JP2720972B2 - Phased array antenna with coupler in spatial filter configuration - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna system, and more particularly, to a lossless spatial filter provided between an input port of an antenna and an antenna element to each input port. A system in which the antenna element pattern is modified by having the associated effective element pattern primarily fall within a selected angular region of space.

BACKGROUND OF THE INVENTION Array antenna systems are designed to transmit a desired radiation pattern in one of a plurality of angular directions within a selected spatial region. According to the known design of such an array antenna, each antenna element has an input port associated with it. By varying the amplitude and / or phase of the wave energy signal sent to the input port, the antenna pattern can be steered electronically in space to direct it in the desired direction of radiation, or a time-based beam scan pattern The antenna pattern can also be controlled so as to emit desired signal characteristics. If it is desired to have the array antenna radiate its beam over a selected limited spatial region, it is preferred that the radiation pattern of the individual antenna elements also fall primarily within the selected angular region. . This makes it possible to maximize the element spacing while suppressing undesired grating ropes.

In some systems, it is not possible to control the element pattern by changing the physical shape of the antenna element. This is because an element aperture size that exceeds the required element spacing of the array is required to obtain a desired element pattern. A practical solution to overcoming the physical element size constraints is to connect each antenna input port to two such that the effective element pattern associated with each input port is formed by the combined emission of multiple elements.
The provision of a network interconnecting one or more antenna elements. These networks can be implemented by printed circuit technology using a single substrate layer.

One known solution to this problem is described in U.S. Pat.
No. 3,625. Nemit obtains a large effective element size by providing an intermediate antenna element between the primary antenna elements and coupling the signal from the port of the primary antenna element to the port of the intermediate element. This tapered multi-element aperture excitation can provide some control over the radiated antenna pattern.

A more effective known antenna coupling network is disclosed in US Pat. No. 4,041,501 to Frazzita et al., Which is hereby incorporated by reference and assigned to the same assignee as the present invention. According to the technique of Fragita, the antenna element is configured as an element module, and each module is provided with an input port. The transmission line is
It is connected to all antenna element modules in the array. The transmission line connects the signal sent to any port to a selected element of all antenna element modules of the array. This antenna (hereinafter, compact (CO
MPACT) provides an effective element aperture that is coextensive with the aperture of the array.

Yet another effective known antenna coupling network is disclosed in U.S. Pat. No. 4,143,379 to Wheeler, hereby incorporated by reference and assigned to the same assignee as the present invention. According to Wheeler's technique, a wave energy signal is coupled to adjacent modules using cross-coupled ports.

Yet another technique is described in U.S. Pat. No. 4,168,50 which describes an antenna array having a printed circuit lens in a coupling network.
It is disclosed in Issue 3. The radiated signals received by each of the plurality of spatially separated antennas forming the directional array are coherently returned by these lenses. These lenses comprise a plurality of vertically upright, circularly arranged printed circuit panels, each of which comprises a conductor strip having one end connected to each antenna. A plurality of semi-elliptical circuit panels are fixed to the vertical panel at a predetermined angle. Metal strips plated on semi-elliptical panels provide the desired delay to the antenna signal. Connected to the time delay strip is a composite strip, which at one end generates a composite output signal in a semi-oval pattern. The angle at which the semi-oval board is fixed to the vertical board corrects for the time delay distortion caused by the placement of the composite strip. This configuration cannot be implemented using integrated circuit technology on a single substrate layer.

U.S. Pat. No. 4,321,605 discloses an array antenna system wherein the ratio of antenna elements to input terminals interconnected via a primary transmission line is at least 2: 1. The secondary transmission lines are connected to and cross a selected number of primary transmission lines. A signal sent to any one of the input terminals is mainly connected to the element corresponding to the input terminal, and is also connected to other selected elements.

In time-based scanning beam systems such as the microwave landing system (MLS), linearity is required for glide guidance, ie, the difference between the actual angle and the indicated angle. Must be within some limited range. It is also necessary to minimize the field monitor distance to the runway antenna. In particular, in MLS, the present invention
It is an object of the present invention to provide a non-lean or fully loaded array that can be used to obtain linearity and minimize field monitor distance.

An object of the present invention is to provide an alternating array system in which an antenna element pattern is formed by a spatial filter between an input port of the antenna element and the antenna element.

