High-Frequency Semiconductor Devices for Mobile Phones
74
High-Frequency Semiconductor Devices for Mobile Phones
Chushiro Kusano
Tetsuaki Adachi
Takefumi Endo
Shigeyuki Sudo
OVERVIEW: The dissemination of mobile phones is proceeding at a rapid
pace throughout the world. This trend has been driven by smaller size and
lighter weight, and by the much lower price that has become possible because
of technological innovation in components—especially semiconductors.
Achieving smaller size, lighter weight, lower price, and longer talk-time
are unchangeable propositions, and even now technological innovation
proceeds step by step. At present the progress being made in bringing higher
functionality to mobile phones is leading to an increase in components
including semiconductors. This in turn tends to cause an increase in power
consumption. Also, to increase convenience of use, dual-band types and
dual-mode types are being implemented, decreasing the space available for
those components. This further increases requirements that semiconductors
become smaller, thinner, and operate with lower power consumption. Hitachi,
Ltd. has responded to these needs by developing and producing a variety of
high-frequency semiconductor devices for mobile phones. These include
power amplifiers with high efficiency and low power consumption, GaAs
microwave monolithic ICs (MMIC) that can be densely integrated and
bipolar complementary metal-oxide semiconductor (Bi-CMOS) analog
signal processing ICs for dual-band operation.
INTRODUCTION
REQUIREMENTS for mobile phones, which enable
anyone to communicate anytime at anyplace, include
small size, light weight, and long talk-time. Smaller
size and lighter weight can be implemented by
integrating semiconductors more densely and using
smaller packages. Long talk-time has been made
possible by the higher efficiency and performance of
semiconductors, which results in longer battery life.
In this paper we will discuss mobile phone systems
(a) Si-MOSFET dual-band
high-frequency power
amplifier module
Fig. 1—Principal High-Frequency
Semiconductors for Mobile Phones.
Three dual-band circuits were developed
and are now being produced. The compactly
designed dual-band high-frequency power
amplifier module features a small package
and high efficiency in each band. The dualband receiver section is a composite GaAs
MMIC consisting of a low-noise amplifier,
mixer circuits, and local oscillator amplifier
with on-chip input and output matching
circuits in a small surface-mount package.
The dual-band high-frequency analog signal
processing IC incorporates most of the
required high-frequency receiver and
transmitter analog functions implemented
on-chip in a small package.
(c) GaAs MMIC low-noise amplifier,
mixer circuit, and local-oscillator amplifier
(b) Bi-CMOS dual-band high frequency analog signal processing IC
MOSFET: metal-oxide semiconductor field-effect
transistor
Hitachi Review Vol. 48 (1999), No. 2
trends and requirements. We will also describe the high
efficiency, high performance, and high-integration
technology of high frequency semiconductor devices
developed by Hitachi together with the outlook for
the future.
SYSTEM TRENDS AND REQUIREMENTS
Mobile phones are undergoing a generation change
from the analog types that were called the first
generation to the second generation digital types that
have become predominant. The principal second
generation communications systems are shown in
Table 1.
Conversations cannot be carried out between
mobile phones using different communications
systems. Thus, for convenience, manufacturers are
making dual mode types - code division multiple
access (CDMA) and Advanced Mobile Phone Service
(AMPS), etc.; and dual band types - Global System
for Mobile Communications (GSM) and Digital
Cellular System 1800 (DCS-1800), etc.
The communications area of mobile phones is
confined to within a limited area on land, but systems
such as Iridium using low earth-orbit communications
satellites circling the earth will provide seamless
75
worldwide communications so that conversations will
be possible at anyplace with a single mobile phone.
If one uses a dual-mode mobile phone, one can
change the mode of operation to utilize satellite service
when in an area beyond the reach of terrestrial signals.
These services feature the use of low earth orbit
circling satellites: thus the distance to the earth is small,
the propagation delay time of the radio waves is short,
and the delay of the other party’s voice is small enough
not to be noticeable. The next generation mobile
phone, which will be the third generation, will provide
multimedia services. Moreover the International
Telecommunication Union (ITU) aims to introduce in
the year 2001 the IMT-2000 digital communications
system that will make worldwide roaming possible.
