‘I&ble 6-10. Time Domain Reflection Formats

Format

 

Parameter

LlN MAG

 

Reflection Coefficient (unitless) (0 < p< 1)

REAL

 

Reflection Cbdicient (unitless) (- 1 < p< 1)

LOGMAG

 

Retnm Loss (dB)

SWR

 

Standing Wave Ratio (unitless)

Transmission Measurements Using Bandpass Mode

The bandpass mode can also transform transmission measurements to the time domain. For example, this mode can provide information about a surface acoustic wave (SAW) filter that is not apparent in the frequency domain. Figure 6-64 illustrates a time domain bandpass measurement of a 321 MHz SAW filter.

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Figure 6-64. Transmission Measurement in Time Domain Bandpass Mode

Interpreting the bandpass transmission response horizontal axis. In time domain transmission measurements, the horizontal axis is displayed in units of time. The time axis indicates the propagation delay through the device. Note that in time domain transmission measurements, the value displayed is the actual delay (not x2). The marker provides the propagation delay in both time and distance.

Marker 2 in Figure 6-63 (left) indicates the main path response through the test device, which has a propagation delay of 655.6 ns, or about 196.5 meters in electrical length. Marker 4 in Figure 6-63 (right) indicates the triple-travel path response at 1.91 ps, or about 573.5 meters. The response at marker 1 (at 0 seconds) is an RF feedthru leakage path. In addition to the triple travel path response, there are several other multi-path responses through the test device, which are inherent in the design of a SAW filter.

Interpreting the bandpass transmission response vertical axis. In the log magnitude format, the vertical axis displays the transmission loss or gain in dB; in the linear magnitude

format it displays the transmission coefficient (7). Think of this as an average of the transmission response over the measurement frequency range.

Application and OperationConoepts 6-126

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HP 8753E manual ‘I&ble 6-10. Time Domain Reflection Formats, Transmission Measurements Using Bandpass Mode