CN209844939U - VHF microwave frequency hopping radio station receiver - Google Patents
VHF microwave frequency hopping radio station receiver Download PDFInfo
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Abstract
The utility model provides a VHF microwave frequency hopping radio receiver, which is connected with a preposed low noise amplification and gain adjustment circuit in sequence from a radio frequency receiving antenna; a frequency hopping filtering and driving amplifying circuit; a first time frequency conversion circuit; an intermediate frequency filtering and amplifying circuit; a second frequency conversion circuit; an intermediate frequency filtering and amplifying circuit; meanwhile, a frequency synthesizer for providing frequency signals for the first secondary frequency conversion circuit and the second secondary frequency conversion circuit is integrated; the frequency hopping filtering and driving amplifying circuit adopts a two-stage cascade form and comprises a first-stage frequency hopping filter, a second-stage frequency hopping filter and a first-stage 15-20 dB driving amplifier which is arranged between the first-stage frequency hopping filter and the second-stage frequency hopping filter and is inserted. The utility model discloses a VHF microwave frequency hopping radio station receiver reaches frequency hopping filter through continuous quick change or with switch change band pass filter's whole or partial parameter and will realize the quick transformation of wave filter central frequency.
Description
Technical Field
The utility model relates to a frequency hopping radio station receiver field, in particular to realize VHF microwave frequency hopping radio station receiver to functions such as VHF radio frequency signal low noise amplification, frequency band filtering and down conversion to intermediate frequency of big dynamic range.
Background
The radio station is an instant communication device which appears in the early stage of the development of radio communication, is a main means for keeping communication in a maneuvering state due to the advantages of lightness, flexibility, convenience in use and the like, and becomes a dual-purpose mainstream device for military and civil use of communication in motion and field communication. The early wireless radio station can only transmit conversation service, so that the data transmission and dynamic video interaction capacity is developed, the communication mode is also developed into cluster dynamic networking communication and frequency hopping communication from point-to-point and fixed-frequency voice communication, and the new service requirement of the radio station puts high requirements on the high-speed data transmission, large dynamic working capacity, wide linearity, low noise, frequency agility, anti-interference and other capacities of the radio station.
The VHF ultra-short wave radio frequency receiver mainly has the functions of filtering weak interfering electric signals, filtering the interfering signals, processing the signals into intermediate frequency signals through a series of measures such as signal amplification, down-conversion and the like, and finally completing demodulation by a digital circuit. The radio frequency receiver mainly comprises a superheterodyne receiver, a low intermediate frequency receiver, a zero intermediate frequency receiver and the like. The superheterodyne receiver is the most commonly used receiver at present, and adopts one or more times of down-conversion to down-convert the radio frequency to a lower intermediate frequency, and adopts a filter to filter the image frequency and various combined interference frequencies through reasonable selection of the intermediate frequency and the local oscillation frequency. The superheterodyne receiver is widely used because of its advantages of stable and reliable operation, easy realization, and excellent performance. The receiver is influenced by the output power of a transmitter, the communication distance, electromagnetic disturbance, environmental noise and artificial interference, the amplitude of a signal received by an antenna is always in a dynamic range of more than 100dB, and in order to ensure that the receiver can normally receive the signal in the large dynamic range, an automatic gain control system is required to be introduced into a radio frequency link, so that the receiver can receive a weak signal with low noise and simultaneously can keep the linearity of a circuit when high power is input, the large dynamic range of the radio frequency signal can be compressed into an intermediate frequency dynamic range of less than 20dB, and the demodulation of a digital circuit can be conveniently completed.
The radio station mainly comprises a short-wave radio station and an ultra-short-wave radio station according to the working frequency band, wherein the VHF radio station mainly works in the ultra-short-wave radio station with a microwave band of 30-88 MHz and is communicated in a mode mainly based on line-of-sight transmission. Compared with short wave communication, VHF frequency communication quality is good, channel capacity is large, influence of day and night and seasonal changes is small, and communication is stable and widely applied. Compared with UHF (over 100 MHz), VHF communication has certain diffraction and ground wave propagation characteristics, the signal coverage range can still reach dozens of kilometers in a field operation environment with moderate fluctuation, and the VHF communication is a main means of ground communication and ground-air cooperative communication. The ultrashort wave channel can support high-speed data transmission, and an active tactical ultrashort wave radio station can transmit data of more than 16kbit/s, which far exceeds the data transmission capacity of the ultrashort wave radio station.
In order to improve the anti-interference capability of the ultrashort wave radio station, two spread spectrum technologies, namely direct sequence spread spectrum and frequency hopping, are mainly adopted in the industry. Direct sequence spread spectrum has spectrum concealment and confidentiality, but cannot overcome narrow-band interference, so that the ultra-short wave radio station generally does not adopt a direct spread spectrum technology. The frequency hopping technology overcomes narrow-band interference by quickly changing working frequency and avoiding interference frequency spectrum, and meanwhile, a plurality of subnets can adopt orthogonal frequency hopping networking to improve the channel utilization rate and reduce the probability of being detected by enemies, so that the frequency hopping communication technology is widely adopted in VHF communication. With the development of the technology, the hopping speed of the VHF frequency hopping radio station is faster and faster, and at present, thousands of hops per second are achieved, so that high requirements on high-speed frequency hopping filtering and frequency hopping synchronization are provided.
