JPH01218105A - Phasing array antenna with space filter structure coupler - Google Patents

Abstract

PURPOSE: To radiate a wave energy signal within the selected area of a space by providing a spatial filter having no loss between the input port and antenna element of an antenna. CONSTITUTION: A beam steering unit 34 controls the direction of radiation and is provided with N pieces of phase shifters 26-33 and a means 54 for controlling these phase shifters 26-33. The respective phase shifters 26-33 have phase shift input ports 18-25 and phase shift output ports 9-16, and these output ports 9-16 are connected to only one of input ports 18-25 of a spatial filter 17. The energy signal supplied by a signal generator 44 is supplied through a line 45 to a power divider 43 and this divider divides the signal into eight equal components. The respective components are sent through lines 46-53 to only one input of the beam steering unit 34. Thus, the wave energy signal can be radiated in the selected angle area and desired angle pattern of the space.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an array antenna system, and more particularly, a lossless spatial filter is provided between an input port of an antenna and an antenna element, and each input port is provided with a lossless spatial filter. The present invention relates to a system in which the antenna element pattern is modified by causing the associated effective element pattern to primarily fall within a selected angular region of space.

Prior art array antenna systems are designed to transmit a desired radiation pattern toward one of a plurality of angular directions within a selected spatial region. According to known designs of such array antennas, each antenna element has an input port associated with it. By varying the amplitude and/or phase of the wave energy signal delivered to the input port, the antenna pattern can be electronically steered in space to orient the desired radiation direction, or by changing the time-based beam scanning pattern. The antenna pattern can also be controlled to radiate desired signal characteristics such as:

If it is desired that the array antenna radiate its beam over a selected limited spatial region, it is preferred that the radiation pattern of an individual antenna element also fall primarily within the selected angular region. .

This allows the element spacing to be maximized while suppressing undesirable grating lobes.

In these systems, it is not possible to control the element pattern by changing the physical shape of the antenna elements. This is because obtaining the desired device pattern requires an element aperture size that exceeds the required element spacing of the array. A practical solution to overcome physical element size constraints is to divide each antenna input port into two such that the effective element pattern associated with each input port is formed by the combined radiation of a large number of elements.
providing a network interconnecting two or more antenna elements. These networks can be realized by printed circuit technology using a single substrate layer.

One known solution to this problem is U.S. Pat.
, No. 803,625.

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 a degree of control over the radiated antenna pattern.

A further effective known antenna coupling network is disclosed in U.S. Pat. No. 4,041 to Frazita et al., incorporated herein by reference and assigned to the same assignee as the present invention.
No. 501. According to Frajita's technique, the antenna elements are configured as element modules, and each module is provided with an input port.

A transmission line is connected to all antenna element modules in the array. Transmission lines connect signals sent to either port to selected elements of all antenna element modules in the array. This antenna (hereinafter referred to as
(referred to as a COMPACT antenna) is
Provide an array aperture and a spacing effective element aperture.

Yet another effective known antenna coupling network is disclosed in U.S. Pat. No. 4,143.379 to Wheeler, assigned to the same assignee as the present invention and incorporated herein by reference. According to Wheeler's technique, wave energy signals are coupled to adjacent modules using cross-coupling ports.

Yet another technique is disclosed in U.S. Pat. No. 4,168, which describes an antenna array having a printed circuit lens in the coupling network.
, No. 503.

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 include a plurality of vertically upright, circularly arranged printed circuit panels, each with a conductive strip connected at one end to a respective antenna. A plurality of semi-elliptical circuit panels are fixed to the vertical panel at predetermined angles. A metal strip plated on the semi-elliptical panel provides the desired delay to the antenna signal. A synthesis strip is connected to this time delay strip, which produces a half-elliptical pattern of synthesis output signals at one end thereof. The angle at which the semi-elliptical board is fixed to the vertical board corrects for time delay distortion caused by the placement of the composite strips.

This configuration cannot be implemented using integrated circuit technology in a single substrate layer.

