Antenna device with lens or passive element acting as lens

An antenna device has a divider producing first and second signals, and amplifiers amplifying the signals at a changeable amplitude ratio of the first signal to the second signal. A Rotman lens gives first phase differences to first high frequency waves, produced from the first amplified signal at an input port and transmitted to output ports, and gives second phase differences to second high frequency waves produced from the second amplified signal at another input port and transmitted to the output ports. An antenna forms a beam composed of electromagnetic waves, having the first phase differences and electric power corresponding to the first amplified signal on an antenna surface, and electromagnetic waves, having the second phase differences and electric power corresponding to the second amplified signal on the antenna surface, and radiates the beam in a particular direction corresponding to the phase differences and the amplitude ratio.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application 2008-243147, filed on Sep. 22, 2008, so that the contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present application relates to an antenna device which forms a beam having a radiation direction freely set by using a lens or a passive element acting as a lens, radiates the beam in the radiation direction and receives the beam reflected by an object to detect the bearing angle to the object.

2. Description of Related Art

An antenna device has been used to radiate a beam of electromagnetic waves while scanning the beam within a predetermined range of scanning angle. Further, this device receives the beam reflected by an object to detect the bearing angle to the object.

For example, a well-known Rotman lens with a Rotman lens pattern acting as wave-guiding channels is used for the antenna device. In this lens, electromagnetic waves induced from a transmission signal are distributed to form a beam directed in a radiation direction, and electromagnetic waves of an incoming beam are combined with one another to produce a reception signal indicating the incoming direction of the beam.

This Rotman lens has a channel pattern, a plurality of antenna ports disposed on one side of the lens, and a plurality of beam ports disposed on another side of the lens. In response to a transmission signal, electromagnetic waves are induced at one specified beam port by magnetic coupling, the induced waves are distributed to the antenna ports through respective channels having different lengths. Therefore, the groups of waves at the antenna ports have respective phases different from one another. In response to these waves at the antenna ports, an array antenna having antenna elements connected with the respective antenna ports forms a transmitting beam. This beam is composed of groups of electromagnetic waves having phase differences. Then, the array antenna radiates this beam in a radiation direction corresponding to these phase differences.

Therefore, each beam port corresponds to one radiation direction of the beam, and the antenna device can radiate a beam in any of radiation directions corresponding to the beam ports.

The antenna device further has a receiving antenna array and a Rotman lens in a beam receiving block. This lens has antenna ports and beam ports. When an incoming beam comes to this antenna array from an incoming direction, antenna elements of the array receive respective groups of electromagnetic waves composing this beam on an antenna surface. The groups of electromagnetic waves at the antenna elements have phase differences corresponding to the incoming direction. Then, in response to this beam, groups of electromagnetic waves having these phase differences are induced at the antenna ports of the Rotman lens by magnetic coupling and are transmitted through respective channels having different lengths to have the same phase at one beam port corresponding to the phase differences. That is, the group of induced waves are combined with one another at the beam port, and a reception signal is produced from the combined waves at the beam port. Because the phase differences of the groups of waves composing the beam corresponds to the incoming direction, each beam port of the lens corresponds to one incoming direction of the beam. Therefore, the antenna device can receive a beam coming from any of incoming directions corresponding to the beam ports.

Accordingly, the antenna device can detect the bearing angle to an object from the reception signal which is produced from a beam coming from any of directions corresponding to the beam ports.

The antenna device performs the beam scanning to radiate a beam, formed by using the Rotman lens, at a scanned angle denoting the radiation direction while changing the scanned angle with respect to time. The number of scanned angles is equal to the number of beam ports. Therefore, the scanned angles are discretely set, and the antenna device performs bearing detection while discretely changing the scanned angle of the scanning beam. In this case, the bearing resolution undesirably becomes low. To heighten this resolution, it is required to increase the number of beam ports. However, the size of the Rotman lens is increased with the number of beam ports, so that it is difficult to manufacture a small-sized antenna device while heightening the bearing resolution in the bearing detection.

To solve this problem, Published Japanese Patent First Publication No. 2003-152422 has proposed an antenna array device. A beam radiated in a particular direction generally has a radiation pattern of electric power with respect to the radiation direction. That is, radiation energy of the beam is maximized in that particular direction, and the beam has also radiation energy in directions surrounding the particular direction. In this device, two beam ports adjacent to each other are changeably selected from many beam ports of a Rotman lens, electromagnetic waves distributed from one selected beam port to antenna ports of the Rotman lens are added with electromagnetic waves distributed from the other selected beam port to the antenna ports, and a transmitting beam induced from the added waves is radiated. Therefore, the beam has a radiation pattern having the maximum radiation energy in the first direction corresponding to one selected beam port and another radiation pattern having the maximum radiation energy in the second direction corresponding to the other selected beam port. The sum of the radiation patterns has a composite pattern having the maximum radiation energy in a third direction placed between the first and second directions. Therefore, the transmitting beam is substantially radiated in the third direction.

Therefore, this conventional device can set scanned angles of which the number is larger than the number of beam ports. Further, this conventional device can also detect each of received beams coming from different directions of which the number is larger than the number of beam ports. Accordingly, the bearing resolution can be heightened in the bearing detection without increasing the number of beam ports.

However, this conventional device requires many selecting switches and a selection controller to appropriately select two beam ports from a large number of beam ports. Because the selection of the beam ports is performed in a cycle corresponding to a frequency in a wide frequency band from several hundreds MHz to tens GHz, it is difficult to manufacture many switches operable in this operating cycle with uniform characteristics. Therefore, it is difficult to manufacture the conventional device operable with high precision.

BRIEF SUMMARY

An object of the present exemplary embodiment is to provide, with due consideration to the drawbacks of the conventional antenna array device, an antenna device which radiates a beam in any direction freely set in a simple structure while using a lens or a passive element having the same function as the function of the lens.

Another object of the present exemplary embodiment is to provide an antenna device which receives a beam coming from any direction in a simple structure while using a lens or a passive element having the same function as the function of the lens.

