) signal is consistent with the original regular signal after the detection of the photo-detector (PD). The obtained (3, 1) constellation has better performance compared to pre-coded quadrature phase shift keying (QPSK) constellation at the receiver end, and effectively reduces system complexity and cost. The frequency-quadrupled scheme is experimentally completed with different date rates at 2 and 4-Gbaud. The bit-error-ratios (BERs) results show that the BER performance of (3, 1) signal is superior to the pre-coded QPSK, and it is below the 7% hard-decision forward-error-correction (HD-FEC) threshold of 3.8 × 10−3 over 5 and 10 km single-mode-fiber (SMF) transmission , which demonstrates that the generation of (3, 1) vector mm-wave signal based on proposed frequency-quadrupled scheme and nonlinearities tolerant modulation can be used in our system.

Generation of (3, 1) Vector Signal Based on Probabilistic Shaping Technology without Precoding

In this paper, we introduce the probabilistic shaping (PS) technique to the normal (3, 1) vector signal and simulate the generated PS (3, 1) photonic vector signal on an optical transmission system. The PS (3, 1) photonic vector signal is generated by a radio frequency (RF) signal at 12 GHz driving a Mach–Zehnder modulator- (MZM-) based optical carrier suppression (OCS) doubling, and the PS (3, 1) photonic vector signal is not precoding. The PS (3, 1) photonic vector signal and the normal (3, 1) photonic vector signal are used to transmit in 5 km, 10 km, and 20 km single-mode fibers (SMF), respectively. The simulation results demonstrate that the bit error ratio (BER) of the PS (3, 1) vector signal is less than the forward error correction (FEC) threshold of 3.8 × 10−3, and the BER performance is better than that of the normal (3, 1) vector signal at 4 Gbit/s and 8 Gbit/s transmission rates.

Fractional frequency reuse based frequency allocation for 5G HetNet using master–slave algorithm

Frequency allocation in small cell-based green heterogeneous mobile networks is a demanding research domain nowadays. Femtocells are the essential components of small cell networks. In this paper, we propose a low power micro-femtocell network using the master–slave algorithm. In the master–slave algorithm, the master node allocates work to the slave nodes. When a slave ends its task given by a master node, it informs the master node, and it is being assigned a new workload. Slave nodes do not communicate with each other. In our approach, the microcell is divided into three sectors, and each sector is further categorized into three regions: inner region, outer region, and most-outer region. Femtocells are allocated in these three regions. According to the duty cycle, several femtocells are chosen as master femtocells. The rest of the femtocells are assigned under the supervision of the master femtocells. These femtocells are referred to as slave femtocells. The master femtocells communicate with the microcell, and the slave femtocells communicate with the corresponding master femtocell. Frequency allocation for this micro-femtocell network is proposed based on Fractional Frequency Reuse (FFR). The power consumption, signal-to-interference-plus-noise ratio (SINR), and spectral efficiency for the proposed network are calculated. The simulation results exemplify that the proposed scheme reduces the power consumption of the network by approximately 44%–80% than the conventional heterogeneous network. The simulation results also demonstrate that the proposed network has better SINR and spectral efficiency than the existing micro-femtocell network. For experimental analysis, vector signal generator (VSG) and vector signal analyzer (VSA) are used. The experimental results also show that the proposed network is greener compared to the existing micro-femtocell network.

A scheme to generate 16QAM-OFDM vector mm-wave signal based on a single MZM without optical filter and precoding

In this paper, a novel and relatively simple scheme for generation of high-quality 16QAM-modulated multi-carrier vector millimeter-wave (mm-wave) was proposed, which was only based on a single Mach–Zehnder modulator (MZM), while the precoding technique and optical filter were not needed. At the transmitter, electrical dual single sideband (SSB) signals were generated by a digital signal processing (DSP) module, in which the frequency of modulated signals could be adjusted flexibly. Employing the generated dual-SSB signal to drive a push–pull MZM biased at Quad point, optical dual-SSB 16-QAM OFDM signals were obtained. After a photodiode, higher frequency OFDM vector mm-wave signals were achieved by beating. Based on the proposed method, a simulation platform of generating 30 GHz 16QAM OFDM vector mm-wave signals was set up and the performance of the generated OFDM vector mm-wave was analyzed. The results show that the bit-error ratio of the transmission system were less than hard decision forward-error correction threshold of 3.8×10−3, which demonstrates that the generation of OFDM vector signal can work well.

