TW200838125A - Amplifying circuit and wireless communication device - Google Patents

Abstract

This invention demands for a power modulation characteristic with highest efficiency and lowest deviation. This invention is provided with an amplifier 22, a power modulator 31 for determining a power modulation voltage v(n) provided to the amplifier 22 based on a amplifier input signal u(n), a distortion compensator 30 for performing a distortion compensation based on an amplifier module 32a, a controller 32 for controlling the power modulator 31 and the distortion compensator 30. The controller 32 is configured for identifying the amplifier module 32a based on an output signal z(n) and an input signal U(n) of the amplifier 22 and the power modulation voltage v(n) provided to the amplifier 22, and for controlling a parameter for determining the power modulation voltage v(n) based on the amplifier module 32a.

Description

200838125 IX. Description of the Invention: [Technical Field] The present invention relates to an amplifying circuit and a wireless communication device, and more particularly to an amplifying circuit and the like which can compensate for distortion. [Prior Art] The amplifier requires a high degree of linearity. For example, a power amplifier that amplifies a linear modulation signal or a low noise amplifier that is used for a receiver of a linear modulation signal requires high linearity in order to suppress spectral characteristics and deterioration of transmission characteristics due to signal distortion. However, in order to improve the linearity of the amplifier, it is necessary to increase its saturation region. That is, in terms of the input/output power characteristics of the amplifier, the relationship between the input signal and the output signal is not linear in the range in which the output signal voltage is close to the amplifier power supply voltage, but becomes a non-linear region in which the input-output ratio is saturated. Therefore, in order to ensure linearity, it is necessary to apply a sufficiently large current and voltage (= electric power) to the amplifier as the power supply voltage, and the amplifier operates in an operation region having a lower power supply voltage and higher linearity. As a result, it is possible to ensure that the linear action region is narrowed, and the ratio of the output power of the amplifier to the used power (power source) (power efficiency) is deteriorated. Thus, the guarantee of linearity has a trade-off relationship with the securing of power efficiency. In order to seek to ensure linearity and to improve the power efficiency of an amplifier, a distortion compensation method for compensating for distortion generated in a non-linear region has been proposed. In the distortion compensation method, there is an input signal to the amplifier, which is obtained by adding a characteristic opposite to the distortion characteristic of the amplifier to the amplifier input by the 200838125 in advance, and obtaining a distortion-free desired signal in the amplifier output (pre-bridge positive method; Pre -distortion). An example of a pre-distorter for distortion compensation by pre-bridge positive method is: first, the correction amount is memorized in the LUT (look up table), and the difference between the amplifier output signal and the target output signal is used to sequentially correct it. The method of correcting the amount (called LUT mode); and the method of calculating the polynomial by using the amplifier output signal and the input signal by the polynomial approximate distortion correction amount ' 'number 値 (adaptive control) way (called polynomial approximation) Wait. In addition, in order to improve the efficiency of the amplifier, there is a method in which the input voltage of the amplifier is used to modulate the power supply voltage of the amplifier, and the power consumption of the amplifier is varied in accordance with the magnitude of the input signal (referred to as a power supply modulation method or It is the envelope tracking method). To maintain a constant supply voltage to the amplifier, a supply voltage that is sized according to the amplifier's maximum output voltage is required. As a result, even if the output voltage is small, the power consumption of the amplifier is large, and the power efficiency is deteriorated. C. In contrast, the power supply modulation method changes the power consumption of the amplifier in accordance with the size of the input signal. Therefore, when the output voltage is small, the power consumption of the amplifier can be suppressed, and the power efficiency can be improved. Further, Non-Patent Documents 1 and 2 propose a method of performing power supply modulation and performing distortion compensation by a predistorter. The advantage of performing power supply modulation and performing distortion compensation by pre-correction is that the efficiency of the amplifier can be increased and distortion can be reduced. Fig. 4 is a block diagram showing an amplifying circuit in which power supply modulation is performed and distortion compensation is performed by a predistorter. 200838125 The amplification circuit of FIG. 4 includes a power supply modulation unit ι〇1 that controls the power supply voltage of the power amplifier (pA; Power Amplifier) 100. The power supply modulation unit 101 is configured to match the amplitude of the input signal envelope of the amplifier 丨00 to change the voltage applied to the amplifier 〇〇. Further, the amplifying circuit includes a pA inverse model identifying unit 102 that recognizes the inverse model of the amplifier 100 based on the output signal of the amplifier 1 and the input signal '. The pre-bridge positive controller 103 performs distortion compensation of the amplifier 1 依据 according to the determined pa inverse model. ί [Non-Patent Document l] Donald F. Kimball, et. al.,

High-Efficiency Envelope-Tracking W-CDMA Base-Station Amplifier Using GaN HFETs", IEEE Transactions on Microwave Theory and Techniques, V o 1. 54, No. 11,

November 2006 .

