PANORAMIC MEASURING RECEIVER ARK-D1TR..

PANORAMIC MEASURING RECEIVER ARK-D1TR..

SERGEEV Viktor Borisovich,
SERGIENKO Alexander Rostislavovich,
PEREVERZEV Sergey Borisovich.

 PANORAMIC MEASURING RECEIVER ARC-D1TR

This article discusses the panoramic measuring receiver ARK-D1TR, the features of its use in stationary and mobile multifunctional measuring complexes and methods for calibrating the hardware and software part of the radio receiver and the complex as a whole. This article opens a series of publications on news in the field of domestic certified measuring equipment.

The task of conducting radio and radio engineering measurements

The most important tasks of improving radio monitoring systems include the need to increase the accuracy of measuring the frequency and time parameters of radio signals. Such parameters include the values ​​of the carrier frequency and level, bandwidth, etc. The development and production of domestic radio monitoring systems and complexes did not begin yesterday. Leading government organizations and commercial firms have developed a large number of technical means with radio monitoring functions, panoramic and spectral analysis, signal processing and analysis, direction finding, which are now available on the market. As user needs grow, the direction of development and production of measuring instruments has also recently experienced an upswing.

General information about the panoramic measuring receiver ARK-D1TR

The production of the panoramic measuring receiver ARK-D1TR of the 3rd generation was mastered within the framework of the program for the development of radio receiving complexes [3]. The receiver is designed to measure the parameters of radio signal spectra in the frequency range from 20 to 2020 MHz. Such complexes are automated, provide input of information into the system, automation of the measurement process, processing and display of measurement results.

The receiver is a portable table-top device consisting of two main units — the CT1 unit and the ATSO1 unit. The appearance of the receiver from the rear panels is shown in photo 1.

 Photo 1. Receiver appearance

The receiver has wide functionality in terms of signal processing, namely: reception, amplification, frequency selection in the range, digitization, processing using software installed directly in the product with flexibly changing algorithm parameters with the output of spectral data for further processing and visualization.

• Input signal frequency range 20 … 2020 MHz, with additional devices 9 kHz … 18 GHz.
• Panoramic analysis speed in the operating range 150 MHz/s.
• The frequency stability of the built-in reference generator is 2×10-6, an external reference signal input is provided.
• Limits of permissible absolute error in frequency measurement:

— ±3 kHz at frequencies from 20 to 1012 MHz;
— ±6 kHz at frequencies above 1012 to 2020 MHz.

• Software-switchable spans of 2 MHz, 1 MHz, 250 kHz.
• Permissible absolute error in setting the span ±4 kHz.
• VSWR at the input with a nominal input impedance of 50 Ohm is no more than 3.
• The level of intrinsic noise is no more than:

— minus 116 dBm (minus 9 dBμV)*) – at frequencies from 20 to 1012 MHz;
— minus 113 dBm (minus 6 dBμV) – at frequencies above 1012 to 2020 MHz.

• Single-signal selectivity for side channels at mirror and intermediate frequencies is not less than 70 dB.
• The selectivity for side channels at combination frequencies must be at least 70 dB (in the frequency range from 1012 to 2020 MHz, the selectivity for side channels at combination frequencies is not standardized).
• The maximum permissible signal at the receiver input is 100 mV.
• The range of measured input signal levels is from a level 6 dB higher than the level of intrinsic noise to minus 7 dBm.
• The limit of permissible absolute error in measuring levels:

— without additional calibration – ±3 dB;
— with additional calibration – ±1.5 kHz.

• Intermodulation distortion of the 3rd and 2nd order is no more than minus 70 dB.
• The resolution for distinguishing two signals is no worse than 7 kHz.
• The receiver is powered from an external DC source with a nominal voltage of 27 V.
• Permissible deviations of the supply voltage from the nominal ±3 V.
• The current consumption is no more than 1.2 A.
• The operating mode establishment time is no more than 30 min.
• The duration of continuous operation is not less than 24 hours.
• Overall dimensions no more than (340x260x130) mm. In this case, the overall dimensions of the blocks are no more than:

— of the CT1 block – (300x255x65) mm;
— of the ACO1 block – (300x255x65) mm.

