RU2067770C1 - User set receiver for signals from global satellite navigation systems - Google Patents

Abstract

FIELD: radar devices. SUBSTANCE: device has two antennas 1, 7, two preliminary selection filters 2, 6, three low-noise amplifiers 3, 5, 9, one microwave commutator 4, one amplitude clipper 8, three band-pass filters 10, 16, 20, two mixers 11, 12, phase shifter 13, reference frequency lattice generator 14, temperature-stable reference oscillator 15, two intermediate frequency amplifiers 17, 21, two units 18, 22 which controls amplification gain, analog-to-digital converter 19. EFFECT: increased functional capabilities. 4 dwg

Description

 The invention relates to the field of satellite radio navigation and can be used in primary information processing paths of receiver indicators of two mutually synchronized global satellite radio navigation systems (SRNS).

 A known receiver that contains an antenna, a low noise amplifier (LNA), a filter of the first mirror channel (FZK 1), a mixer, a frequency multiplier n times, a filter, a preliminary amplifier of the first intermediate frequency, a filter of the second mirror channel (FZK 2), a second mixer, the second frequency multiplier is a factor of m, the input of which receives a signal from the output of the synthesizer of the exact frequency grid, the second intermediate-frequency amplifier, covered by an automatic gain control (AGC) circuit. This device can only receive signals from only one navigation system (Glonass-type systems or Global Posifionung System-like systems of the Global Navstar positioning system), which is a serious drawback, since it is necessary to duplicate receiver equipment in case of receiving signals from spacecraft (SC) two radio navigation systems. In addition, the use of two frequency multipliers (n and m times, respectively) leads to a significant increase in the phase noise level of the receiving path, which reduces the signal-to-noise ratio at the output of the device and, as a result, the accuracy of the measurement vector of the entire transceiver.

These disadvantages are partially eliminated in the multiplex receiver of Texas Instruments (USA) [2] which includes an antenna, antenna amplifier, frequency selector f _s and f ₂ , converter
L-band frequencies, generator of built-in frequency control f ₁ and f ₂ , frequency synthesizer, correlator and frequency converter, analog-to-digital converter (ADC) and preprocessing device. It should be noted that the structural diagram of the receiver also shows some other blocks that are not components of the receiver itself, but that implement the function of tracking meters and therefore will not be considered here.

The advantage of this device is the ability to work with spacecraft GPS "Navstar" according to the general use code (C / A - code) and high-precision R code for the frequency f ₁ and f ₂ (respectively 1575.42 and 1227.6 MHz). However, the presence of multiplexing reduces the signal-to-noise ratio. The loss in this case is approximately 1.5 dB per channel.

 In addition, the receiver cannot simultaneously provide the reception and processing of signals from two satellite radio navigation systems such as Glonass and GPS type Navstar.

 Closest to the technical essence of the invention is a combined receiver of GPS spacecraft signals Navstar / Glonass, comprising an antenna, a low-noise amplifier, a diplexer, a signal splitter, a reference thermostatically controlled oscillator, a four-channel receiving module of the Glonass system, each of which contains in turn, its own mixer, intermediate frequency amplifier and analog-to-digital converter.

 This construction is due to the fact that each spacecraft of the Glonass system emits a signal to its carrier frequency.

 The device also contains a six-channel receiver module of the Navstar GPS system, which contains a mixer, an intermediate frequency amplifier, and an analog-to-digital converter.

 The advantage of the combined receiver is the ability to work with the signals of two satellite radio navigation systems of the Glonass system and the Navstar system. This ensures the continuity and high accuracy of the measurement of the vector of navigation parameters by the receiver indicators in which this receiver is used.

 However, the prototype device has a number of significant drawbacks, since the ability to work on the signals from spacecraft of two satellite radio navigation systems is achieved due to the two-channel reception equipment separate for each spacecraft system, which leads to a noticeable complication and increase in the mass-dimensional parameters of the receiver.

