Calculation of the Differential Impedance of Tracks on FR4 substrates
There is a discrepancy between calculated and measured values of impedance for differential transmission lineson FR4. This is especially noticeable in the case of surface microstrip configurations. The anomaly is shown tobe due to the nature of the substrate material. This needs to be considered as a layered structure of epoxy resinand glass fibre. Calculations, using Boundary Element field methods, show that the distribution of the electricfield within this layered structure determines the apparent dielectric constant and therefore affects theimpedance. Thus FR4 cannot be considered to be uniform dielectric when calculating differential impedance.
ACPR (adjacent channel power ratio), AltCPR (alternatechannel power ratio), and noise are important performancemetrics for digital communication systems thatuse, for example, WCDMA (wideband code division multipleaccess) modulation. ACPR and AltCPR are bothmeasures of spectral regrowth. The power in the WCDMAcarrier is measured using a 5MHz measurement bandwidth;see Figure 1. In the case of ACPR, the total powerin a 3.84MHz bandwidth centered at 5MHz (the carrierspacing) away from the center of the outermost carrier ismeasured and compared to the carrier power. The resultis expressed in dBc. For AltCPR, the procedure is thesame, except we center the measurement 10MHz awayfrom the center of the outermost carrier.
Rotating shafts experience a an elliptical motion called whirl. It is important to decompose this motion into a forward and backward whil orbits. The current function makes use of two sensors to generate a bi-directional spectrogram. The method can be extended to any time-frequency distribution
％
％ compute the forward/backward Campbell/specgtrogram
％
％ INPUT:
％ y (n x 2) each column is measured from a different sensor
％ ///////
％ __
％ |s1| y(:,1)
％ |__|
％ __
％ / \ ________|/
％ | | | s2 |/ y(:,2)
％ \____/ --------|/
％
％ Fs Sampling frequnecy
％
％ OUTPUT:
％ B spectrogram/Campbel diagram
％ x x-axis coordinate vector (time or Speed)
％ y y-axis coordinate vector (frequency [Hz])
This m file analyzes a coherent binary phase shift keyed(BPSK) and a amplitude shift keyed(ASK) communication system. The receiver uses a correlator(mixer-integrator[LPF]) configuration with BER measurements comparing measured and theoretical results. The bandpass and low pass used in the receiver are constructed using z transforms.
A new cable fault location method based on
wavelet reconstruction is proposed. In this method the
difference between the currents of faulty phase and sound
phase under the high voltage pulse excitation is used as the
measured signal and is decomposed in multi-scale by wavelet
transform, then reconstructed in single scale. Comparing with
traditional fault location method by travelling wave, the
presented method will not be interfered by the reflected wave
from the branch joint of cables or from other positions where
the impedances are not matched and not be influenced by fault
types, otherwise, the reflected waves can be recognized even
the faulty position is near to the measuring terminal, at the
same time, the influence of the wave speed uncertainty can be
reduced. The correctness of the proposed method is proved by
simulation results.
Analytical constant-modulus algorithm, to separate linear combinations of CM sourcesThe algorithm
is robust in the presence of noise, and is tested on measured data,
collected from an experimental set-up.
A digital fi‘equeney meter designed with FPGA development software Q-~us 11 is introduced．The 1 Hz—l MHz input measured pulse signals of the digital ii‘equency meter can be used for measuring frequency，period，pulse width and duty ratio，etc．The test results stably display O71 3 seven—segment numeric tubes，and the measuring ranges may be switched over automatically．The measuring error is equal to or less than 0．1％．
This demonstration illustrates the application of adaptive filters to signal separation
using a structure called an adaptive line enhancer (ALE). In adaptive line
enhancement, a measured signal x(n) contains two signals, an unknown signal
of interest v(n), and a nearly-periodic noise signal eta(n). The goal is to remove
the noise signal from the measured signal to obtain the signal of interest.
The idea behind differential GPS is to remove as much errors as possible from the range measurements by establishing these errors at a reference site. In its most simple setup, a GPS receiver is located at a well surveyed position and its (pseudo) range measurements are compared with the actual calculated range from this receiver to the SV s. The differences between measured ranges and calculated ranges at the reference receiver are applied as corrections to the ranges measured by other receiver(s) close by.
Quality control of production has always been a necessity
in stainless steel mills. The users of stainless
steel set ever-increasing requirements on product
quality. Many material properties can still only be
measured in laboratory but more and more measurements
are now made on-line during the production.
Especially surface defects have to be detected on-line
with a surface inspection system because of their random
appearance.
