Logarithmic detector based on input frequency dynamic compensation

Abstract

A logarithmic detector based on input frequency dynamic compensation comprises a logarithmic amplifier for receiving a radio frequency signal, performing logarithmic conversion and outputting a first current; the frequency discriminator determines first frequency information according to a radio frequency signal, and the first frequency information indicates a first frequency of the radio frequency signal; the control module is used for generating a first control signal and a second control signal based on the first frequency information; wherein the first control signal is used for controlling the magnitude of the second current; the second control signal is used for controlling the magnitude of the third current; the temperature compensation circuit comprises a first transistor with a temperature coefficient and a current adjusting circuit; the first transistor is used for generating a second current changing along with the temperature; the current adjusting circuit adjusts the magnitude of the second current based on the first control signal; and the intercept compensation circuit outputs a corresponding third current based on the second control signal.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a logarithmic detector for dynamically compensating output current based on input frequency. Background Art

[0002] Detectors are usually used to measure the amplitude or power of a signal and are widely used in wireless systems. They can be simply divided into two categories: logarithmic detectors (or envelope detectors) and root mean square (RMS) detectors. See Figure 1 , which shows the detection results of the logarithmic detector and the RMS detector for the same RF signal. Figure 1 As shown in the figure, the RF signal is a high-frequency sine wave whose amplitude / phase changes with time. The logarithmic detector will detect the envelope output of the input signal, usually its logarithmic value, which is the output result 1 in the figure; the RMS detector will detect the root mean square value (or power value) of the input signal and output it, which is the output result 2 in the figure. Its output voltage does not change with the shape of the signal or the peak-to-average ratio. The peak-to-average ratio refers to the peak-to-average power ratio (PAPR), such as Figure 1 As shown, for the signal value of the RF input signal, the amplitude of the high-frequency sinusoidal wave oscillation is not fixed, and the ratio of the power corresponding to the peak value to the power corresponding to the average value is the peak-to-average ratio.

[0003] Whether the logarithmic detector circuit is designed using a bipolar transistor (BJT) or a metal-oxide semiconductor field-effect transistor (MOSFET), the device will have certain temperature characteristics. For the same circuit design, when the chip operating temperature is different, the circuit gain and other parameters may be different, resulting in different intercepts of the final output logarithmic curve at different temperatures, so the circuit needs to be temperature compensated.

[0004] Logarithmic detectors have broadband applications. When the input signal frequency is different, the temperature characteristics of the entire logarithmic detector may be slightly different. In other words, the intercept of the logarithmic curve will also be slightly different when the frequency is different. Therefore, the circuit needs to be compensated according to the frequency of the input signal.

[0005] Some designs provide a manual temperature compensation control port outside the chip, which can be used to manually adjust the temperature compensation information according to the usage scenario. However, this method increases the complexity of the circuit on the one hand, and can only perform temperature compensation on a certain frequency at a time on the other hand, which limits the broadband application of the logarithmic detector. Summary of the invention

[0006] In order to solve the influence of temperature and frequency of RF signal on logarithmic detector, the present application proposes a logarithmic detector based on frequency compensation logarithmic curve, which can automatically compensate according to temperature and frequency of RF signal to improve detection accuracy.

[0007] In some embodiments, the logarithmic detector based on the frequency compensation logarithmic curve includes: A logarithmic amplifier, used for receiving a radio frequency signal, wherein an output terminal of the logarithmic amplifier outputs a first current; a frequency discriminator, configured to determine first frequency information according to the radio frequency signal, wherein the first frequency information indicates a first frequency of the radio frequency signal; A control module generates a first control signal and / or a second control signal based on the first frequency information; wherein the first control signal is used to control the temperature coefficient of the second current at different first frequencies, and the second current is used to compensate for the first current at different temperatures; and the second control signal is used to control the magnitude of the third current, and the third current is used to compensate for the first current at different first frequencies.

[0008] A temperature compensation circuit is used to generate the second current that changes with temperature to compensate for the change of the first current caused by temperature, thereby compensating for the intercept change of the logarithmic curve caused by the temperature change; the temperature compensation circuit also receives the first control signal, and based on the first control signal, changes the temperature coefficient of the second current to compensate for the influence of different frequencies on the temperature coefficient of the second current; through the double compensation of the temperature compensation circuit, the intercept change of the logarithmic curve caused by temperature and frequency changes can be compensated; and / or, The intercept compensation circuit outputs the corresponding third current based on the second control signal to compensate for the magnitude of the first current at different first frequencies, thereby compensating for the intercept change of the logarithmic curve caused by the change of frequency.

[0009] The entire process does not require manual adjustment. The temperature and / or intercept compensation effect can be obtained through the frequency discriminator, control module output, temperature compensation circuit and / or intercept compensation circuit, realizing wide-band optimal temperature compensation and / or intercept compensation, and the circuit complexity is low.

[0010] In some embodiments, the logarithmic detector includes both a temperature compensation circuit and an intercept compensation circuit to achieve two-stage current regulation: the temperature compensation circuit can adjust the intercept of the logarithmic curve based on the first frequency of the input AC RF signal; the intercept compensation circuit can adjust the intercept of the logarithmic curve based on the first frequency of the input AC RF signal, thereby achieving automatic and flexible adjustment of the intercept of the logarithmic curve. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1It is a schematic diagram of the detection results of the logarithmic detector and the RMS detector for the same RF signal.

[0012] Figure 2 It is a structural diagram of a logarithmic detector.

[0013] Figure 3 It is a logarithmic curve of the input power and detection voltage output of the logarithmic detector at the same frequency and different temperatures.

[0014] Figure 4 It is a logarithmic curve after temperature compensation.

[0015] Figure 5 It is a logarithmic curve of the input power and detection voltage output of the logarithmic detector at the same temperature and different frequencies.

[0016] Figure 6 is a schematic diagram of a logarithmic detector according to an embodiment of the present application.

[0017] Figure 7 is a schematic diagram of a frequency discriminator in a logarithmic detector according to an embodiment of the present application.

[0018] Figure 8 It is a working flow chart of the control module in the logarithmic detector according to the embodiment of the present application.