U.S. Pat. No. 4,321,605 discloses an array antenna system in which the ratio of antenna elements to input terminals interconnected via negative order transmission lines 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 input terminal is connected primarily to the element corresponding to that input terminal, and also to other selected elements.

Problem to be Solved by the Invention In time-based scanning beam systems such as microwave landing systems (MLS), linearity is required for runway guidance, i.e. the difference between the actual and commanded angles. must be within a limited range. It is also necessary to minimize the field monitor distance to the airstrip antenna. Specifically, in MLS, the present invention provides a undiluted 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 the input port of the antenna element and the antenna element.

Another object of the present invention is to provide a non-reduced antenna system, i.e. the number of antenna input ports is equal to the number of output ports of the antenna element, so that there is no reduction ratio between the number of radiators and the number of phase shifters. The purpose of the present invention is to provide such an antenna system.

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

Yet another object of the invention is to provide a lossless spatial filter with a 1:1 input/output ratio and using a minimum number of couplers and termination connections.

Yet another object of the present invention is to provide a lossless spatial filter that is flexible in controlling its radiation pattern, meeting linearity requirements, and minimizing field monitor distances. be.

According to the invention, an antenna system radiates wave energy signals into a selected angular region of space and a desired angular pattern. The antenna system has N input ports;
and a lossless spatial filter having 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 the 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 that supplies a signal to a power divider having N output signal ports, each output port being connected to only one phase shift input port.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the invention, the invention will now be described in detail with reference to the accompanying drawings. The scope of the invention is pointed out in the claims.

FIG. 1 is a circuit diagram showing an antenna system according to the invention. FIG. 1 shows a plurality of antenna elements 1-8 arranged along a predetermined path (in this case, a straight line).

Each antenna element includes one and one of the spatial filters 17.
It is connected to only one output port 9-16. The spatial filter is composed of a plurality of modules A to H, one for each antenna element. The spatial filter 17 includes eight input ports (18-25),
Each of them has one and only one phase shifter 26-33.
connected to the output of The array of phase shifters 26-33 forms a beam steering unit 34. Phase shifter input 3
5-42 is connected to one and only one output of the power divider 43, which is signaled by a signal generator 44.

The power divider and the signal generator form supply means for supplying the wave energy signal. Although filter 17 is shown as symmetrical, it is contemplated that spatial filters according to the present invention may be asymmetrical.

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, considering the leftmost part of the antenna system, line 46 supplies the 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 commands received via control line 55 from control unit 54. The output of phase shifter 26 is sent to input port 18 of spatial filter 17. The signal component fed to the input port 18 is fed to the output port 9 connected to the antenna element 1 and also fed by the coupling arrangement to the element 2 adjacent to the antenna element 1 .

Spatial filter 17 couples the component signals provided at its input to the antenna element associated with its input and to elements adjacent to this associated element. Coupler 56-63 couples the signal provided to the associated antenna element to the antenna element to the left of the associated antenna element. The component signals provided to the inputs are routed by transmission lines 64-71 to the antenna elements associated with that input. For example, the component signals provided by branch 39 of power divider 43 are provided via phase shifter 30 and provided to input 22 of spatial filter 17 . This input 22 is connected by a transmission line 68 to its associated output 13 and to the antenna element 5 . The component signals are also coupled by coupler 59 to antenna element 4 adjacent to the left side of antenna element 5 .

Similarly, the component signals provided to the inputs are coupled to coupler 72-
It is also coupled by 80 to the antenna element adjacent to the right of the associated antenna element. For example, power divider crossroads 4
The component signals provided by 9 pass through a phase shifter 29 and are provided to the input 21 of the spatial filter 17 . This component signal is then

It is sent to output 12 by transmission line 67. Output 12
is directly connected to the antenna element 4. Element 5 is adjacent to the right side of antenna element 4 and receives and takes away a portion of the component signals via coupler 76. Element 3 is adjacent to the left side of antenna element 4 and receives and takes away a portion of the component signal via coupler 58.

