Beamforming circuit

Abstract

This invention provides a beamforming circuit that performs beamforming while suppressing beam angle broadening. [Solution] A beamforming circuit 100 for beamforming a faceted array antenna including a plurality of antenna elements 11 arranged in a row at equal intervals, comprising: a plurality of LO phase shifters 26 that shift the phase of an input LO signal by a variable phase shift amount; a plurality of IF phase shifters 23 that delay the phase of frequency components included in the input IF signal as the frequency is lower than the center frequency, and advance the phase as the frequency is higher than the center frequency; and a plurality of mixers 29 connected to the plurality of antenna elements 11, the plurality of LO phase shifters 26, and the plurality of IF phase shifters 23, wherein the LO phase difference between the plurality of mixers 29 is set to a variable phase shift amount by the plurality of LO phase shifters 26, and the phase shift characteristics of the IF phase shifters 23 change according to the variable phase shift amount of the LO phase shifters 26.

Description

[Technical Field]

[0001] The present invention relates to a beamforming circuit, and more particularly to a beamforming circuit suitable for performing broadband communication with a phased array antenna. [Background technology]

[0002] In wireless communication, the received power decreases on the order of the square of the RF (radio frequency) signal wavelength. Therefore, when the RF frequency is in the millimeter wave band of 20-100 GHz, and even higher in the subterahertz band of 100-300 GHz or the terahertz band, the received power becomes extremely small. This can be improved by increasing the transmitted power or antenna gain, but there are limits to this. Therefore, beamforming is performed to increase antenna gain by arranging multiple antennas in an array and adjusting the phase of the radio waves transmitted and received by each antenna to improve directivity (see, for example, Non-Patent Documents 1 and 2).

[0003] In array antennas, antenna elements are arranged at half-wavelength pitches of radio waves. In the 300 GHz band, antenna elements need to be arranged at approximately 500 μm pitches. Therefore, if an array antenna with antenna elements arranged in a two-dimensional grid is to be used in a transceiver operating in the 300 GHz band, the transceiver circuit must be crammed into an area of ​​approximately 500 μm square. To address this problem, the inventors have proposed a 300 GHz band array antenna device in which only the mixer and its peripheral circuits are concentrated in a narrow area, and other circuit elements are placed in the remaining area (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2023 / 162887 [Non-patent literature]

[0005] [Non-Patent Document 1] Ahmed, Amr et al. “140-GHz 2-D Scalable On-Grid 8x8-Element Transmit-Receive Phased Arrays With Up / Down Converters Demonstrating a 5.2-m Link at 16 Gbps.” IEEE Transactions on Microwave Theory and Techniques 72 (2024): 2852-2868. [Non-Patent Document 2] Yoshida, Takeshi et al. “A 2D Beam-Steerable 252-285-GHz 25.8-Gbit / s CMOS Receiver Module.” 2023 IEEE Asian Solid-State Circuits Conference (A-SSCC) (2023): 1-3. [Overview of the project] [Problems that the invention aims to solve]

[0006] Figure 7 illustrates the beamforming principle of a phased array antenna. It describes the radio waves radiated from two antenna elements arranged in the same plane. Each antenna element radiates an RF signal, i.e., a radio wave, obtained by upconverting the IF (intermediate frequency) signal with the LO (local oscillator frequency) signal in a mixer. Let P0 be the radiation point of the RF signal radiated from the right-hand antenna element in the figure, and P1 be the radiation point of the RF signal radiated from the left-hand antenna element. Both mixers receive in-phase IF signals, and the LO signal from the left mixer has a phase difference of θ compared to the LO signal from the right-hand mixer. LO Let's assume it has progressed that far.

[0007] Since the phase of the RF signal is the sum of the phase of the IF signal and the phase of the LO signal, the RF signal of the left antenna element will be θ greater than that of the right antenna element. LO The phase is advanced by θ from P1 to P0.LO The RF signal is radiated earlier by a time corresponding to the time difference. The RF signal has a bandwidth, and due to the difference in the wavelengths of each frequency component within the bandwidth, there is a difference in the propagation distances of each frequency component during the time difference. Let the center frequency of the RF signal be f0 and the half-bandwidth be f BW / 2 . Then, while f0 propagates from P1 to point P C , the lower frequency f0 - f with a longer wavelength than f0 BW / 2 propagates to a point P LSB farther away, and the upper frequency f0 + f with a shorter wavelength than f0 BW / 2 propagates to a point P USB closer.

