A difference frequency multiplication integral linear transformation network detection method

Abstract

The present invention provides a difference frequency multiplication integral linear transformation network detection method, which belongs to the field of detection technology. The method comprises the following steps: setting a first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 (τ), receiving the amplitude modulated signal u i (τ), the received amplitude modulated signal u i (τ) are respectively related to the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 (τ) performs product operation, and then performs integration operation respectively. At the same time, the first preset difference frequency signal u s1 (τ) is phase shifted and then combined with the amplitude modulated signal u i (τ) is multiplied, and then the product result is integrated to obtain the phase shift result I n1 , take the first operation result u n1 and the second operation result u n2 Frequency restoration is performed to obtain the frequency of the AM signal, and linear transformation is performed to obtain the original modulated signal. There is no need to accurately restore the carrier signal with the same frequency and phase. The phase of the AM signal has no effect on the detection result. The difference frequency signal can be flexibly selected according to the actual detection application, and high-quality detection results can be achieved by meeting simple selection criteria.

Description

Technical Field

[0001] The present invention relates to the field of detection technology, in particular to a difference frequency multiplication integral linear transformation network detection method. Background Art

[0002] In wired or radio communications and broadcasting applications, amplitude modulated signals are often used for information transmission. An amplitude modulated signal is a signal in which the amplitude of the carrier wave changes according to the changing pattern of the desired signal, but the frequency remains unchanged. The expressions for the carrier wave, modulating signal, and amplitude modulated signal of a common amplitude modulated signal are:

[0003] Carrier signal: u c (t) = U cm cosω c t, where U cm is the carrier amplitude, ω c is the carrier angular frequency;

[0004] Modulation signal: u Ω (t) = U Ωm cosω Ω t, where U Ωm is the carrier amplitude, ω Ω is the carrier angular frequency;

[0005] AM signal:

[0006] where k a is the amplitude modulation sensitivity, is the amplitude modulation coefficient, which indicates the degree to which the carrier amplitude is controlled by the modulation signal. The waveform of the amplitude modulation process signal is as follows: Figure 4 shown.

[0007] Detection is the process of extracting the modulating signal from an AM signal in order to recover the modulated signal. It is widely used in small-signal circuits in devices such as semiconductor radios, tape recorders, televisions, and communications. Two detection methods are available: the diode envelope detector and the synchronous detector. The diode envelope detector, due to the presence of a filter network, is prone to inertia distortion and negative peak clipping. In practical applications, carefully selected filter networks are essential to minimize distortion.

[0008] The synchronous detector uses a synchronous signal with the same frequency and phase as the amplitude modulated signal to multiply it and then pass it through a low-pass filter to restore the modulated signal. Its working model is as follows: Figure 5As shown in the figure, a synchronous detector must strictly restore the synchronous signal of the same frequency and phase. In practical applications, two methods are commonly used to restore this signal. One method is to limit and amplify the AM signal to a constant amplitude before filtering it to convert it into a synchronous sinusoidal signal. This method requires a filtering network, making it difficult for the restored synchronous signal to achieve phase consistency, resulting in loss of detection amplitude. The other method is to transmit a carrier signal during the AM signal transmission process and intercept the carrier signal as the synchronization signal based on the synchronization header signal. This method results in low operating efficiency at the transmitter and high energy loss. Summary of the Invention

[0009] The purpose of the present invention is to provide a difference frequency multiplication integral linear transformation network detection method to solve the technical problems of amplitude loss in existing detection methods or the need to transmit a carrier signal, which leads to low working efficiency of the transmitting end.

[0010] The amplitude modulated signal is sent to the multiplication and integration network, and is multiplied and integrated with the three difference frequency signals respectively. s1 (t),u s2 The multiplication integral of (t) can restore the frequency parameter of the amplitude modulated signal, which is consistent with u s1 (t) The multiplication and integration result of the signal with a phase shift of 270° is the same as u s1 The multiplication and integration results of (t) and the restored frequency parameters are passed through a linear transformation network to restore the modulated signal.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A difference frequency multiplication integral linear transformation network detection method, the method comprising the following steps:

[0013] Step 1: Set the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 (τ), receiving the amplitude modulated signal u i (τ);

[0014] Step 2: Convert the received AM signal u i (τ) are respectively related to the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s1 (τ) performs product operation, and then integrates the product results to obtain the first operation result u n1 and the second operation result u n2 , while the first preset difference frequency signal u s1 (τ) is phase shifted and then combined with the amplitude modulated signal ui (τ) is multiplied, and then the product result is integrated to obtain the phase shift result I n1 ;

[0015] Step 3: Take the first operation result u n1 and the second operation result u n2 Perform frequency restoration processing to obtain the frequency of the AM signal;

[0016] Step 4: Convert the phase shift result I n1 , the first operation result u n1 The original modulation signal is obtained by linearly transforming the frequency of the restored amplitude modulation signal.

