ADRF6820

Data Sheet

Rev. C | Page 20 of 45

RF BALUN INSERTION LOSS OPTIMIZATION

As shown in Figure 34 to Figure 37, the gain of the ADRF6820

mixer was characterized for every combination of BAL_CIN and

BAL_COUT (Register 0x30, Bits[7:0]). As shown, a range of

BAL_CIN and BAL_COUT values can be used to optimize the

gain of the ADRF6820. The optimized values do not change with

temperature. After the values are chosen, the absolute gain changes

over temperature; however, the signature of the BAL_CIN and

BAL_COUT values is fixed.

At lower input frequencies, more capacitance is needed. This

capacitance increase is achieved by programming higher codes into

BAL_CIN and BAL_COUT. At higher frequencies, less capacitance

is required; therefore, lower BAL_CIN and BAL_COUT codes

are appropriate. Figure 38 shows the change in gain over frequency

for various BAL_CIN and BAL_COUT codes. Use Figure 34 to

Figure 38 only as guides; do not interpret them in the absolute

sense because every application and PCB design varies. Additional

fine-tuning may be necessary to achieve the maximum gain.

Table 16 shows the recommended BAL_CIN and BAL_COUT

settings for various RF frequencies.

–4.0

–3.5

–3.0

–2.5

–2.0

–1.5

–1.0

–0.5

0

–40°C

+25°C

+85°C

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0

1

2

3

4

5

6

7

–

12

–

10

–

8

–

6

–

4

–

2

0

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0

1

2

3

4

5

6

7

–40°C

+25°C

+85°C

–

10

–

9

–

8

–

7

–

6

–

5

–

4

–

3

–

2

–

1

0

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0

1

2

3

4

5

6

7

–40°C

+25°C

+85°C

–

16

–

14

–

12

–

10

–

8

–

6

–

4

–

2

0

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0

1

2

3

4

5

6

7

–40°C

+25°C

+85°C

500

700

900

1100 1300 1500 1700 1900 2200 2400 2600

–12

–10

–8

–6

–4

–2

0

RF FREQUENCY (MHz)

CIN = 0, COUT = 0

CIN = 1, COUT = 1

CIN = 2, COUT = 2

CIN = 3, COUT = 3

CIN = 4, COUT = 4

CIN = 5, COUT = 5

CIN = 6, COUT = 6

CIN = 7, COUT = 7

Figure 38. Gain vs. RF Frequency for Various BAL_CIN and BAL_COUT Codes