[Non-Patent Document 2] Feipeng Wang, et al., "Design of Wide-Band Envelope-Tracking Power Amplifiers for OFDM Applications", IEEE Transactions on Microwave Theory C and Techniques, Vol. 5 3 , No. 4, April 2005 [Disclosure] The problem of the invention is to solve the problem. The signal proportional to the input signal of the amplifier is supplied to the power supply modulation unit 101. Therefore, the power supply modulation unit 110 changes the power supply voltage of the amplifier 10 based only on the envelope amplitude of the output signal of the predistorter. As a result, the amplifying circuit of Figure 4 does not maximize the efficiency of the amplifier, but rather the efficiency of the slack without considering the change in the supply voltage. In other words, the efficiency characteristic of the amplifier varies by the supply voltage (thin voltage) of the amplifier. Therefore, depending on the envelope amplitude of the output signal of the predistorter (the input signal to the amplifier), the power supply voltage of the amplifier 100 is changed, even if a certain degree of efficiency can be achieved, because the change of the power supply voltage is not considered. Since the characteristics of the amplifier 100 are changed, the efficiency of the slack is improved. As described above, the amplifier circuit of Fig. 4 cannot adjust the power supply modulation characteristics of the power supply modulation section, and it is not possible to optimize the amplifier efficiency and the free adjustment of the amplifier efficiency. Accordingly, it is an object of the present invention to provide an amplifying circuit and a wireless communication device that can adjust power supply modulation characteristics. Further, another object of the present invention is to perform control of both power supply modulation characteristics and distortion compensation characteristics. The present invention is an amplifier circuit comprising: an amplifier; a compensation unit that performs distortion compensation of the amplifier according to an amplifier model that displays characteristics of the amplifier; and a control unit that controls the power supply modulation unit and the distortion compensation unit; and the control unit controls an output signal according to the amplifier And the input signal, and the power supply modulation voltage applied to the amplifier, to determine the configuration of the amplifier model, and to control the parameter for determining the power supply modulation voltage according to the amplifier 200838125 model. In the above invention, the amplifier model is determined by the amplifier's power supply modulation voltage in addition to the amplifier's input and output signals, so the amplifier model can reflect the characteristic variation caused by the power supply modulation voltage. Then, the control unit controls the parameter for determining the power supply modulation voltage based on the amplifier model in consideration of the power supply modulation voltage, so that high-precision efficiency of the power supply modulation voltage can be considered. (% control unit should minimize the difference between the input signal of the aforementioned amplifier and the estimated input signal of the amplifier obtained by the aforementioned amplifier model, and maximize the power efficiency of the amplifier, and determine the power supply modulation voltage for determining the aforementioned power supply. The parameter is constructed in such a way that the distortion of the amplifier output can be minimized and the efficiency is maximized. The control unit should minimize the aforementioned difference and maximize the aforementioned efficiency by the gradient method. The gradient method can be easily used. The distortion and the efficiency are optimized. The control unit preferably uses the amplifier model expressed in power series and the power modulation expressed in power series when determining the parameter for determining the power supply modulation voltage. The function of the voltage on the input signal of the aforementioned amplifier. The operation of the amplifier model and the power supply modulation voltage to the input signal of the amplifier is represented by a power series. The present invention is a second aspect. An amplifier circuit comprising: an amplifier; a power supply modulation unit that determines the assignment based on an input signal of the amplifier a power supply modulation voltage of the amplifier; and a control unit that controls the power supply modulation unit to determine a parameter of the power supply modulation voltage. Further, in addition to 200838125, the control unit is configured to provide the variable voltage according to the amplifier. The above-described parameter configuration for determining the power supply modulation voltage is controlled. When the present invention is used, the control unit can control the parameter for determining the power supply modulation voltage to adjust the power supply modulation voltage, and thus the amplifier efficiency. The present invention is an amplifier circuit, an amplifier, and a power supply modulation unit that determines a power supply modulation voltage given to the amplifier according to an input of the amplifier; the distortion compensation unit is based on an amplifier model that displays characteristics of the amplifier. The distortion compensation of the front device is performed, and the control unit can control the parameters of the release type and the parameters for determining the power supply modulation voltage of the amplifier from the input signal of the amplifier. By