Oscillator frequency adjustment lookup table establishment method and related transceiver
By establishing an oscillator frequency adjustment lookup table in the transceiver, and utilizing adjustable capacitor banks and interpolation operations, the frequency adjustment process is simplified, the high cost problem is solved, and high-precision frequency adjustment is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- REALTEK SEMICON CORP
- Filing Date
- 2021-11-04
- Publication Date
- 2026-06-26
AI Technical Summary
In existing mobile communications technologies, the production cost of transceivers is too high in order to meet the high-precision frequency requirements. How to achieve accurate frequency adjustment while reducing costs is an urgent problem to be solved.
By establishing an oscillator frequency adjustment lookup table in the transceiver, and using adjustable capacitor banks and interpolation operations, the relationship between the equivalent capacitance value and the frequency change is recorded. A univariate quadratic polynomial is used to approximate the curve, reducing the number of measurements and simplifying the lookup table establishment process.
This reduces the cost of chip production while meeting the requirements for high-precision frequency adjustment, thus improving the accuracy and efficiency of frequency adjustment.
Smart Images
Figure CN116073764B_ABST
Abstract
Description
Technical Field
[0001] This application relates to oscillator frequency control, specifically to a method for establishing an oscillator frequency adjustment lookup table and a related transceiver. Background Technology
[0002] Mobile communication standards impose stringent requirements on frequency error, such as a tolerance range of only 0.1 ppm. In other words, to comply with these standards, the transceiver's crystal oscillator circuitry must be able to precisely generate the required resonant frequency. However, meeting these standards often significantly increases costs for system manufacturers. Therefore, achieving similar performance at a lower cost has become a pressing issue in this field. Summary of the Invention
[0003] This application provides a method for establishing an oscillator frequency adjustment lookup table in a transceiver, wherein the transceiver generates a clock based on a crystal oscillator external to the transceiver for transmission and reception, the transceiver including an adjustable capacitor bank coupled to the crystal oscillator, wherein when the equivalent capacitance value of the adjustable capacitor bank is a reference value, the crystal oscillator has a reference frequency, and when the equivalent capacitance value changes relative to the reference value, the crystal oscillator correspondingly generates a frequency change relative to the reference frequency, the method comprising: obtaining the frequency change corresponding to a first value, a second value, and a third value of the equivalent capacitance value. The equivalent capacitance value is used to perform interpolation on the first value, the second value, and the third value and the corresponding frequency change to obtain the frequency change corresponding to the first sub-value of the equivalent capacitance value between the first value and the second value, and the frequency change corresponding to the second sub-value of the equivalent capacitance value between the second value and the third value; and the first value, the first sub-value, the second value, the second sub-value, and the third value of the equivalent capacitance value and the corresponding frequency change are stored in the oscillator frequency adjustment lookup table in the storage unit of the transceiver.
[0004] This application provides a transceiver for transmitting and receiving data based on a clock generated by a crystal oscillator outside the transceiver. The transceiver includes: an adjustable capacitor bank coupled to the crystal oscillator, wherein when the equivalent capacitance value of the adjustable capacitor bank is a reference value, the crystal oscillator has a reference frequency, and when the equivalent capacitance value changes relative to the reference value, the crystal oscillator correspondingly generates a frequency change relative to the reference frequency; an arithmetic unit for performing interpolation operations based on a first value, a second value, and a third value of the equivalent capacitance value and their corresponding frequency changes to obtain the frequency change corresponding to a first sub-value of the equivalent capacitance value between the first value and the second value, and to obtain the frequency change corresponding to a second sub-value of the equivalent capacitance value between the second value and the third value; and a storage unit for storing an oscillator frequency adjustment lookup table, the oscillator frequency adjustment lookup table including the first value, the first sub-value, the second value, the second sub-value, and the third value of the equivalent capacitance value and their corresponding frequency changes.
[0005] The oscillator frequency adjustment lookup table establishment method and related transceiver of this application can reduce the cost of chip manufacturing. Attached Figure Description
[0006] Various implementations of this disclosure can be best understood by reading the following embodiments and accompanying drawings. It should be noted that, in accordance with art standards, the various features in the figures are not drawn to scale. In fact, the dimensions of certain features may be intentionally enlarged or reduced for clarity of description.
[0007] Figure 1 This is a schematic diagram of an embodiment of the transceiver of this application.
[0008] Figure 2 This is a graph showing the change in crystal oscillator frequency versus temperature.
[0009] Figure 3 This is a graph showing the equivalent capacitance of the adjustable capacitor bank versus the frequency.