[0019] Fig. 9 is a schematic diagram of a temperature compensation circuit in a logarithmic detector according to an embodiment of the present application.

[0020] Fig.10 is a schematic diagram of another temperature compensation circuit in a logarithmic detector according to an embodiment of the present application.

[0021] Fig.11 is a schematic diagram of an intercept compensation circuit in a logarithmic detector according to an embodiment of the present application.

[0022] Fig.12 is a schematic diagram of another intercept compensation circuit in a logarithmic detector according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is understood that the specific embodiments described herein are only used to explain the relevant disclosure, rather than to limit the disclosure. It should also be noted that, for the convenience of description, only the parts related to the relevant disclosure are shown in the drawings.

[0024] First, the terms involved in this application are explained: Logarithmic curve: A curve showing the change of the output DC detection voltage signal of the logarithmic detector as the input signal changes. The horizontal axis of the logarithmic curve is the signal power of the input RF signal. For example, the unit of the RF signal power can be decibel milliwatt (dBm). The vertical axis of the logarithmic curve is the DC detection voltage of the output signal, which can be in volts (V) or millivolts (mV).

[0025] The intercept of the logarithmic curve is the input power corresponding to the intersection of the logarithmic curve and the horizontal axis. The intercept of the logarithmic curve can also be understood as the output offset of the logarithmic detector.

[0026] refer to Figure 2 , which shows a schematic diagram of the structure of a logarithmic detector. The logarithmic detector includes a logarithmic amplifier 200, which is used to logarithmically amplify the input signal. The logarithmic amplifier 200 includes a plurality of cascaded limiting amplifiers (such as amplifiers 201-205) and a plurality of rectifiers (such as rectifiers 210-260), wherein the limiting amplifier is used to amplify the AC signals of each level, and the rectifier is used to rectify the AC signal into a DC signal, and the DC signal has a logarithmic relationship with the input signal. The input end of the first-stage limiting amplifier 201 receives the AC radio frequency signal RFin input to the logarithmic detector, and is connected to the input end of the first-stage rectifier 210. In addition, the output end of each amplifier circuit is connected to the input end of a rectifier, and the output ends of all rectifiers are connected together to form the output end of the logarithmic amplifier, which is used to output a DC output signal Iout. The DC output signal Iout can be converted into a voltage to form a DC detection voltage signal; and the output end of the last-stage limiting amplifier 205 outputs a radio frequency voltage signal RFout. Since the limiting amplifier gain changes with temperature, a compensation current can be added to the output current of the logarithmic amplifier to compensate for the current change caused by temperature. Figure 2 The compensation current 21 is connected at Iout in.

[0027] Figure 3 The logarithmic curves of the input power and the detection voltage output of the logarithmic detector at the same frequency and different temperatures are shown in Figure 301, where curve 301 is a low temperature logarithmic curve, curve 302 is a normal temperature logarithmic curve, and curve 303 is a high temperature logarithmic curve. The limiting amplifier includes a bipolar transistor (BJT), and the transconductance of the BJT can be obtained by the following formula: g m =I C / V T , where g m is the transconductance, I C is the input current, V T is the thermal voltage, V T Related to temperature. Generally speaking, the higher the temperature, the higher the V TThe higher the limiter, the gain of the limiting amplifier can be obtained by the following formula: V =g m ×R L , where A V is the gain, R L is the load resistance. When the temperature of the BJT increases, its thermal voltage V T It increases with the increase of temperature, so the transconductance g m will decrease as the temperature increases, and the gain A of the limiting amplifier V It will also decrease with increasing temperature, and the detector requires the input signal strength to reach a certain value before it can respond. Therefore, the higher the temperature, the smaller the gain of the logarithmic amplifier, causing the starting point of the detected voltage to shift to the right. That is, the higher the temperature, the greater the input signal power required to generate the same detection voltage (that is, the RF voltage signal RFout).

[0028] Therefore, in order to obtain the same logarithmic curve at different temperatures, that is, to make the zero point of the logarithmic curve the same at different temperatures, a temperature compensation circuit can be introduced at the DC output terminal Iout of the logarithmic amplifier to generate a temperature compensation current. The temperature compensation current causes the logarithmic curve to shift upward or downward accordingly, and finally makes the logarithmic curves overlap at different temperatures. For example, Figure 3 The curve 301 and the curve 303 shown in FIG. 3 are both overlapped with the curve 302 by translation. Figure 4 The curve in is the curve after the three curves overlap. It can be understood that there are other temperature effects in the logarithmic detector, and the above description is only a simplified example for the convenience of explanation.

[0029] The relationship between the temperature compensation current output in the temperature compensation and the temperature can be simplified to a functional relationship Y=kX+b, where Y is the temperature compensation current, X is the temperature, k is the temperature coefficient of the temperature compensation circuit, and b is the intercept. It can be seen from the above functional relationship Y=kX+b that in addition to the temperature X, there are two factors that affect the temperature compensation current Y: 1) intercept b; 2) temperature coefficient k.

[0030] In view of the influence of intercept b, it is often necessary to introduce an intercept compensation circuit with a zero temperature coefficient to generate an intercept compensation current to perform intercept compensation.

[0031] The temperature coefficient k varies with the frequency of the input AC RF signal. If the temperature coefficient k cannot vary with the frequency, only a good temperature compensation can be achieved for one input signal frequency point.

[0032] In addition, since the frequency of the input AC RF signal will also have a certain impact on the gain of the limiting amplifier, when the frequency is different, the gain of the limiting amplifier is different, which makes the corresponding RFIN different when the last stage rectifier enters the normal working input power range, so that the intercept size of the logarithmic curve is also different after the same intercept compensation, such as Figure 5 As shown, curves 501, 502, and 503 are obtained at the same temperature and different frequencies. Figure 3 The generated compensation current shown (including the generated traditional temperature compensation current and intercept compensation current) cannot be adaptively adjusted as the frequency changes. For example, when the current is compensated, the three curves will be translated simultaneously and equally spaced along the y-axis direction, and the three curves will not overlap, so the influence of frequency on the output current cannot be improved.

