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Design Notes

WJ SME 1400B 10 One Tone Diagram:

This example demonstrates the VSS file based mixer MIXER_F. The gain conversion (GCONV) of the mixer is set to -7.5dB. The oscillator frequency (fLO) is set to 2000MHz and its power (PLO) is 10dBm. The input tone (fInp) is set to 1950MHz and its power (PIn) is -10dBm.

MIXER_F is dependent on an external spur table. The data file "WJ SME 1400B 10" is derived from the datasheet for the WJ SME 1400B-10 mixer. The first row of the data file is designated as a comment by the exclamation mark and is used to number the columns.

The first column/first row value, 0, is ignored since it does not correspond to any harmonic or intermodulation product.

Each row represents the input harmonics, each column represents the LO harmonics, with the top row and left column representing the first harmonic. For example, the value 33 in column 2, row 1 (the first row is 0 since there is no input contribution to the LO harmonics) of the data file designates a 33dBc spur at 2*fLO - 1*fInp (2050MHz) and 2*fLO + 1*fInp (5950MHz).

Values in the table greater than or equal to 100 indicate no spur is to be generated. The actual limit is determined by the SUPPLIM parameter. The expected spurs for the above settings are:

LO (n)

RF (m)

MHz

dBc

dBm

1

-1

50

0

-17.5

2

-2

100

56

-73.5

3

-3

150

68

-85.5*

-1

2

1900

55

-72.5

0

1

1950

27

-44.5

1

0

2000

34

-51.5

2

-1

2050

33

-50.5

3

-2

2100

55

-72.5

4

-3

2150

73

-90.5

-1

3

3850

69

-86.5

0

2

3900

63

-80.5

1

1

3950

0

-17.5

2

0

4000

44

-61.5

3

-1

4050

12

-29.5

4

-2

4100

59

-76.5

5

-3

4150

47

-64.5

1

2

5900

55

-72.5

2

1

5950

33

-50.5

3

0

6000

46

-63.5

4

-1

6050

35

-52.5

5

-2

6100

59

-76.5

0

4

7800

77

-94.5

1

3

7850

69

-86.5*

2

2

7900

56

-73.5

3

1

7950

12

-29.5

4

0

8000

57

-74.5

5

-1

8050

28

-45.5

The mixer LOHTYP parameter is set to "dBc LO" according to the WJ SME 1400B specs.  With PLO=10dBm, the LO harmonics should be:

      MHz   dBm

1xLO  2000  -24 

2xLO  4000  -34

3xLO  6000  -36

4xLO  8000  -47

The results shown in the graph "WJ SME 1400B Spectrum" graph agree with the values in the above table. For example, the 7900MHz tone in the graph is at -73.5dBm, which agrees with the value in the table.  An RFI spectral measurement is also plotted.

System Diagram - WJ SME 1400B 10 One Tone

Graph - WJ SME 1400B 10 Spectrum