Sponsors

Some of our projects are sponsored, or partly sponsored, by companies that include the following:

Elecard develops and provides video compression solutions, analyzers of media streams and compressed video bitstreams, and QoS & QoE probes for real-time video monitoring. Elecard MPEG-2, H.264/AVC, HEVC live encoders and MPEG-DASH/HLS packagers are in production with Tier 1/2/3 broadcasters, IPTV and OTT operators. VVC, HEVC, AV1, VP9, MPEG-2 and H.264/AVC video analyzers, monitoring probes, encoders and playback software enable system architects, SoC designers and QA to shorten development cycles and improve time to market. Elecard also creates bespoke software and hardware solutions to help your business thrive.

Elecard StreamEye Studio – video quality analysis software

Powerful and incredibly useful software tools to view and analyze syntax of encoded media streams, validating streams against ETSI TR 101 290 standard, computing quality metrics like VMAF, PSNR, SSIM, and others. HEVC, H.264/AVC, AV1, VP9, and MPEG-2 video formats are supported. VVC support coming soon.

Elecard Boro – IPTV, OTT, DVB monitoring probes

Multifunctional solution to monitor UDP, RTP, HTTP and HLS streams and measure a spectrum of QoS and QoE parameters with signaling on issues. A flexible software architecture concept allows integration with an already existing fault management system or creating your optimal monitoring solution tailored to your needs.

Elecard CodecWorks – live transcoding software

Software platform to encode and transcode in real-time mode into HEVC, H.264/AVC, and MPEG-2 video that outputs packaged HLS/DASH files for distribution.

For more information, please go to Elecard.


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IWT technology was developed to bring true interactivity to broadcast and wireless media.

For more information, please go to Interactive Wireless Technologies.

FCC Proposes to Reinstate Amateur Radio Service Fees

The FCC has proposed in an NPRM to impose license fees on Radio Amateurs.  I urge you to send your comments to the FCC arguing against the reinstatement of those license fees.

You may not be aware of the public good this service provides in times of emergency, as it has during the recent hurricanes.  The decrease of new applicants in recent years is not helped by this mercenary proposal.

You may also not know that amateur radio is often a leading developer of new technologies.  Just one example is the recent development of a low-cost vector network analyzer — the NanoVNA.  Originally developed by and for radio amateurs, this breakthrough device is now being used in the broadcast and other wireless industries, as written up by broadcast engineer Doug Lung in the last two issues of IEEE BTS Magazine and in TV Technology.

The NPRM can be found at FCC MD Docket No. 20-270Comments are due by November 16, 2020.

The ARRL will be filing comments, and their position can be found at this link; you may be interested to see my filed comments.

73’s,

Aldo, W2AGC

Modulation 101

Modulation is the process of imparting a signal, usually audio, video, or data, onto a high-frequency carrier, for the purpose of transmitting that signal over a distance.

Let’s take a carrier signal,  cos(ω_c t) and a modulating signal,  cos(ω_m t), where ω = 2 \pi f , and f is the signal frequency.

Amplitude modulation is simply the product of the carrier signal and (1 + modulating signal):

\displaystyle AM(t) = cos(ω_c t) \times [1 + cos(ω_m t)] ,

which multiplies out as: AM(t) = cos(ω_c t) + cos(ω_c t)\times cos(ω_m t) ] . A carrier modulated by a sine wave is shown in the following example.

Note that such a signal is relatively easy to demodulate: a simple rectifier and low-pass filter will recover the modulation from this signal, as you can visualize by “erasing” the negative portion of the signal and averaging over the remaining waveform.  Such a process is called envelope detection.

To analyze the composition of this signal, we take the trig product identity, cos(x)\,cos(y) = \frac{1}{2} [ cos(x-y)+cos(x+y) ], and apply it to the product term in AM(t), producing the following:

\displaystyle AM(t) = cos(ω_c t) + \frac{1}{2} cos(ω_c t - ω_m t) + \frac{1}{2} cos(ω_c t + ω_m t) .

From this, we observe an important aspect of the process:  amplitude modulation results in a signal composed of the following three components:

    1. the carrier signal, cos(ω_c t),
    2. a lower sideband signal, \frac{1}{2} cos(ω_c t - ω_m t),
    3. and an upper sideband signal, \frac{1}{2} cos(ω_c t + ω_m t).