Spatial filter 171i: shown in modular form. Therefore, the input to the coupler 72 is the terminal connection 8
Connected by 1. This is because there is no antenna element on the left side of antenna element 1. Similarly, the output from coupler 56 is connected by termination connection 82 . This is because there is no antenna element to the left of antenna element 1 for receiving and receiving the component signals applied to input 18. On the right side of the spatial filter 17, the coupler 8
0 is connected by a terminal connection 83 , and the coupler 63 is connected by a terminal connection 84 . This is because the coupling signal from coupler 80 is received or taken from coupler 63.
The antenna element that supplies the combined signal via the antenna element 8
This is because it is not on the right side of .

FIG. 2 is a top view of a printed circuit combination network useful as the spatial filter 17 of FIG.

This network 17 has input ports 18-25 connected to the output of the beam steering unit 34. These input ports are connected to a first series of couplers C1, shown in detail in Figure 2a.

Coupler C1 and all other couplers are standard microstrip network couplers with predetermined coupling ratios. The specific coupling ratio depends on the width of the transmission line in the coupler,
Depends on length and thickness. Usually, coupler C1
The signals sent to inputs 101 and 102 of are connected to outputs 103 and 104 based on a predetermined ratio. In the case of coupler C1, input 102 is connected by a termination connection 105, and any component signal sent to input 101 is distributed to outputs 103 and 104, so that C12+T1''=1
It is made to be.

Following the 17th lay of coupler C1 is the 27th lay of coupler C2, which is shown in detail in Figure 2b. input 105
and 106 are combined and sent to output 108 at ratio T2 and to output 107 at ratio C2, such that T2''+C2''=1. Completing the three-level spatial filter 17 is a third series of couplers 109-116. According to the 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 fed to their inputs with the outputs 9-16 of spatial filter 17.

As defined by the present invention, the spatial filter 17 is ideally lossless (apart from dissipative losses), so that the power (voltage) passing through each coupler C1 and T1 respectively is: relationship must be applied.

C12+T1''==1 and C2''+T2''=1 A lossless condition for the network is ensured by the following relationship.

C1"=1/2 (1+f = τ") (1) This relationship can be solved by setting inputs 18-25 equal to 1 and inputs to termination connections 117-124 equal to 0. can be derived.

[Non-rarefaction spatial filter] 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 is a circuit diagram of an antenna system according to the invention including a 3/4 level cascaded spatial filter 300. Generally, the spatial filter 17 of the antenna system shown in FIG.
By replacing it with 00, it can be used in combination with the antenna system shown in FIG. Each antenna element 1-8
are connected to one and only one output port 301 of spatial filter 300. Spatial filter 300 is comprised of a plurality of modules A-H, one for each antenna element. Spatial filter 300 includes input ports 302 each connected to one and only one output of the phase shifting network.

FIG. 4 is a top view of the printed circuit combination 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 C1, shown in detail in Figure 2a. Following the 17th lay of coupler C1 is the 27th lay of coupler C2, which is shown in detail in Figure 2b. Following the 27th lay of coupler C2, there is the 37th lay of coupler C2. Completing the four-level spatial filter 300 is a fourth series of couplers C
According to the invention, the couplers C1 at the beginning and end of the array and the middle coupler C2 are of the same configuration in order to achieve symmetrical excitation. The following relation ensures a lossless state for the network.

C1''=1/2+C2r and 2'' (2) Figure 5a shows an ideal antenna pattern for an antenna according to the invention using a spatial filter with two-level coupling. In such a coupling, essentially the lobe 50
1.502 and 503 are formed. FIG. 5b shows a typical antenna pattern with a three-level spatial filter forming a single lobe 504. FIG. FIG. 5C shows a typical antenna pattern for a four-level spatial filter that produces a very well defined single probe 505.

A for a 5-level non-sparse spatial filter Step 1: Figures 6a, 6b, 6c and 6d
Referring to the diagram, determine the initial values of couplers C1-C5.

(a) Specify the desired excitation Al-A3 (b) Specify C1 (c) Calculate C2-C5 using Figure 6c Step 2: Actual excitation Al'-A5 based on the following formula
′ is calculated.