Another object of the invention is a non-diluted antenna system, i.e. the number of antenna input ports is equal to the number of output ports of the antenna element, and thus there is no reduction ratio between the number of radiators and the number of phase shifters It is to provide such an antenna system.

It is yet another object of the present invention to provide an antenna system that does not generate grating lobes.

It is yet another object of the present invention to provide a lossless spatial filter having an input / output ratio of 1: 1 and using only a minimal number of couplers and termination connections.

It is yet another object of the present invention to provide a lossless spatial filter that is flexible in that it controls the radiation pattern of the spatial filter, meets linearity requirements, and minimizes the field monitor distance. is there.

According to the present invention, an antenna system radiates a wave energy signal into a selected angular region of space and a desired angular pattern. The antenna system includes a lossless spatial filter having N input ports and N output ports. The aperture of the system comprises a plurality of N antenna elements. These antenna elements are arranged along a predetermined path, and each element is connected to only one output port of the spatial filter.

The beam steering unit controls the direction of the radiation and comprises N phase shifters and means for controlling these phase shifters. Each phase shifter has a phase shift input port and a phase shift output port, which output port is connected to only one input port of the spatial filter. The antenna also includes means for providing a wave energy signal. The supply means comprises a signal generator for supplying a power divider having N output signal ports, each output port being connected to only one phase shift input port.

Examples For a better understanding of the present invention, a detailed description is given below with reference to the accompanying drawings. The scope of the invention is pointed out in the appended claims.

FIG. 1 is a circuit diagram showing an antenna system according to the present invention. Fig. 1 shows a predetermined route (in this case, a straight line)
Are shown in the figure. Each antenna element is connected to one and only one output port 9-16 of the spatial filter 17. The spatial filter is composed of a plurality of modules A to H provided one for each antenna element. Spatial filter
17 has eight input ports 18-25, each of which is connected to the output of one and only one phase shifter 26-33. The array of phase shifters 26-33 forms a beam steering unit 34. Input 35-42 of the phase shifter is a signal generator
It is connected to one and only one output of a power divider 43 signaled by 44. The power divider and the signal generator form a supply means for supplying a wave energy signal. Although the filter 17 is shown as being symmetric, it is contemplated that the spatial filter according to the present invention may be asymmetric.

Referring to the signal path of the wave energy signal provided by signal generator 44, the original signal is provided via line 45 to power divider 43, which divides the signal into eight equal components. Each component is sent to only one input of beam steering unit 34 via lines 46-53. For example, to describe the left-most portion of the antenna system, line 46 supplies a signal component to input 35 of beam steering unit 34. This component then passes through a phase shifter 26, which shifts the phase of the component based on a command received via a control line 55 from a control unit 54. It is sent to the input port 18 of the filter 17. The signal component sent to the input port 18 is supplied to the output port 9 connected to the antenna element 1 and also supplied to the element 2 adjacent to the antenna element 1 by the coupling structure.

Spatial filter 17 couples the component signal provided to its input to the antenna element associated with the input and the element adjacent to the associated element. Couplers 56-63 couple the signal provided to the associated antenna element to the antenna element to the left of the associated antenna element. The component signal provided to an input is sent by a transmission line 64-71 to the antenna element associated with that input. For example, power divider
The component signal provided by the branch 39 at 43 is provided via the phase shifter 30 and to the input 22 of the spatial filter 17.
This input 22 is connected by a transmission line 68 to its associated output 13 and antenna element 5. The component signal is also coupled by the coupler 59 to the antenna element 4 adjacent to the left side of the antenna element 5. Similarly, the component signals provided at the inputs are also coupled by couplers 72-80 to antenna elements adjacent to the right of the associated antenna element. For example, the component signal provided by the power divider junction 59 passes through the phase shifter 29 and the input 21 of the spatial filter 17.
Supplied to This component signal is then transmitted to transmission line 67
Sent to output 12. Output 12 is antenna element 4
Is directly connected to. Element 5 is adjacent to the right side of antenna element 4 and receives a portion of the component signal via coupler 76. Element 3 is adjacent to the left side of antenna element 4,
A portion of the component signal is received via coupler 58.