Dual-mode mobile phones are under consideration to
promote coordination with current systems, and even
triple mode types are also a possibility. Trends of the
various generations are shown in Fig. 2.
Considering these trends, requirements for high
frequency semiconductors include even smaller
packages occupying less volume inside mobile phones
for dual-band systems, higher integration to realize
space saving, higher efficiency for longer battery life,
more precise modulation characteristics to improve
TABLE 1. Principal Communication Systems for Digital Mobile Phones
PDC is used in Japan, GSM has its hub in Europe but extends to a total of more than 100 countries,
and N-CDMA is used in Asia including Japan, and in the US. W-CDMA has been proposed by Japan
as a candidate for IMT-2000.
Communication
system
GSM
Frequency band
800 MHz/1.5 GHz
900 MHz
800 MHz
2 GHz
Channel spacing
25 kHz (alternate allocation)
200 kHz
1.25 MHz
5 MHz
Transmitting power
0.8 – 3 W
0.8 – 20 W
0.2 – 6.3 W
0.01 – 2 W
Frequency between
carriers
130 MHz (800 MHz)
48 MHz (1.5 GHz)
45 MHz
45 MHz
190 MHz
9.6 – 28.8 kbit/s
14.4 kbit/s
9.6 – 64 kbit/s
16 k – 2 Mbit/s
42 kbit/s
270.833 kbit/s
1.2288 Mchip/s spreading
(For example: 4.096 Mchip/s)*1
spreading
TDMA/FDD
TDMA/FDD
CDMA/FDD
CDMA/FDD, TDD
3 (6)
8 (16)
55
(256)*2
User data rate
Signal transfer rate
Access method
Voice channels per carrier
N-CDMA (IS95)
W-CDMA
(IMT-2000)
PDC
Item
Modulation method
4-phase shift QPSK
GMSK
OQPS/QPSK
BPSK/QPSK
Voice coding method
VSELP/11.2 kbit/s
(PSI-CELP/5.6 kbit/s)
RPE-LTP/13 kbit/s
EVRC/8 kbit/s
also/13 kbit/s
(For example: CSA-CELP)
PDC: personal digital cellular telecommunication system
N-CDMA: narrowband code division multiple access
IS-95: Interim Standard 95
W-CDMA: wideband CDMA
IMT-2000: International Mobile Telecommunication 2000
TDMA: time division multiple access
FDD : frequency division duplex
TDD: time division duplex
QPSK: quadrature phase shift keying
GMSK: gaussian filtered minimum shift keying
OQPSK: offset QPSK
VSELP: vector-sum excited linear prediction coding
PSI-CELP: pitch synchronous innovation code-excited linear prediction
RPE-LTP: regular pulse excitation with long-term prediction
EVRC: enhanced variable bit rate coder CSA-CELP: conjugate structure algebraic code-excited linear prediction
*1: 1.024 M/4.096 M/8.192 M/16.384 M are available; maximum user data rate at 4.096 M is 2 Mbit/s
*2: 4.096 spreading @ 16 kbit/s channel
US Europe Japan
Cellular
High-Frequency Semiconductor Devices for Mobile Phones
Small-zone
system
PDC
N-COMA
J-TACS
AMPS
USDC
TACS
GSM
R1
interface
IMT-2000
UMTS
(2 Mbit/s)
US Europe Japan
Cordless
NMT
R2
interface
PHS
PCS
DECT
CT-2*
First generation
(analog)
1985
DCS-1800
Second generation
(digital)
1990
1995
R3
interface
(satellite)
Unification of
all interfaces
1999
Third generation
(mobile telephone
unification)
2001
Year
76
J-TACS: Japanese total access
communication system
NMT: Nordic mobile telephone
PDC: personal digital cellular telecommunication system
USDC: US digital cellular
PHS: personal handyphone system
PCS: personal communication system
DECT: digital European cordless telephone
FPLMTS: future public land mobile
telecommunications system
R1: radio interface between a mobile station
and the base station
R2: radio interface between a personal station
and the personal base station
R3: radio interface between a satellite and
a mobile earth station
UMTS: universal mobile telecommunication
system
* Originating-only cordless telephone
developed in Europe
Fig. 2—Mobile Phone Trends and Forecast.