[0010] Figure 4 To be Figure 3 A schematic diagram showing the decomposition of a curve into multiple curves. Detailed Implementation
[0011] Figure 1 This is a schematic diagram of an embodiment of the transceiver of this application. The transceiver 100 generates a clock based on the frequency generated by a crystal oscillator 200 outside the transceiver 100 for transmitting and receiving. The crystal oscillator 200 can be equivalent to a capacitor C0, an inductor L1, a resistor R, and a capacitor C1. The inductor L1, resistor R, and capacitor C1 are connected in series, and the capacitor C0 is connected in parallel.
[0012] Transceiver 100 includes an adjustable capacitor bank 102 coupled to crystal oscillator 200, wherein the adjustable capacitor bank 102 includes a first adjustable capacitor C. L1 Second adjustable capacitor C L2 The first adjustable capacitor C L1 One end is coupled to one end of the crystal oscillator 200, and the first adjustable capacitor C L1 The other end is coupled to ground; the second adjustable capacitor C L2 One end is coupled to the other end of the crystal oscillator 200, and the second adjustable capacitor C L2 The other end is coupled to ground. Therefore, the first adjustable capacitor C L1 Second adjustable capacitor C L2 The first adjustable capacitor C is connected in series with the ground terminal, and the two capacitors are equivalently connected in series. L1 Second adjustable capacitor C L2 It has an equivalent capacitance value C. By adjusting the equivalent capacitance value C, the resonant frequency of the crystal oscillator 200 can be changed.
[0013] Normally, at the factory, the equivalent capacitance value C is adjusted to reduce the error between the resonant frequency and the target frequency of the crystal oscillator 200 to within the allowable range specified. However, in actual use, temperature changes may cause this error to exceed the allowable range specified. Figure 2 As shown, the factory temperature was T. C The error (frequency change) between the resonant frequency and the target frequency of the crystal oscillator 200 is 0. According to the specification, the transceiver 100 must be able to operate normally within the temperature range T. L and T H The range between 100 and 100 indicates that the transceiver 100 must be able to handle at least the temperature range T. L and T H The most severe frequency change between them, i.e., Δf H and -Δf L .
[0014] Therefore, transceiver 100 needs to dynamically monitor the resonant frequency of crystal oscillator 200 and control the error of crystal oscillator 200 by adjusting adjustable capacitor bank 102 at any time. However, the equivalent capacitance value C and the resonant frequency of crystal oscillator 200 are not linearly related, so the correspondence between capacitance value C and resonant frequency of crystal oscillator 200 must be recorded in advance in the oscillator frequency adjustment lookup table (hereinafter referred to as the lookup table) of storage unit 106 of transceiver 100 in order to know how to adjust adjustable capacitor bank 102 to generate the desired frequency change in order to compensate for the above-mentioned error.
[0015] Please refer to Figure 3Before leaving the factory, a lookup table creation process is required. Generally speaking, the purpose of this process is to find the frequencies of the crystal oscillator 200 corresponding to multiple equivalent capacitance values C within a certain range and record them in the lookup table. For example, the intervals between the multiple equivalent capacitance values C can be fixed capacitance values. In one embodiment, the value of the equivalent capacitance C that makes the resonant frequency of the crystal oscillator 200 the target frequency at the time this process is executed can be used as the reference value C. RF And through measurement, a value different from the reference value C was obtained. RF The table retrieves multiple equivalent capacitance values C and their corresponding frequencies of the crystal oscillator 200, along with the difference between these frequencies and the target frequency (i.e., frequency variation). It then records these multiple equivalent capacitance values C and their corresponding frequency variations in a lookup table. The range of the aforementioned equivalent capacitance values C depends on the desired maximum allowable positive and negative frequency variation, for example... Figure 3 In the process, the frequency change Δf9 corresponding to the smallest equivalent capacitance value C (i.e., equivalent capacitance value C9) must be less than -Δf. L The frequency change Δf1 corresponding to the largest equivalent capacitance value C (i.e., equivalent capacitance value C1) must be greater than Δf. H .
[0016] However, Figure 3 This is for illustrative purposes only. To achieve precise adjustment of the crystal oscillator 200, the actual number of data points required for measurement is more than [a certain percentage]. Figure 3 The required density of the markers is very high to meet the accuracy requirements of the specification, which makes the process of building the lookup table extremely time-consuming and costly. Therefore, this process needs to be simplified, and the details are as follows.