By the way, the reason for the “1 + ” term in the modulation equation above is that it specifically generates the carrier component in the modulated signal. Without it, we would have the following Double-Sideband-Suppressed Carrier signal, which should make it apparent that we can’t use a simple envelope detector to demodulate; note how the envelope “crosses over” itself:

An analysis of modulation is aided by using a more complex modulating signal.  A ramp signal is comprised of a fundamental sinusoid and integer harmonics of that fundamental.  For illustration purposes, we will take an approximation that uses the fundamental and the next 8 harmonics. This modulating signal is shown below, as a function of time.

The spectrum of this signal, i.e., a plot of the frequency components versus level, is shown next; it consists of a fundamental (at “1”), followed by a series of harmonics with decreasing levels.

If we amplitude modulate a carrier with this ramp signal, we get the following time-varying signal; note again that this signal can be demodulated by an envelope detector:

The spectrum of the modulated ramp signal follows; note that there is a carrier at “0” and sidebands extending in both the positive and negative frequency directions. (In practice, this zero point would actually be at some high frequency, such as at 7 MHz for example. The spacing of the individual components in this example would be exactly that of the frequency of the fundamental component of the ramp signal.)

Recall from our earlier discussion that amplitude modulation results in a signal composed of the three components, the carrier signal, a lower sideband signal, and an upper sideband signal. Note the following as well: because the lower sideband component has a negative modulating-frequency term (cos(ω_c t - ω_m t), for a sine wave) the spectrum of the lower sideband is reversed compared with that of the upper sideband (and that of the baseband modulating signal).

We can also see from this example that amplitude modulation is rather wasteful of spectrum space, if our goal is to take up as little bandwidth as possible.  For one, the two sidebands are merely reflections of each other, i.e., each one carries the same information content.  For another, the carrier itself is unnecessary for the communication of the modulating signal as well — something that wastes power on the transmission side.

Taking that into account, we can choose to transmit only one sideband, resulting in a Single Sideband (SSB) Transmission. If we transmit only the lower sideband, its spectrum will look like this (note that the carrier is also absent):

SSB modulation can be implemented using a variety of methods, including an analog filter, or phase-shift network (PSN) quadrature modulation.  (For a clue as to how PSN works, look up and calculate the result of adding cos(x) cos(y) + sin(x) sin(y).)

The challenge in receiving this signal is how to demodulate it, as we can see from its time-domain plot:

As compared with amplitude modulation, a SSB signal cannot be demodulated with an envelope detector, because the envelope is no longer a faithful representation of the original signal.  One way to demodulate it is to frequency-shift the signal down to its original range of baseband frequencies, by using a product detector which mixes it with the output of a beat frequency oscillator (BFO).

One can appreciate that, if the demodulator BFO is not exactly at the original carrier frequency, the resulting demodulated signal will be frequency-shifted up or down by the amount of the error, resulting in a kind of “Donald Duck”-sounding voice signal.  While this was often an issue with analog transmitters and receivers, whose carrier frequencies were imprecise, and would drift over time, modern digital equipment is so accurate that a near-perfect re-synchronization is not difficult to achieve.

— agc

/ / /

Video Pioneers Remember Historic HDTV Debut

Grand Alliance Prototype

Twenty-five years ago this week, the world’s first HDTV broadcast system was unveiled in Las Vegas at the 1995 NAB Show.  AGC Systems’ Aldo Cugnini was there, as one of the many engineers who developed the “Grand Alliance” digital HDTV system.  Then at Philips, Aldo had a leadership role in the system’s development, which went on to become the ATSC digital television system.

Click here to see historic videos of the debut of HDTV.

Selected Papers

  • The Promise of Mobile DTV, NAB Broadcast Engineering Conference Proceedings, 2011.
  • A Revenue Model for Mobile DTV Service, NAB Broadcast Engineering Conference Proceedings, 2010.
  • Considerations for Digital Program Insertion of Multiple-Video Programs, NCTA Fall Technical Forum, 2002.
  • Digital Video and the National Information Infrastructure, Philips Journal of Research, Volume 50, Issues 1–2, 1996.
  • MPEG-2 video decoder for the digital HDTV Grand Alliance system, IEEE Transactions on Consumer Electronics, Vol. 41, Aug 1995.
  • Grand Alliance MPEG-2-based video decoder with parallel processing architecture, Intl. J. of Imaging Systems and Technology Vol. 5, No. 4, 1994.
  • The ISO/MPEG Audio Coding Standard, Widescreen Review, June/July, 1994.