At present second-generation digital phones have become predominant. The International
Telecommunications Union (ITU) is promoting the introduction of IMT-2000 communications system
mobile phones that can be used anyplace on the Earth.
communications quality, and better linearity for lower
distortion amplification. We will describe the
technologies and products developed by Hitachi to
fulfill these needs.
TOWARD HIGH EFFICIENCY AND HIGH
PERFORMANCE
Si-MOSFET Dual Band (GSM/DCS-1800) HighFrequency Power Amplifier
The aim of a dual-band terminal is to improve the
convenience of the user. To obtain acceptance by the
largest number of users it is necessary to approach as
close as possible to the size and price of a single-band
terminal. Thus it is imperative that the high frequency
components feature lower cost and smaller size.
The transmitter can easily be configured using two
single-band power amplifiers suitable for two-band
Output
(GSM)
Input
Output
(DCS)
Bias circuit
use, but this is not the best solution from the size and
price standpoint. If a single amplifier is used to amplify
two bands, then the size of the power amplifier alone
can be made small. But since the 2nd harmonic of the
GSM band is close to the DCS-1800 band, specially
designed components will be required for harmonic
filtering, and the overall cost will become expensive.
Hitachi developed the PF08103A small-size low-cost
dual-band high-frequency power amplifier module,
which uses shared amplifiers for the first and second
stages, but 2 separate final stages with operating
efficiency optimized for each band. Below it is called
“RF module.” A block diagram of the 3-stage dualband RF module is shown in Fig 3. The matching
circuits at the input and between the first and second
stages are matched for 2 frequencies, while the input
and output of the final stages are matched for their
VCTL
Vapc
H
L
Control
signal
L
H
Control
signal
L
L
< 0.2 V
Operating mode VCTL
Amplifier
GSM
transmission
Matching circuit
(single frequency) DCS 1800
transmission
Matching circuit
(dual frequency) Transmission
close down
Fig. 3—Block Diagram of Dual-Band RF Module.
Compactly configured with 1 input, 2 outputs, and internal circuits; and designed for high efficiency
in both bands. Controllability is enhanced with 1 control signal and 2 band-switching digital signals.
Hitachi Review Vol. 48 (1999), No. 2
60
f = 915 MHz
30
f = 1,785 MHz
50
f = 915 MHz
10
Efficiency
Output
power
0
40
f = 1,785 MHz
-10
30
-20
Efficiency (%)
Output power (dBm)
20
-30
Vdd = 4.8 V
VCTL = 2.0 V
VCTL = 0.3 V
TC = 25°C
-40
-50
-60
0.0
0.5
1.0
1.5
Vapc (V)
2.0
2.5
20
10
3.0
Fig. 4—Dual-Band RF Module Output and Efficiency
Characteristics.
Efficiencies realized for the two frequency-bands at the output
terminals are 50% for GSM and 40% for DCS-1800.
respective frequency. Selection of the operating mode
is done through external band-switching logic.
Active devices for the amplifier are highperformance MOSFETs fabricated with a fine-pattern
process. MOSFETs are easily controlled, have
excellent thermal stability, and are suitable for mass
production because they are based on a silicon process.
Characteristics of the Dual-Band RF Module
This amplifier is suitable for 2 bands: Extended
GSM (E-GSM) and DCS-1800. Output power at the
high-frequency terminal and efficiency dependence on
the control voltage are shown in Fig. 4, while principal
characteristics are shown in Table 2. Efficiency values
of 50% in the GSM band and 40% in the DCS-1800
band are achieved. Noise characteristics in the
receiving band are -138 dBm/Hz for E-GSM at f =
TABLE 2. Main Characteristics of “PF08103” Module
GSM covers E-GSM bands and high efficiency has been
achieved for each of the bands.
Item
Power output
Characteristics
E-GSM: 48% (standard)
Vdd = 4.8 V
Vapc = 3.0 V
Pin = 4.5 dBm
Po = 34.5 dBm
DCS-1800: 40% (standard)
Po = 31.5 dBm
E-GSM: 35.78 dBm (standard)
DCS-1800: 33.0 dBm (standard)
Efficiency
Package
Conditions
Surface-mounting type, 11 × 13.75 × 1.8 (mm)
925 MHz and -139 dBm/Hz for GSM at f = 935MHz.
Moreover, when operating in the GSM band, 2nd
harmonic leakage to the DCS-1800 port is held down
below -20dBm, decreasing the burden on the external
filter characteristics. A leadless multilayer ceramic
package is used enabling small size to be realized.
