RU2593928C1 - Radio receiver for digital active phased antenna array - Google Patents

Abstract

FIELD: radio engineering and communications.

SUBSTANCE: invention relates to radio receiving devices of digital multielement active phased antenna arrays (AFAR). Radio receiving device consists of N channels, each channel has series-connected high frequency amplifier, input of which is input channel, a mixer, second input of which is heterodyne channel input and an intermediate frequency amplifier (IFA), control input of which is control input of channel, and output is output channel and is differential. Output of amplifier, first input of which is heterodyne input of device, is connected to series-connected directional coupler (DC) and power divider, N outputs of which are connected with heterodyne inputs of channels of device. Input of amplitude detector (AD) is connected to second output of DC, and output is connected to input of analogue-to-digital converter (ADC), output of which is connected to input of data control unit. Bidirectional control input of control unit is control input of device, first output is connected to control input of amplifier, rest of control outputs are connected to control inputs of channels of device.

EFFECT: simplified adjustment of radio receiving device and possibility of its use in digital multielement AFAR with components in space.

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Description

The invention relates to radio receivers of multi-element active phased array antennas (AFAR).

Known radio receiver (RPU) [1 - Reference radar. Editor M. Skolnik. Volume 3. "Radar devices and systems." M .: "Soviet Radio". 1979, p. 136], comprising a high-frequency amplifier, a local oscillator, and a coherent receiver, including a quadrature frequency converter with heterodyning to zero frequency, a low-pass filter (low-pass filter), analog-to-digital converters (ADCs), and a phase shifter.

The disadvantages of the known device include:

- excessive complexity, since quadrature frequency conversion using two mixers is used to convert the received signal to zero frequency, and two ADCs must be used to sample the received signal, which significantly increases the cost of multi-element digital AFAR equipment, since the number of ADCs corresponds to the number of RPU channels.

Known radio receiver of a coherent radar station [3 - RF Patent No. 2189054, “Radio receiver of a coherent radar, published 2002.09.10], closest to the claimed device and taken as a prototype containing a local oscillator, two digital adders, N reception channels, each from an analog adder, coherent receiver and phase shifter. In this case, the coherent receiver contains a high-frequency amplifier, the output of which is connected to the input of the quadrature frequency converter, each arm of which contains a mixer, a low-pass filter (LPF), and an analog-to-digital converter, the output of which is the output of the receiver. The disadvantages of the prototype include:

- excessive complexity, since quadrature frequency conversion using two mixers is used to convert the received signal to zero frequency, and two ADCs must be used to sample the received signal, which significantly increases the cost of multi-element digital AFAR equipment, since the number of ADCs corresponds to the number of RPU channels;

- high requirements for the identity of the phase and amplitude characteristics of the elements used in the prototype scheme of the quadrature frequency conversion to zero frequency. So the non-identical amplitude characteristics of the arms of the quadrature frequency converter, each of which contains a mixer, low-pass filter and amplifier, the output of which is connected to the ADC (the amplifier is not shown in the prototype diagram, but it is necessary to amplify the received signal to the level necessary for the ADC to work), in 1 dB causes the appearance of spurious components in the spectrum of the digital signal with a level of minus 40 dB relative to the main signal [2 - V. Lityuk, L. V. Lityuk Methods of digital multiprocessor processing of ensembles of radio signals. - M .: Solon-press. 2007, p. 41];

- the inability to adjust the local oscillator signal at the input of the radio receiver, which makes it impossible to use the prototype circuit in digital multi-element AFAR with spacing of the components in space.

The task to which the invention is directed is to simplify the configuration of a radio receiver and to ensure the possibility of its use in digital multi-element AFARs with diversity of components in space.

To achieve this objective, a digital AFAR radio receiver is proposed, including N channels, each of which includes a high frequency amplifier (UHF) and a mixer in series, the second input of which is the channel heterodyne input.

According to the invention, an intermediate frequency amplifier (IFA) is connected to the mixer output, the output of which is a channel output and is made differential, and its control input is a channel control input, one of the N outputs of the power divider is connected to the channel heterodyne input, the input of which is connected to the first output directional coupler, while the input of the directional coupler is connected to the output of the amplifier, the first input of which is the heterodyne input of the device, and the second output of the directional coupler is li ne through the amplitude detector to the ADC input, whose output is connected to an input control block data which bidirectional control input is a control input device, the first control unit output is connected to the control input of the amplifier, and the remaining control outputs connected to control inputs of the device channels.

