EVB7122

27 to 930MHz Transceiver

Evaluation Board Description

39012 07122 02

Page 3 of 24

EVB Description

Rev. 005

June/07

1

Theory of Operation

1.1

General

The main building block of the transceiver is a programmable PLL frequency synthesizer that is based on an

integer-N topology. The PLL is used for generating the carrier frequency during transmission and for

generating the LO signal during reception. The carrier frequency can be FSK-modulated by pulling the

crystal and ASK-modulated by on/off keying of the power amplifier. The receiver is based on the principle of

a single conversion superhet. Therefore the VCO frequency has to be changed between transmit and

receive mode. In receive mode, the preferred LO injection type is low-side injection.

The TH7122 transceiver IC consists of the following building blocks:

"

Low-noise amplifier (LNA) for high-sensitivity

RF signal reception with switchable gain

"

Mixer (MIX) for RF-to-IF down-conversion

"

IF amplifier (IFA) to amplify and limit the IF

signal and for RSSI generation

"

Phase-coincidence demodulator with external

ceramic discriminator (FSK Demodulator)

"

Operational amplifier (OA1), connected to

demodulator output

"

Operational amplifier (OA2), for geral use

"

Peak detector (PKDET) for ASK detection

"

Control logic with 3wire bus serial control

interface (SCI)

"

Reference oscillator (RO) with external crystal

"

Reference divider (R counter)

"

Programmable divider (N/A counter)

"

Phase-frequency detector (PFD)

"

Charge pump (CP)

"

Voltage controlled oscillator (VCO) with internal

varactor

"

Power amplifier (PA) with adjustable output

power

1.2

Technical Data Overview

!

Frequency range: 300 MHz to 930 MHz in

programmable user mode

!

Extended frequency range with external VCO

varactor diode: 27 MHz to 930 MHz

!

315 MHz, 433 MHz, 868 MHz or 915 MHz fixed-

frequency settings in stand-alone mode

!

Power supply range: 2.2 V to 5.5 V

!

Temperature range: -40 °C to +85 °C

!

Standby current: 50 nA

!

Operating current in receive: 6.5 mA (low gain)

!

Operating current in transmit: 12 mA (at -2 dBm)

!

Adjustable RF power range: -20 dBm to

+10dBm

!

Sensitivity: -105 dBm at FSK with 180 kHz

IF filter BW

!

Sensitivity: -107 dBm at ASK with 180 kHz

IF filter BW

!

Max. data rate with crystal pulling: 20 kbps NRZ

!

Max. data rate with direct VCO modulation:

115 kbps NRZ

!

Max. input level: -10 dBm at FSK

and -20 dBm at ASK

!

Input frequency acceptance:

± 10 to ± 150 kHz

(depending on FSK deviation)

!

FM/FSK deviation range:

±2.5 to ±80 kHz

!

Analog modulation frequency: max. 10 kHz

!

Crystal reference frequency: 3 MHz to 12 MHz

!

External reference frequency: 1 MHz to 16 MHz

1.3

Note on ASK Operation

Optimum ASK performance can be achieved by using an 8-MHz crystal for operation at 315 MHz, 434 MHz

and 915 MHz. For details please refer to the software settings shown in sections 4.2 and 4.3. FSK operation

is the preferred choice for applications in the European 868MHz band.

For more detailed information, please refer to the latest TH7122 data sheet revision