Band filter automatic tuning device

FIELD: radio engineering for radio communications and radar systems.

SUBSTANCE: proposed automatically tunable band filter has series-connected limiting amplifier 1, tunable band filter 2 in the form of first series-tuned circuit with capacitor whose value varies depending on voltage applied to control input, first buffer amplifier 3, parametric correcting unit 4 in the form of second series-tuned circuit incorporating variable capacitor, second buffer amplifier 5, first differential unit 6, first amplitude detector 7, first integrating device 9, and subtraction unit 9. Inverting input of subtraction unit 9 is connected to reference-voltage generator 10 and output, to control input of variable capacitors 2 and 4. Automatically tunable band filter also has series-connected second amplitude detector 11, second integrating unit 12, and threshold unit 13. Synchronous operation of this filter during reception and processing of finite-length radio pulses is ensured by synchronizer 14 whose output is connected to units 10, 8, and 12. This automatically tunable band filter also has second differential unit whose input is connected to output of buffer amplifier 3 and output, to second control input of variable capacitor of band filter 2.

EFFECT: enhanced noise immunity due to maintaining device characteristics within wide frequency range.

1 cl, 1 dwg

 

The invention relates to electrical engineering and can be used in radio systems, radar, etc. at the reception and detection of quasi-harmonic signals with unknown carrier frequency.

When building high-quality and robust radio systems, such as navigation, communication and radar systems, one of the major problems is the provision of reliable a posteriori estimates of the values of the carrier frequencies in the distribution and process the signals received on the background noise. There are various methods of building systems for allocation of radio signals from interference and determine estimates of the unknown carrier frequency [1-5]. Both algorithmically and hardware (i.e. shemotehnicheski) in these methods use the principles of narrowband filtering, both adaptive and multi-channel.

As analogues claimed are tracking filters [1], however, their disadvantages are, firstly, not enough high noise immunity due to use of non-linear elements of type frequency detectors, to determine and display frequency shift and the generation of control signals; secondly, a relatively small range of adjustment is determined by the decrease of the magnitude of the control signal when the original frequency the Sam is the properties, excess bandwidth due to the dynamic change of the transmission factor of the bandpass filter in the process of adjustment (adaptation), which also lowers the immunity of such devices.

The prototype, i.e. the closest device to the invention by the technical nature, is the automatic tuning bandpass filter containing the serially connected band pass amplifier-limiter, the input of which is the input of the bandpass filter in the form of the first single series resonant circuit in which the variable capacitor with one output connected to the common wire, and the second output to the output of the bandpass filter, and the first buffer amplifier, connected in series, the first amplitude detector and the first integrating device [6].

The disadvantage of the prototype is the lack of immunity caused by the use of additional test signals, interaction of which with the input signals and changes in the structure of the latter is the formation of control signals for adjustment of the passband of the filter. As with counterparts in the prototype, the magnitude of the control signals depends on the initial detuning and decreases with its increase, and therefore the robustness of the prototype wkhuds what is with the increase in initial detuning from the original resonance frequency of the bandpass filter.

The purpose of the invention is the increased robustness by maintaining characteristics of the device in a wide range of frequency shift.

This objective is achieved in that in the automatic tuning bandpass filter containing the serially connected band pass amplifier-limiter, the input of which is the input of the tunable bandpass filter in the form of the first single series resonant circuit in which the variable capacitor with one output connected to the common wire, and the second output to the output of the bandpass filter, and a buffer amplifier and connected in series to the first amplitude detector and the first integrating device, inserted between the output of the first buffer amplifier and an output device connected in series parametric adjustment device is connected to the common wire of the second single of the series resonant circuit with the second variable capacitor, the second buffer amplifier, the second amplitude detector, the second integrating device and a threshold device, and also introduced the first differentiating device connected between the output of the second buffer amplifier and the first input of the amplitude detector, and entered sequentially connect the data synchronizer, the reference voltage generator and subtractive device, the output of which is connected to control inputs of the adjustable capacitors of the first and second single series resonant circuits respectively tunable bandpass filter and parametric correction device, and a non-inverting second input of subtractive device connected to the output of the second integrating device, and the output of the synchronizer is also connected to the clock inputs of both the first and second integrating device, and a threshold device, when it entered the second differentiating the input device is connected to the output of the first buffer amplifier, and the output to the second control input of the variable capacitor tunable bandpass filter.

