JPH11331287A - Amplitude modulated wave elimination circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplitude modulated(AM) wave elimination circuit that extracts a digitally modulated wave by canceling the AM wave from an AM data multiplex modulated wave. SOLUTION: An AM data multiplex modulated wave is sampled by a sampling pulse with a frequency that is four times a carrier frequency, an A/D converter 4 applies A/D conversion to the sampled signal, to obtain a positive integer including m=0, and discrete output values that are A/D converted at (4m) sampling points and discrete output values that are A/D converted at (4m+1) sampling points are mutually interchanged in a sampling point interchanging circuit 5. Furthermore, discrete value outputs that are A/D converted at (4m+1) sampling points and discrete value outputs that are A/D converted at (4m+2) sampling points are interchanged An AM modulated wave by adding is eliminated the interchanged discrete value outputs and the discrete value outputs that are A/D converted by the A/D converter 4 in an adder 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an AM modulation wave removing circuit for removing an AM modulation wave from an AM data multiplex modulation wave generated by an AM data multiplex modulation device.

[0002]

2. Description of the Related Art An AM data multiplex modulation apparatus for multiplexing a digital modulation wave with an AM modulation wave so as not to affect the AM synchronous detection output is disclosed in Japanese Patent Application Laid-Open No. 9-326836.

[0003] An example in which the above-described conventional AM data multiplex modulation apparatus uses a QPSK (four-phase PSK) modulation method as a digital modulation method will be described with reference to FIG.

[0004] An analog signal wave such as an audio signal (hereinafter, also simply referred to as a signal) is supplied to an AM modulator 11, and a carrier having a frequency fc is AM-modulated by the signal wave. AM modulator 1
The AM modulated wave νAM (t) output from 1 is as follows, assuming that the amplitude of the carrier is 1, the angular frequency of the AM carrier is ωc (rad / s), the modulation is κ, and the signal wave is νm (t). It is expressed as in equation (1).

ΝAM (t) = ｛1 + κνm (t)｝ cos ωct t Equation (1)

The I and Q digital signal sequences generated by the QPSK baseband digital signal generator 12 are represented by In and Qn. Here, it is assumed that In = ± 1 and Qn = ± 1.

[0007] The output signal from the QPSK baseband digital signal generator 12 is input to a quadrature modulator 13 to which a carrier having a frequency (fc + fα) is supplied. Are orthogonally modulated. The output signal νDH (t) from the quadrature modulator 13 is as shown in the following equation (2).

ΝDH (t) = In cos (ωc + ωα) t + Qn sin (ωc + ωα) t Equation (2)

On the other hand, the QPSK baseband digital signal output from the QPSK baseband digital signal generator 12 is supplied to a sign inverter 14 where the sign is inverted (−).
In) and (-Qn). The QPSK baseband digital signal whose sign has been inverted in the sign inverter 14 is supplied to a complex conjugate unit 15 where the complex conjugate is obtained,
The sign of the Qn signal sequence of the SK baseband digital signal is inverted (-In) and converted to (Qn). That is, the sign of the component in phase with the reference carrier phase of the vector shift corresponding to the dibit formed by the QPSK baseband digital signal is inverted by the sign inverter 14 and the complex conjugate unit 15.

The complex signal sequence complex-conjugated by the complex conjugator 15 is input to a quadrature modulator 16 to which a carrier having a frequency (fc-fα) is supplied. ) (Rad / s) is quadrature-modulated. The output signal νDL (t) from the quadrature modulator 16 is as shown in the following equation (3).

ΝDL (t) = − In cos (ωc−ωα) t + Qn sin (ωc−ωα) t Equation (3)

The output signal νDH of the equations (2) and (3)
(t) and νDL (t) are added by the adder 17, and the digital modulation wave νD (t), which is the added output, is as shown in the following equation (4).

ΝD (t) = νDH (t) + νDL (t) = Incos (ωc + ωα) t + Qn sin (ωc + ωα) t−Incos (ωc−ωα) t + Qn sin (ωc−ωα) t Equation (4)

AM modulated wave νAM (t) and digital modulated wave νD
(t) is input to the adder 18 and added, and the AM data multiplex modulation wave ν (t) is as shown in the following expression (5) from the expressions (1) and (4).

Ν (t) = νAM (t) + νD (t) = ｛1 + κνm (t)｝ cos ωct + Incos (ωc + ωα) t + Qn sin (ωc + ωα) t−Incos (ωc−ωα) t + Qn sin (ωc− ωα) t ... Equation (5)

The AM data multiplex modulation process in the conventional AM data multiplex modulation wave device is as shown in FIG.
The AM modulated wave output from the AM modulator 11 is shown as a in FIG.
That is, the digital modulation wave is shown as b in FIG. 4, and the output signal from the quadrature modulator 13, that is, the digital modulation wave is shown as c in FIG. Adder 17
The digitally modulated wave output from FIG.
, And the AM data multiplex modulation wave output from the adder 18 is shown as d in FIG.

