TW578406B - Method for measuring and compensating gain and phase imbalances in quadrature modulators - Google Patents

Abstract

A simple and efficient method to measure base-band gain and phase imbalance as well as orthogonality phase imbalance in a quadrature (IQ) modulator. The method comprises estimating values of modulator gain and phase imbalances while the modulator is operational, by inputting at least one test signal at a base-band frequency fi to the modulator to generate detected output signals having a term at frequency 2fi and computing the imbalances based on the 2fi term the computed imbalances then used in normal transmit operation to generate a pre-distortion transformation on the transmit signal to generate an imbalance compensation. The method can be easily expanded to cope with frequency dependent base-band amplitude and phase imbalance. This feature has an advantage when the transmitted signal is a multi-carrier signal, as the compensation can be adapted for each individual carrier.

Description

578406 Bureau of Intellectual Property, Ministry of Economic Affairs (printed by A ^ _Cooperative Cooperative A7 _____B7_ V. Description of the Invention (1) Field and Background of the Invention: The present invention relates to the measurement and calibration of quadrature modulators used in digital communication transmitters. AC modulators (sometimes referred to as IQ modulators) (especially those used in radio frequency integrated circuits (RFICs) operating at high frequencies in the GHz range) ) May cause significant gain and phase imbalances in the baseband path, or quadrature phase imbalances in the local oscillator path. Often referred to as gain and phase imbalance (or " IQ "imbalance) The effects of these degradations are the distortion of the transmitted signal, which translates into poor or even unacceptable performance. In many cases, designing and making a quadrature modulator with sufficiently low gain and phase imbalance often results. It is impractical and sometimes not feasible. However, if the gain and phase imbalance of the quadrature modulator can be estimated, there are known methods to compensate the transmitted Input signal, or equivalently distorting the transmitted input signal in advance, thereby cancelling the effects of this gain and phase imbalance. The gain and phase imbalance 値 is usually not fixed and can vary with operating conditions and components. Factors such as aging, etc. When installing or operating a quadrature modulator, a simple and efficient built-in method is needed in order to perform these measurements and evaluate compensation terms in a timely manner. Summary of the Invention: The method of the present invention A sequence of test signals is applied to the input of the quadrature modulator, and the resulting output is coupled to a detector and processed to evaluate the estimates of modulator gain and phase imbalance. The paper size applies the Chinese National Standard (CNS) A4 specification (210X297 mm) _ 4 _ (Please read the precautions on the back before filling out this page). Binding, order, line. 578406 A7 _B7________ 5. Description of the invention (2) ( (Please read the notes on the back before filling out this page) In transmission operations, these estimates are used to compensate or equivalent predistortion of the transmitted signal in order to offset The effect of gain and phase imbalance on the transmitted signal. The method proposed by the present invention uses a sequence of test input signals, which are combined with the operation of the detector circuit to perform a Simple and accurate evaluation. In a preferred embodiment, the test signals are sinusoidal waveforms with a specific amplitude and phase, so a specific signal is generated at the output of the quadrature modulator. When the AC modulator is compared, the gain and phase imbalance of the quadrature modulator will distort the signal. The distortion is equivalent to generating additional spectral components, and the frequency, amplitude, and phase of the additional spectral components are The modulator is unbalanced as a function of 値. A detector coupled to the output of the modulator performs a non-linear operation, thus generating several intermodulation products between various spectral components. As can be seen from the following, the amplitude of the 2fi (where is the frequency of the input sinusoidal waveform) component is proportional to the gain and phase imbalance terms of these modulators, and by controlling the amplitude and phase of the test signals, These terms can be derived from the frequency of this 2fi component. According to the present invention, a method for calibrating a quadrature modulator is provided by the Intellectual Property Cooperative Employees ’Cooperative Bureau of the Intellectual Property Bureau of the Ministry of Economic Affairs. Band I (t) and Q (t) signals. The modulator is used to transmit the signal after quadrature modulation. The method includes the following steps: (a) when the modulator is in operation, sequentially estimate The gain of the modulator is unbalanced, and the phase of the modulator is unbalanced. The estimation step includes inputting at least one test signal at a base band frequency fi to the modulator so