The spatial filter 17 is shown in a module form.
Therefore, the input to the coupler 72 is connected by the termination connection 81. This is because there is no antenna element on the left side of the antenna element 1. Similarly, the output from coupler 56 is connected by termination connection 82. This is because there is no antenna element on the left side of the antenna element 1 for receiving the component signal given to the input 18. On the right side of the spatial filter 17, the coupler 80 is connected by the terminal connection 83, and the coupler 63 is connected by the terminal connection 84. This is because there is no antenna element on the right side of the antenna element 8 that receives the coupling signal from the coupler 80 or supplies the coupling signal via the coupler 63.

FIG. 2 is a plan view of a printed circuit coupling network useful as the spatial filter 17 of FIG. This network 17
Input port 18 connected to the output of beam steering unit 34
-25. These input ports are connected to a first series of couplers C1, shown in detail in FIG. 2a. Coupler C1 and all other couplers are standard microstrip network couplers having a predetermined coupling ratio. The specific coupling ratio depends on the width, length and thickness of the transmission line in the coupler. Typically, the signals sent to inputs 101 and 102 of coupler C1 are connected to outputs 103 and 104 based on a predetermined ratio. In the case of coupler C1, input 102 is connected by termination connection 105, and any component signal sent to input 101 is distributed to outputs 103 and 104,
C1 ² + T1 ² = 1.

Following the first array of couplers C1, there is a second array of couplers C2, shown in detail in FIG. 2b. Input 105 and 106
Are sent to the output 108 at the ratio T2 and sent to the output 107 at the ratio C2 so that T2 ² + C2 ² = 1. Completing the three-level spatial filter 17 is a third series of couplers 109-116. According to the present invention, these couplers have the same configuration as coupler C1. Couplers 109-116 operate similarly to coupler C1 shown in FIG. 2a by combining the signals sent to their inputs with the outputs 9-16 of spatial filter 17.

Ideally, as defined by the present invention, the spatial filter 17 is lossless (apart from dissipation losses), so that the power (voltage) through each coupler C1 and T1 respectively.
Must apply the following relationship:

C1 ² + T1 ² = 1, and C2 ² + T2 ² = 1 A lossless state for the network is ensured by the following relation:

This relation can be derived by setting inputs 18-25 equal to 1 and inputs to termination connections 117-124 equal to 0.

A "non-diluted spatial filter" as used in connection with the present invention is a filter formed by an array of couplers. This array is essentially lossless in that the power dissipated in the termination connections is minimized.

FIG. 3 shows a 3/4 level cascaded spatial filter 3
FIG. 3 is a circuit diagram of the antenna system according to the present invention including 00. In general, this spatial filter can be used in combination with the antenna system of FIG. 1 by replacing the spatial filter 17 of the antenna system shown in FIG. Each antenna element 1-8 has one and only one output port 301 of the spatial filter 300.
Connected to. The spatial filter 300 includes a plurality of modules A to H, one for each antenna element. The spatial filter 300 has input ports 302 each connected to one and only one output of the phase shifting network.

FIG. 4 is a plan view of a printed circuit coupling network of the cascaded spatial filter 300 shown in FIG. The network 300 has an input port 302 connected to the output port of the beam steering unit. These input ports are connected to a first series of couplers, shown in detail in FIG. 2a.
Connected to C1. Following the first array of couplers C1, there is a second array of couplers C2, shown in detail in FIG. 2b. Following the second array of coupler C2 is a third array of coupler C2. Completing the four-level spatial filter 300 is a fourth series of couplers C1. According to the invention, the coupler C1 at the beginning and the end of the array and the intermediate coupler C2 are configured identically in order to provide symmetric excitation. The following relation ensures a lossless state for the network.

FIG. 5a shows an ideal antenna pattern for an antenna according to the invention using a spatial filter with two-level coupling. Such a connection essentially forms lobes 501, 502 and 503. FIG. 5b shows a typical antenna pattern using a three-level spatial filter forming a single lobe 504. FIG. 5c shows a typical antenna pattern of a four-level spatial filter generating a very well-defined single probe 505.

Synthesis Procedure for 5-Level Non-Dilution Spatial Filter Step 1: Referring to FIGS. 6a, 6b, 6c and 6d, determine the initial values of couplers C1-C5.

(A) Specify desired excitation A1-A5 (b) Specify C1 (c) Calculate C2-C5 using Fig. 6c Step 2: Calculate actual excitation A1'-A5 'based on the following formula I do.

