A receiver unit for a far field monitor for a II instrument landing system localizer beacon

Abstract

The application provides a receiver unit of a far field monitoring device of a II instrument landing equipment heading beacon, which comprises an input radio frequency amplifier connected with a frequency synthesizer, the frequency synthesizer being connected with a mixer, the mixer being further connected with an intermediate frequency amplification circuit, the intermediate frequency amplification circuit being further connected with a detection circuit, the mixer comprising a first mixer, an input end of the first mixer being connected with an output end of the amplifier; the intermediate frequency amplification circuit comprising a band pass filter and a first intermediate frequency amplifier, wherein an input end of the band pass filter is connected with an output end of the first mixer, and an output end of the band pass filter is connected with an input end of the first intermediate frequency amplifier; and the detection circuit comprising an AGC controller, a low pass detector, an absolute value detection circuit, a second intermediate frequency amplifier, a second mixer and a local oscillator.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication navigation technology, in particular to a receiver unit of a II instrument landing equipment heading beacon far field monitoring device. BACKGROUND

[0002] The receiver unit is the core unit of the heading beacon far field monitoring device. The last generation of domestic instrument landing equipment is a class I equipment without the function of far field monitoring. The new generation of domestic instrument landing equipment is a class II landing equipment in accordance with the international civil aviation annex 10, which must have the function of far field monitoring of heading. The receiver unit is a necessary component for receiving far field monitoring signals and realizing the function of far field monitoring. SUMMARY

[0003] The purpose of the present application is to solve at least one of the above technical defects.

[0004] To this end, the purpose of the present application is to provide a receiver unit of a II instrument landing equipment heading beacon far field monitoring device.

[0005] In order to achieve the above purpose, the embodiment of the present application provides a receiver unit of a II instrument landing equipment heading beacon far field monitoring device, comprising:

[0006] An input radio frequency amplifier, a frequency synthesizer, a mixer, an intermediate frequency amplification circuit and a detection circuit, wherein,

[0007] The input radio frequency amplifier is connected with the mixer, the frequency synthesizer is connected with the mixer, the mixer is further connected with the intermediate frequency amplification circuit, and the intermediate frequency amplification circuit is further connected with the detection circuit,

[0008] The frequency synthesizer comprises a phase-locked loop frequency synthesizer, a low-pass filter, a voltage-controlled oscillator, an amplifier and a dual-mode pre-divider, wherein the input end of the phase-locked loop frequency synthesizer is connected with a frequency setting instruction, the output end of the phase-locked loop frequency synthesizer is connected with the input end of the low-pass filter, the output end of the low-pass filter is connected with the input end of the voltage-controlled oscillator, the output end of the voltage-controlled oscillator is connected with the input end of the amplifier and the input end of the dual-mode pre-divider respectively, and the output end of the dual-mode pre-divider is connected with the input end of the phase-locked loop frequency synthesizer;

[0009] The mixer comprises a first mixer, and the input end of the first mixer is connected with the output end of the amplifier;

[0010] The input radio frequency amplifier comprises a high-pass filter, an electrically-controlled attenuator and a high-frequency amplifier, wherein the input end of the high-pass filter is connected to a radio frequency signal, the output end of the high-pass filter is connected to the input end of the electrically-controlled attenuator, the output end of the electrically-controlled attenuator is connected to the input end of the high-frequency amplifier, and the output end of the high-frequency amplifier is connected to the input end of the first frequency mixer.

[0011] The intermediate frequency amplification circuit comprises a band-pass filter and a first intermediate frequency amplifier, wherein the input end of the band-pass filter is connected to the output end of the first frequency mixer, and the output end of the band-pass filter is connected to the input end of the first intermediate frequency amplifier.

