Adaptive receiver linearity techniques for a radio transceiver

Details Adaptive receiver linearity techniques for a radio transceiver Adaptive receiver linearity techniques for a radio transceiver

1998-04-01

2001-10-02

Legree, Tracy (Department: 2681)

Telecommunications

Transmitter and receiver at same station

C455S063300, C455S296000, C455S234100

Reexamination Certificate

active

06298221

ABSTRACT:

BACKGROUND OF THE INVENTION
CDMA telephones operate according to the IS-95 standard. These devices operate generally as shown in the block diagram of FIG.
1
. The user speaks into a microphone
100
. The audio from the microphone
100
is processed by processor
102
, and amplified by high power amplifier (HPA)
104
. The output of HPA
104
is coupled through duplexer
108
to antenna
110
. Duplexer
108
allows both transmission and reception to occur at the same time.
Transmissions received from antenna
110
are coupled through duplexer
108
to low noise amplifier (LNA)
112
. The output of LNA
112
is processed by processor
114
, and reproduced to the user through speaker
116
.
The duplexer
110
is not perfect. It allows some transmit-to-receive crosstalk shown as
109
. A measure of the transmit to receive crosstalk is available for many duplexers.
The transmitter
110
communicates with a base station shown generally as
150
. Different effects occur depending on the distance between the transmitter
110
and the base station
150
. When the handset
99
is close to the base station
150
, the transmitter needs to transmit a relatively low amount of power and receives a relatively large amount of power. However, when the handset
99
is far away from the base station
150
, it needs to transmit a large amount of power to reach the base station, and it receives only a small amount.
Other handsets which are close by are also similarly transmitting a large amount and receiving a small amount. These other handsets transceive on different frequencies. However, non-linearities in the components cause addition and different products to be formed. The other close handsets effectively become interferers.
In addition, the transmitted signal beam leaks through the duplexer as
109
and also forms another interference signal.
Interferers in non-desired bands can be eliminated by filtering, even though they may in many cases be at a higher amplitude than the actual desired signal. However, non-linearities in the LNA and/or any mixers, can cause intermodulation distortion which effectively mixes these products together. The noise from the undesired signals may be mixed into the band of desired signals. Since the noise is in the desired band, it becomes more difficult to filter out. This lowers the signal-to-noise ratio of the system as the handset gets farther from the base station.
It is also important that portable telephones have the maximum possible battery life.
SUMMARY OF THE INVENTION
The present disclosure describes a system intended to minimize the above drawback. This is done by adaptively modifying some aspect of reception Linearity performance of the receiver based on transmitted signal power level.
Many LNAs become less linear when driven in a mode where less current is consumed. Most LNAs for portable telephones are driven in this reduced current mode in order to decrease power consumption. The inventor recognized, however, that during the transmitting time, the LNA is still using a lot less power than the HPA. During that time, the current draw of the LNA is not significant compared with the current drawn by the HPA.
The system as described in this specification improves reception sensitivity during the time of simultaneous transmission and reception. However, receiver power consumption during reception-only intervals is preferably not increased. Hence, performance is increased without significant decrease in battery life.


REFERENCES:
patent: 5001776 (1991-03-01), Clark
patent: 5204970 (1993-04-01), Stengel et al.
patent: 5287211 (1994-02-01), Grimes et al.
patent: 5625674 (1997-04-01), Paniccia, Jr.
patent: 5694433 (1997-12-01), Dent
patent: 5732341 (1998-03-01), Wheatley, III
patent: 6070091 (2000-05-01), Hogevik

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