As described above, in the conventional AM data multiplex modulation apparatus, the position of the frequency (fc + fα) and the frequency (fc-f) which are line-symmetric with respect to the carrier fc on the frequency axis.
Since the digital modulation wave is multiplexed with the position of α),
When the AM data multiplex modulation wave is subjected to the AM synchronous detection, it does not affect the AM synchronous detection output.

[0018]

However, in the conventional modulation described above, a carrier having a frequency fc is converted to an analog signal wave by AM.
AM data multiplex modulation in which a digital modulation wave is multiplexed at a position of a frequency (fc + fα) and a position of a frequency (fc−fα), which are amplitude-modulated by a modulator, and are axisymmetric with respect to a carrier of a frequency fc on a frequency axis. In the AM data multiplex modulation wave modulated by the method, the AM modulation component and the data modulation component are multiplexed in the same frequency band and the same time,
It is not possible to extract desired digital data by selecting the time during which digital data is multiplexed, or to extract desired data by selecting a frequency band in which data is multiplexed.

According to the present invention, an AM data multiplex modulation wave
It is an object of the present invention to provide an AM modulation wave removing circuit that can cancel a modulation wave and extract a digital modulation wave.

[0020]

An AM modulated wave removing circuit according to the present invention AM-modulates a carrier having a frequency fc with an analog signal wave, and converts the carrier having a frequency fc on a frequency axis within a frequency band of the AM modulated wave. Frequency (fc +
An AM modulation wave removing circuit for removing an AM modulation wave from an AM data multiplex modulation wave obtained by multiplexing a digital modulation wave signal at a position of (fα) and a frequency (fc−fα). A / D conversion means for sampling with a sampling pulse having a frequency four times the carrier frequency and A / D converting the sampled signal;
= 0, 1, 2, 3,..., The A / D-converted discrete value output at the (4m) sampling point and (4m +
The A / D-converted discrete value output at the sampling point 3) is interchanged, and the A / D-converted discrete value output and (4m +
2) A sampling point exchange circuit for mutually exchanging the A / D converted discrete value output at the sampling point, and the discrete value output exchanged by the sampling point exchange circuit and A / D converted by the A / D conversion means. And an adder for adding the discrete value output.

In the AM modulated wave removing circuit according to the present invention,
The AM data multiplex modulation wave is sampled at a cycle four times the cycle of the carrier wave, and the sampled signal is A / D converted by an A / D converter. m = 0, 1, 2, 3,
..., at the sampling point of (4 m), A /
The D-converted discrete value output and the A / D-converted discrete value output at the (4m + 3) sampling point are interchanged, and the A / D-converted discrete value output at the (4m + 1) sampling point and ( At the sampling point of 4m + 2), the A / D-converted discrete value outputs are exchanged with each other, and the exchanged discrete value outputs and the A / D-converted discrete value outputs are added. . As a result, only the digital modulation wave is sampled by the sampling pulse and the A / D converted discrete output value is output from the addition output, and the AM modulation wave is removed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an AM modulated wave removing circuit according to the present invention will be described with reference to embodiments.

FIG. 1 shows A according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an M-modulated wave removing circuit.

In the AM modulated wave removing circuit according to one embodiment of the present invention, the input AM data multiplexed modulated wave is supplied to a carrier regenerator 1 to regenerate the AM modulated carrier,
The AM modulated carrier reproduced by the carrier regenerator 1 is supplied to a timing signal generator 2 to generate a timing signal for A / D conversion. For example, a timing signal having a frequency four times the frequency of the carrier is generated as a sampling pulse. On the other hand, the input AM data multiplex modulation wave is supplied to the delay unit 3 for delay, and the output from the delay unit 3 is A
The signal is supplied to the / D converter 4 and A / D converted at a timing based on the timing signal. The A / D conversion output output from the A / D converter 3 is an A / D conversion output obtained by performing A / D conversion at the sampling point (4m), where m = 0, 1, 2, 3,. The (discrete value output) and the A / D converted output A / D converted at the sampling point (4m + 3) are interchanged, and the A / D converted output A / D converted at the sampling point (4m + 1) is (4m +
A / D converted at the sampling point 2)
The conversion output is supplied to a sampling point exchange circuit 5 for exchanging the A / D conversion output.
The A / D conversion output from the / D converter 4 and the output from the sampling point exchange circuit 5 are supplied to an adder 6, added, and transmitted.