[0033] In order to solve the problem that the temperature coefficient k and the intercept b cannot automatically change with the frequency, it is necessary to provide the compensation circuit with the frequency information of the input signal and automatically adjust the compensation current according to the information. The present application adopts a solution of adding a frequency discriminator and a control module, wherein the frequency discriminator is used to determine the frequency of the input RF signal, and the control module is used to generate a corresponding control signal to control the magnitude of the compensation current.

[0034] Figure 6 This is an embodiment of the logarithmic detector based on the frequency compensation logarithmic curve proposed in the present application. The logarithmic detector includes a logarithmic amplifier 601, a frequency detector 602, a control module 603, a temperature compensation circuit 604 and an intercept compensation circuit 605. The structure of the logarithmic amplifier 601 can refer to Figure 2 The structure of the logarithmic amplifier 200 is not described in detail here.

[0035] The logarithmic amplifier 601 is used to receive the input of the radio frequency signal RFin, and after logarithmic conversion of the radio frequency signal RFin, its output terminal outputs a first current. Figure 6 The first current in the frequency detector 602 is the current Iout. The input end of the frequency detector 602 can be connected to the input end of the logarithmic amplifier 601, or can be connected to the input end or output end of any level limiting amplifier in the logarithmic amplifier 601. The frequencies of these positions are the same as the frequency of the radio frequency signal RFin, so as to reflect the frequency of the radio frequency signal RFin. The frequency detector 602 collects the frequencies of these positions to determine the first frequency information according to the radio frequency signal RFin. The first frequency information is used to indicate the first frequency of the radio frequency signal RFin. f 1 , wherein the first frequency information may include the first frequency f 1 , or for calculating the first frequency f 1The frequency discriminator 602 is used to detect the frequency of the radio frequency signal RFin. Specifically, the radio frequency signal in the form of power is input to the logarithmic detector, converted into a radio frequency voltage signal through the logarithmic amplifier, and finally outputs the radio frequency voltage RFout. The frequency discriminator 602 can determine the first frequency of the input radio frequency signal RFin according to the radio frequency signal input or output at any stage of the logarithmic amplifier. f 1 It is understandable that since the logarithmic detector converts the power or amplitude change of the RF signal RFin into the change of the output voltage or current, it will not affect the frequency of the RF signal RFin. Therefore, the first frequency of the RF signal RFin at the input end of the logarithmic detector is f 1 The frequency of the output voltage RFout and the output current Iout at the output end is equal, and the first frequency of the input RF signal RFin can be determined according to the RF signal input or output at any stage of the logarithmic amplifier. f 1 .

[0036] The control module 603 generates a first control signal and a second control signal based on the first frequency information. The first frequency information has a corresponding relationship with the first control signal and the second control signal. When the first frequency information is different, the first control signal and the second control signal are different. The first control signal and the second control signal change with the first frequency information to compensate for the influence of the frequency change of the radio frequency signal RFin according to the first frequency information. Among them, the first control signal reflects the compensation for the change of the temperature coefficient caused by the change of the second current with the frequency, and the second control signal reflects the compensation for the change of the intercept caused by the change of the logarithmic curve with the frequency. The first control signal and the second control signal can be multi-bit digital signal control codes in binary form, which can be easily compensated. Specifically, when the first frequency information determined by the discriminator only includes parameters for determining the first frequency, the parameters can be processed in the control module 603 to obtain the first frequency f 1 ; When the first frequency information includes the first frequency f 1 When the control module 603 can directly obtain the first frequency f 1 .

[0037] The temperature compensation circuit 604 is used to output the size of the corresponding second current based on the first control signal. The output end of the temperature compensation circuit 604 is connected to the output end of the logarithmic amplifier 601. The second current is used to compensate the first current at different frequencies. The second current can reflect the change in temperature and can reflect the change in temperature with the first frequency. The first control signal has a corresponding relationship with the size of the second current. When the first control signal is different, the size of the second current is different.

[0038] The intercept compensation circuit 605 is used to output the size of the corresponding third current based on the second control signal. The output end of the intercept compensation circuit 605 is connected to the output end of the logarithmic amplifier 601. The third current is used to compensate the first current at different frequencies. The second control signal and the size of the third current have a corresponding relationship. When the second control signal is different, the size of the third current is different.

[0039] Since the temperature and the first frequency change in real time, the compensation process is carried out in real time, so the acquisition of the first frequency and the generation of the control signal are also carried out in real time according to the frequency of the radio frequency signal. By applying the above circuit, the discriminator can automatically detect the first frequency of the radio frequency signal at a certain frequency, and the control module automatically determines the first control signal and the second control signal based on the first frequency. The first control signal is used to control the temperature coefficient of the second current at different first frequencies to compensate for the influence of different frequencies on the temperature coefficient of the second current; the temperature compensation circuit is also used to generate a second current that changes with temperature to compensate for the change of the first current caused by temperature, thereby compensating for the intercept change of the logarithmic curve caused by temperature change; through the double compensation of the temperature compensation circuit, the intercept change of the logarithmic curve caused by temperature and frequency changes can be compensated. The second control signal is used to control the size of the third current, and the third current is used to compensate the first current at different first frequencies to compensate for the intercept change of the logarithmic curve caused by frequency change; thereby realizing automatic and flexible adjustment of the intercept of the logarithmic curve.

[0040] The entire process can automatically obtain frequency and temperature compensation effects at a certain operating frequency without manual adjustment, achieving broadband optimal temperature compensation and intercept compensation, and the circuit complexity is low.

[0041] The above is the basic structure of the logarithmic detector proposed in this application. Figure 6-Figure 11 Let's explain the various parts of the logarithmic detector in detail.

[0042] First refer to Figure 7 , an implementation of the frequency discriminator 602 is described. The frequency discriminator 602 includes a reference frequency source 701, a first counter 702, a second counter 703 and a calculation unit 704. The reference frequency source 701 is used to output a reference signal, and the frequency of the reference signal is the reference frequencyf 2 , as a basis for comparison, that is, the reference signal is used as a reference signal of the RF signal. By comparing the frequency of the reference signal with the frequency of the reference signal, the frequency of the RF signal can be obtained. The reference signal can be a pulse signal. The first counter 702 is used to count the pulses of the RF signal to obtain a first count C 1 The first counter 702 can convert the RF signal into a pulse signal and count the pulses after shaping. The second counter 703 is used to count the pulses of the reference signal to obtain a second count C 2 In this embodiment, the calculation unit 704 is used to calculate the value of the first count C 1 and the second count C 2 ratio, and the reference frequency f 2 , to calculate the first frequency f 1 Since the frequency is linearly proportional to the number of pulses within a certain period of time, the ratio of the number of pulses of the RF signal to the reference signal within a certain period of time is equivalent to the ratio of the frequency of the RF signal to the reference signal.

