Integration Guide

10/15
29.10.2019
Anticimex Innovation Center A/S
Skovgaardsvej 25
3200 Helsinge, Denmark
Phone [phone], [e-mail]
anticimex.com/innovationcenter
Reg no. DK30350766
Registered office:
Helsinge
Receive path
The antenna receives the electro-magnetic waves and generates a single 50Ω ended signal.
This signal is impedance transformed and converted to a differential signal through a
discrete balun then the differential signals enter the chip through RF_N and RF_P. Inside the
chip, the signal is then amplified through a two stage differential RF LNA. The amplified RF
signal is down converted through an IQ differential down converting mixer. The Low IF (0-
1MHz) signal is filtered through an anti-aliasing filter and imposed on to the differential ADC.
Further digital filtering, down converting to base-band and the de-modulation is then done
within the DSP circuitry. The demodulated data can be clocked out on an IO pin or stored in
internal memory for future use. I and Q are two identical differential signals with a 90 degree
phase difference. When this signal is used as LO signal in a balanced IQ–mixer, a greater
suppression of the image frequency is achieved that improves the receiver selectivity
(improving signal suppression at image frequency). The local oscillator is a standard crystal
oscillator operating at the fundamental crystal frequency (48MHz). The oscillators are
amplitude regulated to suppress the generation of harmonic frequencies. The VCO is a
standard multi-vibrator with oscillation frequency determined by its LC tank. The capacitor in
this tank is introducing the voltage dependent oscillation frequency. The VCO has a range
from 4.2 GHz to 5.6 GHz and this is divided by a division ratio of 30, 15, 12, 6 or 5 to achieve
oscillation at the required ISM range. The used division ratio for the gateway is 5.
Transmit path
Frequency modulation is achieved through instantaneous changing the division ratio in the
synthesizer. This signal then led through a divide by two circuit, generating the IQ signals
used during reception. Only one of these output signals is connected to the multistage
amplifier used to generate the differential output signal. This amplified signal is then passed
to the RF_N and RF_P pins if configured differentially. The signal is converted to single-ended
signal and filtered through the external balun, impedance matching and low-pass filter
circuitry.
Finally the resulting signal is imposed on the antenna and converted to electro-magnetic
waves. The whole transmit chain is fully differential from the VCO within the synthesizer to
the RF_P and RF_N pins. The output frequency is generated through a PLL circuit. The output
frequency is a result of the division ratio of the loop divider N, the reference divider M and
the crystal frequency. The res.ult, Fout=N*Xosc/M, is then the required frequency. The VCO
operates at 5xf
RF
which equals 4630MHz for operation at the highest channel (926MHz)