At present, the working frequency of an advanced ultrashort wave radio station covers 30 MHz-2000 MHz, the radio station has multiple radio frequency channels, the capacity of supporting the simultaneous working of narrowband and broadband channels is realized, and the frequency hopping rate can reach 1000 hops/second. The frequency hopping technology of the radio station is rapidly developed, the hopping speed is higher and higher, and comprehensive anti-interference technologies such as adaptive frequency hopping, signal power adaptive and variable speed frequency hopping are developed. The VHF ultrashort wave radio station receiver proposed in document [ 1 ] (majors scholars thesis of university of electronic technology, 2018) has a large dynamic range, and a corresponding receiver channel linearization technique, a fast AGC (automatic gain control) technique, and a agile low noise frequency synthesizer technique have been developed. The dynamic range of the whole machine is-120 dBm-0 dBm, the signal compression is not more than 1dB when the maximum amplitude is input, the frequency agility time is not more than 200us, the position of one local oscillator phase noise deviating from the main frequency spectrum by 2kHz is not more than-80 dBc/Hz, and the position of two local oscillators deviating from the main frequency spectrum by 20kHz is not more than-120 dBc/Hz. The receiver has the advantages that the overall technical performance meets the requirements, the receiver has high-speed frequency hopping capability, can meet the dynamic networking of a plurality of mobile radio station nodes, and supports the directional development of various forms and types of services such as voice communication, data transmission, dynamic video interaction and the like. Document [ 2 ] (penwenouin. research and implementation of U/V channel module of ultra-short wave radio, master academic paper of electronic technology university, 2018) introduces an anti-interference ultra-short wave radio channel module, which includes subsystems such as a receiver, a transmitter and a frequency synthesizer. The transmitting power of a transmitting channel of the module is 10 +/-1 dBm, the broadband transmitting broadband noise is less than-134 dBm/Hz, the stray rejection is better than 70dBc, and the ALC (amplitude stabilized) response time is less than 50 us. The noise coefficient of a receiving channel is less than 4.5dB, the output amplitude of the intermediate frequency is minus 5 +/-5 dBm, and the dynamic range of the receiver exceeds 120 dB. Document [ 3 ] (charkhahi. short wave signal receiver research. master academic paper of Nanjing university of technology, 2015.) designs a short wave signal receiver, which has the characteristics of large dynamic processing capacity, full-band sampling, high-speed data acquisition and transmission and the like, and designs a low-noise amplification link by adopting a balanced amplification and negative feedback principle, and realizes high selectivity of a receiving channel by adopting a high-order filter. The receiver intermediate frequency adopts ADC with high digit number and high sampling rate, which ensures dynamic range and precision of sampling, and its high data rate adopts ten-gigabit Ethernet transmission. Document [ 4 ] (quality of sun, quality of a certain ultrashort wave radio station frequency synthesizer design and implementation. master school's paper of western's university of electronics technology, 2015.) adopts technologies such as superheterodyne down-conversion, wide-band large dynamic receiver, fast automatic gain control to realize a large dynamic range receiver, and adopts a frequency hopping system to realize an anti-interference function. The literature designs a frequency synthesizer applied to an anti-interference high-speed data transmission radio station, wherein a local oscillator adopts a agile frequency hopping frequency source, the frequency range is 154.8 MHz-212.8 MHz, the frequency hopping step is 25kHz, a decimal frequency division phase-locked loop scheme is used, a two-way control voltage-controlled oscillator is adopted, the contradiction between phase noise and locking time is balanced, the phase noise is better than-105 dBc/Hz @1kHz, and the frequency locking time is less than 130 us. The frequency of the second local oscillator is 124.416MHz, and the second local oscillator is a fixed point frequency and is realized by adopting a phase-locked loop. The frequency synthesizer meets the performance index requirements of the radio station, has advantages in the aspects of structure, power consumption and the like, and has high frequency hopping speed and signal spectrum purity.
At present, a first-stage amplifier of a receiving link of an ultra-short wave radio station is a low-noise amplifier, has higher gain, and the saturated output power is generally in the magnitude of 20dBm, so that the maximum power input by the ultra-short wave radio station is generally near 0dBm, and the receiving dynamic range of the ultra-short wave radio station is generally-120-0 dBm; therefore, the dynamic range of the conventional VHF receiver in the industry is generally-120-0 dBm, and the first-stage amplifier is overloaded when the dynamic range exceeds 0dBm, so that nonlinearity is generated and the use of the system is influenced.