(A) A1 '= T5C4C3C2C1 (b) A2' = C5T4C3C2C1 -T5T4T3C2C1 -T5C4T3T2T1 -T5C4C3T2T1 (c) A3 '= C5C4T3C2C1 -T5C4T3C2T1 -T5T4T3T2T1 -T5T4C3T2C1 -C5T4C3T2T1 -C5T4T3T2C1 (d) A4' = C5C4C3T2C1 -T5T4C3C2T1 -C5T4T3C2T1 -C5C4T3T2T1 (E) A5 '= C5C4C3C2T1 Step 3: Adjust the value of coupler C2-C5.

(A) Adjust C5 as follows.

(B) Adjust C4 as follows.

(C) Adjust C3 as follows.

(D) Adjust C2 as follows.

Step 4: The actual excitation A1'-A5 'is calculated again. (A
(See step 2 for 1'-A5 'formula) Step 5: Normalize the actual excitation by calculating A1 "-A5".

(A) A ″ = 1. Therefore, (b) A2 ″ = A2 ′ / A1 ′ (c) A3 ″ = A3 ′ / A1 ′ (d) A4 ″ = A4 ′ / A1 ′ (e) A5 ″ = A5 '/ A1' Step 6: Calculate the deviation S between the normalized actual excitation A1 "-A5" and the desired excitation A1-A5.

Step 7: Step 3 until the deviation S falls within the allowable range.
Repeat 6.

Step 8: the ratio of the power P _T and the radiation power P _R of the sealing end, i.e., repeat steps 1-7 until P _T / P _R is minimized.

P _T = Σ (TM) ² ; P _R = Σ (AN) ² N = 1, 2,... 5 For example, consider the case of a five-element aperture as shown in FIG. 6a. Assume the desired excitation (from step 1a) as follows.

A1 = 1.0000 A2 = 1.6086 A3 = 1.93156 A4 = 1.6086 A5 = 1.0000 Here, if C1 = 0.979 (from step 1b), the values of the other couplers are as follows.

C2 = 0.9502 C3 = 0.9366 C4 = 0.9600 C5 = 0.9852 With the normalized actual excitation (steps 2-5):

A1 = 1 A2 = 1.3755 A3 = 1.6478 A4 = 1.544 A5 = 1.1957 The dB loss (from step 8) between the normalized actual excitation (from step 5) and the desired excitation (from step 1a) is become that way.

 LOSS = 7.12 dB Continue the synthesis procedure according to Table 1 below.

As shown in Table 1, Trial 5 shows the optimal configuration with the least power loss. As shown in Table 2, trial 4
The optimal configuration is shown for a five-coupler structure where symmetrical excitation must be used to set C5 = C1 and C4 = C2.

Although the above procedure was applied to develop a symmetric filter, this procedure is of a general nature and can be used to develop an asymmetric filter. Symmetry generally refers to maintaining complexity and reducing complexity. Symmetric filters typically use redundant couplers and other structures that minimize design effort.

Designing a spatial filter involves determining a coupling value for the multilayer circuit. A non-closed form solution would be readily apparent for synthesizing a network to form a particular output voltage distribution. However, analysis of any network is possible. Therefore, the synthesis involves the iterative trial and error procedure described above, which gradually adjusts the coupling value until the desired output is obtained.

Since the computational time can be significant when analyzing a complex network, it is desirable to form an iterative algorithm that is reasonably timely focused on the desired solution. When the analysis is performed for each combination of the binding values, it takes several weeks or months to evaluate by a computer.
Furthermore, there are an unlimited number of solutions for forming the desired amplitude distribution. The difference between these solutions is the resulting insertion loss of the network. It is therefore necessary to determine the minimum possible loss by theoretical means and to know when the optimal solution has been achieved.

The theoretical loss of the spatial filter network is determined by the idea that power is conserved. The prototype of this network is shown in FIG. This network is symmetric and runs infinitely in both directions. Each input excites a sub-array having N outputs. The outputs of the sub-arrays resulting from adjacent inputs overlap. The network shown in FIG.
It has the same number of inputs and outputs. Therefore, the input and output intervals are equal, and when all inputs are energized, each output port is the sum of the effects from the N input ports.
An internal termination connection must be made for each output port.

