Low Profile ATSC
Digital Television Fractal Antennas
Without low profile fractal antennas designed for reliable
reception of ATSC 8VSB Digital Television (Widescreen HDTV) millions of
people in metropolitan (and rural) regions in North America will continue
to be without a reliable television service.
With the exception of some households that have been able to recycle their
Yagi-Uda antennas (VHF, UHF or Dual-band types) for reception of ATSC --
most North American households will continue to have television reception
quality far below what the 8VSB signal transmission system is capable of
Historically : NTSC, PAL or SECAM fadeout events generally are "long
duration" events due to the continuous wave nature of the traditional TV
transmission signal. These fadeout events were tolerable (or at least
interesting) to the traditional analogue television viewer.
ATSC 8VSB fadeout events in the digital television era are generally
catastrophic and random. These fadeout events alienate less technically
inclined television viewers, as the cause of reception failure is often
not obvious. Viewers in general expect digital television (regardless of
how it is transmitted) to be more reliable than analogue television. This
reliability has not yet been achieved.
Most 8VSB set top box decoders (as of the mid to late 2010s) only possess
"2nd generation" adaptive reception chipsets. These chipsets [and their
associated receiver subsystems] have on average only adequate sensitivity
to weak signals. These receivers possess only a limited ability to cope
with instantaneous fade out events. Longer duration fade out events are at
best "coped with" generally with variable degrees of success.
The most up to date 3rd and 4th generation 8VSB adaptive reception
chipsets often do not perform as optimally as their designers originally
hoped. There are a myriad of subtle (and gross) design and transmission
issues that these receivers must cope with that are beyond the ability of
a laboratory to simulate adequately.
Currently the ATSC HDTV viewer is left only with ongoing
frustration. Most 8VSB decoders uniformly fail to tell the viewer that the
received signal is unhealthy before a link loss event. Long duration fade
events (as with analogue television) don't really happen with 8VSB as the
digital television transmitters use 2/3rds to 1/3rd less power than their
previous analogue relative.
Essentially, fractal antennas are the only way to make 8VSB HDTV reception
reliable again, at the lowest possible cost to all parties involved.
If the antennas are designed properly, the need for antenna
amplifiers (for a large number of users) may also be mitigated.
Why the current ATSC antennas are
The 8VSB waveform is a "single carrier waveform" that is systemically
subject to the vagaries of Single Side Band (SSB) fading. SSB is the analog
waveform it is most closely related to 8VSB. SSB is used by PAL, SECAM and
NTSC -- the three existing TV broadcasting systems that have been around for
some 50 years.
Options that need to be considered
Why these options need to be
- Increasing the power of the 8VSB carrier wave (not
the overall transmitter power and not the 7% DC component inserted
into the 8VSB datastream) by 2db will probably not
substantially improve reception link margins. Increasing carrier wave
power could at best help to improve link margins by 1.25db under ideal
conditions. This signal modification would require replacing current
modulators. This means having to recalibrate existing transmitters, not
to mention testing the modification out to see if it actually works at
all. Increasing carrier wave power is not an ideal option at this time,
but it needs to be reconsidered as part of a set of long run solutions
to improve 8VSB reception. No more than 2db carrier power increase is
necessary, but it will be mess to implement.
- The recently specified ATSC error correction subsystem's non-mandatory
status (in the US or Canada) is not available to help reception due to a
failure of leadership in the oversight of 8VSB. This backwardly
compatible subsystem is part of ATSC-E (E for Enhanced).
- Making the updated ATSC Error Correction data stream mandatory (for
transmission and decoders) by 2010 would help, but this would not help
- There has been a systemic failure in terms of implementing in the body
of broadcasting regulation a secondary psudorandom anti fading sequence
for ATSC. This long run sequence anti fading sequence came into effect
with the coming of the updated ATSC standard. This backwardly compatible
subsystem is part of ATSC-E (E for Enhanced).
- ATSC already supports a 24 ms anti fading sequence, but it is not
suitable for combating long run (30 ms .... 3000 ms) fading effects.
Making the updated ATSC secondary anti fading sequence mandatory by 2010
would help, but existing receivers would be left out in the cold.
