Method for judging semi-radio frequency signal
By observing the relationship between the attenuation value of the digitally controlled attenuator and the change in intermediate frequency signal power in the frequency conversion link, it is possible to determine whether the intermediate frequency signal is a false signal, thus solving the false signal problem caused by the semi-radio frequency signal and improving the anti-interference capability of the radar system.
Patent Information
- Application Number
- CN202511701474.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-19
- Publication Date
- 2026-02-24
AI Technical Summary
In existing multi-channel frequency conversion schemes, the problem of false intermediate frequency signals caused by half-RF signals has not been effectively suppressed. In particular, when the input signal power is close to the input P-1, the second harmonic generated by the second amplifier is large, which leads to the generation of false intermediate frequency signals.
By observing the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the intermediate frequency signal, it is possible to determine whether the intermediate frequency signal is a spurious signal. Specifically, this involves controlling the digitally controlled attenuator to generate different attenuation values and monitoring the power change of the intermediate frequency signal, and using the second harmonic suppression characteristics of specific amplifiers and filters for judgment.
Without increasing hardware costs, it achieves effective identification of false intermediate frequency signals, improves the anti-interference capability of the radar system, and reduces the design difficulty of the frequency conversion scheme.
Smart Images
Figure CN121559151A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave circuit technology, and specifically relates to a method for determining half-radio frequency signals. Background Technology
[0002] In a multi-channel frequency conversion scheme, the signal with a frequency half that of the target signal to be detected is called a half-RF signal. In order to prevent the half-RF signal from generating an intermediate frequency signal and causing false signals, a bandpass filter is often used to suppress the half-RF signal. Since the filter and the power divider network that distributes the signal to multiple channels have relatively large insertion losses, in order to ensure the noise figure of the frequency conversion scheme and compensate for this loss, an amplifier needs to be added before and after the filter and the power divider network, respectively called the first amplifier and the second amplifier.
[0003] This approach has the following problems: When the input signal power is much smaller than the input P-1, such as -40dBm, the second harmonic signals generated by the first and second amplifiers are relatively small, and the second harmonic suppression is relatively high. However, when the input signal power is close to the input P-1, the second harmonic generated by the second amplifier is relatively large. At this time, the bandpass filter covers the frequencies of multiple channels, so it has almost no suppression of the half-RF signals corresponding to the RF signals of some channels. As a result, the second amplifier will generate a relatively large second harmonic, which enters the mixer and eventually generates the intermediate frequency signal, causing spurious signals.
[0004] Previous literature has focused on the suppression of image frequency signals and half-IF signals in frequency conversion links, but the suppression of half-RF signals has been largely ignored. Summary of the Invention
[0005] The purpose of this invention is to provide a method for judging semi-radio frequency signals, solving the problem of false signals caused by semi-radio frequency signals. By observing the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the intermediate frequency signal, it is determined whether the intermediate frequency signal is a false signal. This method is simple to implement, can effectively judge whether the intermediate frequency signal is a false signal, and improves the anti-interference capability of radar.
[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:
[0007] A method for determining semi-RF signals is based on an RF link before the first frequency conversion. The RF link includes a first amplifier, a filter, a power divider, a digitally controlled attenuator, a second amplifier, and a mixer connected in sequence. The output signal of the mixer is an intermediate frequency (IF) signal. When the IF signal is detected, the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the IF signal is observed to determine whether the IF signal is generated by an RF signal or a semi-RF signal, and whether it is a false signal.
[0008] Furthermore, by observing the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the intermediate frequency signal, it can be determined whether the intermediate frequency signal is generated by a radio frequency (RF) signal or a semi-RF signal, and whether it is a spurious signal. Specifically, this includes:
[0009] The numerically controlled attenuator generates attenuation of adB and 2adB respectively;
[0010] Observe the digitally controlled attenuator. If, for the two set attenuations, the signal power decreases by x1dB and x2dB respectively, and x1 is greater than a and less than 2a, and x2 is greater than 2a and less than 4a, and x1 / a is less than x2 / 2a, then the intermediate frequency signal is generated by a semi-radio frequency signal and is a spurious signal. If x1 is less than a and x2 is less than 2a, then the intermediate frequency signal is generated by a radio frequency signal.
[0011] If the digitally controlled attenuator has no additional attenuation and the power of the intermediate frequency signal fluctuates up and down, with the power varying around the set value, and the digitally controlled attenuator is controlled to generate attenuation of adb and 2adB respectively, if the power fluctuation of the signal is observed to be decreasing, it is determined that the signal at this time is generated by both radio frequency signal and semi-radio frequency signal.
[0012] Furthermore, a is greater than or equal to 5.
[0013] Furthermore, x1 is less than a and x2 is less than 2a specifically: x1 = l1 * a, x2 = l2 * 2a, where l1 and l2 are coefficients less than 1.
