motorola K3 Theory of Operation

MOTOKRZR K3 – Theory of operation - v.1.0. – 2006.12.10

MOTOKRZR K3
Theory of operation

1. Overview

Motorola MOTOKRZR K3 phone delivers 3G features in a thin and narrow clam KRZR form factor. It is
a dual-mode phone, tri-band GSM plus W-CDMA 2100 for the European market. It is based on the
Freescale Argon LV and RF Colorado2 platform.

As a 3G product, the MOTOKRZR K3 complies with all key specifications as defined by the 3GPP.

Key Points and Features

• Form Factor: Thin Clam

• Finish: Premium CMF

• Color: Dark Pearl Grey, Stone Grey

• Dimensions: 103.2 x 42.3 x 16.3mm / Approx 63cc

• Bands/Modes: WCDMA 2100 (HSDPA DL 3.6Mbps), GSM/GPRS class 12/EDGE class 12

triband: 900/1800/1900

• Antenna: internal – main (GSM TX/RX), secondary (WCDMA RX), Bluetooth

• Imagers - external: 2MP Camera – internal (for video telephony): VGA

• Display – internal: 2.0” 240x320 QVGA 262K color – external (for CLI): 1.3” 120 x 160 262K

TFT

• Memory: 64M On-Board plus removable Micro SD slot

• Bluetooth: Stereo (A2DP/AVRCP)

• Messaging: MMS, EMS 5.0, IM Wireless Village, Email (POP3, SMTP, IMAP4)

• Video: MPEG4, h.263 Capture / playback

• Audio: MIDI,MP3, WMA, AAC / AAC+ , Enhanced AAC+, WMA

• Connectivity: Mini USB 2.0 FS, MotoSync, BT Class 2

• Speakers: Independent Name & Digit Dialing

• Battery: BT50 High Capacity (min: 910mAh, typ: 950 mAh)

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MOTOKRZR K3 – Theory of operation - v.1.0. – 2006.12.10

2. Overall block diagram

The overall block diagram is shown in Figure 1

The phone is equipped with three antennas. The first one (MAIN low-profile FICA antenna) is a
tri-band antenna used for both TX and RX on GSM bands, along with WCDMA TX. The connection
to the proper TX/RX line-up is switched by the front-end module (FEM).

The second antenna is connected to the only WCDMA RX line-up, thus providing a way to monitor
the WCDMA downlink signal, independently of the band and the technology that the phone is
transmitting and camped on. In particular, it is not necessary to use downlink compressed mode for
3G-2G hand-over, while in WCDMA call and monitoring GSM cell by the main antenna. However,
compressed mode must be used for uplink in the same scenario – since the WCDMA TX signal is
switched by the FEM along with the GSM RX ones.

The third antenna is used by the only Bluetooth IC, for both TX and RX

Figure 1. Overall block diagram

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3. RF Section

3.1. Front-end module

The Front End Module integrates two GaAs switches, a diplexer, and a 3-line control decoder in a
low profile plastic mold package. A simplified block diagram is shown in Figure 2.

The module provides band selection and filtering between the antenna and the transceiver circuitry
for Colorado II chipset-based phones. This includes GSM850, GSM900 and WB850 band V (which
includes Japanese band VI) receive and transmit bands on the low pass side of the diplexer, and
GSM1800, GSM1900, WB1900 (band II) receive and transmit bands, and WB2100 (band I) transmit
band on the high pass side. This phone uses only the GSM900, DCS1800, PCS1900 and
WCDMA2100 paths.

Figure 2. Front-end module (FEM) simplified block diagram

As mentioned in the previous section, the design of this module is assuming a separate antenna
dedicated to the WCDMA2100 receiver. This antenna should have at least 10 dB isolation from the
main antenna in the 2110-2170 MHz band.

3.2. RF WCDMA Receiver

3.2.1. LNA (U300)

WCDMA receive signals from the secondary antenna are fed into a ceramic 3-pole pre-select band
pass filter (FL001) through an antenna matching network and RF connector (M002). If M002 is used,
all WCDMA signals are fed into M001. Also, the internal antenna path will be in an open state when
M001 is used.