as to first -This paper size applies Chinese National Standard (CNS) A4 specification (210X 297 mm) 578406 A7 B7 V. Invention Description (3) (Please read the precautions on the back before filling this page). In the phase imbalance estimation, a detected output signal having a term below the frequency 2f, is generated, and the gains and phase imbalances are calculated based on the 2fi terms of the detected output signals; and (b) at normal In the transmission operation, first aim at the gain The unbalance is then compensated for the phase imbalance in order to obtain a substantially quadrature modulated signal that is essentially ideal. The compensation step includes inputting a transmission signal to the detector and calculating the These gains and phases are not balanced, and a pre-distortion transform is applied to the input transmission signal. According to a feature of the method of the present invention, the calculation of the gain imbalance is based on an iterative operation, the iterative operation includes: modifying the test signals, and repeating the measurement of the detected output signal items at a frequency of 2fi Until it reaches a reference level of the detected output signal. The Intellectual Property Bureau of the Ministry of Economic Affairs (industrial and consumer cooperatives prints another feature of the method according to the present invention, the method further includes the following steps: for the gain imbalance, and in a first step, the A cosine waveform is input to the terminal, and a zero waveform is input to the Q input. In a second step, a zero waveform is input to the I input, and the same cosine waveform is input to the Q input. And for phase imbalance, in a first step, two sinusoidal waveforms are input to the I and Q inputs, the two sinusoidal waveforms have the same amplitude and frequency, but the two sinusoidal waveforms are as follows Equation 40 shown in Equation 17. + 0 ϊ phase shift, or two sine waveforms can be input in a second step, these two sine waveforms have the same amplitude and frequency, but between these two sine waveforms There is a phase shift of + 90 ° + 0 2 as shown in Equation 21. According to another feature in the method of the present invention, the phase is unbalanced -6-This paper size is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) 5784 06 A7 B7 V. Description of the invention (4) The calculation step includes the following steps: using the test signal input and an iterative operation to calculate a base band phase imbalance △ 0 and a local oscillator quadrature phase imbalance, respectively. △ 0, wherein the iterative operation includes modifying the test signals by changing the phases Θ ′ and β 2 and repeating the measurement of the detector output signals until the signal term at the frequency 2fi is effectively cancelled. According to the present invention In another feature of the method, the reference frame is a result of a first measurement of a detected output amplitude at a frequency 2fi generated by a first test signal. According to yet another feature of the method of the present invention, input at least one of The step of the test signal at a base band frequency fi includes the following steps: inputting a plurality of N test signals, and each test signal is at a different base band frequency fi (N); and applying a prior to the input transmission signal This step of the distortion transformation includes the following steps: applying a frequency-dependent predistortion transformation. Brief description of the drawings: The invention is illustrated herein by way of example only. These drawings are: Figure 1 is a high-order block diagram of a system including a quadrature modulator to which the method of the invention is applied; Figure 2 is a diagram of the method The general block diagram of the main steps; Figure 3 shows the signal flow through the quadrature modulator; Figure 4 is a flow chart for measuring the gain imbalance; This paper size applies the Chinese National Standard (CNS) A4 specification (210X 297 gong) (Please read the notes on the back before filling out this page) Binding · Order printed by the Employees 'Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 578406 Printed by the Employees' Cooperatives of the Intellectual Property Bureau of the Ministry of Economics A7 B7 ) FIG. 5 is a measurement flow chart of phase imbalance. DESCRIPTION OF SYMBOLS 12 Quadrature modulator 14 Test signal generator 16 Output signal 22 RF coupler 18 Detector 20 Detector output 24 Tracking bandpass filter 30 Filter output 3 2 Processor 34 Estimation 値 40 Input signal 42 Advance Distortion device 5 0 In-phase port 60 Quadrature 52,54 Block 70 First mixer 72 First local oscillator signal 74 Second mixer 76 Second local oscillator signal 80 Phaser device 82 Phase Error box (please read the notes on the back before filling this page) This paper size is applicable to Chinese National Standard (CNS) A4 specification (210X 297 mm) _ 8-578406 A7 ——____ B7_ V. Description of the invention (6) 90 Combined with network 78 common input signal (please read the precautions on the back before filling out this page) 210 Single-sideband carrier 212,220 Small-sideband component 222 Main sideband carrier Description of the