RU181982U1 - TRANSMISSION DEVICE WITH WIDE DYNAMIC RANGE AND LOW NOISE - Google Patents

Abstract

The utility model relates to communication technology and can be used to build a transceiver path of multiband broadband portable equipment with half-duplex mode of operation or digital full-duplex mode with time division. The transceiver includes an antenna 1, a block 2 switchable sub-octave filters (PSF), a switch 3 receive / transmit, the first low-noise amplifier 4 (LNA), the first block 5 switchable band-pass filters (PPF), a mixer 6, the second LNA 7, the second block 8 PPF , driver 9, analog-to-digital converter 10, connected by their outputs to the inputs in series. The transmit power amplifier 11 is connected through the second input of the receive / transmit switch 3 and the PSF block 2 to the antenna 1. The device is equipped with a frequency synthesizer 12, a programmable divider 13 and a mixer switch 14. A frequency synthesizer 12 is connected through a programmable divider 13 to the second input of the mixer 6. The mixer switch 14 is connected by an input to the output of the first PPF block 5 and by an output to the input of the second LNA 7. The device allows to increase the dynamic range, reduce noise, improve and simplify filtering, and due to this, reduce the size and simplify the device, increase its overall reliability.

Description

The utility model relates to communication, detection, telecommunications, radar, radio engineering and can be used to build a transceiver tract of multi-band portable communication equipment or radar, radio intelligence and radio control, other radio devices with half-duplex mode of operation or digital full-duplex mode with temporary separation.

Widely known are transceivers with superheterodyne-type receivers (for example, GV Korolev. “Electronic devices of automation.” Moscow, Vysshaya Shkola, 1991, p. 182-186). Device receivers have high selectivity and reception quality due to the fact that the main filtering of the useful signal occurs at a constant intermediate frequency (IF) regardless of the current operating frequency.

To transfer the signal at the receiver input to the inverter, a mixer is used - an analog element in which the radio frequency signal is mixed with the reference signal (local oscillator signal), so that a useful signal is generated at the inverter output from the mixer. However, the nonlinear properties of the mixer are used in this process, therefore, it is fundamentally impossible to obtain only one useful signal at the IF at the output of the mixer.

As a result of the combined action of the interfering signal at certain frequencies, called side reception channels (PCB), and the local oscillator signal, the output of the mixer generates interference at the IF, from which it is no longer possible to filter out the useful signal after the mixer. Therefore, interference signals at these frequencies must be suppressed before the mixer. Such filtering in receivers of a wide range of operating frequencies requires a large number of complex filters, especially for broadband receivers. This significantly increases the size and weight of devices, limits the range of operating frequencies of portable devices, leads to difficulties in tuning and stability of their characteristics, complicates the design.

The solution to this problem is to convert to a sufficiently high IF. This allows you to remove the frequency of the control panel from the operating frequency of reception and thereby simplify the filter circuit. However, this technical solution has the following disadvantages:

- with an increase in the IF, the local oscillator frequency and its phase noise increase, which does not allow to obtain a high value of the dynamic range for blocking the receiver;

- the IF filter circuit is complicated;

- with an increase in the frequency of the inverter, the characteristics of the amplifiers in the IF and ADC paths deteriorate to a large extent, stability under the influence of external factors deteriorates, which does not allow obtaining high sensitivity and susceptibility values for blocking the receiver.

Another well-known technical solution is to apply a reception scheme with transfer to zero frequency using a quadrature mixer (Belorussov DI, Shadenkov Yu.A. “Modern methods of digital signal processing in radio receivers.” “Special equipment”, No. 5, 2011 city, UDC: 621.39).

Its main disadvantage is the large intrinsic noise of the receiver in the band up to several tens of kilohertz from the center of the received signal, the so-called flicker noise. As a result, such a device works well with broadband signals, but has significant limitations when receiving narrowband signals.

The prior art various devices that use certain features of the claimed technical solution, however, the functional blocks and structural elements in these technical solutions have other connections.