From the band-pass filter, the W2100 Rx signal is fed into the 2100 MHz band Low Noise Amplifier
(U300) through a second Rx matching network.

The LNA is controlled by Symphony through two enable lines. Gain line is used to put LNA into either

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high gain or low gain mode, depending on the input power level. The LNAs turn off at antenna input
level threshold around -70 dBm and turns on at input level threshold around -68 dBm.

3.2.2. Symphony Rx (U100)

Symphony (U100) is a programmable mixed-signal quadband exciter (Tx) and receiver back-end
(Rx) for a UMTS W-CDMA cellular radio (UE) operating in FDD mode. The functional interface of this
part is RF at the carrier frequency and digital baseband. The four bands supported are UMTS (Band
I), North American PCS (Band II), North American 800 (Band V), and Japan 800 (Band VI). Only
Band I is used for this phone.

Figure 3 Symphony (Rx)

The frequency generation within the part supports variable duplex frequency spacing (Rx/Tx) per
3GPP requirements though the intention at this time is to use the part in fixed duplex mode. Because
of this requirement, the Rx and Tx have separate VCO’s and PLL’s, and their operation is
independent of the other. Loop filters are internal to the module.

The SPI (serial programming interface) is used to setup the part for operation and is programmed by
the baseband processor. The SPI supports read and write operations to/from the internal
programmable registers. In addition to static operational modes defined by some of the register
values, the part also includes “sequence managers” that utilize a pre-programmed sequence of
instructions to dynamically enable, control, and disable the transceiver. The sequence managers
are triggered by layer 1 timed control signals from the baseband processor.

The receiver architecture is a direct conversion receiver (DCR). The inputs drive three sets of
differential quadrature mixers, one for each frequency band. Preselection filters, LNA’s, and
interstage filters must be provided externally to the inputs. The mixer inputs are internally matched to
pre-defined interstage filter output impedances.

The mixer zero-IF outputs are low pass filtered and amplified internally with a variable gain amplifier,
also known as the post-mixer amplifier (PMA). The dynamic range of the PMA is driven by the AGC
system requirements. Finally, the I/Q signals are digitized, digitally filtered, and output in a serial
fashion to the DSP demodulator in the baseband processor.

This particular module is a Multi-Chip Module (MCM) integrated on an organic High Density

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Interconnect (HDI) substrate. The module contains two IC’s named internally as “Melody”
(RF/baseband interface IC) and “Viper” (RFIC). Supporting discrete components are placed inside
the module such as impedance matching networks, PLL loop filters, and supply bypass capacitors.
Melody is paired with ArgonLV (U1000), which is the baseband processor. ArgonLV includes the
DSP core known as “WAMMO”.

3.3. RF WCDMA Transmitter

3.3.1. Symphony Tx (U100)

The transmitter architecture is direct launch. The inputs are serial digital baseband I/Q from the DSP
modulator in ArgonLV. They are digitally filtered and then converted to baseband analog signals.
After filtering, the I/Q signals are quadrature modulated and upconverted directly to the carrier
frequency. The RF signal is input to a variable gain amplifier (VGA) that is controlled by the AOC
feedback system for precise power control.

Finally, the RF is routed to a set of three PA driver stages, one for each frequency band, that serves
as the module’s output. Provided externally to this part are pre-PA filtering, PA amplification, power
detection, and final Tx filtering.

Figure 4 Symphony (Tx)

3.3.2. WCDMA PA (U400)

The PASSKEY-5W PA (U400) is a 50 ohm, single-band, single-mode, WCDMA PA modules
intended for 3G radio applications. The module integrates an inter-stage filter, power amplifier,
coupler, power detector. It has Tx band-pass filter internal to the module.

The 5W module includes a Tx band-pass filter at the input and output, as shown in the module block
diagram in Figure 5.

A Motorola proprietary high power / low power efficiency enhancement load (EE Ld) switch is
included in the output match. For the EE Ld switch, VMODE voltage level changes the output load

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for optimum efficiency from low power to high power out. A bias line (Vba) is available for band/mode
optimization for ACLR and current.

The PA has an internal RF detector which is used for feedback to the AOC system.