 In addition, the use in the known prototype device as an analog-to-digital converter (ADC) of a two-way limiter with the subsequent conversion of an analog-digital signal leads to an energy loss of 0.96 dB, and also does not compensate for non-Gaussian interference that occurs, for example, when installing consumer equipment (AP) at highly dynamic facilities (aircraft, helicopters, submarines, etc.).

In the inventive device, the ability to solve the following problems:
the ability to simultaneously receive and process signals from the SRNS Glonass and Navstar spacecraft, which allows for high-speed and high-precision digital processing of spacecraft signals in various classes of SRNS receivers,
to increase the accuracy of the receiver through the use of filters with linear phase-frequency characteristics in the signal processing path of the satellite signals of the Glonass and Navstar systems,
to expand the functionality of the claimed device by introducing a microwave switch that provides work on the internal (built into the receiver-indicator) and external (remote) antennas,
to increase the noise immunity of the receiver to non-Gaussian and impulse noise due to the use of adaptive analog-to-digital converter.

 The indicated advantages of the claimed device over the prototype are achieved due to the fact that the receiver of the consumer equipment signals of global satellite navigation systems containing an antenna, a low-noise amplifier, a mixer, an intermediate frequency amplifier (UHF), a reference thermostatic generator and an analog-to-digital converter, the output of which is the output receiver, additionally introduced a second antenna, the first and second filter preselectors, the second and third low-noise amplifiers, microwave switch, amplitudes first limiter reference frequency grid generator (FSOCH) phase shifter, the first three bandpass filters, a second mixer, the second intermediate-frequency amplifier, first and second automatic gain control units. The output of the first antenna is connected to the input of the first preselector filter, the output connected to the input of the first low-noise amplifier, the output of which is connected to the first input of the microwave switch, the second input of which is connected to the output of the second low-noise amplifier. The input of the second LNA is connected to the output of the second preselector filter, the input connected to the output of the second (external) antenna. The output of the microwave switch is connected to the input of the amplitude limiter connected by the output to the first input of the third low-noise amplifier, the output of which is connected to the input of the first band-pass filter. The output of this filter is connected simultaneously to the first inputs of the first and second mixers, and the input of the second mixer is connected to the output of the phase shifter, the input of which is connected simultaneously to the second input of the first mixer and the first output of the reference frequency shaper (FSOCH). The input of the latter is connected to the output of the reference thermostatically controlled oscillator, and the output of the first mixer is connected to the input of the second bandpass filter connected by the output to the first input of the first intermediate frequency amplifier, the direct output of which is connected simultaneously with the first information input of the analog-to-digital converter and the first block of automatic gain control ( AGC). The output of the first AGC block is simultaneously connected to the second input of the first intermediate frequency amplifier (IFA) and the second input of the third low-noise amplifier (LNA), and the output of the second mixer is connected to the input of the third band-pass filter, which, in turn, is connected to the output from the first input of the second amplifier. The output of the second converter is simultaneously connected to the second information input of the analog-to-digital converter (ADC) and the input of the second AGC block, the output of which is connected to the second input of the second converter, while the inverse output of the first converter is connected to the third information input of the ADC, the inverse output of the second converter is connected to the fourth information input of the ADC. The second output of the FSOC is connected to the control input of the ADC.

 In FIG. 1 shows a functional diagram of a receiver of equipment for consumers of signals from global satellite radio navigation systems; figure 2 is a structural diagram of a former of a grid of reference frequencies; in FIG. 3 is a functional diagram of a frequency divider; FIG. 4 is an embodiment of an analog-to-digital converter assembly.

