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118 Chapter 4

Performance Tests

3. Multiple Response Rejection Test

Performance Tests

3. Multiple Response Rejection Test

Description

The multiple response rejection is checked at an LO power level of +15.2 dBm. A known

input power is applied to the input of the mixer. The IF output power is measured on

an 8566B Spectrum Analyzer at the input signal frequency and at the multiple response

frequencies. From the measurements, the multiple response rejection is determined. For

each mixer, the spectrum analyzer/mixer combination is calibrated in frequency and

amplitude for mixing with a certain harmonic of the local oscillator. Multiple responses are

a result of the RF input’s mixing with a harmonic of the local oscillator other than the

harmonic that the spectrum analyzer is calibrated for. The multiple responses appear on

the spectrum analyzer at frequencies described by the following equation:

where n represents the harmonic number for calibrated operation, as listed below.

for an 11974A: 8

for an 11974Q: 10

for an 11974U: 10

for an 11974V: 14

and n

′

= Harmonic number producing unwanted multiple responses. The harmonics that

produce the highest level multiple responses tend to be n

′

= n + 2 and n

′

= n − 2. For

example, for the 11974U, these would be n

′

= 8 and n

′

= 12. This test measures the rejection

of multiple responses caused by n

′

= n − 2 and n

′

= n + 2 for signals at the lowest, middle,

and highest frequencies of each band.

Procedure

1. Connect an SMA cable from the 1ST LO OUTPUT of the spectrum analyzer to the

INPUT of the 11975A Amplifier. Connect a second SMA cable to the OUTPUT of the

amplifier.

2. Connect the 8481A Power Sensor to the 436A Power Meter sensor cable, then zero and

calibrate the 436A Power Meter.

3. Set the spectrum analyzer controls as follows:

SHIFT ⇑ ⇑ ⇑ ⇑ (selects U Band)

FREQUENCY SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz

CENTER FREQUENCY (sets LO frequency to 5.0 GHz) . . . . . . . . . 50.3 GHz

f′

n′

----





n′ n±

n′

-----------





GHz+=

1 2 ... 113 114 115 116 117 118 119 120 121 122 123 ... 153 154

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