Local Oscillator Modulation Research Articles

High Repetition Frequency Long-Distance Pulsed Laser Coherent Ranging Based on Local Oscillator Modulation

High Repetition Frequency Long-Distance Pulsed Laser Coherent Ranging Based on Local Oscillator Modulation

A phase-locked loop with a jitter of 50 fs for astronomy applications

AbstractRadio telescopes are among the applications with the highest demands on a local oscillator (LO), which is used to receive and process the signals coming from the sky. Therefore the modules providing the required LO signal have traditionally been big and complicated. To overcome this disadvantage, we implement our own integrated frequency synthesizer inside a small LO module in this article. With this synthesizer we are able to achieve a jitter of only 50 fs integrated from 10 Hz to 2.5 GHz offset at a carrier frequency of 75 GHz. This is in part achieved by a very low in-band phase noise of −111.8 dBc at 10 kHz offset. The stabilizable frequency range is 62–88 GHz. Thus achieving promising results to fulfill this very demanding task with integrated frequency synthesizers in the future.

A reconfigurable wireless superheterodyne receiver for multi-standard communication systems

ABSTRACT The rapid growth of the communication frequency band leads to the diversity of receiving frequency bands of smart devices. This paper proposes a reconfigurable wireless superheterodyne receiver for multi-standard communication systems. The receiver is designed through architecture design, chip selection, layout drawing, and physical measurement. The designed receiver consists of receiving module, local oscillator module, and control module. Unlike previous receivers, the proposed receiver selects the frequency channel, local oscillator frequency, and link gain through the control module in the current scene. The control module consists of a single-chip microcomputer and computer. The receiver can work in application scenarios including 2.4–2.5 GHz, 3.3–3.6 GHz, and 4.8–6.0 GHz. This paper discusses the design process of the proposed reconfigurable receiver in detail. Compared with the traditional receiver, the proposed receiver can change its working mode by software and has the characteristics of flexible reconfiguration. In addition, it has the advantages of a large link gain range and good demodulation performance. Moreover, the receiver is low in design cost and easy to manufacture. Therefore, it can be widely used in receiving modules of WLAN and 5G communication systems.

An improved local oscillator modulation of modulated sampling scheme for multiple mono-pulse radar signals reconstruction

The modulated sampling scheme can intercept noncooperative signals distributed in a wide frequency band by using a single receiving channel, which is an efficient architecture in many radar and communication applications. The modulated sampling scheme employs a non-uniform sample pulse train to fold the intercepted signal prior to quantization/digitization by using a local oscillator (LO) that contains a certain modulation type. Since the mono-pulse radar signals are widely used in many radar systems, the modulated sampling scheme will receive the multiple mono-pulse radar signals simultaneously in dense signal environment, and the folded outputs of the modulated sampling scheme may meet frequency aliasing. Thus, it is necessary to investigate the reconstruction of the multiple mono-pulse signals intercepted by the modulated sampling scheme in the frequency aliasing situation. In this paper, based on the orthogonal matching pursuit algorithm, the LO modulation type of the modulated sampling scheme is analyzed to achieve a better reconstruction performance of the multiple mono-pulse signals. The drawback of the typical LO using sinusoidal frequency modulation to reconstruct multiple mono-pulse signals is investigated firstly. Then, an improved LO using periodic linear frequency modulation is proposed, and its effectiveness to reconstruct multiple mono-pulse signals is analyzed. Furthermore, the parameter setting criterion of the improved LO modulation is given, and the comparison using other modulation types is discussed. Finally, several simulations are conducted to prove our analysis and the improved LO modulation can reconstruct multiple mono-pulse signals under the frequency aliasing condition.

A Flexible Down-Converter for Satellite Communication in the Ka-Band

Abstract Conventional communications satellites operate with fixed frequency, polarisation and coverage plans that are drawn up years before their launch during the payload definition phase. The satellite will typically be designed for a lifetime of more than fifteen years. During this operating period, changes in bandwidth requirements and the distribution of the service across its geographic coverage are more than likely. A new generation of communication satellites is expected to respond flexibly to these regional and temporal fluctuations in demand. The concept of cellular division of the coverage area and the coverage of these cells with spot beams in connection with the reuse of frequency bands enables this flexibility. The satellite's frequency plan has to be redefined throughout the mission lifetime via commands from the ground. The Flexible Down-Converter DOCON is one of the new components that allow satellite signals to be redistributed between service areas to flexibly reallocate the most critical spectrum resources as needed. DOCON is a flexible Ka-band down-converter from RF = 27.5 ... 30.0 GHz to IF = 17.7 ... 20.2 GHz designed for GEO communication satellites. The device includes the housing, DC-, RF-, and telemetry / tele-command interfaces. An Engineering Model (EM) in form, fit and function was successfully built and tested. The next stage, the Engineering Qualification Model (EQM), is currently in fabrication and will be qualified until end of 2019. The modular concept comprises hermetically sealed LTCC microwave modules as key building blocks. There are three of these LTCC-modules: the Local Oscillator Module (LOM), the Mixer Module (MXM), and the Variable Gain Module (VGM). Their function and realization shall be discussed in this paper.

