RF/IF converter XE1201 single chip transceiver Author Gael Goron

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RF/IF converter XE1201 single chip transceiver Author Gael Goron

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AN1201.01 Application Note
RF/IF converter XE1201 single chip transceiver
Author Gael Goron further information, please contact
XEMICS
mail: xemics@xemics.com Web: www.xemics.com
Introduction
This application note describes method using XE1201 World Wide Free 2.4GHz band. approach based insertion RF/IF conversion stage. XE1201 half-duplex single chip transceiver operation 433MHz band 390-470MHz band. modulation used Continuous Phase level Frequency Shift Keying (CPFSK). frequency adaptation between 2.4GHz Intermediate Frequency (IF) realized RF/IF Converter. This needs chosen into 390470 band proper operation XE1201. typical 2.4GHz application made with blocks, RF/IF converter XE1201 transceiver.
->2.4GHz ->CPFSK modulation
mixer architecture advantage making Down conversion without circuit modification. input frequency (initial carrier frequency) shifted down (up) frequencies Fout1 Fout2.
Define local oscillator frequency
According equations eg2, different frequencies defined (FLO1 FLO2). Moreover, needs chosen between 390-470MHz (XE1201 operation band), example 433MHz (commonly used Europe). down conversion, Fout equal intermediate frequency (IF) plus input frequency carrier frequency (2.4GHz). FLO1= FLO1= 433MHz 2.4GHz FLO1= 1.967GHz figure shows spectrum utilization possibilities choice.
->390-470MHz CPFSK Modulation
RF/IF
Converter
Transceiver XE1201
Figure Typical 2.4GHz Application block using XE1201
Down Conversion FLO1-Fin FLO2-Fin
General Description
principle shift 2.4GHz carrier frequency) intermediate frequency (IF) vice-versa with value inside XE1201 operation band (figure
Up/Down Conversion 2.4GHz
FLO1
1.967GHz
2.4GHz
FLO2
2.833GHz
Figure Spectrum utilization. frequency retained 1.967GHz. Since easier generate local oscillator 1.967GHz than 2.833GHz (FLO2). output mixer result (Figure consists spectra, result (Fout1) other minus result (Fout2). Therefore, carrier frequency 2.4GHz shifted down 433MHz 1.967GHz Local Oscillator. XE1201 operate normal range. frequency Fout1 easily eliminated filter.
XE1201 Operation band
Figure Principle RF/IF converter
mixer (figure used realize this conversion. This function generates different frequencies: Fout1 (eg1) Fout2 (eg2) Where Local Oscillator frequency.
Figure Mixer
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Inputs
FLO1
1.967GHz
2.4GHz
Output
Up-conversion path (figure band pass filter, with center frequency 2.4GHz, required transmission path mixer output cancel spurious products. optional band-pass filter, centered frequency, added spurious XE1201 output filtering. filter utility depends application specifications. Figure conversion path
FLO1
4.367GHz
FLO1-Fin
RF=2.4GHz
IF=433MHz Filter Mixer Filter
Figure 5:Mixer output
Power Amplifier
Image frequency
With this type architecture according equations (eg1 eg2) another frequency shifted 433MHz, image frequency (figure This parasitic frequency. Fimage Fimage 1.967GHz 433MHz Fimage =1.534GHz This frequency (1.534GHz) must cancelled. low-cost band pass filter placed before input mixer (figure center frequency 2.4GHz.
RFin 2.4GHz
Down-conversion path (figure band pass filter 2.4GHz included path cancel frequency image. optional band pass filter 433MHz cancels spurious resulting mixer operation better band rejection.
RF=2.4GHz
Noise Amplifier Filter Mixer Filter
IF=433MHz
Figure Down conversion path Moreover, Noise Amplifier added reception path Power Amplifier transmission path (figure 10).
IF=433MHz Noise Amplifier 2.4GHz Antenna Switch Image Filtering Mixer band rejection
Figure Pass-band filter
Data Clock XE1201 Data
Implementation
Real mixers generate various frequencies addition wanted ones). Their values given following formula: Fout mFLO±nFin Where integer (When m=n=1, ideal case described above)
Power Amplifier RF/IF Converter
Image Filtering
Mixer
Spurious Filtering
Figure Functional block diagram
2.4GHz F=3.501GHz F=4.367GHz
Image
Frequency
Filter
1.534GHz
1.967GHz
Filter
Figure Spectrum mixer result with image frequency
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Filters Characteristics
modulation used CPFSK with +/-200KHz frequency deviation. margin filter bandwidth required drift filters tolerance. filter needs have bandwidth -3dB around 500KHz. filter, bandwidth large according required image frequency rejection (1GHz between image frequency carrier frequency).
Components Indications
Single Chip solution Harris HFA3624 mixers LNA) Filter Murata LFJ30-03B244B084 Filter "Discrete components" Antenna switch Motorola MRFIC1801 Motorola: MC145202
XEMICS, 2001 rights reserved. Reproduction whole part prohibited without prior written consent copyright owner. information presented this document does form part quotation contract, believed accurate reliable changed without notice. liability will accepted publisher consequence use. Publication thereof does convey imply license under patent- other industrial intellectual property rights.
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RF/IF converter XE1201 single chip transceiver Author Gael Goron

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