(a) Al' = C5C4C3T2C1 (b) A2'
=C5T4C3C2C1-T5T4T3C2C1 -T5C4T3T2T1 -T5C4C3T2T1 (c) A3' =C5C4T3C2C1-T5C4T3
C2T1 -T5T4T3T2T1 -T5T4C3T2C1 -C5T4C3T2T1 -C5T4T3T2C1 (d) A4' = C5C4C3T2C1 - T5T4C
3C2T1 -C5T4T3C:2T1 -C5C4T3T2T1 (e) A5' = C5C403C2T1
Step 3: Adjust the values of couplers C2-C5.

(a) Adjust 05 as follows.

A2'　A2 Al'　Al (b) Adjust C4 as follows.

A3' A3 A2'　A2 (c) Adjust 03 as follows.

A4' A4 A3' A3 (d) Adjust C2 as follows.

A5' A3 A4' A4 Step 4: Calculate the actual excitation Al' - A5' again. (See step 2 for the formula for Al'-A5') Step 5: Normalize the actual excitation by calculating A1''-As2.

(a) A”=1. Therefore.

(b) A2"=A2'/Al' (c) A3"=A3'/Al' (d) A4"=A4'/Al' (e) A5"=A5'/Al' Step 6: Normalization Actual excitation Al''-As2
and the desired excitation Al-A3.

Σ(AN)” N=1.2...5 Step 7: Step 3 until the deviation S is within the allowable range
-Repeat step 6.

Step 8: Repeat steps 1-7 until R, where the ratio of the termination power P and the radiated power PR, ie P/P, is minimized.

P = Σ (T N)": pR = Σ (AN)" 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.

Al=1.0000 A2=1.6086 A3=1. 93156 A4=1.6086 A5=1.0000 Here, if c1=o, 979 (from step 1b), the values of the other couplers are as follows.

C2=0.9502 C3=0.9366 C4=0. 9600 cs=o, 9852 The normalized actual excitation (steps 2-5) yields:

A1=1 A2=1.3755 A3=1.6478 A4=1.5449 A5=1.1957 dB loss between normalized actual excitation (from step 5) and desired excitation (step la) (Step 8
) becomes as follows.

LOSS=7.12 dB The synthesis procedure continues with Table 1 below.

Beni 5 Katsupura's synthetic cut CI C2 Ying q Aka ni g W Kabegaeshi 1.979
．． 9225.8401.9042.97911.606
11.9321.606116.72dB2.98.9
285.857.9132.9811.6081.93
21.61116.59dB3.985.953.91
55.9461.98511.6081.9331.6
0416.69dB4.99.971.9523.96
85.9911.6081.9311.60917.6
8dB5.981.9343.8718.9212.9
811.60851.9321.608516.53d
BAs shown in Table 1, Trial 5 shows the optimal configuration with minimum power loss6As shown in Table 2, Trial 4
The optimal configuration is shown for a five-coupler structure that must be excited symmetrically to set C5=C:1 and C4=C2.

No L Rei 5 Combination of Katsupura C3=C1, C4=C2 Trial 9 q Competition Rainbow 婬岨 Dangyoku 1 . 98
1.91506.8401 11.60861.932
6.93dB2. 979.8823. 857 1
1.60861.9318 7.90dB3. 982
．． 92425. 915511.60861.932
6.80dB4. 984.93866.952311
．． 60861.9321 6.75dB5. 986.
95011. 87181 1.60861.932
6.90 dB Although the above procedure was applied to develop symmetric filters, it is of general nature and can also be used to develop asymmetric filters. Symmetry generally refers to maintaining simplicity while reducing complexity; symmetrical filters typically
It uses redundant couplers and other structures that minimize design effort.

Spatial filter design involves determining coupling values for multilayer circuits. A non-closed form of solution will be readily apparent for the synthesis of a network that forms a particular output voltage distribution. However, analysis of any circuit network is possible. Synthesis therefore involves the iterative trial and error procedure described above in which the combination values are gradually adjusted until the desired output is obtained.

