Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Generating rectangular
Reexamination Certificate
2000-05-12
2001-05-29
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Generating rectangular
C327S172000
Reexamination Certificate
active
06239636
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to waveform generation, and more particularly to a method and apparatus for generating a digital waveform in a dual mode wireless device.
BACKGROUND OF THE INVENTION
A number of different standards and technologies for operating wireless telephones exist today. In order to operate properly, a wireless telephone must be within the boundaries of a wireless telephone system that supports the same technology and is able to operate at the same frequency as the wireless telephone. As a result, dual mode wireless telephones exist today that are designed for use in more than one wireless telephone system. For example, a wireless telephone that operates in both an Advanced Mobile Phone Service (“AMPS”) mode and a Global System for Mobile Communication (“GSM”) mode is known. The object of such dual mode combinations is generally to enable the user to transfer a wireless telephone outside of their home service area and increase the probability that the wireless telephone will continue to have wireless service available.
FIG. 1
is a schematic diagram of data transmission flow in a known dual mode wireless device operable in either the AMPS mode or the GSM mode. As illustrated in
FIG. 1
, a dual mode wireless device, such as a wireless telephone, includes a controller circuit
200
and a transmitter circuit
202
connected along a bus
204
. Both analog and digital data signals, corresponding to voice and data, are input from a microphone
206
and an interface
208
of a computer device, for example, to a data source
210
located at the controller circuit
200
. When the dual mode wireless device is operated in an AMPS mode, the analog signals from the microphone
206
are converted to digital data by an A/D converter
214
located in the AMPS unit
212
, and added to the digital data input to the data source
210
by the interface
208
of the computer device using an adder
216
. The resulting added signals output by the adder
216
are received by an input register
218
located within a digital signal processor
220
of the controller circuit
200
.
On the other band, when the wireless telephone is operated in the GSM mode, the analog signals output by the data source
210
after being received from the microphone
206
are converted to digital data signals by an A/D converter
224
located in a GSM unit
222
, and both the digital data signals input by the data source
210
from interface
208
of the computer device and the digital data signals output from the A/D converter
224
are sent to an interleaver
226
of the GSM unit
222
. The interleaver
226
interleaves the digital data signals according to GSM protocol, and outputs the interleaved data signals to the input register
218
of the digital signal processor
220
.
Depending upon whether the device is being operated in the AMPS or the GSM mode, the digital data signals are transferred from the input register
218
to a microprocessor
228
of the digital signal processor
220
to be packaged and buffered to form processed data that is then output from the digital signal processor
220
to an output register
230
of the controller circuit
200
. The processed data is held in the output register
230
until a new piece of data is required by the transmitting circuit
202
, at which time the processed data is transferred from the output register
230
of the controller circuit
200
to the bus
204
connecting the controller circuit
200
to the transmitter circuit
202
. The processed data is transferred along the bus
204
to an input register
232
of the transmitter circuit
202
and is transferred from the input register
232
to an interpolator
234
. The interpolator
234
interpolates the processed data and outputs the resulting interpolated data to a modulator
236
. The modulator
236
modulates the interpolated data, and the resulting modulated data is then output by the transmitter circuit
202
through an antenna (not shown).
In the prior art dual mode wireless telephone of
FIG. 1
, each time the transmitter circuit
202
requests a packet of data from the controller circuit
200
, the requested data packet must be generated by the signal processor
220
and transported along the bus
204
from the output register
230
of the controller circuit
200
to the input register
232
of the transmitter circuit
202
. As a result, each time the transmitter circuit
202
requests a packet of data from the controller circuit
200
, current processing from the signal processor
220
must be interrupted to enable the signal processor
220
to generate the data packet. As the rate of these interruptions increases, a bottleneck tends to form both between the signal processor
220
and the output register
230
of the controller circuit
200
and along the bus
204
between the controller circuit
200
and the transmitter circuit
202
, corrupting reliability of the data transmission. This bottleneck results from noise that is caused from high clock rates at the bus
204
, which desensitize the receiver receiving the output from the transmitter circuit
202
, and from high current drain in MIPS (million instructions per second) between the digital signal processor
220
and the output register
230
, which lowers the battery life of the device.
One method available to reduce the interrupt rate to the digital signal processor
220
caused by the requests for data from the transmitter circuit
202
is for the digital signal processor
220
to generate a large set of data and create a buffer at output register
230
from which the transmitter circuit
202
draws data in real time. As a result, the interruptions of the digital signal processor
220
are reduced, occurring only when the buffer required additional data. This buffer method reduces the interrupt rate to the digital signal processor
220
, allowing more efficient operation so that lower MIPS are required by the digital signal processor
220
, reducing current drain on the battery and increasing battery life. However, not all supported integrated circuits include the necessary buffer capacity built into the controller circuit
200
.
In addition, the signal from the interpolator
234
could be pre-distorted using analog components in the present state of the art, in order to reduce the effects of distortion caused by bandwidth limitations in the modulator unit
236
. To achieve analog pre-distortion and to achieve modulated signal accuracy and cleanliness, active operational amplifiers, switches, and extra inductors and capacitors may need to be added to the transmitter circuit
202
to obtain the required accuracy. These support circuits increase the size and cost of the transmitter circuit so that such as approach would be difficult and costly using current technology. In addition, even if support was available on the transmitter circuit
202
, the higher data rate involved in transporting the high speed data from the output register
230
across the bus
204
to the input register
232
of the transmitter circuit
202
would cause radio interference back through the antenna, causing the radio to be de-sensitized.
Accordingly, what is needed is dual mode wireless telephone device that minimizes bottlenecks by reducing an interrupt rate of the signal processor while at the same time reducing interference in neighboring bands.
REFERENCES:
patent: 5574979 (1996-11-01), West
Hietala Alexander Wayne
Solar John Thomas
Motorola Inc.
Nguyen Linh
Soldner Michael C.
Tran Toan
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