So, in the certificate of approval of the type of measuring instruments "Spectrum Analyzers FSW43", reg. No. 53782-13 a device for signal analysis is disclosed, the principle of which is based on the heterodyne transfer of the test signal to an intermediate frequency (IF) and its subsequent processing using an analog-to-digital converter (ADC) with a digital processing unit. In the low-frequency region, a direct signal to the ADC is provided bypassing the mixer.

It is known to use a block of sub-octave filters to filter the received signal from interference and higher harmonics of the signal in the receiver (RF patent RU 88886, published November 20, 2009).

The problem being solved by the utility model is to improve the technical and operational characteristics of the transceiver device.

The technical result achieved is an increase in the dynamic range, a decrease in noise, an improvement and simplification of filtering, and, as a result, a decrease in size and a simplification of the device, an increase in the overall reliability of the device while maintaining high reception selectivity parameters.

To solve the problem with achieving the claimed technical result, the transceiver device according to the claimed utility model comprises an antenna, a block of switched sub-octave filters, a receive / transmit switch, a first low-noise amplifier (LNA), a first block of switched bandpass filters, a mixer, a second low-noise amplifier of an intermediate frequency LNA ( IF), the second block of switchable bandpass filters for the analog-to-digital converter (ADC), the driver of the analog-to-digital converter, ADC, analog-to-digital an ADC converter, connected in series, a power amplifier of the transmitting path, connected through the second input of the receive / transmit switch and a block of switched sub-octave filters to the antenna. The device is equipped with a frequency synthesizer, programmable divider and mixer switch. A frequency synthesizer through a programmable divider forming a local oscillator is connected to the second input of the mixer. The mixer switch is connected by the input to the output of the first block of switched bandpass filters, and the output is connected to the input of the second low-noise amplifier of the LNA of the intermediate frequency (IF).

These advantages, as well as the features of the present utility model are explained below with the help of the preferred embodiment with reference to the figures.

FIG. 1 depicts a functional diagram of the claimed transceiver.

FIG. 2 is the same as FIG. 1, with two keys controlling the connection of the mixer switch.

The claimed transceiver device with a wide dynamic range and low noise includes an antenna 1, a block 2 switchable sub-octave filters, a switch 3 transmit / receive, the first low-noise amplifier 4 (first LNA), the first block 5 of switched bandpass filters, mixer 6, the second low-noise amplifier 7 ( the second LNA) of an intermediate frequency (IF), the second block of 8 switchable bandpass filters for an analog-to-digital converter (ADC), driver 9 of an analog-to-digital converter, ADC, analog-to-digital converter 10, ADC, carefully connected by their outputs to the inputs of the subsequent indicated blocks, as shown in FIG. 1. The transmit power amplifier 11 is connected through the second input of the receive / transmit switch 3 and the switchable sub-octave filter unit 2 to the antenna 1. The device is equipped with a frequency synthesizer 12, a programmable divider 13 forming a local oscillator, and a mixer switch 14. A frequency synthesizer 12 through a programmable divider 13 is connected to the second input of the mixer 6. The mixer switch 14 is connected to the input to the output of the first block 5 switchable bandpass filters, and the output to the input of the second LNA 7 of the intermediate frequency (IF).

The letters in FIG. 1 are marked: A - antenna input / output of block 2; B - input of block 2 in transmission mode; In - the input of the switch unit 3 in the receive mode; G - the second input of the switch 3 in transmission mode.

The transceiver operates as follows.

In the transmission mode, the transmit power amplifier 11, connected through the second input G of the receive / transmit switch 3 to the block 2 of switched sub-octave filters, provides a signal to the antenna 1 for radiation to space. In this case, the switch 3 disconnects the receiving path, opening the input circuit of the first LNA 4 of the receiver. Block 2 switchable sub-octave filters in the transmission mode performs the function of a low-pass filter, which serves to suppress the harmonic components of the output RF signal of the transmitting path.

In reception mode, the radio frequency signal from antenna 1, passed through block 2 of switchable sub-octave filters, which partially suppresses the control panel signals and, thus, reduces the requirements for the subsequent cascade of the main panel suppression of block 5 switchable band-pass filters and obtain a more compact device circuit with greater repeatability and stability.

