USOO5774193A United States Patent (19) 11 Patent Number: 5,774, 193 Vaughan (45) Date of Patent: Jun. 30, 1998 54). DIGITAL TELEVISION (HDTV) AND Primary Examiner Benny T. Lee ANALOG TELEVISION (NTSC) BROADCAST Attorney, Agent, or Firm-Robert T. Dunn, Esq. SYSTEMS COMBINED FOR SIMULTANEOUS BROADCAST 57 ABSTRACT Inventor: Thomas J. Vaughan, P.O. Box 440, An HDTV broadcast transmission System and an analog Rye Beach, N.H. 03871 NTSC broadcast transmission system are carried on the Same tower and broadcast to the same area by adaptation of both systems: the NTSC system including: (a) a source of Appl. No.: 395,754 analog NTSC video signals, (b) an NTSC analog video Filed: Feb. 27, 1995 signal exciter producing NTSC IF modulated analog video Signals, (c) an NTSC frequency up converter and power Related U.S. Application Data amplifier producing NTSC RF modulated analog video signals (NTSC RF signals), (d) an NTSC broadcast antenna Continuation-in-part of Ser. No. 956,911, Oct. 5, 1992, and (e) an all band VHF and UHF signal transmission line abandoned. having an input end and an output end; the HDTV system Int. Cl." ........................... H01O 5700; H01P 1/213 including: (1) a Source of digital video signals, (2) a digital Video signal encoder producing IF modulated digital Video U.S. Cl. .......................... 348/723; 343/890; 333/134; Signals and (3) a frequency up converter and power amplifier 333/135; 333/202; 333/212 producing RF modulated digital video signals (HDTV RF Field of Search ..................................... 333/117, 126, signals) and an HDTV broadcast antenna; by combining the 333/129, 132, 134, 135, 202, 212; 343/890, HDTV RF signals and NTSC RF signals at the input end of 891; 348/723, 608, 487,470, 426, 21; 370/37, the transmission line and Separating them at the output end 38, 297, 308; 455/119, 129 and feeding them to the NTSC antenna and the HDTV References Cited antenna, respectively. In a preferred embodiment, the HDTV 56) antenna is supported on the tower below the NTSC antenna U.S. PATENT DOCUMENTS and the antennas radiation patterns cover Substantially over 2,853,681 9/1958 Smoll ...................................... 333/132 lapping broadcast reception areas around the tower. 5,291290 3/1994 Vaughan et al. ........................ 348/723 5,418,506 5/1995 Mahnad .................................. 333/134 22 Claims, 6 Drawing Sheets EXISTING VHF OR FM ANTENNA VHF OUTPUT UPPER OUO-BAND UHF COUPLER 1. 11 HDTV ANTENNA 16 21 UHF OUTPUT EXISTING COAX ENCODER TRANSMISSION LINE 10 NTSC EXCITER U.S. Patent Jun. 30, 1998 Sheet 1 of 6 5,774, 193 EXISTING VHF OR FM ANTENNA 8 VHF OUTPUT - UPPER DUO-BAND UHF COUPLER 1. 11 HDTV ANTENNA 16 21 UHF OUTPUT 20b HDTV EXISTING COAX ENCODER TRANSMISSION LINE 14 HDTV HDTV PASSBAND TRANSMITTER VIDEO FILTER 10 NTSC EXCITER FIG 1 U.S. Patent Jun. 30, 1998 Sheet 3 of 6 5,774, 193 U.S. Patent Jun. 30, 1998 Sheet 4 of 6 5,774, 193 HDTV RF NTSC RF POWER POWER AMPLIFER AMPLIFER U.S. Patent Jun. 30, 1998 Sheet 5 of 6 5,774, 193 11 N 21 (1. TRANSMITTER 14 15 N 1 RF 21ay 16 1 U.S. Patent Jun. 30, 1998 Sheet 6 of 6 5,774, 193 8a NTSC 21a low 10-N TOP MOUNTED FIG 12 8b NTSC p1 11 8c NTSC 10 N 21C HDTV TOP AND SIDE A- 10 MOUNTED TOP AND FIG 13 WRAP AROUND FIG 14 5,774,193 1 2 DIGITAL TELEVISION (HDTV) AND applicant has concluded that each broadcast Station should ANALOG TELEVISION (NTSC) BROADCAST and will try to use its present facility for the HDTV SYSTEMS COMBINED FOR SIMULTANEOUS broadcast. Although many NTSC antenna towers are wind BROADCAST load limited, it will be possible in many cases to re-enforce the tower so that it can also carry the HDTV transmission BACKGROUND OF THE INVENTION line and/or antenna. This is a Continuation-In-Part of the applicant’s aban Present Proposed Digital HDTV Systems doned U.S. patent application Ser. No. 07/956,911, filed Oct. 5, 1992 abn and entitled “High Definition Television Broad Several of the digital HDTV systems and their proponents cast System'. The present invention relates to high power C. broadcast Systems for broadcasting two channels of Substan Digicipher tially different radio frequency (RF) where the channel HDTV System broadcast antennas are on the same Support and fed by a General Instruments common transmission line. The invention has particular MIT 15 application to television broadcast Systems for Simulta DSC neously broadcasting digital high definition television (Digital Spectrum Comparable) HDTV System (HDTV) and analog national television standard code (NTSC) signals, as will be required in the United States by Zenith the Federal Communication Commission (FCC). AT&T The HDTV market is projected to be very large. If every ADTV NTSC television broadcast station (broadcaster) has to (Advance Digital TV) HDTV System Supplement it's existing NTSC transmitter, tower, transmis David Sarnoff Research Ct. (Sri) sion line and antenna with an HDTV system, the total cost Philips throughout the United States will be over two billion dollars. 