Recovering a clock signal in order to decode a received waveform has always
been a tricky proposition in digital RF communications. If we derive the
receiver clock from the recovered data, we have a sort of "chicken and egg"
dilemma. The data must be sampled by the receiver clock in order to be
accurately recovered. The receiver clock itself must be generated from
accurately recovered data. The resulting clocking system quickly "crashes"
when the noise or interference level rises to a point that significant data
errors are received.
When NTSC (and PAL) were invented, the need was recognized to have a
powerful sync pulse that rose above the rest of the RF modulation envelope.
In this way, the receiver synchronization circuits could still "home in" on
the sync pulses and maintain the correct picture framing -- even if the
contents of the picture were a bit snowy. NTSC (and PAL) also benefited from
a large residual visual carrier (caused by the DC component of the
modulating video). This residual carrier helped TV receiver tuners zero in
on the transmitted carrier center frequency.
The 8VSB transmission system employs a similar strategy of sync pulses and
residual carriers that allows the receiver to "lock" onto the incoming
signal and begin decoding, even in the presence of heavy ghosting and high
noise levels. The first "helper" signal is the ATSC pilot. Just before
modulation, a small DC shift is applied to the 8VSB baseband signal (which
was previously centered about zero volts with no DC component). This causes
a small residual carrier to appear at the zero frequency point of the
resulting modulated spectrum. This is the ATSC pilot. This gives the RF PLL
circuits in the 8VSB receiver something to lock onto that is independent of
the data being transmitted.
Although similar in nature, the ATSC pilot is much smaller than the NTSC
visual carrier, consuming only 0.3 dB or 7 percent of the transmitted power.
With NTSC, PAL and SECAM on average 50% of
the transmitter power went into transmitting sync pulses.
For DVB-T and ISDB transmission
technologies, there is no need to use a fractal antenna
DVB-T and ISDB are both multicarrier waveforms, thus there is no need to use
a fractal antenna to receive them. Also, both have configurable error
correction and configurable data rates that allow the bandwidth to be
matched precisely to the content that needs to be transmitted -- in a way
that is most error resilient.
Thus there is no need [at this point in time] for European Union (or
more specifically European Broadcasting Union), ASEAN or Japanese (or
Brazilian) consumers to get new TV antennas.
Ultimately it is up to the
consumer to use a better antenna
While most businesses (and more commonly home owners) can install Log
Periodic "LP " antennas (typically in Horizontal polarization, in the
Yagi-Uda family of antennas), many apartment dwellers as well as condo
dwellers don't have access to mounting an outside antenna for legal or space
It must be noted that the LP antenna type itself a kind of lesser fractal,
so one could in essence argue that fractal antennas have proven themselves
in the television reception area for some 50 years.
A low profile antenna is needed that can fit inside people's flats that
itself is not visible, but can provide link margins similar to the existing
LP antennas used on people's rooftops. So another kind of fractal antenna
must therefore be used. Any kind of fractal antenna would probably be better
than the standard dipoles (and "rabbit ears" antennas for UHF) that are
associated with current TV sets in North America.
Catastrophic 8VSB fading events are caused by the loss of "carrier lock"
coupled with a loss of the inserted "DC" component (mandatory at 7%, by
specification) causing a partial or total loss of the PLL lock on the
Fractal antennas needed here as no
other workable solution is available
In order to compensate against the loss of "carrier lock" (and the DC
component lock), your antenna must get bigger -- classical antenna theory
for all practical purposes dictates this for single carrier wave reception.
A large antenna surface area (and an antenna that is multiply resonant)
seems to be the only viable way to achieve reliable SSB or 8VSB reception.
Fractal antennas (even some the smallest ones) have relatively large surface
areas by default. Fractal antennas also can have the ability to intercept
polarized electromagnetic waves in a superior manner to the dipoles that are
in common use, at least when it comes to concentrating and channeling
incoming electromagnetic energy.
Important design considerations drawn from fractal antenna research (not
organized for content)
- When the number of Iterated Fractal Structure (IFS) iterations
increases beyond a certain threshold, the change in radiation patterns
and input impedance of the antenna tends to zero. In other words, there
is no use in increasing the number of IFS iterations after iteration
'x', due to no further advantage being gained in terms of antenna
efficiency. Convergence is usually achieved between 4 and 6 iterations.
This value depends largely on the size, wire radius or strip width and
topology of the antenna as well as the antenna's target frequency bands.
