Pulse or digital communications – Transceivers – Transmission interface between two stations or terminals
Utility Patent
1997-05-30
2001-01-02
Bocure, Tesfaldet (Department: 2731)
Pulse or digital communications
Transceivers
Transmission interface between two stations or terminals
Utility Patent
active
06169762
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to interface devices such as those used for telephony applications like modems and the like, and, more particularly, to such devices that require electrical isolation.
DESCRIPTION OF THE RELATED ART
The U.S. Federal Communications Commission (FCC) and counterpart regulatory agencies in other countries require telephone equipment to meet stringent requirements in order to protect the telephone lines from damage and degradation. Under one such requirement, telephone equipment must be electrically isolated from the telephone lines. Although the required electrical isolation varies by country, it is invariably demanding. For example, the U.S. requires 1500-volt isolation and other countries require up to 4000-volt isolation. As a result, telephone equipment must include some form of electrical isolation circuitry to prevent the telephone equipment from applying voltage surges or ground connections to the telephone lines, and vice versa.
FIG. 1
shows a block diagram of a conventional modulator/demodulator (modem)
100
, which is an interface device typically placed between a telephone line (i.e., the line side) and a user device, such as a data terminal or a computer (i.e., the device side). Modem
100
comprises data pump
102
, coder/decoder (codec)
104
, and data access arrangement (DAA)
106
. In conventional modems, the DAA provides the interface to analog phone lines and the data pump provides the interface to digital computer buses. The codec operates as an analog-to-digital (A/D) converter for incoming signals in the receive path (i.e., signals traveling from the line side to the device side) and a digital-to-analog (D/A) converter for outgoing signals in the transmit path (i.e., signals traveling from the device side to the line side). That is, the codec converts (1) the incoming analog signals received from the phone lines into digital signals for transmission to the computer and (2) the outgoing digital signals received from the computer into analog signals for transmission over the phone lines. As such, in conventional modems, the DAA comprises circuitry to process analog signals, while the data pump comprises circuitry to process digital signals. Data-pump processing involves (1) the digital-to-digital conversion of computer data streams into a narrow-bandwidth signaling pattern format suitable for application to the input of a D/A converter compatible with voice-band telephone lines and (2) the digital-to-digital conversion of such narrow-band data back into computer data streams.
In particular, in conventional modems, the DAA contains one or more of the following types of analog circuitry:
Electrical protection and high-voltage isolation circuitry to protect the phone lines and/or the computer (as well as the user) from high-voltage transients;
Line termination circuits to meet regulatory return loss requirements;
Transmit amplifier circuitry for controlling transmitted signal power for the outgoing analog signals and receive amplifier circuitry for controlling signal power in the receive path for the incoming analog signals; and
Two-wire-to-four-wire conversion circuitry for converting between the two-wire TIP/RING signals for the telephone line and the four-wire (RX+, RX−, TX+, and TX−) signals for the computer.
Depending on the sophistication of the circuitry, the DAA will contribute more or less degradation to the signals. For example, using large transformers in the DAA would provide a signal path with very little degradation, but using such transformers would be impractical for portable applications because of the size and weight.
In some conventional modems, an isolation transformer is used in the DAA to provide electrical isolation between the telephone lines and the computer. Transformers, however, suffer from excessive bulk and weight relative to most solid-state devices. Transformers are particularly cumbersome when used in modems designed for portable computers and other portable applications. In addition, transformers are relatively expensive, and pose reliability problems due to their mass when subject to mechanical shock or vibration.
What is needed is a scheme for providing low-degradation electrical isolation in modems that do not rely on transformers.
SUMMARY OF THE INVENTION
Embodiments of the present invention are directed to an interface device for interfacing between a first device and a second device. The interface device comprises (a) first-device-side circuitry, adapted to interface to the first device and to provide first-device-side codec processing; (b) second-device-side circuitry, adapted to interface to the second device and to provide second-device-side codec processing; and (c) a digital interface, connected between the first-device-side circuitry and the second-device-side circuitry and adapted to provide electrical isolation between the first device and the second device. The first-device-side circuitry and the second-device-side circuitry are adapted to apply sigma-delta modulation techniques to generate digital signals for transmission through the digital interface.
Alternative embodiments of the present invention are directed to analog front end (AFE) circuitry for an interface device for interfacing between a first device and a second device. The AFE circuitry forms second-device-side circuitry of the interface device which is adapted to interface to the second device and to provide second-device-side codec processing. The interface device further comprises first-device-side circuitry, adapted to interface to the first device and to provide first-device-side codec processing, and a digital interface, connected between the first-device-side circuitry and the second-device-side circuitry and adapted to provide electrical isolation between the first device and the second device. The first-device-side circuitry and the second-device-side circuitry are adapted to apply sigma-delta modulation techniques to generate digital signals for transmission through the digital interface.
Further alternative embodiments of the present invention are directed to an interface device for interfacing between a first device and a second device. The interface device comprises (a) first-device-side circuitry, adapted to interface to the first device; and (b) second-device-side circuitry, adapted to interface to the second device and to the first-device-side circuitry. The second-device-side circuitry comprises (1) an AC termination impedance, adapted to provide impedance for transmission-line AC requirements; (2) an inductor emulator, adapted to provide DC termination for the second device; and (3) a shunt regulator, adapted to control voltage levels seen by the second-device-side circuitry. The inductor emulator is connected in series with the shunt regulator.
Still further alternative embodiments of the present invention are directed to analog front end circuitry for an interface device for interfacing between a first device and a second device. The AFE circuitry comprises (1) an AC termination impedance, adapted to provide impedance for transmission-line AC requirements; (2) an inductor emulator, adapted to provide DC termination for the second device; and (3) a shunt regulator, adapted to control voltage levels seen by the AFE circuitry. The inductor emulator is connected in series with the shunt regulator.
REFERENCES:
patent: 4056719 (1977-11-01), Hizel
patent: 4331842 (1982-05-01), Kiko
patent: 4373117 (1983-02-01), Pierce
patent: 4395590 (1983-07-01), Pierce et al.
patent: 4417099 (1983-11-01), Pierce
patent: 4479066 (1984-10-01), Embree
patent: 4491700 (1985-01-01), Tahara et al.
patent: 4500754 (1985-02-01), Mackey
patent: 4514595 (1985-04-01), Rosenbaum et al.
patent: 4578533 (1986-03-01), Pierce
patent: 4592069 (1986-05-01), Redding
patent: 4715064 (1987-12-01), Claessen
patent: 4807283 (1989-02-01), Pyh{umlaut over (a)}lammi
patent: 4989243 (1991-01-01), Choi
patent: 5029203 (1991-07-01), Ikefuji et al.
patent: 5086454 (1992-02-01), Hizel
patent: 5218616 (1993-06-01), St
Embree Milton L.
Fischer Jonathan H.
Laturell Donald R.
Lee Robert F.
Bocure Tesfaldet
Lucent Technologies - Inc.
Mendelsohn Steve
LandOfFree
Interface devices providing electrical isolation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Interface devices providing electrical isolation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Interface devices providing electrical isolation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2530368