RU118812U1 - Exciter with a pseudo-random re-adjustment of the operating frequency - Google Patents

Abstract

An exciter with a pseudo-random frequency tuning (PFC) containing a modulated signal generator based on a DDS synthesizer, two channel synthesizers, the outputs of which are connected to the corresponding inputs of the RF switches, the third input of which is the control one, and its output is connected to the second input of the converter, the output of which connected to the input of the preamplifier, the output of which is the output of the device, while the first inputs of the shaper and channel synthesizers are control, and their second inputs are inputs for the reference frequency signals, characterized in that a series-connected amplifier and a narrow-band filter with a passband are introduced, matched to the spectrum of the generated signal, wherein the input of the amplifier is connected to the output of the driver, and the output of the bandpass filter is connected to the first input of the frequency converter.

Description

The utility model relates to the field of radio communications and can be used in radio engineering systems and is designed to generate signals with FSK and PSK modulation with pseudo-random tuning of the operating frequency (MHF).

Known pathogen circuits made on the basis of direct digital synthesis synthesizers () They can easily implement different types of modulations FSK and PSK at the output frequency of the pathogen. These devices have a high speed adjustment of the operating frequency. But in them there are restrictions on the frequency of the output signal.

According to the sampling theorem, in order to completely restore the output signal, at least two samples per signal period are required, which means that the maximum frequency of the synthesized signal will be (f _c is the frequency of the clock signals), and practically no more than 40% of f _c . Currently available DDS synthesizers are capable of generating a signal at frequencies up to 400 MHz at a clock frequency of 1 GHz.

There are known schemes of pathogens in which a signal with FSK and PSK modulation is performed by a DDS synthesizer at a subcarrier frequency, and then it is converted to the output frequency of the pathogen, for example, according to the utility model certificate No. 30047, Н04В 7/00.

Closest to the proposed one is the causative agent causative agent developed for the automated complex of communication facilities of the Pantsir-S system (section: Product Catalog, subsection: Telecode and voice communication systems of air defense systems), adopted as a prototype.

Figure 1 shows a diagram of the pathogen prototype, where the following notation is introduced:

1 - modulator of a modulated signal based on a DDS synthesizer;

2 - frequency converter;

3 - preliminary power amplifier;

4, 5 - channel synthesizers with a PLL loop;

6 - block RF keys.

The prototype exciter contains a modulated signal generator based on a digital direct synthesis synthesizer (DDS) 1 in series, a frequency converter 2, and a power pre-amplifier 3, the output of which is the output of the device. In addition, two channel synthesizers 4 and 5, the outputs of which are connected to the corresponding inputs of the RF key block 6, and the output is connected to the second input of the frequency converter 2. Moreover, the third input of the RF key block 6 and the first inputs of the channel synthesizers 4 and 5 are control. The second inputs of synthesizers 4 and 5 are inputs for the reference frequency.

The pathogen works as follows.

Using the control signals in the DDS synthesizer of the former 1, a modulated signal is synthesized at a subcarrier frequency, which is fed to the first input of the frequency converter 2, to the second input of which, using the RF key block, the outputs of the channel synthesizers 4 and 5 are alternately switched by control signals, with one of the synthesizers tuned to the operating frequency, and the second at this time is in the process of tuning to the next, thus, the frequency hopping mode is implemented.

In the prototype exciter, the upper working frequency is determined by the capabilities of synthesizers 4 and 5 with a PLL loop and exceeds the maximum possible output frequency of the DDS synthesizer, and the tuning time is determined by the switching time of the RF keys of block 6.

The difference between the spectrum of the generated modulated signal and the theoretical one is determined by several factors: the ratio of the output signal frequency and the DDS clock frequency, the error in signal generation associated with the effect of quantization of selected values of the low-frequency quadrature components, as well as interference associated with harmonics and combinational components of the control and clock signals of digital devices signal processing receptor exciter. Transformed in a mixer with combinational and noise components of the local oscillator signal, the spectrum of the output signal can be significantly distorted by side components.

For different types of modulation, the relative levels of out-of-band (taking into account the side) superimposed radio emissions should not exceed the values determined by the so-called restrictive line or spectrum mask of out-of-band radio emissions. (The norms of the State Commission on Radio Frequencies (SCRF) of Russia 19-86 on permissible spurious emissions.)

The disadvantage of the pathogen prototype is the presence in the spectrum of the modulated signal generated by it of side components exceeding the permissible level.

The objective of the proposed utility model is to reduce the distortion of the spectrum of the generated signal by the side components and bring it closer to the defined restrictive line or mask of the spectrum.