25 Thomson This does not consider the cost and time it would take to find NBC a new tower Site. In addition, it is estimated that it will cost Compression Labs over twice that amount for HDTV cameras, video Switches These digital HDTV systems are all referred to herein as and a means of getting the Signal from the Studio to the HDTV systems and the term HDTV as used herein refers HDTV broadcast site. only to digital HDTV. The Digicipher, DSC and ADTV Simulcast Period HDTV systems have been tested and tests continue. Zenith and Thomson have both announced that they will have The new Advance TV Service is referred to as high receivers ready for whichever system is selected and will be definition television (HDTV). This new service will be a in full production the next year. digital System, have improved Video, be interactive and 35 The applicant has proposed that a broadcast Station's new more useful with multiple audio and data inputs. All oper digital HDTV broadcast transmission system and existing ating NTSC broadcast full service stations will be given first analog NTSC broadcast transmission System, that broadcast preference to the new HDTV channels. The present low to the same area during the Simulcast Period, be carried on power NTSC broadcast stations, sometimes called LPTV the same tower. The applicant's proposal is described in his stations, will have second preference to the new HDTV 40 above mentioned abandoned U.S. patent application Ser. No. channels. There are at present over 1,300 full service NTSC 07/956,911, from which the present application is a stations and over 1,200 low power television (LPTV) NTSC Continuation-In-Part. Furthermore, in the applicant's pend Stations. Studies show that if the Spacing between ing U.S. patent application Ser. No. 08/293,429, filed Aug. co-channel stations were reduced, all of the existing VHF 19, 1994, entitled “Digital Television (HDTV) And Analog and UHF broadcast station's new HDTV broadcast channels 45 Television (NTSC) Broadcast Systems On A Common can be accommodated in the UHF band. Tower For Simultaneous Broadcast', which is a Continua Because of the “Robustness” of digital transmission, a tion Application of Said abandoned U.S. patent application higher quality Video Signal can be delivered over the same Ser. No. 07/956,911, the applicant proposes that the HDTV geographical audience viewing area as presently reached by antenna be below the NTSC antenna on the tower and be a NTSC broadcasts, with less than 10% of the present NTSC 50 wrap around-type, multi-element antenna, comprised of a power. However, the new HDTV signal that is proposed is multitude of panels Spaced around the tower. not compatible with present day NTSC receivers. In said abandoned U.S. application Ser. No. 07/956,911, It is expected that each full service station will broadcast the applicant also proposes combining the HDTV and NTSC the same program Simultaneously on an NTSC channel and radio frequency (RF) Signals and feeding them to a common on an HDTV channel. In other words, a program that is 55 wide band transmission line that goes up the tower to a presently broadcast by NTSC signal will also be broadcast common wide band (all band) antenna that broadcasts both by HDTV signal over a new UHF channel that is to be HDTV and NTSC RF to the Station broadcast area. The allotted to the station. This Simulcast Period may last 15 major differences between the HDTV and the NTSC sys years, or until there are sufficient HDTV receivers in the temS are: Station's viewing area to allow the Station to broadcast only 60 The NTSC system quality is a function of signal level; the over the HDTV channel. Stronger the Signal, the better the quality. A plan proposed by the FCC is to allow a three year period The HDTV system signal quality, like all digital for each station to apply for an HDTV channel license and transmission, is not a function of Signal level. When the an additional two years for construction. Thereafter, the Signal is too low, it will disappear, hence, the So called station will transmit the NTSC program and the HDTV 65 “Cliff Effect. program for a period of up to 15 years, or until all of the Comparable signal levels based on 50/50 and 50/90 NTSC receivers are replaced with HDTV receivers. The propagation curves are as follows: 5,774,193 3 4 For the NTSC system it is 74 db-Grade A, and different RF signals are broadcast from different antennas, For the HDTV system it is 44 db-Equivalent Grade A.