• Weight no more than 7.5 kg. In this case, the weight of the blocks is no more than:

— of the CT1 block – 4.0 kg;
— ACO1 block – 2.5 kg.

• Mean time between failures – not less than 10,000 hours.
• Average service life not less than 5 years.
• Climatic version type – UHL3.1 according to GOST 15150 under operating conditions:

— operating temperature range from +5 to +40° C;
— relative humidity up to 98% at a temperature of +25° C;
— atmospheric pressure – from 84 to 106.7 kPa.

A qualitatively new level of technical characteristics in comparison with previously used receivers is due not only to the use of a modern element base, originality of circuit solutions, but also to previous many years of development in the field of creating our own radio receiving devices. Preliminary studies were conducted in the field of creating high-frequency paths of a radio receiving device (RPU), an analog-to-digital conversion system, algorithms for digital signal processing, and solving problems of interblock electromagnetic compatibility. The consequence of these measures was the creation of a radio receiving device that combines an increased dynamic range, high speed of panoramic analysis with small (variable) discreteness of spectrum display by frequency, high stability of the parameters of the high-frequency path and timing devices, a low level of intrinsic noise and a practical absence of affected frequencies. All necessary capabilities for calibrating the receiver as a whole and its individual units are also provided, which will be discussed below. All the listed features of the product made it possible to use it as a means of measuring signal parameters, which is confirmed by the certificate of the State Standard of Russia [1] and the license of the State Standard of Russia for its production [2].

Considering the above, two obvious areas of application of the receiver can be identified.

Firstly, the receiver can be supplied exclusively as a measuring device operating autonomously under PC control. In this case, the user can create a complex based on the receiver and existing equipment. Additionally, it is possible to supply measuring calibrated antennas for the range of 9 kHz — 18 GHz and increase the range of operating frequencies of panoramic analysis to 6 GHz or to 18 GHz using an external remotely controlled frequency converter ARK-KNV4, which is currently undergoing certification.

Secondly, it is possible to supply the receiver as an element of a ready-made radio monitoring complex and/or search for technical channels of information leakage.

The logical structure of the receiver repeats its design. The structural diagram of the ARK-D1TR receiver is shown in Fig. 1.

Fig. 1. Structural diagram of the ARK-D1TR receiver

The CT1 unit is designed to receive radio signals with a frequency of 20 to 2020 MHz and convert them to an intermediate frequency of 10.7 MHz.

The structural diagram of the CT1 unit (Fig. 2) reflects the internal relationships between the elements of the unit.

 Fig. 2. Block diagram of the CT1 unit

The preselection unit performs primary filtering of the signal in order to match its parameters with the characteristics of the converters in the mixer unit. The synthesizer unit forms a grid of reference frequencies. In the mixer unit, signals are transferred from radio frequencies to the IF and internal mirror channels associated with the transfer process are suppressed.

The control unit ensures coordination of the entire process, receiving, in turn, commands from the ACO unit.

The second main structural unit of the receiver, the ACO1 unit, consists of an analog processing unit (APU), a digital signal processor (DSP) unit, a control controller, and a power supply unit. The structural diagram of the ACO1 unit is shown in Fig. 3.

Fig. 3. Structural diagram of the ACO1 unit

The AO block prepares the tuner output signal for digitization and further digital processing in the DSP block with signal transfer to the input frequency of the ADC device 1.6 MHz, as well as the required signal amplification. In addition, the AO block provides suppression of mirror channels no worse than 70 dB.

In the DSP block, analog signals are converted into digital form for the actual conversion of signal data from the time domain to the spectral domain. It consists of an analog-to-digital converter (ADC), the DSP itself, and PC interface circuits. Then the data, already in the form of signal spectrum information, is sent to the PC for final processing, storage, and display.

The control controller performs the functions of controlling the ADC1 block and is also a transmission link for control information between the PC and the CT1 block.