 According to the invention, the receiver equipment of the consumers of signals of global satellite radio navigation systems (Fig. 1) contains an antenna 1, the output of which is connected to the input of a broadband filter preselector 2, the output connected to the input of the first low-noise amplifier 3, the output connected to the first input of the microwave switch 4. Second the input of the microwave switch 4 is connected to the output of the second low-noise amplifier 5, the input of which is connected to the output of the second broadband filter preselector 6, the input connected to the output of the second (take-out oh) antennas 7. The output of the microwave switch 4 is connected to the input of the amplitude limiter 8, the output of which is connected to the first input of the third low-noise amplifier 9, the output connected to the input of the bandpass filter 10, the output of which is simultaneously connected to the first inputs of the mixers 11 and 12. The second input mixer 12 is connected to the input of the phase shifter 13, the input of which is simultaneously connected to the second input of the mixer 11 and the first output of the driver 14 of the reference frequency grid, the input connected to the output of the reference thermostatically controlled generator 15. The output the mixer 11 is connected to the input of the bandpass filter 16, the output of which is connected to the first input of the intermediate frequency amplifier 17, the direct output of which is connected simultaneously with the input of the automatic gain control unit 18 and the first information input of the analog-to-digital converter 19. The output of the mixer 12 is connected to the input of the bandpass filter 20, connected by the output to the input of the intermediate frequency amplifier 21, the direct output of which is connected simultaneously to the second information input of the ADC 19 and the input of the automatic control unit 22 gain amplification output connected to the second input of the amplifier 21 of the intermediate frequency. The inverse outputs of the amplifiers 17 and 21 of the intermediate frequency are connected respectively to the third and fourth information inputs of the analog-to-digital converter 19, the first fourth outputs of which are the outputs of the receiver. The second output of the shaper 14 of the reference frequency grid is connected to the control input of the analog-to-digital converter 19.

 Shaper 14 of the grid of the reference frequency (Fig.1,2) contains a pulse phase detector 23 and a frequency detector 24, the first inputs of which are interconnected and connected to the output of the reference thermostated generator 15. The outputs of blocks 23 and 24 are connected respectively to the first and second input of the adder 25, the first and second outputs of which are connected respectively to the control inputs of the keys 26 and 27. The second control inputs of the keys 26 and 27 are connected respectively to the positive potential of the supply voltage and zero potential. The outputs of the keys 26 and 27 are interconnected and connected to the input of the low-pass filter 28, thus maintaining a stable output current at the input of the low-pass filter 28. The output of the low-pass filter 28 is connected to the input of a voltage controlled oscillator 29, the output of which is connected simultaneously with blocks 11 and 13, as well as with a multi-stage divider 30, the first output of which is simultaneously connected to the second inputs of blocks 23 and 24, thereby forming a phase-locked loop. The second output of the divider 30 is connected to the control input of the analog-to-digital Converter 19.

 The multi-stage frequency divider 30 (FIGS. 2 and 3) contains a T-trigger 31, the clock input of which is connected to the output of the voltage controlled oscillator 29, and is the output of the multi-stage frequency divider 30. The output of the T-trigger 31 is connected to the synchronization input of the counter-divider 32 (N = 72), the output of which is connected to the second inputs of the pulse phase detector 23 and the frequency detector 24, respectively. In addition, the output of the T-trigger 31 is also connected to the synchronization input of the counter-divider 33 (N = 8), the output connected to the control input of the analog-to-digital Converter 19.

The analog-to-digital converter 19 (FIGS. 1 and 4) includes comparators 34, 35, 36 and 37, integrators 38 and 39, OR 40 and 41 elements. The first input of the comparator 34 is connected to the direct output of the intermediate frequency amplifier 17, the inverse output of the latter is connected to the first input of the comparator 35. The output of the comparator 34 is the first output of the receiver (output I ₁ ), and it is connected to the first input of the OR element 40. The output of the comparator 35 is the second output of the receiver (output I ₂ ), and it is connected to the second input of the OR element 40. The output of the OR element 40 is connected to the integ a rotor 38, the output of which is connected simultaneously with the second inputs of the comparators 34 and 35. The first input of the comparator 36 is connected to the inverse output of the intermediate frequency amplifier 21, the direct output of the block 21 is connected to the first input of the comparator 37. The output of the comparator 36 is the third output of the receiver (output Q ₁ ), and it is connected to the first input of the OR element 41. The output of the comparator 37 is the fourth output of the receiver (output Q ₂ ), at the same time it is connected to the second input of the OR element 41. The output of the OR element 41 is connected to the input of the integrator 39, the output of which the second is connected simultaneously to the second inputs of the comparators 36 and 37. The second output of the driver 14 of the grid of the reference frequencies is connected simultaneously with the third (control) inputs of the comparators 34 37.