According to an aspect of this exemplary embodiment, the object is achieved by the provision of an antenna device, comprising a transmission signal producing unit, a transmission signal adjusting unit and a beam forming unit. The producing unit produces a first transmission signal and a second transmission signal. The adjusting unit adjusts the first transmission signal produced by the signal producing unit to have a first amplitude or a first phase and adjusts the second transmission signal produced by the signal producing unit to have a second amplitude or a second phase. The forming unit has a first input portion from which first electromagnetic waves having an amplitude or a phase corresponding to the first amplitude or the first phase of the first transmission signal are transmitted, a second input portion from which second electromagnetic waves having an amplitude or a phase corresponding to the second amplitude or the second phase of the second transmission signal are transmitted, an output portion at which the first electromagnetic waves transmitted from the first input portion have first phase differences while the second electromagnetic waves transmitted from the second input portion have second phase differences, and an antenna surface on which a particular beam, composed of a first portion of electromagnetic waves having the first phase differences and electric power corresponding to electric power of the first electromagnetic waves and a second portion of electromagnetic waves having the second phase differences and electric power corresponding to electric power of the second electromagnetic waves, is formed, and from which the particular beam is radiated in a particular direction based on the first phase differences and the electric power of the first portion of electromagnetic waves and the second phase differences and the electric power of the second portion of electromagnetic waves.

With this structure of the antenna device, amplitudes or phases of transmission signals are adjusted in the adjusting unit. The beam forming unit has a lens or a passive element acting as a lens. In this unit, first electromagnetic waves are produced at the first input portion so as to have amplitude or phase corresponding to the first amplitude or the first phase of the first transmission signal, and are transmitted to the output portion to have the first phase differences. In the same manner, second electromagnetic waves are produced at the second input portion so as to have amplitude or phase corresponding to the second amplitude or the second phase of the second transmission signal, and are transmitted to the output portion to have the second phase differences. Then, the beam forming unit forms a particular beam from the first and second electromagnetic waves. This beam is composed of a first portion of electromagnetic waves having the first phase differences and electric power corresponding to electric power of the first electromagnetic waves and a second portion of electromagnetic waves having the second phase differences and electric power corresponding to electric power of the second electromagnetic waves. Then, the particular beam is radiated in a particular direction. This direction is determined on the basis of the first phase differences and the electric power of the first portion of electromagnetic waves and the second phase differences and the electric power of the second portion of electromagnetic waves.

Because the second input portion differs from the first input portion, the first phase differences are differentiated from the second phase differences. In this case, the first portion of electromagnetic waves in the beam has propagation directions centered on a first direction, and the second portion of electromagnetic waves in the beam has propagation directions centered on a second direction different from the first direction.

Further, amplitudes or phases of the first and second transmission signals are independently adjusted by the transmission signal adjusting unit. When amplitudes of the first and second transmission signals are adjusted, the amplitude ratio of the first portion of electromagnetic waves in the beam to the second portion of electromagnetic waves in the beam depends on this amplitude adjustment. Therefore, the particular direction of the particular beam can be adjustably set between the first and second directions. When phases of the first and second transmission signals are adjusted, the phase of electromagnetic waves composing the beam depends on this phase adjustment. Therefore, the particular direction of the particular beam can be adjustably set between the first and second directions or can be adjustably set outside the direction range between the first and second directions.

Accordingly, because the beam forming unit requires only two input portions, from which the transmission of electromagnetic waves is started, to form the particular beam radiated in the particular direction, the antenna device can radiate a beam in any direction freely set in a simple structure while using a lens or a passive element having the same function as the function of the lens.

According to another aspect of this exemplary embodiment, the object is achieved by the provision of an antenna device, comprising a beam receiving unit, a composite signal adjusting unit and a reception signal producing unit. The receiving unit has an antenna surface on which an incoming beam, composed of a first portion of electromagnetic waves having first phase differences and a second portion of electromagnetic waves having second phase differences different from the first phase differences, is received, an input portion from which first electromagnetic waves having the first phase differences and electric power corresponding to electric power of the first portion of electromagnetic waves in the beam and second electromagnetic waves having the second phase differences and electric power corresponding to electric power of the second portion of electromagnetic waves in the beam are transmitted, a first output portion at which the first electromagnetic waves transmitted from the input portion has a phase and a first composite signal is produced from the first electromagnetic waves to have a first amplitude and a first phase corresponding to an amplitude and phase of the first electromagnetic waves, and a second output portion at which the second electromagnetic waves transmitted from the input portion has a phase and a second composite signal is produced from the second electromagnetic waves to have a second amplitude and a second phase corresponding to an amplitude and phase of the second electromagnetic waves. The adjusting unit adjusts the amplitudes or phases of the first and second composite signals. The producing unit produces a reception signal providing information about an object, from which the incoming beam comes, from the first and second composite signals adjusted by the composite signal adjusting unit to detect the information of the object.

With this structure of the antenna device, the beam receiving unit is formed of a lens or a passive element acting as a lens. When an incoming beam is received on the antenna surface, first electromagnetic waves are produced at the input portion to have first phase differences and electric power corresponding to electric power of a first portion of electromagnetic waves having the first phase differences in the beam, and the first electromagnetic waves are transmitted to the first output portion to have the same phase. Further, second electromagnetic waves are produced at the input portion to have second phase differences and electric power corresponding to electric power of a second portion of electromagnetic waves having the second phase differences in the beam, and the second electromagnetic waves are transmitted to the second output portion to have the same phase.

Then, at the first output portion, a first composite signal is produced from the first electromagnetic waves to have a first amplitude and a first phase corresponding to an amplitude and the phase of the first electromagnetic waves. Further, at the second output portion, a second composite signal is produced from the second electromagnetic waves to have a second amplitude and a second phase corresponding to an amplitude and the phase of the second electromagnetic waves.

The amplitude and phase of the first composite signal correspond to those of the first portion of electromagnetic waves in the incoming beam, and the amplitude and phase of the second composite signal correspond to those of the second portion of electromagnetic waves in the incoming beam. Therefore, the amplitudes and phases of the composite signals indicate an incoming direction of the beam.

Then, the adjusting unit appropriately adjusts the amplitudes or phases of the composite signals, and the producing unit produces a reception signal having information about an object from the adjusted composite signals.

Because the adjusting unit appropriately adjusts the composite signals, the information of the object such as speed and distance of the object relative to the antenna device at a bearing angle to the object corresponding to the incoming direction of the beam can be obtained.

Accordingly, because the number of output portions is two in the antenna device, the antenna device can receive a beam coming from any direction in a simple structure while using a lens or a passive element having the same function as the function of the lens.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which like reference numerals indicate like parts, members or elements throughout the specification unless otherwise indicated.

First Embodiment

An antenna device disposed in a radar apparatus will be described.FIG. 1is a block diagram of a radar apparatus having an antenna device according to the first embodiment.

