JPH0831886B2 - Transmitter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter used for digital mobile communication and the like.

2. Description of the Related Art A four-phase phase modulation method is known as a transmitter in digital mobile communication. For example, in 1988, National Institute of Electronics, Information and Communication Engineers Autumn Meeting B-448, a roll-off QPSK high power efficiency transmission system to which the LINC format is applied is shown. In addition, IEICE Technical Report CS-86 (September 1986)
(Mon) describes the multi-wavelength modulation resistant method QPSK-RZ in detail.

FIG. 3 shows an example of the configuration of a conventional four-phase phase modulation type transmitter, and FIG. 4 is an explanatory diagram showing the main signals in the transmitter of FIG. 3 as vectors.

In FIG. 3, 1 is a transmission signal input terminal to which a serial data signal to be transmitted is applied, and 2 is a dual system in which the data retention time of the serial data signal input to the transmission signal input terminal 1 is doubled. The serial / parallel converters 3, 4 for converting the four-phase phase-modulated symbol data signals into the four-phase phase-modulated symbol data signals of the two-system four-phase phase-modulated symbol data signals converted by the serial-parallel converter 2 are respectively band-limited. Low-pass filter 5 for obtaining four-phase phase-modulated baseband signals I (t) and Q (t) is an arithmetic circuit, and low-pass filters 3 and 4
By the two-system four-phase phase modulation baseband signals I (t) and Q (t) obtained by the above, the envelope signal R (t) R (t) = (I (t) of the four-phase phase modulation baseband signal ² + Q (t) ² ) ^1/2 and the modulation phase φ (t) φ (t) = tan ⁻¹ (Q (t) / I (t)), and the maximum value of the envelope signal R (t). Using a constant A having a value equal to or greater than 1/2, the in-phase component I of the first modulation signal having a modulation phase of φ ₁ (t) = φ (t) −cos ⁻¹ (R (t) / 2A) ₁ (t) = Acos (φ ₁ (t)) and orthogonal component Q ₁ (t) = Asin (φ ₁ (t)), and φ ₂ (t) = φ (t) + cos ⁻¹ (R (t) / 2A) phase component of the second modulation signal having a composed modulation phase _{I 2 (t) = Acos (} φ 2 (t)) and quadrature component _{Q 2 (t) = Asin (} φ 2 (t)) to calculate the Circuit.

Reference numeral 6 is a quadrature modulator that performs four-phase phase modulation by the in-phase component I ₁ and the quadrature component Q ₁ of the _first modulation signal calculated by the calculation circuit 5, and 7 is the second modulation signal calculated by the calculation circuit 5. Of the in-phase component I ₂ and the quadrature component Q ₂ for quadrature phase modulation, 8 and 9 are class C amplifiers for amplifying the signals quadrature phase modulated by the quadrature modulators 6 and 7, and 10 is
This is a power combiner for vector-combining the signals amplified by the class-C amplifiers 8 and 9 and sending them as radio waves via the antenna 11.

Next, the operation of the conventional example will be described with reference to FIGS. 3 and 4.

Assuming that a signal indicated by a vector is transmitted from the antenna 11 as shown in FIG. 4 with respect to the data signal applied to the transmission signal input terminal 1, the vector is composed of the vectors ₁ and ₂ having the same absolute value. , And the vectors ₁ and ₂ are selected such that MAX || ≦ 2 | ₁ | = 2 | ₂ |.

Therefore, if the vectors ₁ and ₂ are the output signals of the class C amplifiers 8 and 9 of FIG. 3, respectively, the vectors are combined by the power combiner 10 and sent out from the antenna 11. Therefore, the 4-phase phase modulated signal of constant amplitude output from the quadrature modulator 6 and 7 respectively vectors _{1, 2}
And the gain of the class C amplifiers 8 and 9 is G, the following relation ₁ = G · ₁ , ₂ = G · ₂ holds. Further, as shown in FIG. 4, | ₁ | = | ₂ | = A.

Vectors ₁ and ₂ are the in-phase component I ₁ and the quadrature component of the first modulated signal calculated by the calculation circuit 5, respectively.
Q ₁ and the in-phase component I ₂ and the quadrature component Q ₂ of the second modulation signal are obtained by quadrature phase modulation by the quadrature modulators 6 and 7, respectively. Therefore, the phases of the vectors ₁ and ₂ change according to the modulation pattern according to the transmission data. Here, the vector _{1, 2,} since it is a constant amplitude, as described above, vector ₁ was amplified by class-C amplifiers 8,9,
₂ is a constant multiple of vectors ₁ and ₂ .

