Data processing: generic control systems or specific application – Specific application – apparatus or process – Digital audio data processing system
Reexamination Certificate
1999-10-13
2002-04-16
Lee, Ping (Department: 2644)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Digital audio data processing system
C381S119000, C710S303000
Reexamination Certificate
active
06374148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to portable multimedia computers, and more particularly to a digital audio link to a docking station.
2. Description of the Related Art
Portable computers continue to grow in popularity at a more rapid pace than ordinary desktop personal computers (PC's). These notebook or laptop PC's are extremely powerful, having many of the features of state-of-the-art desktop PC's. Recently, multimedia capabilities have been added to laptop PC's. Stereo speakers, a microphone, and FM synthesizers and other audio capabilities are built in to many multimedia laptop PC's.
Docking stations or port replicators have been used to bridge the gap between the capabilities of older laptop PC's and those of desktop systems. Some docking stations allow expansion or AT-bus cards to be plugged into an industry-standard ISA bus giving the laptop expansion abilities like that of a desktop PC. For example, older laptop PCs did not include audio capabilities. Audio capabilities can be added to these laptops by plugging them into a docking station that had a sound card installed in the ISA bus.
Newer laptop PC's often contain the equivalent of a sound card. Since sound cards use many of the same fixed resources such as interrupts (IRQ's), I/O addresses, and DMA channels, it is generally not feasible to have more than one sound card in a PC. Thus, newer multimedia laptops should not be used with a docking station with a sound card unless the laptop's sound card can be disabled. Unfortunately, disabling the sound-card features in a laptop is not always easy or even possible.
DOCKING STATION SOUND CARDS INCOMPATABLE WITH MULTIMEDIA LAPTOPS
The incompatibility of internal laptop sound cards with docking-station sound cards prevents many docking stations from using sound cards. These docking stations support only analog audio; the digital-sound features of most sound cards are not supported.
The laptop's sound system generates and outputs analog audio signals, which are sent to the docking station for playing on external speakers connected to the docking station. Audio mixing is not performed by the docking station. Audio from a CD player in the docking station must be mixed with computer-generated sound by a mixer inside the laptop and then output back out to the external speakers.
DOCKING STATION—FIG.
1
FIG. 1
shows a laptop PC with a docking station, highlighting audio components. Laptop PC
10
is a multimedia laptop with audio features built-in. A user's voice can be picked up by internal microphone
14
, which is built in to the laptop's housing. Internal speakers
12
are also built in to the laptop's housing, and provide stereo sound generated by the internal sound card inside laptop PC
10
.
While it is convenient to have a built-in internal microphone
14
and internal speakers
12
, the small, compact size of laptop PC
10
prevents the use of high-quality audio components. High-fidelity speakers require a large magnet and large-diameter diaphragm sound cones, which simply do not fit inside a laptop PC.
Laptop PC
10
fits into docking station
20
. External connectors are provided on the back of laptop PC
10
to make electrical connection with docking-station connectors
16
. Digital signals are included in connectors
16
to control an external expansion bus in docking station
20
, such as an ISA bus or a PCI bus (not shown). Other peripherals often included in docking station
20
include connections for a printer, modem, external monitor, or network. Since an audio card in docking station
20
would have resource conflicts with the internal sound card in laptop PC
10
, a sound card cannot be added to docking station
20
. Instead, analog signals output from the sound card in laptop PC
10
are output to connectors
16
. These analog audio signals from laptop PC
10
are routed to high-fidelity external speakers
18
connected to docking station
20
. It is difficult or impossible for the user to disable the internal speakers without losing significant quality when using the external speakers in the several prior-art systems.
Analog input from external microphone
22
is sent from docking station
20
to laptop PC
10
, as can input from other audio sources connected to a line-in (L/IN) input on docking station
20
. Digital or analog-signal mixing of these input sources typically cannot be performed in docking station
20
. Docking station
20
may also provide audio amplification since a separate power supply is included in docking station
20
.
AUDIO NOISE FROM CONNECTORS
FIG. 2
highlights connectors on the back of a laptop PC. Parallel-port connector
32
is used to connect to a printer or other parallel device. Serial-port connector
34
is a D-type plug for connecting an external serial device such as an external modem. Connectors
32
,
34
are often used without a docking station. A VGA connector (not shown) is also included in many docking stations for connection to an external CRT monitor.
Docking connector
30
is a special-purpose connector containing a variety of signals for connecting to a docking station. While parallel-port connector
32
and serial connector
34
are industry-standard connectors, docking connector
30
is a proprietary connector. Docking connector
30
is only able to fit docking stations made for the specific manufacturer and model of laptop PC.
Docking connector
30
contains address, data, and control signals for an external PCI or ISA bus in the docking station, allowing expansion cards plugged into the docking station's bus to be controlled by a docked laptop PC. Data from an external DVD or CD-ROM drive in the docking station can also be sent to the laptop PC thorough docking connector
30
. Power and ground signals may also be included in docking connector
30
. High-speed signals such as digital video data streams are often separated form other signals in docking connector
30
by power or ground signals to act as shielding, preventing cross-talk to adjacent signals.
ANALOG AUDIO SUSCEPTIBLE TO CROSS-TALK NOISE
While analog audio signals from the internal sound card in the laptop PC could be sent through docking connector
30
, this is undesirable because of noise injection from high-speed digital signals in docking connector
30
. Digital signals operating at high frequencies such as clock signals and video or CD-ROM data streams couple noise into other signals in docking connector
30
. Even signals that are not immediately adjacent to the higher-speed signals can suffer from noise injection as common ground signals and the metal housing of the connector can inject noise into all signals in docking connector
30
. Thus docking connector
30
is inherently a noisy environment.
Most digital signals have high noise margins, so a moderate amount of noise injection is tolerable. However, analog signals are sensitive to small voltage changes since the voltage level itself conveys the information, such as the sound intensity. Thus, any analog audio signals sent through docking connector
30
suffer from noise injection. The listener notices the noise injection as scratchy or low-quality sounds from any external speakers attached to the docking station.
SEPARATE ANALOG AUDIO CONNECTORS TO DOCKING STATION
The severe noise injection of docking connector
30
prevents inclusion analog audio signals in docking connector
30
for higher-quality docking stations. Instead, separate analog audio connectors
36
are provided to connect analog audio signals from a docked laptop PC to the docking station. Audio connectors
36
are often round plugs or jacks with concentric shielding around one or two signal lines, such as standard audio jacks. For example, a speaker connector has two signal lines for the two stereo speakers, surrounded by a ground.
Often three, four, or five audio connectors
36
are used. Stereo outputs from the laptop PC are contained in a speaker connector, while inputs from the docking station to the lap
Agarwal Suresh
Dharmarajan Krishnan C.
Auvinen Stuart T.
Lee Ping
NeoMagic Corp.
LandOfFree
Portable-PC audio system with digital-audio links to... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Portable-PC audio system with digital-audio links to..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Portable-PC audio system with digital-audio links to... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2903967