JP6649217B2 - Received signal amplifier and transceiver - Google Patents

Description

  Embodiments of the present invention relate to a reception signal amplifier and a transmission / reception device.

  There has been proposed a transmission / reception module aiming at improving the noise figure while having the function of the transmission / reception module of the transmission / reception module and further downsizing the circuit itself (for example, Patent Document 1).

JP 2007-074420 A

  FIG. 3 is a diagram showing a circuit configuration of a microwave low-noise amplifier used for a passive radar receiving module. In the figure, the output of an antenna 11 is input to a first RF switch 12. The first RF switch 12 is a high-frequency switch having an SPDT (Single Pole, Dual Throw) structure, and selectively switches between two outputs.

  A first output of the first RF switch 12 is provided to the low noise amplifier 13 and the anode of the limiter diode 14. The cathode of the limiter diode 14 is grounded. The second output of the first RF switch 12 is provided to the second RF switch 15.

  The low noise amplifier 13 uses gallium arsenide (GaAs) and supplies an amplified output to the second RF switch 15. The second RF switch 15 is a high-frequency switch having an SPDT (Single Pole, Dual Throw) structure, and selectively switches the two inputs to output.

  In the circuit configuration described above, when the antenna 11 receives an RF signal, the power input to the low-noise amplifier 13 via the first RF switch 12 reaches a certain level as shown in FIG. Although rising, the first RF switch 12 switches to the expansion system near the limiting level of the limiter diode 14, and becomes "0 (zero)".

  On the other hand, the extension-system RF signal output from the first RF switch 12 to the second RF switch 15 rises at the limiting level of the limiter diode 14 as shown in FIG. And rises in proportion to the rise in antenna input power.

  As described above, the circuit shown in FIG. 3 employs a configuration that ensures low-noise performance of the low-noise amplifier 13 and avoids saturation due to an increase in the RF signal.

  However, in the circuit configuration of FIG. 3, the RF signal received by the antenna 11 is switched to the extension system, so that the RF signal passes through a path bypassing the low noise amplifier 13. Therefore, the S / N ratio corresponding to the antenna input in the entire circuit deteriorates at a level higher than the limiting level of the limiter diode 14 as shown in FIG. 4C.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to maintain a high S / N ratio regardless of the level of an RF signal received by an antenna. An object of the present invention is to provide a reception signal amplifier and a transmission / reception device.

  A reception signal amplifier according to an embodiment includes a first low noise amplifier that amplifies and outputs an input RF signal, a limiter diode having an anode connected to an input terminal of the first low noise amplifier, and a cathode grounded. And a second low-noise amplifier for amplifying and outputting an input RF signal, and an RF signal received by an antenna being input to a first terminal, and an input terminal of the first low-noise amplifier being connected to a second terminal. A circulator connected to an input terminal of the second low-noise amplifier and an input terminal of the second low-noise amplifier connected to a third terminal; and a combiner for combining outputs of the first low-noise amplifier and the second low-noise amplifier. Prepare.

FIG. 1 is a diagram showing a circuit configuration when applied to a microwave low-noise amplifier used in a passive radar receiving module according to one embodiment. FIG. 2 is a diagram showing signal waveforms of the circuit of FIG. 1 according to the first embodiment. The figure which shows the circuit structure of the microwave low noise amplifier used for the receiver module for passive radar. FIG. 4 is a diagram illustrating signal waveforms of the circuit in FIG. 3.

  Hereinafter, an embodiment applied to a microwave low-noise amplifier used in a receiving module for a passive radar will be described in detail with reference to the drawings.

[Constitution]
FIG. 1 is a diagram showing a circuit configuration of a microwave low noise amplifier. In the figure, an output of an antenna 21 is input to a first terminal of a circulator 22. A second terminal of the circulator 22 is connected to an anode of the limiter diode 23 and an input terminal of the low noise amplifier 24. The cathode of the limiter diode 23 is grounded.

  The low noise amplifier 24 uses gallium arsenide (GaAs) to amplify an input RF signal and output the amplified RF signal to the combiner 26.

  A third terminal of the circulator 22 is simply connected to the input of the low noise amplifier 25. The low-noise amplifier 25 uses gallium nitride (GaN) and has higher power handling characteristics than the low-noise amplifier 24. The low-noise amplifier 25 amplifies an input RF signal and sends the amplified RF signal to the combiner 26. Output.