the control unit, the parameters of the model can be controlled together, and used for the aforementioned amplifier The input signal determines the parameter of the power supply modulation voltage of the amplifier. Therefore, the efficiency distortion characteristic can be adjusted. The present invention, viewed from a fourth point of view, is a wireless communication device having a front circuit for amplifying a transmission signal or amplifying a reception signal. [Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a communication system having a wireless base as a wireless communication device and terminal devices 1 b, lc, 1 c as the same wireless communication device. The above-mentioned adjustable can be: a signal, > which is a wireless amplifier - 1 lb, 1 which is a wireless amplifier - 10, 200838125, which is used to amplify the first characteristic and the amplifier. Each of c and 1 d includes a receiver 1 for receiving a wireless signal, a transmitter 1 for transmitting a wireless signal, and a processing unit 13 for processing a transmission and reception signal. The receiver 11 receives a linear modulated signal having a low noise amplifying circuit 1 1 a for receiving a linear modulated signal for amplification. Further, the conveyor 12 is a power amplifying circuit 12a which transmits a linear modulation signal and which amplifies a linear modulation signal. The basic configuration of the low noise amplifying circuit 11a and the power amplifying circuit 12a is the same. Therefore, the power amplifying circuit 12a will be described below as an example. Fig. 2 shows the hardware configuration of the power amplifying circuit 12a. The power amplifier circuit 12a includes a digital signal processing unit (DSP) 21, an RF power amplifier (hereinafter abbreviated as amplifier) 22, and an envelope amplifier 23°. The amplifier 22 is used to amplify a linear modulation signal. However, an operation region having a non-linear characteristic is provided, and the distortion compensating unit 30 of Fig. 3 to be described later is required. In addition, in the amplifier 22, the power efficiency and distortion characteristics vary depending on changes in the input signal and variations in amplifier characteristics. The digital signal processing unit 2 1 can output a signal (baseband signal) input to the amplifier 22, and obtain an output (baseband signal) of the amplifier 22. Further, between the digital signal processing unit 21 and the input terminal of the amplifier 22, a DA converter (DAC) 24, a low pass filter (LPF) 25, an up converter 26, a band pass filter 27, and a driver are provided. 28. Further, between the output terminal of the amplifier 22 and the digital signal processing unit 21, a down converter 29a, a low pass filter 29b, and an AD converter -11-200838125 (ADC) 29c are provided. Further, the digital signal processing unit 21 outputs a signal (digital signal) indicating the power supply voltage to the amplifier 22 to the envelope amplifier 23. Further, between the digital signal processing unit 21 and the input terminal of the envelope amplifier 23, a DA converter (DAC) 24 and a low-pass filter 29d are provided. Fig. 3 is a block diagram showing the function of the amplifier 22 in the function of the digital signal processing unit 21. As shown in the figure, the digital signal processing unit 21 includes a predistorter (distortion compensation unit) 30 that performs distortion compensation of a signal applied to the amplifier f22, and a power supply modulation voltage (bungee voltage) that is applied to the amplifier 22. The power supply modulation unit 31 and the control unit 32 that controls the distortion compensation unit 30 and the power supply modulation unit 31. The pre-corrector 30 performs distortion compensation processing on the signal (distortion-compensated pre-baseband signal) X(n) according to the distortion characteristic of the amplifier 22, and obtains the fe number (distortion-added baseband fg number) u (η) By. The distortion compensation is performed by previously adding the inverse characteristic of the distortion characteristic of the amplifier 22 to the signal χ(η). The output ζ(η) with less distortion is obtained from the amplifier 22 by giving the output signal u(n) of the predistorter 30 which has been subjected to distortion compensation in advance to the amplifier 22'. Hereinafter, a power series model (PSM: Power S eries Model) showing the distortion compensation characteristic of the pre-aligner 30 PS PS Μ u of the distortion compensation characteristic of the pre-aligner: Amplifier-compensated amplifier input U = Z Sj#xj Coefficient (parameter of the inverse characteristic of the amplifier) Amplifier input before distortion compensation 12- 200838125 Power supply modulation section 3 1 Envelope of the input signal (output signal of pre-aligner 30) u (η) according to amplifier 22 (enve 1 The amplitude of the power supply voltage v(n) given to the amplifier 22 is varied. That is, the power supply modulation unit 31 has a small power supply voltage v(n) when the input signal u(n) (the envelope amplitude) is small, and the power supply when the input signal u(n) (the envelope amplitude) is large. The voltage v(n) is also large to determine the power supply modulation voltage v(n) as a function of the input signal u(n). The power supply modulation unit 31 can determine the power efficiency of the amplifier 22 by determining the power supply modulation voltage v(n) according to the input signal u(n). Hereinafter, a power series model (PSM) of the power supply modulation characteristic of the power supply modulation unit 31 is displayed.