ACHIEVING HIGHER INTEGRATION
GaAs Microwave Monolithic ICs
Response to the rapid increase in demand for
mobile phones is causing an steadily increasing
demand for gallium arsenide (GaAs) compound
semiconductors - whose use is well advanced at high
frequencies because of their excellent high-frequency
characteristics, including high gain and low noise. An
important feature of GaAs devices is excellent active
device characteristics on a crystal substrate with semiinsulating properties. Thus the low-loss input/output
impedance matching circuits that are indispensable in
high frequency circuits can easily be formed on the
substrate. GaAs MMICs enable most peripheral
components to be fabricated on the chip. The wireless
section can be made smaller, with assembly and
adjustment eliminated—providing important
advantages not possible with silicon LSIs. Hitachi has
previously developed and produced a 1.9-MHz band
GaAs MMIC chip-set incorporating a low-noise lowdistortion GaAs FET and a spiral inductor fabricated
by thick-film Au plating technology 1, 2). Subsequently,
to meet the needs of mobile phones for rapid size
reduction, Hitachi succeeded in the development and
mass production of the HA22022 MMIC extremely
small low-noise amplifier in a small plastic package3) .
HA22022
LNA
HA22032
LNA+MIX+Lo
Receiving
circuits
Antenna
IF amplifier
Transmitreceive
switching
Transmitting
circuits
Lo
Frequency
synthesizer
Orthogonal
modulation
PA
LNA: low noise amplifier
MIX: mixer
Lo: local amplifier
Baseband section
40
77
MIX
PA: power amplifier
IF: intermediate frequency
Fig. 5—Block Diagram of Wireless Section of Mobile Phone.
With an aim to making the assembly area even smaller, we
developed the HA22032 Composite MMIC with LNA + MIX +
Lo and matching circuits on chip.
High-Frequency Semiconductor Devices for Mobile Phones
Bias
RF
circuit
filter 1,805 –
1,880 MHz
Conversion efficiency (dB)
2.5
27
26
2.0
25
24
23
1,400
1,450
1st mixer
CG: conversion gain
RF VCO
Switch
NF: noise figure
including the transmitter section.
Bi-CMOS Analog Signal Processing ICs
In urban areas there is increased demand for dualband phones to solve the shortage of channels,
resulting in a stronger desire for a higher level of
LC
filter
RF
SAW
filter
2nd mixer
I.Q
45 MHz
270 MHz
GSM:
1,150 – 1,185 MHz
PCN:
R×1 1,580–1,655 MHz
R×2 1,575–1,650 MHz
PGA
PL2
GSM: 540 MHz
PCN: 540 MHz
1,710 – 1,785 MHz
RF: radio frequency
PCN: personal computer network
LC: LC filter
I: I signal
880 – 915 MHz
Loop
filter
HD155121F
90°
shift
÷2
÷6
PCN:
270 MHz
GSM: 540 MHz
GSM: 270 MHz
PCN: 135 MHz
90°
shift
÷2
GSM: 270 MHz
PCN: 135 MHz
Phase
I•Q
comparator
modulator
TxVCO
1,710 – 1,785 MHz
LPF: low-pass filter
PLL: phase-locked loop
Tx: transmitter
Rx: receiver
PGA: power gain controlled amplifie
Q: Q signal
I
Q
Serial data
interface
HD155017T
LPF
PA module
880 – 915 MHz
demodulator
÷2
IFVCO
Dual synthesizer
1.5
1,600
1,550
Fig. 6—High-Frequency Characteristics of HA22032.
High-frequency characteristics achieved at 1.5 GHz are a
conversion efficiency of 26 dB and a noise figure of 2 dB.