(1)
где A(t) флуктуирующая в точке приема амплитуда сигнала КА;
Pi(t) псевдослучайная огибающая сигнала i-го КА0;
Di(t) навигационное сообщение i-го КА;
ω_i несущая частота i-го КА;
t текущее время;
Φ_i начальная фаза несущей i-го КА.The device operates as follows. The receiver antenna receives signals from spacecraft of the Glonass and Navstar satellite radio navigation systems S _i (t), which in the general case have the form

(one)
where A (t) is the amplitude of the spacecraft signal fluctuating at the receiving point;
Pi (t) pseudo-random envelope of the signal of the i-th KA0;
Di (t) navigation message of the i-th spacecraft;
ω _{i is the} carrier frequency of the i-th spacecraft;
t current time;
Φ _{i is the} initial phase of the carrier of the i-th spacecraft.

 The amplitude-frequency characteristic of the receiving path of the claimed device is determined by the frequency spectra of the received signals. The frequency spectrum of the signals of the spacecraft GPS "Navstar" when working with the general application code C / A is (1575.42 1) MHz, and the frequency spectrum of the signals of the spacecraft "Glastass" when working with the codes of low and high accuracy (respectively, PT and VT) is (1602 -1620.6) MHz. This means that the total frequency band of the received signals is equal to 1574.42≅Δf≅1620.6 MHz, i.e. The occupied frequency band Δf f is approximately 50 MHz.

 From the output of the antenna 1, which is built directly into the consumer equipment, the signal is fed to the input of the broadband filter-preselector 2, which serves to limit the frequency band of the received signals in the range 1574.42 1621 MHz. The specified filter, which can be performed, for example, on volume electric resonators, implements the Butterworth or Cauer approximation with a linear phase-frequency characteristic (PFC) in the passband, while the filter order is four. This approach leads to the fact that there is no need to use a special calibrator to ensure minimal non-uniformity of group delay time for spacecraft signals with different carrier frequencies. From the output of filter 2, the signal goes to the input of a low-noise amplifier 3, where the signal is pre-amplified, which then goes to the first input of the microwave switch 4.

 The specified microwave switch, which can be performed, for example, on p-i-n diodes, provides the ability to work on one of the antennas: either internal (built-in consumer equipment) or external (remote). At the same time, the microwave switch 4 is implemented in such a way that when connecting an external antenna, blocks 1, 2 and 3 are turned off and only the external antenna is operated.

 From the output of the remote antenna 7, the signal goes to the input of the broadband filter-preselector 6, the purpose, type and parameters of which are similar to filter 2. From the output of the filter 6, the signal goes to the input of low-noise amplifier 5, the functions of which are similar to the functions of device 3. Low-noise amplifiers 3 and 5 are made based on gallium arsenide transistors with a Schottky barrier. The LNA parameters 3 and 5 are as follows: a gain of 35 dB, a range of received frequencies of 1 8 GHz with uneven amplitude-frequency characteristics of 1 dB and a noise figure of 1.5 dB. The output of the LNA 5 is connected to the second input of the microwave switch 4. The parameters of the microwave switch, made on the basis of pin diodes of type 2A547A, are as follows: allowable working frequency band 0.6 9 GHz, open channel transmittance loss 1.5 dB, standing wave coefficient equal to 1.8.