The output excitation resulting from input 1 is denoted by A1 (N) and the output excitation resulting from input 0 is denoted by A0 (N). Since the network is symmetric, A1 (N) = A0 (N) =
Aj (N). Similarly, the terminating power, denoted Bj (N), must be equal.

This network is realized by an N-layer directional coupler.
To obtain the desired symmetry, all coupling values for a given layer must be equal. Further, symmetric output excitation (Aj (1) = Aj (N), Aj (2) = Aj (N-1), etc.)
Requires that the coupling value of the first layer be equal to the coupling value of the Nth layer, and so on. Thus, for example, an eight-output network has eight layers of couplers. If the eight-element excitation is symmetric, C1 (the coupling value of all couplers in the first layer) must be equal to C8, C2 = C7, C3 = C6,
C4 must be C5. Therefore, there are only four separate joint values or unknowns that must be determined for the eight output network.

When input power is supplied to port 1, power conservation indicates that the sum of the power of A1 (N) applied to the internally terminated one (B1 (N)) must be equal to the input power. Is done. Normalization for one watt of input power yields:

A and B are voltage coefficients. The power of each output port is
It becomes equal to the square of the voltage coefficient when the impedance of the system is normalized to 1Ω.

When all input ports are excited with the same power and phase, the output of each port is the sum of the N voltages. Due to symmetry and power conservation, the sum of the power at one output port and its internal termination connection must equal one watt. All output ports are equal.

By combining equations (3) and (4), the following is obtained.

If the network must not be lossy, the internal termination connection cannot be powered when a single input port is energized (all B = 0). If this state exists, then:

The output excitation that satisfies equation (6) is minimal. In the following cases, a minimum loss occurs for the excitation that does not satisfy the expression (6).

If this condition is satisfied, there is no loss in the network when all input ports are excited with the same amplitude and phase. The loss when a single input port is excited and the sub-array pattern has a maximum in the in-phase direction is given by:

When the sub-array pattern has a maximum in a direction other than the in-phase direction, the lower bound on loss is increased by the difference in sub-array gain in the two directions. An optimal network is a network that causes minimal losses. The expected loss is the difference between the calculated network loss and the theoretical value. Therefore, the theoretical minimum loss is calculated to be 3.1 dB using Equation (8) when a single input port is excited, and the minimum loss that can actually be obtained with a feasible network is In the case of 4.6 dB, it was found that the loss when all inputs were excited in phase was 1.5 dB. This 1.5 dB loss is obtained by considering the center of the sub-array pattern. When the array is scanned against the sub-array peak, the loss is theoretically reduced to zero.

The basic topology of a spatial filter network is well known. In the preferred embodiment, 17 layers are required,
It is almost impossible to synthesize this. An actual network that closely approximates the performance of a 17-layer network uses two cascaded 8-layer networks as shown in FIG. The pattern characteristics of this network are shown in FIGS. 9 and 10 for a radiating element spacing of 0.79 wavelength.

FIG. 11 shows the linearity required for MLS runway guidance. Although this linearity will be described focusing on the altitude guidance performance, linearity is also required for azimuth guidance. Linearity has been the subject of much consideration in the MLS industry. The present invention provides a phasing array antenna that meets the requirements of high linearity. Spatial filter networks are a practical way to satisfy low efficiency side rope requirements that are directly related to linearity requirements.

When linearity (autopilot) is required, the degree to which the MLS guidance angle and the actual angle (see FIG. 11) deviate from the ideal linear relationship is limited. This specifies the lateral accuracy characteristics of the angle guidance signal rather than the longitudinal characteristics of the PFN and CMN. Longitudinal properties cause the aircraft to deviate (bend) from the runway or cause noise-like operation of the air traffic controller. Lateral characteristics can cause instability in automatic flight control systems.