[0017] Please return Figure 1 The relationship between the equivalent capacitance C and the oscillation frequency f of the crystal oscillator 200 is as follows: To simplify the calculation, this application proposes to use Taylor expansion to simplify the above relationship into a univariate polynomial of degree n related to the equivalent capacitance value C, where n is a positive integer, i.e., the oscillation frequency f(C) = a0 + a1(CC). α )+a2(CC α ) 2 +…+a n (CC α ) n C α Let a0 be the expansion point of the polynomial, a1 be the coefficient of the constant term, and a2 ~ a1 be the coefficient of the linear term. n And so on. Theoretically, the larger n is, the closer we can get to the approximation. Figure 3 The curve is obtained, but the complexity depends on the size of n. To achieve a balance between accuracy and cost, this embodiment will... Figure 3 The curve is divided into several small segments, such as Figure 4As shown, different quadratic polynomials are used as models for each segment.
[0018] In this embodiment, Figure 1 The transceiver 100 also includes an arithmetic unit 104. In the process of building the lookup table, the arithmetic unit 104 can use different quadratic polynomials as models for each segment, and then interpolate to obtain the frequency change corresponding to multiple points (multiple equivalent capacitance values C) within each segment. For example, the arithmetic unit 104 can adjust the equivalent capacitance value of the adjustable capacitor bank 102 to a first value C1, and then measure the frequency change Δf1; then adjust the equivalent capacitance value of the adjustable capacitor bank 102 to a second value C2, and then measure the frequency change Δf2; then adjust the equivalent capacitance value of the adjustable capacitor bank 102 to a third value C3, and then measure the frequency change Δf3. Figure 4 It can be seen that, compared to measuring every single point, Figure 4 The code skips four points between the first value C1 and the second value C2, and also skips four points between the second value C2 and the third value C3. However, this is just an illustration; in reality, the number of points skipped can be much higher.
[0019] Next, the arithmetic unit 104 uses the first value C1, the second value C2, and the third value C3, along with the corresponding frequency changes Δf1, Δf2, and Δf3, to derive a first univariate quadratic polynomial for the equivalent capacitance value C, which serves as a model of the curve between the first value C1 and the third value C3. In other words, this first univariate quadratic polynomial is used to approximate the relationship between the crystal oscillator 200 and the equivalent capacitance value C at the first value C1 and the third value C3. In this embodiment, the second value C2 is the average of the first value C1 and the third value C3 to reduce computational complexity and achieve better results. However, this application is not limited to this; in some embodiments, the first value C1, the second value C2, and the third value C3 may not be equidistant.
[0020] Therefore, without further measurement, the frequency change corresponding to any value of the equivalent capacitance C between the first value C1 and the third value C3 can be immediately obtained using the first univariate quadratic polynomial and recorded in the lookup table of the storage unit 106. Thus, most of the measurement time in the process of building the lookup table can be saved.
[0021] Similarly, the arithmetic unit 104 can adjust the equivalent capacitance value of the adjustable capacitor bank 102 to the fourth value C4 and then measure the frequency change Δf4; then, it can adjust the equivalent capacitance value of the adjustable capacitor bank 102 to the fifth value C5 and measure the frequency change Δf5. Next, the arithmetic unit 104 uses the third value C3, the fourth value C4, and the fifth value C5, along with the corresponding frequency changes Δf3 (previously measured), Δf4, and Δf5, to derive a second quadratic polynomial with respect to the equivalent capacitance value C as a model of the curve between the third value C3 and the fifth value C5. In other words, this second quadratic polynomial is used to approximate the relationship between the crystal oscillator 200 and the equivalent capacitance value C at the third value C3 and the fifth value C5. Therefore, without further measurement, the frequency change corresponding to any value of the equivalent capacitance C between the third value C3 and the fifth value C5 can be immediately obtained using this second quadratic polynomial and recorded in the lookup table of the storage unit 106. Thus, most of the measurement time in the process of building the lookup table can be saved.
[0022] Similarly, the operation unit 104 can obtain a third univariate quadratic polynomial as a model of the curve between the fifth value C5 and the seventh value C7; and obtain a fourth univariate quadratic polynomial as a model of the curve between the seventh value C7 and the ninth value C9, so as to cover the range of the required frequency variation.
[0023] The above embodiments are not limitations of this application. In some embodiments, more than four univariate quadratic polynomials can be used to form the polynomial. Figure 4 The curve between the frequency change Δf1 and the frequency change Δf9, theoretically, can improve accuracy by dividing the same range of curves into more different segments and using different univariate quadratic polynomials as models. However, in practice, as long as the accuracy is within the specification, there is room to reduce the time (i.e. cost) required to build the lookup table.