As shown inFIG. 1, a radar apparatus1has an antenna device60for forming and radiating a radar beam and receiving the radar beam from an object, which reflects the radiated beam toward the device60, and an object information detecting unit40.

The antenna device60has a transmitting block10for transmitting a radar beam of frequency-modulated continuous waves (FMCW) having directivity according to a transmission signal while changing the radiation direction of the beam in a predetermined cycle within a predetermined direction range, a receiving block20for receiving the radar beam reflected by the object and producing a reception signal, indicating information about the object, from the received beam, and a beam controller30for controlling the transmitting block10to adjustably set the radiation direction of the radar beam while changing the radiation direction in the predetermined cycle and controlling the receiving block20to appropriately produce the reception signal from the received beam.

The object information detecting unit40supplies an instruction to the block10as the transmission signal, supplies a beam instruction specifying the radiation direction of the radar beam to the controller30, and detects information regarding the object from the reception signal produced in the block20.

This radar apparatus1is, for example, disposed on the front portion of a vehicle. When the radar beam radiated in a particular direction is reflected by the object and is returned to the device60from the particular direction, the detecting unit40, for example, detects the speed of the vehicle relative to the object and the distance between the vehicle and object from the reception signal in addition to a particular bearing angle to the object corresponding to the particular direction.

The transmitting block10has a voltage control oscillator (VCO)11for generating a high frequency signal in response to an instruction of the detecting unit40, a first divider12for dividing electric power of the high frequency signal into first and second portions and producing a local signal from the second portion of electric power, a second divider13for equally dividing the first portion of electric power into two to produce a first transmission signal and a second transmission signal having the same amplitude and the same phase, a transmission signal adjusting unit14for receiving the transmission signals having the same amplitude and the same phase from the divider13and independently amplifying the transmission signals, and a beam forming unit80.

This forming unit80produces first high frequency waves (i.e., electromagnetic waves) having electric power and phase corresponding to electric power and phase of the first transmission signal amplified in the adjusting unit14at a first input portion, and transmits the first high frequency waves to an output portion to give first phase differences to the first high frequency waves. Further, the forming unit80produces second high frequency waves having electric power and phase corresponding to electric power and phase of the second transmission signal amplified in the adjusting unit14at a second input portion, and transmits the second high frequency waves to the output portion to give second phase differences to the second high frequency waves. The forming unit80forms a particular beam on an antenna surface and radiates this beam in a particular direction. This beam is composed of a first portion of electromagnetic waves having the first phase differences and electric power corresponding to electric power of the first electromagnetic waves and a second portion of electromagnetic waves having the second phase differences and electric power corresponding to electric power of the second electromagnetic waves. The particular direction of the beam is determined by the first phase differences and the electric power of the first portion of electromagnetic waves and the second phase differences and the electric power of the second portion of electromagnetic waves.

The high frequency signal of the VCO11is frequency-modulated so as to have the center frequency F0(e.g., 76 GHz).

FIG. 2is a view showing the structure of the divider13. As shown inFIG. 2, the divider13has a pair of transmission lines131and132such as micro strip lines and a resistive element133. Each of the transmission lines131and132has the length of λ/4. λ denotes the wavelength of the high frequency signal corresponding to the center frequency F0. One end of the transmission line131and one end of the transmission line132are connected with a common terminal. The other ends of the transmissions131and132are connected with respective ends of the resistive element133. Further, the other end of the transmission line131is connected with a first separated terminal, and the other end of the transmission line132is connected with a second separated terminal. Therefore, a so-called Wilkinson power divider is used as the divider13.

The first portion of electric power in the first divider12is received at the common terminal of the second divider13, and the transmission signals of the second divider13are transmitted to the adjusting unit14through the respective separated terminals.

The adjusting unit14has a first variable amplifier14aand a second variable amplifier14b. The variable amplifier14asets a first variable amplification factor (i.e., first variable gain) according to an instruction of the controller30, and amplifies the first transmission signal by the factor to produce the first transmission signal having a first amplitude. The amplifier14hsets a second variable amplification factor (i.e., second variable gain) according to an instruction of the controller30and amplifying the second transmission signal by the factor to produce the second transmission signal having a second amplitude. The ratio of the first amplification factor to the second amplification factor is changeably set.

Two transmission lines, respectively, connecting the separated terminals of the divider13and the amplifiers14aand14bhave the same length. Therefore, the amplifiers14aand14bcan receive the transmission signals having the same amplitude and phase.

The forming unit30has a Rotman lens15, having two transmission beam ports BP (BP1and BP2) and a plurality of antenna ports AP (e.g., four antenna ports AP1, AP2, AP3and AP4), and a transmission array antenna16having a plurality of antenna elements, (e.g., four antenna elements) connected with the respective antenna ports AP. The Rotman lens15is a passive element acting as a lens. The beam ports BP (i.e., input portions) are placed on one side of the lens15and are spaced from each other at a predetermined interval. The antenna ports AP (i.e., output portion) are placed on the other side of the lens15and are spaced from one another at predetermined intervals. Each beam port SP is spaced from the antenna ports AP through wave-guiding channels of the lens15at different intervals. The antenna elements of the array antenna16are aligned on an antenna surface AN1at equal intervals.

In response to the first transmission signal amplified in the amplifier14a, the Rotman lens15induces or produces high frequency waves, having the same amplitude and phase corresponding to the amplitude and phase of the first transmission signal, at the beam port BP1due to magnetic coupling between the beam port BP1and a feeding line of the amplifier14a, and distributes electric power of the high frequency waves to the antenna ports AP through the wave-guiding channels having different lengths. Therefore, the lens15forms high frequency waves having first phase differences at the respective antenna ports AP. In response to the high frequency waves of the antenna ports AP, the array antenna16produces radiation signals at the respective antenna elements due to magnetic coupling between each antenna port and the corresponding antenna element, and forms a first beam of electromagnetic waves from the radiation signals.

The waves of the first beam have the first phase differences on the antenna surface AN1of the antenna16and have electric power corresponding to electric power of the high frequency waves, but the waves have the same phase along the first direction inclined with respect to the antenna surface AN1. Therefore, the antenna16can radiate the first beam in the first direction (or first angle to the antenna surface AN1) in response to the first amplified transmission signal.

In the same manner, in response to the second transmission signal amplified in the amplifier14b, the Rotman lens15induces or produces high frequency waves, having the same amplitude and phase corresponding to the amplitude and phase of the second transmission signal, at the beam port BP2, and distributes electric power of the high frequency waves to the antenna ports AP to form high frequency waves having second phases differences at the respective antenna ports AP. In response to the high frequency waves of the antenna ports AP, the array antenna16forms a second beam of electromagnetic waves.