[0014] Furthermore, both l1 and l2 are greater than 0.8 and less than 1.
[0015] Furthermore, when the input signal power reaches input P-1, the second harmonic suppression of the first amplifier and the second amplifier is greater than 45dBc.
[0016] Furthermore, the first amplifier is IPA-0030-27.
[0017] Furthermore, the second amplifier is ILA-0003C.
[0018] Furthermore, the filter suppresses half-RF signals by more than 45 dBc.
[0019] Compared with existing technologies, the advantages of this invention are: without increasing hardware costs, by changing the attenuation value of the numerically controlled attenuator, and observing the relationship between the attenuation value of the numerically controlled attenuator and the power change value of the intermediate frequency signal, it can be determined whether the intermediate frequency signal is a spurious signal. This method is simple to implement, can effectively determine whether the intermediate frequency signal is a spurious signal, does not require excessively high requirements for half-IF suppression, reduces the design difficulty of the frequency conversion scheme, and improves the anti-interference capability of the radar system. Attached Figure Description
[0020] Figure 1 This is a block diagram illustrating the principle of a frequency conversion scheme.
[0021] Figure descriptions: 1, First amplifier; 2, Filter; 3, Power divider; 4, Digitally controlled attenuator; 5, Second amplifier; 6, Mixer. Detailed Implementation
[0022] This invention provides a method to solve the problem of spurious signals caused by semi-radio frequency (RF) signals. In the frequency conversion link, before the first frequency conversion, the main components, in sequence, include a first amplifier, a filter, a power divider, a digitally controlled attenuator, a second amplifier, and a mixer. The specific solution is as follows:
[0023] Step 1: When the target signal (intermediate frequency signal output by the mixer) is detected, if it is impossible to determine whether the intermediate frequency signal is generated by the radio frequency signal or the semi-radio frequency signal, the digitally controlled attenuator can be controlled to generate attenuation values such as adB, 2adB, etc. (it is recommended that a be greater than or equal to 5), while monitoring the change value of the intermediate frequency signal power.
[0024] Step 2: Assuming that the power of the intermediate frequency signal drops by x1dB and x2dB respectively, x1 is greater than a and less than 2a, x2 is greater than 2a and less than 4a, and x1 / a is less than x2 / 2a, it can be determined that the intermediate frequency signal at this time is generated by the semi-radio frequency signal and is a false signal.
[0025] Step 3: If x1 is close to and less than a, and x2 is close to and less than 2a, that is, when the power drop of the intermediate frequency signal is basically the same as the attenuation value of the digitally controlled attenuator, it can be determined that the intermediate frequency signal is generated by the radio frequency signal.
[0026] Step 4: If the digitally controlled attenuator has no additional attenuation and the intermediate frequency signal power has obvious up-and-down jitter, with the power fluctuating greatly, the digitally controlled attenuator can be controlled to produce attenuation values such as adb and 2adB. If the power jitter of the intermediate frequency signal is observed to gradually decrease, it can be determined that the intermediate frequency signal is generated by both radio frequency (RF) and semi-RF signals.
[0027] In the frequency conversion link, a first amplifier with high second harmonic suppression, low gain, and high output P-1 should be used, with IPA-0030-27 being the preferred model.
[0028] In frequency conversion links, filters with high suppression of half-radio signals should be used, preferably filters with half-radio signal suppression greater than 45dBc.
[0029] In the frequency conversion link, a second amplifier with high second harmonic suppression should be used. At the same time, the second harmonic suppression characteristics of the second amplifier should be tested in advance. The ratio of x1 / a and x2 / 2a should be compared with the second harmonic suppression characteristics of the second amplifier to observe whether the trend is basically fitted. If so, it can be determined that the intermediate frequency signal is a false signal. The preferred model of the second amplifier is ILA-0003C.
[0030] Example 1
[0031] To better understand the technical content of this invention, specific embodiments are provided in conjunction with the accompanying drawings. Figure 1 The explanation is as follows.
[0032] like Figure 1 As shown, in the frequency conversion link, in the RF link before the first frequency conversion, the main components included in the sequence are the first amplifier, filter, power divider, digitally controlled attenuator, second amplifier and mixer.
[0033] Assuming the frequency of RF signal RF1 is F1, it is down-converted to intermediate frequency (IF) by a mixer. With the input power of RF1 at input P-1 (e.g., -28dBm), the measured power of the IF signal is 12dBm. Then, the input signal is changed to a half-RF signal RF2 with a frequency of F1 / 2. The measured power of the IF signal is now -27dBm, resulting in a half-IF rejection ratio of 39dBc, which is insufficient to meet the general requirement of 45dBc or higher. In practical applications, the filter may be a broadband filter, which inherently provides little to no suppression for the half-RF signal RF2 with a frequency of F1 / 2 corresponding to the RF1 signal at frequency F1. In other words, the filter's operating bandwidth covers both F1 / 2 and F1.