Since the computational time required to analyze complex networks is significant, it is desirable to form iterative algorithms that converge on the desired solution in a reasonable amount of time. When analyzing each combination of combined values, it takes several weeks or months for computer evaluation. Moreover, there are an unlimited number of solutions for creating the desired amplitude distribution.

The difference between these solutions is the resulting network insertion loss. 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 a spatial filter network is determined by the idea that power is conserved.

A prototype of this network is shown in FIG. This network is symmetrical and continues indefinitely in both directions. Each input excites a subarray with N outputs. The outputs of the subarrays resulting from adjacent inputs overlap. The network shown in FIG. 7 has the same number of inputs and outputs. Therefore, the input and output spacing is equal and when all inputs are excited, each output port is the sum of the effects from the N input ports. Internal termination connections must be made for each output port.

The output excitation resulting from input 1 is designated A I (N) and the output excitation resulting from input 0 is designated A O (N). Since the network is symmetric, A1 (N)=
A O (N) = A j (N). Similarly, B
The terminated powers, denoted j (N), must also be equal.

This network is implemented with N layers of directional couplers. To obtain the desired symmetry, all coupling values for a given layer must be equal. Moreover, the symmetrical output excitation (A
j(1)=Aj(N), Aj(2)=Aj(N-1),
etc.) requires that the combined value of the first layer is equal to the combined value of the Nth layer, and so on. So, for example, an 8-output network has 8 layers of couplers. If the 8-element excitation is symmetric, C1 (the coupling value of all couplers in the first layer) must be equal to 08, and C2=C
7. Must be C3=C6, C4=C5. Therefore, there are only four separate combination values or unknowns that must be determined for the eight output network.

When input power is applied to port 1, power conservation requires that the sum of the powers of A 1 (N) applied to the internal termination (Bl(N)) must be equal to the input power. be instructed.

Normalization for an input power of 1 watt gives the following equation: % A and B are voltage coefficients. The power at each output port is equal to the square of the voltage coefficient when the system impedance 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 N voltages. Due to symmetry and conservation of power, the sum of the powers at one output port and its internal termination connections must equal one watt. All output ports are equal.

i=1 i=1 By combining equations (3) and (4), we get the following.

i=1 1=1 i=1 i=1 If there must be no losses in the network, the internal terminations cannot be powered when a single input port is energized ( all B=0). If this condition exists, then:

Only a few output excitations satisfy equation (6). In the following cases, the maximum /
A loss of h limit occurs.

[Σ B 1 (N)] ”= O or i=1 Σ B 1 (N) = O(7) i:1 If this condition is satisfied, all input ports are excited with the same amplitude and phase. When a single input port is excited and the subarray patterns have a maximum value in the same phase direction, the loss is given by the following equation.

i=1 i=1 When the subarray pattern has a maximum in a direction other than the in-phase direction, the lower bound on loss is increased by the difference in subarray gain in the two directions. An optimal network is one that produces the least amount of loss. The predictable loss is the difference between the calculated network loss and the theoretical value.

Therefore, the theoretical minimum loss is calculated using equation (8) to be 3.1 dB when a single input port is energized, and the minimum that can be obtained in practice with a realizable network. It was found that when the loss of 4.6 dB, the loss when all inputs are excited in the same phase becomes 1.5 dB. This 1.5 dB loss is obtained by considering the center of the subarray pattern. The theoretical loss is reduced to zero when the array is scanned for the subarray peak.

The basic topology of spatial filter networks is well known. In the preferred embodiment, 17 layers are required;
It is possible 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 required linearity of the MLS gliding glide. This linearity will be explained with a focus on altitude guidance performance, but linearity is also required for azimuth guidance. Linearity is something that has been heavily considered in the MLS industry. The present invention provides a phased array antenna that meets high linearity requirements. Spatial filter networks are a practical way to meet low efficiency side lobe requirements that are directly related to linearity requirements.