[0012] The detection circuit comprises an AGC controller, a low-pass detector, an absolute value detection circuit, a second intermediate frequency amplifier, a second frequency mixer and a local oscillator, wherein the second frequency mixer is bidirectionally connected to the first intermediate frequency amplifier, the output end of the second frequency mixer is connected to the input end of the second intermediate frequency amplifier, the output end of the second intermediate frequency amplifier is connected to the input end of the absolute value detection circuit, the output end of the absolute value detection circuit is connected to the input end of the low-pass detector, and a baseband signal is output from the low-pass detector; the output end of the low-pass detector is connected to the input end of the AGC controller, the output end of the AGC controller outputs an AGC voltage signal to the first intermediate frequency amplifier, and the AGC controller outputs a control voltage to the electrically-controlled attenuator.

[0013] Further, the radio frequency signal from the host is connected to the high-pass filter through a high-frequency cable, the control voltage from the detector controls the attenuation of the radio frequency signal by the electrically-controlled attenuator, and the output of the electrically-controlled attenuator is coupled to the input radio frequency amplifier through a capacitor, and the amplified radio frequency signal is fed to the frequency mixer to be mixed with the local oscillator signal.

[0014] Further, when the loop is locked, the voltage-controlled oscillator oscillates a sine wave with a stable correct frequency, and the waveform oscillated by the voltage-controlled oscillator is amplified by the amplifier and then input to the frequency mixer as the local oscillator signal of the frequency mixer, so as to generate a local oscillator frequency of 10.725MHz, which is the first radio frequency signal frequency.

[0015] Further, the amplified radio frequency input signal is coupled to the first input end of the frequency mixer, and the local oscillator signal from the frequency synthesizer is added to the second input end of the frequency mixer, wherein the difference frequency of the radio frequency input signal and the local oscillator signal forms a first intermediate frequency of 10.725MHz, and the local oscillator frequency of 10.725MHz lower than the radio frequency is output from the frequency mixer, and the output load of the frequency mixer is composed of a resonant circuit.

[0016] Further, the intermediate frequency signal is coupled to the input of the first intermediate frequency amplifier, which has a wideband amplifier, and the gain is applied to the AGC voltage control terminal of the first intermediate frequency amplifier, and the output of the first intermediate frequency amplifier is resonated at 10.725 MHz, and the intermediate frequency signal is coupled to the detection circuit.

[0017] Further, the second local oscillator and the mixer include a crystal oscillator and a double balanced mixer, wherein the frequency of the crystal oscillator is 10.675 MHz, the local oscillator frequency is fed to the LO terminal of the mixer, and the 10.725 MHz first intermediate frequency signal is fed to the RF terminal of the mixer, and the difference frequency of the mixer is the second intermediate frequency of the receiver, which is 50 kHz, and the second intermediate frequency amplification circuit is a non-tunable two-stage amplifier composed of two wideband amplifiers, including: a first-stage amplifier and a second-stage amplifier, and the front stage of the first-stage amplifier is a low-pass filter for suppressing the sum frequency component in the output signal of the mixer.

[0018] Further, the absolute value detection circuit includes: a first wideband operational amplifier and a second wideband operational amplifier, a first diode and a second diode, wherein the first diode and the second diode are included in the feedback loop to eliminate the temperature effect, and the high gain of the operational amplifier and the use of feedback technology make the detector more linear;

[0019] The low-pass filter uses a 3 kHz low-pass filter, which is a second-order Butterworth filter composed of an operational amplifier, and attenuates the 50 kHz second intermediate frequency component, so that the baseband signal is composed of a direct current component and a modulation component, wherein the direct current component and the modulation degree are adjusted and calibrated by adjusting the bias potentiometer of the operational amplifier.

[0020] Further, the AGC amplifier is composed of an operational amplifier, and the gain of the operational amplifier and the direct current voltage of the operational amplifier maintain a constant intermediate frequency level within a specific radio frequency input range, and the modulation component is cancelled by the integral capacitor, and the radio frequency level output circuit is composed of an integrated operational amplifier, and when the radio frequency input signal changes from the minimum level to the maximum level, the integrated operational amplifier translates the AGC voltage of the operational amplifier to a direct current voltage varying from 0V to 5V.

