RU1800622C - Linear section of superhet radio receiver with interference suppression in mirror channel - Google Patents

Abstract

Usage: radio engineering, superheterodyne radio receivers. SUMMARY OF THE INVENTION: a linear path of a superheterodyne radio receiver with suppression of mirror channel noise comprises a high frequency amplifier 1, a mixer 2, a tunable local oscillator 3, an intermediate frequency amplifier 4, a mirror channel interference recognition unit including a gating unit 5, a dispersion delay line 6, an amplitude detector 7, as well as delay elements 8 ... 8m, elements I 9 ... 9s, a shaper of the interference frequency code of the mirror channel 10, a switch 11 and a source of control signals 12. The devices provide with increased noise immunity. 5 ill.

Description

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The invention relates to radio engineering and can be used in superheterodyne radio receivers of continuous signals.

An object of the invention is to increase the noise immunity of a radio receiver.

Structural diagram of the device shown in figure 1. The device comprises a high frequency amplifier (UHF) 1, a mixer 2, a tunable local oscillator 3, an intermediate frequency amplifier (IFA) with a controlled tuning frequency 4, as well as a block for interference recognition of the mirror channel, consisting of a gating unit 5, a dispersion delay line (DLZ) b, amplitude detector 7, and delay elements 8i-8n, elements And 9i-9n, shaper of the interference frequency code of the mirror channel 10, switch 11, and the source of control signals 12,

UHF input 1 is the input of the device. The output of the UHF 1 is connected to the first input of the mixer 2 m with the input of the gating unit 5. The second input of the mixer 2 is connected to the output of the tunable local oscillator 3. The output of the mixer 2 is connected to the input of the amplifier with a controlled tuning frequency 4, the output of which is the output of the device. The output of the gating unit 5 is connected to the input of the DLZ 6, the output of which is connected to the input of the amplitude detector 7. The output of the amplitude detector 7 is connected to the inputs of n circuits, each of which contains a delay element 8i and element And 9i connected in series. i 1, p, the other input of which is connected to the output of the amplitude detector 7. The output of the i-ro element And 9i is connected to the i-th input of the noise frequency generator of the mirror channel 10, the i-th output of which is connected to the i-th control the input of the switch 11, the i-th input of which is connected to the i-th output of the source of control signals 12. The output of the switch 11 is connected to the control inputs of the tunable local oscillator 3 and the amplifier with a controlled tuning frequency 4.

It should be noted that the tunable local oscillator 3 and the IF with a controlled tuning frequency 4 are constructed in such a way that it is possible to tune to n intermediate frequencies fnpj at the same frequency of the received signal fc. In this case, the condition fnpi h-1 fnpj A fn, where А fn is the IF bandwidth, is the same for all frequencies fnpj. For definiteness, we will assume that for all intermediate frequencies the upper tuning of the local oscillator 3 is used, i.e. fn fc. In addition, the DLZ bandwidth

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b should be wider than the frequency range of the main and all mirror reception channels, and within this band the dispersion characteristic r3 (f) of the DLZ 6 should be close to linear.

The principle of operation of the proposed device is as follows.

Let the device receive a continuous signal of frequency fc with conversion to the ith intermediate frequency fnpi fri - fc by setting the frequency of the signal of the tunable local oscillator 3. In order to achieve the object of the invention, it is necessary to establish the presence of interference at frequency f3 | fri + fnpi corresponding to the mirror channel of reception, and eliminate its reception.

To solve this problem, the proposed device uses a block of interference recognition of the mirror channel, consisting of a gating block 5, DLZ b, amplitude detector 7, n delay elements 8i-8n, n elements And 9i-9n, the frequency code generator of the interference channel 10, switch 11 and control signal source 12.

