Design and Implementation of Low-Price Business Card-Size Portable Digital TV Set through High Integration DVB-T Solution

Abstract

In this paper we provide a system design method to solve the problem of developing a miniaturized portable digital TV set. For such a portable device it is very important to reduce its power consumption and extend its operation time as its battery is the only power source in the system. The hardware circuitry, therefore, must be relatively compact to be in accord with the high integration of the system-on-chip (SOC) and the proper selection of key components. Not only miniaturization can be realized but also cost and power dissipation of the system can be decreased. Whether the implementation can be achieved also depends on antenna efficiency and DVB-T receiver performance. Therefore it is vital to select the right radio frequency architecture, which affects both the signal reception and the power consumption. Based on the demands mentioned above we have chosen single a conversion architecture for the receiver. Furthermore, our design has a better performance than earlier designs because of the use of a shielding case and the appropriate filtering of power ripples. We implement the built-in spiral antenna body by means of the printed circuit board which is low-cost, wideband, small-sized, low-profile, and omnidirectional. Moreover, a heat sink conducts the heat outward and prevents overheating, thus ensuring operational safety.

Full text

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IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, NOVEMBER 2007
Contributed Paper
Original manuscript received August 29, 2007
Revised manuscript received September 23, 2007 0098 3063/07/$20.00 © 2007 IEEE
1608
Design and Implementation of Low-Price Business Card-Size
Portable Digital TV Set through High Integration DVB-T Solution
Ying-Wen Bai and Ming-Huei Lin

Abstract — In this paper we provide a system design
method to solve the problem of developing a miniaturized
portable digital TV set. For such a portable device it is very
important to reduce its power consumption and extend its
operation time as its battery is the only power source in the
system. The hardware circuitry, therefore, must be relatively
compact to be in accord with the high integration of the
system-on-chip (SOC) and the proper selection of key
components. Not only miniaturization can be realized but also
cost and power dissipation of the system can be decreased.
Whether the implementation can be achieved also depends on
antenna efficiency and DVB-T receiver performance.
Therefore it is vital to select the right radio frequency
architecture, which affects both the signal reception and the
power consumption. Based on the demands mentioned above
we have chosen single a conversion architecture for the
receiver. Furthermore, our design has a better performance
than earlier designs because of the use of a shielding case and
the appropriate filtering of power ripples. We implement the
built-in spiral antenna body by means of the printed circuit
board which is low-cost, wideband, small-sized, low-profile,
and omnidirectional. Moreover, a heat sink conducts the heat
outward and prevents overheating, thus ensuring operational
safety1.

Index Terms — Digital Video Broadcasting - Terrestrial
(DVB-T), Portable Digital TV, Power Consumption, Spiral
Antenna, Receiver.
I. INTRODUCTION
After digitization had been introduced, TV broadcasting
little by little switched from traditional analog to digital
systems. Digital Video Broadcasting-Terrestrial (DVB-T) is
currently being deployed in many countries, and it is planned
to replace current analog broadcasting schemes in most parts
of the world [1]. DVB-T conquers the problems faced by
analog systems, such as poor signal reception due to terrain,
and hence provides TV content with better sound quality and
higher video resolution [2].
The DVB-T system provides a means of delivering the
MPEG-2 Transport Stream (TS) via a variety of transmission
media [3]. To provide a high data rate at an extremely low-bit
error rate (BER) for MPEG-2 video data transmission, coded
orthogonal frequency division multiplexing (COFDM)
technology has been adopted in DVB-T systems [4]. COFDM

1 Ying-Wen Bai is with the Department of Electronic Engineering, Fu Jen
Catholic University, Taipei, Taiwan, 242, R.O.C.(e-mail: bai@ee.fju.edu.tw).
Ming-Huei Lin is a graduate student of Fu Jen Catholic University, Taipei,
Taiwan, 242, R.O.C. (e-mail: lmhk1024@yahoo.com.tw).

