JPH05207080A - Modulator - Google Patents

Abstract

PURPOSE:To provide a wideband area with orthogonality without generating unrequited spurious. CONSTITUTION:A synthesizer 13 generates the frequency signal of each channel. A mixer 5 performs the multiplication of the frequency signal of a certain channel with P-channel data. A mixer 6 performs the multiplication of the output of a variable 90 deg. phase shifter with Q-channel data. Thereby, a four-phase orthogonal phase modulation wave signal of each channel can be sent out from an in-phase phase synthesizer 9. The unrequired spurious is not included in the signal. In parallel with such operation, a DC analog signal including an orthogonal phase error is formed by multiplying the output (IF signal) of a device 16 by that of a device 17 by a mixer 10, and eliminating a higher harmonic component included in the signal by a loop filter 11, also, the orthogonal phase error can be detected by taking correlation between the P-channel data and the Q-channel data by supplying to an EXOR circuit 14, and multiplying them by a multiplier 12, and the variable 90 deg. phase shifter 7 is controlled so as to set the error at zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulator used in digital communication, and more particularly to a 4-phase quadrature modulator.

[0002]

2. Description of the Related Art As is well known, in a four-phase quadrature phase modulator which forms multi-channel transmission modulation waves having different frequencies for each channel, orthogonality is maintained in all of the multi-channels, that is, orthogonality. Broadband is required. Therefore, in the past, for example, a configuration as shown in FIG. 2 was used to achieve a wide band of orthogonality.

In FIG. 2, P applied to the input terminal 1
The channel data is waveform-shaped by the low-pass filter (LPF) 3 and becomes one input of the mixer 5. Further, the Q channel data applied to the input terminal 2 is waveform-shaped by the low pass filter (LPF) 4 and becomes one input of the mixer 6.

On the other hand, the output of the local oscillator 31 is branched into two by the in-phase divider 32, one branch output becomes the other input of the mixer 5, and the other branch output is the 90 ° phase shifter 3.
The phase is shifted by 90 ° at 3 and becomes the other input of the mixer 6.

That is, the P channel data and the local oscillator 31
Of the Q channel data and the output of the local oscillator 31 phase-shifted by 90 ° are multiplied by the mixer 6 to perform quadrature phase modulation.

The outputs of both mixers are combined by the in-phase combiner 34 to form a four-phase modulated wave, which is multiplied by the output of the synthesizer 36 in the mixer 35 to form an IF signal having a frequency corresponding to the channel. This is subjected to spurious elimination processing by the band pass filter 37 and sent to the transmission stage.

As described above, in the conventional four-phase quadrature phase modulator, the 90 ° phase shifter 33 allows 90 degrees over a wide band.
It is very difficult to guarantee the 90 °, so 90 ° quadrature phase modulation is performed at a fixed frequency first, and then the desired frequency is set by the synthesizer 36 to support multiple channels while maintaining 90 ° quadrature modulation. To obtain a wide band output frequency.

[0008]

However, in the conventional four-phase quadrature modulator, it is unavoidable that spurious, which is an unwanted wave, is generated in the mixer 35 for widening the band, so that the band for removing this spurious is generated. Although it is necessary to provide the pass filter 37 at the output stage, spurious that enters the band cannot be removed, and spurious outside the band may not be sufficiently removed. That is, in the conventional four-phase quadrature modulator, there is a problem that spurious is always present in the modulator output, which adversely affects the line quality in some cases.

An object of the present invention is to provide a modulator capable of widening the band of orthogonality without generating unnecessary spurious.

[0010]

In order to achieve the above object, the modulator of the present invention has the following structure. That is, the modulator of the first invention is a modulator that performs four-phase quadrature phase modulation on P-channel data and Q-channel data whose waveforms have been shaped by a low-pass filter; this modulator is for each channel. A synthesizer for generating a frequency; a variable 90 ° phase shifter for performing a 90 ° phase shift operation on the output of the synthesizer according to a correction signal; a first mixer for multiplying the P channel data by the output of the synthesizer; A second mixer for multiplying the Q channel data and the output of the variable 90 ° phase shifter; and a four-phase quadrature by combining the output of the first mixer and the output of the second mixer. An in-phase phase synthesizer that outputs a phase-modulated wave signal; and a phase error detection circuit that detects a quadrature phase error and outputs the quadrature phase error as the correction signal are provided.

A modulator according to a second aspect of the present invention is the modulator according to the first aspect of the present invention; the phase error detection circuit is configured to multiply and output the output of the first mixer and the output of the second mixer. A loop filter that filters the output of the third mixer; an exclusive OR circuit that correlates the P-channel data and the Q-channel data; an output of the loop filter and the exclusive A multiplier that multiplies the output of the logical OR circuit and outputs the multiplication result as the correction signal;

[0012]

Next, the operation of the modulator of the present invention constructed as described above will be described. In the present invention, four-phase quadrature phase modulation for P-channel data and Q-channel data is directly performed for each channel using a synthesizer. At that time, the 90 ° phase shifter is a variable type and the quadrature phase error is 0. The variable 90 ° phase shifter is controlled so that

As a result, since the four-phase quadrature-phase modulated wave signal of each channel is directly formed, it is possible to prevent the generation of unnecessary spurious signals as in the conventional case. Further, since the variable 90 ° phase shifter is controlled to maintain the orthogonality at all times, it is possible to ensure the orthogonality of a wide band, and it is always possible to prevent the orthogonality fluctuation due to the temperature and the secular change during operation. Since the correction operation is performed, the orthogonal accuracy is well compensated.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a modulator according to an embodiment of the present invention. In FIG. 1, the P-channel data applied to the input terminal 1 is waveform-shaped by the low pass filter (LPF) 3 and becomes one input of the (first) mixer 5. Also, input terminal 2
Q-channel data applied to the low-pass filter (LP
The waveform is shaped by (F) 4 and becomes one input of the (second) mixer 6. The above is the same as the conventional one (FIG. 2).