[0008] The wavefronts of each frequency component of the RF signal radiated from the two antenna elements are represented as the base of a right triangle with the line segment P1 - P0 as the hypotenuse and the line segment connecting P1 and each of the above points as one side. That is, the straight line including the line segment P0 - P C is the wavefront W C of f0, the straight line including the line segment P0 - P LSB is the wavefront W BW / 2 of f0 - f LSB , and the straight line including the line segment P0 - P USB is the wavefront W BW / 2 of f0 + f USB . The direction orthogonal to these wavefronts is the direction of the beam of each frequency component, and the inclination of the beam with respect to the normal of the antenna surface including the line segment P1 - P0 is the beam angle.

[0009] The beam B C of f0 is inclined by θ BF with respect to the normal of the antenna surface. When the LO phase difference between the mixers is θ LO , the beam angle is controlled to θ BF . On the other hand, the inclination of the beam B BW / 2 of f0 - f LSB is smaller than θ BF , and the inclination of the beam B BW / 2 of f0 + f USB is larger than θ BF . Thus, due to the bandwidth of the RF signal, there is a certain spread in the beam angle of the phased array antenna.

[0010] Figure 8 is a graph showing the relationship between the LO phase difference between mixers and the beam angle. For example, by changing the LO phase difference from 0 to 90 degrees, the beam angle of a 275 GHz RF signal can be controlled within a range of 0 to 30 degrees. Here, as the LO phase difference increases, the beam angle increases, and the beam angle broadening due to the bandwidth of the RF signal also increases. Furthermore, as the bandwidth shown in parentheses widens to 10 GHz, 15 GHz, and 30 GHz, the beam angle broadening increases even further.

[0011] If the beam angle of an RF signal is broadened, as the communication distance increases, the lower and upper frequency beams will deviate significantly from the center frequency beam before reaching the receiver. As a result, frequency components far from the center frequency are attenuated relatively more significantly than the center frequency, effectively narrowing the bandwidth. Therefore, suppressing beam angle broadening is crucial for achieving wideband communication with a phased array antenna. Accordingly, the present invention aims to provide a beamforming circuit that suppresses beam angle broadening and performs beamforming. [Means for solving the problem]

[0012] According to one aspect of the present invention, a beamforming circuit is provided for beamforming a faceted array antenna including a plurality of antenna elements arranged in a row at equal intervals, comprising: a plurality of LO phase shifters that shift the phase of an input LO signal by a variable phase shift amount; a plurality of IF phase shifters that delay the phase of frequency components included in an input IF signal as the frequency is lower than the center frequency and advance the phase as the frequency is higher than the center frequency; and a plurality of mixers connected to the plurality of antenna elements, the plurality of LO phase shifters, and the plurality of IF phase shifters, wherein the LO phase difference between the plurality of mixers is set to the variable phase shift amount by the plurality of LO phase shifters, and the phase shift characteristics of the IF phase shifters change according to the variable phase shift amount of the LO phase shifters. [Effects of the Invention]

[0013] According to the present invention, beamforming can be performed while suppressing beam angle broadening. This enables broadband communication using a phased array antenna. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram showing the configuration of a beamforming circuit according to the first embodiment of the present invention. [Figure 2] This graph shows the phase shift characteristics of an IF phase shifter. [Figure 3] This figure shows an example of the configuration of an IF phase shifter and its phase shift characteristics. [Figure 4A] Figure 1 illustrates the principle of beamforming using the beamforming circuit shown. [Figure 4B] Figure 1 illustrates the principle of beamforming using the beamforming circuit shown. [Figure 5] This is a diagram showing the configuration of a beamforming circuit according to a second embodiment of the present invention. [Figure 6] Figure 5 is a graph showing the phase shift characteristics of the IF phase shifter in the beamforming circuit. [Figure 7] This diagram illustrates the principle of beamforming in phased array antennas. [Figure 8] This graph shows the relationship between the LO phase difference between mixers and the beam angle. [Modes for carrying out the invention]

[0015] The embodiments of the present invention will be described in detail below, with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. The inventors provide the accompanying drawings and the following explanation so that those skilled in the art can fully understand the present invention, and do not intend to limit the subject matter described in the claims by these. Furthermore, the dimensions and detailed shapes of each component depicted in the drawings may differ from those of the actual components.

