The receiver of signals of satellite radio navigation systems "navstar and glonass

 

The proposed receiver refers to satellite navigation and can be used on moving objects, such as cash machines for primary processing of information coming from two mutually asynchronous satellite radionavigation systems "NAVSTAR and GLONASS. An object of the invention is to increase the selectivity and noise immunity of the receiver by suppressing spurious signals (noise) received by the mirror and Raman channels. The receiver includes an antenna, an input feeder, a broadband filter preselector, the first input of the amplifier, the first band-pass filter, the second low noise amplifier, a first mixer, frequency synthesizer, the reference OCXO, the second bandpass filter, the first intermediate frequency amplifier, the block of complex frequency conversion, block automatic gain control, the second mixer, the third band-pass filter, a second intermediate frequency amplifier, the correlator, the threshold block and key. 2 Il.

The proposed receiver refers to satellite navigation and can be used on moving objects, such as incestors the radionavigation systems “NAVSTAR and GLONASS.

Known receivers of signals of satellite radio navigation systems (RF patent No. 2.110.149, N 04 1/06, 1993; Bells Y. D., Solochek L. K. State and prospects of development of equipment linear paths receivers and exciters transmitters. -Telecommunications, 1993, No. 1, S. 34; Abrosimov Century. And. etc. the use of the Navstar system for determining the angular orientation of the objects. Foreign electronics, 1989, No. 1, S. 49; Network satellite navigation system. Ed. by B. C. Shebshaevich. M, 1993; Mishchenko, I. N., Novels of L. M. New developments of satellite navigation systems. Foreign electronics, 1989, No. 1, S. 68-82, etc.).

Known receivers closest to the proposed is a Receiver of signals of satellite radio navigation systems” (patent RF №2.110.149, N 04 1/06, 1993), which is selected as a prototype.

Using the specified receiver can simultaneously receive and process the signals of space-based radio navigation systems “NAVSTAR and GLONASS without duplication of receiving channels, i.e. using a single receive path. In addition, by reducing the group delay time in signal transmission systems “NAVSTAR and GLONASS increase accuracy characteristics Phnom receiver made according to the superheterodyne circuit, in which the same value of the intermediate frequency Wnp may be obtained by receiving signals on two frequencies Wc and W, i.e.

Wnp=Wc-W1and Wnp-W1-W1.

Therefore, if the frequency W to take over the main channel, along with it will be a mirror of the receive channel frequency W1which differs from the frequency W on 2Wnp and is symmetrical (mirrored) relative to the frequency W1lo (Fig.2). Conversion on the image receiving channel is the same conversion factor of the CRC, as the main channel, so it is most significantly affect the selectivity and robustness of the receiver.

In addition to the mirror, there are other additional (Raman) receiving channels. In General, any fluid channel reception occurs when the condition

Wnp=|±mWi±nW1|,

where Wi - frequency of the i-th Raman receiving channel;

m, n, i is a positive integer.

The most harmful combination receiving channels are channels formed by the interaction of the carrier frequency of the received signal with harmonics of the lo frequency of small order (second, third, and so on), as sensitivity is when m=1 and n=2 correspond to frequencies

W to1=2W1-Wnp and W to2=2W1+Wnp.

The presence of false signals (interference), taken in the mirror and Raman channels, leads to lower selectivity and noise immunity of the receiver.

An object of the invention is to increase the selectivity and noise immunity of the receiver by suppressing spurious signals (noise) received by the mirror and Raman channels.

The problem is solved in that the receiver of signals of satellite radio navigation systems containing series-connected antenna, the input feeder, a broadband filter preselector, the first low noise amplifier, the first band-pass filter, the second low noise amplifier, a first mixer, the second input is via a frequency synthesizer connected to the output of the reference temperature-controlled generator, the second band-pass filter and the first intermediate frequency amplifier, while the second and third outputs of the frequency synthesizer connected respectively to first and second inputs of the block of the complex signal conversion, the output of automatic gain control is connected both to the second input of the first amplifier intermediate frequency, the first and second malosetti, the correlator threshold block and key, and to the output of the second low-noise amplifier connected in series to the second mixer, a second input connected to the fourth output of the frequency synthesizer, the third band-pass filter, a second intermediate frequency amplifier, a second input connected to the output of automatic gain control, the correlator, a second input connected to the output of the first intermediate frequency amplifier, a threshold block and the key, a second input connected to the output of the first intermediate frequency amplifier, and the output is connected to the information input unit of the complex signal conversion and block automatic gain control.

Structural diagram of the proposed receiver is shown in Fig.1. Frequency chart explaining the reason for the formation of additional receiving channels is shown in Fig.2.