On the other hand, the synthesizer 13 generates a frequency for each channel, but the frequency signal of a certain channel is branched into two by the in-phase phase distributor 8, one branch output becomes the other input of the mixer 5, and the other output. The branched output is phase-shifted by 90 ° by the variable 90 ° phase shifter 7 and becomes the other input of the mixer 6.

In short, the baseband data (P, Q) of each channel is quadrature-phase modulated and directly converted into an IF signal of a frequency corresponding to each channel.

The output of the mixer 5 (6) is branched into two by the in-phase phase divider 16 (17), and one of the branched outputs is combined by the in-phase phase combiner 9 into a four-phase quadrature modulated wave. Since there are no spurious factors in the above routes,
The output of the in-phase synthesizer 9 does not have spurious noise as in the conventional case. Therefore, the output of the in-phase synthesizer 9 is directly sent to the transmission stage (not shown).

Here, the variable 90 ° phase shifter 7 is controlled so that the phase shift operation is exactly 90 °, as will be described later, and therefore, for each channel which is the output of the in-phase synthesizer 9. The orthogonality of the four-phase quadrature-modulated wave is accurately maintained. The orthogonality compensating operation by the phase error detection circuit will be described below.

The other branch output of the in-phase phase divider 16 (17) becomes the input of the (third) mixer 10. Here, when the other branch output of the in-phase divider 16 is Pcos ω ₀ t, the quadrature phase error is θ, and the other branch output of the in-phase divider 17 is Q sin (ω ₀ t + θ), The output is given by Equation 1, but since the harmonic component included in the output of the mixer 10 is removed by the loop filter 11, the signal [(PQ / 2) sin θ] is input.

[0020]

## EQU1 ## Pcos ω ₀ t · Q sin (ω ₀ t + θ) = (PQ / 2) sin 2ω ₀ t cos θ + PQ sin θ {(1 + cos 2ω ₀ t) / 2}

On the other hand, the baseband channel data P and Q are signals that take ± 1 respectively. The correlation between the two is taken by the exclusive OR circuit 14, and the correlation result is the other of the multiplier 12. Will be input.

Thus, in the multiplier 12, the uncertain data component due to the P channel data and the Q channel data included in the output of the loop filter 11 is removed, and only the quadrature phase error θ which is the DC analog amount is corrected. It is given to the variable 90 ° shift phase shifter 7 as a signal.

In the variable 90 ° shift phase shifter 7, the multiplier 12
By receiving the quadrature phase error θ which is a correction signal from the quadrature phase, the operation phase shift amount with respect to the output of the synthesizer 13 is set so that the phase becomes a predetermined value of 90 ° or less when the quadrature phase error θ is on the + side. When the error θ is on the negative side, the phase is 90
It is variably set so that it becomes a predetermined value of ° or more. By the above correction operation, the quadrature phase error θ is controlled to be always 0.

[0024]

As described above, according to the modulator of the present invention, four-phase quadrature phase modulation of P channel data and Q channel data is directly performed for each channel by using a synthesizer. The ° phase shifter is a variable type, and the variable 90 ° phase shifter is controlled so that the quadrature phase error becomes zero.

Therefore, according to the present invention, 4 of each channel
Since the quadrature-phase modulated wave signal is directly formed, it is possible to prevent the generation of unnecessary spurious signals as in the conventional case. Further, since the variable 90 ° phase shifter is controlled to maintain the orthogonality at all times, it is possible to ensure the orthogonality of a wide band, and it is always possible to prevent the orthogonality fluctuation due to the temperature and the secular change during operation. Since the correction operation is performed, there is an effect that the orthogonal accuracy is favorably compensated.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a modulator according to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a conventional modulator.

[Explanation of symbols]

 1 Input Terminal 2 Input Terminal 3 Low Pass Filter 4 Low Pass Filter 5 Mixer 6 Mixer 7 Variable 90 ° Phase Shifter 8 In-phase Distributor 9 In-phase Synthesizer 10 Mixer 11 Loop Filter 12 Multiplier 13 Synthesizer 14 Exclusive OR circuit 16 In-phase phase distributor 17 In-phase phase distributor

Claims (2)

[Claims] 1. A modulator for performing four-phase quadrature phase modulation on P-channel data and Q-channel data waveform-shaped by a low-pass filter, wherein the modulator generates a frequency for each channel. A variable 90 ° phase shifter that performs an operation of shifting the output of the synthesizer by 90 ° according to a correction signal; a first mixer that multiplies the P-channel data by the output of the synthesizer;
A second mixer that multiplies the Q channel data and the output of the variable 90 ° phase shifter; and combines the output of the first mixer and the output of the second mixer to perform four-phase quadrature phase modulation. A modulator for outputting a wave signal; a phase error detection circuit for detecting a quadrature phase error and outputting it as the correction signal; 2. The modulator according to claim 1, wherein the phase error detection circuit includes a third mixer that multiplies the output of the first mixer and the output of the second mixer, and outputs the product.
A loop filter that filters the output of the third mixer; an exclusive OR circuit that correlates the P-channel data and the Q-channel data; an output of the loop filter and the exclusive-OR circuit And a multiplier that outputs the multiplication result as the correction signal, and a modulator;