realizes a massive high-speed data transfer through the
technique of carrier overlapping and narrowband orthogonal
signals. It is mainly used for its robustness against multipath
interference and for the full setup of a single frequency
network (SFN). The DVB-T system transfers data in a flexible
way, and in order to deal with different circumstances various
modulation schemes are available, for example QPSK, 16-
QAM and 64-QAM. Besides these schemes there are two
transmission modes, 2K and 8K, based on the OFDM
technique which uses different numbers of carriers [1].
DVB-T is capable of mobile reception, and similar
applications have appeared in various kinds of consumer
products [5]. However among those portable digital TV
products which are on the market at present many are beset by
a number of disadvantages like their excessive size and
weight, heavy weight, low resolution, poor reception and
unavailability of replacement batteries. Our digital TV
solution eliminates these many problems and provides an
alternative with low cost, high portability and outstanding
video quality. Our design fulfils the end user’s demand of
being able to watch TV at any time and becomes a consumer
e-product.
This paper is organized as follows. In Section II the design
flow of our portable digital TV is demonstrated by the concept
of the system design. An introduction to the hardware
architecture is given at the beginning of Section III, showing
some of the problems arising during the developing process,
such as, for instance, with the plan of the power source,
antenna design, DVB receiver and cooling solutions. Then the
system’s measurement, an analysis of the system’s
performance and a comparison of the system’s results with
those of other products on the market are depicted. The last
section presents our conclusions.
II. SYSTEM DESIGN
Fig. 1 shows the steps of the system design for the portable
digital TV, and some of the points which needed to be taken
into account at each step are as follows [6]:
A. Specifications
In the planning stage it uses necessary to formulate product
specifications conforming to the industrial regulations.
B. Hardware Design
During the hardware design stage, choosing components of
low cost, minimum size and low power was given high
priority. We planned and examined the hardware circuits
based on the specifications and component characteristics

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Y.-W. Bai and M.-H. Lin: Design and Implementation of Low-Price Business Card-Size Portable Digital TV Set through High Integration DVB-T Solution 1609
before drawing the schematics. Then we made an overall
inspection of the component properties before beginning the
PCB layout. Much attention was paid to electromagnetic
interference (EMI), electromagnetic compatibility (EMC),
ESD protection, DVB-T front-end performance and
impedance matching along the transmission line.
C. Function Test
During the function test stage all hardware functions and
defects were tested and reviewed, and we made every effort to
minimize any mistake in the design phase.
D. Thermal Issue
Long-term monitoring by infrared scanner was used and the
case temperature was recorded during the stage of solving
thermal issues. Our target was to reduce the temperature of the
exterior case to below 39 °C. A thermal meter was used to
probe the IC surface temperature.
E. Receiver Test
During the stage of measuring the receiver, the performance
of the DVB-T receiver was measured to meet the specification
requirements [1].
F. Antenna Test
We experimented with many different materials in the
antenna test stage. FR4 became the final candidate due to the
cost constraint. Then the antenna performance was examined
and analyzed.
G. Integration Test
During this stage, the integration of hardware and software
was tested and the measurements of EMI, EMC and the
verification of reliability and ESD protection were carried out.
H. Final Stage
During the final stage, after all uncertainties were settled,
our design was an accomplishment. A comparison was made
between our design and similar products.


Fig. 1. Flow chart of the integration design for the portable digital TV.
III. THE INTEGRATION DESIGN OF THE BUSINESS CARD-
SIZE PORTABLE DIGITAL TV
The system block diagram of the business card-size
portable digital TV is shown in Fig. 2 and consists of several
modules. The two basic parts of the portable digital TV
system are the baseband and the RF sections. The baseband
contains a DVB decoder, memory ICs, an IR receiver, power
supply, a keypad and voice circuits. The RF sections include
internal and external antenna and the DVB-T receiver which
is composed of the DVB-T tuner and the COFDM
demodulator.

EXT-ANT
RF_IN
INT-ANT
CCIR656
ADDRESS BUS
DATA BUS
DVB
DECODER
ADDRESS BUS
DATA BUS
I2C
KEYPAD
IR
SDRAM
DEMODULATOR
TUNER
MPEG
stream
I2C
DVB-T SIGNAL
EXT-ANT
2.5'' LTPS LCD
EEPROM
FLASH
Amplifier
OFDM
DAC
POWER
+3.0V
+1.8V
SUPPLY
+5V
+7V
TV OUT

Fig. 2. Block diagram of the portable digital TV system.

