ADRF6820ACPZ-R7 datasheet(28/45 Pages) AD

28 / 45 page

ADRF6820

Data Sheet

Rev. C | Page 28 of 45

I/Q POLARITY

The ADRF6820 offers the flexibility of specifying the polarity of

the I/Q outputs, where I can lead Q or vice versa. By addressing

POLI (Register 0x32, Bits[9:8]) or POLQ (Register 0x32,

Bits[11:10]), both the I and Q outputs can be inverted from

their default configuration. The flexibility of specifying the

polarity becomes important when the I and Q outputs are

processed simultaneously in the complex domain, I + jQ.

At power up, depending on whether high-side or low-side

injection of the LO frequency is applied, the I channel can

either lead or lag the Q channel by 90°. When the RF frequency

is greater than the LO frequency (low-side LO injection), the

I channel leads the Q channel (see Figure 53). On the contrary,

if the RF frequency is less than the LO frequency (high-side LO

injection), the Q channel leads the I channel by 90° (see Figure 54).

–0.10

–0.08

–0.06

–0.04

–0.02

0.02

0.04

0.06

0.08

0.10

–5

–4

–3

–2

–1

TIME (ns)

Q CHANNEL I CHANNEL

Figure 53. POLI = 1, POLQ = 2, I Channel Normal Polarity, Q Channel Normal

Polarity, fRF = 2040 MHz, and fLO = 1840 MHz

–0.10

–0.08

–0.06

–0.04

–0.02

0.02

0.04

0.06

0.08

0.10

–5

–4

–3

–2

–1

TIME (ns)

I CHANNEL

Q CHANNEL

Figure 54. POLI = 1, POLQ = 2, I Channel Normal Polarity, Q Channel Normal

Polarity, fRF = 2040 MHz, and fLO = 2240 MHz

Both the I and Q channels can be inverted to achieve the desired

polarity, as shown in Figure 55 to Figure 57, by writing to POLI

(Register 0x32, Bits[9:8]) or POLQ (Register 0x32, Bits[11:10]).

–0.10

–0.08

–0.06

–0.04

–0.02

0.02

0.04

0.06

0.08

0.10

–5

–4

–3

–2

–1

TIME (ns)

I CHANNEL

Q CHANNEL

Figure 55. POLI = 2, POLQ = 2, I Channel Invert Polarity, Q Channel Normal

Polarity, fRF = 2040 MHz, and fLO = 2240 MHz

–0.10

–0.08

–0.06

–0.04

–0.02

0.02

0.04

0.06

0.08

0.10

–5

–4

–3

–2

–1

TIME (ns)

I CHANNEL

Q CHANNEL

Figure 56. POLI = 1, POLQ = 1, I Channel Normal Polarity, Q Channel Invert

Polarity, fRF = 2040 MHz, and fLO = 2240 MHz

–0.10

–0.08

–0.06

–0.04

–0.02

0.02

0.04

0.06

0.08

0.10

–5

–4

–3

–2

–1

TIME (ns)

I CHANNEL

Q CHANNEL

Figure 57. POLI = 2, POLQ = 1, I Channel Invert Polarity, Q Channel Invert

Polarity, fRF = 2040 MHz, and fLO = 2240 MHz

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