 Subsequently, the signal from the output of the microwave switch 4 is fed to the input of a two-sided amplitude limiter 8, which is a parametric amplifier and is designed to prevent the excitation of the cascades of the receive-amplifier path in the event of exposure to powerful interference whose spectrum is in the passband of the receiver (for example, global space communications or astrophysical emitters). The loss of net power when using the amplitude limiter 8 does not exceed 0.5 dB in the passband. The signal from the output of the amplitude limiter 8 is fed to the first input of the LNA 9, where further amplification of the received signal occurs. The band-pass filter 10 is designed to eliminate additional ripple in the passband of the broadband filter-selector 2 or 6 (depending on the operating mode).

за счет фазовращателя 13. На выходе смесителей 11 и 12 образуется сигнал разностной частоты f_пр=f_c f_г с образованием в канале блока 11 синфазной (синусной), а в канале блока 12 квадратурной (косинусной) составляющей преобразованного входного сигнала. Выходы смесителей 11 и 12 подключены соответственно к входам полосовых фильтров 16 и 20, которые представляют собой широкополосные фильтры с аппроксимацией Баттерворта и параметрами: частоты среза f₁= 50 кГц, f₂=26 МГц (по уровню 2 дБ), ослабление по частоте 30 кГц равно 45 дБ, а на частоте 28 МГц 90 дБ соответственно. Заметим, что указанная аппроксимация при реализации фильтров 16 и 20, а также реализация балансных смесителей на основе схемы с квазилинейным сдвигом частоты позволяет обеспечить очень малую величину неравномерности группового времени запаздывания Δτ для всех сигналов КА систем "Глонасс" и "Навстар" (примерно 1,5 нс). Такая величина Dt позволяет существенно повысить точностные показатели аппаратуры потребителей в целом.Subsequently, the signal from the output of the band-pass filter 10 is supplied to the first inputs of the mixers 11 and 12, which are made according to the balanced circuit and are quadrature converters of the input complex phase-shifted signal. To this end, blocks 11 and 12 are connected to a local oscillator with a frequency of 1400 MHz (the first output of the former 14 of the grid of reference frequencies) with a phase shift

due to the phase shifter 13. At the output of the mixers 11 and 12, a difference frequency signal f _pr = f _c f _{g is} formed with the formation of a in-phase (sine) channel in the channel of the block 11 and a quadrature (cosine) component of the converted input signal in the channel of the block 12. The outputs of the mixers 11 and 12 are connected respectively to the inputs of the band-pass filters 16 and 20, which are wide-band filters with Butterworth approximation and parameters: cut-off frequencies f ₁ = 50 kHz, f ₂ = 26 MHz (at a level of 2 dB), attenuation at a frequency of 30 kHz is 45 dB, and at a frequency of 28 MHz, 90 dB, respectively. We note that the indicated approximation in the implementation of filters 16 and 20, as well as the implementation of balanced mixers based on a scheme with a quasilinear frequency shift, makes it possible to provide a very small value of the non-uniformity of the group delay time Δτ for all signals of the spacecraft of the Glonass and Navstar systems (approximately 1, 5 ns). Such a value of Dt makes it possible to significantly increase the accuracy indicators of consumer equipment as a whole.

 The output of the bandpass filter 16 is connected to the first input of the intermediate frequency amplifier 17, and the bandpass filter 20 is connected to the first input of the intermediate frequency amplifier 21. Amplifiers 17 and 21 of intermediate frequency are needed to further amplify the input signal.

 To ensure the constant gain within the specified limits, blocks 18 and 22 of automatic gain control are used, and in the common-mode and quadrature channels, a separate AGC block is implemented. The AGC block 18 operating in common mode comprises an intermediate frequency amplifier 17 and a low-noise amplifier 9, and the AGC block 22 an intermediate frequency amplifier 21. The depth of adjustment of the AGC blocks 18 and 22 is 28 dB.