After several years of consideration in the MLS industry, today E
It has become generally accepted that the PFN, CMN, and linearity for an L-guide device are all based on the effective side lobe level of the antenna. Which of the three properties (PFN, CMN or linearity) is the driver for the effective side lobe level specification is discussed. Path following noise (PFN) is related to the average path following course error and is caused by the frequency components that the aircraft can follow. Control noise (CMN) exists without PFN, but the scanned MLS signal indicates rebound or slippage that the aircraft cannot follow. At first, PF
It was argued that N was the driver. The effective side lobe level required to keep the PFN for a 1.5 ゜ beamwidth antenna from exceeding 0.0830.0 is −25 dB (assuming a ground reflection coefficient of 0 dB, the PFN is Is ±
0.8 from ICAO standard that must not exceed 1.3 feet
A 3 ゜ PFN limit is derived). After some analysis by the FAA, it was determined that CMN would occur when the aircraft was within 2,000 feet of the runway threshold when the phase center of the antenna was 20 feet above the reflecting ground. Therefore, the FAA's draft specification for obtaining a second MLS specifies the effective side rope level such that the CMN does not exceed 0.045 °. This requires an effective side lobe level of −30 dB for a 1.5 ° beamwidth antenna.

Based on simulating the operation of a real automatic flight control system, it has been concluded that linearity is the most stringent requirement for the specification of the effective side lobe level. The simulation results indicate that the angle error limit must not exceed 0.024 ° in order to ensure that the performance of the automatic flight control system is within a comfortable level for passengers.
This error limit corresponds to an effective side lobe level of -36 dB for a 1.5 ° beamwidth antenna.

After examining the requirements for linearity, a measurement methodology was issued to determine compliance with specifications. In this regard, it should be understood that the effective side lobes can be measured in the antenna range and that design recognition by authorities can be performed based on these antenna measurement ranges.

Side ropes radiated in the direction of the ground by the altitude antenna are folded over the main beam by specular reflection. The radiation of this side rope distorts the beam and the PF
Causes N, CMN and linearity errors. The specifications of PFN and CMN limit the magnitude of the angle guidance error. However, the linearity error is based on the product of the maximum angle guidance error and the height of the antenna phase center above the reflecting ground. If this error-height product is large, the guided loop gain of the automatic flight control system will be substantially reduced to the point where the control system becomes unstable. For example, if the maximum error is 0.045 ° and the center height of the phase is 20 feet, the loop gain is less than +6 dB and −40 dB (“maximum gain spot” and “dead spot” in FIG. 11). Vary between.

Using a model of a flat horizontal plane, the effect of side rope radiation on the performance of the automatic flight control system is quantified.
Its geometric configuration and formula are shown in FIG. For the taxiway case, the magnitude of the error remains essentially constant, and the change in phase is
This is due to the path difference from the indirect signal emitted from the ground image of the EL antenna.

This model was used as a disturbance input to simulate an automatic gliding control system for a small jet aircraft. A criterion for the suitability of an automatic flight control system is whether the passenger feels comfortable. FIGS. 13, 14, and 15 schematically show simulation results for the allowable peak MLS guidance error, the height of the phase center of the advanced antenna, and the comfort of passengers. The simulation starts at a distance of 3 NM from the altitude antenna.

FIG. 13 shows that the automatic control system is unstable for a phase center height of 20 feet and a peak error of 0.083 °. Vertical acceleration exceeds the level at which passengers feel comfortable by a factor of 2.4: 1. For a peak error of 0.045 °, the system is marginally stable, and for large phase center heights, for example, at 37 feet,
It is expected that the system will be unstable (the error height product 0.045 ° × 37 ′ is equivalent to a maximum error of 0.083 ° and a height of 20 feet). FIG. 14 and FIG.
Following the same trend, with a phase center height of 20 feet and a peak error of 0.083 °, the vertical speed and attitude will be at levels that passengers feel comfortable with coefficients of 4: 1 and 2: 1 respectively. It is shown to exceed.

By studying the information available for the specification of the effective side lobe level and the autopilot performance within the level that passengers feel comfortable, the following conclusions are reached.

1. The current PFN error limit (0.083 ゜) is not acceptable.

2. The current CMN error limit (0.045 ゜) is barely acceptable (especially if a high antenna phase center height of 20 feet or more is intended).

