KR100253415B1 - Quadrature modulator - Google Patents

Abstract

PURPOSE: A quadrature modulator is provided which internally compensates for amplitude error and phase error with respect to in-phase components and quadrature components to remove interference caused by unnecessary frequency components for the final output signal. CONSTITUTION: A carrier generator(111) generates a carrier frequency, and a carrier phase shifter(112) shifts the carrier signal generated by the carrier generator by pi/2. A quadrature modulation multiplier(110) multiplies a signal of quadrature component amplified by a variable amplifier by the carrier signal shifted by the carrier phase shifter. An amplifier(107) amplifies the output signal of the quadrature modulation multiplier containing an error component twice, and an in-phase multiplier(103) multiplies the output of the amplifier by the carrier generated by the carrier generator. An in-phase low pass filter(102) low-pass-filters the output of the in-phase multiplier, and the first adder(101) adds the filtered signal to a signal of in-phase component. An in-phase modulation multiplier(109) multiplies the signal from the first adder by the carrier, and a phase shifter(108) shifts the output of the amplifier by pi/2. A quadrature multiplier(105) multiplies the signal shifted by the phase shifter by the carrier, and a quadrature low pass filter(104) low-pass-filters the output signal of the quadrature multiplier. A variable amplifier(106) amplifies a signal of quadrature component. The degree of amplification of the variable amplifier is controlled by the output signal of the quadrature low pass filter. The second adder(113) adds the in-phase component modulated by the in-phase modulation multiplier to the quadrature component modulated by the quadrature modulation multiplier.

Description

Quadrature modulator

The present invention relates to an orthogonal modulator, and more particularly, to an orthogonal modulator capable of internally compensating amplitude and phase errors for in-phase and quadrature components so as to eliminate interference by unnecessary frequency components for the final output signal.

FIG. 1 is a block diagram showing a conventional quadrature modulator. As shown therein, a channel separator 1 separating an in-phase component I and an orthogonal component Q in order to modulate the data signal α (t). Wow; An oscillator 14 generating a variable for compensating amplitude and phase to the signal cosα (t) of the in-phase component I separated from the channel separator 1; A multiplier (11) for multiplying the variable (k1) of the oscillator (14) to compensate for amplitude and phase; Two oscillators (16) (21) for generating a variable to compensate for amplitude and phase in the signal (sin alpha (t)) of the quadrature component (Q) separated by the channel separator (1); A multiplier (17) (19) for multiplying the variables (k2) (k3) of each oscillator (16) (21) to compensate for amplitude and phase; An adder (12) for adding the output of the quadrature component multiplier (17) and the output of the in-phase component multiplier (11) to output the difference between the two signals; An oscillator (15) for generating a variable (k4) to compensate for the frequency in the signal output from the adder (12); An adder (13) for adding the variable (k4) generated by the oscillator (15) to output the difference value; An oscillator 18 for generating a variable to compensate for the frequency of the signal output from the quadrature multiplier 19; An adder 20 for adding the variable k5 generated by the oscillator 18 and outputting the difference value; A carrier frequency generator (2) for generating a carrier frequency and shifting the phase by? / 2; A multiplier (3) which multiplies and modulates the output of the adder (13) by the carrier signal (cosωt); A multiplier 4 for multiplying the output of the adder 20 by the? / 2 phase shifted carrier signal sinωt; Referring to the operation and operation of the conventional modulator consisting of an adder (5) to add the output of the two multipliers (3) (4) as follows.

First, assuming that there is no error component, and omit the error compensation structure, the final output signal after the in-phase component and the orthogonal component pass through the adder 5 is expressed by Equation 1 below.

OUT = cosωtcosα (t) -sinωtsinα (t)

If the amplitude error (A) and phase error (V) components are present, the final output passing through each adder and multiplier is expressed by Equation 2 below.

OUT = {k1 cosα (t) -k2sin α (t) -k4} cosωt + {k3sinα (t) -k5} Asin (ωt + V) + Lcos (ωt + U)

Here, if the oscillators 14, 15, 16, 18, 21 are adjusted to determine appropriate values of the variables (k1 to k5), amplitude errors (A) and phase errors (V) present in the in-phase and quadrature signals are determined. , Signal interference due to frequency leakage (L · cos (ωt + U)) can be eliminated and the signal shown in Equation 1 can be output.