preferred embodiment: Property Bureau 3 (industrial consumption Printed in Figure 1, a quadrature modulator (12) receives an input test signal (especially a sine waveform with a specific amplitude and phase) from a test signal generator (1 4). The output of the AC modulator generates a specific output signal (16). When compared with an ideal quadrature modulator, the amplitude and phase imbalance of the quadrature modulator distort the signal. The distortion is equivalent An additional spectral component is generated, and the frequency, amplitude, and phase of the additional spectral component are a function of the imbalance of the modulator. The sample of the output signal is passed through a radio frequency coupler (2 2 ) And a detector (1 8), which performs a non-linear operation to generate a number of intermodulation products between various spectral components of the output signal, including 2f The next component, where fi is the frequency of the input sinusoidal waveform. A detector output (20) is processed in a tracking band-pass filter (24), which is extracted by the tracking band-pass filter (24), while Reject unwanted components.-Filter output 30) preferably is then input to a digital processor, a processor (32), the processor (32) calculates an estimated value (34) Zhi of gain and phase imbalance. In an embodiment, the paper size of the filter and the wave book can be adapted to the Chinese National Standard (CMS) A4 specification (210X297 mm) -9-578406 A7 —— ____B7 V. Description of the invention (7) The device (24) is implemented as Part of the processor (32). (Please read the precautions on the back before filling this page) In normal transmission operation, an input signal (40) passes through a predistortion device (42), which performs a predistortion transformation on the signal, And the unbalance effect of the quadrature modulator is compensated. A predistortion device (42) is set using the calculated estimate 的 (34). The method of designing and setting a compensation device such as a device (42) is known in the art. Figure 2 is a general block diagram of the method of the present invention. This measurement and calibration phase includes the steps described below and is performed sequentially in order to evaluate the gain imbalance first and then to repeat these steps to evaluate the phase imbalance. Printed by the 8th Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs In a generation step (102), the signal generator (14.) in FIG. 1 provides a test input signal. Then, in a test signal transmission step (104), the test signals are transmitted through a quadrature modulator (1 2), so as to generate an output signal (1 6), the output signal (1 6) includes gain and phase distortion. Then in a detection step (106), the detector (1 8) detects the signal (16), and the detector output is also measured in the detection step (1 06). The processor (3 2) then uses the detector to measure chirp to perform a gain and phase imbalance calculation step (108). First, calculate an estimate of the gain imbalance in an iterative manner as shown by the arrow (11 2). The method is to modify the test input and repeat steps (102), (104), and (106) until the measured Output until a predetermined (reference) 値. Finally, a setting step (110) is performed in the processor (32) to set the pre-distortion device to compensate the gain imbalance effect. And execute a similar sequence of steps. This paper size applies the Chinese National Standard (CNS) A4 specification (210X297mm) ~ j〇T ~ 578406 A7 — __B7 V. Description of the invention (8) in order to compensate the phase imbalance effect. (Please read the precautions on the back before filling this page.) After the measurement and calibration phase, the transmitter is switched to the "normal" transmission operation mode. As shown in Figure 2, then perform the following steps: Predistortion The device (42) applies a pre-distortion transform (1 5 2) to a transmission signal (150). Then in a transmission step (15 4), the pre-distorted signal is transmitted via a quadrature modulator (1 2). The pre-distorted signal causes an existing gain and phase imbalance. However, due to the pre-distortion, the net effect is almost " ideal " the signal after quadrature modulation. Quadrature Modulator To make this method easier to understand, a brief description of the operation of the quadrature modulator and the effects of gain and phase imbalance are provided below. An ideal quadrature modulator performs the following mathematical operations on a pair of input signals I (t) and Q (t): Y⑴ = I (t) sin (coL〇t0 Q (t) cos (coLOt) (1) Where I (t) and Q (t) are the baseband input signals, and 2; γ ". Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs is the local oscillator (L0) radial frequency (rad / sec) The operation of a " actual " quadrature modulator with gain and phase imbalance is shown in Figure 3. The detector has two input ports, one of which is labeled I, or " in-phase " (50), and the other input port is marked as Q or " orthogonal " port (60). The corresponding baseband input signal causes gain and phase imbalance. Without losing the universality, we can change all The imbalance effect is expressed as occurring in the path of the I signal. A square (52) represents I and -11-This paper size applies the Chinese National Standard (CNS) A4 specification (21 Οχ 297 mm) 578406 A7 B7 V. Description of the invention (9) (Please read the notes on the back before filling in this page) The relative phase shift between Q paths is △ 0, and a square (54) is Table 1 shows the amplitude gain imbalance ratio 1 + ε between the Q path. The 値 ε and Δ Θ can be frequency dependent on the input signal frequency fi or a function of the input signal frequency fi. I signal (due to the gain and Distortion due to phase imbalance) is input to the baseband input of a first mixer (70), and a first local oscillator signal (72) at frequency h. Is input to the first mixer LO port. As is known in the art, a mixer such as the mixer (70) effectively performs multiplication between two input signals, thereby up-converting the input baseband signal. The Q signal is input To a second mixer (74), and a second local oscillator signal (76) also at the frequency is printed into the second mixer L◦ port by the employee consumer cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. Therefore, the Q input baseband signal is up-converted. The phase relationship between the two up-converted signals depends on the relative phase between the two local oscillator signals. A common input signal (7 8) is passed by one minute Phaser device (80), and the phase splitter The characteristic of the device (80) is that it has a 90 ° phase shift (that is, quadrature) between the two outputs, so the local oscillator signal (7 2) and ( 7 6). A phase error square (8 2) represents a phase error Δ 0 of the phase shift, or equivalently represents a quadrature phase imbalance △ 0 between the two local oscillator signals. Here, also Without loss of universality, we can assume that the quadrature phase error is in the I path. A combined network (90) adds the outputs of these two mixers into a quadrature modulator output (1 6). In the following, the following notation will be used: This includes gain and phase (baseband and quadrature) unbalanced quadrature -12- This paper size applies the Chinese National Standard (CNS) A4 specification (210X 297 mm) 578406 A7 B7 V. Description of the invention (10) The output of the modulator is: Y (t) = (] + ε) Γ (1; A0) sin (toL〇H Δφ) + Q (t) cos (© i〇t) (2 ) (Please read the notes on the back before filling this page) and I '(t, △ 0) represents the phase shift (△ 0) transformation of input I (t). When we deal with sine / cosine waveforms, for ⑴ = Acos (^ t + 0), we have I ’(t, △ 0) = Acos (0it + 0 + A0). Thus: l (t) = Acos ((〇jt + Θ) Q (t) = Bcos (c〇it) and Ύ⑴ = (] + ε) Acos (c〇it + Θ + ^ 0) 5 ^ 1 (( 01 ^ + Δφ) + Bcos (c〇it) cos (c〇L〇t) (3) Everyone knows that the modulated waveform can be expressed by the following formula: Y (t) = SLC〇s [((〇〇 L〇-i ^ i) t + Ψι) + Sucos [((〇LO + i〇i) t + ψυ) (4) Therefore, it can be seen that the quadrature modulator output of the I and Q sine waveform inputs includes two edges Band carrier, where one sideband carrier is lower than L0 frequency and is at fL0-f, and the other sideband carrier is higher than L0 frequency and is at +. This is printed by the 8th Industrial Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs. The amplitude and phase of the sideband are related to the input amplitude and phase, and the chirp of the modulator imbalance. As shown in the detailed method derivation below, we better choose the specific chirp of the I and Q input amplitude and phase in order to derive Give a simple dependency of one of these imbalances. At the same time, let's examine an interesting example: Example: i (t), Q (t) sine with the same amplitude and frequency band shifted 90 degrees from each other / Cosine waveform, for example: -13- This paper size is applicable National Standard (CNS) A4 specification (210X297 mm) 578406 Printed by the Industrial and Commercial Bureau of the Ministry of Economic Affairs, W. Consumer Cooperatives A7 __ B7_ V. Description of the invention (11)] (t) = Acos (c〇it-900) = Asin (ci) it) Q (t) = Acos (cojt) If you ignore the modulator imbalance, you can get: λ (t) = Asin (i〇it) sin (c〇u > t) + Α (: 〇5 (ω4) <: 〇5 (ωΐΌ〇- Acos [(c〇l〇_ (5) That is, the output is included in the frequency fu) -fi = (ω LQ-ω i) / 2 7Γ A single sideband carrier. Now, for the same sinusoidal input waveform, we calculate the effects of gain and phase imbalance: Y (t) = A (l + s) sin (c〇it + △ ehirKcoLot + Δφ) + Acos (〇it) cos (c〇L〇t) By the standard trigonometric function operation, we can get: Υ⑴ = SLcos [(coLCr ^ t + \ | 〇 + Sucos [((i) Lc) + c〇i; ) t + ψιΟ where: 5, = ^ (1 + 〇cos2 (A ^) ^ 2 M-^ (1 ^ / 2) Sd: Let — Α [ε / 2 ^ (Αφ + Αθ) / 2) and where Equivalent approximations are valid when the imbalance terms are sufficiently small. It can be seen from this expression that when the gain and phase are unbalanced, a tiny component at the artifact frequency ho + fi will be obtained, and the amplitude of the component is proportional to these unbalanced terms (also The main term under ho-fi, and the amplitude of the main term will only change slightly due to the gain imbalance). The size of this paper is applicable. National Standard (CNS) A4 (210X 297mm) -14- (6) (Please read the precautions on the back before filling this page) (7) (8) (9) 578406