In addition, too long an AGC lock-in time may result in the AGC not being able to track the change of the signal amplitude in time, and too short a lock-in time may result in the AGC leveling-out of the AM modulation characteristic, i.e. a counter-modulation phenomenon is generated. Therefore, AGC is not suitable for communication systems with multiple coexisting modulations, especially AM (including ASK) modulation. Thus, the existing VHF receiver in the industry generally adopts Automatic Gain Control (AGC) to compress the dynamic range, but the AGC locking time cannot be too long or too short, the loop bandwidth needs to be carefully adjusted, once the loop bandwidth is adjusted, the loop bandwidth is fixed and unchanged, and the loop bandwidth cannot be adjusted in real time according to the debugging mode in the actual use process.
SUMMERY OF THE UTILITY MODEL
The utility model discloses to the above-mentioned defect of present ultrashort wave radio station, provide a VHF microwave frequency hopping radio station receiver, this ultrashort wave radio station can realize that VHF radio frequency signal low noise to big dynamic range enlargies, frequency band filtering and down the frequency conversion to functions such as intermediate frequency. The utility model discloses the applied frequency channel is 30 ~ 88MHz, and noise figure is less than 4dB, and dynamic range exceeds 140dB, adopts high-speed digital control, but self-adaptation ground adjustment amplifier circuit gain changes in order to adapt to input signal's amplitude, compares in traditional automatic gain control, has high-speed locking, can not be absorbed in advantages such as saturation.
The utility model discloses a realize that the technical scheme that its technical purpose adopted is: a VHF microwave frequency hopping radio receiver is characterized in that a front low-noise amplification circuit and a gain adjustment circuit are sequentially connected from a radio frequency receiving antenna; a frequency hopping filtering and driving amplifying circuit; a first time frequency conversion circuit; an intermediate frequency filtering and amplifying circuit; a second frequency conversion circuit; an intermediate frequency filtering and amplifying circuit; meanwhile, a frequency synthesizer for providing local oscillation frequency signals for the first frequency conversion circuit and the second frequency conversion circuit is integrated; the frequency hopping filtering and driving amplifying circuit adopts a two-stage cascade form and comprises a first-stage frequency hopping filter, a second-stage frequency hopping filter and a first-stage 15-20 dB driving amplifier which is arranged between the first-stage frequency hopping filter and the second-stage frequency hopping filter and is inserted.
The utility model discloses a VHF microwave frequency hopping radio station receiver reaches frequency hopping filter through continuous quick change or with switch change band pass filter's whole or partial parameter and will realize the quick transformation of wave filter central frequency.
Further, in the VHF microwave frequency hopping station receiver described above: a front-end high-power protection circuit is arranged between the preposed low-noise amplification and gain adjustment circuit and the antenna; the front-end high-power protection circuit comprises an amplitude limiting circuit and a band filter; the amplitude limiting circuit limits the amplitude of a large signal received by the antenna to the same amplitude and then is connected with a 30-88 MHz frequency band filter for inhibiting out-of-band interference signals.
Further, in the VHF microwave frequency hopping station receiver described above: the amplitude limiting circuit comprises a diode D11, a diode D12, a diode D13, a diode D14 and a Zener diode D10; the antenna is respectively connected with the P pole of the diode D11 and the N pole of the diode D14, the N pole of the diode D11 is connected with the N pole of the diode D12, the P pole of the diode D12 is grounded, the P pole of the diode D14 is connected with the P pole of the diode D13, the N pole of the diode D13 is grounded, the N pole of the zener diode D10 is connected with the common end connected with the N pole of the diode D11 and the N pole of the diode D12, and the P pole of the zener diode D10 is connected with the common end connected with the P pole of the diode D13 and the P pole of the diode D14.
Further, in the VHF microwave frequency hopping station receiver described above: the preposed low-noise amplification and gain adjustment circuit comprises a first path of 30dB attenuator, a second path of 10dB attenuator, a third path of 20dB gain conventional drive amplifier and a fourth path of amplification and gain channels consisting of a 30dB gain low-noise amplifier; one-out-of-four radio frequency switches arranged in front of and behind the four amplifying and gain channels; a first RMS logarithmic detector; a resistor R21; an AD converter;
the signal input end is coupled out by a resistor R21 and connected with a first RMS logarithmic detector, and the output of the first RMS logarithmic detector is connected with an AD converter to generate a control signal of a radio frequency switch, so that the control signal can be amplified from four paths and gated from one path by a gain channel according to the amplitude of the current signal.
Further, in the VHF microwave frequency hopping station receiver described above: the intermediate frequency filtering and amplifying circuit is arranged behind the first frequency conversion circuit and comprises a first narrow-band filter, a resistor R53, a second RMS logarithmic detector, a first-stage automatic gain controller and a first driving amplifier;
an intermediate frequency signal output by the first frequency conversion circuit (4) is filtered and filtered by a first narrow band filter, amplified by a first automatic gain controller and amplified and output by a first drive amplifier; the automatic gain control of the first automatic gain controller adopts a feedforward mode, the filtered output of the first narrow-band filter is coupled out a part of power by a resistor R53 and is connected with the second RMS logarithmic detector, and the analog voltage detected by the second RMS logarithmic detector is subjected to AD conversion and digital processing and then controls the first automatic gain controller to finish gain adjustment.
