Frequency Measurement Technique Research Articles

A Photonic Technique for Instantaneous Microwave Frequency Measurement Utilizing a Phase Modulator

We propose a simple microwave frequency measurement approach utilizing a phase modulator. After properly adjusting the polarization controllers in the proposed system, two dispersion-induced power penalty functions with different variation trends are obtained. A distinct relationship between the power ratio and the microwave frequency can be constructed by comparing the two power penalty functions. Thus, the microwave frequency can be determined by the power ratio value. Since only a bias drift free phase modulator and a single laser source are needed, the measurement system is significantly simplified. In the experiment, a frequency measurement over the range of 1.6–24.6 GHz with measurement errors within ±0.3 GHz is achieved.

Using nanogap in label-free impedance based electrical biosensors to overcome electrical double layer effect

Point-of-care biosensor applications require low-cost and low-power solutions. They offer being easily accessible at home site. They are usable without any complex sample handling or any kind of special expertise. Impedance spectroscopy has been utilized for point-of-care biosensor applications; however, electrical double layer formed due to ions in the solution of interest has been a challenge, due to shielding of the electric field used for sensing the target molecules. Here in this study, we demonstrate a nanogap based biosensor structure with a relatively low frequency (1---100 kHz) measurement technique, which not only eliminates the undesired shielding effect of electrical double layer but also helps in minimizing the measurement volume and enabling low concentration (µ molar level) detection of target molecules (streptavidin). Repeatability and sensitivity tests proved stable and reliable operation of the sensors. These biosensors might offer attributes such as low-cost label-free detection, fast measurement and monolithic chip integrability.

Radial period extraction method employing frequency measurement for quantitative collimation testing

A radial period extraction method employing frequency measurement is proposed for quantitative collimation testing using spiral gratings. The radial period of the difference-frequency fringe is treated as a measure of the collimation condition. A frequency measurement technique based on wavelet transform and a statistical approach is presented to extract the radial period directly from the amplitude-transmittance spiral fringe. A basic constraint to set the parameters of the wavelet is introduced. Strict mathematical demonstration is given. The method outperforms methods employing phase measurement in terms of precision, stability and noise immune ability.

Frequency Domain Sensors and Frequency Measurement Techniques

Getting fast and accurate information is of paramount importance for most monitoring, data acquisition, and monitoring systems; there are sensors that transform their input into a frequency domain output, this kind of sensors are known as Frequency Domain Sensors (FDS); when the value of the output frequency is measured in a FDS, the value of the sensor’s input (measurand) can be calculated, that is why the frequency measurement in the output of FDS is critical for using such sensors. In this work different kinds of resonant sensors (FDS) are reviewed; also frequency measurement techniques are explored; finally a novel frequency measurement method is proposed and analyzed for resolution improvement in frequency domain sensors.

Mathematical Modelling of molecular adsorption in zeolite coated frequency domain sensors

Fast and accurate information is important for most monitoring, data acquisition, and monitoring systems; sensors are transducers that allow to accomplish such task. In this work different kinds of resonant sensors known as frequency domain sensors are reviewed; also frequency measurement techniques are explored; finally resolution improvement is proposed and analyzed for using frequency domain sensors by mathematical modelling.

On-Wafer Calibration Technique for High Frequency Measurement with Simultaneous Voltage and Current Tuning

This paper presents a novel on wafer calibration method for the measurement of radio RF passive components with R&S vector network analyzer (VNA) at RF and mm-wave frequency. This method has employed the high frequency structure simulator (HFSS) results along with multi-level optimizations to get the nominal values used for on wafer calibration. Multiline (Thru-reflect-line) TRL calibration standards fabricated on the same substrate are used with better accuracy. Measured results show that a thru line provides less than 0.015 dB insertion loss throughout the frequency range of 1GHz-67GHz. This result is much better compared to the results achieved by conventional Short-open-load-thru (SOLT) calibration and (Thru-reflect-line) TRL calibration using the available calibration substrates. Using this calibration technique, the phase variation of the thru line shows less than 3° at 67GHz which is much lower than 15° achieved by the conventional calibration methods. The measurement of the multi band characteristics of the RF passive components by simultaneous current and voltage application has also been demonstrated successfully.

Instantaneous microwave frequency measurement based on hybrid microwave photonic filter

A novel photonic technique for instantaneous microwave frequency measurement based on hybrid microwave photonic filter (HMPF) is proposed and experimentally demonstrated. The HMPF is composed of an all-pass filter and a band-pass filter with negative coefficients. By properly controlling the power relationship between the all-pass filter and the band-pass filter, the HMPF can realize a monotonic frequency response, and then a unique relationship between the output power and the input frequency is established. A high measurement resolution can be achieved for a given frequency range.