PSM of power modulation characteristics: power supply modulation voltage v = ^ £j#uJ coefficient (parameter of power modulation characteristics) V: amplifier input control section 32 has control pre-corrector 30 from distortion compensation pre-signal x ( n) A function of determining the parameter (the parameter of the parameter two-distortion compensation characteristic of the inverse characteristic (inverse model) of the amplifier 22) for the distortion compensation signal u(n). Since the parameters of the predistorter 30 can be adjusted, the distortion compensating property can be freely adjusted by appropriately determining the parameters of the predistorter in the control unit 32. Further, the control unit 32 has a function of controlling the power supply modulation unit 31 to determine the parameter h for the power supply modulation voltage v(n) from the amplifier input signal (pre-corrector output signal) u(n). Since the parameters of the power supply modulation unit 31 can be adjusted, the power modulation characteristics can be freely adjusted by appropriately setting the parameters of the power supply modulation unit 31 in the control unit 3 2, and thus freely adjustable. The efficiency of the amplifier 22 is adjusted. As described above, since the control unit 32 can separately control the parameters of the predistorter 30 and the power supply modulation unit 31, the power modulation characteristics and the distortion compensation characteristics of the amplifier 22 can be separately controlled. Therefore, as will be described later, adaptive control of both the power modulation characteristics and the distortion compensation characteristics of the amplifier 2 can be performed, and the optimum amplifier characteristics of "maximum efficiency and minimum distortion" can be obtained. F% In addition, the control that sacrifices efficiency and distortion, and improves the performance of the other side, can also be adjusted by parameters. In order to obtain the amplifier characteristics in which the efficiency of the amplifier 22 is the largest and the distortion is the smallest, the control unit 32 of the present embodiment includes an amplifier model 32a, an efficiency characteristic model 32b of the amplifier, and an evaluation unit 32c. The amplifier model 32a here is constructed as a PA inverse model of the inverse characteristic of the non-linear characteristic of the display amplifier (PA) 22. In other words, when the amplifier model 32a is supplied with the amplifier output z(n) and the power supply modulation voltage v(n), the estimation of the input of the amplifier can be performed according to the parameter g. The method for determining the parameter g will be described later. The power series model (pSM) of the non-linear characteristic of 22, and the power series model (PSM) of the nonlinear inverse characteristic (PA inverse model) of the amplifier 22 are as follows. PS of the non-linear characteristic of the amplifier Μ -14- 200838125 Z : Amplifier output z = · v1 ®uJ Pu : coefficient (parameter)