Further, in the VHF microwave frequency hopping station receiver described above: the second secondary frequency conversion circuit outputs a medium-frequency signal, the medium-frequency signal is processed by a medium-frequency filtering and amplifying circuit, and the medium-frequency filtering and amplifying circuit comprises a second narrow-band filter, a second automatic gain controller and a second driving amplifier; the intermediate frequency signal is output after being amplified in two stages by a second automatic gain controller and a second drive amplifier;
the second automatic gain controller adopts a feedforward circuit and a feedback circuit integrated mode to carry out power control on the gain control box; the feedforward circuit carries out field intensity detection before the second automatic gain controller, and the feedback circuit carries out field intensity detection after the second automatic gain controller;
the feed-forward circuit comprises a resistor R73 and a third RMS logarithmic detector; the output of the second time frequency conversion circuit is that a middle frequency signal is coupled out by a resistor R73, and part of power is connected with a third RMS logarithmic detector;
the feedback circuit comprises a resistor R76 and a fourth RMS logarithmic detector; the intermediate frequency signal output by the second driving amplifier is coupled out of a part of power by a resistor R76 and is connected with a fourth RMS logarithmic detector;
analog voltages detected by the third RMS logarithmic detector and the fourth RMS logarithmic detector are sent to the CPLD processor through AD conversion, and are subjected to DA conversion after being calculated by a gain and power algorithm, so that the second automatic gain controller is controlled to complete double adjustment of gain and amplitude, and AGC and ALC control are realized at the same time.
Further, in the VHF microwave frequency hopping station receiver described above: and an online monitoring module is also arranged for carrying out temperature detection, temperature calibration and circuit state monitoring.
The present invention will be further described with reference to the accompanying drawings and the detailed description.
Drawings
Fig. 1 is a link block diagram of a VHF rf receiver according to embodiment 1 of the present invention.
Fig. 2 is a block diagram of the high power protection circuit according to embodiment 1 of the present invention.
Fig. 3 is a schematic block diagram of a front-end large dynamic low noise amplifier circuit according to embodiment 1 of the present invention.
Fig. 4 is the frequency hopping filtering and driving amplification block diagram of embodiment 1 of the present invention.
Fig. 5 is a block diagram of an intermediate frequency filtering and amplifying circuit according to embodiment 1 of the present invention.
Fig. 6 is a block diagram of the intermediate frequency filtering and amplifying circuit in embodiment 1 of the present invention.
Fig. 7 is a block diagram of the digital control part according to embodiment 1 of the present invention.
Detailed Description
In embodiment 1, a circuit structure of a radio receiver is designed in this embodiment as shown in fig. 1, and a received signal of 30 to 88MHz is down-converted to a 21.4MHz intermediate frequency and amplified for output. The circuit mainly comprises: a high-power protection circuit 1; a preposed low-noise amplifying and gain adjusting circuit 2; a frequency hopping filtering and driving amplifying circuit 3; a first secondary frequency conversion circuit 4; an intermediate frequency filtering and amplifying circuit 5; a second frequency conversion circuit 6; an intermediate frequency filtering and amplifying circuit 6; meanwhile, the system is integrated with a frequency synthesizer and on-line monitoring functions of temperature detection, temperature calibration, circuit state monitoring and the like.
In this embodiment, the high-power protection circuit is used for limiting the amplitude of the radio frequency input power and protecting the post-stage circuit from being burnt. Protection circuit as shown in fig. 2, the front-end high power protection circuit 1 includes a limiter circuit and a band filter 15; the amplitude limiting circuit limits the amplitude of a large signal received by the antenna to be connected with a 30-88 MHz band filter 15 for suppressing out-of-band interference signals. The specific limiting circuit is shown in fig. 2, and includes a diode D11, a diode D12, a diode D13, a diode D14, and a zener diode D10; the antenna is respectively connected with the P pole of the diode D11 and the N pole of the diode D14, the N pole of the diode D11 is connected with the N pole of the diode D12, the P pole of the diode D12 is grounded, the P pole of the diode D14 is connected with the P pole of the diode D13, the N pole of the diode D13 is grounded, the N pole of the zener diode D10 is connected with the common end connected with the N pole of the diode D11 and the N pole of the diode D12, and the P pole of the zener diode D10 is connected with the common end connected with the P pole of the diode D13 and the P pole of the diode D14.