[0021] Further, the frequency synthesizer uses a double-mode CMOS large-scale monolithic phase-locked frequency synthesizer programmed by 16-bit parallel code, which integrates a reference frequency divider, a reference oscillator, a digital phase discriminator and a logic control circuit.

[0022] Further, the mixer comprises a mixer, an intermediate frequency transformer and a capacitor in a resonant circuit, wherein the mixer and the intermediate frequency transformer are connected, the intermediate frequency transformer and the capacitor are connected, the amplified radio frequency input signal is coupled to the first input end of the mixer, the local oscillator signal from the frequency synthesizer is added to the second input end, the difference frequency of the radio frequency input signal and the local oscillator signal forms a first intermediate frequency frequency of 10.725MHz, and the local oscillator frequency lower than the radio frequency frequency 10.725MHz is output by the mixer; the output load of the mixer is composed of the intermediate frequency transformer and the capacitor in the resonant circuit, and the intermediate frequency signal on the secondary side of the intermediate frequency transformer is coupled to the crystal filter.

[0023] Additional aspects and advantages of the present application will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following description and drawings or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the accompanying drawings, in which:

[0025] Figure 1 The structure diagram of the receiver unit of the II instrument landing equipment course beacon far field monitoring equipment according to the embodiment of the present application;

[0026] Figure 2 The circuit diagram of the input radio frequency amplifier according to the embodiment of the present application;

[0027] Figure 3 The circuit diagram of the mixer according to the embodiment of the present application;

[0028] Figure 4 The circuit diagram of the intermediate frequency amplification circuit according to the embodiment of the present application;

[0029] Figure 5 The circuit diagram of the frequency synthesizer according to the embodiment of the present application;

[0030] Figure 6 The circuit diagram of the detection circuit according to the embodiment of the present application. DETAILED DESCRIPTION

[0031] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar components have the same or similar reference numerals throughout. The embodiments described below are exemplary and are intended to explain the present application, and should not be understood as limiting the present application.

[0032] The receiver unit of the II instrument landing equipment course beacon far field monitoring equipment of the application is a receiver unit of a beacon machine far field monitoring equipment.

[0033] The receiver unit of the II instrument landing equipment course beacon far field monitoring equipment of the application adopts an input radio frequency amplifier, a frequency synthesizer, a frequency mixer, an intermediate frequency amplification circuit and a detection circuit. The baseband signal generated by the detection is transmitted to a monitor unit through an interface with a radio frequency level signal, and is subjected to digital processing to obtain technical parameters. The working frequency point of the course receiver is set through software of a digital processing unit. The radio frequency signal is from a radio frequency input port of the equipment. The input radio frequency amplifier is connected with the frequency mixer, the frequency synthesizer is connected with the frequency mixer, the frequency mixer is connected with the intermediate frequency amplification circuit, and the intermediate frequency amplification circuit is connected with the detection circuit. The detection circuit is characterized in that it comprises a second frequency mixer, a second intermediate frequency amplifier, an absolute value detector, a 3 kHz low pass filter, an AGC amplifier and a radio frequency level (RF LEVEL) output circuit. The second frequency mixer is connected with the second intermediate frequency amplifier, the second intermediate frequency amplifier is connected with the absolute value detector, the absolute value detector is connected with the 3 kHz low pass filter, the 3 kHz low pass filter is connected with the AGC amplifier, and the AGC amplifier is connected with the radio frequency level (RF LEVEL) output circuit.

[0034] As shown in Figure 1 The receiver unit of the II instrument landing equipment course beacon far field monitoring equipment of the embodiment of the application comprises an input radio frequency amplifier 100, a frequency synthesizer 200, a frequency mixer 300, an intermediate frequency amplification circuit 400 and a detection circuit 500.