RF
SAW
filter
Bias
circuit
1,500
Frequency (MHz)
PL1
LPF
28
Baseband block
RF
SAW
filter
3.0
Power supply voltage: 3 V
Input power: -30 dBm
Intermediate frequency: 130 MHz
Local oscillator input: -15 dBm
1st mixer
925 – 960 MHz
RF
filter
29
Noise figure (dB)
Now, to reduce size even more, Hitachi has developed
and mass-produced the HA22032 MMIC that
consolidates several receiver functions including lownoise amplifier, receiving mixer, and local oscillator
amplifier together input/output matching circuits as
shown in Fig. 5. Moreover the surface mount package
used is an 8-pin thin small outline package (TSSOP)
measuring only 6.4 × 3 mm.
The high-frequency characteristics of the HA22032
are shown in Fig. 6. When operating at 1.5GHz, the
dual-gate metal-semiconductor FET (MESFET) with
gate lengths of 0.4 µm provides high-gain and lownoise characteristics with a conversion gain of 26 dB,
and a noise figure of 2 dB. For the same conditions,
the third-order intercept point is 4 dBm, which
provides excellent distortion characteristics. Use of this
MMIC makes possible a size reduction to 1/2,
including peripheral components, compared with
previous Hitachi products.
In the future we will have to respond to mobile
phone system requirements for multiplexing and even
smaller size. Thus we believe that it will be necessary
to produce highly integrated and multifunctional
MMICs not only for the receiver section but also
78
SAW: surface acoustic wave
VCO: voltage-controlled oscillator
Fig. 7—Block Diagram of HD155121F.
This chip integrates most of the analog section of dual-band mobile phones. Since it uses the same
LQFP 48-pin package as the previously developed single-band IC, assembly area is greatly reduced.
I
Q
Hitachi Review Vol. 48 (1999), No. 2
integration of the high-frequency signal processing
section. Hitachi has already developed and produced
single band ICs: HD155101BF for GSM4) and
HD155111F for DCS-1800. These devices can be used
in a dual-band phone, but the assembly area and power
consumption will become large. Therefore Hitachi
cooperated with TTP Communications Ltd of England
to develop and produce a single chip that integrates
GSM/DCS-1800 dual-band transmitting and receiving
sections, the HD155121F high-frequency analog signal
processing chip.
Configuration of the HD155121F
This IC uses the same 0.6-µm bipolar
complementary metal oxide semiconductor
(BiCMOS) process proven in single-band ICs, and has
on-chip the majority of functions required in the dualband transmitting and receiving high-frequency analog
section, as shown in Fig. 7. It operates on 58.6 mA
when receiving, 37 mA when transmitting. The
package is the same 48-pin, 9 × 9-mm low profile quad
flat package (LQFP) used for the single-band ICs, and
it realizes a reduction in assembly area.
79
propagation constant (V/A), and transmitter VCO
sensitivity (Hz/V). Since the frequency bandwidth of
GSM and DCS-1800 differs in the same manner as
the frequency bands, the VCO sensitivity as measured
in frequency change as a function of control voltage
also differs.
Because this IC uses a shared phase comparator,
loop filters with differing propagation constants would
be necessary to enable use of an offset PLL with a
fixed loop bandwidth. This requirement is avoided and
a fixed loop bandwidth made possible by a
configuration in which band selection and phase
comparator output current level are simultaneously
switched. Thus it is possible to use a shared filter, the
filter bandwidth can be fixed, and reduction in the
number of external components can be realized.
Other significantly advantageous characteristics are
as follows. Use of the offset PLL method for frequency
conversion results in a large reduction in out-of-band
noise in the transmitted signal. Elimination of the need
for a duplexer makes for a smaller assembly substrate
to help realize lower cost.
Evaluation results
Two separate groups of circuits are used for the
two frequency bands in the first mixer band, and
structured to convert the received signals to the
common intermediate frequency of 225 MHz. Thus
the second mixer and succeeding circuits have the same
structure as a single-band IC. Since operation at each
frequency band has the same form as in a single
frequency IC, users can utilize the same type of level
diagram design as for a single band IC.
Other characteristics are as follows.
(1) The negative-feedback bias circuit for the LNA is
included on the chip greatly reducing the number of
external components needed for the LNA.
(2) The first and second mixers have a 2-stage gainswitching facility.
(3) The digital-control variable-gain amplifier has 50
steps of 2 dB per step.
(4) I and Q (I signal and Q signal) demodulators have
an interference-signal suppression LPF on chip to
reduce assembly area.