[0017] Furthermore, in step 1, it is assumed that the received AM signal is Among them U am =U cm (1+m a cosω Ω t), the first preset difference frequency signal is u s1 (τ)=sin2πf1t=sin2πn1τ, the second preset difference frequency signal u s2 (τ)=sin2πf2t=sin2πn2τ,f f is the frequency of the received AM signal, f1 is the frequency of the first preset difference frequency signal, f2 is the frequency of the second preset difference frequency signal, and the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 The frequencies f1 and f2 of (τ) have a greatest common divisor f0, then f1=n1f0, -=n2f0, n1 and n2 are positive integers, then f f =xf0, x is a positive real number, indicating that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2, τ=f0t, t is time, is the phase difference.

[0018] Furthermore, in step 2, when performing the multiplication-integration transformation, the integration time is set to the period corresponding to f0 That is, the integral time of τ is τ0=f0t0=1, and the first operation result u n1 The operation process is:

[0019]

[0020] The second operation result u n2 The operation process is:

[0021]

[0022] Wherein, x is a positive real number, indicating that the frequency of the AM signal is a multiple of the greatest common divisor of the sum of the frequencies.

[0023] Furthermore, in step 2, the first preset difference frequency signal u s1 (τ)Shift phase.

[0024] Furthermore, in step 2, the first preset difference frequency signal u s1 (τ) Phase shift waveform obtained after phase shifting 270° For the convenience of analysis, the amplitude modulation signal transformation is expressed as:

[0025]

[0026] in The transformed amplitude modulated signal and u s1 (τ),u c1 The multiplication and integration of (τ) is:

[0027]

[0028]

[0029] Q n1 Indicates the amplitude modulated signal after conversion and u s1 The multiplication result of (τ), I n1 Indicates that the converted amplitude modulated signal and u c1 The multiplication product of (τ).

[0030] Furthermore, in step 3, the specific process of frequency restoration is that the FM signal is transformed into a quantity related to the FM signal frequency and the difference frequency signal frequency through the multiplication and integration network. In the linear transformation restoration network, the multiplication and integration transformation result u is first converted into n1 and u n2 By dividing, we can get the relationship between x and n1 and n2.

[0031]

[0032] Then x is equal to: Since f f =xf0, which means that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2. Then we can calculate f f .

[0033] Furthermore, in step 4, the amplitude modulated signal is combined with u s1 The multiplication product formula of (τ) and the converted amplitude modulation signal and u c1 The multiplication product of (τ) is obtained by the simultaneous equations:

[0034]

[0035] Where a=2π(x 2 -n1 2 ), b=cos2πx-1,c=sin2πx, and the solution is:

[0036]

[0037]

[0038] but

[0039]

[0040] because

[0041]

[0042] The final original modulated signal is:

[0043]

[0044] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0045] The present invention does not need to accurately restore the carrier signal with the same frequency and phase. The phase of the amplitude modulated signal has no effect on the detection result. The difference frequency signal can be flexibly selected according to the actual detection application scenario, and high-quality detection effect can be obtained by meeting simple selection conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the principle of the method of the present invention;

[0047] Figure 2 This is a comparison diagram of two detection methods in zero phase difference between the method of the present invention and synchronous detection;

[0048] Figure 3 This is a comparison diagram of two detection methods in the π / 4 phase difference between the method of the present invention and synchronous detection;

[0049] Figure 4 This is a comparison diagram of two detection methods in the π / 2 phase difference between the method of the present invention and synchronous detection;

[0050] Figure 5 This is the signal waveform diagram of the traditional amplitude modulation process of the present invention;

[0051] Figure 6 This is a principle block diagram of the traditional synchronous detection of the present invention. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and by way of preferred embodiments. However, it should be noted that many of the details listed in this specification are merely provided to help the reader gain a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be practiced even without these specific details.