[0034] To determine if the intermediate frequency (IF) signal is a spurious signal, a digitally controlled attenuator can be used to generate attenuations of 5dB and 10dB. Simultaneously, the power change of the IF signal can be measured. If the power decrease of the IF signal (x1dB and x2dB) is greater than 5dB and less than 10dB, and greater than 10dB and less than 20dB, respectively, then the IF signal can be considered a spurious signal. Following this method, the measured IF power values were -34dBm and -43dBm, satisfying the above criteria. Furthermore, (34-27) / 5 = 1.4 is less than (43-27) / 10 = 1.6, confirming that the IF signal is indeed a spurious signal. The input signal... When the signal is changed to RF1, the digitally controlled attenuator is used to generate attenuations of 5dB and 10dB. The measured power of the intermediate frequency (IF) signal is 7.5dBm and 2.2dBm, respectively. The power decrease values are close to and less than 5dB and close to and less than 10dB, indicating that the IF signal is a genuine signal generated by the target being detected. If the measured IF power fluctuates without additional attenuation from the digitally controlled attenuator, it indicates that the IF signal is generated by both the radio frequency (RF) signal RF1 and the semi-RF signal RF2. This can be observed by combining the RF1 and RF2 signals using a power divider and inputting them simultaneously into the frequency converter link. To measure the power of the target RF1 signal, the digitally controlled attenuator can be made to generate 10dB attenuation. Then, the measured stable IF signal power is increased by 10dB to obtain the IF signal power generated by the target RF1 signal. Further processing is then performed. If the IF signal is not stable enough, the attenuation value of the digitally controlled attenuator can be appropriately increased.
[0035] exist Figure 1 In the block diagram shown, although a narrow-bandwidth surface acoustic wave (SAW) filter can be added before the second amplifier to suppress the half-RF signal of each channel, this would significantly increase the noise figure of the frequency conversion link due to the filter's insertion loss (approximately 3dB), making it counterproductive.
[0036] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.
[0037] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if these modifications and variations to the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.
Claims
1. A method for determining a half-radio frequency signal, characterized in that, Based on the RF link before the first frequency conversion, the RF link includes a first amplifier, a filter, a power divider, a digitally controlled attenuator, a second amplifier, and a mixer connected in sequence. The output signal of the mixer is an intermediate frequency (IF) signal. When the IF signal is detected, the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the IF signal is observed to determine whether the IF signal at this time is an RF signal or an IF signal generated by a semi-RF signal, and whether it is a false signal.
2. The method for determining a half-radio frequency signal according to claim 1, characterized in that, By observing the relationship between the attenuation value of the digitally controlled attenuator and the power change value of the intermediate frequency (IF) signal, it can be determined whether the IF signal is generated by radio frequency (RF) or semi-RF signal, and whether it is a spurious signal. Specifically, this includes: The numerically controlled attenuator generates attenuation of adB and 2adB respectively; Observe the digitally controlled attenuator. If, for the two set attenuations, the signal power decreases by x1dB and x2dB respectively, and x1 is greater than a and less than 2a, and x2 is greater than 2a and less than 4a, and x1 / a is less than x2 / 2a, then the intermediate frequency signal is generated by a semi-radio frequency signal and is a spurious signal. If x1 is less than a and x2 is less than 2a, then the intermediate frequency signal is generated by a radio frequency signal. If the digitally controlled attenuator has no additional attenuation and the power of the intermediate frequency signal fluctuates up and down, with the power varying around the set value, and the digitally controlled attenuator is controlled to generate attenuation of adb and 2adB respectively, if the power fluctuation of the signal is observed to be decreasing, it is determined that the signal at this time is generated by both radio frequency signal and semi-radio frequency signal.
3. The method for determining a half-radio frequency signal according to claim 2, characterized in that: The a is greater than or equal to 5.
4. The method for determining a half-radio frequency signal according to claim 2, characterized in that: x1 is less than a, x2 is less than 2a. Specifically, x1 = l1 * a, x2 = l2 * 2a, where l1 and l2 are coefficients less than 1.
5. The method for determining a half-radio frequency signal according to claim 4, characterized in that: Both l1 and l2 are greater than 0.8 and less than 1.
6. The method for determining a half-radio frequency signal according to claim 1, characterized in that: When the input signal power reaches input P-1, the second harmonic suppression of the first amplifier and the second amplifier is greater than 45dBc.
7. The method for determining a half-radio frequency signal according to claim 6, characterized in that: The first amplifier is IPA-0030-27.
8. The method for determining a half-radio frequency signal according to claim 6, characterized in that: The second amplifier is ILA-0003C.
9. The method for determining a half-radio frequency signal according to claim 1, characterized in that: The filter suppresses half-RF signals by more than 45 dBc.