ATA5745 datasheet(6/43 Pages) ATMEL

6 / 43 page

4596A–RKE–05/06

ATA5745/ATA5746 [Preliminary]

2.2

Input Matching at LNA_IN

The measured input impedances as well as the values of a parallel equivalent circuit of these

impedances can be seen in Table 2-1. The highest sensitivity is achieved with power matching

of these impedances to the source impedance.

The matching of the LNA input to 50

Ω is done using the circuit shown in Figure 2-1 and the val-

ues of the matching elements given in Table 2-2. The reflection coefficients were always

≤ –10 dB. Note that value changes of C1 and L1 may be necessary to compensate individual

board layout parasitics. The measured typical FSK and ASK Manchester-code sensitivities with

a bit error rate (BER) of 10

–3 are shown in Table 2-3 and Table 2-4 on page 7. These measure-

ments were done with wire-wound inductors having quality factors reported in Table 2-2,

resulting in estimated matching losses of 0.8 dB at 315 MHz and 433.92 MHz. These losses can

be estimated when calculating the parallel equivalent resistance of the inductor with

loss =2 ×π × f × L × QL and the matching loss with 10 log(1+RIn_p /Rloss).

Figure 2-1.

Input Matching to 50

Ω

Table 2-1.

Measured Input Impedances of the LNA_IN Pin

RF [MHz]

In(RF_IN) [Ω]RIn_p//CIn_p [pF]

315

(72.4 – j298)

1300

Ω//1.60

433.92

(55 – j216)

900

Ω//1.60

Table 2-2.

Input Matching to 50

Ω

RF [MHz]

1 [pF]

1 [nH]

315

2.2

433.92

2.2

RFIN

LNA_IN

ATA5745/ATA5746

ATA5745 Datasheet(PDF) 6 Page - ATMEL Corporation

ATA5745 Datasheet(HTML) 6 Page - ATMEL Corporation

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

Datasheet Download

Link URL