semi合集-English.pdf - 第850页

SEMI E114-0302 E © SEMI 2002 4 9.4.4 After calibration, the cab le assembly to be tested (DUT) shall be attached to Port 1 on the Ne twork Analyzer. The other end of the DUT shall be terminated with a short circuit. Afte…

SEMI E114-0302

9 Test Procedure for Determining Electrical

Length

9.1 Two test procedures can be used to determine the

electrical length of a cable assembly. One method

measures it directly at the operating frequency and the

other measures the half-wave resonant frequency to

determine the electrical length. Each method has

advantages, depending on the length of the cable

assembly. Prior to choosing a method, the equivalent

free-space length of the DUT shall be estimated in units

of distance (i.e., meters). This length can be estimated

by dividing the physical length of the DUT by the

velocity of propagation for the particular type of cable.

For example, a DUT made from RG-217 cable with a

physical length of 20 meters and a velocity of

propagation of 0.66 would have an equivalent free-

space length of 30.303 meters (20/0.66 = 30.303). A

flow chart showing the steps for choosing which test

method to use is shown in Figure 2.

9.2 The equivalent free-space length of the DUT shall

be compared with the wavelength of the nominal

operating frequency. Test Method 1 (Section 9.3) shall

be used if the equivalent free-space length is less than a

quarter wavelength of the nominal operating frequency.

Test Method 2 shall be used if it is equal to or greater

than a quarter wavelength of the nominal operating

frequency. For example, if the estimated free-space

length is 3 meters and the nominal operating frequency

is 13.56 MHz (quarter wavelength = 0.25 × c/13.56 ×

= 5.527 meters), then Test Method 1 is

recommended. If the estimated free-space length is 25

meters, then Test Method 2 is recommended.

9.3 Test Method 1 for Determining Electrical Length

9.3.1 This test method measures the phase angle of the

reflection coefficient at the nominal operating

frequency of the DUT when the DUT is terminated by a

short circuit.

9.3.2 Calibrate the Network Analyzer at the desired

operating frequency (e.g., 13.56 MHz). If adapters are

to be used to connect the DUT to the Network Analyzer

and/or to the short circuit termination, then the

calibration shall be made with the adapters in place.

The Network Analyzer shall be calibrated for

measuring the reflection coefficient at test Port 1 (see

Figure 1) using the calibration kit provided with the

Network Analyzer. This measurement is equivalent to

measuring the S11 S-parameter. The calibration shall

be performed at fixed frequency (continuous-wave

operation) using the lowest bandwidth possible

(typically 10 Hz).

9.3.3 After calibration, the cable assembly to be tested

(DUT) shall be attached to Port 1 on the Network

Analyzer. The other end of the DUT shall be

terminated with a short circuit. After all connections

have been visually inspected to ensure proper contact

and the Network Analyzer measurement has stabilized,

the value of the reflection coefficient phase angle shall

be recorded.

9.3.4 If the indicated phase angle of the reflection

coefficient is positive, then the electrical length of the

DUT is equal to one half of the value of the difference

between 180 and the measured phase angle. For

example, if the measure reflection coefficient phase

angle is 120 degrees, then the electrical length is 30

degrees ((180-120)/2).

9.3.5 If the indicated phase angle of the reflection

coefficient is negative, then the electrical length of the

DUT is greater than a quarter wavelength. For this

case, the electrical length is equal to one half of the

absolute value of the measured value of the reflection

coefficient phase angle plus 90. For example, if the

measure reflection coefficient phase angle is -10

degrees, then the electrical length is 95 degrees (90 +

10/2).

9.4 Test Method 2 for Determining Electrical Length

9.4.1 This test method determines the electrical length

of the cable assembly DUT by measuring the half wave

resonant frequency when the DUT is terminated by a

short circuit. For this measurement, the frequency of

the network analyzer is swept. The frequency range of

the sweep is determined from the estimated free-space

length of the DUT.

