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Phone: 978-250-3343

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Application Support: Phone: 978-250-3343 or apps@hittite.com

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HMC993LP5E

v00.0911

RF AUTOMATIC GAIN CONTROLLER

(RF-AGC), 700 - 3000 MHz

Figure 2: Pout vs. Pin at 1900 MHz, 1 attenuator

Therefore, increasing the VCTRL pin voltage reduces the gain of the HMC993LP5E’s VGA and increases input power

level required for power saturation. When the input signal is weak, the attenuation level of the variable attenuators

should be reduced. When the input signal is large; the attenuation level of the variable attenuators should be increased

to achieve a constant output level.

The gain control performance of the HMC993LP5E at 1900 MHz is shown in Figures 3. The HMC993LP5E provides

22.2 dB of gain control range with a maximum gain of 26 dB when it is configured in 1 attenuator + 2 amplifiers mode,

and similarly a 33.6 dB of gain control range with a maximum gain of 21.5 dB of gain when it is configured in 2 attenua-

tors + 2 amplifiers mode. The HMC993LP5E’s VGA has a very flat linear-in-dB gain control characteristic with a slope of

-12.97 dB/V for the 2 attenuators configuration and -7.28 dB/V for the 1 attenuator configuration. The log-linearity error

of the HMC993LP5 VGA is typically less than ± 2dB over the entire gain control range.

Noise and Distortion

As with any multistage VGA consisting of voltage variable attenuators and gain blocks, the noise figure (NF) and input

referred distortion (IIP3) characteristics of the HMC993LP5E’s VGA are dependent on the gain control voltage VCTRL.

When the attenuation level of the variable attenuators is set to minimum (maximum gain state), the noise figure of the

HMC993LP5E’s VGA is minimized; however the IIP3 is degraded to minimum as well. The noise figure and IIP3 of the

HMC993LP5E’s VGA increases with the attenuation level of the variable attenuators.

For low attenuation levels, the noise contribution from the VGA is important since the input signal is weak. For high atten-

Figure 3: Gain vs. VCTRL at 1900 MHz

-50

-40

-30

-20

-10

0

10

20

30

-70

-60

-50

-40

-30

-20

-10

0

10

VCTRL=1 V

VCTRL=2 V

VCTRL=3 V

VCTRL=4 V

INPUT POWER (dBm)

-20

-10

0

10

20

30

1

1.5

2

2.5

3

3.5

4

1 Attenuator

2 Attenuators

VCTRL (V)