Detector The output signal of the quadrature modulator ((16) in Fig. 1) is coupled to a detector ((18) in Fig. 1) via a multiplexer ((22) in Fig. 丨). . The detector performs a non-linear transformation on its input (signal (16)), which can be approximated by the following formula (square-law detector): V〇ut = Kl Vin2 where Vin is the input, Voiu is the output, and Kl Is the scale factor. As we all know, when Vin contains more than one carrier, the output will include several intermodulation terms. Appropriate filtering (filter (24) in Figure 1) can be selected-the desired item. For I and Q sine inputs, we get: (10) (Please read the notes on the back before filling this page) vin = K2Y (t) = K2lSLc〇s [(ci > Lcr-CD〇t + + δυε〇3 [ (ωιο + ω〇ι The 8th Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economy printed the filter to extract the 2fi terms, and at the same time rejected the unwanted terms. That is, when the modulator output has f ^ -fi and fuD + fi component, the detected output has 2 fi components due to a non-linear effect. Then, the only relevant term (after filtering) Z is a frequency equal to the frequency difference between the two subcarriers (or equivalent One of the difference frequency components between the two subcarriers in the baseband input frequency), and Z has an amplitude SD proportional to the amplitude products of the subcarriers, that is: Z = SDccs (20jt π- ψ) = k SuSLcos (20it + ψ) (11) where k is a scale factor and γ is a (irrelevant) phase term. In the above equation, 値 (Equations 8 and 9) of the above example is used to replace the paper Standards are applicable to China National Standard (CNS) A4 specifications (210X 297 mm) _ 15-578406 A7 — one ___B 7 V. In the description of the invention (13), SD is proportional to the imbalance term, that is: SD-= kA2 (l + ε / 2) [ε / 2 + (ΔΘ + Δφ) / 2] — κ [ε / 2 + (ΔΘ + Δφ ^) / 2] (12) (Please read the precautions on the back before filling out this page), and the approximations are valid when the imbalance term is small enough. A "actual" test The nonlinear transformation function of the detector may deviate from the simple function (square law) described above. In the detailed derivation of the measurement of gain and phase imbalance, it will be seen that the method proposed by the present invention has the knowledge of the accurate description of the detector transformation function Method embodiments The method of the present invention includes two main phases: Phase I: Evaluate the gain imbalance term ε and apply the resulting compensation. Phase II: Evaluate the phase imbalance terms Δ 0 and Δ 0, and The compensation obtained is applied. The Intellectual Property Bureau of the Ministry of Economic Affairs, g (industrial and consumer cooperatives, printing phase I-gain imbalance: Figure 4 shows the signal flow of the gain imbalance measurement. To evaluate the gain imbalance between the I and Q baseband paths , In step 1 (will be shown in detail below) on the I input port (Hereinafter referred to as " I input terminal "50) and transmits a test signal on a Q input port (hereinafter referred to as " Q input terminal") (50), The generated (first) signal amplitude is measured at the output of the filtered detector (18) (the first amplitude will be used as a reference in the next step). Repeat the experiment with these inputs interchanged ("Step-16- This paper size applies to the Chinese National Standard (CNS) A4 specification (210X297 mm) 578406 A7 ____ B7 V. Description of the invention (14) 2", please refer to Below), that is, a test signal is transmitted on the Q input (60), a zero signal is transmitted on the I input (50), and the (second) signal amplitude generated is measured at the detector output . Change the amplitude of the test signal at the Q input (up and down in small increments) until the amplitude of the signal generated at the output of the detector is equal to the reference 値 in step 1. This method can measure gain imbalance regardless of the amount of phase imbalance. Phase I-Detailed procedure Step 1: The following signals are transmitted: (13) η]] (t) = Acos ((〇it)

