APN1005 データシートの表示（PDF） - Skyworks Solutions

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APN1005

A Balanced Wideband VCO for Set-Top TV Tuner Applications

Skyworks Solutions 

APPLICATION NOTE • APN1005

100

1.0

Approximation

Measured

0.8

10

0.6

0.4

1

0.2

0.1

0

0

5

10 15 20 25 30

Varactor Voltage (V)

Figure 6. SMV1265 Capacitance vs. Voltage

2.6

2.4

2.2

2.0

1.8

1.6

RS_PWL

1.4

1.2

0

RS Measured

5

10 15 20 25 30

Varactor Voltage (V)

Figure 7. SMV1265 Resistance vs. Voltage

Figure 6 demonstrates the quality of the piece-wise fitting

approach.

Special consideration was given to the fit at the lowest capaci-

tance range (high-voltage area) since it dramatically affects the

upper frequency limit of the VCO.

To incorporate this function into Libra, the pwl() built-in function

was used in the “variables” component of the schematic bench.

M = pwl (VVAR 0 2 2.5 2 2.500009 25 6.5 25 6.50009 7.3 11

7.3 11.0009 1.8 40 1.8)

VJ = pwl (VVAR 0 4 2.5 4 2.500009 68 6.5 68 6.50009 14 11

14 11.0009 1.85 40 1.85)

CP = pwl (VVAR 0 0 2.5 0 2.500009 0 6.5 0 6.50009 0.9 11

0.9 11.0009 0.56 40 0.56)

CJO = pwl (VVAR 0 22.5 2.5 22.5 2.500009 21 6.5 21 6.50009

20 11 20 11.0009 20 40 20)*1012

Note: While CP is given in picofarads, CGO is given in farads to

comply with the default nominations in Libra. (For more details

regarding pwl() function see Circuit Network Items, Variables and

Equations, Series IV Manuals, p. 19–15).

Since the epitaxial layer for this kind of hyperabrupt varactor has

relatively high resistivity, the series resistance is strongly depen-

dent on the reverse voltage applied to varactor junction. The

value of series resistance (RS) measured at 500 MHz is shown in

Figure 7, with a piece-wise approximation of RS also given.

The piece-wise function may be used as follows:

RS = pwl (VVAR 0 2.4 3 2.4 4 2.3 5 2.2 6 2 7 1.85 8 1.76 9

1.7 10 1.65 11 1.61 12 1.5 40 1.5)

Note: The pwl() function in Libra IV is defined for the evaluation of

harmonic balance parameters rather than variables. Therefore,

although series resistance was defined as dependent on reverse

voltage, for harmonic balance it remains parametric and linear.

The same applies to capacitance, which remains the same as in

the original diode model, but its coefficients (VJ, M, CJO, and CP)

become parametric functions of the reverse voltage.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

6

July 21, 2005 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • 200314 Rev. A

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