Block 2 is connected by the switch 3 to the input of the first LNA 4. In this case, the switch 3 disconnects the input circuit of the amplifier 11 (second input Г of the switch 3). After the first LNA 4 and the first block 5 of switched bandpass filters, which suppresses the signals of the side receiving channels, the signal is supplied to the mixer 6. In the process of mixing the frequencies of the useful radio frequency signal and the local oscillator signal generated by the frequency synthesizer 12 through a programmable divider 13, the output of the mixer 6 is formed intermediate frequency. Programmable divider 13 allows you to switch the frequency of the local oscillator from "high" frequency to "lower" so that the modulus of the difference between the frequency of the local oscillator and the operating frequency of the receiver is kept equal to the IF. At those operating frequencies of the receiver, where this does not lead to the appearance of large unsuppressed combinational control panels, the conditions of which are described below, this reduces the phase noise of the local oscillator and, accordingly, increases the dynamic range for blocking the receiver at a rate of 6 dB to reduce the local oscillator frequency by 2 times.

The intermediate frequency signal from the mixer 6 is further amplified by the second LNA 7, filtered by the second block of 8 switched bandpass filters, amplified by the driver 9, which works as a buffer and a low-pass filter (LPF), which reduces the overall noise level, digitizes the ADC 10 and goes further to digital signal processing circuit (DSP) for demodulation.

The receivers operating according to the superheterodyne reception scheme, due to the nonlinearity of mixer 6, have the so-called secondary reception channels: the output frequency of the inverter occurs when the nth harmonic of the local oscillator and the mth harmonic of the interference signal input to the mixer 6 are converted. As a result, at different m, n at the intermediate frequency, the input signals of the whole set of frequencies Fnm are converted:

where n = 0, ± 1, ± 2, ...; m = ± 1, ± 2, ...; Fg is the frequency of the local oscillator; FPC - intermediate frequency.

These frequencies form a set of receiving channels, and only one of these channels is useful, and the rest are secondary. The signals of the side receiving channels (PKP) must be suppressed before the input of mixer 6. This is done by the first block 5 of switched bandpass filters. For various values of m, n, the frequencies of the control panels can be both above and below the frequency of the main reception channel. For receivers of a wide range of frequencies, this leads to the fact that for effective suppression of the control panel, the first block 5 must have a very large number of links of complex filters. For broadband receivers with a large frequency band of simultaneous viewing, these filters should have an appropriate overlap, which further increases the number and order (complexity) of filters.

In the claimed technical solution, one or several sufficiently low IFs are used, while the upper limit of the IF is selected based on the ability of the ADC 10 to digitize the signal with the least distortion and noise, the ability of the local oscillator to provide sufficiently low phase noise corresponding to the required dynamic blocking range, as well as the stability of the characteristics of the path elements on the inverter after the mixer 6 - LNA 7, block 8 of switched bandpass filters, driver 9. The lower limit of the inverter must be high enough to provide the required bandwidth of the broadband receiver, and not lead to unreasonably high complexity of the filters of block 5 for the control panel at values m = ± 1.

где n=0, 1, 2, и, как следствие, значительно уменьшается количество и упрощается конструкция фильтров блока 5.The gain of the first LNA 4 is selected small, only providing a given noise figure and path sensitivity (in the useful signal band) to the mixer 6. At the same time, the blocking signals are also slightly amplified, and the signals of the lowest possible amplitude are fed to the mixer 6. Under such conditions, strong suppression (more than 75 dB for a typical receiver with a sensitivity of 1 μV) of the combinations of harmonics of the local oscillator and harmonics of the interference signal for m = 2, 3, ... occurs in mixer 6. As a result, the number of frequency bands Fпкп PKP is significantly reduced, which required to suppress:

where n = 0, 1, 2, and, as a result, the number is significantly reduced and the design of the filters of block 5 is simplified.

To compensate for the lack of path amplification in the device, a second low-noise amplifier 7 (LNA) of an intermediate frequency (IF) is used. By using the LNA not only at the input of the receiver, but also in the cascade on the inverter, two goals are achieved: a low noise figure ensures the given sensitivity of the receiving path as a whole, and due to the fact that the second LNA 7 is located in the constant IF path, it becomes possible to choose electronic components with a large dynamic range so that the dynamic range of the receiver is ultimately not limited to an amplifier.

