Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2001-01-02
2004-08-17
Corrielus, Jean B. (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S142000, C375S343000
Reexamination Certificate
active
06778593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Code Division Multiple Access (CDMA) type demodulator device. In particular, the present invention relates to a technique for demodulating information carried by respective channel signals from an up link signal specified in the CDMA standard conforming to IS-2000.
2. Description of the Related Art
FIG. 2
is a circuit diagram showing an exemplary structure of a modulator device
10
. The modulator device
10
is installed in a transmitter conforming to the current standard, i.e., the standard in conformity to IS-2000. The standard in conformity to IS-2000 is a standard which may be applied to CDMA receivers or cellular telecommunication systems according to CDMA modulation/demodulation techniques. The up link signal according to the standard in conformity to IS-2000 is composed of three channel signals, that is, a pilot channel signal, a supplemental channel signal and a fundamental channel signal.
In the circuit arrangement shown in
FIG. 2
, the modulator device
10
processes information for the pilot channel signal, information for the supplemental channel signal and information for the fundamental channel signal. The modulator device
10
includes multipliers A
1
and A
2
, gain adjustment circuits A
3
and A
4
, an adder A
5
, multipliers A
6
, A
7
, A
8
, A
9
, A
10
and A
11
, adders A
12
and A
13
, filter circuits A
14
and A
15
and an adder A
16
.
The multiplier A
1
modulates the information for the supplemental signal with the first Walsh-Code sequence. Such a modulation is generally called as spread spectrum modulation. As a result of the modulation using the first Walsh-Code sequence, the supplemental channel signal is obtained.
The multiplier A
2
modulates the information for the fundamental signal with the second Walsh-Code sequence, thereby the fundamental channel signal is obtained.
The gain adjustment circuits A
3
and A
4
adjust a gain of an amplitude component of the supplemental channel signal and a gain of an amplitude component of the fundamental channel signals, respectively.
The adder A
5
multiplexes the supplemental channel signal output from the gain adjustment circuit A
3
and the fundamental channel signal output from the gain adjustment circuit A
4
, so as to obtain an information channel signal.
The multiplier A
6
multiplies a long-code sequence, that is a part of a PN(Pseudorandom Noise)-Code sequence, by a PN (Pseudorandom Noise)-Code sequence that corresponds to an inphase component, PNi, thereby the first orthogonal code sequence is obtained. Similarly, the multiplier A
7
multiplies the above long-code sequence by a PN (Pseudorandom Noise)-Code sequence corresponding to a quadrature component, PNq, thereby the second orthogonal code sequence.
The multiplier A
8
modulates the pilot channel signal carrying the information for the pilot channel signal by spread spectrum modulation using the first orthogonal code sequence output from the multiplier A
6
. The modulated pilot channel signal is used as an inphase component of the pilot channel signal. The multiplier A
9
modulates the information channel signal output from the adder A
5
by spread spectrum modulation using the first orthogonal code sequence output from the multiplier A
6
. The modulated information channel signal is used as a quadrature component of the information channel signal. The multiplier A
10
modulates the information channel signal from the adder A
5
by spread spectrum modulation using the second orthogonal code sequence output from the multiplier A
7
. The thus modulated information channel signal is used as an inphase component of the information channel signal. The multiplier A
11
modulates the pilot channel signal with spread spectrum modulation using the second orthogonal code sequence output from the multiplier A
7
. The thus modulated pilot channel signal is used as a quadrature component of the pilot channel signal.
The adder A
12
multiplexes the inphase component of the pilot channel signal output from the multiplier A
8
and that of the information channel signal output from the multiplier A
10
, thereby an inphase component of a channel signal is obtained. The adder A
13
multiplies the quadrature component of the pilot channel signal output from the multiplier A
9
and the quadrature component of the information channel signal from the multiplier. The multiplexed signal is used as a quadrature component of the channel signal.
The filter circuit A
14
adjusts the gain of the amplitude component of the inphase component of the channel signal output from the adder A
12
by a low-pass filter. The filter circuit A
14
rotates the phase of the adjusted signal by 90 degrees. The resultant signal is used as an inphase component of a transmitted signal TS. The filter circuit A
15
adjusts the gain of the quadrature component of the channel signal output from the adder A
13
by a low-pass filter. The thus adjusted signal is used as a quadrature component of the transmitted signal TS.
The adder A
16
multiplexes the inphase and the quadrature components of the transmitted signal TS that are respectively output from the filter circuits A
14
and A
15
, so as to obtain the transmitted signal TS.
As described above, the modulator device
10
modulates information for the three channel signals, i.e., information for the pilot channel signal, information for the supplemental channel signal and information for the fundamental channel signal by spread spectrum modulation using Walsh-Code sequence or spread spectrum modulation both Walsh-Code sequence and Orthogonal-Code sequence. The modulator device
10
multiplexes the modulated three channel signals to obtain the transmitted signal TS, and then transmits the transmitted signal TS.
It should be noted that the pilot channel signal is different from the supplemental channel signal that is used as the information channel signal. Also, the pilot channel signal is different from the fundamental channel signal that is used as the information channel signal. The modulator device
10
does not modulate the pilot channel signal by the spread spectrum modulation using the Walsh-Code sequence. Instead, the pilot channel signal is used for estimating a radio propagation path. When the receiver demodulates the pilot channel signal, the receiver uses a demodulation method different from that used for the supplemental channel signal and the fundamental channel signal.
FIG. 3
shows an exemplary demodulator device
11
included in the receiver. The demodulator device
11
receives the transmitted signal TS transmitted from the transmitter having the modulator device
10
as a received signal RS. The received signal RS is a signal that has passed through a propagation path composed of a multi-path fading environment. The demodulator device
11
extracts the three channel signals, i.e., the pilot channel signal, the supplemental channel signal and the fundamental channel signal from the received signal RS. The demodulator device
11
demodulates the information for the supplemental channel signal from the extracted supplemental channel signal and the information for the fundamental channel signal from the extracted fundamental channel signal.
The demodulator device
11
includes path demodulator units B
1
, B
2
and B
3
. The path demodulator unit B
1
corresponds to a path
1
; the path demodulator unit B
2
corresponds to a path
2
; and the path demodulator unit B
3
corresponds to a path N. These path demodulator units are finger circuits.
The path demodulator unit B
1
includes demodulator circuits
1
,
2
and
3
that are denoted by B
4
, B
5
and B
6
, respectively so as to demodulate the channel signals
1
,
2
and N in the path
1
. The path demodulator unit B
2
includes demodulator circuits
1
,
2
and
3
that are denoted by B
7
, B
8
and B
9
, respectively so as to extract the channel signals
1
,
2
and N in the path
2
. The path demodulator unit B
3
includes demodulator circuits
1
,
2
and
3
that are denoted by B
10
,
Corrielus Jean B.
Oki Electric Industry Co. Ltd.
Sartori Michael A.
Venable LLP
Vivarelli, Jr. Daniel G.
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