Therefore, in the above-mentioned conventional example, the 4-phase phase modulation signal whose band is limited in the baseband signal can be amplified and transmitted by the class C amplifiers 8 and 9 while maintaining the band limiting effect.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional transmission device, the in-phase component I ₁ of the first modulation signal, the quadrature component Q ₁ , the in-phase component I ₂ of the second modulation signal, and the quadrature component Q ₂ make four-phase Since phase modulation and class C amplification are performed, output signals of the class C amplifiers 8 and 9 (vector ₁ ,
_When the phase difference of ₂ ) increases according to the modulation pattern,
There is a problem that the power loss of the power combiner 10 for vector-synthesizing these signals increases, and the power efficiency of the entire transmission device decreases.

In view of the above conventional problems, it is an object of the present invention to provide a transmission device capable of reducing the power loss of a power combiner and improving the overall power efficiency.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a first calculating means for calculating an in-phase component and a quadrature component of a first modulated signal and an in-phase component and a quadrature component of a second modulated signal. In addition, the in-phase component and the quadrature component of the first modulation signal and the in-phase component and the quadrature component of the second modulation signal are used to reduce the loss when vector-combining the modulation signals of the two systems in the power combiner. Second in-phase components of the first modulation signal are provided, and second in-phase components of the in-phase component and the quadrature component of the third modulation signal and the in-phase component and the quadrature component of the fourth modulation signal of the selected predetermined modulation phase difference are provided. And whether or not the modulation phase difference between the in-phase component and the quadrature component of the quadrature component and the quadrature component is larger than the predetermined modulation phase difference. Select the modulation signal of 2 Note 2
Selecting the third and fourth modulated signals of the arithmetic circuit, and applying bias voltages to the first and second C so that the amplitudes of the signals amplified by the first and second class C amplifiers become constant. It is designed to be supplied to a class amplifier.

Effect of the Invention With the above-described configuration, the present invention prevents the power loss of the power combiner because the phase difference between the signals input from the first and second class C amplifiers to the power amplifier does not exceed a predetermined value and the amplitude is constant. It can be reduced and thus the overall power efficiency can be improved.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a transmitting apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing main signals in the transmitting apparatus of FIG. 1 by vectors, and the configuration shown in FIG. The same parts as those of the members are designated by the same reference numerals.

In FIG. 1, 1 is a transmission signal input terminal to which a serial data signal to be transmitted is applied, and 2 is a dual system in which the data retention time of the serial data signal input to the transmission signal input terminal 1 is doubled. Serial-parallel converters 3, 4 for converting the four-phase phase-modulation symbol data signals into low-pass filters for band limiting the two-system 4-phase phase-modulation symbol data signals converted by the serial-parallel converter 2, respectively. Is a low-pass filter. 5 is a two-system 4 which is band-limited by the low-pass filters 3 and 4, respectively.
The phase-phase modulated baseband signals I (t) and Q (t) are subjected to the same calculation as that of the calculation circuit 5 of FIG. 3, and the in-phase component I ₁ and the quadrature component Q _{1 of} the first modulated signal and the second component, respectively. Operation circuit (I) for obtaining in-phase component I ₂ and quadrature component Q ₂ of the modulated signal of
The configuration and operation of the arithmetic circuit 5 in the conventional example shown in FIG. 3 are exactly the same.

Reference numeral 12 denotes an in-phase component I ₁ and a quadrature component Q _{1 of} the first modulation signal calculated by the arithmetic circuit 5, and an in-phase component of the second modulation signal.
A third modulation having a predetermined modulation phase difference selected by I ₂ and the quadrature component Q ₂ so as to reduce the loss when the modulated signals of the two systems are vector-combined by the power combiner 10 described later. An arithmetic circuit (II) for calculating the in-phase component I ₁₁ , the quadrature component Q ₁₁ , the in-phase component I ₂₁ , and the quadrature component Q ₂₁ of the fourth modulation signal and outputting the control signal C ₁ to the power supply voltage control circuit 15 (II ), 13 is the first modulation by the in-phase component I ₁ and the quadrature component Q _{1 of} the first modulation signal calculated by the calculation circuit 5 and the in-phase component I ₂ and the quadrature component Q ₂ of the second modulation signal. It is determined whether or not the difference between the modulation phase of the signal and the modulation phase of the second modulation signal is larger than a predetermined value, the control signal C ₂ is output to the changeover switch 14 according to the determination result, and the control signal C ₃ is supplied to the power supply voltage. This is a determination circuit for outputting to the control circuit 15.