The linearity (autopilot) requirement limits the extent to which the MLS guided angle and the actual angle (see FIG. 11) deviate from the ideal linear relationship. This is PFN and CMN
Specifies the lateral precision characteristics of the angular guidance signal rather than the longitudinal characteristics of the angular guidance signal. Longitudinal characteristics may cause the aircraft to deviate from the runway (turn) or cause noisy operation of the control equipment.

Lateral characteristics can lead to instability in automatic flight control systems.

After several years of consideration in the MLS industry, today...
It has become generally accepted that the PFN, CMN and linearity for EL induction devices are all based on the effective side lobe level of the antenna. Three characteristics (PFN, C
MN or linearity) is the driver for the specification of effective side lobe levels. Path following noise (PFN) is related to the path following average course error and is caused by the frequency components that the aircraft is able to follow. Controlled movement noise (CMN)
exists without any PFN occurring, but the scanned M
The LS signal indicates a rebound or deviation that the aircraft cannot follow. Initially.

It was discussed that PFN was the driver. 1°5°
The effective side lobe level required to ensure that the PFN does not exceed 0.083" for a beamwidth antenna of 0.083' from the CAOM scale.
(The PFN limit is derived). After analysis by the FAA, it was determined that CMN occurs when the aircraft is within 2000 feet of the runway threshold when the phase center of the antenna is 20 feet above the reflective ground. Therefore, in the FAA's second draft specification for MLS acquisition, effective side lobe levels are specified 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 an actual automatic flight control system, it has been concluded that linearity is the most stringent requirement for the specification of effective side lobe levels. The simulation results indicate that the angular error limit should not exceed 0.024° to ensure the performance of the automatic flight control system is within a level that is comfortable for passengers. This error limit corresponds to an effective side lobe level of -36 dB for a 1.5'' beamwidth antenna.

After consideration of linearity requirements, a measurement methodology was published to determine compliance with specifications. In this regard, it should be understood that effective side lobes can be measured at antenna ranges and design certification by authorities can be performed based on these antenna measurement ranges.

The side lobes radiated by the altitude antenna in the direction of the ground are caused to fold onto the main beam by specular reflection. This side lobe radiation distorts the beam and PF
N, CMN and linearity errors. The PFN and CMN specifications limit the magnitude of the angular guidance error. However, the linearity error will be based on the product of the maximum angular guidance error and the height of the antenna phase center above the reflective ground. If this error multiplied by height is large, the guidance 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 phase center height is 20 feet, then the loop gains are +6 dB and -40 dB ("maximum gain spot" and "dead spot" in Figure 11). Varies between:

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

This model was used as a disturbance input to simulate a small jet aircraft's automatic glide ramp control system. The criterion for the suitability of automatic flight control systems is whether passengers feel comfortable. Figures 13 and 14
The figures and FIG. 15 schematically illustrate the simulated results for acceptable peak MLS guidance error, altitude antenna phase center height and passenger comfort. The simulation begins at a distance of jNM from the altitude antenna.

Figure 13 shows a phase center height of 20 feet and 0.083
” indicates that the automatic control system is unstable. The vertical acceleration is 2.4:1.
The coefficient exceeds the level that passengers feel is comfortable. 0.
For a peak error of 045°, the system is barely stable; if the phase center height is large, say 37 feet, the system is expected to become unstable (the error height product 0 .045° x 37' is equivalent to a maximum error of 0.083" and a height of 20 feet). Figures 14 and 15 show the same trend, with a phase center height of 20 feet. feet and the peak error is 0.083°, the vertical velocity and attitude are each 4
It is shown that the coefficients of :1 and 2:1 exceed the level that passengers feel comfortable.

By studying the information available for the specification of effective side lobe levels and autopilot performance within the level of passenger comfort, the following conclusions are reached.

1. Current PFN error limit (0,083') is unacceptable.

2. The current 0MN error limit (0,045') is barely acceptable (especially if high antenna phase center heights of 20 feet or more are intended).