The PA can be set in two modes, the High Power Mode (HPM) and the Low Power Mode (LPM). The
modes are selected by setting WB_PA_VLD (Vmod) line. When VLD is set high (2.4V), the PA is in
LPM. When VLD is set low (0V), the PA is in HPM. In LPM, the gain of the PA is variable. The PA
gain can be varied by applying different PA biases on the WB_PA_VBIAS (VBA) line. The range for
LPM is from 16dBm to below -50dBm. In HPM the gain of the PA is the highest, about 20 to 23 dB.
HPM is any power above 16dBm to 23 dBm at the antenna port. The PA bias, VBA is set to about

2.2V.

Figure 5. Passkey 5W PA block diagram

The WCDMA TX lineup can also be operated in a Open Loop or Closed Loop Mode. The Open Loop
mode is generally from below -50 to +3dBm, below the operating range of the RF detector. The Tx
power is set by calibration tables. The AOC system calculates the required TX index for the required
power level and applies any channel LPM correction. Since the detector feedback is not used, the
AOC system is not aware of the actual transmitted power.

The Closed Loop Mode is power levels above 3dBm, within the range of the RF detector. The Tx
power is dynamically adjusted based on RF detect feedback. The detector within the PA is used to
provide feedback to Symphony (AOC system) about the current output power level from the PA.

3.4. EGPRS Transceiver

3.4.1. Introduction

This phone is using an highly integrated EGPRS transceiver providing bits to antenna capability
through the combination of the TransAAM transceiver module with the Orphee PA module. Figure 6
shows the major subsystems integrated into the TransAAM / Orphee modules.

The transceiver works over the GSM850 (not used on this phone), EGSM900, DCS1800, and
PCS1900 transmit and receive frequency bands. It includes a VLIF/DCR receive architecture with
integrated LNAs and a polar modulation transmit architecture with direct modulation of the VCO by a
fractional-N synthesizer. Both the RX and TX VCOs are fully integrated. The polar architecture
allows for a filter-free transmit lineup.

An on-chip transmit/receiver sequencer generates appropriate timing events for the transmitter
calibration and the EDGE/GMSK transmit/receive burst, therefore, limiting the RF hardware
dependency of the L1 engine software to an absolute minimum. The DigRF standard defines the

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digital interface between the TransAAM and the baseband processor IC.

3.4.2. Trans-AAM (U500)

Rx Analog Section
providing functionality for GSM850, EGSM900, DCS1800 and PCS1900 frequency bands. The
LNAs are differential and provide 30 dB of dynamic range as digital steps, eliminating the need for
RX AGC gain.

The quadrature mixer down-converts the RF signal to baseband. Passive differential and common
mode filtering at the mixer output limits out of band signals in the active stages of the baseband
section and results in an IP2 of 55 dBm (including processor gain). The I and Q analog baseband
signals are passed through low pass anti-aliasing filters and dc offset correction circuits before being
processed by the analog-to-digital converters.

-The RX architecture is digital VLIF/DCR. There are four separate LNAs

Figure 6. EGPRS transceiver - TransAAM and Orphee connections

TX Analog Section
VCO. The module can transmit in GMSK (phase modulation) or 8PSK (phase and amplitude
modulation) mode.

In GMSK mode, the dual port TX VCO is phase modulated by the dual port synthesizer and the
signal is fed to the PA input at a fixed level.

In 8PSK mode, the additional amplitude modulation is performed via a commuting switch mixer. The
mixer core drives a resistive digital step attenuator, which provides 0 to 45 dB of dynamic range in 3
dB steps, allowing the required full dynamic range to cover all EDGE power steps with only 20 dB of
dynamic range from the modulator. Two DACs provide signals to the modulator. One DAC is
dedicated to the amplitude component of the 8PSK wave form and the other to driving the VCO high
port input.

Frequency Generation
resonators with 32 states of digital course tuning. The frequency synthesizer is a 24-bit, 3rd order
fractional N synthesizer with digital AFC and a lock time of less than 80 µs. A 26 MHz crystal
oscillator provides a stable frequency reference. The VCO output signal runs through a

- The TX architecture is a polar modulator with direct digital modulation of the

- Both the RX and TX VCO run at 3296 to 3820 MHz and have integrated

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