High frequency measurement techniques for vias in printed circuit boards

This article provides an overview of some multiport measurement techniques for dense via arrays, which play an important role in high-speed links as package and connector footprints in multilayer printed circuit boards. Advantages, challenges, and limitations of three approaches for high-frequency measurements up to 50 GHz are discussed: launches with fan-out traces and on-board coaxial connectors, double-sided direct surface probing with RF microprobes, and recessed probe launches with extension traces and microprobes. The measurement results obtained by the presented measurement techniques are then compared to simulation results computed using full-wave and physics-based via models. Finally, the multiport probing approach with interposers is addressed through a case study of simultaneous access for up to 12 vias in a 1 mm pitch via array that can be applied for measurements in the frequency range up to 10 – 15 GHz.

Ultrahigh-Resolution Photonic-Assisted Microwave Frequency Identification Based on Temporal Channelization

Real-time ultrahigh-resolution microwave frequency identification is paramount for widespread applications, such as communications, radar, and electronic warfare. Photonics-assisted microwave frequency identification can be achieved using an optical channelizer. While this technique enables simultaneous measurement of multiple frequencies, it has poor measurement resolution due to the large channel spacing, which is usually greater than 1 GHz. Here, we introduce a new channelizer-based microwave frequency measurement technique that offers nearly 500 times higher spectral resolution. This method employs largely dispersed broadband optical pulses to encode the time-domain characteristics of the modulating signal to the optical spectral domain. An optical channelizer is employed to slice the spectrum, which is equivalent to performing temporal sampling of the time-domain waveform. The unknown microwave signal is then reconstructed and its spectral distribution is analyzed by a digital processor. To evaluate the proposed technique, frequency measurements of a single-tone, a multiple-tone, and a frequency-hopping microwave signal are demonstrated. A measurement resolution as high as 55 MHz is achieved using an optical channelizer with a channel spacing of 25 GHz.

The optimization of super-high resolution frequency measurement techniques based on phase quantization regularities between any frequencies

Step phase quantization regularity between different nominal frequency signals is introduced in this paper. Based on this regularity, an optimized high resolution frequency measurement technique is presented. The key features and issues of phase quantization characteristics and measurements are described. Based on the relationship between the same or multiple nominal signals with a certain differences, the resolution of frequency measurements is developed and the range is widened. Several measurement results are provided to support the concepts with experimental evidence. The resolution of frequency measurement can reach 10(-12) (s(-1)) over a wide range or higher for specific frequency signals.

Remote Wideband Microwave Frequency Measurement Based on a Single-Passband Microwave Photonic Filter

A new method for remote wideband microwave frequency measurement utilizing a single-passband microwave photonic filter is proposed, theoretically analyzed, and experimentally demonstrated. The frequencies of the input microwave signals can be measured by monitoring the maximum output microwave power while scanning the central frequency of the single-passband microwave photonic filter. The parameters of the filter have also been analyzed to optimize the frequency measurement performance. The proposed frequency measurement technique is easy to implement, capable of measuring frequencies of multiple microwave signals.

Method for high resolution and wideband spectroscopy in the terahertz and far-infrared region

Asynchronous electro-optic sampling (A-EOS) using two mode-locked lasers with slightly different pulse repetition rates has significantly advanced high-speed time-domain terahertz (THz) spectroscopy on several practical fronts. However, A-EOS also holds strong potential as a precision frequency measurement technique. By carefully considering A-EOS in the frequency domain as a pair of femtosecond frequency combs with a detuned comb spacing, we show there exists a unique one-to-one mapping between a THz frequency comb and the resulting radio frequency comb of the A-EOS signal. With reasonable frequency comb spacing (0.1 to 1 GHz) and detuning frequencies (1 to 50 kHz) of the combs’ repetition rates, interrogation bandwidths of >10  THz centered between 10 to 100 THz (300 to 3000  cm−1) are possible. Furthermore, we calculate the effect of nonuniform spectral phase of the sampling pulse train and wave-vector mismatch within a ZnTe sampling crystal on the expected heterodyne beat signal.

Brillouin-assisted microwave frequency measurement with adjustable measurement range and resolution

We present a reconfigurable microwave frequency measurement technique with adjustable measurement range and resolution. The key novelty of the technique is the employment of stimulated Brillouin scattering, which results in a tunable amplitude comparison function, leading to an adjustable measurement range and resolution. The proposed technique is switchable between a wideband tunable narrow measurement range (~2 GHz) with high resolution (±0.05 GHz) and a fixed wide measurement range (12 GHz) with moderate resolution (±0.25 GHz).