- The increase of fractal dimension, although making better space
filling curves, builds larger monopoles with lower efficiencies and
higher quality factors even for the first iterations, at least for wire
structures without loops.
- Topology has a stronger influence than fractal dimension on the
electromagnetic behavior of planar pre-fractal wire monopoles, in
particular on their respective losses efficiency factor.
- When the wire geometry contains no loops, each IFS iteration increases
the length and bending of the wires: as a consequence ohmic losses and
the amount of stored energy on the surrounding of the antenna increases
(this means lower radiation efficiencies and higher quality factors).
While the ratios of miniaturization can be remarkable, the achieved
efficiencies and quality factors are not that practical. The low
radiation resistances are due to the presence of anti-parallel currents
that cancel the radiation of each other. The antenna must be designed or
tapped in such a way as to minimize this problem.
- Wire geometries containing loops do not have anti-parallel currents.
Although they do not achieve a large degree of miniaturization, as the
number of loops inside the structure increases, efficiency and
fractional bandwidth (inverse of quality factor) seem to increase with
the order of the pre-fractal (number of IFS iterations).
- It has been observed that radiation resistance results are dependent
on the length of the feeding segment of the monopole, which seems to be
the main source of radiation, while the rest of the structure behaves as
a capacitive load that reduces the resonant frequency.
- The hypothesis of electromagnetic coupling (or shortcuts) between
corners fully explains why the resonant frequency of pre-fractal
antennas is much larger than what could be expected from the wire length
only, and why it stagnates as the number of IFS iterations increases.
The antenna must be designed or tapped in such a way as to minimize this
- As a result of the electromagnetic coupling hypothesis, some
guidelines for the design of small antennas have been derived. An
antenna design that follows these guidelines, the two-arm spiral
antenna, has the smallest possible size for a given resonant frequency.
- The design of wire small antennas using pre-fractal geometries has the
advantage of using an easily programmable IFS algorithm to pack a long
wire into a given volume. However, the mere fact of being a pre-fractal
object does not imply that the degree of miniaturization and antenna
parameters are optimum.
- As in any other kind of antenna, it is in fact the antenna geometry
what determines the radiation behaviour. The previous conception that
“fractal antenna” is equivalent to “optimum miniaturization and
bandwidth” is perhaps a misunderstanding of the well-known Hansen’s
statement: “To obtain performance closer to the minimum (Quality) "Q"
curve the spherical volume must be used more effectively”.
- Some pre-fractal antennas have a slightly smaller electrical size than
its conventional counterparts while maintaining their main radiation
parameters (quality factor and loss efficiency). This has been assessed
for planar monopole configurations, but other fractal antenna types are
still being accessed.
- It may be wise to mix different kinds of fractal antennas and feeder
structures to obtain an antenna with maximal efficiency.
- It may be wise to heavily tap some kinds of fractal antenna structures
to minimize reverse currents that decrease antenna efficiency.
Ideally this kind of fractal antenna should
be mountable on a vertical Venetian track blind. A window blind is
a window covering composed of long strips of fabric or rigid material.
Examples include shutters, Venetian blinds, roller shades and curtain-like
track blinds. A blind limits outside observation and thus “blinds” the
observer to the view. The main types are slat blinds which can be opened in
two ways and solid blinds.
structure ("Concatenated Horizontal H trees")
replicated vertically equal 150 cm height
each subunit being about 6 cm2
each antenna sub element minimum size should be 0.8 mm
each antenna sub element minimum size should be 1.6
each antenna sub element increment step should be 0.2 mm
|Illustrated above :
Manufactured fractal antennas with target fractal dimension ~1.58
compared with the size of 10 euro cents. All antennas are assumed to
be tapped at the bottom vertex or valley of the "V".
From Left to Right and by columns :
- Delta-Wired Sierpinski monopoles (DWS); Y-Wired Sierpinski
monopoles (YWS); Sierpinski Arrowhead monopoles (SA); and
Koch-1 Sierpinski monopoles (K1S).
- Note: Each step down each column is the next fractal antenna
iteration, from 1 to 5.
Intellectual property issues
Because of the complexity of "fine tuning" antennas for optimal broadband
performance (as TV antennas mainly operate below 1.0 GHz), it can be broadly
agreed upon that fractal antennas [that are designed to operate in the VHF
& UHF TV bands] should be patentable.
