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ADMV1014

Data Sheet

Rev. A | Page 28 of 42

THEORY OF OPERATION

The ADMV1014 is a wideband microwave downconverter

optimized for microwave radio designs operating in the 24 GHz

to 44 GHz frequency range. See Figure 1 for a functional block

diagram of the device. The ADMV1014 digital settings are

controlled via the SPI. The ADMV1014 has two modes of

operation:



Baseband quadrature demodulation (I/Q mode)



Image reject I/Q downconversion (IF mode)

START-UP SEQUENCE

The ADMV1014 SPI settings require its default settings to be

changed during startup for optimum performance. To use the

SPI, toggle the RST pin to logic low and then logic high to

perform a hard reset before starting up the device.

Set Register 0x0B to 0x727C after every power-up or reset. Set

BASEBAND QUADRATURE DEMODULATION (I/Q

MODE)

In I/Q mode, the output impedance of the baseband I/Q ports is

100 Ω differential. These outputs are designed to be loaded to a

dc-coupled, differential, 100 Ω load. I_P and I_N are the

differential baseband I outputs. Q_P and Q_N are the

differential baseband Q outputs.

To set the ADMV1014 in I/Q mode, set BB_AMP_PD

(Register 0x03, Bit 8) to 0 and set IF_AMP_PD (Register 0x03,

Bit 11) to 1.

The baseband I/Q ports are designed to operate from dc to

6.0 GHz at each I and Q channel.

The BB output VCM can be changed from 1.05 V to 1.85 V. To

change the VCM, set BB_SWITCH_HIGH_LOW_COMMMON

(Register 0x0A, Bit 0) to be the opposite of Register 0x0A, Bit 6.

Also, set the MIXER_VGATE bit field (Register 0x07, Bits[15:9])

and the BB_AMP_REF_GEN bit field (Register 0x0A, Bits[6:3])

based on Table 6.

Table 6 provides the correct setting for these bit fields vs. the

required common-mode voltage.

The VCM can be further adjusted on each I or Q channel by

±15 mV by setting the BB_AMP_OFFSET_I bit field

(Register 0x09, Bits[4:0]) and the BB_AMP_OFFSET_Q bit field

(Register 0x09, Bits[9:5]) for each VCM setting shown in Table 6.

The most significant bit (MSB) for each bit field is the sign bit.

When the MSB is 1, the values of the four lower bits are

positive. When the MSB is 0, the values of the four lower bits

are negative. These bits also offer input IP2 and common-mode

rejection optimization.

The BB I/Q section of the ADMV1014 also features a baseband

amplifier with a digital attenuator that is controlled by setting

the BB_AMP_GAIN_CTRL bit field (Register 0x0A, Bits[2:1]).

Figure 44, Figure 45, and Figure 46 show the performance of the

baseband digital attenuator.

The Baseband Quadrature Demodulation to Very Low

Frequencies section shows the baseband performance to very

low demodulation frequencies.

Table 6. Common-Mode Voltage Settings

VCM (V)

MIXER_VGATE

(Register 0x07, Bits[15:9])

BB_AMP_REF_GEN

(Register 0x0A, Bits[6:3])

BB_SWITCH_HIGH_LOW_COMMON_MODE

(Register 0x0A, Bit 0)

1.05

1101010

0000

1.10

1101011

0001

1.15

1101100

0010

1.20

1101110

0011

1.25

1101111

0100

1.30

1110000

0101

1.35

1110001

0110

1.40

1110010

0111

1.50

1110101

1000

1.55

1110110

1001

1.60

1110111

1010

1.65

1111000

1011

1.70

1111010

1100

1.75

1111011

1101

1.80

0101100

1110

1.85

0101101

1111

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