In the embodiment, the amplitude limiting circuit adopts four Schottky diodes and one Zener diode, when a large signal is input and the signal operates in a positive half cycle, the diode D11 and the diode D13 are conducted, and the Zener diode D10 is subjected to reverse breakdown, so that a grounding path is formed; when the signal operates in the negative half cycle, the diode D12 and the diode D14 are conducted, and the zener diode D10 also breaks down in the reverse direction, so that a ground path is formed, and the signal amplitude of the main path is reduced. After the strong signal passes through, the Zener diode D10 is cut off rapidly, when the input signal is a small signal, the signal can not break down the Zener diode D10 no matter whether the positive half shaft or the negative half shaft is connected with the ground, and the signal transmission of the main circuit is not influenced. The amplitude limiting circuit can reduce a high-power signal with an input end of 40dBm to 25dBm, and a band filter 15 with the frequency of 30-88 MHz is arranged behind the amplitude limiting circuit and used for suppressing out-of-band interference signals.
In this embodiment, the first-stage amplifier of the receiving link adopts a multi-path amplification network as a front low-noise amplification and gain adjustment circuit 2, and as shown in fig. 3, the circuit includes four paths of amplification and gain channels, which are composed of a first path of 30dB attenuator 24, a second path of 10dB attenuator 25, a third path of 20dB gain conventional driving amplifier 26, and a 30dB gain low-noise amplifier 27; a one-out-of-four radio frequency switch 23 arranged in front of and behind the four amplifying and gain channels; a first RMS log detector 22; a resistor R21; an AD converter. The signal input end is coupled out by a resistor R21 and connected with the first RMS logarithmic detector 22, and the output of the first RMS logarithmic detector 22 is connected with the AD converter to generate a control signal of the radio frequency switch 23, so that one path can be selected from four paths of amplification and gain channels according to the amplitude of the current signal.
As shown in fig. 2. When the power of an input signal is in a range of-10 dBm to 20dBm, the signal gates a first path of 30dB attenuator 24; when the input signal power is in the range of-30 dBm to-10 dBm, the signal gates the second path of 10dB attenuator 25; when the power of the input signal is in an interval of-60 dBm to-30 dBm, the signal gates a third 20dB gain amplifier 26, and the third 20dB gain amplifier adopts a conventional drive amplifier without using a low-noise amplifier; when the input signal power is in the interval of-120 dBm to-60 dBm, the signal gates the low noise amplifier 27 with 30dB gain in the fourth path. The signal input end adopts a resistor R21 with 400 ohms to couple out certain radio frequency power for field intensity detection. The larger resistor is used to reduce the loss of the main path so as not to affect the noise figure. The field strength detection is realized by using a first RMS logarithmic detector 22, and the detected analog voltage is subjected to AD conversion and digital processing to generate a control signal of a radio frequency switch 23, so that the control signal can be subjected to circuit gating according to the amplitude of the current signal to complete the power processing of the previous-stage signal. After the processing of the current stage circuit, the minimum input signal is amplified to-90 dBm, the maximum input signal is attenuated to-10 dBm, and the dynamic range is reduced to 80dB from the initial 140 dB.
As shown in fig. 4, the frequency hopping filter and driver amplifier circuit 3 is in a two-stage cascade form, and includes a first stage frequency hopping filter 31 and a second stage frequency hopping filter 33 connected in sequence, and a first stage 15-20 dB driver amplifier 32 interposed between the first stage frequency hopping filter 31 and the second stage frequency hopping filter 33.
The key parts of the VHF rf receiver front-end are a large dynamic range low noise amplifier and a frequency hopping filter. The frequency hopping filter realizes the quick change of the center frequency of the filter, and the core is achieved by continuously and quickly changing or changing all or part of parameters of the band-pass filter by using a switch, the utility model discloses select digital tuning filter scheme. The single-stage frequency hopping filter is inhibited by 25-30 dB at 3% out-of-band, and in order to ensure 50dB out-of-band inhibition, a two-stage cascade form is adopted. Because the insertion loss of the frequency hopping filter is large, and the loss of the rear-stage frequency converter is also large, a first-stage 15-20 dB driving amplifier is inserted between the two stages of frequency hopping filters to ensure the noise coefficient of the system.
The first-stage frequency conversion of this embodiment adopts a high local oscillator up-conversion scheme, the first-time frequency conversion circuit 4 circuit up-converts 30-88 MHz to 270MHz, a local oscillator frequency range is 300-358 MHz, an image frequency range is 570-628 MHz, and a filter with a frequency band of 30-88 MHz easily filters out the image frequency.
An intermediate frequency filtering and amplifying circuit 5 is arranged after the first frequency conversion circuit 4, as shown in fig. 5, and includes a first narrow band filter 51, a resistor R53, a second RMS logarithmic detector 54, a first-stage automatic gain controller 52, and a first driving amplifier 53;
the 270MHz intermediate frequency signal output by the first frequency conversion circuit 4 is filtered by the first narrow band filter 51, amplified by the first automatic gain controller 52, and amplified and output by the first driving amplifier 53; the automatic gain control of the first automatic gain controller 52 adopts a feedforward mode, the output of the first narrow-band filter 51 is coupled out a part of power by a resistor R53 and is connected with the second RMS logarithmic detector 54, and the analog voltage detected by the second RMS logarithmic detector 54 is subjected to AD conversion and digital processing and then controls the first automatic gain controller 52 to complete gain adjustment.