[0035] Specifically, the input radio frequency amplifier 100 is connected with the frequency mixer 300, the frequency synthesizer 200 is connected with the frequency mixer 300, the frequency mixer 300 is further connected with the intermediate frequency amplification circuit 400, and the intermediate frequency amplification circuit 400 is further connected with the detection circuit 500.

[0036] The frequency synthesizer 200 comprises a phase-locked loop frequency synthesizer 200, a low pass filter, a voltage-controlled oscillator, an amplifier and a dual-mode pre-divider. The input end of the phase-locked loop frequency synthesizer 200 is connected with a frequency setting instruction, the output end of the phase-locked loop frequency synthesizer 200 is connected with the input end of the low pass filter, the output end of the low pass filter is connected with the input end of the voltage-controlled oscillator, the output end of the voltage-controlled oscillator is respectively connected with the input end of the amplifier and the input end of the dual-mode pre-divider, and the output end of the dual-mode pre-divider is connected with the input end of the phase-locked loop frequency synthesizer 200.

[0037] The mixer 300 comprises a first mixer 300, and an input end of the first mixer 300 is connected with an output end of the amplifier.

[0038] The input radio frequency amplifier 100 comprises a high-pass filter, an electrically-controlled attenuator and a high-frequency amplifier, wherein an input end of the high-pass filter is connected with the radio frequency signal, an output end of the high-pass filter is connected with an input end of the electrically-controlled attenuator, an output end of the electrically-controlled attenuator is connected with an input end of the high-frequency amplifier, and an output end of the high-frequency amplifier is connected with an input end of the first mixer 300.

[0039] The intermediate frequency amplification circuit 400 comprises a band-pass filter and a first intermediate frequency amplifier, wherein an input end of the band-pass filter is connected with an output end of the first mixer 300, and an output end of the band-pass filter is connected with an input end of the first intermediate frequency amplifier.

[0040] The detection circuit 500 comprises an AGC controller, a low-pass detector, an absolute value detection circuit 500, a second intermediate frequency amplifier, a second mixer 300 and a local oscillator, wherein the second mixer 300 is bidirectionally connected with the first intermediate frequency amplifier, an output end of the second mixer 300 is connected with an input end of the second intermediate frequency amplifier, an output end of the second intermediate frequency amplifier is connected with an input end of the absolute value detection circuit 500, an output end of the absolute value detection circuit 500 is connected with an input end of the low-pass detector, and a baseband signal is output from the low-pass detector; an output end of the low-pass detector is connected with an input end of the AGC controller, and an output end of the AGC controller outputs an AGC voltage signal to the first intermediate frequency amplifier; and the AGC controller outputs a control voltage to the electrically-controlled attenuator.

[0041] The following will be described in combination with Figures 2 to 6 The receiver unit of the II instrument landing equipment course beacon far field monitoring equipment of the application will be described in detail.

[0042] The receiver unit of the II instrument landing equipment heading beacon far field monitoring equipment provided by the application generates a baseband signal and a radio frequency level signal through detection and transmits the signals to a monitor unit through an interface for digital processing to obtain technical parameters. The working frequency point of the heading receiver is set through software of a digital processing unit. The radio frequency signal comes from a radio frequency input port of the equipment. Among them: the input radio frequency amplifier 100 is connected with the mixer 300, the frequency synthesizer 200 is connected with the mixer 300, the mixer 300 is connected with the intermediate frequency amplification circuit 400, and the intermediate frequency amplification circuit 400 is connected with the detection circuit 500. The detection circuit 500 is characterized by comprising a second mixer 300, a second intermediate frequency amplifier, an absolute value detector, a 3 kHz low-pass filter, an AGC amplifier and a radio frequency level (RF LEVEL) output circuit. Among them: the second mixer 300 is connected with the second intermediate frequency amplifier, the second intermediate frequency amplifier is connected with the absolute value detector, the absolute value detector is connected with the 3 kHz low-pass filter, the 3 kHz low-pass filter is connected with the AGC amplifier, and the AGC amplifier is connected with the radio frequency level (RF LEVEL) output circuit.