The waves of the second beam have the second phase differences on the antenna surface AN1of the antenna16and have electric power corresponding to electric power of the high frequency waves, but the waves have the same phase along the second direction inclined with respect to the antenna surface AN1. Therefore, the antenna16can radiate the second beam in the second direction (or second angle to the antenna surface AN1) in response to the second amplified transmission signal.

In case of the reception of the first and second transmission signals having the same phase in the Rotman lens15, the lens15combines the high frequency waves produced from the first transmission signal with the high frequency waves produced from the second transmission signal at each antenna port AP. In response to the high frequency waves combined in the antenna elements, the array antenna16forms a particular beam on the antenna surface AN1and radiates this beam from the antenna surface AN1in a particular direction (or particular angle to the antenna surface ANT). The particular beam has a first portion of electromagnetic waves and a second portion of electromagnetic waves. The first portion of waves has the first phase differences on the antenna surface AN1and electric power corresponding to electric power of the high frequency waves produced from the first transmission signal. The second portion of waves has the second phase differences on the antenna surface AN1and electric power corresponding to electric power of the high frequency waves produced from the second transmission signal.

FIG. 3is a view showing a radiation pattern of a beam obtained by combining the first and second portions of waves with each other. As shown inFIG. 3, each of the first portion of waves (i.e., first beam) and the second portion of waves (i.e., second beam) has a radiation pattern of electric power with respect to the radiation direction. The first portion of waves has the highest electric power in the first direction, and the second portion of waves has the highest electric power in the second direction. The particular beam obtained by combining the first and second portions of waves with each other has the highest electric power in the particular direction placed between the first and second directions. Therefore, the particular beam is radiated in the particular direction between the first and second directions. This particular direction depends on the power ratio of the first portion to the second portion.

The electric power of the first portion of waves depends on the electric power of the first amplified transmission signal, and the electric power of the second portion of waves depends on the electric power of the second amplified transmission signal. Therefore, the particular direction is defined by the first phase differences corresponding to the first direction, the second phase differences corresponding to the second direction, and the electric power ratio (or amplitude ratio) of the first amplified transmission signal to the second amplified transmission signal (i.e., ratio of the first amplification factor to the second amplification factor).

The receiving block20has a beam receiving unit81for receiving a beam, which is radiated from the block10and is reflected from an object, from the particular direction, and producing a first composite signal and a second composite signal from the received beam, a composite signal adjusting unit23for appropriately amplifying the composite signals, a power combiner (or reception signal producing unit)24for combining the composite signals amplified in the adjusting unit23to produce a reception signal indicating information about the object, and a mixer25for mixing the reception signal with the local signal of the first divider12of the transmitting block10to produce a beat signal.

The receiving unit81has a reception array antenna21and a Rotman lens22denoting a passive element acting as a lens. The array antenna21has a plurality of antenna elements (e.g., four antenna elements), respectively, receiving electromagnetic waves of the beam. These antenna elements are aligned on an antenna surface AN2at equal intervals. The Rotman lens22has two reception beam ports BP (BP3and BP4) and a plurality of antenna ports AP (e.g., four antenna ports AP5, AP6, AP7and AP8) connected with the antenna elements of the array antenna21. The beam ports BP3and BP4(i.e., output portions) are placed on one side of the lens22and are spaced from each other at a predetermined interval. The antenna ports AP5to AP8(i.e., input portion) are placed on the other side of the lens22and are spaced from one another at predetermined intervals. Each beam port BP is spaced from the antenna ports AP through wave-guiding channels of the lens22at different intervals.

The array antenna21receives a beam coming from the particular direction (or particular angle to the antenna surface AN2). This beam has a first portion of electromagnetic waves having first phase differences on the antenna surface AN2and a second portion of electromagnetic waves having second phase differences on the antenna surface AN2. The first phase differences correspond to the first direction. The second phase differences correspond to the second direction. In response to the first portion of waves contained in the beam, the Rotman lens22induces or produces first high frequency waves having the first phase differences and electric power corresponding to the first portion of waves at the antenna ports AP. Further, in response to the second portion of waves contained in the beam, the Rotman lens22induces or produces second high frequency waves having the second phase differences and electric power corresponding to the second portion of waves at the antenna ports AP. The Rotman lens22transmits the first high frequency waves of the antenna ports AP to the beam port BP3so as to produce the first high frequency waves having the same phase at the beam port BP3, and produces a first composite signal at the beam port BP3. Therefore, the first composite signal has the same phase as that of the first high frequency waves and has electric power of the first high frequency waves, so that electric power and phase of the first composite signal corresponds to electric power and phase of the first portion of waves. In the same manner, the Rotman lens22transmits the second high frequency waves of the antenna ports AP to the beam port BP4to produce the second high frequency waves having the same phase at the beam port BP4, and produces a second composite signal at the beam port BP4. Therefore, the second composite signal has the same phase as that of the second high frequency waves and has electric power of the second high frequency waves, so that electric power and phase of the second composite signal corresponds to electric power and phase of the second portion of waves.

The amplitude ratio of the first portion of waves to the second portion of waves corresponds to the particular direction of the received beam, so that the amplitude ratio of the first composite signal to the second composite signal indicates the particular direction of the received beam. Because the received beam is produced from the transmission signals having the same phase in the transmitting block10, the composite signals have the same phase.

The adjusting unit23has a first variable amplifier23aconnected with the beam port BP3and a second variable amplifier23bconnected with the beam port BP4. The amplifier23asets a third variable amplification factor (i.e., a third gain) according to a first reception control signal of the controller30and amplifies the first composite signal by the third variable amplification factor. The amplifier23bsets a fourth variable amplification factor (i.e., a fourth gain) according to a second reception control signal of the controller30and amplifies the second composite signal by the fourth variable amplification factor.

The combiner24has the same structure as that of the second divider13shown inFIG. 2. The combiner24receives the amplified composite signals at the respective separated terminals, produces a reception signal by combining the composite signals with each other at the common terminal and outputs the reception signal from the common terminal. Two transmission lines, respectively, connecting the separated terminals of the combiner24and the amplifiers23aand23bhave the same length. Therefore, the composite signals received in the amplifiers23aand23bhave the same phase.