The predetermined value of the determination circuit 13 is the third and fourth values of the arithmetic circuit 12.
Is the same as the predetermined modulation phase difference of the modulation signal of. Further, the changeover switch 14 selects and outputs the first and second modulation signals calculated by the calculation circuit 5 or the third and fourth modulation signals calculated by the calculation circuit 12 according to the control signal C _2. To do.

As will be described later, the power supply voltage control circuit 15 uses the control signal C ₁ from the arithmetic circuit 12, the control signal C ₃ from the determination circuit 13, and the transmission output control signal C ₄ from the base station (not shown) to control C The bias voltage Vcc for the class amplifiers 8 and 9 is controlled.

Reference numeral 6 is a quadrature modulation in which the in-phase component I ₁ and the quadrature component Q _{1 of} the first modulation signal selected by the changeover switch 14 or the in-phase component I ₁₁ and the quadrature component Q ₁₁ of the third modulation signal are used for four-phase phase modulation. The device 7 is the second selected by the changeover switch 14.
This is a quadrature modulator that performs four-phase phase modulation by the in-phase component I ₂ and the quadrature component Q ₂ of the modulation signal of, or the in-phase component I ₂₁ and the quadrature component Q ₂₁ of the fourth modulation signal.

The class C amplifiers 8 and 9 amplify the signals v ₁ and v ₂ which are quadrature phase modulated by the quadrature modulators 6 and 7, respectively, according to the bias voltage Vcc, and the power combiner 10 determines the class C amplifiers 8 and 9 respectively. The signals S ₁ and S ₂ amplified by
Sent as a radio wave via.

Next, the operation of the above embodiment will be described with reference to FIG. 1 and FIG.

As in the conventional example, if a signal indicated by a vector is transmitted from the antenna 11 as shown in FIG. 2 for the data signal applied to the transmission signal input terminal 1, the vector is the class C amplifier 8, It is obtained by synthesizing the vectors ₁ and ₂ having the same absolute values corresponding to the output signals S ₁ and S ₂ of 9.

Similarly, the vectors ₁ and ₂ correspond to the output signals v ₁ and v ₂ having a constant amplitude output from the quadrature modulators 6 and 7, respectively, and are the constant multiples of the vectors ₁ and ₂ having the same absolute value. Is the gain of the class C amplifiers 8 and 9.

Here, the vectors ₁ and ₂ are four-phase phase-modulated output signals I ₁ , Q ₁ , I ₂ , and Q ₂ of the arithmetic circuit 5, and the phase difference φ _d between the vectors ₁ and ₂ is a predetermined value φ. If it is larger than _th , the decision circuit 13 switches the changeover switch by the control signal C _2.
14 is switched to the arithmetic unit 12 side.

Therefore, the output signals of the quadrature modulators 6 and 7 are the vectors ₁₁ and ₂₁ having the phase difference equal to the predetermined value φ _th and the following equation | ₁ | = | ₂ | = | ₁₁ | = | ₂₁ | .

Here, the output signals I ₁₁ , Q ₁₁ , I ₂₁ , and Q ₂₁ of the arithmetic unit 12 are I ₁₁ = I ₁ cos φ _c −Q ₁ sin φ _c Q ₁₁ = Q ₁ cos φ _c + I ₁ sin φ _c I ₂₁ = I ₂ cos φ _c + Q ₂ sin φ _c I ₂₁ = Q ₂ cos φ _c −I ₂ sin φ _c Is.

The signal vector to be transmitted, as shown in FIG. 2, the vector ₁₁ multiplied by a constant vector _{11, 21,
It} is obtained by combining ₂₁ with the power combiner 10.

Therefore, the decision circuit 13 outputs the switching control signal C _3, and the gain of the class C amplifier is φ when φ _d (t) ≦ φ _th , whereas φ _d (t)> φ _th. Then, when the arithmetic circuit 12 outputs the control signal C ₁ to set the gain of the class C amplifier to G × cos (φ _d (t) / 2) / cos (φ _th / 2), the power supply voltage control circuit 15 Bias voltage Vcc is generated so that the vectors of the output signals of class C amplifiers 8 and 9 are ₁₁ and ₂₁ , respectively.