A comparative analysis of the claimed device and prototype shows that the claimed device is characterized in that:

- in the prototype, a quadrature conversion of the carrier frequency of the input signal to zero frequency is carried out using two mixers, which requires two ADCs to be connected to such a radio receiver, which complicates the receiving part of the AFAR and increases the cost of the AFAR as a whole, while in the proposed device the carrier is converted the frequency of the received signal in the IF band, with further sampling of the IF signal using one ADC instead of two. For multi-element digital AFARs, the savings reach, depending on the number of receiving channels, several hundred pieces of ADC chips;

- used in the prototype scheme of the quadrature frequency conversion to zero frequency requires high identity of the phase and amplitude characteristics of the low-pass filter, mixers and amplifiers. While in the proposed device, the use of one amplifier with the subsequent connection of one ADC eliminates these requirements and simplifies the configuration of the radio receiver;

- in the prototype, a single line is used to connect to the ADC, while the proposed device uses differential outputs, which provides a significant reduction in the level of induced noise at the ADC input;

- in the prototype there is no adjustment of the signal level of the local oscillator, while in the proposed device the signal level of the local oscillator is regulated.

The combination of distinctive features and properties of the proposed device from the literature is not known, therefore, it meets the criteria of novelty and inventive step.

In FIG. 1 shows a structural diagram of the proposed radio receiver.

In FIG. 2 is a structural diagram of a high frequency amplifier.

In FIG. 3 shows the design of the proposed device.

The radio receiving device (Fig. 1) consists of N channels 1, each channel contains UHF 2 connected in series, the input of which is the channel input, a mixer 3, the second input of which is the channel heterodyne input, and an intermediate frequency amplifier (IF) 5, the control input of which is the control input of the channel, and the output is the output of the channel and is made differential.

The output of amplifier 6, the first input of which is the heterodyne input of the device, is connected to a series-connected directional coupler (HO) 7 and a power divider 8, the input of which is connected to the first output of HO 7, and N outputs are connected to the heterodyne inputs of the device channels.

The input of the amplitude detector (HELL) 9 is connected to the second output of the HO 7, and the output of the HELL 9 is connected to the input of the ADC 10, the output of which is connected to the data input of the control unit (BU) 11.

The bi-directional control input BU 11 is the control input of the device, its first output is connected to the control input of the amplifier 6, and the remaining control outputs are connected to the control inputs of the device channels.

UPCH 5 (Fig. 2) consists of a series-connected band-pass filter 12, a limiter 13 and a low-noise amplifier (LNA) 14.

The power divider 8 is made on one of the layers of the printed circuit board 15 (not shown in Fig. 3). The construction of the power divider 8 corresponds to the description of the construction of the dividers given in [4 - Bova NT, Efremov VV and other microwave electronic devices. M .: Kiev. "Technics". 1984. 184 p.].

The control unit 11 is designed to receive control commands received at the control input of the device, receive data of measuring the level of the input signal from the ADC 10, set the transmission coefficients of the amplifier 6 and UPCH 5 and can be performed based on a microprocessor, the structure is similar to that given in [5 - Digital filters and signal processing devices on integrated circuits / F.B. Vysotsky, V.I. Alekseev et al. M .: Radio and communications. 1987. - Page 126], based on the microprocessor structure described in [6 - Ugryumov E. Digital circuitry. St. Petersburg: BHV-Petersburg. 2004, fig. 5.1] or on the FPGA chip.

ADC 10 is designed to convert the received signal to digital samples. For its implementation, you can use, for example, a chip type AD7276 manufactured by Analog Devices [website www.analog.com].

HELL 9 is designed to highlight the envelope of the local oscillator signal. For its implementation, you can use, for example, a chip type AD8319 manufactured by Analog Devices [website www.analog.com].