Using gating unit 5, a periodic sequence of radio pulses is formed from the received continuous radio signal and interference, which is fed to the input of the broadband DLZ b, delaying these radio pulses for different time intervals g3 depending on the carrier frequency of the signal, which is different for the main and i-ro mirror reception channels. Depending on the result of recognizing the situation in the code generator of the interference frequency of the mirror channel 10 through the switch 11 from the source of control signals 12, the control signal that implements a synchronous change in the frequency fn to another is supplied to the control inputs of the tunable local oscillator 3. frequency frj and tuning the IF from frequency fnpi to frequency fnpj ffj - fc. In this case, the frequency frj is selected so that there is no interference at the frequency f3j-frj + fnpj.

Consider the possible modes of operation of the receiving device,

1, initial installation.

After the device is turned on, the generator of the interference frequency code of the mirror channel 10 generates at its first output a signal supplied to the first control input of the switch 11, as a result of which the control signal from the source of control signals 12 passes to the output of the last from its first input, realizing the tuning of the tunable the local oscillator 3 to the frequency fn and the amplifier with a controlled tuning frequency 4 to the frequency fnpi fn - fc. Thus, the device is ready to receive radio signals with conversion to an intermediate frequency fnpi.

Reception of a radio signal on the main channel at a frequency fc (no interference on the mirror receiving channel).

Timing diagrams explaining this reception case are shown in FIG. 2,3.

A received radio signal at a frequency fc is received at the input of the device (see Ui (t) of FIG. 3a). UHF 1 amplifies this signal. From the output of UHF 1, this radio signal is fed to the first input of mixer 2 and to the input of gating unit 5. The second input of mixer 2 receives the voltage frequency fri from the output of tunable local oscillator 3, From the output of mixer 2, the signal at the intermediate frequency fnpi fri - fc goes to the input A drive with a controlled tuning frequency 4 tuned to the frequency fnpi, and then to the output of the device.

In gate block 5, a periodic sequence of radio pulses U2 (t) of FIG. 36 and FIG. 2a, of duration d with a repetition period T, which is fed to the input of the DLZ 6. The dispersion characteristic T3 (f) of the broadband DLZ 6 is shown in FIG. 26. In this DLZ, the incoming radio pulse is delayed by the time G3c (see Fig. 2c and Fig. Sv). From the output of the DLZ 6 pulses U3 (t), FIG. Sv, received at the input of the amplitude detector 7, The pulse U3 (t) is delayed relative to the pulse U. (t) for a time Г3с, corresponding to the frequency fc. At the output of the amplitude detector 7, a sequence of video pulses U4 (t), FIG. 3G, is generated, which is fed to the inputs of delay elements 8i. J 1, n, and to the inputs of the elements U 9i, i 1, ri. In each delay element 8), the input pulse is delayed by a time t corresponding to the delay interval in DLZ 6 between the pulses received on the main fc and mirror f3j channels when converting to the ith intermediate frequency fnpi frj - fc. Thus, in the first delay element 8i, the delay time is th (see Fig. 4c), in the second - t 32, in the 5th delay element 8p - t 3p. Since in this situation there is no interference on any of the n mirror channels, then on each period T of the sequence U2 (t),

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FIG. 36, there will be no pulses at the outputs of the elements And 9i, i 1, n. Thus, no signals are received at all inputs of the driver of the interference frequency code of the mirror channel 10. In this case, the state of the device corresponds to the initial setting and it receives a useful signal with conversion to an intermediate frequency fnpi

Simultaneous reception of radio signals through the main channel at a frequency fc and through the first mirror channel at a frequency fsi fn fnpi Timing diagrams explaining this case of reception are presented in FIG. 4,5.

The received useful signal at the frequency fc and the interference at the frequency f3- | fri + fnpi of the reception mirror channel when converting to the intermediate frequency fnpi, FIG. 4a.

In the UHF, these radio signals are amplified and fed to the first input of the mixer 2 and to the input of the gating unit 5, in which a sequence of radio pulses U2 (t), Figs. 56 and 4a, is supplied to the input of the DLZ 6. Like the case considered above, since the sequence U2 ( t) is an additive mixture of signals of two different frequencies fc and fai fn + fnpi, then in DLZ 6 the delay of useful and interfering signals will be different. The useful component of the signal U2 (t) will be delayed by t3 t3s, and the interference component by time g31. FIG. 4c. It should be noted that t31 - g3c g 31, where t 31 is the delay time in the first delay element 8i.

