T5743P6 查看數據表（PDF） - Atmel Corporation

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T5743P6

UHF ASK/FSK Receiver

Atmel Corporation 

T5743

This is described by the following formulas:

MODE

=

0 (USA) : fIF

=

-f--L---O---

314

MODE

=

1 (Europe) : fIF

=

------f-L---O-------

432.92

The relation is designed to achieve the nominal IF frequency of fIF = 1 MHz for most

applications. For applications where fRF = 315 MHz, MODE must be set to ‘0’. In the

case of fRF = 433.92 MHz, MODE must be set to ‘1’. For other RF frequencies, fIF is

not equal to 1 MHz. fIF is then dependent on the logical level at Pin MODE and on fRF.

Table 1 summarizes the different conditions.

The RF input either from an antenna or from a generator must be transformed to the RF

input Pin LNA_IN. The input impedance of that pin is provided in the electrical parame-

ters. The parasitic board inductances and capacitances also influence the input

matching. The RF receiver T5743 exhibits its highest sensitivity at the best signal-to-

noise ratio in the LNA. Hence, noise matching is the best choice for designing the trans-

formation network.

A good practice when designing the network is to start with power matching. From that

starting point, the values of the components can be varied to some extent to achieve the

best sensitivity.

If a SAW is implemented into the input network a mirror frequency suppression of

DPRef = 40 dB can be achieved. There are SAWs available that exhibit a notch at

Df = 2 MHz. These SAWs work best for an intermediate frequency of fIF = 1 MHz. The

selectivity of the receiver is also improved by using a SAW. In typical automotive appli-

cations, a SAW is used.

Figure 5 shows a typical input matching network, for fRF = 315 MHz and fRF =

433.92 MHz using a SAW. Figure 6 illustrates an according input matching to 50 W

without a SAW. The input matching networks shown in Figure 6 are the reference net-

works for the parameters given in the electrical characteristics.

Table 1. Calculation of LO and IF Frequency

Conditions

Local Oscillator Frequency

fRF = 315 MHz, MODE = 0

fRF = 433.92 MHz, MODE = 1

300 MHz < fRF < 365 MHz,

MODE = 0

fLO = 314 MHz

fLO = 432.92 MHz

fLO

=

------f--R----F-------

1

+

----1-----

314

Intermediate Frequency

fIF = 1 MHz

fIF = 1 MHz

fIF

=

-f--L---O---

314

365 MHz < fRF < 450 MHz,

MODE = 1

fLO

=

----------f--R----F-----------

1 + --------1---------

432.92

fIF

=

-----f--L---O-------

432.92

5

4569A–RKE–12/02

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