To solve this problem, a driver with pseudo-random tuning of the working frequency (PFRCH), containing a modulated signal driver based on a DDS synthesizer, two channel synthesizers, the outputs of which are connected to the corresponding inputs of the RF key block, the third input of which is control, and its output is connected to the second the input of the converter, the output of which is connected to the input of the preliminary power amplifier, the output of which is the output of the device, while the first inputs of the shaper and channel synthesis Ators are controllers, and their second inputs are inputs for reference frequency signals, according to a utility model, a series-connected amplifier and a narrow-band filter with a passband matched to the spectrum of the generated signal are introduced, the input of the amplifier being connected to the output of the driver, and the output of the band-pass filter connected to the first input of the frequency converter.

Figure 2 shows a diagram of the proposed pathogen, where indicated:

1 - modulator of a modulated signal based on a DDS synthesizer;

2 - frequency converter;

3 - preliminary power amplifier;

4, 5 - channel synthesizers with a PLL loop;

6 - block RF keys;

7 - amplifier;

8 - narrow-band filter.

The proposed pathogen contains serially connected modulator 1, amplifier 7, narrow-band filter 8, frequency converter 2 and pre-power amplifier 3, the output of which is the output of the device. In addition, the first 4 and second 5 channel synthesizers with a PLL loop, the outputs of which are connected to the corresponding inputs of the RF key block 6, the output of which is connected to the second input of the frequency converter 2. The third input of the RF key block 6 is an input for control signals. Moreover, the first inputs of blocks 1, 4, and 5 are inputs for control signals, and their second inputs are for reference frequency signals.

The proposed pathogen works as follows.

The signal with the subcarrier frequency generated in the driver 1 by means of a DDS synthesizer is fed to an amplifier 7, to the output of which a narrow-band filter 8 is connected, which is matched by the bandwidth with the spectrum of the generated signal. Thus, the suppression of side harmonic and combination components associated with the operation of the DDS synthesizer 1 and other digital devices of the pathogen. Then the filtered subcarrier signal is fed to the input of the frequency converter 2, to the second (heterodyne) input of which, as in the prototype, using the RF key block 6, the outputs of the channel synthesizers 4 and 5 are alternately switched, while one of the synthesizers is tuned to the operating frequency, and the second at this time is in the process of adjustment to the next.

To compare the energy spectra of the signals generated by the prototype pathogen and proposed in figure 3 shows the spectrogram of the QPSK signal taken at the output of the pathogen prototype, figure 4 is a QPSK spectrogram at the output of the proposed pathogen.

The parameters of the initial information messages for the QPSK signals generated in both types of pathogens are the same. In accordance with the SCRF standards for permissible spurious emissions for signals with QPSK, the requirements at point M2 (22.95 dB instead of 30 dB) and at point M3 (35.89 dB instead of 60 dB) of the spectrogram in Fig. 3 can be seen.

After considering the spectrogram in figure 4, we can conclude that there is a significant gain (from 8dB at point M2 to 25dB at point M3) in suppressing spurious emissions by the proposed pathogen compared with the prototype pathogen.

Information sources.

1. Patent No. 30047, Н04В 7/00 “Exciter with pseudo-random tuning of the operating frequency”. Korolkov M.A., Fridland O.B., Kolesnichenko G.D. (prototype).

2. All about DDS synthesizers. Eva Murphy, Colm Slettern Translation: Alexey Vlasenko, alexey.vlasenko@analog.spb.ru. / dds.

3., section: PRODUCT CATALOG,

subsection: Telecode and voice communication systems of air defense systems, rubric: Automated communication system of the system, "Shell-S".

4. GOST RV52226-2004. Radio transmitting devices. Requirements for the basic parameters of out-of-band and spurious emissions.

5. Standards GKRCh 19-86 on permissible spurious emissions.

Claims (1)

An exciter with a pseudo-random tuning of the operating frequency (PFRCH), comprising a modulated signal driver based on a DDS synthesizer, two channel synthesizers, the outputs of which are connected to the corresponding inputs of the RF key block, the third input of which is control, and its output is connected to the second input of the converter, the output of which connected to the input of the preliminary power amplifier, the output of which is the output of the device, while the first inputs of the shaper and channel synthesizers are control, and their the second inputs are inputs for the reference frequency signals, characterized in that a serially connected amplifier and a narrow-band filter with a passband matched to the spectrum of the generated signal are introduced, the input of the amplifier connected to the output of the driver, and the output of the band-pass filter connected to the first input of the frequency converter.