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Abstract The authors deal with the problem of the design and manufacture of a high‐resolution FMCW radar for drone detection and classification. The difficulties of the problem are discrete clutter reduction and spurious phase noise mitigation. The discrete clutter is due to the reflected signals from land vehicles, birds etc., while the spurious phase noise is inherent in the radar signal due to the phase‐locked loop component and leakage between the transmitting and receiving paths. Both spurious phase noise and clutter will increase the system noise level and hence reduce the probability of detection of small targets such as drones and induce false alarms on the radar screen. In order to reduce discrete clutter, the authors propose a method to separate a drone from discrete clutter based on the design of the radar system parameters for a drone and its propeller detection, target's Doppler dispersion and moving characteristics. For spur mitigation, a method that focuses on the design of the isolation coefficient between transmitting and receiving paths to decrease the power of spurs below the minimum power requirement at the input of the analogue‐to‐digital converter is introduced. The results were applied by the authors to the development and manufacture of a radar with the given specifications for drone detection and classification. Different laboratory and field tests show that the spurs are mitigated and the drones are separated from discrete clutter with a range and accuracy better than the one recently published.

Abstract This paper presents a differential complementary metal oxide semiconductor inductor‐capacitor voltage controlled oscillator (LC‐VCO). The VCO is adopted from the gate‐to‐source capacitor feedback Colpitts VCO which has the advantage of large value of negative conductance. Due to the large negative conductance, the VCO has a more reliable startup oscillation at the lower currents. The main characteristics of the VCO such as negative conductance, oscillation frequency and phase noise are discussed and analysed. The value of parameters in this circuit have been determined using Non‐dominated Sorting Genetic Algorithm (NSGA‐II) to have the optimum performance. The designed VCO oscillates at 2.76 GHz under a supply voltage of 1.4 V. Power dissipation of the proposed VCO is 873 μW which is significantly lower than that of some other VCOs. The post‐layout simulation results of the proposed VCO are presented and compared with the performance of some other VCOs.

Abstract Low‐frequency noise, generated inherently by the number or mobility fluctuation of carriers, is a crucial concern for the design of analog and digital circuits. Unified modelling based on experimental validation of near‐DC noise in amplifiers is a long‐standing open problem. This article develops a model for low‐frequency noise by deriving new bounds for carrier capturing and releasing. According to the proposed model, a measurement system is suggested that operates in a wide frequency range and even at very low frequencies. The system is noise‐tolerant, since the amplifier is selected based on acceptable noise levels. Among the advantages are the independence from specialized structural noise models for each component and the low cost of the measurement system. The evaluation results show that the proposed method leads to a promising improvement in the low‐frequency noise measuring and is superior to conventional models in the normalized root mean square error indicator. Findings reveal that the proposed measurement method can estimate the flicker noise around the DC frequency, and the proposed model agrees reasonably with the proposed measurement circuit.

Abstract The ever‐expanding horizon of radar applications demands solutions with high‐end radar functionalities and technologies and is often limited by the available radar equipment, cost and time. A practical method to tackle the situation is to rely on the modelling and simulation of radar systems based on the user requirements. The comprehensive system‐level modelling of a pulsed Doppler radar in MATLAB/Simulink consisting of all the fundamental blocks in the transmit chain, the environment, the receive chain, and the data processing chain is presented in this article. The first half of the article discusses the high‐fidelity simulation of each building block in the radar model. In the second half of the article, the range‐Doppler plot generated from the high‐fidelity radar model is compared and validated using the range‐Doppler plot from a real radar trial. The radar phase noise plays a crucial role in the detection of slowly moving, low radar cross‐section targets in the presence of strong clutter. The article also briefly discusses the effects of radar oscillator phase noise in the range‐Doppler plot. The validated, fully flexible radar model has the advantage of supporting the addition of further building blocks and optimising the parameters based on user requirements.

Abstract Due to their perfect periodic autocorrelation property, Zadoff–Chu sequences are often used as stimulus signals in the measurement of radio channel responses. In this letter, the cross‐correlation of a linear shift‐invariant system's response to a Zadoff–Chu sequence is derived for the case that a multiplicative perturbation such as phase noise is present at its output. The perturbation signal is shown to incur a spurious discrete Fourier transform, thus degrading the correlation's peak to sidelobe ratio. The implications for the performance limits of channel measurement systems are discussed.