The top-level software installed on the control PC is represented by the device driver and the user shell, providing the user interface, including control elements and data display. The driver for working with the receiver uses a fixed wide system of commands.

The requirements for the PC are relatively low, since most of the resource-intensive calculations for signal processing are performed in the receiver's DSP unit. The PC must have a processor no worse than Pentium 533, at least 64 MB of RAM, and free USB and LPT1 ports. The software runs under Windows-98, -NT, -2000.

Depending on the purposes of using the receiver, the delivery set may include various software packages. The SMO-D1TR program is used as the basic program.

Control software for the panoramic measuring receiver ARK-D1TR

Depending on the receiver's intended use, the delivery set may include various software packages. The SMO-D1TR program is used as the basic program.

This program is designed to control the receiver, calibrate the receiver and display in real time the results of fast spectral analysis of radio signals with a controlled resolution from 3.125 kHz to 390.625 Hz. The program's graphical interface is shown in Fig. 4.

 
Fig. 4. SMO-D1TR-M program graphical interface

The central part of the interface is occupied by a graphic panel, which displays the spectra of signals received by the receiver. The horizontal axis of the panel shows the frequency values ​​in megahertz, and the vertical axis shows the level in decibels relative to 1 μV.

On the right side of the graphical interface there is a panel that displays the receiver settings – receiver tuning frequency, input attenuator position (0.10, 20 or 30 dB), reference signal source (internal or external), as well as measurement parameters – span (0.25, 1.0 or 2 MHz) and spectrum averaging.

The following measurement parameters are located at the bottom of the graphical interface: measurement zone width, vertical marker position by frequency, horizontal marker position by level, and spectrum observation mode. The results of signal spectrum measurements are also displayed here: the magnitude of the spectral component at the position (frequency) of the vertical marker, the frequency and level of the maximum component in the specified measurement zone, the difference in frequency and level between the results of measurements of the maximum component in the specified zone and at the position of the vertical marker.

Signals are measured in two modes: “Continuous” and “Single”. In the “Continuous” mode, spectral samples are continuously obtained with a time resolution determined by the speed of the PC and the DSP. In the “Single” mode, a single spectral sample is obtained by an operator command or an external synchronizing event.

The “Zone Width” window indicates the spectrum section in the vertical marker area where measurements are taken. The automatically measured value of the frequency and level of the maximum component of the signal spectrum in the measurement zone is displayed in the “Measurement B” panel in the “Frequency” and “Level” windows, respectively, and as marks on the vertical and horizontal axes of the graphical interface. The “Measurement A” window displays the frequency and level of the spectral component. The levels of the measured signals are measured in decibels relative to 1 μV.

When measuring signal parameters in the “Single” mode, the “Start” command stores the signals on the graphical interface of the program. The “Difference A-B” window displays the results of calculating the difference in frequency and level values ​​between the stored value of the maximum component measured in the zone and the current value in the position of the vertical marker.

Possibilities of using the receiver as part of complexes with specialized functions

The second of the specified application areas deserves special attention — as part of radio monitoring, radio measurements and detection of technical information leakage channels. The complexes are a set of measuring instruments combined with auxiliary devices according to the functional feature of identifying received signals and measuring their parameters. Further in the text, the names of devices used to create flexible structure complexes based on receivers of our own production will be used.

The radio monitoring complex based on the panoramic measuring receiver ARK-D1TR includes, in addition to the already listed receiver units, a specialized power supply unit and an antenna switch unit. A set of antennas can be connected to the antenna inputs of the switch — a broadband antenna ARK-A2M, an external reference antenna ARK-A5 with an amplifier ARK-AU1 and a specialized automobile antenna ARK-A7I. In addition, the active and passive network probes ARK-ASP2 and ARK-PSP2 can be connected to the HF inputs of the antenna switch, and the remote module ARK-VM-K2 with a set of remote antennas ARK-A2A1, ARK-A11A1 and ARK-A11K is also connected to the special control bus connector «D3» and the dedicated antenna input «ANT. 4».The presence of auxiliary devices in this case dramatically expands the capabilities of the equipment. In particular, it becomes possible to organize a distributed antenna system, as well as a system for remote radio monitoring of remote premises. The latter is achieved by connecting remote modules that are installed in remote premises and create a kind of “presence effect” of all the equipment in each of the monitored premises.