[0053] like Figure 1 As shown, a difference frequency multiplication integral linear transformation network detection method comprises the following steps:

[0054] Step 1: Set the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 (τ), receiving the amplitude modulated signal u i (τ). Assume that the received AM signal is Among them U am =U cm (1+m a cosω Ω t), the first preset difference frequency signal is u s1 ((τ)=sin2πf1t=sin2πn1τ, the second preset difference frequency signal u s2 (τ)=sin2πf2t=sin2πn2τ,f f is the frequency of the received AM signal, f1 is the frequency of the first preset difference frequency signal, f2 is the frequency of the second preset difference frequency signal, and the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 The frequencies f1 and f2 of (τ) have a greatest common divisor f0, then f1=n1f0, f2=n2f0, n1 and n2 are positive integers, then f f =xf0, x is a positive real number, indicating that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2, τ=f0t, t is time, is the phase difference.

[0055] Step 2: Convert the received AM signal u i (τ) are respectively related to the first preset difference frequency signal u s1 (τ) and the second preset difference frequency signal u s2 (τ) performs product operation, and then integrates the product results to obtain the first operation result u n1 and the second operation result u n2 , while the first preset difference frequency signal u s1 (τ) is phase shifted, and then multiplied with the amplitude modulated signal ui(τ), and then the product result is integrated to obtain the phase shift result I n1 .

[0056] When performing multiplication-integration transformation, the integration time is set to the period corresponding to f0 That is, the integral time of τ is τ0=f0t0=1, and the first operation result u n1 The operation process is:

[0057]

[0058] and the difference frequency signal u s1 The specific calculation process of (τ) multiplication integral is:

[0059]

[0060] The second operation result u n2 The operation process is:

[0061]

[0062]

[0063] Wherein, x is a positive real number, indicating that the frequency of the AM signal is a multiple of the greatest common divisor of the sum of the frequencies.

[0064] and the difference frequency signal u s2 The calculation process of (τ) multiplication integral is:

[0065]

[0066] The first preset difference frequency signal u s1 (τ)Shift or In this embodiment, 270° is taken as an example, and the first preset difference frequency signal u s1 (τ) Phase shift waveform obtained after phase shifting 270° For the convenience of analysis, the amplitude modulation signal transformation is expressed as:

[0067]

[0068] in The transformed amplitude modulated signal and u s1 (τ),u c1 The multiplication and integration of (τ) is:

[0069]

[0070]

[0071] Q n1 Indicates the amplitude modulated signal after conversion and u s1 The multiplication result of (τ), I n1 Indicates that the converted amplitude modulated signal and u c1 The multiplication product of (τ).

[0072] Step 3: Take the first operation result u n1 and the second operation result u n2Perform frequency restoration to obtain the frequency of the AM signal. The specific process of frequency restoration is that the FM signal is transformed into a quantity related to the FM signal frequency and the difference frequency signal frequency through the multiplication and integration network. In the linear transformation restoration network, the multiplication and integration transformation result u is first converted to n1 and u n2 By dividing, we can get the relationship between x and n1 and n2.

[0073]

[0074] Then x is equal to: Since f f =xf0, which means that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2. Then we can calculate f f .

[0075] With AM signal and u s1 (τ),u c1 The multiplication integral calculation process of (τ) is as follows:

[0076]

[0077]

[0078]

[0079] Step 4: Convert the phase shift result I n1、 The first operation result u n1 The original modulation signal is obtained by linearly transforming the frequency of the restored amplitude modulation signal. s1 The multiplication product formula of (τ) and the converted amplitude modulation signal and u c1 The multiplication product of (τ) is obtained by the simultaneous equations:

[0080]

[0081] Where a=2π(x 2 -n1 2 ), b=cos2πx-1,c=sin2πx, and the solution is:

[0082]

[0083]

[0084] but

[0085]

[0086] because

[0087]

[0088] The final original modulated signal is:

[0089]

[0090] When the recovered carrier signal is in phase with the AM signal, that is, the phase difference is 0, the simulation results are Figure 2 As shown, it can be seen that the detection quality of synchronous detection and difference frequency multiplication and integration frequency restoration linear transformation network is comparable, and the restored modulated signal has no distortion and amplitude loss.

