Agilent Technologies 22A Specifiche Scaricare il pdf (Pagina 87)

In examining Figure 7-5, we find some additional complications. The

spectrum analyzer is set up to operate in several tuning bands. Depending

on the frequency to which the analyzer is tuned, the analyzer display is

frequency calibrated for a specific LO harmonic. For example, in the 6.2

to 13.2 GHz input frequency range, the spectrum analyzer is calibrated for

the 2

–

tuning curve. Suppose we have an 11 GHz signal present at the input.

As the LO sweeps, the signal will produce IF responses with the 3

, 3

–

, 2

and 2

–

tuning curves. The desired response of the 2

–

tuning curve occurs

when the LO frequency satisfies the tuning equation:

11 GHz = 2 f

– 0.3

= 5.65 GHz

Similarly, we can calculate that the response from the 2

tuning curve

occurs when f

= 5.35 GHz, resulting in a displayed signal that appears

to be at 10.4 GHz.

The displayed signals created by the responses to the 3

and 3

–

tuning curves

are known as in-band multiple responses. Because they occur when the LO is

tuned to 3.57 GHz and 3.77 GHz, they will produce false responses on the

display that appear to be genuine signals at 6.84 GHz and 7.24 GHz.

3.57

3.77

5.35

5.65

In-band

multiple

responses

–

LO frequency (GHz)

Signal frequency (GHz)

Band 0

(lowband)

Band 1

Band 2

Band 3

Band 4

–

10.4

7.24

6.84

Apparent location of an

input signal resulting from

the response to the 2

tuning curve

Apparent locations of

in-band multiples of an

11 GHz input signal

Figure 7-5. Tuning curves up to 4th harmonic of LO showing in-band multiple responses

to an 11 GHz input signal.

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Agilent Technologies 22A Specifiche Pagina 87

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