QiO) = 〇 Then Y I (t) = A () + €) cos ((〇it + Ae) sin (coL〇t + Δφ)

The signal spectrum of Yi (t) includes two subcarriers under fL0-fi (1 10) and fLo + fi (112). The two subcarriers have almost the same amplitude (when the gain is balanced, the amplitude is the same) . The filtered detector output (that is, the term under frequency 2fi) is equal to: (14) I ----- r--install-- (Please read the precautions on the back before filling this page)

Zj (t) = kA2 (K e) 2cos (20it + \ i / i) where k is a scale factor and P is an uncorrelated phase term. The subscript " Γ means the parameter of step 1. Steps This paper size applies the Chinese National Standard (CNS) A4 specification (210X 297 mm) _ 578406 A7 ___B7_ V. Description of the invention (15) Repeat the experiment and exchange the I and Q test signals transmitted at the same time: 12 ( 0 = 0 (15) Q2 (t) = A () + A) COS (C〇it) (Please read the notes on the back before filling this page} where △ is a control variable of Q input amplitude. Then: Y2 (t) = A () + 2) COS (C〇it) C〇S (0) L〇t) It is easy to know that the filtered detector output (that is, the term at frequency 2fi) is equal to: z2 ( t) = kA2 (1 + Δ) 2〇〇5 (2ωίΗψ2) (16) where k is a scale factor and is an unrelated phase term. The subscript "2" means the parameter of step 2. Under the assumption of the square-law detector and △ = 0, it is easy to print the ratio between the amplitudes from the employees' cooperatives of the Intellectual Property Office of the Ministry of Economic Affairs of Z1 and Z 2 (Equations 14 and 16), and derive the gain imbalance into amp. (Z〇 / amp (Z2) == (1 + ε) 2. We do not calculate the ratio, but use the measured amplitude of Z1 (step 1) as a reference 値, and repeatedly modify the input in step 2 Amplitude (via Control the variable △ and modify it in small increments up and down) until the resulting Z2 amplitude is equal to the reference 値. Assuming Δ is △ 时 when the equality occurs, then: ε = △ etc. via the iterative procedure When reducing these amplitudes, the gain imbalance term can be solved without assuming the exact form of a "actual" detector's non-linear transform function. After the gain imbalance term is measured and evaluated, The signals transmitted on the I and Q ports are appropriately scaled so as to compensate for the application of the paper size. National Standards (CNS) A4 specifications (2 丨 〇, 乂 297 mm) 8 ~ * 578406 A7 B7 V. Description of the invention (16) The effect of unbalance. (Please read the notes on the back before filling out this page.) Phase II-Phase Imbalance: Figure 5 shows the signal flow of the phase imbalance measurement. To evaluate the path between the I and Q baseband paths Phase imbalance and quadrature phase imbalance in the LO path, in step 1, we transmit a sine test signal on the I input (50) and a cosine (also on the Q input (60)) That is, there is -90 ° phase relationship) signal, and the resulting (first) signal amplitude is measured at the output of the filtered detector (18). The input signal is set to: in the ideal case (that is, without phase imbalance) ), We should get a single sideband carrier (2 1 0). Due to the phase imbalance, we also get a small sideband component (2 1 2) at the artifact frequency. After the detector (18), we get a component at frequency 2fi. The amplitude of this component is proportional to the phase imbalance. In step 2, the procedure is repeated with new test inputs 値 (50) and (60). The new test inputs 値 (50) and (60) are selected so that the phase relationship between inputs I and Q (Under nominal) is + 90 °. In this case printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, we obtain a main sideband carrier (222) and a small sideband component (220) at the artifact frequency. However, these frequency positions This is the reverse of the frequency position obtained in step 1. We measure the resulting (second) signal amplitude at the detector output. Based on these two measurements, we can solve the phase imbalance △ β in the baseband and the phase imbalance △ ^ in the quadrature (local oscillator). However, this approach will require a priori calibration of the detector (a-priori calibration) and knowledge of the detector's transform function. In the detailed description below, we would rather choose a variant of the above procedure to apply the Chinese paper standard (CNS) A4 specification (210X297 mm) ~ 'Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs (18) (19) 578406 Α7 Β7 V. Description of the invention (17) (applicable to " actual " detector), instead of measuring the 2 fi signal amplitude at the detector output (requires calibrated measurement), so we are relative to the I input Move the Q input by a (known) control phase θ until the 2fi term is canceled. The θ 抵消 that is used to cancel out is used to solve Δ 0 and Δ 0. We assume that the measurement of gain imbalance has been performed The signals transmitted on the I and Q ports are appropriately scaled. However, it is also possible to perform a phase imbalance measurement when there is still a small residual gain imbalance. Phase I-Detailed Procedure Step 1: Transmission of two The same amplitude and frequency but 90 ° between each other. · Θ 'phase shifted sine waveform, where Θ! Is a control (tuned) phase variable 1 丨 (〇 = Acos (c〇it -900+ Θ 丨) = Asin (c〇it + θ ) (17)

Qi (t) = Acos (tojt) Assuming gain balance (equivalently, the gain imbalance has been compensated in advance), we get: Y 丨 (t) = Asin (c〇it + Θ! + + Δφ) + Acos (c〇it) cos (coLOt) By the standard trigonometric function operation, we can get:

Yl (t) = SL] C〇s [(wL ^ i) t + \ | / Li) + Suicos [(toL〇 + 0i) H ψυι) Where: This paper size applies the Chinese National Standard (CNS) A4 specification (210X297 Mm) -20- --------- L -------- " equipment ------ order ------ V--It (please read the first Note for this page, please fill in this page) 578406 Α7 Β7 V. Description of the invention (18)