The VHF-AK antenna switch connects one of its inputs to the antenna input of the digital tuner. In turn, a VHF antenna, an ARK-KNV0 converter (9 kHz — 20 MHz) or an ARK-KPS wired network control unit, which transfers signals from wired networks to the VHF range (105 … 135 MHz), can be connected to the antenna input. A radio signal from a remote module with an ARK-KNV2 (2 — 6 GHz) or ARK-KNV4 (2 … 18 GHz) converter can also be fed to one of the VHF-AK switch inputs. It is also possible to supply power voltage to antenna amplifiers through the switch and the HF cable along the central core.

The KV-AK antenna switch is used to connect network probes or HF antennas. The switch has a built-in controlled attenuator with an attenuation of 20 dB.

When using remote antennas or expanding the frequency range to 6 GHz, the ARK-VM-K2 remote module with the ARK-KNV2 converter (2 — 6 GHz) is used.

Photo 2 shows the appearance of the remote module, respectively, the front view and the back view.

Photo 2. Remote module. View of the front and rear panels

In Fig. 5The structural diagram of the remote module is presented. The ARK-KNV2 converter unit functions as a frequency converter for the signal received in the 2–6 GHz range. The HF switch switches signals from one of three antennas, which can be connected to the remote module via an antenna amplifier.

Fig. 5. Structural diagram of the ARK-VM-K2 remote module

Metrological aspects of using ARK-D1TR panoramic measuring receivers

The main features of using measuring receivers as part of single-channel complexes include:

• multivariance of signal transmission to the receiver input through switched intermediate paths containing converters, attenuators, switches, buffer amplifiers, etc.;
• optionality of the structures of the complexes, leading to differences in the composition of switched intermediate paths in different implementations of the complexes;
• “openness” of the structures of the complexes, allowing modification at the operational stage;
• use of various classes of measuring antennas (indoor, outdoor, specialized, etc.) during operation;
• a fairly wide range of operating temperatures.

In this regard, the tasks of reducing measurement errors in a wide range of operating temperatures, characterized by the optionality of structures and the multivariance of signal transmission in a given structure, are of particular relevance.

Such tasks include:

• improving the hardware of blocks and units of the radio receiving path for transmitting signals;
• use of built-in computing control subsystems in the blocks that optimize the operating mode of the blocks, including automatically generating the necessary corrective actions to minimize equipment errors when changing operating modes and changing the temperature of the blocks;
• use of methodological and information support for calibration procedures of the system as a whole at different stages of the life cycle of the measuring system: during adjustment, during routine periodic calibrations of systems, during preventive maintenance, etc.;
• development and use of technological hardware and software for automated and automatic calibration of systems.

The most important feature of the hardware and software complex for receiving and processing signals of modern mobile automated radio monitoring systems is their multifunctionality, which leads to the need for automatic connection of a fixed set of hardware units into a given structure to solve a given problem. The metrological level of radio monitoring complexes is determined by all components of these systems, including methods and algorithms for mathematical support of measurements, the class of technical support of the computing tools used, sensitivity, error and susceptibility to interference of the hardware and software complex for receiving and processing signals. However, the main sources of error in the composition of the complexes should include the radio signal transmission path to the analog-to-digital signal processing device (when measuring the levels and frequencies of radio signals) and the antenna (when measuring the levels of radio signals).

In Fig. 6 shows a generalized diagram of the signal flow in the measuring complexes.

Fig. 6. Generalized diagram of the signal flow in the measuring complexes

Here, the main “sections” of the generalized structure are conventionally displayed, introducing additional error into the amplitude-frequency transfer characteristic of the signal transmission path.

The section of antennas and feeders characterizes the possible types of antennas (feeders). Only measuring antennas with a known calibration file for a given frequency section can be used to carry out measurements. The set of measuring antennas covers individual main sections of the operating range, but it is nevertheless practically impossible to cover the entire range.

