MC13201 Technical Data, Rev. 1.1,

26

Freescale Semiconductor

8.8

RF Single Port Application with an F Antenna

Figure 16 shows a typical single port RF application in which part count is minimized and a printed copper

F antenna is used for low cost. Only the RFIN port of the MC13201 is required because the differential

port is bi-directional and uses the on-chip T/R switch. Matching to near 50 Ohms is accomplished with L1,

L2, L3, and the traces on the PCB. A balun transforms the differential signal to single-ended to interface

with the F antenna.

The proper DC bias to the RFIN_x (PAO_x) pins is provided through the balun. The CT_Bias pin provides

the proper bias voltage point to the balun depending on operation, that is, CT_Bias is at VDDA voltage for

transmit and is at ground for receive. CT_Bias is switched between these two voltages based on the

operation. Capacitor C2 provides some high frequency bypass to the DC bias point. The L3/C1 network

provides a simple bandpass filter to limit out-of-band harmonics from the transmitter.

Figure 16. RF Single Port Application with an F-Antenna

TX

1

0

1

0

TX

0

X

X

Hi-Z

Idle

1

X

X

0

Idle

0

X

X

Hi-Z

Doze

1

X

X

0

Doze

0

X

X

Hi-Z

Hibernate

1

X

X

0 (Low-Z)

Hibernate

0

X

X

Hi-Z

Off

XXX

Unknown

Table 11. CT_Bias Output vs. Register Settings (continued)

Mode

CT_Bias_en

RF_switch_mode

CT_Bias_inv

CT_Bias

L2

6.8nH

5

1

6

2

3

4

Z1

LDB212G4005C-001

L3

3.9nH

C1

1.0pF

R1

0R

R2

0R

Not Mounted

2

5

3

4

J1

SMA_edge_Receptac

C2

10pF

ANT1

F_Antenna

PAO_M

6

PAO_P

5

RFIN_P

2

RFIN_M

1

CT_Bias

3

U5

MC1320x

L1

1.8nH

L4

1.8nH