[0043] Therefore, within a certain counting time, the ratio of the frequency of the RF signal to the reference signal to the count is as shown in the following formula (1):

[0044] By transforming the above formula, the first frequency can be obtained through formula (2): f 1 :

[0045] In this solution, the calculation unit 704 in the frequency discriminator 602 is used to calculate the first frequency f 1 , so the first frequency information is the first frequency f 1 , the calculation unit 704 can convert the first frequency f 1 Sent to the control module.

[0046] Reference frequency f 2 , first count C 1 and the second count C 2 That is, the parameter used to determine the first frequency in the first frequency information. However, in other embodiments, the frequency detector 602 may not include the calculation unit 704. The calculation unit 704 may be located in the control module, and the control module calculates the first frequency. f 1 For example, the frequency detector 602 can count the first1 and the second count C 2 The control module can then use the pre-known reference frequency to f 2 , get the first count C 1 and the second count C 2 , according to formula (2) we can get the first frequency f 1 At this time, the first frequency information is the first count C 1 and the second count C 2 , the first count C 1 and the second count C 2 is a parameter used to determine the first frequency. In other embodiments, the calculation unit 704 may also be an independent module, or integrated with other modules.

[0047] In addition, the frequency discriminator 602 may also include a clear signal input terminal 705 connected to the first counter 702 and the second counter 703, and used to clear the counts of the first counter 702 and the second counter 703. The clear signal input terminal 705 can be controlled by the control module 603. When receiving the clear signal CLR output by the control module 603, the count data of the first counter 702 and the second counter 703 will be cleared to indicate the counting starting point, thereby eliminating the process of determining the counting starting point of this cycle, and the count value of the counter is the required first count and second count, which can save computing resources.

[0048] It is worth noting that the amplitude of the RF signal input to the counter needs to be large enough to make the counter count accurately. Therefore, Figure 6 As shown, the discriminator 602 can be arranged at the RF voltage output terminal of the logarithmic amplifier 601, and the amplitude of the RF signal outputted from the RF voltage output terminal of the logarithmic amplifier 601 is relatively large. Optionally, a gain amplifier 608 can be inserted between the logarithmic amplifier and the discriminator to amplify the amplitude of the RF signal to be sufficient to drive the discriminator 602, thereby avoiding the situation where the discriminator 602 cannot work normally.

[0049] In addition, in other embodiments, the frequency discriminator may also include an analog-to-digital converter ADC and a calculation unit, wherein the analog-to-digital converter is used to perform analog-to-digital conversion on the input RF signal, and convert the analog RF signal into a digital signal. The calculation unit can calculate the first frequency of the RF signal according to the digital signal through mathematical calculations such as Fourier transform in the digital domain. In another implementation, the frequency discriminator may include an analog-to-digital converter ADC but not a calculation unit, and mathematical calculations such as Fourier transform may be performed by the control module 603. Among them, the Fourier transform may adopt the following formula:

[0050] Wherein, F(m) is the first frequency, m is the harmonic number, n is the current operation point, and M represents the number of n.

[0051] It can be understood that the above frequency discriminator is only an example, and the frequency discriminator can also detect the frequency in other ways.

[0052] Next, the control module 603 in this embodiment is described.

[0053] In one embodiment, the control module 603 may be a logic circuit including a lookup table 609, and the control module 603 determines the first control signal and the second control signal based on the first frequency information received from the frequency discriminator 602. The circuit logic may be implemented using a pure digital circuit, for example, the hardware description language Verilog HDL is usually used to write behavioral level code, so as to generate a circuit through program synthesis. The lookup table 609 stores a frequency correspondence relationship, and the frequency correspondence relationship indicates the first control signal and the second control signal at different first frequencies. That is, different first frequencies may correspond to different first control signals and second control signals. The control module may be based on the first frequency f 1 and frequency correspondence, determine the first control signal and the second control signal, when the first frequency f 1 When the frequency detector detects the first frequency, the first control signal and the second control signal change accordingly to compensate for the change in the intercept of the logarithmic curve caused by the frequency change. f 1 When the first frequency is 350kHz, the first control signal may be V11 (for example, 11001001), and the second control signal may be V21 (for example, 1001101). f 1 When the first control signal is 700kHz, the first control signal may be V12 (for example, 01111001), and the second control signal may be V22 (for example, 0111100). Furthermore, the frequency correspondence may also be that the first frequency f 1 The corresponding relationship between the frequency range (the frequency range can be customized according to the accuracy requirements during circuit design) and the first control signal and the second control signal. For example, when the first frequency f 1 When the frequency is within the range of 340kHz to 350kHz, the first control signal may be V11 (e.g. 11001001), and the second control signal may be V21 (e.g. 1001101). f 1When the frequency is within the range of 690kHz to 710kHz, the first control signal may be V12 (e.g. 01111001), and the second control signal may be V22 (e.g. 0111100). It is understood that the above examples are only for illustrating the corresponding manner of the frequency correspondence, and do not represent actual values. For example, the number of bits of the control signal is related to the actual structure of the compensation circuit, and the first frequency f 1 The relationship between the size of and the value of the control signal also needs to be judged based on the actual circuit.

[0054] Before the logarithmic detector leaves the factory, for a certain first frequency and a certain real-time temperature, different first control signals are input to the temperature compensation circuit, and different second control signals are input to the intercept compensation circuit; for different first control signals and second control signals, the logarithmic curve of the logarithmic amplifier is tested respectively; when the input first control signal and second control signal make the logarithmic curve the target logarithmic curve, the first control signal and the second control signal are the target first control signal and the target second control signal for a certain first frequency and a certain real-time temperature. Polling is performed sequentially to find the target first control signal and the target second control signal for all first frequencies and all real-time temperatures, so as to obtain the frequency correspondence, and store the frequency correspondence in the lookup table.