From the direct and inverse outputs of the intermediate frequency amplifier 17, the in-phase component of the input signal is supplied to the first and third information inputs of the analog-to-digital converter 19, and the quadrature component is supplied from the direct and inverse outputs of the amplifier 21 to the second and fourth information inputs of the ADC 19. After the analog-digital the converter at the outputs I ₁ and I _{2 of the} ADC 19 are formed in-phase, respectively, and at the outputs Q ₁ and Q _2, respectively, the quadrature digital components of the input signal of the receiver of the consumer equipment th SRNS.

 The advantage of ADC 19 is the adaptability property, i.e. the threshold voltage levels with which the input signals are compared during digitization are not fixed, but are formed by logical addition by OR and integration. This ADC property allows you to increase or decrease the comparison thresholds depending on the spectral properties of the input signal. Such an implementation significantly increases the noise immunity of the system, for example, when exposed to harmonic (non-Gaussian) or concentrated impulse noise.

Compared with the prototype device [3] in the inventive receiver of the apparatus of consumers of signals from global satellite radio navigation systems, the following advantages are achieved:
the possibility of receiving and processing signals of two satellite radio navigation systems "Glonass" and "Navstar" using one receiving path, i.e. A significant simplification of the equipment was achieved;
due to the use of filters with a linear phase-frequency characteristic, a small value ($ E <=> 1.5 ns) of non-uniformity of group delay time in the entire band of operating frequencies of the spacecraft is ensured, which ensures the precision of measurement of the vector of radio navigation parameters;
the receiver’s functionality has been expanded due to the introduction of an internal (built-in) and external antenna, and the use of a microwave switch makes it possible to automatically switch from an internal antenna to an external antenna when the latter is connected;
the noise immunity of the receiver to non-Gaussian and external noise due to the use of an adaptive analog-to-digital converter is increased.

 Thus, the tasks are solved.

Claims (1)

 A receiver of global satellite radio navigation system signal consumer equipment, comprising an antenna, a low-noise amplifier, a mixer, an intermediate frequency amplifier, a reference thermostated generator and an analog-to-digital converter, the output of which is the output of the receiver, characterized in that the second antenna, the first and second, are additionally introduced into it preselector filters, second and third low-noise amplifiers, microwave (microwave) switch, amplitude limiter, reference clock shaper one, phase shifter, first, second and third bandpass filters, second mixer, second intermediate-frequency amplifier, first and second automatic gain control units, the output of the first antenna is connected to the input of the first preselector filter, the output of which is connected to the input of the first low-noise amplifier, the output of which connected to the first input of the microwave switch, the second input of which is connected to the output of the second low-noise amplifier, the input connected to the output of the second preselector filter, the input of which is connected to the WTO output antenna, the output of the microwave switch is connected to the input of the amplitude limiter connected by the output to the first input of the third low-noise amplifier, the output of which is connected to the input of the first bandpass filter, the output of which is simultaneously connected to the first input of the first and second mixers, the second input of the second mixer is connected to the output phase shifter, the input of which is connected simultaneously with the second input of the first mixer and the first output of the reference frequency driver, the input connected to the output of the reference thermostatically generator, the output of the first mixer is connected to the input of the second bandpass filter, the output of which is connected to the first input of the first intermediate frequency amplifier, the direct output of which is connected simultaneously with the first information input of the analog-to-digital converter and the first block of automatic gain control, the output of which is simultaneously connected to the second the input of the first intermediate frequency amplifier and the third low-noise amplifier, the output of the second mixer is connected to the input of the third band-pass filter, the output to connected to the first input of the second intermediate frequency amplifier, the output of which is simultaneously connected to the second information input of the analog-to-digital converter and the input of the second block of automatic gain control, the output connected to the second input of the second intermediate frequency amplifier, the inverse output of the first intermediate frequency amplifier is connected to the third information the input of the analog-to-digital converter, the inverse output of the second intermediate frequency amplifier is connected to the fourth information nnym input of the analog-digital converter, and a second output reference frequency grid generator is connected to the control input of analog-to-digital converter.

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