The controller30has a temperature sensor31for detecting the ambient temperature of the radar apparatus1, a map storing unit32for storing a transmission adjusting map, a reception adjusting map, a transmission correcting map and a reception correcting map, and an adjustment setting unit33. The transmission adjusting map indicates the relationship between the direction of the beam radiated from the transmitting block10and a transmission adjustment denoting gains of the amplifiers14aand14b. The reception adjusting map indicates the relationship between the direction of the beam received in the receiving block20and a reception adjustment denoting gains of the amplifiers23aand23b. The transmission correcting map indicates the relationship between the ambient temperature and a correction of the transmission adjustment. The reception correcting map indicates the relationship between the ambient temperature and a correction of the reception adjustment. The adjustment setting unit33sets adjusting instructions indicating gains of the amplifiers14a,14b,23aand23baccording to the instruction of the unit40, the ambient temperature detected in the sensor31and the maps of the unit32, outputs the adjusting instructions to the respective amplifiers14aand14bof the block10and outputs the other adjusting instructions to the respective amplifiers23aand23bof the block20.

Therefore, the amplifiers14aand14bamplify the transmission signals according to the adjusting instructions, and the amplifiers23aand23bappropriately amplify the composite signals according to the adjusting instructions. For example, the controller30controls the amplifiers14aand14bsuch that the summed electric power of the amplified transmission signals becomes a constant value.

To radiate a particular beam in the particular direction, it is required that the amplitude ratio of the first transmission signal amplified in the amplifier14ato the second transmission signal amplified in the amplifier14bis set at a particular value. The transmission adjusting map is produced by experimentally determining the ratio required to radiate a beam in each of many directions. In the same manner, to appropriately amplify the composite signals in the amplifiers23aand23b, the reception adjusting map is produced by experimentally determining the amplitude ratio of the first composite signal amplified in the amplifier23ato the second composite signal amplified in the amplifier23b.

For example, the first and second variable amplification factors are set based on the transmission adjusting map in the amplifiers14aand14bsuch that the ratio of electric power outputted from the amplifier14ato electric power outputted from the amplifier14bis set at 1:0, 0.9:0.1, 0.81:0.19, 0.5:0.5 and 0:1 in that order every scanning period.

FIG. 4Ais a view showing the beam radiated in the first direction in case of the amplitude ratio 1:0,FIG. 4Bis a view showing the beam radiated in the second direction in case of the amplitude ratio 0:1, andFIG. 4Cis a view showing the beam radiated in the middle direction between the first and second directions in case of the amplitude ratio 0.5:0.5.

For example, as shown inFIG. 4A, when the amplitude ratio in the adjusting unit14is set at 1:0, the array antenna16radiates the beam in the first direction. As shown inFIG. 4B, when the amplitude ratio is set at 0:1, the array antenna16radiates the beam in the second direction. When the amplitude ratio differs from 1:0 and 0:1, the particular direction of the beam differs from the first and second directions. As shown inFIG. 4C, when the amplitude ratio is set at 0.5:0.5, the particular direction of the beam accords with the middle direction between the first and second directions.

Each of the Rotman lenses15and22has characteristics that change with temperature. For example, the distance between the beam ports BP1(or BP3) and BP2(or BP4) is changed with temperature. Therefore, the controller30corrects the adjustments of the adjusting maps on the basis of the ambient temperature to compensate differences between actual characteristics of the Rotman lens15and designed characteristics of the Rotman lens15and to compensate differences between actual characteristics of the Rotman lens22and designed characteristics of the Rotman lens22. In this embodiment, for example, a correction value or a correction factor is determined as the correction of the transmission adjustment from the ambient temperature detected in the sensor31, and the transmission adjustment determined based on the direction of the transmitting beam is corrected by adding the correction value to the adjustment or by multiplying the adjustment by the correction factor.

The object information detecting unit40is structured by a well-known microcomputer having a central processing unit (CPU) including a digital signal processor (DSP), a read only memory (ROM) for storing programs used for information detection, a random access memory (RAM) and an analog-to-digital (A/D) converter. The unit40supplies a beam instruction to the unit33of the controller30. This instruction specifies a beam radiation direction changing with time within a predetermined range. The unit40supplies a transmission instruction to the VCO11of the block10as the transmission signal. This instruction indicates a beam transmission period of time. The unit40detects beat frequencies of the beat signal outputted from the mixer25in the A/D converter every sampling period of time to obtain sampling data. These sampling data are stored in the RAM, and the DSP performs fast Fourier transform (FFT) on the sampling data.

The operation of the radar apparatus I will be described.

When the unit40sends a transmission instruction to the transmitting block11while sending a beam instruction to the unit33of the controller30, a frequency-modulated high frequency signal is intermittently generated in the VCO11every radiation period of time. As is well known, a triangular wave modulation is performed for a carrier wave of the frequency F0at a frequency modulation width ΔF by using a controlled voltage outputted from a direct current source (not shown) for modulation. Therefore, the modulated wave having the variable frequency in the range of F0±ΔF (i.e., variable wavelength in the range of λ±Δλ) is produced as the high frequency signal. A local signal is produced from this signal in the divider12and is outputted to the mixer25of the receiving block20. First and second transmission signals are produced from the high frequency signal in the divider13, and these transmission signals having the same amplitude and phase are received in the amplifiers14aand14bof the adjusting unit14.

In this case, even when a part of electric power of the first transmission signal is returned from the amplifier14ato the divider13, the resistive element133of the divider13substantially prevents the returned power from being transmitted to the amplifier14b. More specifically, as shown inFIG. 2, a first returned signal is transmitted from the amplifier14ato the amplifier14bthrough the transmission lines131and132, and a second returned signal is transmitted from the amplifier14ato the amplifier14bthrough the resistive element133. The phases of the returned signals are differentiated from each other by a half of the wavelength λ at the amplifier14b. Therefore, the returned signals are substantially cancelled out so as to supply no electric power of the signals to the amplifier14b. The power of the returned signals are consumed in the resistive element133. In the same manner, even when a part of electric power of the second transmission signal is returned from the amplifier14bto the divider13, the resistive element133of the divider13substantially prevents the returned power from being transmitted to the amplifier14a. Accordingly, the divider13with the element133can enhance the isolation between the amplifiers14aand14b, and the combiner24with the element133can enhance the isolation between the amplifiers23aand23b.

In the controller30, in response to the beam instruction, adjusting instructions are sent from the setting unit33to the respective amplifiers14aand14b, and the transmission signals are, respectively, amplified according to the adjusting instructions in the amplifiers14aand14b. In this amplification, the amplitude ratio of the first transmission signal amplified in the amplifier14ato the second transmission signal amplified in the amplifier14bis changed with time in a predetermined ratio range every scanning period of time much longer than the radiation period.