Abstract The experimental validation is presented of an optical injection‐locked (OIL) vertical‐cavity surface‐emitting laser (VCSEL)‐based optoelectronic oscillator (VBO) to overcome the direct‐modulation bandwidth limitations of packaged VCSELs. A 1.3 μm VCSEL under OIL is directly modulated at 12 GHz. The carrier phase noise value is −97.7 dBc/Hz at 10 kHz offset. A time domain characterisation of the oscillator based on Allan variance is proposed. The performed measurements showed that the OIL technique allows an increase in the optoelectronic oscillator (OEO) carrier frequency in comparison with free‐running VBOs while maintaining high spectral purity. The results for a 12 GHz delay‐line OEO with amplitude modulation are also compared with the proposed approach.

Abstract This article proposes a tunable active inductor (AI)‐based voltage‐controlled oscillator (VCO) andbandpass filters (BPF) on a single integrated design in 90 nm CMOS process for wireless applications. By exploiting component sharing technique through single pole double throws switching method, a common AI is shared between VCO and BPFs. As the passive inductor is replaced by the AI and shared, silicon area consumption is significantly reduced. Transforming the inductor in tunable mode benefits to eliminate MOS varactors for tuning purposes; one step forward to reduce silicon area consumption. Operating as VCO, its frequency ranges from 1.93 to 6.22 GHz (tuning scope is 105%) for tuning voltage of 0.2 ∼ 1 V. The DC power consumption varies from 1.83 to 3.84 mW, and differential output power is 3.39 to − 2.99 dBm. The phase noise varies from − 81.32 to − 76.89 dBc/Hz, and the figure of merit has a value of − 148.74 dBc/Hz at 5.03 GHz frequency. While acting as BPF, two approaches of center frequency tuning are applied. The voltage tuning yields center frequency of 8.43 ∼ 7.08 GHz along with the maximum gain of 10.29 dB at 7.81 GHz. The capacitive tuning outputs frequency tuning of 7.64 ∼ 7.06 GHz. The BPF consumes DC power of 2.56 to 2.27 mW (voltage tuning) and 2.40 mW (capacitive tuning). The proposed design occupies a layout area of 1215.6 μm2. All the simulations have been performed considering parasitic elements evolved from the extraction of layout. Finally, a quantitative comparison and justification of the proposed design are made with respect to other published works.

It is generally considered that increasing the carrier frequency of radar is an important way to improve the precision of micro-motion measurement. However, the increase of the radar frequency may raise the phase noise intensity of the radar transmitting signal and make the extraction more difficult, therefore it is particularly necessary to study the influence of phase noise on the extraction of micro-motion characteristics. In this study, specific studying about the effect of phase noise on the extraction of micro-Doppler (m-D) features is carried out. The effect of phase noise on the extraction performance of the m-D features is evaluated based on a parameter micro-motion signal-to-clutter ratio and an empirical formula is put forward based on the experiments. The results of simulation experiments indicate that increasing the carrier frequency cannot improve the extraction performance of micro-motion features in the case of using both time–frequency analysis method and the new developed sinusoidal frequency modulation Fourier transform (SFMFT) method. Meanwhile, increasing the frequency of target's micro-motion has an improvement effect through time–frequency method due to the increase of Doppler frequency.

Parasitic capacitances in high frequency have a significant role in examining the inductor-capacitor tank oscillators (LC oscillators) output signal quality. Here, the authors proposed a new idea for Ka-band satellite receiver oscillator, which considers these parasitic elements, in order to maintain a specific precise frequency where there is no need for a broadband frequency range. By using tuned parasitic elements in differential LC oscillator to resonate the circuit's common mode at twice the oscillation frequency, a better phase noise performance and higher oscillator FOM can be achieved. The developed methodology is employed to design and fabricate an oscillator in 0.25 µm AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors process for 19.25 GHz oscillations.

Based on the study of existed least-squares and weighted least-squares phase unwrapping methods, an improved weighted least-squares algorithm based on unwrapping phase error compensation is proposed. First, the conventional weighted least-squares method is used to get the initial result of phase unwrapping. Then the unwrapping result is optimised by iterative compensation of phase unwrapping error. In addition, for the reasonable selection of the times of iteration, an iterative mechanism is designed to avoid the redundant or insufficient compensation caused by too many iterative times and too few. Compared with the traditional weighted least-square method, by using the proposed method, the global influence of phase noise is constrained by weighted processing, and meanwhile, the accuracy of phase unwrapping is greatly improved by iterative error compensation. The simulation results confirm the superiority of the proposed method.

Pseudo-random sequence plays an important role in the field of the phase noise simulation. This study analyses the pseudo-random sequence generated by the method based on cellular automata (CA). Compared with the method of look-up table and linear feedback neighbourhood registers, the simulation results show that the pseudo-random sequence generated by the CA method has better adaptability in the process of phase noise simulation.