[0016] (First Embodiment) Figure 1 is a configuration diagram of a beamforming circuit according to a first embodiment of the present invention. The beamforming circuit 100 according to this embodiment is a circuit for a 300 GHz band silicon CMOS radio and performs beamforming of a faceted array antenna which includes a plurality of antenna elements 11 arranged in a row at equal intervals.

[0017] The antenna element 11 is a rectangular microstrip patch antenna or the like formed on the surface of a printed circuit board. Considering that the desired RF frequency for 300 GHz wireless communication is 252 to 296 GHz (wavelength approximately 1000 to 1200 μm), as an example, the sum of the lengths of the two sides of the antenna element 11 is 300 to 350 μm, with a slight margin over one-quarter wavelength of the RF signal, and the arrangement pitch of the antenna elements 11 is 600 to 700 μm, with a slight margin over one-half wavelength of the RF signal.

[0018] The beamforming circuit 100 includes an IF signal line 21, multiple IF phase shifters 23, an LO signal line 24, multiple LO phase shifters 26, and multiple mixers 29. These circuit elements are formed on a semiconductor substrate.

[0019] Each mixer 29 is electrically connected to a corresponding antenna element 11. Generally, a transmitter inputs an IF signal and a LO signal to a mixer, upconverts the IF signal with the LO signal to generate an RF signal, amplifies it with a power amplifier, and transmits it from the antenna. On the other hand, a receiver amplifies the RF signal received by the antenna with a low-noise amplifier, inputs it to the mixer along with the LO signal, and downconverts the RF signal with the LO signal to generate an IF signal. However, when the RF signal reaches the 300 GHz band, it becomes difficult to place a power amplifier in the final stage of a transmitter and a low-noise amplifier in the first stage of a receiver due to the operating limits of CMOS transistors. Therefore, in high-frequency bands such as the 300 GHz band, as shown in Figure 1, transmitters with a mixer-last configuration where the mixer is placed in the final stage and receivers with a mixer-first configuration where the mixer is placed in the first stage are used.

[0020] Multiple mixers 29 are connected to multiple LO phase shifters 26. More specifically, the multiple mixers 29 are connected in common to an LO signal line 24, and multiple LO phase shifters 26 are connected in series between these connection points.

[0021] The LO phase shifter 26 shifts the input LO signal by a variable phase shift amount θ LO This is a circuit that shifts the phase by θ. In the example in Figure 1, the LO signal line 24 extends to the left and right, and the LO signal is input to its left end. Therefore, using the phase of the LO signal input to the leftmost mixer 29 as a reference, each mixer 29 to the right of it shifts the phase by θ from the reference. LO An LO signal with a phase delay of an integer multiple of θ is input. That is, the LO phase difference between mixers 29 is θ LO It is as follows: θ LO It can be controlled by a controller (not shown in the diagram).

[0022] θ LO It can also be controlled to a negative value. For example, the variable phase shift amount can be -θ LO When controlled, the LO phase shifter 26 changes the phase of the input LO signal to θ LOIt advances by only that much and outputs. In this case, the phase of the LO signal input to the rightmost mixer 29 is used as the reference, and each mixer 29 to the left of it is set to θ from the reference. LO An LO signal with a phase delay of an integer multiple of that will be input.