[0091] When the phase difference between the recovered carrier signal and the AM signal is π / 4, the experimental comparison results are as follows: Figure 3 As shown in the figure, the amplitude of the modulation signal restored by synchronous detection is obviously attenuated, while the modulation signal restored by the difference frequency multiplication integral frequency restoration linear transformation network detection method is highly consistent with the original modulation signal waveform.

[0092] When the phase difference between the recovered carrier signal and the AM signal is π / 2, the experimental comparison results are as follows: Figure 4 As shown, the synchronous detection multiplication result with the AM signal is a high-frequency component, which is completely filtered out by the low-pass filter and cannot be restored to the original modulated signal. However, the modulation signal restored by the difference frequency multiplication, integral frequency restoration, and linear transformation network detection method still matches the original modulation signal waveform. This shows that the difference frequency multiplication, integral frequency restoration, and linear transformation network detection method has extremely high detection quality.

[0093] This method is used at a signal receiving end to process a modulated signal, such as when demodulating a signal received by a wireless receiving device. It can also be used for signal demodulation at a wired receiving end.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A difference frequency multiplication integral linear transformation network detection method, characterized in that: The method comprises the following steps: Step 1: Set the first preset difference frequency signal and the second preset difference frequency signal Receiving AM signals Step 2: Convert the received AM signal respectively with the first preset difference frequency signal and the second preset difference frequency signal Perform the product operation, and then perform the integration operation on the product results to obtain the first operation result u n1 and the second operation result u n2 , while the first preset difference frequency signal Phase shifted and then combined with the AM signal Perform product operation, then integrate the product result to obtain the phase shift operation result I n1 ; Step 3: Take the first operation result u n1 and the second operation result u n2 Perform frequency restoration processing to obtain the frequency of the AM signal; Step 4: Convert the phase shift result I n1 , the first operation result u n1 Perform linear transformation on the frequency of the restored AM signal to obtain the original modulation signal; In step 1, assume that the received AM signal is Among them U am =U cm (1+m a cosω Ω t), the first preset difference frequency signal is The second preset difference frequency signal f f is the frequency of the received AM signal, f1 is the frequency of the first preset difference frequency signal, f2 is the frequency of the second preset difference frequency signal, and the first preset difference frequency signal and the second preset difference frequency signal The frequencies f1 and f2 have a greatest common divisor f0, then f1=n1f0, f2=n2f0, n1, n2 are positive integers, then f f =xf0, x is a positive real number, indicating that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2. t is time, is the phase difference, U cm is the carrier amplitude, ω Ω is the carrier angular frequency, is the amplitude modulation coefficient.

2. The difference frequency multiplication integral linear transformation network detection method according to claim 1, characterized in that: In step 2, when performing the multiplication-integration transformation, the integration time is set to the period corresponding to f0 Right now The integration time is The first operation result u n1 The operation process is: The second operation result u n2 The operation process is: Where x is a positive real number.

3. The difference frequency multiplication-integral linear transformation network detection method according to claim 1, characterized in that: In step 2, the first preset difference frequency signal shift phase.

4. The difference frequency multiplication-integral linear transformation network detection method according to claim 1, characterized in that: In step 2, the first preset difference frequency signal Phase shift waveform obtained after phase shifting 270° For the convenience of analysis, the amplitude modulation signal transformation is expressed as: in The converted amplitude modulated signal is The multiplication integral result is: Q n1 The transformed amplitude modulated signal is The multiplication integral result, I n1 The transformed amplitude modulated signal is The multiplication integral result of .

5. The difference frequency multiplication-integral linear transformation network detection method according to claim 4, characterized in that: In step 3, the specific process of frequency restoration is that the FM signal is transformed into a quantity related to the FM signal frequency and the difference frequency signal frequency through the multiplication and integration network. In the linear transformation restoration network, the multiplication and integration transformation result u is first converted into n1 and u n2 By dividing, we can get the relationship between x and n1 and n2. Then x is equal to: Since f f =xf0, which means that the frequency of the AM signal is a multiple of the greatest common divisor f0 with the frequencies f1 and f2. Then we can calculate f f .

6. The difference frequency multiplication integral linear transformation network detection method according to claim 5, characterized in that: In step 4, the transformed AM signal is compared with The multiplication and integration result formula and the transformed amplitude modulation signal and The multiplication and integration results of the simultaneous equations are: Where a=2π(x 2 -n1 2 ), b=cos2πx-1,c=sin2πx, and the solution is: but because The final original modulated signal is:

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