The AM data multiplex modulation wave ν of the above equation (5)
(t) can be transformed as shown in the following equation (6).

Ν (t) = ｛1 + κνm (t)｝ cos ωct + Incos (ωc + ωα) t + Qn sin (ωc + ωα) t−Incos (ωc−ωα) t + Qn sin (ωc−ωα) t = ｛1 + κνm (t) ｝ Cos ωct −2In sinωct sinωαt + 2Qn cosωαt sinωct ... Equation (6)

Where ωα is the digitally modulated carrier and AM
The angular frequency (rad / s) of the difference from the modulation carrier, and the digital modulation carrier has a frequency f in the upper and lower sidebands of the AM modulation carrier.
α is present at the target position. Also, fc≫fα.

In the AM modulated wave removing circuit according to the embodiment of the present invention shown in FIG. 1, the AM data multiplexed modulated wave represented by the above equation (6) is input to the carrier regenerator 1 and the delay unit 3. Is done.

The input AM data multiplex modulation wave signal ν
(t) is input to the carrier regenerator 1 and the delay unit 3.
First, carrier wave reproduction by the carrier regenerator 1 will be described. What is reproduced by the carrier regenerator 1 is a carrier wave for AM modulation, and the output vc from the carrier regenerator 1
(t) is as shown in the following equation (7).

Νc (t) = cosωct Equation (7)

Next, the signal νc (t) is input to the timing signal generator 2 to generate a timing signal for A / D conversion. Here, the phase of the single frequency signal νc (t) is (π / 4) radian, (3π / 4) radian, (5π
A timing signal is output at / 4) radians and (7π / 4) radians. That is, when the time t is represented by the following equation (8), the A / D converter 4 generates a timing signal such that the AM data multiplex modulation wave signal ν (t) is sampled.

T = 1 + 2m / 8fc Expression (8) Here, m = 0, 1, 2, 3,... At this time, the sampling frequency is 4fc (Hz).

On the other hand, the AM data multiplex modulation wave ν (t) is transmitted by the delay unit 3 after being delayed by the sum of the delay amounts of the carrier regenerator 1 and the timing signal generator 2.
Here, for simplicity, each delay is not taken into account, and the delay amount of the delay unit 3 is set to 0. Therefore, the signal output from the delay unit 3 is an AM data multiplex modulation wave ν
(t), and is input to the A / D converter 4 and is sampled by the timing signal generated by the timing signal generator 2.

Therefore, the AM data multiplex modulation wave signal ν
(t) is sampled by a sampling pulse having a sampling frequency of 4fc (Hz), and the A / D converter 4
Are A / D converted.

Therefore, the discrete output signal νD (m) output from the A / D converter 4 is as shown in the following equation (9).

ΝD (m) = {1 + Kνm (t)} cos2πfc (1 + 2m) / 8fc−In {sin2πfc (1 + 2m) / 8fc} {sin2πfα (1 + 2m) / 8fc} + Qn {sin2πfc (1 + 2m) / 8fcπco 1 + 2m) / 8fc} = {1 + Kνm (t)} cos (1 + 2m) π / 4−In sin (1 + 2m) π / 4 · sin (1 + 2m) πfα / 4fc + Qn sin (1 + 2m) π / 4 · cos (1 + 2m) πfα / 4fc = {1 + Kνm (t)} cos (1 + 2m) π / 4 + [− Insin (1 + 2m) πfα / 4fc + Qncos (1 + 2m) πfα / 4fc] · sin (1 + 2m) π / 4 Equation (9)

Next, an exchange process of the sampling point exchange circuit 5 will be described. Here, m = 0 ← → m =
3, m = 1 ← → m = 2, m = 4 ← → m = 7, m = 5 ← →
m = 6,... Here, ← → indicates that they are interchanged. That is, m = 0, 1,
2, 3, ..., and the sampling point is (4m) ← → (4m +
3), (4m + 1) ← → (4m + 2).

Here, ｛1 + Kνm in equation (9)
(t)｝ and [-In sin (1 + 2m) πfα / 4fc + Qn
cos (1 + 2m) πfα / 4fc] is cos (1 + 2m) π / 4 and sin (1 + 2m) depending on the condition of fc≫fα.
Since the change is much slower than π / 4, it can be considered that the value does not change even if the sampling points are exchanged.