[0055] It is understandable that the control module 603 generates the corresponding control signal based on the lookup table is only an embodiment, and in other embodiments, the frequency correspondence relationship can also be fitted into a frequency function relationship, and the frequency function relationship is a function of calculating the first control signal and the second control signal according to the first frequency. Therefore, when the first frequency is obtained, the control module 603 will bring the first frequency into the frequency function relationship to calculate the corresponding first control signal and the second control signal.

[0056] The control module 603 is configured to perform the following operations to compensate the first current: Obtaining first frequency information to obtain a first frequency; searching a first control signal and a second control signal in a lookup table according to the first frequency; The first control signal and the second control signal are transmitted to the temperature compensation circuit and the intercept compensation circuit respectively.

[0057] refer to Figure 8 Flowchart, combined with Figure 6 , Figure 7 , to illustrate the working process of the control module 603. In this embodiment, the control module 603 includes a reference frequency source 701, a first counter 702, and a second counter 703, but does not include a calculation unit 704.

[0058] In step 801, the control module 603 sends a clear signal CLR at a second frequency to the frequency discriminator 602 to start a new round of compensation control. In other examples, clearing may not be performed, but the count before the new round of control time point is subtracted during the calculation process.

[0059] In step 802, after the first counter 702 and the second counter 703 count for a period of time, the control module 603 receives the first count C 1 and the second count C 2 In this step, it is necessary to wait for an appropriate amount of time in order to satisfy both the appropriate response speed and the accuracy of the calculation results.

[0060] In step 803, based on the reference frequency stored in the control module 603 f 2 Information, first count C 1 and the second count C 2 The first frequency of the currently input RF signal can be calculated according to the above formula (2): f 1 .

[0061] In this solution, through steps 801 to 803, the first frequency information is obtained with the second frequency to obtain the first frequency.

[0062] In step 804, the control module 603 searches the lookup table 609 for the first frequency f 1 A first control signal and a second control signal (eg, a control code) having a corresponding frequency range.

[0063] In step 805, the first control signal and the second control signal are output to the temperature compensation circuit 604 and the intercept compensation circuit 605, respectively, to adjust the temperature compensation current and the intercept compensation current. It can be understood that the frequency range is determined based on the compensation accuracy requirement. The higher the compensation accuracy requirement, the smaller the defined frequency range.

[0064] It can be understood that step 802 and step 803 correspond to the first frequency information determined by the frequency discriminator including the parameters used to determine the first frequency (the first count C 1 and the second count C 2 ), so the control module needs to receive the parameter and calculate the first frequency based on the parameter f 1 For example, the first frequency information is the first frequency f 1 In the implementation mode, the control module can directly receive the first frequency of the discriminator f 1, that is, step 802 and step 803 can be combined into one step.

[0065] Finally, after starting to work, the control module 603 will execute the above operations cyclically at a certain frequency until the chip is enabled to be turned off or powered off. In addition, the actual circuit implementation can also be designed in a pipeline form.

[0066] Next, the temperature compensation circuit and the intercept compensation circuit are described separately.

[0067] like Figure 6 As shown, the temperature compensation circuit 504 includes a current generating circuit 606 and a first current regulating circuit 607, wherein the current generating circuit 606 is used to generate a second current that varies with temperature, and the second current has a temperature coefficient; the first current regulating circuit 607 regulates the magnitude of the second current based on a first control signal. The temperature compensation circuit 504 can regulate the second current that varies with temperature based on a first frequency, so that the temperature coefficient of the second current varies with the first frequency, so as to change the intercept of the logarithmic curve.

[0068] In some embodiments, the current generating circuit 606 includes a first transistor with a temperature coefficient, wherein the first transistor is used to generate a second current that varies with temperature, and the first transistor can be any transistor with a temperature coefficient. A transistor with a corresponding temperature coefficient can be selected based on different temperature compensation needs. For example, the first transistor can be a BJT transistor, or a MOS transistor, or the required temperature compensation effect can be obtained by changing the direction of current injection. The current regulating circuit 607 is used to adjust the magnitude of the second current based on the first control signal, and the second current is used to compensate for the first current at the same frequency and different temperatures. There is a corresponding relationship between the first control signal and the adjustment of the magnitude of the second current. When the first control signal is different, the magnitude of the second current is different.

[0069] Specifically, refer to Fig. 9 The temperature compensation circuit shown in FIG. 1 includes a first transistor Q1 and a first current regulating circuit 901, wherein the first current regulating circuit 901 includes: a plurality of first resistors R1 <1> ~R1 <4> and a plurality of first switches M1 <1> ~M1 <4> In this embodiment, the first transistor may be an NPN bipolar junction transistor (BJT) Q1, which includes a control terminal P1 (i.e., the base of the BJT Q1), a first terminal P2 (i.e., the emitter of the BJT Q1), and a second terminal P3 (i.e., the collector of the BJT Q1). The control terminal P1 receives a first voltage V B1 The first terminal P2 is connected to the first current regulating circuit 901 via a current limiting resistor R1, and the second terminal P3 is used to output the second current I O2(i.e., temperature compensation current). It is understood that the first transistor can be any suitable transistor with a temperature coefficient, preferably a BJT with stable and predictable temperature characteristics. In addition, the plurality of first switches are implemented by a plurality of MOS tubes and connected to a plurality of first resistors R1 <1> ~R1 <4> The first control signal is used to control the on and off of the first switch of the corresponding position, thereby controlling whether the corresponding first resistor is short-circuited, so as to adjust the resistance value of the branch where the second end P3 of the first transistor Q1 is connected by adjusting the equivalent resistance in the first current regulating circuit 901, thereby adjusting the second current I O2 In addition, CMOS transmission gates and other devices can also be used to replace MOS tubes to achieve the switch function. The first voltage V B1 is a constant voltage with zero temperature coefficient, and the voltage difference V between the base and the emitter (i.e. the first terminal P2) BE is a negative temperature coefficient voltage, so subtract the two (i.e. V B1 -V BE ) can obtain a positive temperature coefficient voltage, and by controlling whether to short-circuit the corresponding first resistor, the positive temperature coefficient voltage can be converted into a positive temperature coefficient current I of corresponding magnitude O2 After receiving the multi-bit first control signal transmitted by the control module 603, the corresponding MOS tube M1 is controlled <1> ~M1 <4> For example, when the digital signal bit corresponding to the control signal of the MOS tube is at a logic high level 1, the MOS tube is turned on to short-circuit the resistor corresponding to the MOS tube, so that the second current I O2 The second current I O2 It can be obtained from the following formula (3):

[0070] Among them, R 1 ' is the resistor R1 <1> ~R1 <4> The resistor that is not short-circuited by the MOS tube.