D-Band mm-Wave SSB Vector Signal Generation Based on Cascaded Intensity Modulators

We proposed and experimentally demonstrated a novel and simple method to realize D-band millimeter-wave (mm-wave) single-sideband (SSB) vector signal generation using cascaded one single-drive Mach-Zehnder modulator (MZM) and one push-pull MZM. After the first MZM driven by a radio frequency (RF) signal of 20-GHz, an optical frequency comb (OFC) with six flat carriers was successfully generated. Using the subsequent push-pull MZM driven by 10-GHz SSB vector signals and a photodiode (PD) for detection, we finally generated D-band SSB vector mm-wave signals at frequencies of 130-GHz and 150-GHz, respectively. The experimental results are well consistent with theoretical and simulation analysis. Based on the proposed scheme, 4-Gbaud generated D-band quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) mm-wave signals were transmitted over 10-km/25-km single-mode-fiber (SMF) and 1-m wireless links. The bit-error-rate (BER) performance can reach less than 7% hard-decision forward-error-correction (FEC) threshold of 3.8 × 10−3.

D-band vector signal generation based on OCS and SSB without an optical filter

A novel D-band vector signal generation and transmission scheme by using joint optical carrier suppression (OCS) and single sideband (SSB) modulation without a narrowband optical filter to remove the undesired optical sidebands is proposed and implemented. An intensity modulator operating on OCS mode is utilized to generate two carrier signals with a frequency spacing of 165.6-GHz. A lower sideband modulated RF vector signal at 20-GHz is used to modulate the push–pull modulator which working on OCS mode. Finally, two electrical millimeter vector signals with frequency 145.6-GHz and 185.6-GHz were generated by heterodyne beating on a photodetector. We experimentally demonstrated 2-Gbaud 16QAM, 4-Gbaud QPSK, and 10-Gbaud QPSK vector signals generation and transmission over 20 km standard single mode fiber and 1 m wireless link, respectively.

Generation of (3, 1) vector signals based on optical carrier suppression without pre-coding.

We experimentally and numerically demonstrated the generation of a (3, 1) vector signal by a single Mach-Zehnder modulator (MZM) without pre-coding. The MZM is driven by the (3, 1) modulated signal after photoelectric conversion by the "square law" of a photodetector. Although the phase changes, the corresponding constellation distribution is consistent with that of the regular signal. Our proposed scheme effectively avoids the pre-coding process with a simple architecture. The bit-error-ratio (BER) results indicate that the (3, 1) signal has a better BER performance than the pre-coded quadrature phase shift keying vector signal, and both are below ${3.8}\times {{10}^{ - 3}}$3.8×10-3 after 25 km optical fiber transmission.

Design of a Portable Orthogonal Surface Acoustic Wave Sensor System for Simultaneous Sensing and Removal of Nonspecifically Bound Proteins.

One challenge for current surface acoustic wave (SAW) biosensors is reducing nonspecific adsorption. A device propagating Rayleigh and shear horizontal surface acoustic waves in orthogonal directions fabricated in ST quartz has the capability of achieving simultaneous detection and nonspecific binding (NSB) protein removal. Current measurement methods for a SAW sensor system based on this device require large-size and expensive equipment such as a vector network analyzer (VNA), signal generator, and frequency counter, which are not suitable for portable, especially point-of-care, applications. In this work, a portable platform based on a direct digital synthesizer (DDS) is investigated for the orthogonal SAW sensor, integrating signal synthesis, gain control, phase/amplitude measurement, and data processing in a small, portable electronic system. This prototype was verified for both stability and repeatability, and the results matched very well with VNA measurements. Finally, system performance in real-time sensing and NSB removal was evaluated.

