PRODUCT SPECIFICATION

nRF403 Single Chip RF Transceiver

Nordic VLSI ASA -

Vestre Rosten 81, N-7075 Tiller, Norway

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Phone +4772898900

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Fax +4772898989

Revision: 1.1

Page 7 of 18

July 2001

APPLICATION INFORMATION

Antenna input/output

The ANT1 and ANT2 pins provide RF input to the LNA (Low Noise Amplifier) when

nRF403 is in receive mode, and RF output from the PA (Power Amplifier) when

nRF403 is in transmit mode. The antenna connection to nRF403 is differential and the

recommended load impedance at the antenna port is 400

Ω.

Figure 12 shows a typical application schematic with a differential loop antenna on a

Printed Circuit Board (PCB). The output stage (PA) consists of two open collector

transistors in a differential pair configuration. VDD to the PA must be supplied

through the collector load. When connecting a differential loop antenna to the

ANT1/ANT2 pins, VDD should be supplied through the centre of the loop antenna as

shown in Figure 12.

A single ended antenna or 50

Ω test instrument may be connected to nRF403 by using

a differential to single ended matching network (BALUN) as shown in Figure 7, 433

MHz and 315 MHz operation.

nRF403

ANT1

ANT2

RF in/out 50 ohm

18nH

470pF

2.2pF

470pF

18nH

18nH

VDD

27pF

27pF

nRF403

ANT1

ANT2

RF in/out 50 ohm

18nH

470pF

470pF

18nH

18nH

VDD

15pF

15pF

a) 315MHz

b) 433MHz

xxx

xxx

Figure 7. Connection of nRF403 to single ended antenna by using

a differential to single ended matching network for 433 and 315 MHz.

A single ended antenna may also be connected to nRF403 using an 8:1 impedance RF

transformer, both 315/433 MHz operation. The RF transformer must have a centre tap

at the primary side for VDD supply.