In order to actually determine the values of the variables (k1 to k5), the measurement is performed by measuring a frequency component other than the desired signal component using a measuring instrument such as a spectrum analyzer at the final output stage while the various signals are applied. The value of the designer adjusts the oscillators 14, 15, 16, 18 and 21 to determine the variables k1 to k5.

As described above, in the conventional apparatus, since an appropriate compensation value for an internally configured compensation structure is measured by an external measuring instrument, the oscillator is individually compensated and compensated for, thereby causing a lot of cost and time.

Accordingly, an object of the present invention is to provide an orthogonal modulator for automatically compensating after determining an error value internally without measuring an output from the outside.

1 is a block diagram showing a conventional quadrature modulator.

2 is a schematic block diagram of a quadrature modulator of the present invention;

*** Description of the symbols for the main parts of the drawings ***

101: first adder 102: in-phase low-pass filter unit

103: statue multiplier 104: orthogonal low pass filter

105: quadrature multiplier 106: variable amplifier

107: drain amplifier 108: phase shift unit

109: In-phase Modulation Multiplier 110: Orthogonal Modulation Multiplier

111: carrier generation unit 112: carrier phase shift unit

113: second adder

The configuration of the present invention for achieving the above object is a carrier generation unit for generating a carrier frequency; A carrier phase shift unit for shifting the carrier signal cosω _c t generated by the carrier generation unit by π / 2 phase shift; A quadrature modulator multiplier 110 for multiplying and outputting a quadrature signal amplified by a variable amplifier and a carrier signal sinω _c t shifted by the carrier phase shift unit; A multiplier amplifier for amplifying the output signal of the quadrature modulator multiplier 110 including the error component twice; An in-phase multiplier (103) multiplying the output of the drain amplifier by a carrier (cosω _c t) generated by the carrier generator; An in-phase low pass filter unit for low-pass filtering the output of the in-phase booster; A first adder for compensating and outputting the signal filtered by the in-phase low pass filter to the in-phase component (cosω _m t); An in-phase modulation multiplier (109) for multiplying and outputting the signal compensated by the first adder and a carrier (cosω _c t); A phase shifter for shifting the output of the multiple amplifier by? / 2 phase; An orthogonal multiplier (105) multiplying a signal shifted in the phase shift unit by a carrier wave (cosω _c t); An orthogonal low pass filter unit for low-pass filtering the output signal of the quadrature multiplier 105; And a variable amplifier which is amplification-controlled amplifying a signal of the quadrature-phase component (sinω _m t) by the quadrature low-pass filter section output signal; It is achieved by configuring a second adder which adds and outputs an in-phase component modulated by the in-phase modulator multiplier 109 and an orthogonal component modulated and output by the quadrature modulator multiplier 110, and according to the present invention. An example will be described in detail with reference to the accompanying drawings.

2 is a schematic block diagram of an orthogonal modulator of the present invention, and a carrier generation unit 111 for generating a carrier frequency as shown therein; A carrier phase shift unit 112 for shifting the carrier signal cosω _c t generated by the carrier generator 111 by π / 2 phase shift; A quadrature modulator multiplier 110 for multiplying and outputting a quadrature signal amplified by the variable amplifier 106 and a carrier signal sinω _c t shifted by the carrier phase shift unit 112; A multiplier amplifier 107 for amplifying the output signal of the quadrature modulator multiplier 110 including the error component twice; An in-phase multiplier (103) for multiplying the output of the multiple amplifier (107) by the carrier (cosω _c t) generated by the carrier generator (111); An in-phase low pass filter 102 for low-pass filtering the output of the in-phase booster; A first adder (101) for compensating and outputting the signal filtered by the in-phase low pass filter (102) to the in-phase component signal (cosω _m t); An in-phase modulation multiplier (109) for multiplying the signal compensated by the first adder (101) and a carrier (cosω _c t) and outputting the multiplier; A phase shift unit 108 for shifting the output of the multiple amplifier 107 by? / 2 phase; An orthogonal multiplier 105 for multiplying the signal shifted in the phase shift unit 108 by a carrier wave (cosω _c t); An orthogonal low pass filter 104 for low-pass filtering the output signal of the quadrature multiplier 105; And the variable amplifier 106 for amplifying a signal (sinω _m t) of the quadrature low-pass filter section 104 is the amplification degree controlled by the output signal of the quadrature-phase component; The present invention constituted by the second adder 113 which adds and outputs an in-phase component modulated by the in-phase modulator multiplier 109 and an orthogonal component modulated and output by the quadrature modulator multiplier 110. Describes the operation and action of.

