Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Reexamination Certificate
2000-08-04
2004-11-02
Patel, Ajit (Department: 2664)
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
C370S503000, C379S149000
Reexamination Certificate
active
06813262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a synchronization tracking device and method in a code division multiple access (hereinafter, referred to as CDMA) receiver, and more particularly, to a synchronization tracking device and method in a CDMA receiver which is capable of obtaining channel tracking results and energy values for all paths existing within a time section corresponding to a delay profile during a synchronization tracking for an initial synchronization in a CDMA communication system to thereby carry out demodulation for a best path with the obtained result and continuously correcting the information of the corresponding path to thereby ensure a high performance of the receiver.
2. Discussion of Related Art
A CDMA communication system generally divides channels by a pseudo noise code and upon call opening, checks the pseudo noise code to conduct channel connection. The checking procedure for the pseudo noise code is classified into code recognition and synchronization tracking. Through the code recognition, the codes generated by the receiver itself are adjusted to have a variation in a range of a single chip with received signals and through the synchronization tracking, an accurate synchronization acquiring and tracking for the received signals are completed. Based upon the synchronization tracking result, the phase information and energy value for a specific path are obtained.
In a mobile radio communication environment, signals on a plurality of paths are naturally generated according to a channel characteristic, which is called a multiple path signal. So as to improve the performance of the receiver, a plurality of signals in the multiple path signals are demodulated and coupled. To this end, since the phase information and energy values for the plurality of multiple path signals should be required, the synchronization tracking for each path has to be carried out.
Now, an explanation of the construction and operation of a conventional synchronization tracking device in a CDMA receiver will be discussed.
FIG. 1
is a block diagram illustrating the construction of the conventional synchronization tracking device in the CDMA receiver.
A reference numeral
10
denotes a delay code generator for delaying a pseudo noise code generated in the receiver itself by a predetermined time &dgr;, a reference numeral
30
represents a first multiplier for multiplying the received signal and the pseudo noise code generated in the delay code generator
10
, a reference numeral
20
denotes a fast code generator for generating a fast pseudo noise code which is made by making the pseudo noise code generated in the receiver itself substantially fast by the predetermined time &dgr;, and a reference numeral
40
represents a second multiplier for multiplying the received signal and the pseudo noise code generated in the fast code generator
20
. Reference numerals
50
and
70
denote first and second band-pass filters for filtering the output signals from the first and second multipliers
30
and
40
to an arbitrary intermediate frequency, and reference numerals
60
and
80
denote first and second envelope detectors for detecting envelope values from the output signals filtered from the first and second band-pass filters
50
and
70
. A reference numeral
90
represents a subtracter for subtracting the envelope value detected in the second envelope detector
80
from the envelope value detected in the first envelope detector
60
, thereby outputting the subtracted result value. In addition, a reference numeral
100
denotes a loop filter for low-pass filtering the envelop difference signal outputted from the subtracter
90
, and a reference numeral
110
represents a voltage controlled oscillator for outputting an arbitrary oscillating frequency in accordance with the filtered signal in the loop filter
100
. A reference numeral
120
denotes a pseudo noise code generator for generating a pseudo noise code which is proportional to the phase of the oscillating frequency outputted from the voltage controlled oscillator
110
, a reference numeral
130
represents a local oscillator for generating an arbitrary local frequency for adjusting the phase of the pseudo noise code generated in the pseudo noise code generator
120
, and a reference numeral
140
denotes a mixer for mixing the pseudo noise code generated in the pseudo noise code generator
120
and the local frequency generated in the local oscillator
130
, thereby outputting the mixed result as the pseudo noise code generated in the receiver itself.
In operation, the delay code generator
10
delays the pseudo noise code outputted from the mixer
140
by the predetermined time &dgr; and transmits the delayed pseudo noise codes to the first multiplier
30
, and the fast code generator
20
generates the fast pseudo noise code preceding the pseudo noise codes outputted from the mixer
140
by the predetermined time &dgr; and transmits the fast pseudo noise code to the second multiplier
40
.
The first multiplier
30
mixes the received signal inputted and the pseudo noise code delayed by the predetermined time &dgr; in the delay code generator
10
and outputs the mixed result to the first band-pass filter
50
. The second multiplier
40
mixes the received signal inputted and the fast pseudo noise code preceding the pseudo noise codes by the predetermined time &dgr; in the fast code generator
20
and outputs the mixed result to the second band-pass filter
70
.
The first and second band-pass filters
50
and
70
band-pass filter the mixed signals in the first and second multipliers
30
and
40
and output the filtered signals to the first and second envelope detectors
60
and
80
.
The first and second envelope detectors
60
and
80
detect the envelope values of the output signals from the first and second band-pass filters
50
and
70
and output the envelope values to the subtracter
90
.
The subtracter
90
subtracts the envelope value detected in the second envelope detector
80
from the envelope value detected in the first envelope detector
60
and outputs the subtracted result value to the loop filter
100
.
The loop filter
100
eliminates other signals over the band in the envelope difference signal outputted from the subtracter
90
and outputs the output signal to the voltage controlled oscillator
110
. The voltage controlled oscillator
110
outputs the arbitrary oscillating frequency to the pseudo noise code generator
120
in accordance with the filtered signal in the loop filter
100
.
The pseudo noise code generator
120
generates the pseudo noise code which is proportional to the phase of the oscillating frequency provided from the voltage controlled oscillator
110
and outputs the generated pseudo noise code to the mixer
140
.
The mixer
140
mixes the local frequency provided from the local oscillator
130
and the generated pseudo noise code in the pseudo noise code generator
120
for adjusting the phase of the pseudo noise code outputted from the pseudo noise code generator
120
to thereby generate a final pseudo noise code and outputs the final pseudo noise code to the first and second multipliers
30
and
40
, respectively.
As a result, the conventional synchronization tracking device in the CDMA receiver carries out correlation between the received signal and the pseudo noise code generated in the receiver itself and delayed by the predetermined time &dgr; and between the received signal and the fast pseudo noise code preceding the pseudo noise code by the predetermined time &dgr;, thereby obtaining energy values and calculates the energy value difference to adjust the phase of the pseudo noise code generated to be proportional to the phase difference between the two signals, thereby enabling accurate synchronization tracking and phase to be maintained.
Under the conventional synchronization tracking device in the CDMA receiver, however, the synchronization tracking method conducts the tracking for only a single path in a single synchro
Lee Woo Jae
Yoon Cheon Soo
Bryan Cave LLP
Hyundai Electronics Ind. Co. Ltd.
Patel Ajit
Shah Chirag
LandOfFree
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