[0023] The IF signal line 21 is a line that supplies IF signals to each mixer 29 in the transmitter, and a line that acquires IF signals from each mixer 29 and power couples them in the receiver. Specifically, the IF signal line 21 has an H-tree type wiring structure. IF phase shifters 23 are connected to the leaf nodes of this H-tree type IF signal line 21. That is, the line lengths from the root node of the IF signal line 21 to each IF phase shifter 23 are all equal, and there is no signal delay difference from the root node of the IF signal line 21 to each IF phase shifter 23, meaning that the phase of the IF signals is aligned across all IF phase shifters 23.

[0024] The IF phase shifter 23 is an equalizer-like circuit that provides different delay amounts for each frequency component of the input signal. For frequency components in the input IF signal, it delays the phase as the frequency is lower than the center frequency and advances the phase as the frequency is higher than the center frequency. Furthermore, the phase shift characteristics of the IF phase shifter 23 are determined by the variable phase shift amount θ of the LO phase shifter 23. LO It is designed to change accordingly.

[0025] Figure 2 is a graph showing the phase shift characteristics of the IF phase shifter. The center frequency of the IF signal is f IF The lower frequency of the IF signal is f IF -f BW / 2 The upper frequency of the IF signal is f IF +f BW / 2 If we take the antenna element 11 at the end of the multiple antenna elements 11 as element 0 and count from there, let n be the number of the antenna element 11, then the phase shift characteristic of the IF phase shifter 23 corresponding to the nth antenna element 11 is f IF Using the phase of as a reference, f IF -f BW / 2 Compared to the standard, f BW / 2 / f0|θ LO | delays the phase by this much, fIF +f BW / 2 Compared to the standard, f BW / 2 / f0|θ LO A linear phase shift characteristic that advances the phase by | is used as the basic phase shift characteristic, and the value is set to n times this basic phase shift characteristic.

[0026] In this context, the "end" antenna element 11 refers to the antenna element 11 that radiates the most phase-lag RF signal in the case of a transmitter, and the antenna element 11 that receives the most phase-lead RF signal in the case of a receiver. In the example in Figure 1, the antenna element 11 on the far right corresponds to the end antenna element 11.

[0027] When n=0, that is, the IF phase shifter 23 corresponding to the end antenna element 11 connects the IF signal to the mixer 29 without shifting the phase of the IF signal. Depending on the direction of the RF signal beam, the rightmost or leftmost antenna element 11 becomes the end antenna element 11, so the IF phase shifters 23 corresponding to the antenna elements 11 at both ends are configured to switch between shifting the phase of the IF signal and not shifting it.

[0028] Figure 3 shows an example of the configuration of an IF phase shifter and its phase shift characteristics. For example, the IF phase shifter 23 comprises a variable resistor 231 and a capacitor 232 connected in parallel, and a variable resistor 233 connected between the connection point of these elements and ground. Such a circuit configuration is essentially a high-pass filter. A high-pass filter has a frequency band in which the phase changes approximately linearly with respect to the frequency of the input signal in the attenuation region below the cutoff frequency. Furthermore, the phase shift characteristics in this frequency band can be controlled by adjusting the resistance values ​​of the variable resistors 231 and 233. Therefore, the phase shift characteristics shown in Figure 2 can be achieved with an IF phase shifter 23 of this configuration.

[0029] Figure 4A is a diagram illustrating the principle of beamforming using the beamforming circuit shown in Figure 1. The beamforming circuit shown in this figure is a selection of the right half of the beamforming circuit 100 in Figure 1. Note that the IF signal line 21 and the IF phase shifter 23 corresponding to the antenna element 11 at the end are set to a mode that does not shift the phase of the IF signal, so they are not shown in the diagram.

[0030] Let's explain the radio waves radiated from the two antenna elements 11. If there is no IF phase shifter 23, as explained in Figure 7, the RF signal f0 shifts from P1 to P C During propagation to the lower frequency f0-f BW / 2 P is even further away LSB It propagates to the upper frequency f0+f BW / 2 P is closer to the front. USB It propagates to the . On the other hand, in the beamforming circuit 100 according to this embodiment, the phase of each frequency component of the IF signal is adjusted by the IF phase shifter 23, f IF -f BW / 2 is f IF f BW / 2 / f0|θ LO |The phase is delayed by only f IF +f BW / 2 is f IF f BW / 2 / f0|θ LO The phase advances by | and is input to mixer 29. As a result, as shown by the arrow in the figure, P LSB and P USB P C As it approaches, the wavefront W of each frequency component in the bandwidth of the RF signal C , W LSB , W USB Gather them and use Beam B C B LSB B USB The direction can be aligned. The same can be said for the radio waves radiated from the antenna element 11 further to the left, which is not shown in Figure 4A.