There are several major parts in our system as explained
below.
(1) DVB Decoder
The DVB decoder we have chosen is a single-chip digital
TV processor of high integration which includes MPEG A/V
decoder, MPEG transport de-multiplex processor, micro-
controller and TV encoder onto a chip, facilitating a cost-
effective solution for digital TV receivers.
(2) Receiver
The key members of this part are tuner, AGC circuit,
COFDM demodulator, SAW filter and VGLNA. This receiver
is designed to cover VHF channels from 170 MHz to 230
MHz and UHF channels from 470 MHz to 862 MHz.
(3) Antenna
To reduce volume, weight and cost while still maintaining a
high level of performance and functionality [7], our antenna
uses the microstrip type, unlike the rod antenna used by other
products. Spiral antennas are known for their ability to
maintain near-circular polarization, consistent gain and input
impedance over a wide bandwidth; therefore the spiral shape
has been adopted for the antenna design [8].
(4) Memory
Memory ICs include Flash, SDRAM and EEPROM. Flash
acts as the storage for system firmware, SDRAM provides
software programs with a temporary place to store the
computation data, and EEPROM memorizes the user’s
personal configuration.
(5) Display
The 2.5 inch display panel is made of Low Temperature
Poly Silicon (LTPS) LCD with a resolution of 960x240 dots.
This kind of LCD has the advantages of low profile, light
weight, low power consumption and high resolution [9].
(6) Audio
The key members of this part are DAC (digital-to-analog
converter), LPF (low pass filter) and audio power amplifier.
The DAC translates the demodulated DVB-T signal into the
analog audio output. The LPF which attenuates the noise

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IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, NOVEMBER 2007
1610
higher than 24.9 kHz has been applied before the amplifier.
The audio power amplifier of Class D type is highly efficient
and suitable for the application of low power portable
products [10].
(7) Power
The power system comprises DC/DC converters, charging
circuitry and a rechargeable Li-ion battery. There are four
voltage outputs (+7V, +5V, +3.3V and +1.8V) coming from
the DC/DC converters. The Li-ion battery pack has a capacity
of 1050mA/H.
(8) Keypad and IR
Six function keys are defined for system operation: the
Menu, Enter, Channel up, Channel down, Volume up and
Volume down. The IR receiver is responsible for receiving
remote control signals from the external TV. The TV output
terminal provides video compatible with PAL, NTSC and
SECAM formats.
A. The power plan of the Integration Design
Power consumption is an important factor in portable
digital TV design. The power plan in the integration design of
the portable digital TV is shown in Fig. 3. We have chosen the
high-efficiency DC/DC converters to provide the voltage
transformation. The power for the LCD panel backlight is
provided by the built-in regulator whose efficiency is as high
as 90%. Besides their efficient handling of power, the ICs
behind the regulators are energy saving components. As the
LCD is shut down while the TV out terminal is in use, the
total power can be controlled at under 2.6 watts, which is
much lower than that in current products on the market.

Charger
DC_5V
Battery
ON/OFF
DC_5V
+7V
MOS
FET
+5V
+1.8V
+3.3V
Backlight
DVB-T
Decoder
DVB-T RF
Receiver
Memory
LCD
Amplifier
(5V/1.5A)
Switch
Adapter
DC/DC
Converter
Fig. 3. The power plan of our design.

Table I shows the power analysis of each voltage source.

TABLE I
POWER CONSUMPTION ANALYSIS OF OUR DESIGN
Power Mode 1.8V 3.3V
Power
Consumption (W)

5V 7V Backlight
0.33 0.94 1.03 0.18 0.09
B. Antenna Design and Performance Measurement
The DVB signal uses low-frequency carriers and occupies a
wide bandwidth. Both of these factors place certain physical
constraints on the size and the gain of an antenna. However,
size and gain are both critical essentials of a portable TV
product, so the technique used to make a small-size and high-
gain antenna becomes a major focus of our design. In our case
the rod antenna would be a simple choice. Typically a dipole
antenna for a VHF/UHF band requires a resonant length of
about 40cm as a quarter of the electromagnetic wavelength in
a vacuum. This length, however, is too long for portable
equipment [11]. The length of a rod antenna can be adjusted
between high and low frequency, but this gives a portable TV
a bad look and causes inconvenience during operation.
Consequently a printed antenna reveals its advantages
compared to a rod antenna. It is light, low-profile, easy to
manufacture and can be mounted on any exterior. Thus we
have chosen the microstrip antenna for our design.
We have evaluated the geometry of both spiral and fractal
dipole. Compared with the fractal dipole, the spiral shape
provides a wider bandwidth at the same benchmark value of
gain and input impedance. The Smith charts within the desired
frequency span illustrate that the impedance of a spiral antenna
is more centralized than that of a fractal dipole antenna.
Moreover, as spiral antennae are nearly circular polarized and
simpler to develop, we have selected the Archimedean Two-
Wire Spiral Antenna as the built-in antenna body [12].
We have measured the parameters of Smith charts, return
loss and Voltage Standing Wave Ratio (VSWR) of our design.
The Smith charts are shown in Fig. 4. Our antenna presents a
more centralized contour than other products.