The amplified transmission signals having the same phase are received in the beam ports BP1and BP2of the Rotman lens15. In the Rotman lens15, first high frequency waves having first phase differences are produced from the first amplified transmission signal at the antenna ports AP, second high frequency waves having second phase differences are produced from the second amplified transmission signal at the antenna ports AP, and the first and second high frequency waves are combined with each other at each antenna port AP. In the array antenna16, a particular beam of electromagnetic waves is formed from the combined high frequency waves of the antenna ports AP.

This particular beam is composed of the first portion of electromagnetic waves, having first phase differences on the antenna surface AN1and having electric power corresponding to electric power of the first amplified transmission signal, and the second portion of electromagnetic waves, having second phase differences on the antenna surface AN1and having electric power corresponding to electric power of the second amplified transmission signal. In other words, the first portion of electromagnetic waves has propagation directions centered on the first direction corresponding to the first phase differences, and the second portion of waves has propagation directions centered on the second direction corresponding to the second phase differences. Therefore, the particular beam is radiated in the particular direction placed between the first and second radiation directions. Because the amplitude ratio in the adjusting unit14is changed with time, the radiation direction of the beam is also changed with time. Therefore, the radar apparatus1performs the beam scanning.

When the beam radiated in the particular direction from the array antenna16is reflected by an object and is returned to the antenna device60, the array antenna21receives electromagnetic waves of a beam coming from the particular direction at the respective antenna elements. In response to the reception of the beam in the antenna21, the Rotman lens22produces a first composite signal at the beam port23aand a second composite signal at the beam port23b.

The amplitude ratio of the first composite signal to the second composite signal depends on the coming direction of the received beam. For example, when the received beam comes from the first direction, the amplitude ratio becomes 1:0. When the receiving beam comes from the second direction, the amplitude ratio becomes 0:1. When the amplitude ratio differs from 1:0 and 0:1, the coming direction of the receiving beam differs from the first and second directions.

Further, in response to the beam instruction of the detecting unit40, adjusting instructions indicating amplification factors are sent from the setting unit33to the respective amplifiers23aand23b, and the composite signals are, respectively, amplified in the amplifiers23aand23baccording to the adjusting instructions. Because the direction of the beam radiated from the block10is specified by the detecting unit40, the amplification ratio in the composite signals are known by the unit40, and the composite signals are, for example, amplified under control of the unit40to have the same amplitude or to have electric power higher than a threshold value. In this case, information of the object can be adequately detected in the unit40.

Then, the composite signals are combined in the combiner24to produce a reception signal having information of the object, and the reception signal is mixed with the local signal of the divider12in the mixer25to produce a beat signal. The detecting unit40detects the speed of the apparatus1relative to the object and the distance between the apparatus1and the object from the beat signal in addition to the particular bearing angle to the object corresponding to the particular direction.

As described above, because the amplitude ratio in the transmission signals are changeably set in the amplifiers14aand14bunder control of the controller30, the direction of the beam radiated from the transmitting block10can be changeably adjusted in the Rotman lens15. Further, because amplitudes of the composite signals formed from the received beam are appropriately set in the amplifiers23aand23bunder control of the controller30, the receiving block20can adjust the reception signal such that the unit40appropriately detects information about the object from the reception signal.

Therefore, when the beam radiated from the array antenna16in the particular direction specified by the unit40is reflected by the object, the detecting unit40can obtain the bearing angle to the object corresponding to the particular direction, the speed of the apparatus1relative to the object and the distance between the apparatus1and the object.

Accordingly, because the antenna device60has the Rotman lens15having only two beam ports BP1and BP2and two amplifiers14aand14bconnected with the beam ports in the transmitting block10, the antenna device60using a passive element having the same function as the function of a lens can be manufactured in a simple structure without using any high frequency switch, and the antenna device60can be freely set to form a beam radiated in any direction between the first and second directions.

Further, the antenna device60has the Rotman lens22having only two beam ports BP3and BP4and two amplifiers23aand23bconnected with the beam ports in the receiving block20. Accordingly, the antenna device60using a passive element having the same function as the function of a lens can be manufactured in a simple structure to appropriately receive a beam coming from any direction between the first and second directions and to appropriately detect information about the object in the unit40from the received beam.

Moreover, the amplification in each of the amplifiers14a,14b,23aand23bis adjusted according to the ambient temperature of the radar apparatus1. Accordingly, the antenna device60can set the radiation direction of the transmitting beam with high precision, and the antenna device60can detect the incoming direction of the received beam with high precision so as to heighten the precision in the detection of the bearing angle to the object.

In this embodiment, when the radar apparatus1is, for example, mounted on a vehicle, the radar apparatus1may change the radiation direction of the transmitting beam in any of the horizontal and vertical planes. To change the radiation direction of the beam in the horizontal plane, the antenna elements of the array antenna16are aligned along the horizontal direction, and the antenna elements of the array antenna21are also aligned along the horizontal direction. In contrast, when the radar apparatus1vertically changes the radiation direction of the beam, the antenna elements of the array antenna16are aligned along the vertical direction, and the antenna elements of the array antenna21are also aligned along the vertical direction.

When the radar apparatus1is fixed to the vehicle so as to align the antenna elements of the array antenna16along the vertical direction, the antenna surface of the antenna16is sometimes inclined with respect to the vertical plane. In this case, the radiation angle of the beam to the antenna surface undesirably differs from the radiation angle of the beam to the vertical plane. To avoid this problem, in the same manner as the adjusting work for the optical axis of the headlamp of the vehicle, the apparatus1is fixed to the vehicle by using three bolts, and the fastening force of the bolts is normally adjusted manually by hand to precisely place the antenna surface in the vertical plane. This adjusting work is troublesome. However, in this embodiment, because gains in the amplifiers can be arbitrarily adjusted, the radiation direction of the beam to the antenna surface can be easily changed without manually adjusting the bolts by hand. As a result, the radar apparatus1can appropriately change the radiation direction of the beam to improve the performance of the apparatus1.

In this embodiment, each of the Rotman lenses15and22has two beam ports BP. However, each Rotman lens may have three beam ports or more. In this case, the beam ports are connected with respective amplifiers of the adjusting unit14or23.

