Amplitude-only Measurement Research Articles

Large-Scale Phased Array Calibration Based on Amplitude-Only Measurement With the Multiround Grouped-REV Method

Large-Scale Phased Array Calibration Based on Amplitude-Only Measurement With the Multiround Grouped-REV Method

Fast Amplitude-Only Measurement Method for Phased Array Calibration

A novel amplitude-only measurement method is proposed to measure the signals (complex fields) of individual antenna elements for phased array calibration. The proposed method has minimum measuring time among the known amplitude-only measurement methods. The total number of power measurements with this method is about twice the number of antenna elements of phased array. Phase shifters are required to implement only three phase shifts (0°, 90°, and 180°). Array signal power is measured when the phase setting of an antenna element is one of the three phase shifts. According to the superposition principle of electromagnetic field, array signal is a linear combination of antenna element signals. As signal power is the inner product of a complex signal and itself, a set of linear equations concerning the inner products of the antenna element signals are established and solved with the measured data. The element signals are obtained with the inner products analyzed with a set of nonlinear equations. Numerical simulations and experimental results validated the effectiveness of the proposed method in calibrating phased arrays.

Compressed sensing phase retrieval with phase diversity

The compressed sensing (CS) theory shows that sparse signal can be reconstructed accurately with some randomly observed measurements that are much fewer than what traditional method requires. Since it takes structure of signals into consideration, it has many advantages in the structured signals process. With CS, measuring can be speeded up and the cost of hardware can be decreased significantly. However, it faces great challenge in the amplitude-only measurement. In this article, we study the magnitude-only compressed sensing phase retrieval (CSPR) problem, and propose a practical recovery algorithm. In our algorithm, we introduce the powerful Hybrid-Input–Output algorithm with phase diversity to make our algorithm robust and efficient. A relaxed ℓ0 norm constrain is also introduced to help PR find a sparse solution with fewer measurements, which is demonstrated to be essential and effective to CSPR. We finally successfully apply it into complex-valued object recovery in THz imaging. The numerical results show that the proposed algorithm can recover the object pretty well with fewer measurements than what PR traditionally requires.

A Novel Amplitude-Only Measurement Method to Determine Element Fields in Phased Arrays

A novel amplitude-only measurement method is proposed for phased array calibrations. The proposed method can determine a complex element field at every phase shift of a digital phase shifter in phased arrays. The method can be realized using higher order Fourier coefficients of one array-power response measured with the conventional rotating element electric field vector (REV) method. Simulations and experiments were carried out, including transmission errors from the phase shifters, which validated the proposed method. More accurate calibration and beam forming can be achieved by using the precise element fields at all phase shifts determined by the proposed method.

Comments on “A novel vector network analyzer”

The authors comments on the work of Hoffman and Skvor "A Novel Vector Network Analyzer”(1998). It was demonstrated in this paper that only five independent parameters are needed to fully map the complex reflection coefficient of an unknown sample to amplitude-only reflection measurement instead of six parameters as concluded in the above paper.

PERFORMANCE EVALUATION OF PHASE-ANGLE GRADIENT METHOD FOR PHASE RETRIEVAL BASED ON LOW-FREQUENCY AMPLITUDE-ONLY NEAR-FIELD DATA

The Phase Angle Gradient Method (PAGM) is a recent technique developed for phase retrieval based on amplitude-only measurement data. Preliminary results have shown that the PAGM is able to perform phase retrieval at 100MHz with accurate phase information based on measured fIeld components on three planar surfaces. In this paper, a performance evaluation of the PAGM under different conFigurations is conducted. Phase retrieval based on field measurements for different plane sizes and separations between the planes are studied rigorously. In addition, the PAGM is tested for different initial phase distributions. The results show that the PAGM is capable of retrieving phase information even if the separation between the measurement planes is small in terms of wavelengths.

Phase Retrieval for Millimeter- and Submillimeter-Wave Imaging

Phase-retrieval techniques are demonstrated on scattered-field amplitude-only measurements at 186 and 580 GHz. These techniques allow for imaging of a scatterer using a simple amplitude-only measurement system.

Measurement system of complex permittivity of ornamental rocks in L frequency band

The use of ground-penetrating radar (GPR) techniques at high frequencies for historical building investigations requires an accurate knowledge of the material complex permittivity. A new measurement system is presented, which by exploiting a resonance phenomenon, yields accurate values of permittivity and resistivity also in the case of low-loss materials. These parameters are obtained from an amplitude-only measurement of the transmission response curve of a rectangular waveguide cavity, loaded by the sample under test. The setup requires the availability of brick-shaped samples, which can be obtained easily in the case of rock materials. Permittivities and resistivities were measured in the frequency range 1.1-1.7 GHz on samples of marbles, sandstones, and limestones. The measurement method and the experimental results are presented and discussed.

Far-field antenna pattern estimation from near-field data using a low-cost amplitude-only measurement setup

In this paper we report some results on the estimation of the far-field of an antenna by using a low-cost amplitude-only near-field measurement setup. A simple experimental setup is used to measure the intensity of the near-field of the antenna under test on two planes. The measured intensity of the near field is then numerically processed to determine the far-field pattern. The results confirm the validity of the approach.

Phase difference between linear components of elliptically polarized waves from amplitude only measurements

An amplitude-only measurement setup can measure the axial ratio and tilt angle of an elliptically polarized wave. During design, both the amplitude and phase of the linear components are needed. The equipment measures the amplitudes directly. A nomograph, using the well-known relationships between polarization components determines the phase of the vertical component relative to the horizontal. The value of the nomograph goes beyond the stated objective, because it shows the relationships between the variables. The nomograph gives both the requirements for good circularity, and the sensitivity of the various parameters. >

An Amplitude-Only Measurement Technique for the Evaluation of the Complex Permittivity Of Composite Materials in the Microwave Range.

ABSTRACTThe basic transmission line and rectangular waveguide equations, with reference to different loading conditions, are firstly reviewed. Amplitude and phase, amplitudeonly, and phase-only permittivity measurement techniques are briefly discussed. Two very naive graphical and numerical calculation procedures are presented, together with the results of measurements on some composite materials.

Precise Phase Measurements with the Acoustic Microscope

Abstmct-The measurement and the use of phase in acoustic microscopy are discussed. It is demonstrated that in many applications phase can be used to provide sensitivity and information unparalleled by amplitude-only measurement methods. A technique capable of highaccuracy measurement of the phase of short RF acoustic pulses is described. The power of this phase measurement technique is illustrated in a number of applications. Surface material property measurements such as the Rayleigh-wave velocity and the inversion of the complex V(z) to obtain the reflectance function of a liquid-solid interface are considered. Surface topography mapping based on phase measurement is examined. A Fourier transform approach for precision determination of linewidths comparable to the resolution spot size is also presented.