Fig. 4. The power plan of our design.

The test data of return loss and VSWR in Table II show that
the operational frequency of our antenna covers both VHF and
UHF bands.

TABLE II
RETURN LOSS AND VSWR OF OUR DESIGN
Frequency (MHz) 170 230
Return Loss (dB) -9.25 -8.92
VSWR (dB) 2.06 2.08

Although we underestimated the gain and radiation pattern
there is a certain tolerance present. Due to the relatively low
operation frequency for DVB-T, a larger size of the semi-
470
-12.2
1.67
680
-22.7
1.15
810
-23.9
1.42

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Y.-W. Bai and M.-H. Lin: Design and Implementation of Low-Price Business Card-Size Portable Digital TV Set through High Integration DVB-T Solution 1611
anechoic chamber is required for the field tests. However, as
the availability of such chambers is limited, we fixed the
measurements at the 5 points (754, 762, 778, 818 and 870
MHz) on the UHF band. The results are presented in Table III.
The data in Table III show that we have achieved a compact
size; an area of only 50x50mm2 is allowed for our antenna.
This physical limitation and the goal of full VHF/UHF
coverage have made our antenna more difficult to develop.
TABLE III
PEAK GAIN AND EFFICIENCY TEST RESULT OF OUR DESIGN
Frequency (MHz) 754
Peak Gain (dBi) -4.43
Efficiency (%) 8.931
762
-4.45
10.65
778
-4.18
10.57
818
-3.67
10.26
870
-4.93
7.65

C. Performance Measurement of the DVB-T Receiver
The RF architecture of the DVB-T receiver has to be
carefully surveyed since it directly affects receiver
performance and power consumption. The DVB-T standard
defines many requirements, such as noise figure (NF),
sensitivity, dynamic range, interference immunity, as well as a
frequency span of 800 MHz for VHF and UHF bands. The
choice of a proper receiver structure governs the amount of
components and the possibility of implementation. The single
conversion allows the design over a wide bandwidth to be
divided into 2 to 3 spectral sections and hence makes the
component specifications more relaxed and mass production
less expensive [13-14]. The block diagram of the DVB-T
receiver is presented in Fig. 5.

UHF PLL
UHF
Tracking
Filter
VHF
VGLNA
Tracking
Filter
LPF
RF IN
DVB-T
SIGNAL
SAW
Filter
IF AGC
DVB-T TUNER
PLL(36.167MHz)
Down
Mixer
VHF
VCO
UHF
VCO
VHF PLL
COFDM
Demodulator
MPEG
Stream

Fig. 5. Block diagram of the DVB-T receiver.

We have provided some verification items and test
procedures for receiver performance. The instrument we have
used is the R&S broadcast test system (SFU), and the setup is
shown in Fig. 6. The sensitivity and the multipath
susceptibility have been measured to ensure conformity with
the DVB-T regulations [1].

Power
Supply
I2C
Broadcast
Test System
Signal
Input
Test JIGPC
I2C
DUT

Fig. 6. Basic setup of measuring equipment for DVB-T receiver
performance.

(1) Performance with noise figure and sensitivity
To improve the sensitivity and the dynamic range of the
receiver we have chosen the low-noise and wide bandwidth
VGLNA as the first-stage amplifier to improve the sensitivity
of our system design.

OUT
IF OUT
IN
PLL
Control
Noise
Source
ANT IN
Power
Supply
DUT
Noise Figure
Meter

Fig. 7. Basic setup of measuring equipment for noise figure.

Fig. 7 shows the setup for noise figure measurement. Data
are taken at the 12 frequency points of 177.5, 205.5, 226.5,
474, 522, 594, 618, 690, 714, 794, 802 and 858 MHz, and the
results are shown in Fig. 8.

100 200 300400
Frequency (MHz)
500 600 700800900
3
3.5
4
4.5
5
5.5
6
6.5
7
NF (dB)
Noise Figure

Fig. 8. Measuring results for the noise figure.