The 270MHz signal after up-conversion by a local oscillator is called an intermediate frequency, and after frequency conversion, the signal should be filtered by the first narrow band filter 51 to filter out rf leakage, local oscillator leakage and other high-order mixing components. The first narrow band filter 51 is followed by a first automatic gain controller 52 with a dynamic range of 40 dB. The automatic gain control of the first automatic gain controller 52 adopts a feedforward mode, firstly a part of power is coupled out by a 400-ohm resistor R53 for field intensity detection, the field intensity detection is realized by adopting a second RMS logarithmic detector 54, the detected analog voltage is subjected to AD conversion and digital processing and then controls a variable gain amplifier to complete gain adjustment, and the automatic gain rear stage is cascaded with the first driving amplifier 51 to ensure the overall gain of the link. The dynamic range is reduced to 40dB from 80dB after passing through the circuit module.
The second frequency conversion circuit 6 for realizing the second-stage frequency conversion is down-conversion, and adopts a high local oscillator scheme to down-convert a first 270MHz intermediate frequency to an intermediate frequency of 21.4MHz, a second local oscillator frequency is 291.4MHz, and an image frequency is 312.8MHz, so that the first frequency conversion circuit and the second frequency conversion circuit are easily filtered by using a narrow-band filter.
The intermediate frequency filtering and amplifying circuit 7 is similar to an intermediate frequency filtering and amplifying circuit 5 except that the control manner of the second automatic gain controller 72 is different therefrom, as shown in fig. 6, the intermediate frequency filtering and amplifying circuit 7 includes a second narrow band filter 71, a second automatic gain controller 72 and a second driver amplifier 75 as in the case of the intermediate frequency filtering and amplifying circuit 5; the intermediate frequency signal is amplified in two stages by the second automatic gain controller 72 and the second driver amplifier 75 and then output.
Except that the second automatic gain controller 72 performs power control of the gain control box in a combined manner of a feed-forward circuit and a feedback circuit; the feed-forward circuit performs field strength detection before the second automatic gain controller 72, and the feedback circuit performs field strength detection after the second automatic gain controller 72; the feed forward circuit includes resistor R73 and third RMS log detector 74; the output of the second secondary frequency conversion circuit 6 is a middle frequency signal which is coupled out a part of power by a resistor R73 and is connected with a third RMS logarithmic detector 74; the feedback circuit comprises a resistor R76 and a fourth RMS log detector 77; the intermediate frequency signal output by the second driver amplifier 75 is coupled out a part of power by a resistor R76 and then connected to the fourth RMS logarithmic detector 77; the analog voltages detected by the third RMS logarithmic detector 74 and the fourth RMS logarithmic detector 77 are sent to the CPLD processor through AD conversion, calculated through a gain and power algorithm, and then subjected to DA conversion, thereby controlling the second automatic gain controller 72 to complete dual adjustment of gain and amplitude, and simultaneously realizing AGC and ALC control.
Specifically, as shown in fig. 6, the intermediate frequency filtering and amplifying circuit is configured to filter the intermediate frequency of 21.4MHz by a second narrow band filter 71, so as to filter out rf leakage, local oscillator leakage, and other high-order mixing components. A first-stage automatic gain control is arranged behind the filter, the dynamic range of the automatic gain control is 30dB, and the automatic gain control adopts a feedforward and feedback comprehensive mode to carry out power control on a gain control box. The feedforward is carried out the field intensity detection before the variable gain amplifier, and the feedback is carried out the field intensity detection after the variable gain amplifier, the field intensity detection is realized by the RMS logarithmic detector, the detected analog voltage is sent to the CPLD processor through AD conversion, and is converted by DA after being calculated by the gain and power algorithm, thereby controlling the variable gain amplifier to finish the double adjustment of gain and amplitude, and simultaneously realizing the AGC and ALC control functions. The dynamic range is reduced from 40dB to 10dB through the circuit module, and the final intermediate frequency output power range is controlled to be-5 dBm, so that the demodulation of the circuit module is facilitated.
The functions of field intensity detection, radio frequency switch control, gain control and the like of the VHF receiver are realized by the CPLD. The link has four field intensity detections, analog voltage output by the logarithmic detector is subjected to AD conversion and then is sent to the CPLD for processing, and a control signal (general IO) of the radio frequency switch and a control signal (analog voltage realized by DA conversion driven by the CPLD) of the variable gain amplifier are generated after calculation, and meanwhile, address control of the frequency hopping filter is also driven by the general IO of the CPLD. The design block diagram of the digital control part is shown in FIG. 7.
Each stage of local oscillator is generated by a phase-locked loop (PLL), in this embodiment, a PLL chip with a dual-output feature is used, and each chip can independently output two local oscillator signals. The locking time of the frequency sweeping source is less than 100us, and the phase-locked loops all refer to 100MHz external supply crystal oscillator signals.