9.4.2 Estimate the half wave resonant frequency of the

DUT. This frequency is equal to one half of the ratio of

the speed of light divided by the estimated free space

length determined in Section 9.2. For example, if the

estimated free space length of the DUT is 25 meters,

then the estimated half wave resonant frequency is

5.996 MHz (0.5 × c/25).

9.4.3 Calibrate the Network Analyzer. If adapters are

to be used to connect the DUT to the Network Analyzer

and/or to the short circuit termination, then the

calibration shall be made with the adapters in place.

The center frequency of the frequency sweep shall be at

the estimated half wave resonant frequency calculated

in Section 9.4.2, and the frequency span of the sweep

shall be no greater than 10% of the estimated

frequency. For example, if the estimated half wave

resonant frequency is 6.0 MHz, then the frequency span

shall be no greater than 0.6 MHz. The Network

Analyzer shall be calibrated for measuring the

reflection coefficient at test Port 1 (see Figure 1) using

the calibration kit provided with the Network Analyzer.

This measurement is equivalent to measuring the S11

S-parameter. The calibration shall be performed using

the lowest bandwidth possible (typically 10 Hz).

SEMI E114-0302

9.4.4 After calibration, the cable assembly to be tested

(DUT) shall be attached to Port 1 on the Network

Analyzer. The other end of the DUT shall be

terminated with a short circuit. After all connections

have been visually inspected to ensure proper contact

and the Network Analyzer measurement has stabilized,

the value of the reflection coefficient phase angle can

be examined.

9.4.5 The indicated frequency where the reflection

coefficient phase angle is ± 180 degrees shall be

recorded. The electrical length of the DUT at the

desired nominal operating frequency (for example,

13.56 MHz) is equal to 180 degrees multiplied by the

ratio of the nominal operating frequency divided by the

measured frequency where the phase angle of the DUT

is equal to ± 180 degrees. For example, if the measured

frequency where the reflection coefficient is ± 180

degrees is 6.1 MHz, then the electrical length of the

DUT at 13.56 MHz is 400.13 degrees (180 × 13.56 /

6.1).

10 Test Setup for Power Dissipation (Loss)

Test

10.1 The Test Setup for the power dissipation (loss)

test consists of the Network Analyzer, the cable

assembly to be tested (DUT), an additional short test

cable (for transmission calibration), the appropriate

adapter (if any) to connect the DUT input to the

network analyzer, and the appropriate adapter (if any)

to connect the DUT output to the network analyzer. A

schematic of the Test Setup is shown in Figure 3.

11 Test Procedure for Determining Power

Dissipation

11.1 The test procedure for determining power

dissipation in cable assemblies will also use a Network

Analyzer. In this case, both Ports of the Network

Analyzer will be used. The transmission coefficient

will be measured (also called the S21 S-parameter).

11.2 Calibrate the Network Analyzer at the desired

operating frequency (for example, 13.56 MHz). If

adapters are to be used to connect the DUT to the

Network Analyzer and/or to the short circuit

termination, then the calibration shall be made with the

adapters in place, along with the additional section of

test cable needed for the calibration. The Network

Analyzer shall be calibrated for measuring the

transmission coefficient, S21 (see Figure 3). The

calibration shall be performed at fixed frequency

(continuous-wave operation) using the lowest

bandwidth possible (typically 10 Hz).

11.3 Connect the cable assembly DUT between the two

test Ports on the Network Analyzer (including the

additional test cable used for calibration). After

visually inspecting the connections to ensure proper

contact and the Network Analyzer measurement has

stabilized, the value of the transmission coefficient

(S21) shall be recorded.

11.4 The recorded number shall be expressed in terms

of dB (decibels) and percentage of power transferred in

the DUT. The conversion between dB and percentage

is expressed as:

)10/dBin loss(

10100% ×=TransferPower

For example, if the transmission coefficient is measured

to be –0.4 dB, then the power transfer percentage would

be 91.2%. In other words, 8.8% of the power is lost in

the DUT.