First, assuming that there is no error component and omit the error compensation structure, the final output signal after the in-phase component and the quadrature component pass through the second adder 113 is represented by Equation 3 below.

OUT = cosω _m tcosω _c t + sinω _m tsinsin _C t

If the amplitude error (A) and phase error (V) components are present, the final output passing through each adder and multiplier is expressed by Equation 4 below.

OUT = cosω _m t cosω _c t + sinω _m t Asin (ω _c t + V)

= cosω _m t cosω _c t + sinω _m t Asin _c t cosV + sinω _m t Acos co t _c sinV

Here, in order to make an error-containing equation as shown in Equation 4 into a normal signal without error as shown in Equation 3, an error component included in Equation 4 (sinω _m t · A · cosω _c t · sinV ) And subtract the error component (A · cosV) included in the next orthogonal component to '1'.

In more detail, the above-described operation is amplified by a double amplifier 107 by a multiplier amplifier 107 after a signal including an error component passing through the quadrature modulator multiplier 110, and the amplified signal 103 is in-phase multiplier (103). When multiplied by the carrier signal generated by the carrier generator 111 is output as shown in the following equation (5).

m (t) = 2 {sinω _m t · A · sinω _c t · cosV + sinω _m t · A · cosω _c t · sinV} · cosω _c t

= A · cosV · sinω _m t · (sin2ω _c t · sin0) + A · sinV · sinω _m t · (cos2ω _c t · cos0)

Equation 5 is filtered through the low pass filter 102, and m (t) = A · sinV · sinω _m t, and this signal is the in-phase signal (cosω _m ) through the first adder 101. t) and the added signal (cosω _m t -A · sinV · sinω _m t) are transmitted to the in-phase modulation multiplier 109 and multiplied by the carrier signal cosω _c t to pass through the second adder 113. The error component of 4 (sinω _m t · A · cosω _c t · sinV) is eliminated.

Next, when the signal passing through the multiple amplifier 107 is π / 2 phase shifted by the phase shift unit 108, the signal is output as shown in Equation 6 below.

m2 (t) = 2 {sin (ω _m t + 90 °) · sin (ω _c t + 90 °) · cosV + sin (ω _m t + 90 °) · A · cos (ω _c t + 90 °) · sinV}

= 2 {A · cosω _m t · cosω _c t · cosV − A · cosω _m t · sinω _c t · sinV}

Equation 6 is multiplied by the carrier signal cosω _c t through the quadrature multiplier 105 and then filtered through the low pass filter 104 to obtain the signal A · cosV · cosω _m t. The variable amplifier 106 reduces the gain by the DC component A · cosV in the signal to compensate for the amount A · cosV in the sinω _m t · Asin sin _{c c} · cosV term of Equation 4 above. Result.

As described above, the quadrature modulator of the present invention can automatically compensate for an error value after determining an error value internally without measuring an output from the outside, thereby reducing cost and time.

Claims (1)

A carrier generator for generating a carrier frequency; A carrier phase shift unit for shifting the carrier signal cosω _c t generated by the carrier generation unit by π / 2 phase shift; A quadrature modulator multiplier 110 for multiplying and outputting a quadrature signal amplified by a variable amplifier and a carrier signal sinω _c t shifted by the carrier phase shift unit; A multiplier amplifier for amplifying the output signal of the quadrature modulator multiplier 110 including the error component twice; An in-phase multiplier (103) multiplying the output of the drain amplifier by a carrier (cosω _c t) generated by the carrier generator; An in-phase low pass filter unit for low-pass filtering the output of the in-phase booster; A first adder for compensating and outputting the signal filtered by the in-phase low pass filter to the in-phase component (cosω _m t); An in-phase modulation multiplier (109) for multiplying and outputting the signal compensated by the first adder and a carrier (cosω _c t); A phase shifter for shifting the output of the multiple amplifier by? / 2 phase; An orthogonal multiplier (105) multiplying a signal shifted in the phase shift unit by a carrier wave (cosω _c t); An orthogonal low pass filter unit for low-pass filtering the output signal of the quadrature multiplier 105; And a variable amplifier which is amplification-controlled amplifying a signal of the quadrature-phase component (sinω _m t) by the quadrature low-pass filter section output signal; Quadrature modulator comprising a second adder for adding the in-phase component modulated by the in-phase modulation multiplier (109) and the orthogonal component modulated and output by the quadrature modulator multiplier (110).