Since low IFs are used, the operating modes of driver 9 and ADC 10 also have better stability, dynamic range, and noise characteristics at relatively low frequencies.

Connecting the receive / transmit switch 3 not at antenna input A, but after block 2 of switched sub-octave filters for the transmitting path, leads to the fact that the control panels are additionally suppressed in the receiver path by the same filters, which also makes it possible to significantly simplify the switched bandpass filters of the first block 5.

For low operating frequencies at the input of the receiver falling into the working areas for direct digitization of the ADC 10, the switch 14 connected to the output of the first block 5 of switched bandpass filters and to the input of the second LNA 7 switches the signals bypassing the mixer 6. Thus, the claimed device eliminates for the indicated frequencies, mixer 6 and all associated control panels, which eliminates the requirement of their suppression by the first block 5, simplifying it.

At each point in time in the inventive device (Fig. 2) either a mixer 6 or a switch 14 is turned on. This is controlled by a control unit, which is not shown in the diagram, which, for example, switches the filters in the filtering units 2, 5, supplies power to the amplification stages the first and second LNA 4, 7, etc., but does not apply directly to the transmitting and receiving paths. Two keys 15, 16 are used, which, in the mode of connecting the switch 14, are connected by signals from the control unit to the output of block 5 and to the input of the second LNA 7 through switch 14, disconnecting the local oscillator and mixer 6. And in the mode of operation with the local oscillator, two keys 14, 15 are connected the input of the mixer 6 to the output of block 5, and the output of the mixer 6 to the input of the second LNA 7.

A low value of the intermediate frequency allows for a wide range of operating reception frequencies to select with the help of a programmable divider 13 the lower value of the local oscillator frequency (Fg <Fpr) without complicating the switched bandpass filters of the filter unit 5. Using a lower frequency local oscillator reduces its phase noise and allows you to further increase the dynamic range of the receiver blocking.

A transceiver was tested with the following parameters.

At a sampling frequency of the ADC of 150 MHz, the IF was chosen to be 110 MHz or 185 MHz. The characteristics of the first LNA 4 had the following values: a gain of 25 dB, a noise figure of 1.5 dB. Characteristics of the second LNA: gain of 20 dB, noise figure of 1.7 dB. The passive mixer 6 was characterized by a loss of about 7 dB. As tests showed, the claimed technical solution made it possible to implement a transceiver device that overlaps the operating frequencies of the DKMV, MB and parts of the UHF band (1.5-520 MHz), having a sensitivity of 1 μV, a dynamic range for blocking more than 70 dB and suppression of the control panel more than 70 dB during the entire frequency range with a bandwidth of simultaneous review of the transceiver up to 40 MHz. To ensure a wide band of the product up to 40 MHz in the operating frequency range, it was necessary to use 9 sub-octave transmitter filters, while the block of switchable PKP filters in the receiving path contains only 6 filters. This receiver, along with the transmission path, forms a transceiver, which, together with other modules (control module, navigation module, liquid crystal display and keyboard module, power battery) is located in the dimensions of a typical portable radio station.

The most successfully declared transceiver with a wide dynamic range and low noise is applicable in various fields of radio engineering, mainly in communications, detection, telecommunications, and radar.

Claims (1)

A transceiver comprising an antenna, a switchable sub-octave filter unit, a receive / transmit switch, a first low-noise amplifier, a first switch-bandpass filter, a mixer, a second low-noise amplifier, a second switchable band-pass filter, a driver, an analog-to-digital converter connected in series, a power amplifier transmission path, connected via the second input of the receive / transmit switch and a block of switched sub-octave filters to the antenna, frequency synthesizer, programmer my divider constituting a local oscillator and a mixer switch, wherein the frequency synthesizer through a programmable divider coupled to the second input of the mixer, and the mixer input of the switch is connected with the output of the first block of switchable bandpass filters, and output - with an input of the second low-noise amplifier.

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