[0031] FIG. 4B is a diagram for explaining the principle of beamforming by the beamforming circuit of FIG. 1. The beamforming circuit shown in this figure is a pick-up of the left half in the beamforming circuit 100 of FIG. 1. Note that the IF signal line 21 and the IF phase shifter 23 corresponding to the end antenna element 11 are not shown because they are set in a mode that does not shift the IF signal.

[0032] In this example, unlike the example of FIG. 4A, the variable phase shift amount of the LO phase shifter 26 is controlled to a negative value of -θ LO When the variable phase shift amount is a positive value, as shown in FIG. 4A, the direction of the beam can be controlled within the first quadrant with the normal line of the antenna plane as the axis. On the other hand, when the variable phase shift amount of the LO phase shifter 26 is a negative value, the direction of the beam can be controlled within the second quadrant as in this example. Thus, the end antenna element 11 is switched according to the sign of the variable phase shift amount of the LO phase shifter 26. That is, in the beamforming circuit 100 of FIG. 1, when the variable phase shift amount of the LO phase shifter 26 is a positive value, the right end antenna element 11 is the end antenna element 11, and when the variable phase shift amount of the LO phase shifter 26 is a negative value, the left end antenna element 11 is the end antenna element 11.

[0033] In the case of the example of FIG. 4B as well, the phase of each frequency component of the IF signal is adjusted by the IF phase shifter 23, and f IF -f BW / 2 is delayed by |f IF / f0|θ BW / 2 | compared to f LO and f IF +f BW / 2 is advanced by |f IF / f0|θ BW / 2 | compared to f LO and input to the mixer 29. As a result, as indicated by the arrow in the figure, P LSB and P USB approach P C and the wavefronts W C 、W LSB 、W USB of each frequency component in the bandwidth of the RF signal are aligned to form the beams B C 、B LSB 、B USBThe direction can be aligned. The same can be said for the radio waves radiated from the antenna element 11 further to the right, which is not shown in Figure 4B.

[0034] (Second embodiment) Figure 5 is a configuration diagram of a beamforming circuit according to a second embodiment of the present invention. The beamforming circuit 200 according to this embodiment is an extension of the beamforming circuit 100 of Figure 1, enabling two-dimensional beamforming in a faceted array antenna in which multiple antenna elements are arranged in a vertical and horizontal grid. Specifically, the beamforming circuit 200 is formed by arranging the beamforming circuit 100 of Figure 1 in the column direction and arranging four of these in the row direction.

[0035] In the beamforming circuit 200, each mixer 29 is connected to the leaf node of the H-tree type IF signal line 21. That is, the line length from the root node of the IF signal line 21 to each mixer 29 is all equal, and there is no difference in signal delay from the root node of the IF signal line 21 to each mixer 29, meaning that the phase of the IF signals is aligned among all mixers 29.

[0036] In the beamforming circuit 200, the mixers 29 are arranged in a 4x4 grid. Antenna elements 11 (not shown) corresponding one-to-one to each mixer 29 are also arranged in a 4x4 grid with the same pitch as the mixers 29 and are electrically connected to the mixers 29.

[0037] In the beamforming circuit 200, a main LO signal line 22 extending in a predetermined direction (left-right in the example shown in the figure) and a plurality of main line LO phase shifters 25 are provided to connect the beamforming circuits 100 together. The LO signal lines 24 extend orthogonally from the main LO signal line 22 in a vertical direction (up-down in the example shown in the figure) at intervals of 600 to 700 μm, the same as the arrangement pitch of the mixer 29.