The receiver of signals of satellite radio navigation systems “NAVSTAR and GLONASS contains consistently included antenna input feeder 1, a broadband filter preselector 2, the first low noise amplifier 3, the first band-pass filter 4, the second low noise amplifier 5, the first mixer 6, the second input is through the synth h is l 10 intermediate frequency, sequentially connected to the output of the second low-noise amplifier 5, the second mixer 13, a second input connected to the fourth output of the frequency synthesizer, the third band-pass filter 14, a second amplifier 15 intermediate frequency, the correlator 16, a second input connected to the output of the first amplifier 10 intermediate frequency, a threshold unit 17 and the key 18, a second input connected to the output of the amplifier 10 intermediate frequency, and the output is connected to the information input unit 11 integrated signal conversion unit 12 automatic gain control. Thus the output of block 12 automatic gain control is connected both to a second input of the first 3 and second 5 low noise amplifiers, the first 10 and second 15 intermediate frequency amplifiers.

The proposed receiver operates as follows.

The input of receiver antenna receives signals simultaneously spacecraft two satellite navigation systems “NAVSTAR and GLONASS SLthat dual-band receive frequency L1and L2have

Sj·L1(t)=Pj(t)·Dj(t)·Cos(Wj·L1·t+jL1),

Sj·L2(t)=Pj

Dj(t) is the navigation message of the j-th KA;

Wj·L1, Wj·L2- carrier frequencies in the range of L1and L2from the j-th spacecraft;

j·L1,j·L2- the initial phase of the received signals.

Amplitude-frequency response of the receive path is determined by the spectrum of frequencies of the received signals. Range of signals KA GPS NAVSTAR” when working on the code of General application With the/And is (1574,42-1594,24) MHz, and the spectrum signals of the AC system “GLONASS” when working on C/a and P codes is (1602-1620) MHz.

This means that the total bandwidth of the received signals is equal to

1574,42W1620,6 MHz,

i.e., occupied bandwidthW is 50 MHz.

Accept FMN-signals from the antenna are received in the input feeder 1, which is a quarter-wave closed on one side segment of the coaxial line and is used to negotiate parameters of the antenna and input circuits of the receiver. From the output of the feeder 1 QPSK signals fed to the input of the broadband filter preselector 2, which serves to ogran the risk lines, implements elliptic bandpass filter kawara 5-th order. Broadband filter preselector 2 has an important advantage, namely almost linear phase in the passband of the filter, which is a big advantage when working with complex photomanipulating the signals received from the satellites. This leads, for example, to the fact that the filter preselector 2 has the same linear group delayin a bandwidth equal to about 2.5 NS. This implementation leads to the fact that there is no need to use a special calibrator to ensure equal group delay timefor all of the signals received from the SPACECRAFT.

From the output of the filter preselector 2 signal is fed to the input of a low noise amplifier 3, the output of which is connected to the input of bandpass filter 4, the output of which is fed to the input of the second low-noise amplifier 5.

Band-pass filter 4 is designed to eliminate any ripple in the band boom broadband filter preselector 2, and the junction between the low-noise amplifiers 3 and 5. A major increase in receive path provides a low noise adding to the existing amplifiers 3 and 5: the gain of 35dB, the range of acceptable frequencies 1-8 GHz with uneven amplitude-frequency characteristics 1 dB and the noise figure of 1.1 dB.

Further, the outputs of the second low-noise amplifier 5 is fed to the first inputs of the mixers 6 and 13, the second inputs of which are served voltage from the first and fourth outputs of the synthesizer 7 frequencies. Moreover, the frequency of these voltages separated by twice the value of the intermediate frequency

W2-W1-2Wnp

and symmetric with respect to the selected frequency W main channel

W-W1=W2-W=Wnp.

This circumstance leads to a doubling of the number of receiving channels (Fig.2), but creates favorable conditions for their suppression using correlation processing of the received signals. The outputs of the mixers 6 and 13 are connected to bandpass filters 9 and 14, respectively, each of which consists of two cascaded filter of the third order Bessel linear phase-frequency characteristic configured to frequency signals spacecraft system GPS NAVSTAR” (133-137 MHz) and system “GLONASS” (157-181 MHz), thereby processing the input information in a wide band of frequencies. The outputs of bandpass filters 9 and 14 are connected to soo the level of the constant gain within the specified limits used unit 12 automatic gain control, covering low-noise amplifiers 3 and 5, the amplifiers 10 and 15 intermediate frequency.