High accuracy microwave frequency measurement based on single-drive dual-parallel Mach-Zehnder modulator

A novel approach for broadband microwave frequency measurement by employing a single-drive dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. Based on bias manipulations of the modulator, conventional frequency-to-power mapping technique is developed by performing a two-stage frequency measurement cooperating with digital signal processing. In the experiment, 10 GHz measurement range is guaranteed and the average uncertainty of estimated microwave frequency is 5.4 MHz, which verifies the measurement accuracy is significantly improved by achieving an unprecedented 10(-3) relative error. This high accuracy frequency measurement technique is a promising candidate for high-speed electronic warfare and defense applications.

Instantaneous microwave frequency measurement using optical carrier suppression based DC power monitoring

A novel photonic-assisted technique for instantaneous microwave frequency measurement is proposed using two cascaded Mach-Zehnder modulators (MZMs) biased at the transmission null point. Then, the microwave frequency can be estimated by monitoring direct current (DC) optical power. Moreover, the measurement range and the measurement resolution can be optimized by setting the time delay between optical and electrical link and optical dispersion, respectively. The approach is theoretically investigated and experimentally verified with a measurement range of 8 GHz and a measurement error of less than ± 0.15 GHz.

Photonic instantaneous microwave frequency measurement based on two different phase modulation to intensity modulation conversions

A novel photonic technique for instantaneous frequency measurement of microwave signal based on phase modulation to intensity modulation conversion is proposed and demonstrated. In the proposed system, an optical carrier is modulated by a microwave signal with its frequency to be measured through a phase modulator. The phase-modulated optical signal is then converted to intensity-modulated signals in two independent paths using a dispersive media and a frequency discriminator respectively. Since the dependence of the received microwave power on the input microwave frequency in the two paths differs, the microwave power ratio between the two paths can be used to uniquely determine the microwave frequency. The major advantages of the approach lie in that only one laser source and the bias-free phase modulator is employed in the system, which improves the stability of the system. Experimental demonstrations of the frequency measurement based on the proposed approach are presented.

A new time‐domain based power system frequency estimation algorithm

SUMMARYFrequency stability is one of the most important features of power systems. It is closely dependent on the value of system frequency. In the present day modern power systems, fast and accurate frequency estimation has become quite vital. Any mistake in accurate estimation of frequency may threaten the frequency stability or at least lead to system operation problems. In this paper, a new time‐domain based power system frequency estimation algorithm is proposed. Different abnormal events such as frequency decline due to load‐generation mismatch are modeled and ability of the new frequency measurement technique to track the frequency is tested. Performance of the new method is evaluated and compared with an existing frequency estimation algorithm. Simulation results confirm advantages of the new approach over the existing method. Copyright © 2011 John Wiley & Sons, Ltd.

Microwave Frequency Measurement Based on Phase Modulation to Intensity Modulation Conversion using Fiber Bragg Grating

A simple photonic technique for instantaneous microwave frequency measurement using an optical phase modulator and a fiber Bragg grating (FBG) is proposed and investigated. The FBG acts as tilt filters to offer different slopes of suppression for the optical carrier and the two sidebands when wavelengths are located at different positions of the FBG. A fixed relationship between the microwave frequencies and microwave powers is established. The microwave frequency can be estimated by measuring the microwave power differences. A measurement resolution of ±0.22 GHz over a 15 GHz measurement bandwidth is achieved. Experiments are performed to verify the effectiveness of the proposed approach.

Instantaneous frequency measurement based on transversal microwave filters with high resolution

We propose a novel photonic technique for microwave frequency measurement based on transversal microwave filters with high resolution. Two parallel microwave filters with sine and cosine frequency responses are obtained by cross gain modulation in a single semiconductor optical amplifier, which introduces two different frequency responses to achieve an amplitude comparison function. We also demonstrate a proof-of-concept experiment. The measurement error is less than +-0.04 GHz for the first band range of 0-3.45 GHz and less than +-0.03 GHz for the second band range of 3.45-5.8 GHz. Our scheme is found to be capable of being extended for larger frequency range measurements using a shorter fiber length.

Instantaneous Microwave Frequency Measurement Using a Photonic Microwave Filter With an Infinite Impulse Response

A photonic technique for instantaneous microwave frequency measurement is proposed. In the proposed technique, a photonic microwave filter having a monotonic frequency response with the magnitude varying from positive infinity to negative infinity on a log scale, is constructed by cascading two photonic microwave filters with one having an infinite impulse response and the other having a finite impulse response. For a single-frequency microwave signal with a normalized magnitude, a unique relationship between the output response and the input frequency is established. Since the response extends from positive to negative infinity, for a given measurement range, a significantly increased measurement resolution is achieved. The proposed technique is verified by an experiment.