The goal of increasing the noise immunity is achieved, firstly, by introducing in the control condition tunable bandpass filter, namely the instantaneous state of the resonant frequency of the filter; secondly, by introducing to compensate for changes in frequency characteristics of the tunable bandpass filter parametric correction, changing synchronously in time with changes in the bandpass filter; thirdly, by introducing a more robust compared to the other pic is the means of linear identification of the frequency detuning using the first differential device.

The use of these essential features in conjunction with the optimal operation of the prototype - integration enables the operation of the automatic tuning bandpass filter with high noise immunity greater range frequency shift than that of the prototype. Introduction feedback on the derivative, as a result of which implemented a non-linear modes of the tunable bandpass filter, automatic instantaneous running condition of the filter under the action of powerful interference, i.e. robustness (insensitivity) to these interferences, which also increases the noise immunity of the device.

As the characteristics of the proposed device are improved in a wider range of frequency reconstructions, the device can also be designated as automatic tunable bandpass filter (PAPF), i.e. also with more compact abbreviation.

The drawing shows a structural diagram of the proposed automatic tuning bandpass filter.

PAPP contains serially connected band pass amplifier-limiter 1, tunable band-pass filter 2, a first series resonant circuit with a capacitor, the capacitance of which varies under the action applied to the control input voltage, the first choice of the buffer amplifier 3, parametric adjustment device 4 in the form of the second series resonant circuit with variable capacitance, the second buffer amplifier 5, a first differentiating unit 6, the first amplitude detector 7, the first integrating device 8, subtractive device 9. The output of subtractive device connected to the control inputs of variable capacitors for tunable bandpass filter 2 and parametric correction device 4, and the second, inverting, input of subtractive device 9 is connected to the output of the reference voltage generator 10. PAPP also contains serially connected second amplitude detector 11, the second integrating device 12 and a threshold device 13 whose output is the output of the entire device. Synchronous operation of PAPP at the reception and processing of radio pulses with a finite duration provides the synchronizer 14, the output of which is connected to the clock inputs of the generator 10, the integrating device 8 and 12, and the threshold device 13. In addition, PAPP includes a second differentiating unit 15, the input of which is connected to the output of the buffer amplifier 3, and the output connected to the second managing input of the variable capacitor bandpass filter 2.

PAPP works as follows.

The input signal in the form additive compounds the noise and radar pulse with constant amplitude, a finite duration and unknown carrier frequency is fed to the input of bandpass amplifier-limiter 1, which is a two-way restriction and the formation of a random process in the form of radio pulses with constant amplitude and random, changing in time full phase containing a monotonic component, due to the unknown, i.e. random, but constant over the observation interval, the carrier frequency of the radar pulse.

The basis of PAPF is tunable band-pass filter 2, made in the form of a single series resonant circuit with a variable capacitor, which has two control inputs for changes in the capacitance. One control input voltage feedback using the second differential device 15 that is proportional to the derivative of the voltage on the variable capacitor. This increased robustness is due to the fact that the presence of large values of the noise component, the spectrum of which coincides with the current setup tunable bandpass filter 2, is not correlated with her derivative of this component changes (reduces) the value of capacitance of the variable capacitor, i.e. instantaneous offset tunable bandpass filter 2 from interference. Thus, when controlling for MF the t derivative is automatically offset from the powerful disturbances spectral components.

Similarly, the process of automatic detuning occurs when the random interference of structurally coincides with the signal, i.e. suppresses it. Only in this case, by reducing the magnitude of the derivative is the instantaneous increase of the capacity, i.e., the current resonant frequency of the tunable bandpass filter 2 is changed (reduced), and band-pass filter is automatically rebuilt from such a powerful noise.

