Telecommunications – Transmitter and receiver at separate stations – Having measuring – testing – or monitoring of system or part
Utility Patent
1998-04-06
2001-01-02
Vo, Nguyen (Department: 2745)
Telecommunications
Transmitter and receiver at separate stations
Having measuring, testing, or monitoring of system or part
C455S115200
Utility Patent
active
06169884
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the prevention of heat buildup in radio transmitters.
2. State of the Art
Wireless data and voice connectivity is increasingly in demand. Wireless data connectivity is typically achieved using a wireless modem/radio combination. This combination is often referred to generically as a wireless modem.
Wireless modems exist for various radio transmission standards. One such standard is the CDPD, or Cellular Digital Packet Data, standard. The CDPD service is implemented as an overlay on top of the AMPS, or Advanced Mobile Phone System, standard for cellular telephone communications. Within AMPS, a cellular telephone is instructed to transmit at one of several different power levels depending on the distance of the cellular telephone from a supervising radio base station. Similarly, the radio of a CDPD wireless modem is instructed to transmit at one of several different power levels. Nominal power levels within the AMPS/CDPD system are shown in Table I.
TABLE 1
Mobile Station Nominal Power Levels
Nominal ERP
Mobile Station
Mobile
dBW*
Power Level
Attenuation
Mobile Station Power Class
(PL)
Code (MAC)
I
II
III
0
000
6
2
−2
1
001
2
2
−2
2
010
−2
−2
−2
3
011
−6
−6
−6
4
100
−10
−10
−10
5
101
−14
−14
−14
6
110
−18
−18
−18
7
111
−22
−22
−22
*Nominal ERP values in watts for power level 0 are:
I. +6 dBW = 4.0 W
II. +2 dBW = 1.6 W
III. −2 dBW = 0.6 W
Currently, a popular form factor for wireless modems is that of the PC Card, formerly referred to as the PCMCIA card. During use, a PC Card is inserted into a PC Card slot in a computer, such as a laptop or notebook computer. It is common for a PC Card wireless modem to have a portion that extends outside the PC Card slot. It is desirable, however, for a PC Card wireless modem to fit entirely within a PC Card slot. When such a PC Card is inserted into the PC Card slot, the surface area of the PC Card, with the exception of a small end surface, is entirely enclosed by the PC Card slot, greatly restricting air circulation.
Because the first PCMCIA cards were typically memory cards and other relatively low-power devices, the PCMCIA standard gave little or no consideration to heat dissipation. Similarly, the current PC Card standard does not address issues of heat dissipation. Consequently, for a PC Card wireless modem of the type described, if prolonged transmission at high power levels is performed, heat buildup may occur. Such heat buildup is disadvantageous in several respects. Heat buildup may reduce the expected useful life of the wireless modem. Furthermore, heat may build up to such an extent that, when the user withdraws the wireless modem from the PC Card slot, the wireless modem is hot to the touch. In extreme cases, the modem may be sufficiently hot as to cause discomfort or even mild burns. In any event, such heat buildup will likely be the cause of consternation on the part of the user.
Therefore, there exists a need for a method and apparatus whereby heat buildup in a wireless modem or other device including a radio transmitter may be substantially reduced. The present invention addresses this need.
SUMMARY OF THE INVENTION
The present invention, generally speaking, provides a mechanism for substantially reducing heat buildup within a mobile radio device having a radio transmitter. The invention is particularly applicable to PC Card wireless modems. In accordance with one aspect of the invention, device temperature in a mobile radio device is controlled by monitoring the temperature of the mobile radio device; if the temperature of the mobile radio device exceeds a threshold then, when the mobile radio device is to transmit information, transmission power of the mobile radio device is reduced, thereby reducing the amount of heat generated within the mobile radio device and allowing the temperature of the mobile radio device to decrease. Transmission power is reduced sufficiently to allow the temperature of the mobile radio to decrease but not so much as to affect the reliability of transmission in the typical case. In this respect, the technique takes advantage of extra margin built into commonly-employed radio data transmissions standards such as the CDPD (Cellular Digital Packet Data) standard.
In accordance with another aspect of the invention, a mobile radio device includes a power amplifier, a temperature-variable component, and a microprocessor/microcontroller coupled to the power amplifier and the temperature-variable component. A memory coupled to the microprocessor/microcontroller contains instructions for monitoring device temperature and reducing transmission power when a temperature threshold is exceeded, in the same manner as described previously. The mobile radio device may advantageously be formed as a PC Card.
In accordance with another aspect of the present invention heat and power is reduced by inserting brief pauses at intervals during transmission by the mobile radio device effectively reducing the transmission duty cycle, the transmit amplifier being turned off during such pauses. The pauses are made sufficiently short in duration that the radio connection is not lost.
In another embodiment, the data transmission mode (i.e. receive mode or transmit mode) of the host processor coupled to the mobile radio device is monitored. In the case when the host processor is receiving data, brief pauses are inserted into the SAT signal being transmitted from the mobile radio device, where the transmit amplifier is turned off during such pauses and the pauses are made sufficiently short in duration that the radio connection is not lost. In one embodiment, the data transmission mode is monitored by a microprocessor within a modem coupled between the mobile radio device and the host processor.
REFERENCES:
patent: 5519886 (1996-05-01), Gilbert et al.
patent: 5603101 (1997-02-01), Choi
patent: 5774784 (1998-06-01), Ohno
patent: WO94/29968 (1994-12-01), None
patent: WO96/33555 (1996-10-01), None
European Patent Office, Patent Abstracts of Japan, Publication No. 09300866, Oki Electric Ind Co Ltd, Published Nov. 25, 1997.
Banks-Harold Marsha D.
Burns Doane Swecker & Mathis L.L.P.
Sierra Wireless Inc.
Vo Nguyen
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