JP3447646B2 - Digital signal transmission device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal transmitter for modulating a quadrature carrier signal with a digital baseband signal and transmitting a carrier digital signal, and more particularly to generation of a quadrature carrier signal.

[0002]

2. Description of the Related Art A conventional technique will be described below with reference to the drawings. FIG. 7 is a block diagram for explaining the configuration of the most basic conventional first digital signal transmitting apparatus. In the configuration shown in FIG. 7, since the frequency of the carrier digital signal output 730 and the frequency of the oscillation output signal 7200 of the local oscillator 720 are equal, the carrier digital signal output is feedback-coupled to the local oscillator, and its oscillation output is generated. Signal 72
00, and the phase of the carrier signal is affected, so that the modulation accuracy deteriorates. In order to prevent this, it is necessary to shield the entire digital signal transmission device with a metal.

FIG. 8 is a block diagram for explaining the configuration of the second conventional digital signal transmitting apparatus. In the configuration shown in FIG. 8, two local oscillators 820 and 821 are provided.
The frequency of the oscillation output signal and the frequency of the carrier digital signal output are made different from each other to solve the problem of the influence of the feedback coupling on the phase of the oscillation output signal of the local oscillator. However, in this case, two local oscillators are needed. In addition, the frequency conversion unit 8
A bandpass filter 823 is required to remove the image signal generated at 22. Further, in the frequency conversion unit 822, a spurious signal is generated due to the non-linearity.

Digital mobile phone PDC (Person)
In the case of the al Digital Cellular method, the frequencies of the oscillation output signals of the two local oscillators 820 and 821 are, for example, 135 MHz and 795 M.
Hz is used, and the frequency of the carrier digital signal output is 93
It is 0 MHz. In this case, 94 times 7 times of 135MHz
Frequency 91 of 5 MHz and twice the difference of 795 MHz (1590 MHz) and 5 times of 135 MHz (675 MHz)
Spurious signals are generated at 5 MHz, and the frequency of these spurious signals and the frequency of the carrier digital signal output (9
(30 MHz) is small, and the filter circuit may not be able to remove it sufficiently, which causes a problem of interference with the carrier digital signal output and the frequency of the adjacent transmission channel.

As a solution to these problems, a digital signal transmitting apparatus disclosed in Japanese Patent Laid-Open No. 10-4437 has been proposed. FIG. 5 is a block diagram illustrating the configuration of this digital signal transmitting apparatus. In this digital signal transmitting apparatus, the frequency fosc of the oscillation output signal 5200 of the local oscillator 520 is set to “4/3” times the frequency fout of the carrier digital signal output 530, and the oscillation output signal 5 of the local oscillator 520 is generated.
The frequency conversion unit 540 generates a signal having a frequency difference between these two signals from the signal 200 and a signal 5201 obtained by dividing the frequency by 200, and the frequency signal is further doubled by the frequency doubler circuit 560. , A divide-by-2 and 90-degree phase shift circuit 5 composed of a master-slave type D flip-flop circuit 5
At 70, the quadrature carrier signals 5700 and 5701 are obtained, and the quadrature carrier signal is quadrature-modulated with the digital baseband signal. At this time, the frequency conversion unit 54
At 0, at the same time as the frequency (3/4) fosc, the frequency fosc is
Since an image signal having a frequency of "5/4" times that of the
I try to remove it at 50. With such a configuration, the frequency fout of the carrier digital signal output and the frequency fosc of the oscillation output signal of the local oscillator are different, and the influence of the feedback coupling described above is eliminated.
Further, due to the non-linearity of the frequency conversion unit 540, the frequency of the spurious signal generated becomes equal to the frequency of the carrier digital signal output, so that the problem of interference action does not occur. FIG. 6 shows the frequencies of the signals at the respective points in FIG.

[0006]

However, in the above-described digital signal transmitter of FIG. 5, it is necessary to provide a bandpass filter at the output section of the frequency conversion section in order to remove the image signal. As this bandpass filter, a SAW filter, a multilayer ceramic filter, or the like is used, and there is a problem that a large area is required for mounting.

Further, in order to obtain a quadrature carrier signal, the signal after frequency conversion is once doubled, so that there is a problem that the frequency becomes high and power consumption increases.

