A kind of directionless beacon receiver based on DDS
Technical field
The utility model relates to the receiver of directionless beacon (NDB) signal in the aircraft landing system, and is particularly a kind of based on Direct Digital frequency synthesis (Direct Digital Synthesis, DDS) the directionless beacon receiver of technology.
Background technology
Directionless beacon receiver receives directionless beacon signal, and for the relative bearing of airborne radio direction finder mensuration aircraft and directionless Radio Beacon, thereby vector aircraft flies, goes home and approach along prebriefed pattern.Directionless beacon receiver carries out difference frequency with radiofrequency signal and the local oscillated signal that antenna receives, and obtains the intermediate-freuqncy signal of fixed-frequency, passes through intermediate frequency filtering, amplification and detection again, obtains directionless beacon signal.Directionless beacon receiver is by regulating the directionless beacon emissions signal frequency that the local oscillated signal FREQUENCY CONTROL receives.Present directionless beacon receiver produces local oscillated signal based on LC oscillator or phase-locked loop (PLL) mostly.Based on the directionless beacon receiver of LC oscillator, this receiver is controlled the frequency of the directionless beacon signal that receives, but can't be realized the frequency step adjusting by the output frequency of the doubly-linked capacitor change local oscillated signal of adjusting connecting shaft.Based on the directionless beacon receiver of phase-locked loop, the local oscillated signal frequency resolution of generation is low, and frequency inverted speed is slower, influences the receiving ability of receiver.
Summary of the invention
In view of the deficiency that prior art exists, the utility model provides a kind of directionless beacon receiver based on DDS.Advantages such as the DDS technology is to produce multiple frequency output with digital control method by a reference frequency source, and it has output frequency resolution rate height, the output frequency conversion speed is fast, tuning range big, control is convenient.
The technical scheme that its technical problem that solves the utility model adopts is: a kind of directionless beacon receiver based on DDS, form by antenna 1, low noise amplifier 2, frequency mixer 3, intermediate-frequency filter 4, intermediate frequency amplifier 5, wave detector 6, crystal oscillator 7, DDS chip 8, button 9, single-chip microcomputer 10; Single-chip microcomputer 10 is according to the operation of button 9, and control DDS chip 8 produces the local oscillated signal of corresponding frequencies; After antenna 1 receives radiofrequency signal, by low noise amplifier 2, with local oscillated signal input mixer 3, these two signals are down-converted to the intermediate-freuqncy signal that frequency is 4.4MHz in frequency mixer 3, this intermediate-freuqncy signal is amplified and wave detector 6 detections through intermediate-frequency filter 4 filtering, intermediate frequency amplifier 5, obtains directionless beacon signal.
The beneficial effects of the utility model are, local oscillated signal frequency resolution height, frequency inverted speed are fast, receive that the stepping of directionless beacon signal frequency adjustment is little, control is flexible, can improve the overall performance of directionless beacon receiver.
Description of drawings
Fig. 1 is the theory diagram of a kind of directionless beacon receiver based on DDS of the utility model.
Embodiment
The embodiment of a kind of directionless beacon receiver based on DDS that the utility model is provided below in conjunction with accompanying drawing elaborates.
Referring to Fig. 1, a kind of directionless beacon receiver based on DDS is made up of antenna 1, low noise amplifier 2, frequency mixer 3, intermediate-frequency filter 4, intermediate frequency amplifier 5, wave detector 6, crystal oscillator 7, DDS chip 8, button 9, single-chip microcomputer 10.
In the utility model, the signal range of receiving is 100KHz ~ 1MHz, can change the receive frequency of directionless Radio Beacon with the stepping of 1Hz, 10 Hz, 100Hz and 1KHz by the adjusting of button 9, single-chip microcomputer 10 adopts the C8051F310 of Silicon Laboratories company, DDS chip 8 adopts the AD9834 of ADI company, reference frequency is the crystal oscillator of 50MHz, and the intermediate-freuqncy signal frequency is 4.4MHz.
During concrete enforcement, the user operates button, and the operation of 10 pairs of buttons 9 of single-chip microcomputer is deciphered, and obtains the correspondent frequency control word and sends into DDS chip 8, and DDS chip 8 produces the local oscillated signal of corresponding frequencies thus; The radiofrequency signal that receives from antenna 1 adds frequency mixer 3 through the amplification of low noise amplifier 2 with local oscillated signal, and these two signals are down-converted to the intermediate-freuqncy signal that frequency is 4.4MHz in frequency mixer; After the detection of the amplification of the filtering of intermediate-frequency filter 4, intermediate frequency amplifier 5 and wave detector 6, obtain directionless beacon signal again.