System units — antenna switch, attenuators, amplifiers are designed to work in the entire frequency range. Converters — frequency converters that expand the operating frequency range of the radio receiver.

Connectors — cables and connectors have uncompensated inhomogeneities, leading to an increase (depending on frequency) in VSWR on internal signal transmission lines from unit to unit. The quality of connectors deteriorates over time due to wear (deterioration of surface quality, density of connections, etc.) of connectors.

The difference between the actual structure of the measuring complex and the optimal one (minimum, consisting of a measuring antenna, a measuring receiver and a display device) leads to the need to take into account and compensate for the additional error when carrying out special calibration procedures. The specified measurement error is associated with the dependence of the modules of the transmission coefficients of the passive (switching and feeder) and active paths (converters, attenuators, buffer amplifiers, etc.) on the frequency, temperature, and atmospheric pressure.

The ARK-D1TR hardware and software panoramic measuring receiver has the ability to generate and use calibration files for the system as a whole during operation. A special feature of the calibration is the use of three-dimensional calibration files that match the given frequency of the system settings and the current temperature with a correction factor.

Calibration of the complex is carried out using reference signal sources, attenuators and connectors, the error of which is 3-5 times less than the permissible basic error of the complex. Calibration is carried out at several reference points of the frequency range by changing the value of the transfer function until the nominal reading is obtained. Calculation of corrections between two reference points is carried out using the linear interpolation method, which significantly simplifies the correction algorithm. By increasing the number of reference points, it is possible to reduce the systematic error to a level determined by the error of the calibration process. Calibration allows you to check the serviceability of the hardware and software complex and reduce its systematic error.

Interpolation allows one to find correction values ​​corresponding to points between two reference points with a given error. It should be noted that the interpolation problem is correctly solved under the assumption that the law of change of the studied function in intermediate values ​​of the argument has the same character as in its discrete (measured) values.

The accuracy of interpolation depends on the interval (t2 — t1) of change of the argument and the increment F(t2) — F(t1) of the function estimated by tabular differences; the smaller these differences, the simpler the interpolation formulas and the more accurate the result.

With linear interpolation, the reading F(t12) at an arbitrary point t12 between points t1 and t2 is determined by the formula [4]:

F(t12)=F(t1)+(t12 -t1)(t2-t1)-1[F(t2)-F(t1)]

In the ARK-D1TR receiver, calibration using the linear interpolation method between reference points is performed:

• at the stage of adjusting the hardware and software part of the ARK-D1TR receiver (setting the preselector block);
• when compiling a calibration file for a given structure — a three-dimensional array of correction values ​​for reference points by frequency and temperature;
• when taking into account the calibration files of the measuring antennas.

The preselection block is designed to weaken the passage of signals on side channels and reduce the dynamic range of the signal at the input of the first tuner mixer. The block contains ten range-switched filters for the operating frequency intervals: 20 — 35, 35 — 60, 60 — 100, 100 — 170, 170 — 240, 240 — 333, 333 — 465, 465 — 700, 700 — 1012, 1012 — 2020 MHz, switched by analog switches. Within the range, each filter is reconfigured, and the average frequency of the filter passband corresponds to the reception frequency. In the frequency range of 20 — 1012 MHz, band-pass filters are used, and in the range of 1012 — 2020 MHz — a high-pass filter with an adjustable (corresponding to the reception frequency) cutoff frequency.

The control of the switches and filters is provided by a special preselector controller after the procedure of individual programming of the processor's permanent memory with the values ​​of control voltages, providing precise adjustment of the filters at 16 points of each frequency range. In the operating mode, the voltages supplied to the filter varicaps from the outputs of the DAC block are determined by the method of linear interpolation of the values ​​taken from the array of control voltages. The indices by which the selection of control values ​​is made are calculated based on the receiver tuning frequency. A similar approach to the preparation and use of arrays of control voltages is used to maintain the non-uniformity of the transfer coefficient of the preselection block. The graphical interface of the receiver preselector calibration program window is shown in Fig. 7.