Further, a Wilkinson power divider or combiner shown inFIG. 2is used as each of the divider13and the combiner24. However, a Rat-Race power divider or combiner shown inFIG. 5may be used as each of the divider13and the combiner24. As shown inFIG. 5, the Rat-Race power divider or combiner has four transmission lines231,232,233and234and a resistive element235. The transmission line231is placed between the common terminal and the first separated terminal, and the transmission line232is placed between the common terminal and the second separated terminal. The transmission line233is placed between the second separated terminal and one end of the element235, and the transmission line234is placed between the first separated terminal and the end of the element235. The other end of the element235is earthed. The transmission lines231to233have the same length of λ/4, and the transmission line234has the length of 3λ/4. Therefore, the first and second transmission signals transmitted to the adjusting unit14have the same amplitude and phase. Further, the length of the first route between the separated terminals through the transmission lines231and232differs from the length of the second route through the transmission lines233and234by a half of the wavelength λ. Therefore, even when a part of electric power of the first transmission signal is returned from the amplifier14a(or14b) to the divider13, the resistive element235of the divider13substantially prevents the returned power from being transmitted to the amplifier14b(or14a).

Moreover, the transmission signals received in the amplifiers14aand14bhave the same amplitude and the same phase. However, the transmission signals received in the amplifiers14aand14bmay have different amplitudes or different phases. In this case, it is required to perform the calibration in the unit14for the purpose of compensating different amplitudes or different phases of the signals.

Furthermore, the amplification factors in the unit14are set such that the summed electric power of the amplified transmission signals becomes a constant value. Accordingly, the transmission power of the radar beam becomes constant, and the radar beam can be radiated according to relevant laws and regulations.

Still further, each of the adjusting units14and23has variable amplifiers. However, the adjusting unit14or23may have phase shifters in place of the amplifiers or may have phase shifters in addition to the amplifiers.

FIG. 6is a block diagram of a radar apparatus having an antenna device according to a first modification of the first embodiment. As shown inFIG. 6, the radar apparatus2differs from the radar apparatus1shown inFIG. 1in that the adjusting unit14has two phase shifters14cand14din place of the amplifiers while the adjusting unit23has two phase shifters23cand23din place of the amplifiers.

With this structure, the phase shifters14cand14dof the transmitting block10shift phases of the transmission signals to set the phase difference between the signals. Therefore, the array antenna16radiates a beam in a particular direction different from the first and second directions. This particular direction is placed outside the directional range between the first and second directions by appropriately setting the phase difference between the signals.

Further, when the array antenna21of the receiving block20receives a beam radiated from the block10and reflected by an object, composite signals received in the phase shifters23cand23dhave different phases corresponding to those set in the adjusting unit14. Because the phases of the composite signals are known by the controller30, the phases of the composite signals are shifted in the phase shifters23cand23dso as to have the same phase. Therefore, the reception signal produced in the combiner24appropriately has information about the object. In this case, the detecting unit40can appropriately detect this information.

Accordingly, because the adjusting units14and23adjust phases of the received signals, the antenna device60can radiate a beam in a particular direction between the first and second directions and can radiate a beam in a particular direction placed outside the directional range between the first and second directions.

Further, the antenna device60can appropriately produce the reception signal indicating information about the object by receiving a beam radiated from the apparatus60and reflected by the object.

Second Embodiment

FIG. 7is a block diagram of a radar apparatus having an antenna device according to the second embodiment. As shown inFIG. 7, a radar apparatus3differs from the radar apparatus1according to the first embodiment in that an antenna device61of the radar apparatus3has a beam forming unit82of a transmitting block110in place of the unit80and has a beam receiving unit83of a receiving block120in place of the unit81.

The forming unit82has a transmission array antenna17and a dielectric convex lens18. The antenna17has two antenna elements connected with the respective amplifiers14aand14b. The lens18has a first input surface (i.e., first input portion)1a, a second input surface (i.e., second input portion) lab and an antenna surface AN3acting as an output portion of the unit82. The antenna elements of the antenna17are disposed to be symmetric to each other with respect to the optical axis (i.e., center axis) of the lens18. These antenna elements face the respective input surfaces of the lens18along the optical axis.

The forming unit83of the receiving block120has a dielectric convex lens26and a transmission array antenna27having two antenna elements connected with the respective amplifiers23aand23b. The lens26has an antenna surface AN4acting as an input portion, a first output surface (i.e., first output portion)26aand a second output surface (i.e., second output portion)26b. The antenna elements of the antenna27are disposed to be symmetric to each other with respect to the optical axis (i.e., center axis) of the lens22. The antenna elements of the antenna27, respectively, face the output surfaces of the lens26along the optical axis.

The map storing unit32of the controller30has the maps corresponding to the lenses18and26, the positional relationship between the lens18and the antenna17, and the positional relationship between the lens26and the antenna27.

In response to the first transmission signal amplified in the amplifier14a, one antenna element of the antenna17produces electromagnetic waves of a first beam having the amplitude and phase corresponding to the amplitude and phase of the signal and radiates the beam. This beam is transmitted to the first input surface of the lens18. Then, this beam is refracted and phase shifted by the lens18. That is, the waves of the beam have first phase differences on the antenna surface AN3of the lens18. Therefore, the first beam is radiated in the first direction corresponding to the first phase differences. This first direction is deflected from the optical axis of the lens18.

In the same manner, in response to the second transmission signal amplified in the amplifier14b, the other antenna element of the antenna17produces electromagnetic waves of a second beam having the amplitude and phase corresponding to the amplitude and phase of the second transmission signal and radiates the beam. This beam is transmitted to the second input surface of the lens18. Then, this beam is refracted and phase-shifted by the lens18. That is, the waves of the beam have second phase differences on the antenna surface AN3of the lens18. Therefore, the second beam is radiated in the second direction corresponding to the second phase differences. This second direction is inclined with respect to the optical axis of the lens18.

When the first and second transmission signals are amplified in the amplifiers14aand14bat a changeable amplifier ratio, the electromagnetic waves of the first beam and the electromagnetic waves of the second beam are combined with each other on the antenna surface AN3of the lens18to form a particular beam. This particular beam has propagation directions centered on the particular direction placed between the first and second directions. Therefore, the transmitting block110radiates the particular beam in the particular direction while changing the direction of the beam.

When a beam of electromagnetic waves coming from the first direction is received in the lens26, these waves have first different phases on an antenna surface AN4of the lens26. This beam is refracted by the lens26while phases of waves are shifted, and the waves have the same phase on the first output surface of the lens26. In other words, the reception strength of the waves is maximized on the first output surface. Then, the beam is outputted from the lens26. The antenna element of the antenna27connected with the amplifier23areceives this beam and produces a first reception signal from the beam. Therefore, information about the object can be detected from the reception signal at the bearing angle to the object corresponding to the first direction.