  The combiner 26 combines the outputs of the low-noise amplifier 24 and the low-noise amplifier 25 and outputs the combined output to the next-stage receiving circuit system (not shown).

[motion]
In the circuit configuration described above, when the antenna 21 receives a microwave RF signal, the input power V21 given to the limiter diode 23 and the low-noise amplifier 24 via the circulator 22 is indicated by a broken line in FIG. As shown, the level rises to a certain level, but when the level exceeds the limiting level of the limiter diode 23, it is suppressed to a certain level by the limiter diode 23.

  When the input power V21 further rises from a state exceeding the limiting level of the limiter diode 23, the impedance of the limiter diode 23 changes to a short-circuit state in accordance with the RF signal. Is increased.

  However, the signal component reflected by the circulator 22 disposed between the limiter diode 23 and the antenna 21 is output not to the antenna 21 but to the input terminal side of the low noise amplifier 25, and the input power V22 of the low noise amplifier 25 is output. Will increase by that amount.

  That is, the input power V22 reflected by the limiter diode 23 and applied to the low-noise amplifier 25 via the circulator 22 increases as shown by the solid line in FIG. Therefore, even in a region exceeding the limiting level of the limiter diode 23, as described above, the low-noise amplifier 25 using gallium nitride (GaN) having high power handling characteristics as shown by a solid line in FIG. The amplification operation with low noise is continuously performed, and a situation in which the S / N ratio decreases can be reliably avoided.

  In FIG. 2B, the wavy line indicates the S / N ratio when the low noise amplification process is not performed in the region exceeding the limiting level of the limiter diode 23, also shown in FIG. 4C. It is shown for reference.

[Effects]
As described above, in the circuit according to the present embodiment, even in a region where the RF signal obtained by reception exceeds the limiting level of the limiter diode 23, the RF signal obtained on the side of the second low-noise amplifier 25 provided together with the first low-noise amplifier 24 is used. Subsequently, since the amplification operation with low noise is performed, it is possible to maintain a high S / N ratio according to the entire level of the RF signal.

  In addition, in the present embodiment, the reflected wave generated by the limiter diode 23 is output not to the antenna 21 but to the low noise amplifier 25, so that the VSWR (voltage standing wave ratio) at the antenna 21 is improved. As a result, it is possible to prevent the antenna 21 from deteriorating due to the input voltage at the antenna 21.

  The low-noise amplifier 25 to which a higher level of power is provided as compared with the low-noise amplifier 24 is configured by using gallium nitride (GaN) having higher power resistance than the low-noise amplifier 24. The operation of the entire circuit can be stabilized.

  In addition, even when the circuit shown in FIG. 1 is used as a part of a receiving circuit and a transmitting / receiving circuit including a transmitting circuit sharing the antenna 21 is constructed, the reflection generated in a part of the receiving system can be realized. The wave does not reach the antenna 21 and is processed as a low-noise reception signal.

  As a result, since the reflected wave generated in the receiving system does not propagate to the circuit of the transmitting system via the antenna 21 as a result, the VSWR between the transmitting and receiving operations of the antenna 21 is kept good, and the antenna 21 is It is possible to operate without deterioration.

  In the above embodiment, the case where the present invention is applied to the microwave low noise amplifier used for the passive radar receiving module has been described. However, the frequency band of the target RF signal and the material forming the low noise amplifiers 24 and 25 are described. It is not limited.

  Although one embodiment has been described, the embodiment is presented as an example and is not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

21: antenna, 22: circulator, 23: limiter diode, 24: (first) low-noise amplifier, 25 ... (second) low-noise amplifier.

Claims (3)

A first low noise amplifier that amplifies and outputs an input RF signal;
A limiter diode having an anode connected to an input terminal of the first low noise amplifier and a cathode grounded;
A second low-noise amplifier that amplifies and outputs an input RF signal;
An RF signal received by an antenna is input to a first terminal, an input terminal of the first low-noise amplifier is connected to a second terminal, and an input terminal of the second low-noise amplifier is connected to a third terminal. Connected circulator,
A combiner that combines the outputs of the first low-noise amplifier and the second low-noise amplifier.   2. The reception signal amplifier according to claim 1, wherein the second low noise amplifier uses an amplifier having higher power handling characteristics than the first low noise amplifier. 3.   A transmission / reception device comprising the reception signal amplifier according to claim 1 in a reception system circuit, and further comprising a transmission system circuit sharing the antenna.