The power supply voltage control circuit 15 is also informed that the base station instructs the mobile station to increase or decrease the transmission output power of the mobile station according to the distance between the base station and the mobile station. A bias voltage Vcc is generated according to the control signal C ₄ to control the power of the transmission signal.

Therefore, according to the above embodiment, the class C amplifiers 8 and 9 are
The phase difference of the vector of the output signal of does not become larger than the predetermined value φ _{th, and} even if the phase difference becomes small, the bias voltage
Since Vcc makes the amplitude constant, the power loss of the power combiner is reduced, and therefore the overall power efficiency can be improved.

EFFECTS OF THE INVENTION As described above, the present invention includes, in addition to the first calculation means for calculating the in-phase component and quadrature component of the first modulation signal and the in-phase component and quadrature component of the second modulation signal, The in-phase component and the quadrature component of the second modulation signal and the in-phase component and the quadrature component of the third modulation signal having a predetermined modulation phase difference and the in-phase component of the fourth modulation signal and Second calculation means for calculating the quadrature component is provided, and whether the modulation phase difference between the in-phase component and the quadrature component of the first modulation signal and the in-phase component and the quadrature component of the second modulation signal is larger than the predetermined modulation phase difference. It is determined whether or not the first and second modulated signals of the first arithmetic means are selected if not larger, and the third and fourth modulated signals of the second arithmetic circuit are selected when larger. , And the signal amplitude amplified by the first and second class C amplifiers. Since the bias voltage is supplied to the first and second class C amplifiers so that the width becomes constant, the first and second
The phase difference between the signals input from the class C amplifier to the power amplifier does not become larger than a predetermined value and the amplitude is constant, so that the power loss of the power combiner is reduced and the overall power efficiency is improved. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a transmitting apparatus according to the present invention, FIG. 2 is an explanatory diagram showing vectors of main signals in the transmitting apparatus of FIG. 1, and FIG. FIG. 4 is a block diagram showing the device, and FIG. 4 is an explanatory diagram showing the main signals in the transmitting device of FIG. 2 as vectors. 2 ... Series-parallel converter, 3,4 ... Low-pass filter, 5,1
2 ... Arithmetic circuit, 6,7 ... Quadrature modulator, 8,9 ... Class C amplifier, 10 ... Power amplifier, 11 ... Antenna, 13 ... Judgment circuit, 14 ... Changeover switch, 15 ... Power supply voltage control circuit.

Claims (1)

[Claims] 1. A conversion means for converting serial data to be transmitted into two systems of four-phase phase modulation symbol data signals, and band-limiting the two systems of four-phase phase modulation symbol data signals converted by the conversion means. And a second low-pass filter for obtaining two systems of four-phase phase-modulation baseband signals, and two-system four-phase phase-modulation baseband signals obtained by the first and second low-pass filters for the four-phase The envelope signal and the modulation phase of the phase-modulated baseband signal are obtained, the in-phase component and the quadrature component of the first modulation signal having the first modulation phase determined by the envelope signal and the modulation phase, and the envelope signal and the modulation First computing means for computing an in-phase component and a quadrature component of a second modulation signal having a second modulation phase determined by the phase; and the first computation. The in-phase component and the quadrature component of the first modulation signal and the in-phase component and the quadrature component of the second modulation signal, which are calculated by the stage, make it possible to obtain the in-phase component and the quadrature component of the third modulation signal having a predetermined modulation phase difference and the fourth component. Second computing means for computing the in-phase component and the quadrature component of the modulated signal, and the in-phase component and the quadrature component of the first modulated signal computed by the first computing means, and the in-phase component of the second modulated signal, It is determined whether or not the modulation phase difference of the quadrature component is larger than the predetermined modulation phase difference, and if it is not larger, the first and second modulation signals of the first computing means are selected. Selecting means for selecting the third and fourth modulated signals of the second arithmetic circuit; first quadrature modulating means for quadrature modulating the first or third modulated signal selected by the selecting means; and the selecting means. Selected by Second quadrature modulating means for quadrature modulating the second or fourth modulated signal, and first and second class C amplifiers for amplifying the signals modulated by the first and second quadrature modulating means, respectively. And a means for supplying a bias voltage to the first and second class C amplifiers so that the amplitudes of the signals amplified by the first and second class C amplifiers are constant.