Receiver

Details Receiver Receiver

2000-07-14

2004-04-06

Ghayour, Mohammad H. (Department: 2631)

Pulse or digital communications

Receivers

Angle modulation

Reexamination Certificate

active

06717993

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a receiver, particularly to a receiver for demodulating a signal to be PSK-modulated in which digital signals modulated by 2-, 4-, and 8-phase PSK modulation systems are time-multiplexed in accordance with a hierarchical transmission system or the like by using a carrier wave regenerated by carrier-wave regenerating means to output I and Q symbol-stream data.
BACKGROUND ART
Practical use of digital satellite TV broadcast is advanced which conforms to a plurality of modulation systems having necessary C/Ns different from each other such as hierarchical transmission systems in which a wave to be 8PSK-modulated, a wave to be QPSK-modulated, and a wave to be BPSK-modulated are time-multiplexed and repeatedly transmitted with frame.
FIG.
11
(
1
) is an illustration showing a frame configuration of a hierarchical transmission system. One frame is configured by a frame-synchronizing-signal pattern comprising 32 BPSK-modulated symbols (20 latter-half symbols among 32 symbols are actually used as frame-synchronizing signal), a TMCC (Transmission and Multiplexing Configuration Control) pattern comprising 128 BPSK-modulated symbols to identify a multiple transmission configuration, a super-frame identifying signal pattern comprising 32 symbols (20 latter-half symbols among 32 symbols are actually used as super-frame identifying signal), a main signal of
203
8PSK(trellis-codec-8PSK)-modulated symbols, a burst symbol signal (BS) of four symbols in which a pseudo random noise (PN) signal is BPSK-modulated, a main signal of
202
8PSK(trellis-codec-8PSK)-modulated symbols, a burst symbol signal (BS) of four symbols in which a pseudo random noise (PN) signal is BPSK-modulated, . . . , a main signal of
203
QPSK-modulated symbols, a burst symbol signal (BS) of four symbols in which a pseudo random noise (PN) signal is BPSK-modulated, a main signal of
203
QPSK-modulated symbols, and a burst symbol signal (BS) of four BPSK-modulated symbols in order.
In case of a receiver for receiving a digital wave to be modulated (wave to be PSK-modulated) according to a hierarchical transmission system, an intermediate-frequency signal of received signals received by a receiving circuit is demodulated by a demodulating circuit and two-series I and Q base-band signals (hereafter, I and Q base-band signals are also referred to as I and Q symbol-stream data) showing instantaneous values of I-axis and Q-axis orthogonal to each other for each symbol are obtained. Absolute phase generation to be fitted to a transmission-signal phase angle is performed by an absolute-phase generating circuit by acquiring a frame-synchronizing signal from the demodulated I and Q base-band signals, obtaining the present received-signal-phase rotation angle from a signal point arrangement of the acquired frame-synchronizing signal, and inversely rotating the phase of the demodulated I and Q base-band signals on the basis of the obtained received-signal phase rotation angle.
As shown in
FIG. 12
, an absolute-phase generating circuit of a receiver for receiving a wave to be PSK-modulated according to a conventional hierarchical transmission system is configured by a frame-sync detecting/regenerating circuit
2
serving as frame-synchronizing-signal acquiring means provided for the output side of a demodulating circuit
1
to acquire a frame-synchronizing signal, a remapper
7
serving as inversely-phase-rotating means comprising a ROM, and a received-signal-phase-rotation-angle detecting circuit
8
serving as received-signal-phase-rotation-angle detecting means. Symbol
9
denotes a transmission-configuration identifying circuit for identifying the multiple transmission configuration shown in FIG.
11
(
1
), which outputs a two-bit modulation-system identifying signal DM.
The demodulating circuit
1
orthogonally detects intermediate-frequency signals to obtain I and Q base-band signals. In the demodulating circuit
1
, symbol
10
denotes a carrier-wave regenerating circuit to regenerate two reference carrier waves f
c1
(=cos&ohgr;t) and f
c2
(=sin&ohgr;t) orthogonal to each other with phases shifted from each other by 90° because a frequency and a phase synchronize with a carrier wave before modulated in inputs of the demodulating circuit
1
. Symbols
60
and
61
denote multipliers for multiplying an intermediate-frequency signal IF by f
c1
and f
c2
,
62
and
63
denote A/D converters for A/D-converting outputs of the multipliers
60
and
61
at a sampling rate two times larger than a symbol rate,
64
and
65
denote digital filters for applying band restriction to outputs of the A/D converters
62
and
63
through digital-signal processing,
66
and
67
denote thinning circuits for thinning outputs of the digital filters
64
and
65
to 1/2 sampling rate and outputting two series of I and Q base-band signals (I and Q symbol-stream data) showing instantaneous values of I-axis and Q-axis for each symbol. The thinning circuits
66
and
67
transmit two series of I and Q base-band signals I(
8
) and Q(
8
) (a numeral in parentheses denotes the number of quantization bits which is hereafter also simply referred to as I and Q) respectively having 8 quantization bits (two's complement system).
Mapping for each modulation system at the transmission side is described below by referring to FIGS.
13
(
1
) to
13
(
3
). FIG.
13
(
1
) shows signal point arrangements on I-Q phase plane (also referred to as I-Q vector plane or I-Q signal space diagram) when using 8PSK for a modulation system. The 8PSK modulation system transmits a three-bit digital signal (abc) by one symbol. Combinations of bits constituting the symbol include such eight ways as (000), (001), (010), (011), (100), (101), (110), and (111). These three-bit digital signals are converted into signal point arrangements “0” to “7” on transmission-side I-Q phase plane in FIG.
12
(
1
) and this conversion is referred to as 8PSK mapping.
In case of the example shown in FIG.
13
(
1
), bit string (000) is converted into signal point arrangement “0,” bit string (001) into signal point arrangement “1,” bit string (011) into signal point arrangement “2,” bit string (010) into signal point arrangement “3,” bit string (100) into signal point arrangement “4,” bit string (101) into signal point arrangement “5,” bit string (111) into signal point arrangement “6,” and bit string (110) into signal point arrangement “7.”
FIG.
13
(
2
) shows signal point arrangements on I-Q phase plane at the time of using QPSK for a modulation system. The QPSK modulation system transmits two-bit digital signal (de) by one symbol. Combinations of bits constituting the symbol include such four ways as (00), (01), (10), and (11). In the case of the example in FIG.
13
(
2
), bit string (00) is converted into signal point arrangement “1,” bit string (01) into signal point arrangement “3,” bit string (11) into signal point arrangement “5,” and bit string (10) into signal point arrangement “7.”
FIG.
13
(
3
) shows signal point arrangements at the time of using BPSK for a modulation system. The BPSK modulation system transmits one-bit digital signal (f) by one symbol. In case of the digital signal (f), bit (
0
) is converted into signal point arrangement “0” and bit (
1
) into signal point arrangement “4.” The relation between signal point arrangement and arrangement number is the same for various modulation systems on the basis of 8BPSK.
I-axis and Q-axis of QPSK and BPSK in a hierarchical transmission system coincide with I-axis and Q-axis of 8PSK.
When a phase of a carrier wave before modulated in inputs of the demodulating circuit
1
coincides with phases of reference carrier waves f
c1
and f
c2
regenerated by the carrier-wave regenerating circuit
10
, a phase of a received-signal point on I-Q phase plane according to reception-side I and Q base-band signals I(
8
) and Q(
8
) when receiving digital signals related to signal point arrangements “0” to “7” on I-Q phase plane at the transmission side coincides with that of the t

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