P2602

ETALDOC 258/8

Page 3 of 4

February 2006

halves of the tapped winding will not be

greater than 5Ω.

MATCHING RECOMMENDATIONS

CONSTRUCTION

Recommended Circuit

Fig. 2

560

LINE

600

* If return loss > 16dB, 300Hz - 4kHz is acceptable, bloc king

capacitor may be relaxed to 4.7 F

33nF

27nF

5%

+_

2%

+_

μ

*

+50%

20%

_

μ

6.8 F

+50%

20%

_

5%

+_

600 MATCH

Ω

Figure 3 gives flat RX and TX responses against the

CTR21 complex reference impedance (typically

around ±0.5dB 300Hz - 3.4kHz). Return loss is

typically better than 20dB.

The circuit values in

parentheses give optimum flatness at a small

sacrifice in return loss.

For circuits with existing board drillings, figure 4

gives good return loss (>20dB) and RX flatness

against the CTR21 complex reference impedance,

but TX flatness is degraded by the use of this

topology.

EUROPEAN CTR21 COMPLEX MATCH

Recommended Circuit

Fig. 3

150

(220)

LINE

270

750

750

(680)

56nF

(150nF)

100nF

150nF

μ

2.2 F

Fig. 4

820

LINE

270

750

330

27nF

68nF

150nF

μ

2.2 F