iJ V1: power supply modulation voltage V: estimation of the non-linear inverse characteristic of the amplifier input amplifier p S μ amplifier input :^: coefficient (parameter of the inverse characteristic of the amplifier u = y g. ^v1· zj tr J number): power supply Variable Voltage: Amplifier Output In addition, the control unit 32 calculates an error e(n) between the estimated input signal of the amplifier calculated from the PA inverse model of the amplifier model 32a and the actual amplifier input signal. This error e(n) is given to the evaluation unit 32c. In addition, the arithmetic expression of the error e(n) is as follows. The error e(n) e(n) = u(n) - ύ(η) of the amplifier input signal u(n) and the estimated input signal ύ(η). In addition, the efficiency characteristic model 32b at this time is the same as the amplifier 22. The inverse function of the extreme efficiency characteristic (power efficiency characteristic) W (efficiency inverse model) // constitutes. The inverse function // is as follows

The inverse characteristic of the efficiency characteristic of the amplifier V PSM -15- 200838125 = Zfu#yi#zj fu : coefficient (known parameter of efficiency characteristic) V1 : power supply modulation voltage Z": amplifier output the efficiency characteristic model 3 2b in advance The control unit 32 is provided. In other words, when the control unit 32 applies the efficiency characteristic parameter f in the inverse function in advance, and the power supply modulation voltage v (η) and the amplifier output z (η) are applied to the control unit 32, the control unit 32 can calculate The inverse of the efficiency of 7? 値 / /. Further, since the efficiency characteristic (the parameter) differs depending on the power supply modulation voltage, the efficiency characteristic parameters of the various power supply modulation voltages and the amplifier input signals are measured in advance, and the efficiency characteristic parameters are stored in the control unit 32. In addition, the efficiency characteristic can also be expressed by the relationship between the power supply modulation voltage ν(η) and the amplifier input u(n). The evaluation unit 3 2c is given /z calculated as above. The evaluation unit 32c optimizes the error e(n) by minimizing the error e(n) based on the error e(n) and the inverse function of the given value 値 //, and minimizes it. Specifically, the evaluation unit 32c has the following evaluation function for reducing the error (distortion) e (η) of the amplifier and the inverse function 效率 of the efficiency characteristic, and performs the process of reducing the evaluation function.

Evaluation function J = (8) + αμ2 § System & vector representation iW system & vector representation At this time, due to the aforementioned error (distortion) e(n) is the difference between the amplifier input signal and the -16 - 200838125 estimated input signal, When the amplifier output z(n) and the power supply modulation voltage v(n) are given, it is determined by the coefficient (parameter) g of the PA inverse model 32. In addition, the power supply modulation voltage v(n) is determined by the coefficient (parameter) h of the power supply modulation characteristic when the amplifier input u(n) is applied. Furthermore, the inverse function of the efficiency 7// when the amplifier output z(n) and the power supply modulation voltage v(n) are given, the power supply modulation voltage v(n) is determined by the known coefficient (parameter) f. When the input u(n) is given to the amplifier, it is determined by the power supply modulation "the coefficient of the characteristic (parameter) h. Therefore, the evaluation unit 32c adapts the coefficient of the PA inverse model of the control amplifier model 32a (amplifier model) The parameter g) and the coefficient of the power modulation characteristic (the parameter for determining the power supply modulation voltage) h can minimize the aforementioned evaluation function. More specifically, the evaluation unit 32c minimizes the evaluation function by the gradient method operation. The parameters of the PA inverse model of the amplifier model 32a (parameters of the amplifier model) g and the power modulation characteristics are determined successively by the gradient method, and the parameters of the parameters (the parameters used to determine the power supply modulation voltage) h are as follows: In addition, the algorithm for optimizing the parameters is not limited to the gradient method. The parameter adaptation rule by the gradient method g is adapted to the law [J g(h + l) 4(8) one-step adaptation rule £ (h+ i) = ii(8)- ah rg is the step of the vector The parameter rh is a step parameter of the vector έ* 共 conjugate (vector) -17- 200838125 As described above, the control unit 32 adapts to the inverse of the amplifier 22 that determines the input and output signals of the amplifier and the power supply modulation voltage. The model (polynomial approximation) is sequentially determined by the coefficient 値 (parameter of the amplifier model 32a) g. Further, the control unit 32 uses the coefficient 値.g of the adaptive amplifier model 32a, the amplifier input/output signal u(n), z. (n), the power supply modulation voltage ν(η), and the efficiency characteristic model 32b of the amplifier, and the parameter h for determining the power supply modulation voltage is successively determined. As a result, the same as the distortion compensation by the predistorter 30, successively The optimum power modulation characteristics of the input signal are calculated to perform adaptive control of both the power modulation characteristics and the distortion compensation characteristics. Therefore, when the control unit 32 of the present embodiment is used, the amplification circuit itself can be automatically performed. The efficiency and distortion characteristics of the amplifiers of the trade-off relationship are optimized. Thereby, the power modulation characteristics can be more precise than before, and the distortion performance can be accommodated in the specifications, and In addition, the fluctuation of the characteristics of the amplifier can be sufficiently matched. Further, when the control unit 32 of the present embodiment is used, the software and the circuit design can be changed without changing the modulation mode of the transmission signal. In addition, in order to sacrifice some efficiency or distortion and improve the performance of the other side, it is only necessary to change the parameters, and the adjustment can be easily performed. The present invention is not limited to the above embodiment, and various modifications can be made. The present invention will be described in detail with reference to the preferred embodiments of the present invention. It will be understood by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The present application is based on January 19, 2007- 200838125 Japanese Patent Application (Japanese Patent Application No. 2007-010181), the contents of which are hereby incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a wireless communication system. Fig. 2 is a diagram showing the hardware configuration of the amplifier circuit. Figure 3 is a functional block diagram of the amplifier circuit. Figure 4 is a functional block diagram of the prior amplification circuit. [Description of main components] la radio base station lb, lc, Id terminal device 11 receiver 1 la low noise amplifier circuit 12 transmitter 12a power amplifier circuit 13 processing unit 21 digital signal processing unit 22 RF power amplifier 23 envelope amplifier 24 DA converter 25 low pass filter 26 up converter 27 band pass filter 28 driver 29a down converter 29b low pass filter -19- 200838125 f 29c AD converter 30 predistorter (distortion compensation unit) 3 1 Power supply modulation unit 32 Control unit 32a Amplifier model 32b Efficiency characteristic model 32c Evaluation unit 100 Power amplifier 101 Power supply modulation unit 102 PA inverse model identification unit 103 Pre-aligner