[0071] Alternatively, in another embodiment, each first switch and each first resistor may be connected in series to form a group, and then all the groups may be connected in parallel, that is, R1 <1> With M1 <1> Connect in series as group 1, R1 <2> With M1 <2> Connect in series to group 2, R1 <3> With M1 <3> Connect in series to group 3, R1 <4> With M1 <4> After being connected in series to form group 4, groups 1 to 4 are then connected in parallel, so as to control the first switch to disconnect the corresponding first resistor through the first control signal, thereby adjusting the magnitude of the second current.

[0072] Fig.101 is a schematic diagram of another embodiment of a temperature compensation circuit, the temperature compensation circuit includes a first transistor Q1 and a first current regulating circuit 1001, wherein the first transistor can be any suitable transistor with a temperature coefficient, and the first current regulating circuit 1001 includes: a first current mirror structure 10011 and a plurality of second transistors 10012. In this embodiment, the control terminal of the first transistor inputs a first voltage V B1 , the first end is grounded via the grounding resistor R2, and the fourth current I is output at the second end o4 The first current mirror structure 10011 of the current regulating circuit 1001 includes a first input transistor M1 and a first output transistor M2. The first input transistor M1 is connected to the first end or the second end of the first transistor Q1; the first output transistor M2 is used to adjust the fourth current I o4 Mirror copy is performed to output a second current; wherein the fourth current I o4 is the current at the second terminal of the first transistor Q1. Fig.10 In the embodiment shown, the first input transistor is a MOS transistor M1, which is connected to the second end of the first transistor for receiving the fourth current output by the first transistor; and the first output transistor is a MOS transistor M2, which is used to output the second current; the first control signal can control the conduction or disconnection of multiple second transistors M3~MN to adjust the equivalent size of the first output transistor, thereby adjusting the size of the second current. Fig.10 In the illustrated embodiment, the second transistor is a plurality of MOS transistors M3 to MN cascaded on the side of the first output transistor, wherein a single-pole double-throw switch is provided at the gate of each of the MOS transistors M3 to MN, one side of the switch is used to connect to the gate of the MOS transistor M2, and the other side is used to connect to the power supply voltage VDD. The first control signal is used to control the conduction position of the single-pole double-throw switch. For example, in an exemplary control logic, when the digital signal bit (not shown) corresponding to the first control signal is at a high level, the single-pole double-throw switch of the MOS transistor corresponding to the bit is connected to the gate of the MOS transistor M2, so that the MOS transistor is connected in parallel with the MOS transistor M2, which is equivalent to increasing the width-to-length ratio of M2, thereby increasing the multiple of the copied fourth current, that is, increasing the output second current; when the digital signal bit is at a low level, the single-pole double-throw switch of the MOS transistor of the corresponding bit is connected to the power supply voltage VDD, and the MOS transistor is turned off, which is equivalent to reducing the width-to-length ratio of M2, thereby reducing the multiple of the copied fourth current, that is, reducing the output second current. Therefore, by controlling whether M3 to MN are connected to the compensation circuit through the control code, the second current I O2 size.

[0073] Furthermore, according to different accuracy requirements, Fig. 9The temperature compensation circuit shown can use different numbers of resistors, resistors with different resistance values ​​and control codes of corresponding bits. Fig.10 The temperature compensation circuit shown can use different numbers of cascaded MOS tubes and corresponding bits of control code to control the accuracy of adjusting the compensation current. In addition, it can be understood that Fig. 9 and Fig.10 In the temperature compensation circuit examples shown, the on and off of the electronic device is controlled by a first control signal in the form of a multi-bit digital signal, thereby controlling the magnitude of the analog current. However, this circuit is only an example and not a limitation. Any circuit that can achieve temperature compensation can be applied.

[0074] Next, an implementation of the intercept compensation circuit will be described. Fig.11 FIG. 1 is a schematic diagram of an implementation of an intercept compensation circuit. In this solution, the intercept compensation circuit includes a first current source circuit 1101 and a second current regulation circuit 1102, wherein the first current source circuit 1101 is based on a control voltage V CTRL , the control voltage V CTRL Converted into the corresponding third current I O3 The second current regulating circuit 1102 adjusts the control voltage V based on the second control signal (eg, control code). CTRL Size. Fig.11 In the embodiment shown, the second current regulating circuit 1102 is a digital-to-analog converter DAC, wherein the digital-to-analog converter DAC receives the second control signal (control code), performs digital-to-analog conversion according to the second control signal, and outputs a control voltage V corresponding to the second control signal. CTRL The current source circuit 1101 receives the control voltage, converts the control voltage into a current, and outputs a third current I corresponding to the control voltage. O3 .

[0075] The current source circuit 1101 may include an operational amplifier 1103 and an output transistor Q3. After the control module inputs the second control signal in the form of a digital signal into the DAC, the DAC converts the second control signal consisting of a multi-bit digital signal into a control voltage V with a zero temperature coefficient. CTRL , output to the non-inverting input terminal of the operational amplifier 1103. The output transistor Q3 also includes a control terminal, a first terminal, and a second terminal, wherein the control terminal of the output transistor Q3 receives the voltage output by the operational amplifier 1103, the first terminal is grounded via the grounding resistor R3, and the inverting input terminal of the operational amplifier is connected to the first terminal of the output transistor, so as to utilize the clamping function of the amplifier to clamp the control voltage V CTRL At the same time, it is applied to the top of the resistor R3, so the third current I output from the second end of the output transistor can be obtained by the following formula: O3 :

[0076] In addition, the NPN type BJT in the circuit can also be replaced by NMOS. The circuit structure is simple, and because the second control signal changes with the input frequency, dynamic adjustment of the intercept compensation current at different frequencies is achieved. In other embodiments, the current source circuit 1101 can also include an output transistor Q3 instead of the operational amplifier 1103, and the control voltage V CTRL The first end is directly output to the control end of the output transistor Q3, the first end is grounded via the grounding resistor R3, and the second end outputs the third current I O3 Among them, the third current Io 3 It has a zero temperature coefficient.