3. A limit of 0.024'' is considered acceptable for the investigated case.

4. Linearity is the main system requirement for the specification of effective side lobe levels.

5. The product of error and height shall not exceed 0.45” feet.

[Brief explanation of the drawing]

1 is a diagram illustrating the concept of an antenna system including a three-level spatial filter such that a signal applied to an antenna input port is routed to an antenna element associated with that port and an antenna element adjacent to the associated element; FIG. 2 is a plan view of the printed circuit combination network of the three-level spatial filter shown in FIG. 1, and FIG. 3 is an antenna system according to the invention in which the three-level spatial filter is cascaded with a four-level spatial filter. Diagram showing the concept. 4 is a plan view of the printed circuit combination network of the cascaded spatial filter shown in FIG. 3; FIGS. 5a, 5b and 5c are two-level,
Figure 6a shows a schematic diagram of the coupler and its associated inputs and outputs; Figure 6b shows the coupling values and terminations. List of equations defining connection values. Figure 6c is a circuit diagram showing a series coupled network. FIG. 6d shows a general view of a five-level spatial filter; FIG. 7 shows a prototype network for an infinite spatial filter antenna used in the invention; FIG. 8a shows two FIG. 8b is a table showing the optimum excitation of the 8-point spatial filter according to the invention; FIG. The circuit diagrams illustrating the unit cells of the module antenna system of the four-power Tsupra spatial filter, Figures 9 and 10, are shown in Figure 8a.
FIG. 11 shows the calculated antenna pattern for the zero-rarefaction spatial filter shown in FIG. The graphs, Figure 12, illustrate the geometry and equations of a flat horizontal model used to quantify the effect of side lobe radiation on the performance of automatic flight control systems. Figure 15 shows the simulated results of vertical acceleration, vertical velocity, and vertical attitude for the antenna phase center heights of 10 feet and 20 feet when considering passenger ride comfort, respectively, and the peak MLS induced error. 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...Terminal connection part 109-116...Coupler 300...Spatial filter ↑J Pattern angle (degree) Pattern angle (degree) FIG, 10

Claims (1)