Thus, a signal U3 (t) is generated at the output of the DLZ 6, Fig. 5c, which is a sequence of paired pulses on each period T. The first pulse of the signal Uz (t) is delayed relative to the corresponding input pulse of the signal U2 (t) by time t3s, and the second by time tz1. From the output of the DLZ 6, the signal lJ3 (t) is fed to the input of the amplitude detector 7, at the output of which a video signal is generated), Fig. 5g, which enters the inputs of the delay elements 8i,, ri, and the inputs of the elements And 9i, i 1, gG. In each delay element 8i, the signal U4t) is delayed by a time of 3. From the outputs of the respective delay elements 8i, the signals (e.g., Us (t) in Fig. 5d for the first delay element 8i) are fed to the other inputs of the respective AND elements 9j. So

as soon as the delay time is r 31 in the first delay element 8i, then only the output pulses of the coincidence Ue (t) appear at the output of the first I / I element 9i, Fig. 5e, on each period T. There will be no signals at the outputs of the remaining elements And 9i, I 2e.

Thus, in the situation under consideration, only pulses Ue (t) are received only at the first input of the noise frequency generator of the mirror channel 10. There will be no signal at the remaining p-1 inputs of the driver 10. In this case, only at the second output of the shaper 10 a signal arrives at the second control input of the switch 11, as a result of which the control signal from the second output of the source of control signals 12 passes to its output. This signal is fed to the control inputs of the tunable local oscillator 3 and a gain controller with a controlled tuning frequency 4, which leads to the input to the second input of the mixer 2 from the output of the tunable local oscillator 3 signal with a frequency fr2 and at the same time tunes the amplifier 4 to an intermediate frequency fnp2. The signal is converted to an intermediate frequency fnp2 fr2 fc.

Simultaneous reception of radio signals through the main channel at a frequency fc, through the first mirror channel at a frequency f3i and through several other mirror channels at frequencies f3 |, i M.

In this case, at the output of DLZ b, at each gate period T, several pulses are observed (their number is equal to the number of received signals). The outputs of several elements And 9i receive signals that are analyzed in the code generator of the noise frequency of the mirror channel 10. As a result of the analysis, the driver 10 passes through the switch 11 that control signal from the source of the control signals 12, which implements the transition to receiving an input signal with conversion to an intermediate frequency fnpj closest to the frequency fnpi and free from interference through the corresponding mirror channel f3j.

Thus, in the device according to the invention, by detecting the fact of interference on the mirror channel and receiving the signal with conversion to such an intermediate frequency at which there is no noise on the mirror channel, an increase in noise immunity is achieved.

Claims (1)

The claims The linear path of a superheterodyne radio receiver with suppression of mirror channel interference, containing a high-frequency amplifier connected in series, a mixer with a tunable local oscillator connected to it and an intermediate-frequency amplifier with a controlled tuning frequency, as well as a mirror-channel interference recognition unit connected between the output of the high-frequency amplifier and control inputs of a tunable local oscillator and an intermediate frequency amplifier with a controlled tuning frequency, characterized in that, with In order to increase noise immunity, the mirror channel interference recognition unit is made in the form of a gated block, a dispersed delay line and an amplitude detector, n circuits, each of which contains a delay element and an I element connected in series, the circuit inputs and other inputs of the And circuit elements are connected to the output the amplitude detector, as well as the generator of the interference frequency code and the mirror channel and the switch, to the inputs of which the outputs of the source of control signals are connected, while the outputs and outputs of the mirror channel interference frequency code generator are connected respectively to the circuit outputs and control inputs of the switch, and the output of the switch is the output of the mirror channel interference recognition unit. CM CN CO O oh co Ј - V oi "( &  -f a) H -CD -CD PiiiiiiiifiiiiMiPSi i iiiPfftMiiiiii ni shiik B) Ј3 -V