In order for this process occurred when configured on the useful signal band-pass filter is used the second branch of the feedback - feedback control, formed by blocks 4, 5, 6, 7, 8, 9 and 10. However, radiopulse signal with arbitrary carrier frequency, i.e. disordered relative to the resonance frequency of the tunable bandpass filter 2, and accordingly a constant amplitude due to the correction device 4. The adjustment device has an amplitude-frequency characteristic (AFC), the inverse frequency response of tunable bandpass filter 2. This is implemented using the series resonant circuit included in the output of the amplifier operating in the generator mode current. In order for this line was maintained within the required range of frequency adjustment, the adjustment of the mouth of austo is parametric, namely, it is the capacity of the variable capacitor when the reconstruction is updated synchronously capacity tunable bandpass filter 2.

Information about the frequency detuning of the signal is contained in the value of the derivative, i.e. for signal

s(t)=A0sin(ω t+ϕ0), t∈ [0, T]

derivative of y(t) is equal to

y(t)=A0ωcos(ω t+ϕ0)=B(ω )cos(ω t+ϕ0), t∈ [0, T] (T is the duration of the signal).

This frequency detuning is determined by the first differentiating unit 6 and then allocated using the first amplitude detector 7, which may be performed, for example, as a determinant of the module.

As the basic operation in identifying the frequency shift is a linear operator, i.e, by differentiation, in the whole range of frequency shift, the noise immunity of the device of APF is implemented as potential. Structurally and technically, this is achieved using the first integrating device 8 that performs the optimal operation of calculating the autocorrelation function over the output voltage of the amplitude detector 7.

In order to control the frequency adjustment device voltage could be both positive and negative depending on the sign of the initial frequency detuning, is used in the reading device 9, to the inverting input of which is supplied from the voltage generator 10, the shape of which is similar to the output signal of the integrator 8 at zero initial frequency detuning.

For device PAPP as image detector used blocks 11, 12 and 13, through which runs the optimal non-coherent filtering of the radar pulse and the decision about the presence or absence of the signal in the noise threshold device 13.

Synchronous operation is provided by the synchronizer 14.

Thus, in the automatic tuning bandpass filter provides a high immunity by suppressing the powerful noise components by the instantaneous adjustment with the introduction of the derivative band-filtered voltage in the management capacity of the tunable bandpass filter, and determine the frequency detuning of the linear differential device and further optimal filtering through the operation of integration.

Industrial applicability.

The automatic tuning bandpass filter may be applied in various fields of radio as an effective filter for reception of radio signals with unknown frequency in radio systems, radar systems, synchronization systems, etc.

the sources of information

1. Kantor L.Y., Dorofeev V.M. Robustness of reception of FM signals. - M.: Communication, 1977.

2. System phase-locked loop with elements of sampling/ Shahgeldyan CENTURIES, Shoukin A.A., Karjakin V.L. and other edited Vol. - M.: Communication, 1979.

3. Shelukhin I. the short-range Radio system. M.: Radio and communication 1989.

4. Sahtain B. I. Random processes in engineering. M.: Radio and communication, 2002.

5. Tikhonov, V.I. Optimum reception of signals. M.: Radio and communication, 1983.

6. A.S. 1626336 (51), 5 N 03 J 3/00, Uastring, Vigdorovich, Wasecret, Euscript. The automatic tuning bandpass filter.

The automatic tuning bandpass filter containing the serially connected band pass amplifier-limiter, the input of which is the input of the tunable bandpass filter in the form of the first single series resonant circuit in which the variable capacitor with one output connected to the common wire, and the second output to the output of the bandpass filter, and a buffer amplifier and connected in series to the first amplitude detector and the first integrating device, characterized in that it introduced between the output of the first buffer amplifier and an output device connected in series parametric adjustment device is in the form connected to the common wire of the second single of the series resonant circuit with the second variable capacitor, the second buffer amplifier, the second amplitude detector, the second integrating device and a threshold device, and also introduced the first differentiating device connected between the output of the second buffer amplifier and the first input of the amplitude detector, and entered successively the United synchronizer, the reference voltage generator and subtractive device, the output of which is connected to control inputs of the adjustable capacitors of the first and second single series resonant circuits respectively tunable bandpass filter and parametric correction device, and not inverting second input of subtractive device connected to the output of the second integrating device, and the output of the synchronizer is also connected to the clock inputs of both the first and second integrating device and threshold device, when it entered the second differentiating the input device is connected to the output of the first buffer amplifier, and the output to the second control input of the variable capacitor tunable bandpass filter.



 

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