 
Fig. 7. The ARK-D1TR receiver preselector calibration program window

Calibration of the specified structure of the complex is implemented according to the schemes shown in Fig. 8:

• without taking into account the receiving antenna — in a circuit with a reference signal generator, in which case the hardware and software complex is actually calibrated; the accuracy limit is determined by the dependence of the VSWR at the input on the frequency;
• with taking into account the receiving antenna — in a circuit with the emission and reception of signals from the reference generator using an auxiliary measuring antenna; the accuracy limit is determined by the calibration conditions, in particular, the propagation conditions of radio waves.

Fig. 8. Calibration schemes for the specified structures of the complexes

The graphical interface of the calibration window is shown in Fig. 9.

Fig. 9. Graphic interface of the calibration window of the SMO-D1TR-K program

To select a frequency calibration point, use the arrow in the “Range” window and select the required frequency range from the drop-down list in the window. Then use the arrows in the “Frequency” window to set the required frequency value, and then click the “Insert” button.

The required correction value of the input signal level at the selected frequency is set using the arrows in the “Value” window:

• To restore the original value of the input signal level, click the “Original” button, and to delete the calibration point, click the “Delete” button.
• To quickly move within the selected frequency range by inserted calibration points to change the correction value of the input signal level, click on the arrow in the “Calibration point” window and select the required point from the drop-down list.
• To record the values ​​of the performed calibration in the permanent memory of the corresponding control arrays, click on the “Record” button.
• To restore the original calibration values, click on the “Reset” button.
• To read the calibration values ​​recorded in the permanent memory, you must click the “Read” button.
• To exit the calibration program, you must click the system button to close the calibration program window.

Calibration is carried out in certain temperature ranges inside the receiver:

• from minus 30° C to minus 25° C;
• from 0° C to +5° C;
• from +30° C to +35° C;
• from +60° C to +65° C.

At other temperatures inside the receiver, calibration is not performed. Between temperature calibration points, the calibration coefficient is calculated using the linear interpolation method.

The “Temperature” panel displays data on the current temperature inside the receiver and the temperature at which the level correction is performed for recording in the data array.

Frequency calibration points are selected from the drop-down list in the “Range” window and from the drop-down list in the “Calibration point” window. If necessary, new calibration points can be added to the list in each range. To do this, enter the required frequency value in the “Frequency” window. The total number of calibration points is not limited. The required correction value of the input signal level at the selected frequency is set using the arrows in the “Value” window.

CONCLUSION

The results of the receiver certification tests showed a sufficient reserve for the main parameters. Currently, the development of the next modification of the new generation of measuring equipment (panoramic receiver «ARGAMAK») is being completed, characterized by:

• expansion of the frequency range to the low frequencies up to 9 kHz, and the high frequencies up to 3 GHz;
• inclusion of a digital signal demodulator in the receiver;
• greater technological effectiveness and mass production;
• the ability to work in single-channel and dual-channel automated radio monitoring systems and identify technical information leakage channels with coherently coupled heterodynes.

The emergence of domestic Gosstandart-certified new generation measuring radio receivers opens the next page in the development of specialized radio electronic equipment production in Russia. It is obvious that this scientific and technical direction is only taking its first steps towards producing such products and creating a choice for the customer.

Literature

1. Certificate No. 13618 of the State Standard of Russia dated 03.12.2002 on entering the panoramic measuring receiver ARK-D1TR into the register of measuring instruments of the Russian Federation under No. 23924-02.
2. License of the State Standard of the Russian Federation for the right to produce measuring instruments No. 000403-IR.
3. Ashikhmin A.A., Sergeev V.B., Sergienko A.R. Radio receiving paths of automated radio monitoring systems: features, solutions and prospects.//Special equipment. 2002. Special issue, pp. 57 – 64.
4. Vernik S.M., Kushnir F.V., Rudnitsky V.B. Increasing the accuracy of measurements in communications technology. Moscow: Radio and Communications, 1981. 200 p.