Tuner with switched analog and digital demodulators

• US 6,348,955 B1
• Filed: 02/23/1998
• Issued: 02/19/2002
• Est. Priority Date: 02/23/1998
• Status: Expired due to Term

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: Zenith Electronics Corporation (LG Corporation)
• Inventors: Tait, David S.
• Primary Examiner(s): Eisenzopf, Reinhard J
• Assistant Examiner(s): NATNAEL, PAULOS M
• Application Number:
  US09/027,688
• Time in Patent Office: 1,457 Days
• Field of Search: 348/725, 348/726, 348/731, 348/735, 348/678, 348/638, 348/639, 348/705, 348/706, 348/732, 348/733, 348/10, 348/554-556, 348/558, 455/553, 455/245.1, 455/246.1, 455/247.1, 455/337, 455/214
• US Class Current: 348/731
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/0007 wherein the AD/DA conversion occurs at radiofrequency or intermediate frequency stage
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/42638 involving a hybrid front-end, e.g. analog and digital tuners
• CPC Class Codes: H04N 5/46 for receiving on more than one standard at will deflecting circuits of multi-standard receivers H04N3/27
• CPC Class Codes: H04N 5/50 Tuning indicators; Automatic tuning control

Abstract

A television receiver includes a tuner for receiving either analog or digital signals. Separate analog and digital demodulators are selectively coupled to the tuner through an RF switch that is controlled by a sync detector in the output of the analog demodulator. The selected one of the demodulators develops an AGC signal that is coupled to the tuner through the RF switch. In one embodiment, a two pole RF switch is used with one pole switching the IF signal and the other pole switching the AGC signal In another embodiment, a single pole RF switch is used with the tuner signal and the AGC signal being multiplexed through the switch. This is accomplished by the provision of a high frequency path and a low frequency path between each of the RF switch and the tuner, the RF switch and the analog demodulator, and the RF switch and the digital demodulator.

Claims

1. A method of operating a television receiver for receiving either analog or digital signals comprising:

providing an analog demodulator and a digital demodulator;

providing RF switching means for selectively switching the tuner signal between the analog demodulator and the digital demodulator;

developing an AGC signal from the selected one of the analog and digital demodulators;

multiplexing the AGC signal with the tuner signal through the RF switching means;

developing the AGC signal from the selected one of the demodulators; and

wherein the multiplexing step is performed on the basis of the frequency difference between the tuner signal and the AGC signal;

developing a first signal indicative of the type of tuner signal; and

controlling the RF switching means with the first signal.

2. A television receiver for receiving either analog or digital signals comprising:

an analog demodulator and a digital demodulator;

an RF switch coupled between said tuner and said demodulators for selectively coupling the tuner signal between said analog demodulator and said digital demodulator;

means for developing an AGC signal from the selected one of said analog and said digital demodulators;

means for multiplexing said AGC signal with said tuner signal through said RF switch;

said multiplexing means operating on the basis of the frequency difference between the tuner signal and the AGC signal;

means for developing a first signal indicative of the type of said tuner signal; and

means for controlling said RF switch with said first signal.

3. The receiver of claim 2, wherein said RF switching means includes an RF switch, said AGC signal is developed from the selected one of said demodulators;

and said multiplexing means includes;

a high frequency path and a low frequency path coupled between each of

said RF switch and said tuner;

said RF switch and said analog demodulator; and

said RF switch and said digital demodulator.