NAB 2019 Conference Widely Featuring ATSC 3.0

More than 100 NAB Show sessions and more than 50 exhibitors will feature Next Gen TV technology that is now voluntarily spreading to cities throughout the country. Powered by the ATSC 3.0 next-generation broadcast standard, Next Gen TV promises to deliver sharper, more detailed pictures and lifelike multichannel audio with upgraded broadcasts that will be transmitted and received in the same Internet Protocol language as Internet-delivered content.

Jointly sponsored by the Advanced Television Systems Committee, the Consumer Technology Association and NAB, the “Ride the Road to ATSC 3.0” exhibit will be featuring a series of free presentations about all facets of the ATSC 3.0 standard. And attendees can pick up a free Guide to 3.0 at the Show in the Central Lobby of the Las Vegas Convention Center during the show.

Single Frequency Network Demonstrations

The NAB, with support from a number of technology companies, will demonstrate the Single Frequency Network (SFN) capabilities of the Next-Gen TV standard, showing how reception can be improved in difficult locations and in moving vehicles by deploying multiple broadcast towers transmitting the broadcast signal on the same channel.

Using several local transmissions, special SFN viewing kiosks will showcase the flexibility of the ATSC 3.0 standard. Dozens of sessions planned in the exhibit will include updates on the Dallas, Phoenix, Santa Barbara, East Lansing, Cleveland, and Korea ATSC 3.0 deployments.

Scores of papers and sessions will be presented about Next-Gen TV during the 2019 NAB Show, with session topics that will cover consumer research, consumer device plans, conformance testing, audio enhancements, station build-out advice, watermarking, advanced emergency information, channel security, advanced advertising and interactivity. In addition to ATSC, CTA and NAB, exhibit sponsors include Pearl TV, Sinclair Broadcast Group, LG Electronics, Dolby, Sony, Samsung and the AWARN Alliance. The centerpiece of the Ride the Road stage is a giant new LED videowall optimized for broadcast applications, provided by LG Business Solutions.

AGC Systems president Aldo Cugnini will be at the show, and available for discussions regarding support for ATSC and other related ventures. If you’d like to meet up, please contact us.

FCC Opens Up Spectrum Above 95 GHz

This month, the Federal Communications Commission allowed a plan to make the spectrum above 95 GHz more readily accessible for new innovative services and technologies. Calling the initiative “Spectrum Horizons Experimental Radio Licenses,” the plan is outlined in a First Report and Order, which allows a number of changes to existing rules, including:

  • a new category of experimental licenses, to increase opportunities for entities to develop new services and technologies from 95 GHz to 3 THz, with no limits on geography or technology; and
  • making 15.2 gigahertz of spectrum available for unlicensed use.

The Order specifically allows two types of operations:

  • A Spectrum Horizons experimental radio license can be issued for the purpose of testing and marketing devices on frequencies above 95 GHz, where there are no existing service rules.  Licenses are issued for a term of 10 years and may not be renewed.
  • Unlicensed operations are allowed in the bands 116-123 GHz, 174.8-182 GHz, 185-190 GHz, and 244-246 GHz, that are consistent with the rules proposed in the Spectrum Horizons, Notice of Proposed Rulemaking and Order.

Part 15 of the FCC Rules was also amended to extend operational limitations and interference measurements covering frequencies above 95 GHz.

The new rules provide that the Commission may, at any time without notice or hearing, modify or cancel a Spectrum Horizons License, if, in its discretion, the need for such action arises.  Some commenters raised the issue that this could result in an abuse of the complaint process, but the Commission pushed back, saying they “routinely work with parties to resolve potential or actual issues…”

The Commission withheld action on their proposal for licensed fixed point-to-point operations in a total of 102.2 gigahertz of spectrum, and opposed the concerns of the ham-radio organization ARRL regarding protection from interference.  In defending the latter position, the Commission states, “both the amateur radio service and the experimental licensing program are designed to contribute to the advancement of radio knowledge,” and goes on to say that “we will instead require all Spectrum Horizons License applicants to submit an interference analysis that would address the potential effects of the experimental operation on existing services.”  

In addition to Chairman Ajit Pai, the proposal has general support — albeit with certain cautions — from all four of the other commissioners, who evenly represent both sides of the political aisle. 

— agc