Transmitting circuits
The bandwidth of the offset PLL circuit that
determines the transmitter output noise characteristics
and phase accuracy is dependent on the product of the
phase comparator output current (A/rad), loop filter
In addition to evaluating each block within the IC,
evaluation of the entire system including baseband was
carried out, and it was determined that the
specifications are fully satisfied. As an example,
receiver sensitivity characteristics of -106.3 dBm in
the GSM band and -106 dBm in the DCS-1800 band
are achieved, which provides more than adequate
margin with respect to the specifications, as shown in
Fig. 8.
4.5
4.0
3.5
RBER (%)
Receiving circuits
3.0
System specifications
GSM: Less than 2% at -102 dBm
DCS-1800: Less than 2% at -100 dBm
DCS-1800 specification
DCS-1800
2.5
2.0
1.5
GSM
specification
GSM
1.0
0.5
0
-108
-106
-104
-102
-100
Strength of received signal (dBm)
RBER: residual bit error rate
Fig. 8—RBER as a Function of Received Signal.
Received signal sensitivity specifications for both GSM and
DCS-1800 are exceeded.
High-Frequency Semiconductor Devices for Mobile Phones
Product plans
80
ABOUT THE AUTHORS
A 0.35-µm Bi-CMOS process triple-band IC is
currently being developed to respond to the demand
for even higher integra tion and lower power
consumption. This IC has a triple-band specification
to implement GSM, DCS-1800, and additionally
Personal Communications Services 1900 (PCS1900);
and our goal is to have both LNA and PLL synthesizers
on the same chip. We are also considering using this
technology as the basis for extending development to
W-CDMA and other systems.
CONCLUSIONS
We have described mobile phone systems trends,
requir ements, and work on high-frequency
semiconductor development ongoing at Hitachi. Highfrequency semiconductors greatly influence the
realization of mobile phones featuring smaller size,
lighter weight, and longer talk-time, and strong
demand exists for devices with higher efficiency,
higher performance, and higher integration. We expect
to continue our progress in developing high-frequency
semiconductors suitable for many types of
communications systems.
REFERENCES
(1) C. Kusano, et al., Low-Power and Low-Noise MicrowaveMonolithic IC (GaAs MMIC), The Hitachi Hyoron 75, (Apr.
1993) pp. 269–274, in Japanese
(2) I. Akitake, et al., Digital Devices for Mobile Communications
Terminals, The Hitachi Hyoron 78, (Oct. 1996) pp. 719–722,
in Japanese
(3) C. Kusano, et al., High-Frequency Semiconductor Devices for
Mobile Telecommunications Systems, The Hitachi Hyoron 78,
(Nov. 1996) pp. 757–762, in Japanese.
(4) High-Frequency Analog Signal Processing IC for Digital
Cellular Standard “GSM/EGSM”, The Hitachi Hyoron 79,
(Nov. 1997) pp. 885–890, in Japanese
Chushiro Kusano
Joined Hitachi, Ltd. in 1976, and now works at the
General Purpose Semiconductor Division,
Semiconductor & Integrated Circuits Group. He is
currently engaged in development and design of highfrequency compound semiconductor devices. Mr.
Kusano can be reached by e-mail at
kusano@cm.musashi.hitachi.co.jp
Tetsuaki Adachi
Joined Hitachi East Semiconductor, Ltd. in 1980, and
now works at the General Purpose Semiconductor
Division, Semiconductor & Integrated Circuits
Group. He is currently engaged in the development
and design of high-frequency power modules for
mobile phones.
Takefumi Endo
Joined Hitachi, Ltd. in 1986 and now works at the
Systems LSI Div., Systems LSI Division,
Semiconductor & Integrated Circuits Group. He is
currently engaged in the development of highfrequency ICs for GSM/DCS-1800 -based mobile
phones. Mr. Endo can be reached by e-mail at
endouta@cm.musashi.hitachi.co.jp
Shigeyuki Sudo
Joined Hitachi, Ltd. in 1986 and now works at the
Multimedia Systems R&D Division. He is currently
engaged in the development of LSIs for mobile
phones. Mr. Sudo can be reached by e-mail at
sudo@msrd.hitachi.co.jp