[0008]

In order to solve the above-mentioned problems, a digital signal transmitting apparatus according to the present invention generates a digital signal generator for generating a digital baseband signal and two quadrature carrier wave signals having 90 ° different phases. A quadrature carrier signal generating unit, a quadrature modulation unit that quadrature modulates the quadrature carrier signal with the digital baseband signal and outputs a carrier digital signal, and the quadrature carrier signal via the bandpass filter and an amplifier circuit. In a digital signal transmitting device having a transmitting section for transmitting and outputting from an antenna,
The quadrature carrier signal generator generates a local oscillator that outputs an oscillation output signal having a predetermined oscillation frequency, and a first oscillator and a second oscillator that divide the oscillation output signal by two and have a phase difference of 90 degrees.
And a second frequency divider / phase-shift circuit for outputting the frequency-divided signal and a second frequency-dividing circuit for dividing the oscillation output signal by four and outputting third and fourth frequency-divided signals having different 90-degree phases. From the frequency divider / phase shift circuit and the first, second, third and fourth frequency divided signals, the frequency is the frequency of the first and second frequency divided signals and the frequency of the third and fourth frequency divided signals. The image rejection mixer circuit outputs two quadrature carrier signals having the 90-degree phases different from each other, which is the sum of the frequencies of the signals.

The first frequency dividing / phase shifting circuit is
Of the master-slave D flip-flop circuit, and the second frequency dividing / phase-shifting circuit is formed by connecting the second and third master-slave D flip-flop circuits in series. .

Alternatively, in the second frequency divider / phase shift circuit, the first master / slave type D flip-flop circuit is also used as the second master / slave type D flip-flop circuit. I did it.

In another digital signal transmitter of the present invention, a direct connection circuit and a frequency doubling circuit are provided in parallel between the first frequency dividing / phase shifting circuit and the local oscillator, The switch circuit selects either the oscillation output signal of the local oscillator or a signal obtained by doubling the oscillation output signal and supplies it to the first frequency dividing / phase shifting circuit to output two types of carrier signal output frequencies. Is configured to be selectively used.

Here, the oscillation frequency of the local oscillator is set to a frequency that is four thirds (= 4/3) times the required frequency of the carrier digital signal output from the transmitter.

Further, in the other digital signal transmitting apparatus of the present invention, when the oscillation output signal of the local oscillator is supplied to the first frequency dividing / phase shifting circuit by the switch circuit, the quadrature carrier signal is supplied. The frequency of
Three quarters of the oscillation output signal frequency of the local oscillator
(= 3/4) times the frequency, and when the switching circuit supplies a signal obtained by doubling the oscillation output signal of the local oscillator to the first frequency dividing / phase shifting circuit, the frequency of the orthogonal carrier wave signal is supplied. Is set to 5/4 (= 5/4) times the oscillation output signal frequency of the local oscillator.

Further, the image rejection mixer circuit includes four multipliers for generating multiplication signals between the first and second frequency-divided signals and the third and fourth frequency-divided signals. An adder that adds two signals of the multiplication signals of the four multipliers to generate one carrier signal of the two orthogonal carrier signals, and the remaining two signals of the multiplication signals. And a subtracter for generating the other carrier signal of the two orthogonal carrier signals by performing a subtraction process.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram illustrating the configuration of a digital signal transmitting apparatus according to the first embodiment of the present invention.

The digital signal transmitting apparatus of FIG. 1 includes a digital signal generator 1 for generating a digital baseband signal.
And a quadrature carrier signal generation unit 2 for generating two quadrature carrier signals having different 90-degree phases, and a quadrature modulator for quadrature modulating the quadrature carrier signal with the digital baseband signal and outputting a carrier digital signal 300. 3 and a transmitter 4 for transmitting and outputting the carrier digital signal 300 from an antenna via a bandpass filter and an amplifier circuit, and the quadrature carrier signal generator 2 includes [4 / 3] times the oscillation frequency fo
The local oscillator 20 which sends out the oscillation output signal 200 of sc and the first oscillator which divides the oscillation output signal 200 by 2 and outputs the first and second divided signals 210 and 211 which are different in phase by 90 degrees. The frequency division / phase shift circuit 21 and the second frequency division / phase shift circuit 24 which divides the oscillation output signal 200 into four and outputs third and fourth frequency division signals 230 and 231 having different phases by 90 degrees. From the first, second, third and fourth frequency-divided signals 210, 211, 230 and 231, the frequency is the frequency of the first and second frequency-divided signals ([1/2] fos
c) and the frequency of the third and fourth divided signals ([1/4]
fosc) and sum frequency ([1/2] fosc + [1/4]
The image rejection mixer circuit 25 outputs the two quadrature carrier signals 250 and 251 having different 90-degree phases, where fosc = [3/4] fosc).

Here, the first frequency dividing / phase shifting circuit 21
Is composed of a first master-slave D flip-flop circuit, and the second frequency-dividing / phase-shifting circuit 24 is composed of second and third master-slave D-flip-flop circuits 22 and 23 in series. I am trying to connect and configure.