[0043] The receiver unit of the II instrument landing equipment heading beacon far field monitoring equipment is in the form of superheterodyne reception, in addition to the above-mentioned main components, it also comprises a baseband signal output port, a frequency measurement signal output port, a level measurement signal output port and an input port (including: +12V, -12V power supply, GND, CLK, DATA, ENB signal, radio frequency input).

[0044] As shown in Figure 2 , the radio frequency signal (RF) received through the antenna is input to the radio frequency input end of the heading receiver, the input radio frequency amplifier 100 comprises a high-pass filter Z1, an electrically tunable attenuator N1 and a high-frequency broadband amplifier N2, wherein: the radio frequency signal from the host is connected to the 108MHz high-pass filter through a high-frequency cable, the control voltage from the detector controls the attenuation of the radio frequency signal of the electrically tunable attenuator N1, the output of N1 is capacitively coupled to the integrated broadband amplifier N2, and the amplified radio frequency signal is fed to the mixer 300 N3 and mixed with the local oscillator signal.

[0045] As shown in Figure 5As shown in the figure, the frequency synthesizer 200 includes a frequency synthesizer 200N5, a low pass filter N6, a voltage controlled oscillator N8, a dual mode pre- frequency divider N7 and an amplifier N9, wherein: the frequency synthesizer 200N5 is connected with the low pass filter N6 and the dual mode pre-frequency divider N7 respectively, the output of the low pass filter N6 is connected with the voltage controlled oscillator N8, the output of the voltage controlled oscillator N8 is connected with the input of N7, and the output of the voltage controlled oscillator N8 is connected with the input of the amplifier N9. The frequency synthesizer 200N5 adopts a dual mode CMOS large-scale monolithic phase-locked frequency synthesizer 200 programmed by 16-bit parallel code, which integrates reference frequency divider, reference oscillator, digital phase discriminator, various logic control circuits and other components. With N6, N7 and N8, the loop automatically changes the frequency ratio to realize frequency synthesis. When the loop is locked, the voltage controlled oscillator N8 oscillates out a sine wave with a stable correct frequency, at this time, the pins 7 and 8 of the frequency synthesizer 200N5 present high level and negative pulse waveforms, and the pin 9 presents square waveforms. The waveform oscillated by the voltage controlled oscillator N8 is amplified by the amplifier N9 and input to the mixer 300 as the local oscillator signal of the mixer 300, that is, according to the received radio frequency signal, a local oscillator frequency lower than the radio frequency signal frequency 10.725MHz is generated.

[0046] As shown in the figure, Figure 3 As shown in the figure, the mixer 300 includes a mixer 300N3, an intermediate frequency transformer T1 in a resonant circuit and a capacitor C24, wherein: the mixer 300N3 is connected with the intermediate frequency transformer T1, and the intermediate frequency transformer T1 is connected with the capacitor C24. The amplified radio frequency input signal is coupled to the first input end 3 pin of the mixer 300N3, and the local oscillator signal from the frequency synthesizer 200 is added to the second input end 6 pin, the difference frequency of the radio frequency input signal and the local oscillator signal forms a first intermediate frequency frequency of 10.725MHz, and the local oscillator frequency lower than the radio frequency frequency 10.725MHz is output by the pin 2 of N3. The output load of N3 is composed of the resonant circuit T1 and C35, and the intermediate frequency signal on the secondary side of T1 is coupled to the crystal filter.