A parameter estimation algorithm for LFM/BPSK hybrid modulated signal intercepted by Nyquist folding receiver.

Nyquist folding receiver (NYFR) is a novel ultra-wideband receiver architecture which can realize wideband receiving with a small amount of equipment. Linear frequency modulated/binary phase shift keying (LFM/BPSK) hybrid modulated signal is a novel kind of low probability interception signal with wide bandwidth. The NYFR is an effective architecture to intercept the LFM/BPSK signal and the LFM/BPSK signal intercepted by the NYFR will add the local oscillator modulation. A parameter estimation algorithm for the NYFR output signal is proposed. According to the NYFR prior information, the chirp singular value ratio spectrum is proposed to estimate the chirp rate. Then, based on the output self-characteristic, matching component function is designed to estimate Nyquist zone (NZ) index. Finally, matching code and subspace method are employed to estimate the phase change points and code length. Compared with the existing methods, the proposed algorithm has a better performance. It also has no need to construct a multi-channel structure, which means the computational complexity for the NZ index estimation is small. The simulation results demonstrate the efficacy of the proposed algorithm.

High Conversion Efficiency Photonic Microwave Mixer With Image Rejection Capability

A new photonic microwave image rejection mixer that can achieve high conversion efficiency and has a wide bandwidth is presented. It is based on an integrated dual-parallel Mach–Zehnder modulator (MZM) with a 90° polarization rotator on one branch of the modulator. The two modulators connected in parallel are biased at the minimum transmission point to generate two sets of orthogonally polarized radio frequency (RF) and local oscillator (LO) modulation sidebands with the optical carrier being suppressed. Suppressing the optical carrier enables high RF and LO modulation sidebands to be detected by a photodiode without saturation. The LO modulation index is also designed to obtain a high conversion efficiency mixing operation. Experimental results demonstrate frequency downconversion with an image rejection function and a high conversion efficiency of > $-$ 5 dB over a wide 3 to 20 GHz frequency range. A technique for compensating the effect of coupler amplitude and phase imbalance to obtain a high image rejection ratio is also experimentally demonstrated.

디지털 고주파 메모리 구현에 관한 연구

Digital Radio Frequency Memory, ( as DRFM ), is a device with the ability to restore output to the input RF signal in the required time after storing the incoming RF signals. Therefore DRFM is widely used in Jammer, EW Simulator, Target Echo Generator, and so on. This paper proposes its hardware implementation composed with the high frequency part and the digital processing part consisting of RF input/output module and local oscillator module. It is also proposed the replicated signal generation method which is consisted of the Analog-Digital conversion in the form of pulsed RF signal quantization, and FPGA to save and produce the playback signal, and RF signals to produce a Digital-Analog Conversion in the digital processing unit. This proposed scheme applied to test board and confirmed the validity of the proposed scheme through the test results obtained by the simulated input signals.

Frequency Quadrupler for Millimeter-Wave Multiband OFDM Ultrawideband Wireless Signals and Distribution Over Fiber Systems

Performance of millimeter-wave (mm-wave) multiband orthogonal frequency division multiplexing (MB-OFDM) ultrawideband (UWB) signal generation using a frequency-quadrupling technique and transmission over fiber is investigated by simulation and experiment, and the error vector magnitude (EVM) is used to evaluate the transmission quality. Frequency hopping within the first three bands of IEEE 802.15.3a has been used in experiments to obtain an MB-OFDM UWB signal. The frequency quadrupling can be achieved by using only one Mach–Zehnder modulator (MZM) and two cascaded MZMs. It is found that using one MZM is better than using two cascaded MZMs in the performance of mm-wave generation. For using one MZM, it is found that transmission through 20 km of fiber degrades the EVM by less than 0.5 dB compared with back-to-back. Also, the EVM is degraded by less than 1 and 0.25 dB for a bias drift of less than 20% and an extinction ratio of more than 10 dB, respectively. Moreover, the EVM of the system using one MZM is improved by more than 2.5 dB compared with the two cascaded MZMs. In addition, it is found that the minimum EVM required of −17 dB can be achieved by using a local oscillator modulation index of ∼63% and 70% at least for using the one MZM and two cascaded MZMs, respectively.

A periodic nonlinear analysis technique for microwave mixers

AbstractA general, iterative method is described for obtaining voltage and current waveforms in a periodically driven nonlinear active circuit. This allows local oscillator modulation of the parameters of device models to be studied. The technique is applicable to both diode and FET circuit models, since it can accommodate multiple nonlinearities.