Sli = ~ A

Sui = Ajsin [(θι + ΔΘ + Δφ) / 2] | Α | (θ] + Δθ + Δφ) / 2 | and the filtered detector output (that is, the term at frequency 2fi) is equal to: Z, j (t) = kA2 | sin [(θι + ΔΘ + Δφ) / 2] | ο〇5 (2ωίΗψ)) (20) where k 疋 is a scale factor and V1 is an uncorrelated phase term. Suppose that watts are straight lines that cancel the difference frequency component Z !. Θλ--(Δθ + Αφ) I --- II Pack-(Please read the precautions on the back before filling this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs with small steps to change 0 1 (in Range), and evaluate Λ until the difference frequency component Z! Note that in this step, we found that the combined base band Δ Θ and the local oscillator Δ 0 are out of phase. For some quadrature modulators, Δ 0 is negligible. In this case, Δ 0 = ~ (-1) Λ. However, when this assumption is not valid, an additional step is required to solve Δ Θ and Δ 0 individually, and the situation will be explained in step 2 below. When the measurement is in a noisy environment, or there is a residual gain imbalance, Λ is the minimum to minimize Z !. Step 2: We repeat the experiment, but use the following inputs: 2 (t) = Acos (c〇jt + 90〇 + ⑸ = _Asin (c〇it +02) Q: (t) = Acos (c〇it) (21) The paper size of the edition applies to the Chinese National Standard (CNS) A4 specification (2) 0X 297 Gongchu -21-578406 A7 B7 V. Description of the invention 0 9) where .Θ 2 is a control (tuned) phase variable

Y2 (() = -Asin (0; t-+-02+ A6) sin (c〇L〇 ^ + ^ φ) + Acos (〇jt) cos (0L〇O (22) is calculated by standard trigonometric functions. , We get: Y2 (t) = SL2C〇S [(C〇LCT (〇i) t + \ | / L2) + Su2C〇S [(C〇L〇 + C〇i) t + ψυ2) (23)

Where: SL2 = A | sin [(θ2 + ΔΘ-Δφ) / 2] | == Α | (θ2 + Δθ-Δφ) / 2 | Suf Acos [(02 + A0 + Aip) / 2] = ~ A 1 · —u— I jl-! I I l · »! · Ϋ —1 II (Please read the notes on the back before filling this page) (24) V / u and V / w are unrelated phase terms. As we expected, the signal has its larger component at the frequency hcH-fi, and in step 1, we get the larger component at fu-fi. Similar to step 1, the filtered detector output (that is, the term at frequency 2fi) is equal to: Z2⑴ = kA2 | sin [(02 + A0-A (p) / 2] | cos (2〇) it + ψ2) Where k is a scale factor and is an uncorrelated phase term. Suppose that 孓 is the 0 2 of the offset frequency component Z2. = -Δ0 + △ After solving these two equations, you can get: =-(5, +0,) / 2 △ 史 = Θ 丨 + 6 * 2) / 2 Cancel the difference frequency component Z through this iterative procedure ! And z2, there is no need to know the exact form of the non-linear transformation function of the detector. Any fake paper size applies the Chinese National Standard (CNS) Λ4 specification (210X 297 mm) _ 22-,-= t & gt Printed by 8th Industrial Cooperative Cooperative of the Ministry of Economic Affairs and Intellectual Property Co., Ltd. 578406 A7 __ _ B7 V. Description of Invention (20) (Please read the precautions on the back before filling this page) Under the circumstance, solve these phase imbalance items . The obtained phase imbalance terms are used to generate a transformation to the input signals, thereby compensating the baseband and quadrature phase imbalance of the quadrature modulator. The compensation equivalent to the pre-distortion method is conventional and will not be repeated in this article. Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. In summary, the method proposed by the present invention is used in its preferred embodiment for a test input signal with controlled amplitude and phase. As we all know, the gain and phase imbalance are reflected in the output spectral components, so a complex narrow-band receiver is needed to extract this information. However, the method proposed by the present invention uses a sequence of test signals at a base band frequency fi in an innovative way and a way different from the prior art technology, and uses a detector to analyze the frequency The amplitude of the detector output at 2 fi. The output term is proportional to the gain and phase imbalance, and by controlling these test signals, the estimates of the gain and phase imbalance can be calculated. These test inputs are selected so that the magnitude of this term at a frequency of 2fi is sufficient to avoid noise from the measurement and detector, and thus produce accurate results. In addition, such gain and phase imbalance measurements can be performed at several 値 N of the input frequency f i, thus showing the frequency dependence of these measurements. For a single carrier modulation, we usually use an average (or intermediate frequency) 增益 of gain and phase imbalance to perform compensation. However, for such as Orthogonal Frequency Division Multiplexing (FDM for short) For multi-carrier modulation such as), frequency-dependent compensation based on the 2fi component (N) can be applied individually for each carrier. To take account of the clarity of the description, the measurement and compensation sequence at each frequency is performed in the manner previously described. -23- The size of this paper applies to China National Standard (CNS) A4 (21 〇χ 297 公 楚) 578406 A7 _ B7 V. Description of Invention (21) All publications, patents, and patent applications mentioned in this specification The case is to use the full text as the reference material of this specification, and the degree of reference is like clearly and individually indicating that each individual publication, patent, and patent application is the reference material cited in the present invention. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is prior art to the present invention. Although the invention has been described with reference to a limited number of embodiments, it should be understood that many variations, modifications, and other applications of the invention can be made. (Please read the notes on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Office of the Ministry of Economic Affairs This paper applies the Chinese National Standard (CNS) A4 specification (210X297 mm) _ 24-