In the embodiment, the VHF receiver adopts a power supply voltage of 9-18V, the power supply management component realizes the voltage conversion of a functional circuit, and a DCDC voltage stabilizing circuit with high efficiency and large current and an LDO linear voltage regulator with high common mode rejection ratio are selected for ensuring the power supply efficiency. In order to reduce electromagnetic interference in the module, the power supply adopts sub-modules for power supply, namely, a radio frequency circuit and a digital processing assembly are respectively in a power supply mode. The circuit has a temperature monitoring function, can feed back the current working temperature in real time, and carries out gain temperature calibration on each temperature so as to achieve higher temperature stability. The module function detection circuit can also monitor the working states of each power supply, each frequency source and each digital circuit, and a user can conveniently master the current state of the system.
The design method of the 1-40 GHz full-band beacon receiver is similar to that of a common radio frequency receiver, the radio frequency is reduced to the intermediate frequency by adopting a single-stage or multi-stage down-conversion mode, the related circuit modules comprise low-noise amplifiers, multi-stage down-conversion, segmented filtering, frequency synthesizers and other circuit modules, and the circuit technologies of radio frequency, microelectronics, analog circuits, digital circuits and the like are integrated.
In this embodiment, consider heat dissipation and the miniaturized requirement of structure, the structure adopts integration box body design, and radio frequency, intermediate frequency and digital processing circuit adopt lumped element to build, and wherein power and digital circuit adopt a main printed circuit board to realize, realize power supply and control to analog circuit through the pin header. The box body of the beacon receiver is made of a metal material with good corrosion resistance, a non-mildew and ageing-resistant non-metal material is selected, the whole beacon receiver is designed in a watertight and sealed three-proofing mode, the outer surface of the beacon receiver is coated with acrylic paint and polyurethane paint in a protective mode, and the environmental adaptability capabilities of the beacon receiver, such as water resistance, moisture resistance, salt mist resistance, mildew resistance, corrosion resistance and the like, of the beacon receiver are improved. In order to ensure the electromagnetic compatibility of the module, the inside of the circuit effectively shields interference sources such as radio frequency and switch circuits, and measures such as electromagnetic sealing gaskets are used at seams of the module, so that the shielding requirement of the system is met.
The radio station receiver designed by the embodiment has the following characteristics: (1) the gain is high, and the lowest weak signal of-120 dBm can be amplified to-20 dBm; (2) the dynamic range is high, signals of 20dBm can be received maximally, and the circuit compression does not exceed 1 dB; (3) high selectivity, filtering out-of-band signals by adopting a combination of a band filter, an image frequency filter, a frequency hopping filter and the like, and extracting useful signals from noise and interference; (4) the full digital high-speed control can realize automatic gain control at high speed without inertia.
The VHF microwave frequency hopping radio receiver of the embodiment can realize low-noise receiving and down-conversion of VHF radio frequency signals with large dynamic range. The utility model discloses the applied frequency channel is 30 ~ 88MHz, and noise figure is less than 4dB, and dynamic range exceeds 140dB, and output intermediate frequency power is-5 ~ 5 dBm. The circuit control part adopts a high-speed digital chip, can adaptively adjust the gain of the amplifying circuit to adapt to the amplitude change of an input signal, and has the advantages of high-speed locking, no saturation and the like compared with the traditional automatic gain control. The utility model has the characteristics of compact structure, miniaturization, with low costs etc, extensively use in fields such as emergency rescue and relief work, news interview, scientific investigation adventure, policeman and military affairs are emergent and special communication, have more extensive application prospect.
Claims (7)
1. A VHF microwave frequency hopping radio receiver is characterized in that a front low-noise amplification and gain adjustment circuit (2) is sequentially connected from a radio frequency receiving antenna; a frequency hopping filtering and driving amplifying circuit (3); a first secondary frequency conversion circuit (4); an intermediate frequency filtering and amplifying circuit (5); a second secondary frequency conversion circuit (6); an intermediate frequency filtering and amplifying circuit (7); meanwhile, a frequency synthesizer for providing local oscillation frequency signals for the first frequency conversion circuit (4) and the second frequency conversion circuit (6) is integrated; the method is characterized in that: the frequency hopping filtering and driving amplifying circuit (3) adopts a two-stage cascade form and comprises a first-stage frequency hopping filter (31), a second-stage frequency hopping filter (33) and a first-stage 15-20 dB driving amplifier (32) which is arranged between the first-stage frequency hopping filter (31) and the second-stage frequency hopping filter (33) and is inserted.
2. A VHF microwave frequency hopping radio receiver according to claim 1, wherein: a front-end high-power protection circuit (1) is also arranged between the preposed low-noise amplification and gain adjustment circuit (2) and the antenna; the front-end high-power protection circuit (1) comprises a limiting circuit and a band filter (15); the amplitude limiting circuit limits the amplitude of a large signal received by the antenna to the same amplitude and then is connected with a 30-88 MHz frequency band filter (15) for suppressing out-of-band interference signals.