392 GHz THz vector signal generation based on ISB and multi-frequency signal generation using cascaded phase modulator and I/Q modulator

We propose a novel scheme to generate THz signal based on cascaded phase modulator and I/Q modulator. We experimentally demonstrate 392-GHz THz vector signal generation based on this scheme. Our scheme has these advantages such as dispersion-immunity, good flexibility in frequency and modulation. In our experiment, we realized the THz fiber-wireless link at 392-GHz transmitting 18.4-Gbaud QPSK signal or 4-Gbaud 16QAM signal with BER less than 2.0×10−2, the third generation FEC threshold.

Carrier-frequency-doubled photonic microwave vector signal generation based on PDM-MZM

A simple method based on an integrated polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM) to produce a carrier-frequency-doubled vector signal is presented and experimentally demonstrated. In this structure, the upper sub-MZM is driven by I/Q signals and biased at the quadrature point to modulate a baseband vector signal on the optical carrier. The lower sub-MZM is driven by a LO signal and is biased at the maximum transmission point (MATP) to generate the optical carrier and second-order sidebands. By filtering the negative second-order sideband via an optical bandpass filter (OBPF) and suppressing the optical carrier via polarization controller (PC), a carrier-frequency-doubled vector signal is generated at the photodetector. Due to the adoption of LO frequency-doubled technique, the system’s requirement of a high-frequency LO is relaxed. In a proof-of-concept experiment, 300 MSym/s QPSK signal with a carrier frequency of 16 GHz is obtained by 8 GHz LO signal. Besides, 25-km fiber transmission of the generated QPSK signal is demonstrated. When the optical power obtained after fiber transmission is higher than -4 dBm, the BER after demodulation is less than 8×10−10. Moreover, generation of vector signal with other formats is verified.

On features of implementation of SEFDM-transmitter with optimal shape of envelope

This article describes joint use of two improving spectral efficiency algorithms for multi-frequency signals: SEFDM (Spectrally Efficient Frequency Division Multiplexing) technology and smoothed envelopes. SEFDM-signals are generated with IFFT algorithm. Transmitter with different envelope shapes is realized on SDR-platform HackRF One. Waveforms, spectra and PAPR (peak-to-average power ratio) of SEFDM-signals were obtained from simulation, vector signal generator and SDR-platform.

Analysis and Compensation of Nonidealities in Frequency Multiplier-Based High-Frequency Vector Signal Generators

This paper expounds on the application of frequency multipliers for the frequency upconversion of amplitude- and vector-modulated signals to high frequencies. First, a complex baseband equivalent Volterra series behavioral model is derived for representing the envelope transformation of frequency multipliers. Based on this model, a low-complexity baseband digital predistortion (DPD) scheme is developed to mitigate unwanted distortions exhibited by the frequency multipliers. The proposed DPD scheme consists of three modules: 1) a polynomial predistorter (PD) is first employed to mitigate the memoryless (ML) distortions associated with the frequency conversion; 2) a $D$ th order root module is included to correct for the phase modulation (PM)–PM distortions exhibited by the frequency multiplier with a frequency multiplication factor of $D$ ; and 3) a pruned Volterra-based PD is added to correct for residual distortions attributed to the output stage. As a proof of concept using a low-complexity experimental setup, the proposed DPD scheme is used to linearize several frequency multipliers, namely, a frequency doubler with an output at 12.5 GHz, a frequency quadrupler to produce an output at 25 GHz, and a frequency tripler with an output at 63 GHz. The proposed DPD scheme showed excellent capacity to linearize these frequency multipliers when driven by orthogonal frequency division multiplexing signals with modulation bandwidths up to 400 MHz with less than 56 coefficients.