This "patentability context" should only apply to getting multiple types of
fractal antennas integrated (and optimized) onto a planar surface, with
applicable control mechanisms to reduce consumer annoyance with the antenna
However, for fractal antennas operating from 90 MHz to 900 MHz
- this "patentability rule" should not apply unless there is a
profound issue of miniaturization involved (an antenna size
reduction of at least ~100:1, per targeted wavelength bands).
- this "patentability rule" should not apply where the antenna is
otherwise simple AND is designed for NON-PROFESSIONAL USE.
Entities with "Fractal Antenna Patents"
People do have the right to take existing fractal antenna designs and
create their own distinct designs -- providing that the design shows
either distinct intellectual or artistic effort. This is not only to keep
costs down for the consumer, but to allow for innovation in design. In some
nations, artistic designs are copyrightable -- but this should legal context
should not be abused by antenna designers to artificially create a design
As fractal antennas only mere imitations of nature, there needs to be a
limit the extent that any fractal antenna can be patented or copyrighted.
- Most importantly of all : the antenna's bandwidth, gain,
selectivity and efficiency should be fully disclosed to the consumer.
Further technical reading
General DTV transmission technologies
modulation (the parent waveform of NTSC, PAL and SECAM as well as
- 8VSB (the transmission
waveform that is problematic due to it being a single carrier wave
antennas (the kind of antenna that can reduce 80% of the impact of
8VSB fade events)
Video Broadcasting (DVB the core standard that the ATSC
terrestrial television (the general category for terrestrial HDTV
- ATSC Standards
(the core HDTV transmission standards implemented in North America)
- ATSC tuner (the
device affected by poor antenna performance)
- E-VSB (the standard
for transmission and reception that the FCC and CRTC has failed to make
frequency-division multiplexing (the basis of DVB-T, ISDB (SBTVD)
- ISDB (transmission
standard adopted by Japan, after technical rejection of DVB-T)
(transmission standard to be adopted by Brazil, based on ISDB)
- DVB-T (transmission
standard adopted by the EBU after technical rejection of 8VSB; MPEG2 is
the default video type)
- DVB-T2 (the
successor to DVB-T, for digital terrestrial television)
- DVB_S2 (the
successor to DVB-T, for TVRO)
(transmission standard based on DVB-T, after rejection of some weak
points in DVB-T standard)
Fractals general information
- MPEG-4 SLS (not
implemented in DTV, but all DTV audio is MPEG-4 aka AAC)
- Bitrate peeling
(not implemented in DTV)
stream (the MPEG datastream that is damaged by poor antenna
- MPEG-2 (the MPEG-2
video datastream that depends on the MPEG Transport Stream to operate)
- MPEG-4 (some DVB
countries use MPEG2 or MPEG4 or both, SBTVD is MPEG4 only)
Antenna system issues
- Fractal antenna
(general technology category)
(antenna theory overall suggests that this shape is highly optimal for
reception of Horizontal or Vertical polarized signals)
carpet (in a modified form is used to make broadband mobile
- Hexaflake (has
been used to make experimental antennas, a 7 sided polygon could yield
Antenna (a technology needed in the construction of these antennas)
- Spurline & Stripline (are
related structural technologies needed and necessary in the
construction and manufacture of fractal antennas)
- Signal trace
(the kind of technology that can be used to make fractal antennas that
could be mounted on window blinds)
- Antenna Polarization
(general electromagnetic theory)
polarization (Most broadcasters in North America use
transmission antennas that are 60% Horizontally polarized, 40%
Vertical polarized -- this polarization ratio gives the best
performance for most in home television antennas. Low power relay
antennas (under 2 kw) may be polarized in "Horizontal" or "Vertical"
polarization (the kind of antenna preferred for VHF
broadcasters, but is almost exclusively used for UHF Television
transmission in North America.)
- Very high
frequency (band used by DTV broadcasters, has some impulse noise
- Ultra high
frequency (band used exclusively in Europe for DTV broadcasting,
very low noise immunity in this band)
Antenna mounting areas
Regulators (North America, where ATSC 8VSB HDTV has been adopted)
- Window blind
(structure where this antenna should be mounted)
- Mini blind
(probably not suitable for fractal antennas)
Companies that produce fractal antennas
|15 June 2007
|25 June 2008
|23 March 2014 (Spelling)