Claims (1)

578406 A8 B8 C8 D8 々, patent application scope 1 1. A method for calibrating a quadrature modulator, the quadrature modulator has an I input terminal and a Q input terminal for inputting the base band I (t ) And Q (t) signals, the modulator is used to transmit the signal after quadrature modulation. The method includes the following steps: a. When the modulator is in operation, sequentially estimate the gain of the modulator. A balanced chirp and a modulator with unbalanced chirp, the estimation step includes the following steps: i. Inputting at least one test signal at a baseband frequency fi to the modulator so as to first unbalance the gain In the estimation, then in the phase imbalance estimation, a detected output signal having a term at a frequency of 2fi is generated; and ii. Calculating the gain and phase imbalance based on the 2fi term of the detected output signals; And b. In normal transmission operation, compensation is firstly performed for gain imbalance and then phase imbalance, so as to obtain a substantially orthogonally modulated signal that is essentially ideal. The compensation step includes the following steps: : Iii. Inputting a transmission signal to the detector; and iv · applying a pre-distortion transform to the input transmission signal based on the calculated gain and phase imbalances 値. 2. The method of claim 1 in the patent application range, wherein the input step includes the following steps: a. For the gain imbalance, and in a first step, as shown in Equation 13, enter a Cosine waveform, and input a zero waveform on the Q input, and in a second step, such as Equation 15 This paper i scale applies the Chinese National Standard (CNS) A4 · (21GX297 mm) 7 ^ 1 " " " (Please read the notes on the back before filling out this page) Binding and printing Printed by the Intellectual Property Bureau Employee Consumer Cooperatives of the Ministry of Economic Affairs 578406 A8 B8 C8 D8 Printed by the Intellectual Property Bureau Employee Consumer Cooperatives of the Ministry of Economic Affairs , Input a zero waveform on the I input and a cosine waveform on the Q input; and b. For the phase imbalance, in a * table one * step, as shown in Equation 17, in Two sine waveforms are input to the I and Q inputs. The two sine waveforms have the same amplitude and frequency, but the two sine waveforms have a phase shift of -90 ° +, and may be In the second step, like the equation Shown in FIG. 21, two sine wave input, two sinusoidal waveforms have the same amplitude and frequency, but with a phase + 90 ° + Θ 2 of the shift between the two sinusoidal waveforms. 3. The method of item 1 in the patent application range, wherein the calculation step of the gain imbalance is based on an iterative operation, the iterative operation includes the following steps: modifying the test signals; and repeating the test at the frequency of 2fi The measurement of the output signal item is detected until a reference frame of the output signal is reached. 4. The method of item 1 in the patent application range, wherein the calculation step of the phase imbalance includes the following steps: using the input step and an iterative operation to calculate a base band phase imbalance △ Θ and a local oscillation, respectively The quadrature phase imbalance of the detector Δ ^, where the iterative operation includes modifying the test signals and repeating the measurement of the detector output signals until the signal term of the detection at the frequency 2fi is effectively cancelled. 5. The method of claim 3, wherein the reference chirp is the result of a first measurement of the detected output amplitude at a frequency 2fi generated by a first test signal. 6 · If you want to apply for the method of item 1 of the patent scope, enter at least one ------ U--install-(please read the precautions on the back before filling this page), 1T This paper size applies to China Standard (CNS) A4 specification (210X297 mm)-26-578406 A8 B8 C8 D8 々, patent application scope 3 This step of the test signal at a base band frequency fi includes the following steps: input a plurality of N test signals, and Each test signal is at a different baseband frequency (fKN); and the step of applying a pre-distortion transform to the input transmission signal includes the following steps: applying a frequency-dependent pre-distortion transform. (Please read the precautions on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs This paper applies the Chinese National Standard (CNS) A4 specification (210X297 mm) -27-