[0077] Fig.12 is another embodiment of the intercept compensation circuit. In this embodiment, the intercept compensation circuit includes a second current source circuit 1201 and a third current regulation circuit, wherein the third current regulation circuit includes a second current mirror structure 1202 and a plurality of third transistors 1203. The current source circuit 1201 receives a second voltage V B2 , the second voltage V B2 Converted into current, outputting the second voltage V B2 The corresponding fifth current Io 5 The current source circuit 1201 includes an operational amplifier 1204 and an output transistor Q3. The non-inverting input terminal of the operational amplifier 1204 receives a second voltage V B2 The inverting input terminal is connected to the first terminal of the output transistor Q3, the first terminal of the output transistor Q3 is grounded via the grounding resistor R4, and the fifth current Io is output at the second terminal 5 The second current mirror structure 1202 includes a second input transistor N1 and a second output transistor N2. The second input unit N1 of the second current mirror structure 1202 receives the fifth current I0. 5 The second output transistor N2 is used for the fifth current Io 5 Mirror copy is performed to output the third current Io 3 The plurality of third transistors 1203 are used to adjust the third current Io. 3 The third current Io 3 It has a zero temperature coefficient.

[0078] exist Fig.12 In the example shown, the second input transistor of the second current mirror 1202 is a MOS transistor N1, which is connected to the second end of the output transistor Q3 and is used to receive the fifth current I0 output by the output transistor Q3. 5 ; and the second output transistor is a MOS tube N2, which is used to output a third current Io3 The plurality of third transistors 1203 are turned on or off based on the second control signal to adjust the equivalent size of the second output transistor, thereby adjusting the size of the third current. Fig.12 In the example shown, the plurality of third transistors are a plurality of MOS transistors N3~NN cascaded on the side of the second output transistor, wherein a single-pole double-throw switch is provided at the gate of each of the MOS transistors N3~NN, one side of the switch is used to connect to the gate of the MOS transistor N2, and the other side is used to connect to the power supply voltage VDD. The second control signal is used to control the conduction position of the single-pole double-throw switch. For example, in an exemplary control logic, when the digital signal bit (not shown) corresponding to the second control signal is at a high level, the single-pole double-throw switch of the MOS transistor corresponding to the bit is connected to the gate of N2, so that the MOS transistor is connected in parallel with N2, which is equivalent to increasing the width-to-length ratio of N2, thereby increasing the copy multiple of the fifth current, that is, increasing the output current; when the digital signal bit is at a low level, the single-pole double-throw switch of the MOS transistor of the corresponding bit is connected to the power supply voltage VDD, and the MOS transistor is turned off, which is equivalent to reducing the width-to-length ratio of N2, thereby reducing the copy multiple of the fifth current, that is, reducing the output current. Therefore, by controlling whether N3~NN is connected to the compensation circuit through the control code, the third current Io can be controlled. 3 size.

[0079] Fig.11 The circuit shown controls the intercept compensation current by directly converting the digital signal corresponding to the control code into an analog signal; Fig.12 The circuit shown controls the on and off of the electronic device through the control code, thereby controlling the magnitude of the generated analog current. The above circuit is only an example and not a limitation, and any current source circuit that can generate a zero temperature coefficient current according to a digital signal can be applied.

[0080] It will be appreciated by those skilled in the art that, although the above-mentioned embodiments include a variety of different implementations, these implementations are non-limiting implementations. The present application creatively introduces considerations of frequency in the compensation circuit, and uses a frequency detector and a control module 603 to measure and consider the frequency in real time, so as to generate an appropriate compensation current, so that when a radio frequency signal with a different frequency is input, the logarithmic amplifier can still output a stable current. Therefore, the implementation methods of each circuit and module are not limited to those described in the specification, and the current direction of the compensation current is not the key point of the present application, and the current direction can be changed by, for example, adding a simple current mirror.

[0081] The above specific embodiments illustrate the implementation of the present application, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to the implementation. In addition, in order to avoid confusion or blurring the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0082] Furthermore, various operations will be described as multiple discrete operations in a manner that is most helpful for understanding the illustrative embodiments; however, the order of description should not be construed as implying that these operations are necessarily order dependent. In particular, these operations do not need to be performed in the order presented.

[0083] Unless the context dictates otherwise, the terms "comprising," "having," and "including" are synonymous. The phrase "A / B" means "A or B." The phrase "A and / or B" means "(A and B) or (A or B)."

[0084] As used herein, the term "module" or "unit" may refer to, be or include: an application specific integrated circuit (ASIC), an electronic circuit, a (shared, dedicated or group) processor and / or memory that executes one or more software or firmware programs, a combinational logic circuit and / or other suitable components that provide the described functionality.

[0085] In the accompanying drawings, some structural or method features are shown in a specific arrangement and / or order. However, it should be understood that such a specific arrangement and / or order may not be required. In some embodiments, these features may be arranged in a manner and / or order different from that shown in the illustrative drawings. In addition, the inclusion of structural or method features in a specific figure does not mean that such features are required in all embodiments, and in some embodiments, these features may not be included or may be combined with other features.

[0086] It should be understood that although the terms "first", "second", etc. may be used here to describe various units or data, these units or data should not be limited by these terms. These terms are used only to distinguish one feature from another. For example, without departing from the scope of the exemplary embodiment, a first feature may be referred to as a second feature, and similarly, a second feature may be referred to as a first feature.