Further, cos (1 + 2m) π in equation (9)
/ 4 and sin (1 + 2m) π / 4 are obtained as m = 0, 4, 8,.
, Cos (1 + 2m) π / 4 = 1 / √2, sin (1
+ 2m) π / 4 becomes 1 / √2, and m = 1, 5, 9,
..., cos (1 + 2m) π / 4 = 1 / √2, sin
(1 + 2m) π / 4 becomes −1 / √2, and m = 2,
In the case of 6, 10, ..., cos (1 + 2m) π / 4 = -1
/ √2, sin (1 + 2m) π / 4 becomes −1 / √2, and when m = 3, 7, 11,..., Cos (1 + 2m)
π / 4 = -1 / √2, sin (1 + 2m) π / 4 = 1 /
√2.

Therefore, the above (m = 0 ← → m = 3, m
= 1 → m = 2, m = 4 ← → m = 7, m = 5 ← → m =
By replacing the sampling points of 6, ...,), cos
Only (1 + 2m) π / 4 changes sign, and sin (1 + 2
m) Since the sign of π / 4 does not change, the output of the sampling point exchange circuit 5 is as shown in the following equation (10).

− {1 + Kνm (t)} cos (1 + 2m) π / 4 + [− In sin (1 + 2m) πfα / 4fc + Qncos (1 + 2m) πfα / 4fc] · sin (1 + 2m) π / 4 (10)

Here, the fact that the value does not change even if the sampling points are exchanged will be described with reference to the schematic diagram shown in FIG.

FIG. 2A is an enlarged view of the amplitude in the amplitude direction.
{1 + Kνm (t)} changes as shown in FIG. 2 and expands in the amplitude direction as compared with the actual case, as shown in FIG.
n (1 + 2m) πfα / 4fc + Qn cos (1 + 2m) π
fα / 4fc] changes. On the other hand, cos (1 + 2
m) π / 4 changes as shown in FIG.
+ 2m) π / 4 changes as shown in FIG. FIG. 2 (e) shows sampling points, 0, 1, 2, 3,.
It is numbered.

As shown in FIG. 2E, the sampling points of the AM data multiplex modulation wave signal ν (t) are interchanged. As shown in FIG.
The change of Kνm (t)｝ is small, and as a result, even if the replacement is performed, the value hardly changes, as shown in FIG. Also, as shown in FIG. 2B, [−In sin (1+
2m) πfα / 4fc + Qn cos (1 + 2m) πfα /
4fc] is small, and as a result, the value hardly changes even if the replacement is performed, as shown in FIG. 2 (g).

On the other hand, -cos (1 + 2m) π / 4 changes as shown in FIG. 2 (h), and sin (1 + 2m) π /
4 changes as shown in FIG. cos (1 + 2
m) The sign of (−) for π / 4 is as described above.

Next, the output from the A / D converter 4 shown in the equation (8) and the output of the sampling point exchange circuit 5 shown in the equation (10) are added in the adder 6, and the output from the adder 6 is obtained. The output is as shown in the following equation (11).

2 [−In sin (1 + 2m) πfα / 4fc + Qncos (1 + 2m) πfα / 4fc] · sin (1 + 2m) π / 4 Equation (11)

The output from the adder 6 shown in the equation (11) uses only the digital modulation wave as the sampling frequency of 4fc (Hz).
This is the signal sampled at. Therefore, a signal obtained by removing the AM modulated wave from the AM data multiplexed modulated wave is output from the adder 6, and baseband digital data can be demodulated from this signal.

[0049]

As described above, the AM according to the present invention is described.
According to the modulation wave removing circuit, the AM modulation wave can be removed from the AM data multiplex modulation wave with a simple configuration and a small-scale configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an AM modulated wave removing circuit according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an operation of the AM modulated wave removing circuit according to the embodiment of the present invention;

FIG. 3 is a block diagram illustrating a configuration of an AM data multiplex modulation apparatus.

FIG. 4 is a schematic diagram for explaining an AM data multiplex modulation wave;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carrier regenerator 2 Timing signal generator 3 Delayer 4 A / D converter 5 Sampling point replacement circuit 6 Adder

Claims (1)

[Claims] An analog signal wave having a frequency fc and a carrier wave of A
M-modulated, and a frequency (fc + f
α) and an AM modulation wave removing circuit for removing an AM modulation wave from an AM data multiplex modulation wave obtained by multiplexing a digital modulation wave signal at a position of a frequency (fc−fα),
A / D conversion means for sampling the AM data multiplex modulation wave with a sampling pulse having a frequency four times the carrier frequency and A / D converting the sampled signal;
, 0, 1, 2, 3,..., The A / D converted discrete value output at the (4m) sampling point and (4m +
The A / D-converted discrete value output at the sampling point 3) is interchanged, and the A / D-converted discrete value output and (4m +
2) A sampling point exchange circuit for mutually exchanging the A / D converted discrete value output at the sampling point, and the discrete value output exchanged by the sampling point exchange circuit and A / D converted by the A / D conversion means. And an adder for adding the discrete value output.