12 Test Setup for Characteristic Impedance

Variation Measurement

12.1 The Test Setup for the Characteristic Impedance

variation measurement consists of a Time Domain

Reflectometer (TDR), the cable assembly to be tested

(DUT), the appropriate adapter (if any) to connect the

DUT input to the TDR, and a standard 50-ohm load

termination (see Figure 4).

12.2 Prior to making any measurements, the TDR shall

be turned on and allowed to warm up. This time allows

for electronics to come to a stable operating condition

for the measurements.

13 Test Procedure for Determining

Characteristic Impedance

13.1 Connect a standard 50-ohm load termination to

the input of the TDR and measure the impedance. This

measurement determines the normalization factor for

the measured impedances. All reported measurements

shall be scaled by this factor by multiplying subsequent

measurements by the ratio of 50 divided by the

impedance value measured with the 50-ohm standard

load.

13.2 Prior to measuring the DUT, the nominal velocity

of propagation of the cable shall be entered into the

TDR. For example, the velocity of propagation is 0.66

for cable type RG-217.

13.3 Connect one end of the DUT to the TDR and

terminate the other end of the DUT with a short circuit.

Measure the characteristic impedance as a function of

distance along the DUT by moving the measurement

distance indicator of the TDR. Record the minimum

and maximum impedance measured over the length of

the cable assembly. The measurement shall be made

throughout the length of the DUT, including the

connectors, up to the short circuit termination.

SEMI E114-0302

13.4 At the short circuit termination, the measurement

shall be made up to the point where the falling edge of

the impedance is equal to 90 percent of the nominal

impedance. For example, if the nominal impedance is

50 ohms, then the measurement can stop at the point

where the measured value at the short circuit

termination is equal to 45 ohms (0.9 × 50 = 45). An

example plot showing the measurement termination

point is shown in Figure 5.

NOTE 1: The termination point can be verified by

disconnecting the short circuit termination and observing that

the impedance increases rapidly due to the open circuit.

14 Reporting Test Results

14.1 Report the type of Network Analyzer and the

details of the Network Analyzer parameters used for the

tests, including the bandwidth, the number of data

points, the test frequency, and the frequency span (if

any). An example data sheet is shown in Table 1.

14.2 Report the type of Time Domain Reflectometer

used for the test.

14.3 Report the length of the cable assembly in terms

of degrees at the nominal operating frequency.

14.4 Report the power dissipation in terms of dB

(decibels) and percentage of power transfer.

14.5 Report the variation in characteristic impedance in

terms of the minimum and maximum after the values

have been scaled according to the reference 50-ohm

load.

15 Related Documents

15.1 IEEE Standards

IEEE-STD-572 — IEEE Standard for Qualification of

Class 1E Connection Assemblies for Nuclear Power

Generating Stations

15.2 MIL-Specifications

MIL-PRF-31031A — General Specification for

Connectors, Electrical, Plugs and Receptacles, Coaxial,

Radio Frequency, High Reliability, for Flexible and

Semirigid Cables

MIL-STD-348A — Radio Frequency Connector

Interfaces for MIL-C-3643, MIL-C-3650, MIL-C-3655,

MIL-C-25516, MIL-C-26637, MIL-PRF-39012, MIL-

PRF-49142, MIL-PRF-55339, and MIL C-83517

MIL-STD-220B — Test Method Standard: Method of

Insertion Loss Measurement

Port 1

Short Circuit

Termination

Cable Assembly to be tested

Network

nal

zer

NOTE: The reflection coefficient calibration is at the Port 1 output. The cable assembly to be tested (DUT) attaches to Port 1

and is terminated with a short circuit.

Figure 1

Schematic of the Network Analyzer Test Setup for the Electrical Length Measurement