Further, the image removing mixer circuit 25
Are four multiplications that generate multiplication signals 260, 270, 280 and 290 between the first and second divided signals 210 and 211 and the third and fourth divided signals 230 and 231 respectively. Carrier 26, 27, 28, 29 and one of the two quadrature carrier signals by adding processing of two signals of the multiplication signals of the four multipliers.
And a subtracter 51 that subtracts the remaining two signals of the multiplication signal to generate the other carrier signal 251 of the two orthogonal carrier signals. There is.

Here, the image removal mixer circuit 25
The contents of the signal processing in the above will be described. 2 for simplicity
With π [1/4] fosc · t = α, the first and second divided signals are sin (2 · α) and cos (2 · α).
If the third and fourth frequency-divided signals are represented by sin (α) and cos (α), the first multiplier 2
In 6, as the product of the first divided signal and the third divided signal,
sin (2 · α) · sin (α) = signal 260 is the second
In the multiplier 27 of, cos (2 · α) · cos (α) = signal 27 is obtained as a product of the second divided signal and the fourth divided signal.
0 is the product of the first divided signal and the fourth divided signal in the third multiplier 28, sin (2 · α) · cos
(Α) = the signal 280 is the product of the second frequency-divided signal and the third frequency-divided signal in the fourth multiplier 29.
α) · sin (α) = signal 290 is generated respectively.
In the adder 50, the signal 280 and the signal 290 are subjected to addition processing, and sin (2 · α + α) = sin (3 · α) is the signal 2
50, and the subtracter 51 subtracts the signal 260 from the signal 270 to obtain cos (2 · α + α) = c
os (3 · α) is generated as the signal 251. Here, the oscillation output signal frequency fosc of the local oscillator
Is set to [4/3] times the required frequency fout,
3 · α is 2π · [3/4] fosc · t = 2π · fout · t
Thus, the signals 250 and 251 are quadrature carrier signals of frequency [3/4] fosc = fout, each having a phase difference of 90 degrees.

At this time, each of the multipliers 26 and 27
Since the image signal of the difference frequency generated in 28 and 29 has been removed from the output, bandpass to the outside
No filter is needed. The frequency of the signal at each location is shown in FIG.

Next, the configuration of the digital signal transmitting apparatus according to the second embodiment of the present invention will be described with reference to FIG. Figure 2
In FIG. 1, the second master / slave type D flip-flop circuit 22 forming the second frequency dividing / phase shifting circuit 24 and the first frequency dividing / phase shifting circuit 21 constituting the first frequency dividing / phase shifting circuit 21 are described. The first master-slave D flip-flop circuit is also configured to be used in common.
As a result, the second master / slave type D flip-flop circuit 22 of the frequency dividing / phase shifting circuit 24 can be eliminated.

Next, a digital signal transmitting apparatus according to the third embodiment of the present invention will be described. FIG. 3 is a block diagram for explaining the configuration of the digital signal transmitting apparatus according to the third embodiment.

The difference between the digital signal transmitting apparatus according to the third embodiment and the digital signal transmitting apparatus shown in FIG. 1 lies between the first frequency dividing / phase shifting circuit 21 and the local oscillator 20. , Direct connection circuit 52 and frequency doubling circuit 5
3 is provided in parallel, and the oscillation output signal 20 of the local oscillator 20 is provided by the switch circuits SW1 and SW2.
By selecting either 0 or a signal 530 obtained by doubling it and supplying it to the first frequency dividing / phase shifting circuit 21, two types of carrier signal output frequencies can be selectively used. This is the point of configuration.

In the configuration of FIG. 3, when the switch circuit SW1 is turned on and SW2 is turned off, the frequencies of the quadrature carrier signals 250 and 251 are oscillated by the local oscillator 20 as in the configuration of FIG. Output signal 20
The frequency is [3/4] times the frequency fosc of 0, and SW
Orthogonal carrier signal 2 when 1 is off and SW2 is on
The frequency of 50 · 251 is [5/4] times the frequency fosc of the oscillation output signal 200 of the local oscillator 20.

[0026]

As described above, the digital signal transmitting apparatus of the present invention has the oscillation frequency fosc of the local oscillator.
And the frequency fout of the digital carrier output signal is fout
= [3/4] fosc, so that the carrier digital signal output transmitted from the antenna is not feedback-coupled to the local oscillator and does not adversely affect its phase. The effect is that the two types of local oscillators that were used can be reduced to one.

Further, since the image removing mixer circuit is used in the quadrature carrier signal generating section, it is not necessary to double the carrier signal, so that the power consumption can be reduced and the image signal removing band which has been conventionally required. Since no pass filter is required, the circuit area can be reduced when mounting. Furthermore, since it is not necessary to use a bandpass filter whose band is fixed, there is an effect that the carrier signal frequency can be easily switched.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of a digital signal transmission device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a digital signal transmission device according to a second embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a digital signal transmission device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing frequencies of signals at respective points of the digital signal transmitting apparatus of FIG.

