ADRF6820ACPZ-R7 datasheet(21/45 Pages) AD

21 / 45 page

Data Sheet

ADRF6820

Rev. C | Page 21 of 45

BANDWIDTH SELECT MODES

The ADRF6820 offers four bandwidth select modes, as specified

in Table 15. The bandwidth select modes include either high gain

and low bandwidth or low gain and high bandwidth. The selection

of the resistance and capacitance in the mixer load determines

the IF gain and bandwidth. Use Register 0x34, Bits[9:8] to select

one of the four modes.

The high gain modes, BWSEL0 and BWSEL1, have equivalent

performance in terms of gain, noise figure, and linearity. Similarly,

the low gain modes, BWSEL2 and BWSEL3, share the same

performance specifications. However, the factor that distinguishes

the different modes is the IF bandwidth. Figure 39 to Figure 42

show the voltage gain, pass-band flatness, and 1 dB bandwidth

of the bandwidth modes for the various LO frequencies. Table 15

summarizes the results of Figure 39 to Figure 42.

Table 15. Mixer Gain and Bandwidth Select Modes1

BWSEL

(Reg. 0x34[9:8])

Mode

Voltage

Gain (dB)

1 dB BW

(MHz)

3 dB BW

(MHz)

BWSEL0

240

480

BWSEL1

180

340

BWSEL2

−3

600

1400

BWSEL3

−3

500

900

fLO = 2100 MHz, high-side LO injection.

LO = 1800 MHz

LO = 2100 MHz

LO = 2700 MHz

–300

–200

–100

100

200

300

IF FREQUENCY (MHz)

–4.0

–3.5

–3.0

–2.5

–2.0

–1.5

–1.0

–0.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Figure 39. Voltage Gain vs. IF Frequency, BWSEL = 0, LO Fixed and RF Swept

The LO frequency was set to 1800 MHz, 2100 MHz, and

2700 MHz, and the RF frequency was swept. With this

measurement approach, Figure 39 to Figure 42 show the effects

of both the RF and IF roll-off. The RF roll-off is determined by

the integrated RF balun, and the IF roll-off is set by the bandwidth

select mode. The effect of both the RF roll-off and IF roll-off is

most evident in the widest bandwidth mode (BWSEL2), as shown

in Figure 41. Figure 41 shows the flattest and widest bandwidth

when the LO frequency is at 2700 MHz because the RF frequency

is farthest from the roll-off of the integrated RF balun. In the fLO =

1800 MHz and fLO = 2100 MHz sweeps, the effect of the RF

balun becomes evident, resulting in a narrower 1 dB bandwidth.

It is very difficult to accurately measure the voltage gain flatness

of the ADRF6820 because the signal generators and spectrum

analyzers introduce their own amplitude inaccuracies.

Additionally, at higher frequencies, the board traces are not as

well matched, resulting in signal reflections. With the amplitude

errors/inaccuracies from the signal generators and spectrum

analyzers included in the measurement, the gain flatness of the

ADRF6820 is approximately 0.3 dB for any 100 MHz bandwidth,

or approximately 0.2 dB for any 20 MHz bandwidth. By design,

the gain flatness of the ADRF6820 is substantially better than

this; however, the measurement approach is the limiting factor,

and the result is quoted as such.

Figure 39 to Figure 42 show data for both positive and negative

IF frequencies; positive IF frequencies represent low-side LO

injection, and negative frequencies represent high-side LO

injection.

–4.0

–3.5

–3.0

–2.5

–2.0

–1.5

–1.0

–0.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

–300

–200

–100

100

200

300

IF FREQUENCY (MHz)

LO = 1800MHz

LO = 2100MHz

LO = 2700MHz

Figure 40. Voltage Gain vs. IF Frequency, BWSEL = 1, LO Fixed and RF Swept

ADRF6820ACPZ-R7 数据表(PDF) 21 Page - Analog Devices

ADRF6820ACPZ-R7 数据表(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

数据表下载