3. For the case investigated, a limit of 0.024 mm is considered acceptable.

4. For the specification of the effective side lobe level, linearity is the main system requirement.

5. The product of the error and the height must not exceed 0.45 ゜ feet.

[Brief description of the drawings]

FIG. 1 is a diagram showing the concept of an antenna system including a three-level spatial filter in which a signal supplied to an antenna input port is sent to an antenna element associated with the port and an antenna element adjacent to the associated element; 2 is a plan view of the printed circuit coupling network of the three-level spatial filter shown in FIG. 1, and FIG. 3 is an antenna system according to the present invention in which the three-level spatial filter is cascaded with the four-level spatial filter. FIG. 4 is a plan view showing a printed circuit coupling network of the cascaded spatial filter shown in FIG. 3, and FIGS. 5a, 5b and 5c are 2 FIG. 6a shows the antenna pattern of an antenna according to the invention using a spatial filter having three-level, three-level and four-level coupling, FIG. FIG. 6b is a list of equations defining the coupling and termination connection values, FIG. 6c is a circuit diagram illustrating a series-coupled network, FIG. 6d is a diagram generally illustrating a five-level spatial filter, FIG. FIG. 7 is a diagram showing a prototype network for an infinite spatial filter antenna used in the present invention; FIG. 8a is a schematic diagram showing an antenna system of two cascaded 8-coupler spatial filters according to the present invention; Figure 8 is a table showing the optimal excitation of an 8-port spatial filter according to the invention; Figure 8c is a circuit diagram showing a unit cell of a module antenna system of two cascaded 4-coupler spatial filters according to the invention; And FIG. 10 shows the calculated antenna pattern for the zero-diluted spatial filter shown in FIG. 8a, and FIG. 11 shows the deviation of the MLS guidance angle from the actual angle from the ideal relationship. Limit FIG. 12 shows the geometry and formula of a model in a flat horizontal plane used to quantify the effect of side rope radiation on the performance of an automatic flight control system; and Figures 13, 14, and 15 show vertical acceleration, vertical velocity, and vertical attitude, respectively, for antenna phase center heights of 10 feet and 20 feet when considering the ride comfort of passengers. FIG. 9 is a diagram schematically showing the simulation result of FIG. 1-8: Antenna element 9-16: Output port 17: Spatial filter 18-25: Input port 26-33: Phase shifter 34: Beam steering unit 34-42: Phase shifter Input 43 Power divider 44 Signal generator 54 Control unit 56-63, 72-80 Coupler 64-71 Transmission line 81, 82, 83 Terminator 109-116 Coupler 300 …… Spatial filter

Claims (15)