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Claims (1)

200838125 X. Patent application scope: 1. An amplifying circuit, comprising: an amplifier; a power supply modulation unit, which determines a power supply modulation voltage applied to the amplifier according to an input signal of the amplifier; a distortion compensation unit Performing distortion compensation of the amplifier according to an amplifier model showing characteristics of the amplifier; and a control unit for controlling the power supply modulation unit and the distortion compensation unit; wherein the control unit is based on an output signal and an input signal of the amplifier, and The power supply modulation voltage of the amplifier is given to determine the configuration of the amplifier model, and the parameter for determining the power supply modulation voltage is controlled in accordance with the amplifier model. 2. The amplifying circuit of claim 1, wherein the control unit minimizes a difference between an input signal of the amplifier and an estimated input signal of an amplifier obtained by the amplifier model, and maximizes amplifier power efficiency. Then, the configuration for determining the parameters of the power supply modulation voltage is determined. 3. The amplifying circuit of claim 2, wherein the control unit minimizes the aforementioned difference and maximizes the aforementioned efficiency by a gradient method. 4. The amplifier circuit according to any one of claims 1 to 3, wherein the control unit obtains a parameter for determining the power supply modulation voltage, and uses: the foregoing amplifier model expressed in a power series And a function of the power supply modulation voltage expressed in power series for the input signal of the aforementioned amplifier - 21-200838125. 5. An amplifier circuit, comprising: an amplifier; a power supply modulation unit that determines a power supply modulation voltage applied to the amplifier according to an input signal of the amplifier; and a control unit that controls the power supply modulation unit A parameter used to determine the aforementioned power supply modulation voltage. 6. An amplification circuit characterized by comprising: ί ' amplifier; a power supply modulation unit that determines a power supply modulation voltage applied to the amplifier according to an input signal of the amplifier; and a distortion compensation unit that displays the amplifier according to the display The amplifier model of the characteristic performs distortion compensation of the amplifier; and a control unit that can control parameters of the amplifier model together and parameters for determining a power supply modulation voltage applied to the amplifier from an input signal of the amplifier. A wireless communication device is provided with the amplifying circuit of any one of claims 1, 2, 3, and 5 in order to amplify a transmission signal or amplify a received signal. 8. A wireless communication device comprising the amplifying circuit of claim 4 in order to amplify a transmission signal or amplify a received signal. -twenty two-