User Guide

CC Technical Documentation System Module

RM-11

but the interference free operation in the field. In this receiver structure, linearity lies

heavily on the mixer design. The second order distortion requirements of the mixer are

set by the 'half IF' suppression. A fully balanced mixer topology is required. Additionally,

the receiver third order IIP tends to depend on active mixer IIP3 linearity due to high

LNA gain.

IF stages include a narrow-band SAW filter on the first IF and an integrated lowpass

filtering is on zero IF. The SAW filter guarantees 14 dBc attenuation at alternating

channels, which gives acceptable receiver IMD performance with only moderate VHF

local phase noise performance. The local signal's partition to receiver selectivity and IMD

depends mainly on the spectral purity of the first local. Zero 2nd IF stages include most

of the receiver’s signal gain, AGC control range, and channel filtering.

Receiver requirements and characteristics are presented in detail in the RX specification.

Frequency Synthesizers

The RM-11 synthesizer consists of three synthesizers: one UHF synthesizer and two VHF

synthesizers. The UHF synthesizer is based on an integrated PLL and external UHF VCO,

loop filter, and VCTCXO. Its main goal is to achieve the channel selection, thus for dual-

band operations associated with dual mode. Due to the RX and TX architecture, this UHF

synthesizer is used for down conversion of the received signal and for final

up-conversion in the transmitter. A common 2 GHz UHFVCO module is used for operation

on both low and high bands. The frequency divider by two is integrated in the RF ASIC.

The two VHF synthesizers consist of the RX VHF synthesizer and the TX VHF

synthesizer.The RX VHF synthesizer includes integrated PLL and VCO and loop filter and

resonator. The output of the RX-VHF PLL is used as a LO signal for the second mixer in

the receiver. The TX VHF Synthesizer and loop filter are integrated into the RF ASIC. See

the depicted block diagrams and synthesizer characteristics from the Synthesizer specifi-

cation document.

Transmitter

The transmitter RF architecture is up-conversion type (desired RF spectrum is low side

injection) with (RF-) modulation and gain control at IF. The IF frequency is 180.54 MHz.

The cellular band is 824.01-848.97 MHz and the PCS band is 1850.01-1909.95 MHz.

Common IF

The RF modulator is integrated with a Programmable Gain Amplifier (PGA) and an IF out-

put buffer inside the RFIC chip. I- and Q-signals, which are output signals from the

BB-side SW IQ-modulator, have some filtering inside the RF ASIC before RF modulation

is performed. The required LO-signal from TXVCO is buffered with phase shifting in the

RF ASIC. After modulation (p/4 DQPSK or FM), the modulated IF signal is amplified

in PGA.

Cellular Band

At operation in cellular band, the IF signal is buffered at the IF output stage that is

enabled by TXP1 TX control. The maximum linear (balanced) IF signal level to 50 W load

is about -8 dBm.