5.1.3.1 Overview

In the ATA8210/15, directly connect the RF input and output to the antenna by an integrated SPDT switch. See Input Matching with SPDT on Application Board in the Overview from Related Links.

The following figure shows the equivalent circuit of the SPDT RF switch in RXMode extracted from 300-500 MHz S-parameter measurements without damping activated. The following table summarizes the corresponding equivalent circuit elements. To achieve a 50Ω impedance in RXMode at Ant1 (application board), a standard simulation tool can be used to calculate the element values of the matching network C4(C3) and L1(L2). See Schematic of the ATA8210/15 Application Board in the Application Board Design from Related Links. The equivalent circuit of the SPDT, the input impedance of RFIN_LB(HB) and the parasitics of the individual application board can be used for this calculation. For more details, refer to the ATA8210/ATA8215 UHF ASK/FSK Receiver Data Sheet (9344E), section 4.0, parameter number 8.50. After assembly of the calculated elements on the board, the values for C4(C3) and L1(L2) must be changed slightly to obtain a nominal reflection magnitude of equal to or less than -20 dB at Ant1.

Figure 5-5. Equivalent Circuit of the SPDT RF Switch in RXMode with SPDT_RX
Table 5-7.  Element Values for the Equivalent Circuit in RXMode with SPDT_RX

RANT_RX

CANT_RX

LC_RX

RC_RX

RRX

CRX

2 kΩ 2.8 pF2.7 nH3.3Ω 10 kΩ 2.3 pF
Figure 5-6. Equivalent Circuit of the SPDT RF Switch in RXMode with SPDT_RX2
Table 5-8. Element Values for the Equivalent Circuit in RXMode with SPDT_RX2

RANT_RX2

CANT_RX2

LC_RX2

RC_RX2

RRX2

CRX2

10 kΩ 2.1 pF7.7 nH3.1Ω 2 kΩ 2.2 pF

The following figures indicate the simplified matching circuits from the application board with and without using the SPDT, respectively. See Application Board Design from Related Links. Except for the harmonic filter, components that are not mounted or those replaced by 0Ω bridge components are not listed to facilitate comprehensibility.

Figure 5-7. Input Matching without SPDT on Application Board
Figure 5-8. Input Matching with SPDT on Application Board