(57) [Claims] 1. An antenna system for radiating a wave energy signal to a selected angular region of space in a desired radiation pattern, said spatial filter means having N input ports and N corresponding output ports. Where N is a number greater than 5, and the signal from each of the input ports is
A spatial filter means comprising a network of couplers for coupling with the same phase to the corresponding output port and to at least two other output ports on at least one side of the corresponding port; An aperture comprising a plurality of N antenna elements disposed along the aperture, each element coupled to only one output port of the spatial filter means; and a beam steering means for controlling a direction of the radiation pattern. Wherein there are N phase shifters, each phase shifter having a phase shifter input port and a phase shifter output port coupled to only one input port of the spatial filter means. Beam steering means and a supply means for providing a wave energy signal, the signal generator providing a signal to a power splitter having N signal output ports. Supply means such that each of the output ports is coupled to only one phase shifter, such that when a wave energy signal is provided by the signal generator through the power splitter, The signal provided by the signal output port of the antenna is coupled to the antenna element associated with the output port and at least two adjacent antenna elements on at least one side of the antenna element associated with the output port, wherein the aperture is the desired aperture. An antenna system for causing a radiation pattern to radiate primarily in selected areas of the space without grating ropes. 2. The spatial filter according to claim 1, further comprising: a plurality of N first coupling means, a plurality of N second coupling means, and a plurality of N third coupling means. Each of the coupling means has a first input port, a first coupling output port, and a first transmission output port, the first coupling means being directed to its first input port. The transmitted signal is distributed to the first coupling output port and the first transmission output port based on a first predetermined ratio. The N first input ports are N input ports of the spatial filter, and the N second coupling means includes the N first input ports.
Interposed between the coupling means, each of which has a second left input port associated with a first coupling output port of the first coupling means adjacent to its right and a first left input port of the first coupling means adjacent to its left.
And a second right input port associated with the second transmission output port of the first and second transmission output ports, wherein the second means has a second combined output port and a second transmission output port, and the second combining means has Losslessly combining and distributing the wave energy signals sent to the second left and second right input ports, wherein such sent signals are based on a second predetermined ratio. Distributed to a second coupling output port and a second transmission output port, wherein the N third coupling means are interposed between the N second coupling means, each of which is adjacent to its right. A third left input port associated with the second coupled output port of the second coupling means and a third right input port associated with the second transmit output port of the second coupling means adjacent to the left. Wherein the third coupling means has a third output port and the third coupling means The stage combines losslessly the wave energy signals sent to the third left input port and the third right input port, such signals being sent to a third predetermined ratio. 2. The filter of claim 1, wherein the third output ports are coupled and provided by a third coupled output port, wherein the N third output ports are the N output ports of the spatial filter.
System. 3. The system according to claim 2, wherein said first predetermined ratio is equal to said third predetermined ratio. 4. The second predetermined ratio (C2) is given by the following equation: 4. The system according to claim 3, wherein the system is related to the first predetermined ratio (C1) based on 5. The spatial filter further comprises a plurality of N fourth coupling means disposed between the second means and the third means, each of the N fourth means comprising: Interposed between the N second coupling means, each of which is adjacent to its right a fourth left input port associated with the second coupling output port of the first coupling means and adjacent to its left. A fourth right input port associated with the second transmission output port of the first coupling means, the fourth means comprising a fourth coupling output port associated with the third right input port; And a fourth transmission output port associated with the third left input port, wherein the fourth coupling means losslessly transmits the wave energy signal sent to the fourth left and fourth right input ports. And the signal transmitted in this manner is divided into a plurality of signals based on a fourth predetermined ratio. The system of claim 2 which is of the distributed combined output port and a fourth transmission output port. 6. The system according to claim 5, wherein said first predetermined ratio is equal to said third predetermined ratio and said second predetermined ratio is equal to said fourth predetermined ratio. 7. The second predetermined ratio (C2) is given by the following equation: 7. The system according to claim 6, wherein the system is related to the first predetermined ratio (C1) based on 8. The spatial filter includes a distribution unit, a first transmission unit, and a coupling unit, wherein the distribution unit includes:
It has N distribution input ports and 2N distribution output ports, and distributes the wave energy signal sent to the distribution input port without loss. The distribution input ports are distributed based on a first predetermined ratio, and the N distribution input ports are N filters of the spatial filter.
Input ports, wherein the first transmitting means has 2N first transmission input ports and 2N first transmission output ports respectively associated with only one of the 2N distribution output ports. The first transmitting means couples and distributes the wave energy signal transmitted to the first transmission input port without loss, and the signal transmitted in this way has a second predetermined ratio. And distributed to the first transmission ports, the coupling means comprising: 2N coupling input ports each associated with only one of the 2N first transmission output ports; and N coupling output ports. The coupling means is for coupling the wave energy signals sent to the 2N coupling input ports without loss, and the transmitted signal is a third predetermined signal. Based on the ratio at the combined output port
The system of claim 1, wherein the combined output ports are N input ports of a spatial filter. 9. The system of claim 8, wherein said first predetermined ratio is equal to said third predetermined ratio. 10. The second predetermined ratio (C2) is given by the following equation: 10. The system according to claim 9, wherein the system is related to the first predetermined ratio (C1) based on: 11. The spatial filter further comprises second transmitting means disposed between the first transmitting means and the synthesizing means, wherein the second transmitting means comprises 2N There are 2N second transmission input ports each associated with only one of the first transmission output ports and 2N second transmission output ports each associated with only one of the 2N coupling input ports. The second transmitting means is for coupling and distributing the wave energy signal transmitted to the second transmission input port without loss, and the transmitted signal is the fourth signal. 9. The system of claim 8, wherein said system is combined and distributed to said transmit output port based on a predetermined ratio. 12. The system of claim 11, wherein said first predetermined ratio is equal to said third predetermined ratio and said second predetermined ratio is equal to said fourth predetermined ratio. 13. The second predetermined ratio (C2) is given by the following equation: 13. The system according to claim 12, wherein the system is related to the first predetermined ratio (C1) based on: 14. The filter according to claim 14, wherein the filter comprises: N input ports;
The system of claim 1 comprising first and second cascaded lossless spatial filters having N output ports. 15. The system according to claim 2, wherein the spatial filter is a printed circuit arranged on a single substrate.