[Claims] (1) An antenna system for radiating wave energy signals into a selected angular region of space in a desired radiation pattern, comprising: a lossless antenna system having N input ports and N output ports; a spatial filter; an aperture consisting of a plurality of N antenna elements arranged along a predetermined path, each element being connected to only one output port of the spatial filter; N phase shifters; comprising means for controlling this phase shifter;
each phase shifter comprises: a beam steering unit having a phase shift input port and a phase shift output port connected to only one input port of said filter; and supply means for providing a wave energy signal. The supply means includes a signal generator for supplying a signal to a power voltage divider having N signal output ports, each of which is connected to only one phase shift input port. supply means such that when a wave energy signal is supplied by said signal generator through a power voltage divider, the signal supplied by the signal output port of the power divider is connected to said output port. An antenna system coupled to an antenna element and an antenna element adjacent thereto, characterized in that the aperture causes the desired radiation pattern to be radiated primarily within a selected region of the space without grating lobes. (2) The spatial filter includes a plurality of N first coupling means, a plurality of N second coupling means, and a plurality of N third coupling means, and the first coupling means each has a first input port, a first coupling output port, and a first transmission output port, and the first coupling means includes:
The wave energy signal sent to the first input port is distributed without loss, and such sent signal is distributed to the first combined output port and the first combined output port based on a first predetermined ratio. The N first input ports are the N input ports of the spatial filter, and the N second coupling means are distributed between the N first coupling means. , each of which has a first
a second left input port associated with the first coupling output port of the coupling means and a second right input port associated with the first transmission output port of the first coupling means adjacent to the left thereof; , the second means has a second coupling output port and a second transmission output port, the second coupling means transmitting a wave energy signal to its second left and second right input ports. The transmitted signal is distributed to the second combination output port and the second transmission output port based on a second predetermined ratio,
The N third coupling means are interposed between the N second coupling means, each of which has a third coupling output port associated with the second coupling output port of the second coupling means adjacent to the right thereof. a left input port and a third right input port associated with a second transmission output port of the second coupling means adjacent to the left thereof, said third coupling means having a third output port; The third coupling means couples the wave energy signals sent to the third left input port and the third right input port without loss, and such sent signals are , and wherein the N third output ports are the N output ports of the spatial filter. . 3. The system of claim 2, wherein the first predetermined ratio is equal to the third predetermined ratio. (4) The second predetermined ratio (C2) is calculated using the following formula C1^2
4. The system according to claim 3, wherein said first predetermined ratio (C1) is related to said first predetermined ratio (C1) on the basis of =1/2(1+√(f1-C2^2)). (5) The spatial filter further includes the second means and the third means.
and a plurality of N fourth coupling means disposed between the N fourth coupling means, each of the N fourth coupling means being interposed between the N second coupling means, and each of the N fourth coupling means having: a fourth coupling output port associated with the second coupling output port of the first coupling means adjacent to the right thereof;
and a fourth right input port associated with the second transmission output port of the first coupling means adjacent to the left thereof, the fourth means being connected to the third right input port. an associated fourth coupling output port and a fourth transmitting output port associated with the third left input port;
The coupling means is for coupling and distributing the wave energy signals sent to the fourth left and fourth right input ports without loss, and the signals sent in this way are connected to the fourth predetermined input ports. 3. The system of claim 2, wherein the distribution is based on the ratio between the fourth combined output port and the fourth transmit output port. 6. The system of claim 5, wherein the first predetermined ratio is equal to the third predetermined ratio and the second predetermined ratio is equal to the fourth predetermined ratio. (7) The second predetermined ratio (C2) is calculated using the following formula C1^2
Based on =1/2=C2√(1-C2^2), the above first
7. The system according to claim 6, wherein the system is associated with a predetermined ratio (C1) of . (8) The spatial filter includes a distribution means, a first transmission means, and a coupling means, and the distribution means has N distribution input ports and 2N distribution output ports. The wave energy signal sent to the distribution input port is distributed without loss, and the signal sent in this way is distributed to the distribution output port based on the first predetermined ratio, and the wave energy signal sent to the distribution input port is distributed to the distribution output port based on the first predetermined ratio. The distribution input ports of are the N input ports of the spatial filter, and the first transmitting means is
2N each associated with only one of the 2N distribution output ports
The first transmission means has 2N first transmission input ports and 2N first transmission output ports, and the first transmission means combines and distributes the wave energy signals sent to the first transmission input ports without loss. The signal sent in this way is
are coupled and distributed to the first transmission ports based on a predetermined ratio of N
The coupling means has a coupling output port of
The wave energy signals sent to the 2N combined input ports are combined without loss, and these sent signals are combined at the combined output port based on a third predetermined ratio, 2. The system of claim 1, wherein the N combined output ports are N input ports of a spatial filter. 9. The system of claim 8, wherein the first predetermined ratio is equal to the third predetermined ratio. (10) The second predetermined ratio (C2) is calculated using the following formula C1^2
10. The system according to claim 9, wherein said first predetermined ratio (C1) is related to said first predetermined ratio (C1) on the basis of =1/2(1+√(1-C2^2)). (11) The spatial filter further includes a second transmitting means disposed between the first transmitting means and the combining means, and the second transmitting means includes 2N first transmitting means. 2N second transmit input ports each associated with only one of the transmit output ports, and 2N second transmit output ports each associated with only one of the 2N combined input ports; The second transmission means is for combining and distributing the wave energy signal sent to the second transmission input port without loss, and such a sent signal is transmitted to a fourth predetermined signal. 9. The system of claim 8, wherein the transmission output ports are combined and distributed based on a ratio. 12. The system of claim 11, wherein the first predetermined ratio is equal to the third predetermined ratio and the second predetermined ratio is equal to the fourth predetermined ratio. (13) The second predetermined ratio (C2) is calculated by the following formula C1^2
Based on =1/2+C2√(1-C2^2), the above first
13. The system according to claim 12, associated with a predetermined ratio (C1) of . 14. The system of claim 1, wherein the filter comprises first and second cascaded lossless spatial filters having N input ports and N output ports. 15. The system of claim 2, wherein the spatial filter is a printed circuit disposed on a single substrate.