[0024] The foregoing description briefly outlines the features of certain embodiments of this application, enabling those skilled in the art to more fully understand the various implementations of this application. Those skilled in the art should understand that they can readily utilize this application as a basis to design or modify other processes and structures to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art should understand that these equivalent implementations still fall within the spirit and scope of this application, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this application.
[0025] [Symbol Explanation]
[0026] 100: Transceiver
[0027] 102: Adjustable capacitor bank
[0028] 104: Computational Unit
[0029] 106: Storage Unit
[0030] 200: Crystal Oscillator
Claims
1. A method for establishing an oscillator frequency adjustment lookup table in a transceiver or large-scale integrated circuit, wherein the transceiver or large-scale integrated circuit generates a clock for transmission and reception based on a crystal oscillator external to the transceiver, the transceiver including an adjustable capacitor bank coupled to the crystal oscillator, wherein the crystal oscillator has a reference frequency when the equivalent capacitance value of the adjustable capacitor bank is a reference value, and the crystal oscillator correspondingly generates a frequency change relative to the reference frequency when the equivalent capacitance value changes relative to the reference value, the method comprising: The frequency variation corresponding to the first, second, and third values of the equivalent capacitance is obtained; Interpolation is performed based on the equivalent capacitance value at the first value, the second value, and the third value and the corresponding frequency change to obtain the frequency change corresponding to the first sub-value of the equivalent capacitance value between the first value and the second value, and to obtain the frequency change corresponding to the second sub-value of the equivalent capacitance value between the second value and the third value. as well as The first value, the first sub-value, the second value, the second sub-value, and the third value of the equivalent capacitance, along with their corresponding frequency changes, are stored in the oscillator frequency adjustment lookup table in the storage unit of the transceiver.
2. The method according to claim 1, wherein the step of performing the interpolation operation based on the equivalent capacitance value at the first value, the second value, and the third value and the corresponding frequency variation includes: A first univariate quadratic polynomial about the equivalent capacitance value is obtained based on the changes in the first value, the second value, and the third value and their corresponding frequencies.
3. The method according to claim 2, wherein the first univariate quadratic polynomial is used to approximate the relationship between the crystal oscillator and the equivalent capacitance value at the first value and the third value.
4. The method according to claim 1, wherein the second value of the equivalent capacitance value is the average of the first value and the third value.
5. The method according to claim 2, further comprising: Interpolation is performed based on the equivalent capacitance value at the third, fourth, and fifth values and the corresponding frequency changes to obtain the frequency change corresponding to the third sub-value of the equivalent capacitance value between the third and fourth values, and the frequency change corresponding to the fourth sub-value of the equivalent capacitance value between the fourth and fifth values. as well as The third value, the third sub-value, the fourth value, the fourth sub-value, and the fifth value of the equivalent capacitance, along with their corresponding frequency changes, are stored in the oscillator frequency adjustment lookup table in the storage unit of the transceiver.
6. The method according to claim 5, wherein the step of performing the interpolation operation based on the equivalent capacitance value at the third value, the fourth value, and the fifth value and the corresponding frequency variation includes: A second univariate quadratic polynomial about the equivalent capacitance value is obtained based on the equivalent capacitance value at the third, fourth, and fifth values and the corresponding frequency changes.
7. The method according to claim 6, wherein the second univariate quadratic polynomial is different from the first univariate quadratic polynomial.
8. The method according to claim 6, wherein the second univariate quadratic polynomial is used to approximate the relationship between the crystal oscillator and the equivalent capacitance value in the third and fifth values.
9. The method according to claim 5, wherein the fourth value of the equivalent capacitance value is the average of the third value and the fifth value.
10. A transceiver for transmitting and receiving data based on a clock generated by a crystal oscillator outside the transceiver, the transceiver comprising: An adjustable capacitor bank is coupled to the crystal oscillator, wherein when the equivalent capacitance value of the adjustable capacitor bank is a reference value, the crystal oscillator has a reference frequency, and when the equivalent capacitance value changes relative to the reference value, the crystal oscillator correspondingly generates a frequency change relative to the reference frequency. The arithmetic unit is used to perform interpolation operations based on the first value, the second value, and the third value of the equivalent capacitance value and the corresponding frequency change, so as to obtain the frequency change corresponding to the first sub-value of the equivalent capacitance value between the first value and the second value, and to obtain the frequency change corresponding to the second sub-value of the equivalent capacitance value between the second value and the third value. as well as The storage unit is used to store an oscillator frequency adjustment lookup table, which includes the first value, the first sub-value, the second value, the second sub-value, and the third value of the equivalent capacitance value and the corresponding frequency change amount.