[0047] As shown in the figure, Figure 4As shown, the intermediate frequency amplification circuit 400 comprises a crystal filter Z2, an integrated intermediate amplifier circuit N4, and capacitors C36, C92 and other peripheral circuits, wherein: the crystal filter Z2 is connected with the capacitors C36, C92 respectively, and the C92 is connected with the integrated intermediate amplifier circuit N4. The center frequency of the crystal filter Z2 is 10.725MHz, the bandwidth is ±20kHz, the 60dB stopband attenuation reaches ±100kHz, and the selection characteristics of the heading receiver are mainly determined by the crystal filter. The capacitors C36, C92 are used to correct the in-band ripple of the crystal filter. The intermediate frequency signal is added to the input end of the first intermediate amplifier N4 through the crystal filter. There is a wideband amplifier in N4, and the gain is controlled by the AGC voltage added to the pin 2 of N4. The intermediate frequency signal is coupled to the detection circuit 500 after the output of the intermediate amplifier is resonated at 10.725MHz.

[0048] As Figure 6As shown, the detection circuit 500 includes a local oscillator / mixer 300, a second intermediate frequency amplifier, an absolute value detector, a 3 kHz low pass filter, an AGC amplifier, a radio frequency level (RF LEVEL) output circuit, wherein: the second mixer 300 is connected with the second intermediate frequency amplifier, the second intermediate frequency amplifier is connected with the absolute value detector, the absolute value detector is connected with the 3 kHz low pass filter, the 3 kHz low pass filter is connected with the AGC amplifier, and the AGC amplifier is connected with the radio frequency level (RF LEVEL) output circuit. The second local oscillator / mixer 300 is composed of a crystal oscillator G1 and a double-balance mixer 300N10. The frequency of the crystal oscillator is 10.675 MHz, and this local oscillator frequency is fed to the L0 end of the mixer 300. The 10.725 MHz first intermediate frequency signal is fed to the RF end of the mixer 300, and the difference frequency signal of the mixer 300 is the second intermediate frequency 50 kHz of the receiver. The second intermediate frequency amplifier circuit 400 is a non-tunable two-stage amplifier composed of two stages of wideband amplifiers N11 and N12. The front stage of the amplifier N11 is a low pass filter which suppresses the sum frequency component in the output signal of the mixer 300. The absolute value detector is composed of two wideband operational amplifiers N13 and N14, diodes V2 and V3. The diodes are included in the feedback loop in order to eliminate the temperature influence, and the detector is made more linear by the high gain of the operational amplifier and the use of feedback technology. The 3 kHz low pass filter is a second-order Butterworth filter composed of an operational amplifier N15, which attenuates the 50 kHz second intermediate frequency component, so that the baseband signal is output at the 6 end of N15. The baseband signal component is composed of a direct current component and 90 Hz and 150 Hz modulation components. The adjustment and calibration of the direct current component and the modulation degree and parameters are completed by the bias adjustment potentiometer RP2 of the operational amplifier. The AGC amplifier is composed of an operational amplifier N16. The gain (R41 / R40) of N16 and the direct current voltage at the 12 end of N16 maintain a constant intermediate frequency level within a specific radio frequency input range. The modulation component is cancelled by the integration capacitor C54. The radio frequency level output circuit is composed of an integrated operational amplifier N17. When the radio frequency input signal changes from a specific minimum level to a maximum level, N17 translates the AGC voltage at the 14 end of N16 into a direct current voltage which changes from 0 V to 5 V.

[0049] The present application can realize that the receiver unit can be applied in the II type instrument landing equipment heading beacon far field monitoring equipment, and is used for monitoring and measuring the far field radiation signal, and meets the system performance requirements of the II type instrument landing equipment in the international civil aviation annex 10.

[0050] Technical index of the receiver unit

[0051] 1) Frequency range: 108.1 MHz-111.95 MHz.

[0052] 2) Frequency deviation: better than ±2x10-5.

[0053] 3) Channel spacing: 50 kHz.

[0054] 4) Bandwidth: 6 dB better than ±18 kHz.