The voltage outputs of the amplifiers 10 and 15 intermediate frequency is fed to two inputs of the correlator 16, the output of which is formed of the correlation function R(). The latter is compared with the threshold level Vn threshold in block 17. Threshold voltage Vn exceeded only at the maximum value of the correlation function Rmax(). Since the voltage outputs of amplifiers 5 and 10 intermediate frequency formed from one and the same FMN-signal received through the main channel at the frequency Wc (Fig.2), between these voltages, there is a strong correlation, the correlation function reaches its maximum value Rmax(), which exceeds the threshold level Vn. It should be noted that the correlation function QPSK signal has a remarkable property: the high level of the main lobe and low side lobes. If the threshold level Vnop threshold in block 17 is formed by a DC voltage is supplied to the control input of the key 18 and opens it. In the initial state, the key 18 is always closed.

Prey the input unit 11 integrated signal, which implements quadrature processing of input information by supplying to the control inputs of the given node rectangular pulses shifted by a quarter period, while the outputs of the J1I , J2produces sine, and the outputs Q1, Q2- cosine component of the input information signal.

The above-described operation of the receiver corresponds to the case of reception of QPSK signals in the main channel at the frequency Wc (Fig.2).

If a false signal (interferer) is taken by the first image channel frequency W1then the output of the mixers 6 and 13 are formed of the voltage following frequencies:

W11=W1-W1=Wnp,

W12-W2-W1-3Wnp,

where the first index indicates the channel number of which is a false signal (interferer);

the second index denotes the frequencies involved in the conversion of the frequency of the received false signal (interference).

However, only the voltage with a frequency of W11falls within the bandwidth of the amplifier 10 intermediate frequency. The output voltage of the correlator 16 in this case is zero, the key 18 is not opened and a false signal (interferer) taken by the first image channel frequency W1, pojavlaetsa mixers 6 and 13 are formed of the voltage following frequencies:

W22-W2-W2=Wnp,

W21=W2-W1=3Wnp.

However, only the voltage with a frequency of W22falls within the bandwidth of the amplifier 15 intermediate frequency. The output voltage of the correlator 16 is also zero, the key 18 is not opened and a false signal (interferer) taken by the second image channel frequency W2suppressed.

For a similar reason are suppressed and other interfering signals (noise) taken by the first Raman channel at frequency W to1or on the second Raman channel at frequency W to2or any other Raman channel W.

If the interfering signals (noise) are taken, for example, by the first and second image channel at frequencies W1and W2then from the outputs of the mixers 6 and 13 are formed of the voltage following frequencies:

W11=W1-W1=Wnp,

W12=W2-W1=3Wnp,

W22=W2-W2=Wnp,

W21=W2-W1=3Wnp.

When this voltage with frequencies W11and W12fall within the bandwidth of the amplifiers 10 and 15 intermediate frequency, respectively. However, the key 18 in this case also does not open. This is because false Signa communication. The correlation function reaches a maximum value and does not exceed the threshold level Vnop, the key 18 is not opened and the interfering signals (noise) taken simultaneously by the first and second image channel at frequencies W1and W2are suppressed.

For a similar reason suppressed and false signals (interference) taken simultaneously by two or more other channels.

In the receiver achieved the following benefits:

a) providing the possibility of receiving and processing signals from two satellite navigation systems “NAVSTAR and GLONASS with one reception path, and therefore, a significant simplification of the receiving equipment;

b) implementation of the receiver can be implemented using one conversion to an intermediate frequency for further digital processing of signals received from the SPACECRAFT satellite radio navigation systems, and thereby ensures high reliability and accuracy.

d) the receiver provides a higher fidelity input information through the use of filters with elliptical approximation that implements the linear phase-frequency characteristic and as a consequence the same and minimum vu with prototype and other technical solutions for a similar purpose provides increased selectivity and noise signals of satellite radio navigation systems “NAVSTAR and GLONASS. This is achieved by correlation processing of the received signals using the remarkable properties of the correlation function phase-shift keyed signals, which has a very high level of the main lobe and low side lobes.

Claims

The receiver of signals of satellite radio navigation systems containing series-connected antenna, the input feeder, a broadband filter preselector, the first low noise amplifier, the first band-pass filter, the second low noise amplifier, a first mixer, the second input is via a frequency synthesizer connected to the output of the reference temperature-controlled generator, the second band-pass filter and the first intermediate frequency amplifier, while the second and third outputs of the frequency synthesizer connected respectively to first and second inputs of the block of the complex signal conversion, the output of automatic gain control is connected simultaneously with the second inputs of the first intermediate frequency amplifier, first and second low noise amplifiers, characterized in that he comes with a second mixer, a third bandpass filter, a second intermediate frequency amplifier, clucene the second mixer, the second input of which is connected to the fourth output of the frequency synthesizer, the third band-pass filter, a second intermediate frequency amplifier, a second input connected to the output of automatic gain control, the correlator, a second input connected to the output of the first intermediate frequency amplifier, a threshold block and the key, a second input connected to the output of the first intermediate frequency amplifier, and the output is connected to the information input unit of the complex signal conversion and block automatic gain control.

 

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