3. A VHF microwave frequency hopping radio receiver according to claim 2, wherein: the amplitude limiting circuit comprises a diode D11, a diode D12, a diode D13, a diode D14 and a Zener diode D10; the antenna is respectively connected with the P pole of the diode D11 and the N pole of the diode D14, the N pole of the diode D11 is connected with the N pole of the diode D12, the P pole of the diode D12 is grounded, the P pole of the diode D14 is connected with the P pole of the diode D13, the N pole of the diode D13 is grounded, the N pole of the zener diode D10 is connected with the common end connected with the N pole of the diode D11 and the N pole of the diode D12, and the P pole of the zener diode D10 is connected with the common end connected with the P pole of the diode D13 and the P pole of the diode D14.
4. A VHF microwave frequency hopping radio receiver according to claim 1, wherein: the preposed low-noise amplification and gain adjustment circuit (2) comprises a first path of 30dB attenuator (24), a second path of 10dB attenuator (25), a third path of 20dB gain conventional drive amplifier (26) and a fourth path of amplification and gain channel consisting of a 30dB gain low-noise amplifier (27); a one-out-of-four radio frequency switch (23) arranged in front of and behind the four amplifying and gain channels; a first RMS logarithmic detector (22); a resistor R21; an AD converter;
the signal input end is coupled out by a resistor R21 and connected with a first RMS logarithmic detector (22), the output of the first RMS logarithmic detector (22) is connected with an AD converter to generate a control signal of a radio frequency switch (23), and one path can be selected from four paths of amplification and gain paths according to the amplitude of the current signal.
5. A VHF microwave frequency hopping radio receiver according to claim 1, wherein: the intermediate frequency filtering and amplifying circuit (5) is arranged behind the first frequency conversion circuit (4) and comprises a first narrow-band filter filtering (51), a resistor R53, a second RMS logarithmic detector (54), a first-stage automatic gain controller (52) and a first driving amplifier (53);
an intermediate frequency signal output by the first frequency conversion circuit (4) is filtered by a first narrow-band filter (51), amplified by a first automatic gain controller (52) and amplified and output by a first drive amplifier (53); the automatic gain control of the first automatic gain controller (52) adopts a feedforward mode, the output of the first narrow-band filter (51) is coupled out a part of power by a resistor R53 and is connected with a second RMS logarithmic detector (54), and the analog voltage detected by the second RMS logarithmic detector (54) is subjected to AD conversion and digital processing and then controls the first automatic gain controller (52) to finish gain adjustment.
6. A VHF microwave frequency hopping radio receiver according to claim 1, wherein: the second secondary frequency conversion circuit (6) outputs an intermediate frequency signal, the intermediate frequency signal is processed by an intermediate frequency filtering and amplifying circuit (7), and the intermediate frequency filtering and amplifying circuit (7) comprises a second narrow-band filter (71), a second automatic gain controller (72) and a second driving amplifier (75); the intermediate frequency signal is output after being amplified in two stages by a second automatic gain controller (72) and a second driving amplifier (75);
the second automatic gain controller (72) adopts a feedforward circuit and a feedback circuit integrated mode to carry out power control on the gain control box; the feedforward circuit detects the field intensity before the second automatic gain controller (72), and the feedback circuit detects the field intensity after the second automatic gain controller (72);
the feed forward circuit comprises a resistor R73 and a third RMS log detector (74); the output of the second secondary frequency conversion circuit (6) is a medium-frequency signal, a part of power is coupled out by a resistor R73 and is connected with a third RMS logarithmic detector (74);
the feedback circuit comprises a resistor R76 and a fourth RMS logarithmic detector (77); the intermediate frequency signal output by the second driving amplifier (75) is coupled out of a part of power by a resistor R76 and is connected with a fourth RMS logarithmic detector (77);
analog voltages detected by the third RMS logarithmic detector (74) and the fourth RMS logarithmic detector (77) are sent to the CPLD processor through AD conversion, and are calculated through a gain and power algorithm and then are subjected to DA conversion, so that the second automatic gain controller (72) is controlled to complete double adjustment of gain and amplitude, and AGC and ALC control are realized at the same time.
7. The VHF microwave frequency hopping station receiver according to any one of claims 1 to 6, wherein: and an online monitoring module is also arranged for carrying out temperature detection, temperature calibration and circuit state monitoring.
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CN110289876A (en) * | 2019-07-25 | 2019-09-27 | 广东圣大电子有限公司 | A kind of VHF microwave frequency hopping radio set receiver |
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CN110289876A (en) * | 2019-07-25 | 2019-09-27 | 广东圣大电子有限公司 | A kind of VHF microwave frequency hopping radio set receiver |
CN110289876B (en) * | 2019-07-25 | 2024-04-19 | 广东圣大电子有限公司 | VHF microwave frequency hopping radio receiver |
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