[0038] The main line LO phase shifter 25 receives the input LO signal and shifts it by a variable amount φ HIt is a circuit that performs phase shift. The main line LO phase shifter 25 is provided between each connection point of a plurality of LO signal lines 24 in the LO signal main line 22. Also, main line LO phase shifters 25 are provided at the start and end of the LO signal main line 22. In the illustrated example, the left end of the horizontally extending LO signal main line 22 corresponds to the start, the right end corresponds to the end, and a total of five main line LO phase shifters 25 are connected in series to the LO signal main line 22. These main line LO phase shifters 25 are commonly controlled by a controller (not shown), and the input LO signal is phase-shifted by a variable phase shift amount φ H for phase shift.

[0039] The LO phase shifter 26 is also provided at the start and end of the LO signal branch line 24. In the illustrated example, the upper end of each vertically extending LO signal branch line 24 corresponds to the start, the lower end corresponds to the end, and a total of five LO phase shifters 26 are connected in series to each LO signal line 24. These LO phase shifters 25 are commonly controlled by a controller (not shown), and the input LO signal is phase-shifted by a variable phase shift amount φ V for phase shift.

[0040] In the mixer 29 arranged in a 4×4 grid pattern of vertical and horizontal directions, taking the upper left as the reference position, the phase φ 11 of the LO signal input to the mixer 29 at the reference position is taken as the reference phase φ0. In this case, as the arrangement position of the mixer 29 moves further to the right from the reference position, the phase of the LO signal input to that mixer 29 is delayed by φ H each. Further, as the arrangement position of the mixer 29 moves further below the reference position, the phase of the LO signal input to that mixer 29 is delayed by φ V each. That is, assuming i = {2, 3, 4} and j = {2, 3, 4}, taking the reference position as the first one, the phase of the LO signal input to the mixer 29 at the i-th position to the right and the j-th position below is φ ij = φ0 + (i - 1)φ H + (j - 1)φ V becomes.

[0041] By controlling the phase shift amount φ H of the main line LO phase shifter 25, the beam direction in the row direction of the array of antenna elements 11 (not shown) can be controlled, and by controlling the phase shift amount φ VBy controlling this, the beam direction in the column direction of the array of antenna elements 11 (not shown in the figure) can be controlled. In other words, the beam direction can be controlled up, down, left, and right simply by adjusting the phase of the LO signal.

[0042] Figure 6 is a graph showing the phase shift characteristics of the IF phase shifter in the beamforming circuit of Figure 5. The center frequency of the IF signal is f IF The lower frequency of the IF signal is f IF -f BW / 2 The upper frequency of the IF signal is f IF +f BW / 2 If we consider the antenna element 11 at the end of the row as the 0th element and count from there as n, and the antenna element 11 at the end of the column as the 0th element and count from there as m, then the phase shift characteristic of the IF phase shifter 23 corresponding to the nth row and mth column antenna element 11 is f IF Using the phase of as a reference, f IF -f BW / 2 Compared to the standard, f BW / 2 / f0√(n 2 φ H 2 +m 2 φ V 2 ) delays the phase by that much, f IF +f BW / 2 Compared to the standard, f BW / 2 / f0√(n 2 φ H 2 +m 2 φ V 2 The phase shift characteristic is set to advance the phase by ).

[0043] <Effects> The beamforming circuits 100 and 200 can align the beam direction of each frequency component within the bandwidth of the RF signal. As a result, even at long communication distances, each frequency component of the RF signal bandwidth reaches the receiver with approximately the same beam angle, suppressing relative attenuation of frequency components far from the center frequency and enabling wideband communication. Although the above embodiment describes the case of a transmitter, similar effects can be obtained in the case of a receiver.

[0044] ≪Variations≫ It goes without saying that in the first embodiment, the number of antenna elements 11 is not limited to four, and in the second embodiment, the number of antenna elements 11 is not limited to a total of 16 (4x4). The antenna gain can be increased by increasing the number of antenna elements 11. For example, in the first embodiment, by arranging 32 antenna elements 11, the antenna gain becomes 8 times by simple calculation. Also, in the second embodiment, by using 32x32 (1024) antenna elements 11, the antenna gain becomes 64 times by simple calculation. When the number of antenna elements 11 is large, the length of the IF signal line 21, LO signal line 22, and LO signal branch line 24 becomes longer, which may cause significant signal attenuation at the end of the signal lines. For this reason, a buffer circuit may be appropriately provided at a suitable point in the middle of the signal line to allow the transmission of a signal of a certain magnitude or greater to the end.