Because the received signal strength varies with the
propagation distance, the system should be able to handle a
wide range of input power. The results from our
measurement show that as sensitivity of the receiver is -80
dBm and the saturation point is -20 dBm, its dynamic range
is 60 dBm. The setup for the sensitivity measurement is
shown in Fig. 9, and the configurations are Modulation=64-
QAM, FFT mode=8K, Code rate=7/8, Guard Interval=1/32,
C/N ratio=20 dB, Bandwidth=7 MHz (VHF band)/8 MHz
(UHF band) and Frequency=177.5, 205.5, 226.5, 474, 522,
594, 618, 690, 714, 794, 802 and 858 MHz. The sensitivity
obtained over the spectrum is shown in Fig. 9. This result
shows that our design not only meets the standard [1], but
is superior to both Products A and M, especially in regard
to the UHF band. This has been achieved by offering a
solid shielding and by flattening the power ripple of the
receiver.

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IEEE Transactions on Consumer Electronics, Vol. 53, No. 4, NOVEMBER 2007
1612
100200 300400500600700800900
-85
-80
-75
-70
-65
-60
Frequency (MHz)
Sensitivity (dBm)
Our design
Product M
Product A

Fig. 9. Measuring results of sensitivity.

(2) Performance with short delay echo and long delay echo
The influence of C/N ratio and multipath reflections is
difficult to ignore. Besides having the C/N ratio above the
threshold, the multipath noise must be effectively
eliminated, although the system still needs to be
functional under these circumstances. The equalizer
inside the receiver is responsible for the suppression of
multipath interference below a reasonable level. All
channels of the receiver should be able to receive DVB-T
signals with short and long delay echoes.
The power level of a DVB-T wanted signal has been
adjusted to -50 dBm. The digital television receiver should
be able to receive the broadcast signal with a C/N ratio of
22.5 dB or less in 64-QAM mode after the signal has been
mixed with the long delay echoes as in Table IV and with
the short delay echoes as in Table V. Apart from Tables IV
and V, the test conditions have been configured as follows.
Bandwidth=7 MHz (VHF band)/8 MHz (UHF band), FFT
mode=2K, Modulation=64-QAM, Code rate=7/8, Guard
Interval=1/32 and Frequency=177.5, 205.5, 226.5, 474,
522, 594, 618, 690, 714, 794, 802 and 858 MHz.

TABLE IV
LONG DELAY ECHO PARAMETERS
Path
1 2
Delay (uS) 0 5
Relative
Attenuation (dB)

TABLE V
SHORT DELAY ECHO PARAMETERS
Path
1 2
Delay (uS) 0 0.05
Relative
Attenuation (dB)

Fig. 10 demonstrates that the design conforms to the
regulation [1].

PathPath
3
14
Path
4
35
Path
5
54
Path
6
75
0 9 22 25 27 28

Path Path
3
0.4
Path
4
1.45
Path
5
2.3
Path
6
2.8
2.8 0 3.8 0.1 2.6 1.3
100200 300400
Frequency (MHz)
500600700 800900
17
18
19
20
21
22
23
Power level (dBm)
Long delay echo
Short delay echo

Fig. 10. Measuring results of short delay and long delay echo tolerance.

D. Thermal Issue of the Integration Design
Our DVB decoder IC was not designed for portable devices
in the first place. The limited area of a business card, as shown
in Fig. 12, turns heat control into a serious matter. The portion
of excess heat that is not well conducted will, in the long run,
deform the device’s structure and cause thermal run-away and
explosion in the Li-ion battery.
In the beginning low power components were selected to
minimize heat generation and a heat sink applied to conduct the
heat on to the surface of the device. Using a thermal meter we have
found out that the heat comes mainly from the DVB decoder
chipset and the DVB-T receiver. We have, therefore, separated the
locations of two parts during the PCB re-layout [15].
Powered by the DC adapter, the DUT when turned on,
broadcast TV shows for 24 hours. An IR scanner and a
thermal meter recorded the temperature variations throughout
the day. Fig. 11 illustrates that the case temperature is much
lower with the heat sink added than without a heat sink. The
highest temperature has been effectively reduced by 19%,
from 48 °C to 39 °C.


(a) (b)
Fig. 11. Thermal scan result of IR. (a) Original design. (b) With added
heat sink.

E. Experiment Results
Proper selection of the key components and the DVB-T
architecture have helped us to finish the integration of the portable
digital TV. A snapshot of our system is shown in Fig. 12.