[0055] 5) Selectivity: better than -45 dB at nominal frequency ±100 kHz.

[0056] 6) Sensitivity: no worse than -75 dBm.

[0057] 7) AGC range: -20 dBm to -75 dBm.

[0058] The receiver unit of the II instrument landing equipment course beacon far field monitoring equipment according to the embodiment of the present application is used for monitoring and measuring far field radiation signals, and meets the system performance requirements of the II instrument landing equipment in the International Civil Aviation Annex 10. The domestic blank is filled.

[0059] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0060] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and purposes of the present application within the scope of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A receiver unit for a II Instrument Landing Equipment (ILI) heading beacon far-field monitoring device, characterized in that, include: The input circuit includes an RF amplifier, a frequency synthesizer, a mixer, an intermediate frequency amplifier, and a detector. The input RF amplifier is connected to the mixer, the frequency synthesizer is connected to the mixer, the mixer is further connected to the intermediate frequency amplifier circuit, and the intermediate frequency amplifier circuit is further connected to the detector circuit. The frequency synthesizer includes: a phase-locked loop (PLL) frequency synthesizer, a low-pass filter, a voltage-controlled oscillator (VCO), an amplifier, and a dual-mode prescaler. The input of the PLL frequency synthesizer is connected to a frequency setting command. The output of the PLL frequency synthesizer is connected to the input of the low-pass filter. The output of the low-pass filter is connected to the input of the VCO. The output of the VCO is connected to the inputs of the amplifier and the dual-mode prescaler. The output of the dual-mode prescaler is connected to the input of the PLL frequency synthesizer. The mixer includes: a first mixer, wherein the input terminal of the first mixer is connected to the output terminal of the amplifier; The input RF amplifier includes a high-pass filter, an electrically adjustable attenuator, and a high-frequency amplifier. The input terminal of the high-pass filter is connected to an RF signal, the output terminal of the high-pass filter is connected to the input terminal of the electrically adjustable attenuator, the output terminal of the electrically adjustable attenuator is connected to the input terminal of the high-frequency amplifier, and the output terminal of the high-frequency amplifier is connected to the input terminal of the first mixer. The intermediate frequency amplifier circuit includes a bandpass filter and a first intermediate frequency amplifier, wherein the input terminal of the bandpass filter is connected to the output terminal of the first mixer, and the output terminal of the bandpass filter is connected to the input terminal of the first intermediate frequency amplifier. The detection circuit includes: an AGC controller, a low-pass detector, an absolute value detector circuit, a second intermediate frequency amplifier, a second mixer, and a local oscillator. The second mixer is bidirectionally connected to the first intermediate frequency amplifier, and its output is connected to the input of the second intermediate frequency amplifier. The output of the second intermediate frequency amplifier is connected to the input of the absolute value detector circuit, and the output of the absolute value detector circuit is connected to the input of the low-pass detector, which outputs a baseband signal. The output of the low-pass detector is connected to the input of the AGC controller, and the output of the AGC controller outputs an AGC voltage signal to the first intermediate frequency amplifier. Furthermore, the AGC controller outputs a control voltage to the electrically adjustable attenuator. The high-pass filter has a frequency of 108MHz. The receiver unit also includes a baseband signal output port, a frequency measurement signal output port, a level measurement signal output port, and an input port.

2. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The radio frequency signal from the host is connected to the high-pass filter via a high-frequency cable. The control voltage from the detector controls the electronically tunable attenuator to attenuate the radio frequency signal. The output of the electronically tunable attenuator is coupled to the high-frequency amplifier via a capacitor. The amplified radio frequency signal is fed to the mixer and mixed with the local oscillator signal.

3. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring equipment as described in claim 1, characterized in that, When the loop is locked, the voltage-controlled oscillator oscillates a sine wave with a stable and correct frequency. The waveform oscillated by the voltage-controlled oscillator is amplified by the amplifier and input to the mixer as the local oscillator signal of the mixer. Based on the received radio frequency signal, a local oscillator frequency of 10.725MHz is generated as the first radio frequency signal frequency.

4. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The amplified radio frequency input signal is coupled to the first input terminal of the mixer, and the local oscillator signal from the frequency synthesizer is added to the second input terminal of the mixer. The difference frequency between the radio frequency input signal and the local oscillator signal forms a first intermediate frequency of 10.725MHz. The local oscillator frequency output by the mixer is 10.725MHz lower than the radio frequency frequency. The output load of the mixer consists of a resonant circuit.

5. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring equipment as described in claim 1, characterized in that, The intermediate frequency (IF) signal is applied to the input of the first IF amplifier after passing through a crystal filter. The first IF amplifier contains a broadband amplifier, and the gain is applied to the AGC voltage control terminal of the first IF amplifier. The output of the first IF amplifier resonates at 10.725MHz. The IF signal is coupled to the detection circuit.

6. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The local oscillator is composed of a crystal oscillator, while the second mixer is a double-balanced mixer. The crystal oscillator has a frequency of 10.675MHz, which is fed to the LO terminal of the mixer. The first intermediate frequency signal of 10.725MHz is fed to the RF terminal of the mixer. The difference frequency of the mixer is the second intermediate frequency of the receiver, 50kHz. The second intermediate frequency amplifier circuit is an untuned two-stage amplifier composed of two broadband amplifier stages, including a first-stage amplifier and a second-stage amplifier. The pre-stage of the first-stage amplifier is a low-pass filter used to suppress the sum frequency component in the output signal of the mixer.

7. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The absolute value detection circuit includes: a first broadband operational amplifier and a second broadband operational amplifier, a first diode and a second diode, wherein the first diode and the second diode are included in the feedback loop to eliminate the temperature effect, and the detector is made closer to linear by the high gain of the operational amplifier and the use of feedback technology. The low-pass filter is a 3kHz low-pass filter, which is a second-order Butterworth filter composed of operational amplifiers. It attenuates the second intermediate frequency component of 50kHz. Therefore, the baseband signal consists of DC component and modulation component. The adjustment and calibration of DC component and modulation parameters are accomplished by the bias adjustment potentiometer of the operational amplifier.

8. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The AGC controller consists of an operational amplifier. The absolute value detector operates within the RF input range of -20dBm to -75dBm. The gain and DC voltage of the operational amplifier maintain a constant intermediate frequency level. The modulation component is canceled through the integrating capacitor. The RF level output circuit consists of an integrated operational amplifier. When the RF input signal changes from the minimum level to the maximum level, the integrated operational amplifier translates the AGC voltage of the operational amplifier into a DC voltage that varies from 0V to 5V.

9. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The frequency synthesizer uses a dual-mode CMOS large-scale monolithic phase-locked frequency synthesizer programmed with 16-bit parallel code, which integrates a reference frequency divider, a reference oscillator, a digital phase detector, and logic control circuitry.

10. The receiver unit of the II Instrument Landing Equipment heading beacon far-field monitoring device as described in claim 1, characterized in that, The first mixer includes a mixer ADE-1MH, an intermediate frequency transformer (IF transformer) and a capacitor in a resonant circuit. The mixer ADE-1MH is connected to the IF transformer, and the IF transformer is connected to the capacitor. The amplified radio frequency (RF) input signal is coupled to the first input terminal of the mixer ADE-1MH. The local oscillator (LO) signal from the frequency synthesizer is added to the second input terminal. The difference frequency between the RF input signal and the LO signal forms a first IF frequency of 10.725MHz. The LO frequency output by the mixer ADE-1MH is lower than the RF frequency of 10.725MHz. The output load of the mixer ADE-1MH consists of the IF transformer and the capacitor in the resonant circuit. The IF signal on the secondary winding of the IF transformer is coupled to a crystal filter.

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