In order to protect against electromagnetic interference during the transmission of the output signal of the inverter 5 for further processing, the transmission line is made differential. Conversion to a differential form can be performed, for example, by installing a transformer of the JTX-2-10T type manufactured by Mini-circuits in the OCH 5 [the site www.minicircuits.com].

The proposed radio receiver operates as follows. The received signal is fed to the input of UHF 2, where it is filtered in the bandpass filter 12, limited by the level in the limiter 13 and amplified in the LNA 14, then fed to the mixer 3, where its frequency f _{c is} converted to the IF range according to the formula f _IF = f _c -f _get with the lower tuning of the local oscillator or by the formula f _IF = f _get -f _c with the upper tuning of the local oscillator. Next, the signal is amplified and filtered in the amplifier 5. The amplification and filtering are performed in a differential form, which significantly reduces interference, upon further transmission of the signal to the input of an external ADC (not shown in Fig. 1), which will be connected to this channel of the radio receiver.

The local oscillator signal level Fget, which is input to the heterodyne input of the radio receiver, is amplified in amplifier 6 with an adjustable transmission coefficient, passes through HO 7 and fed to a power divider 8, where it is divided into N outputs and fed to the heterodyne inputs of the mixers 3 of all channels of the device.

Since the mixers 3 are designed to operate at a certain level of the local oscillator signal, the proposed device adjusts the local oscillator signal in order to maintain its level within the specified limits. For this, the level of the incoming local oscillator signal is measured at the second output of HO 7 using AD 9, which selects the envelope of the local oscillator signal and ADC 10, which forms the envelope samples. The measurement results are fed to the data input BU 11, which compares them with the lower and upper threshold values of the permissible change in the level of the local oscillator signal. When the measured value passes through the upper or lower threshold value, the gain of the amplifier 6 is adjusted through its control input to maintain the local oscillator signal level within the specified limits.

The control unit 11 can also set the transfer coefficient of the converter 5 according to an external command coming to the control input of the device.

The design of the radio receiving device (Fig. 3) is a multilayer printed circuit board 15 of a rectangular shape, on the upper side of which surface-mounted components of the device are made. Groups of elements 16 related to the i-th channel are separated by housing printed conductors 17 and are located along the long side of the rectangular printed circuit board.

Elements related to measuring the level of the input signal and adjusting its level - amplifier 6, НО 7, АД 9, and ADC 10 are grouped together on section 18 of printed circuit board 15. Section 18 and control unit 11 are separated by case printed conductors 17. From above on printed circuit board 15 a screen is installed (not shown in Fig. 3), the lower surface of the walls of which is pressed against the case printed conductors 17 of the printed circuit board 15 with screws (not shown in Fig. 3) through the holes 19. For connection with external devices, the cut-in connectors 20 are used.

The proposed radio receiving device provides the construction on its basis of digital multi-element AFAR for coherent radar.

Compared with the prototype, the proposed radio receiving device simplifies tuning of the radio receiving device by eliminating quadrature frequency conversion to zero frequency, which requires high identical phase and amplitude characteristics of the low-pass filter, mixers and amplifiers in quadrature channels, and also allows its use in multi-element diversity antenna arrays with diversity components in space due to the ability to adjust the level of the local oscillator signal. In addition, the cost of the radio receiver part of the AFAR is reduced by reducing the number of ADC chips.

The performance of the proposed device was tested on the layout of a digital AFAR. Tests showed the coincidence of the obtained characteristics with the calculated ones.

Claims (1)

A radio device of a digital active phased antenna array, including N channels, each of which includes a high-frequency amplifier and a mixer connected in series, the second input of which is a channel heterodyne input, characterized in that an intermediate frequency amplifier is connected to the mixer output, the output of which is the channel output and is made differential, and its control input is the control input of the channel, one of the N outputs of the power divider is connected to the heterodyne input of the channel, which is connected to the first output of the directional coupler, while the input of the directional coupler is connected to the output of the amplifier, the first input of which is the heterodyne input of the device, and the second output of the directional coupler is connected through an amplitude detector to the input of the analog-to-digital converter, the output of which is connected to the data input of the unit control, bi-directional control input of which is the control input of the device, the first output of the control unit is connected to the control input of the amplifier, and about tal control outputs connected to control inputs of the device channels.

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