FIG. 5 is a block diagram illustrating a conventional digital signal transmission device described in Japanese Patent Laid-Open No. 10-4437.

FIG. 6 is a diagram showing frequencies of signals at respective points in the digital signal transmitting apparatus of FIG.

FIG. 7 is a block diagram illustrating a first conventional digital signal transmission device.

FIG. 8 is a block diagram illustrating a second conventional digital signal transmission device.

[Explanation of symbols]

1 Digital Signal Generator 2 Quadrature Carrier Signal Generator 3 Quadrature Modulator 4 Transmitter 20 Local Oscillator 21 First Frequency Dividing / Phase Shifting Circuit and First Master
Slave type D flip-flop circuit 22 second master / slave type D flip-flop circuit 23 third master / slave type D flip-flop circuit 24 second frequency dividing / phase shifting circuit 25 image removing mixer circuit 26, 27, 28, 29 Multiplier 50 Adder 51 Subtractor 52 Direct connection circuit 53 Frequency doubler circuit 200 Oscillation output signals 210, 211 First and second divided signals 230, 231 Third and fourth divided signal 250 , 251 Orthogonal carrier signal 300 Carrier digital signal

Claims (7)

(57) [Claims] 1. A digital signal generator for generating a digital baseband signal, a quadrature carrier signal generator for generating two quadrature carrier signals having different 90-degree phases, and the quadrature carrier signal for the digital baseband signal. A quadrature modulation unit that outputs a carrier digital signal by quadrature modulation with
In a digital signal transmission device comprising a transmission section for transmitting and outputting the carrier digital signal from an antenna via a bandpass filter and an amplification circuit, the quadrature carrier signal generation section transmits an oscillation output signal of a predetermined oscillation frequency. A local oscillator, a first frequency dividing / phase shifting circuit which divides the oscillation output signal by two and outputs first and second frequency dividing signals having phases different by 90 degrees, and the oscillation output signal by 4 A second frequency dividing / phase shifting circuit for dividing and outputting third and fourth frequency dividing signals having different phases by 90 degrees; and the first, second, and third circuits.
And from the fourth frequency-divided signal, the frequencies are
And an image rejection mixer circuit that outputs the two quadrature carrier signals having the 90-degree phases different from each other, which is the sum frequency of the frequency of the frequency-divided signal and the frequencies of the third and fourth frequency-divided signals. A digital signal transmission device characterized by: 2. The first frequency dividing / phase shifting circuit is composed of a first master / slave type D flip-flop circuit, and the second frequency dividing / phase shifting circuit is a second and a third phase shifting circuit. The digital signal transmitting apparatus according to claim 1, wherein the master-slave type D flip-flop circuit is connected in series. 3. In the second frequency divider / phase shift circuit, the first master / slave D flip-flop circuit is also used as the second master / slave D flip-flop circuit. The digital signal transmitting apparatus according to claim 2, wherein 4. A direct connection circuit and a frequency doubling circuit are provided in parallel between the first frequency dividing / phase shifting circuit and the local oscillator, and an oscillation output of the local oscillator is provided by a switch circuit. 3. A signal or a signal obtained by multiplying it by 2 is selected and supplied to the first frequency dividing / phase shifting circuit.
The described digital signal transmission device. 5. The frequency of the oscillation output signal of the local oscillator is set to be four thirds (= 4/3) times the required frequency of the carrier digital signal output from the transmission unit. The digital signal transmitting apparatus according to claim 1, 2, or 3. 6. The digital signal transmitting apparatus according to claim 4, wherein when the oscillation output signal of the local oscillator is supplied to the first frequency dividing / phase shifting circuit by the switch circuit, the quadrature carrier signal The frequency is set to three quarters of the oscillation output signal frequency of the local oscillator.
(= 3/4) times the frequency, and when the switching circuit supplies a signal obtained by doubling the oscillation output signal of the local oscillator to the first frequency dividing / phase shifting circuit, the quadrature carrier signal The frequency is 5/4 (= 5/4) of the oscillation output signal frequency of the local oscillator.
A digital signal transmitting device characterized by being doubled. 7. The four multipliers, wherein the image rejection mixer circuit generates a multiplication signal between each of the first and second divided signals and each of the third and fourth divided signals, An adder that adds two signals of the multiplication signals of the four multipliers to generate one carrier signal of the two orthogonal carrier signals, and the remaining two signals of the multiplication signals. And a subtracter for performing a subtraction process to generate the other carrier signal of the two orthogonal carrier signals. The described digital signal transmission device.