[0045] The IF signal line 21 does not have to be an H-tree. For example, an individual IF signal line 21 may be connected to each IF phase shifter 23. In the case of a transmitter, the IF signal line 21 should be configured to supply in-phase IF signals to each IF phase shifter 23, and in the case of a receiver, it should be configured to power-couple the IF signals output from each IF phase shifter 23.

[0046] The LO phase shifters 23 do not necessarily have to be connected in series. For example, each mixer 29 may be connected to a separate LO phase shifter 23 so that the LO phase difference between the LO phase shifters 23 remains equal.

[0047] As described above, embodiments have been explained as examples of the technology in the present invention. For this purpose, accompanying drawings and a detailed description have been provided. Therefore, among the components described in the accompanying drawings and detailed description, there may be not only components that are essential for solving the problem, but also components that are not essential for solving the problem, in order to illustrate the above technology. For this reason, the mere fact that these non-essential components are described in the accompanying drawings and detailed description should not be immediately assumed to be essential. Furthermore, since the above embodiments are for the purpose of illustrating the technology in the present invention, various changes, substitutions, additions, omissions, etc., can be made within the scope of the claims or equivalents. [Explanation of Symbols]

[0048] 100, 200 beamforming circuits 11 Antenna elements 21 IF signal line 22 LO signal main line 23 IF phase shifter 24 LO signal line 25 Mains LO phase shifter 26 LO phase shifter 29 Mixer

Claims

1. A beamforming circuit for beamforming a faceted array antenna, which includes multiple antenna elements arranged in a row at equal intervals, Multiple LO phase shifters that shift the input LO signal by a variable phase shift amount, Multiple IF phase shifters that delay the phase of frequency components in the input IF signal as the frequency is lower than the center frequency, and advance the phase as the frequency is higher than the center frequency, The system comprises the plurality of antenna elements, the plurality of LO phase shifters, and the plurality of mixers connected to the plurality of IF phase shifters, The multiple LO phase shifters set the LO phase difference between the multiple mixers to the variable phase shift amount, and the phase shift characteristics of the IF phase shifter change according to the variable phase shift amount of the LO phase shifter. A beamforming circuit characterized by the following features.

2. The IF phase shifter corresponding to the end antenna element among the plurality of antenna elements is capable of switching whether or not to shift the phase of the IF signal. The beamforming circuit according to claim 1.

3. The phase shift characteristic of the IF phase shifter corresponding to the nth (where n is an integer of 1 or more) antenna element from the end is set to n times the basic phase shift characteristic. The beamforming circuit according to claim 2.

4. The basic phase shift characteristic is the LO phase difference θ between the plurality of mixers ＬＯ , the center frequency of the RF signal is f ０ , and the half bandwidth of the RF signal is f ＢＷ／２ . Taking the phase of the center frequency of the IF signal as a reference, the phase is delayed by f ＢＷ／２ / f ０ |θ ＬＯ | from the reference for the lower frequency of the IF signal, and the phase is advanced by f ＢＷ／２ / f ０ |θ ＬＯ | from the reference for the upper frequency of the IF signal, which is a linear phase shift characteristic The beamforming circuit according to claim 3.

5. The aforementioned multiple mixers are provided with a common LO signal line, The plurality of LO phase shifters are provided and connected in series between each connection point of the plurality of mixers on the LO signal line. A beamforming circuit according to any one of claims 1 to 4.

6. Equipped with an H-tree type IF signal line, The plurality of IF phase shifters are connected to the leaf nodes of the H-tree of the IF signal line. A beamforming circuit according to any one of claims 1 to 4.

7. Equipped with an H-tree type IF signal line, The plurality of IF phase shifters are connected to the leaf nodes of the H-tree of the IF signal line. The beamforming circuit according to claim 5.

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