[0087] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0088] While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims

1. A logarithmic detector based on dynamic compensation of input frequency, characterized in that: include: A logarithmic amplifier, used for receiving a radio frequency signal, wherein an output terminal of the logarithmic amplifier outputs a first current; a frequency discriminator, configured to determine and output first frequency information according to the radio frequency signal, wherein the first frequency information indicates a first frequency of the radio frequency signal; a control module, receiving the first frequency information, and generating a first control signal and / or a second control signal based on the first frequency information; wherein the first control signal is used to control the temperature coefficient of the second current at different first frequencies, and the second current is used to compensate for the first current at different temperatures; and the second control signal is used to control the magnitude of the third current, and the third current is used to compensate for the first current at different first frequencies; a temperature compensation circuit, configured to generate the second current that varies with temperature; the temperature compensation circuit further receiving the first control signal and changing the temperature coefficient of the second current based on the first control signal; and / or, The intercept compensation circuit receives the second control signal and outputs the corresponding third current based on the second control signal.

2. The logarithmic detector according to claim 1, characterized in that The first frequency information includes the first frequency; or the first frequency information includes a parameter used to calculate the first frequency.

3. The logarithmic detector according to claim 1, characterized in that The frequency discriminator comprises: A reference frequency source, used for outputting a reference signal, wherein the frequency of the reference signal is the reference frequency; A first counter, used to count pulses of the radio frequency signal to obtain a first count; The second counter is used to count the pulses of the reference signal to obtain a second count.

4. The logarithmic detector according to claim 3, characterized in that The frequency discriminator also includes: The calculation unit calculates the first frequency based on a ratio of the first count to the second count and the reference frequency.

5. The logarithmic detector according to claim 3, characterized in that The frequency discriminator further includes a clear input terminal for clearing the first counter and the second counter based on a clear signal.

6. The logarithmic detector according to claim 1, characterized in that The frequency discriminator comprises: An analog-to-digital converter, collecting the radio frequency signal into a digital signal; A calculation unit performs Fourier transform on the digital signal to calculate the first frequency.

7. The logarithmic detector according to claim 1, characterized in that The control module includes a lookup table, the lookup table stores a frequency correspondence relationship, and the control module determines the first control signal and the second control signal based on the first frequency and the frequency correspondence relationship; The frequency correspondence relationship indicates: the first control signal and the second control signal at different first frequencies.

8. The logarithmic detector according to claim 7, characterized in that The control module is also configured to perform the following operations: Obtaining the first frequency information to obtain the first frequency; According to the first frequency, searching the first control signal and the second control signal in the lookup table; The first control signal and the second control signal are transmitted to the temperature compensation circuit and the intercept compensation circuit respectively.

9. The logarithmic detector according to claim 8, characterized in that The frequency at which the control module obtains the first frequency information is a second frequency.

10. The logarithmic detector according to claim 9, characterized in that The frequency at which the control module sends a clearing signal to the frequency discriminator is the second frequency.

11. The logarithmic detector according to claim 1, characterized in that The temperature compensation circuit comprises: A first transistor having a temperature coefficient, the first transistor comprising: a control terminal, a first terminal, and a second terminal, the control terminal receiving a first voltage, the second terminal being used to output the second current; The first current regulating circuit is connected to the first end of the first transistor, and the first current regulating circuit receives the first control signal to adjust the resistance value connected to the first end of the first transistor.

12. The logarithmic detector according to claim 11, characterized in that The first current regulating circuit includes: a plurality of first resistors and a plurality of first switches, and the magnitude of the second current is adjusted by adjusting the resistance value of the branch where the second end of the first transistor is connected, wherein: After a plurality of the first resistors are connected in series, they are connected in series between the first end of the first transistor and the ground, and the first switch short-circuits one or more of the first resistors based on the first control signal; or, After being connected in parallel, the plurality of first resistors are connected in series between the first end of the first transistor and the ground. The first switch disconnects one or more of the first resistors based on the first control signal.

13. The logarithmic detector according to claim 1, characterized in that The temperature compensation circuit comprises: A first transistor having a temperature coefficient, the first transistor comprising: a control terminal, a first terminal, and a second terminal, the control terminal receiving a first voltage, the first terminal being grounded via a grounding resistor; The first current regulating circuit is connected to the second end of the first transistor, and the first current regulating circuit receives the first control signal and outputs the second current.

14. The logarithmic detector according to claim 13, characterized in that The first current regulating circuit comprises: A first current mirror structure, comprising a first input transistor and a first output transistor, wherein the first input transistor is connected to a first end or a second end of the first transistor; the first output transistor is used to mirror a fourth current to output the second current; wherein the fourth current is a current at the second end of the first transistor; A plurality of second transistors are provided, wherein the second transistors are turned on or off based on the first control signal to adjust the equivalent size of the first output transistor and output the second current.

15. The logarithmic detector according to claim 1, characterized in that The intercept compensation circuit comprises: A first current source circuit, based on a control voltage, converts the control voltage into the corresponding third current and outputs the third current; The second current regulating circuit adjusts the magnitude of the control voltage based on the second control signal.

16. The logarithmic detector according to claim 15, characterized in that The second current regulating circuit includes a digital-to-analog converter, which receives the second control signal, performs digital-to-analog conversion according to the second control signal, and outputs the control voltage corresponding to the second control signal.

17. The logarithmic detector according to claim 1, characterized in that The intercept compensation circuit comprises: a second current source circuit, receiving a second voltage, converting the second voltage into a current, and outputting a fifth current corresponding to the second voltage; The third current regulating circuit regulates the fifth current and outputs the third current; the third current regulating circuit regulates the magnitude of the third current based on the second control signal.

18. The logarithmic detector according to claim 17, characterized in that The third current regulating circuit comprises: A second current mirror structure comprises a second input transistor and a second output transistor, wherein the second input transistor of the second current mirror structure receives the fifth current; and the second output transistor is used for mirroring the fifth current to output the third current; A plurality of third transistors are turned on or off based on the second control signal to adjust the equivalent size of the second output transistor, thereby adjusting the size of the third current.

19. The logarithmic detector according to claim 1, characterized in that The input end of the frequency discriminator is connected to the radio frequency output end of the logarithmic amplifier, and the frequency discriminator determines the frequency based on the radio frequency signal amplified by the logarithmic amplifier.

20. The logarithmic detector according to claim 19, characterized in that It also includes a gain amplifier connected between the frequency discriminator and the logarithmic amplifier.

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