In the same manner, when a beam of electromagnetic waves coming from the second direction is received in the lens26, these waves have second different phases on the antenna surface AN4of the lens26. This beam is refracted by the lens26while phases of waves are shifted, and the waves have the same phase on the second output surface of the lens26. Then, the beam is outputted from the lens26. The antenna element of the antenna27connected with the amplifier23breceives this beam and produces a second reception signal from the beam. Therefore, information about the object can be detected from the reception signal at the bearing angle to the object corresponding to the second direction.

When a beam of electromagnetic waves having propagation directions centered on the particular direction between the first and second directions is received in the lens26, a first portion of these waves forming a first beam have first different phases on the antenna surface AN4of the lens26, and a second portion of these waves forming a second beam have second different phases on the antenna surface AN4of the lens26. The first beam is refracted by the lens26, and the waves of this beam have the same phase on the first output surface of the lens26and are received in the antenna element of the antenna27connected with the amplifier23a. Then, a first reception signal is produced from the waves having the same phase and is amplified in the amplifier23a. The second beam is refracted by the lens26, and the waves of the second beam have the same phase on the second output surface of the lens26and are received in the antenna element of the antenna27connected with the amplifier23b. Then, a second reception signal is produced from the waves of the second beam having the same phase and is amplified in the amplifier23b. Therefore, information regarding the object can be obtained from the reception signals at the bearing angle to the object corresponding to the particular direction.

Accordingly, because the forming unit82of the block110has only two antenna elements to radiate a beam in the particular direction, the antenna device61using the dielectric lens18can radiate a beam in any direction between the first and second directions in a simple structure.

Further, because the receiving unit83of the block120has only two antenna elements to receive a beam coming from the particular direction, the antenna device61using the dielectric lens26can appropriately receive a beam coming from any direction between the first and second directions in a simple structure to obtain information about the object from the received beam.

Moreover, in the same manner as in the first embodiment, the antenna device61can control the radiation direction of the beam with high precision and can detect the bearing angle to the object with high precision.

In this embodiment, each of the array antennas17and27has two antenna elements. However, each array antenna may have three antenna elements or more. In this case, the antenna elements are connected with respective amplifiers of the adjusting unit14or23.

Further, as shown inFIG. 8, the antenna device may have the phase shifters14cand14dand the phase shifters23cand23dshown inFIG. 6in place of the amplifiers14a,14b,23aand23b. In this case, in the same manner as in the antenna device shown inFIG. 6, the antenna device can radiate a beam in any direction different from the first and second directions with high precision and can receive a beam coming from any direction different from the first and second directions with high precision.

Third Embodiment

FIG. 9is a block diagram of a radar apparatus having an antenna device according to the third embodiment. As shown inFIG. 9, a radar apparatus5differs from the radar apparatus1according to the first embodiment in that an antenna device62of the radar apparatus5has a transmitting and receiving block50in place of the blocks10and20. The block50has the VCO11, the dividers12and13, the adjusting unit14, a beam forming and receiving unit84, the adjusting unit23, the combiner24and the mixer25.

The unit84has a Rotman lens52and an array antenna51. The lens52has two transmission beam ports BP (BP1and BP2), a plurality of antenna ports AP (e.g., four antenna ports AP1, AP2, AP3and AP4) and two reception beam ports BP (BP3and BP4). The lens52is a passive element acting as a lens. The beam ports BP1and BP2(i.e., input portions) are placed on the first side of the lens52and are spaced from each other at a predetermined interval. The beam ports BP1and BP2are connected with the respective amplifiers14aand14bof the unit14. The beam ports BP3and BP4(i.e., reception portions) are placed on the first side of the lens52and are spaced from each other at another predetermined interval. The beam ports BP3and BP4are connected with the respective amplifiers23aand23bof the unit23. The antenna ports AP (i.e., output portion) are placed on the second side of the lens52and are spaced from one another at predetermined intervals. Each beam port BP is spaced from the antenna ports AP through wave-guiding channels of the lens52at different intervals. The array antenna51has a plurality of antenna elements, (e.g., four antenna elements) connected with the respective antenna ports AP. The antenna elements are aligned on an antenna surface AN5at equal intervals.

The map storing unit32of the controller30has the maps corresponding to the Rotman lens52.

With this structure of the antenna device62, in the same manner as in the first embodiment, the unit84radiates a particular beam of electromagnetic waves produced from the transmission signals in the particular direction.

When an object reflects the particular beam to the antenna device62as an incoming beam, the antenna51receives this incoming beam coming from the particular direction. This beam is composed of electromagnetic waves of a third beam having propagation directions centered on a third direction and electromagnetic waves of a fourth beam having propagation directions centered on a fourth direction different from the third direction.

In response to this reception, the lens52produces third high frequency waves having third phase differences and fourth high frequency waves having fourth phase differences at the output ports AP, transmits the third high frequency waves to the beam port BP3so as to give the same phase to the third high frequency waves at the beam port BP3, and transmits the fourth high frequency waves to the beam port BP4so as to give the same phase to the fourth high frequency waves at the beam port BP4. The lens52produces a first composite signal from the third high frequency waves having the same phase at the beam port BP3, and produces a second composite signal from the fourth high frequency waves having the same phase at the beam port BP4.

Accordingly, the same effects as those in the first embodiment can be obtained. Further, because only one Rotman lens52is used for the antenna device62, the structure of the antenna device62can be further simplified.

In this embodiment, the antenna device may be structured according to the conception of the second embodiment. That is, in place of the unit84, the antenna device may have a dielectric convex lens, the array antenna17(seeFIG. 7) disposed to face the first side of the lens, and the array antenna27(seeFIG. 7) disposed to face the first side of the lens.

In the first to third embodiments, the beam is received through the Rotman lens or the dielectric lens to detect information about the object with high precision. However, the beam may be received without using the Rotman lens or the dielectric lens.

FIG. 10is a block diagram of a radar apparatus having an antenna device according to a modification of the first embodiment. As shown inFIG. 10, a radar apparatus7differs from the radar apparatus1shown inFIG. 1in that an antenna device63of the apparatus7has a receiving block70in place of the block20. The block70has the array antenna21and a plurality of mixers25connected with the respective antenna elements of the antenna21. The storing unit32of the controller30has the maps corresponding to the transmitting block10, and the setting unit33outputs instructions to the adjusting unit14.

With this structure of the apparatus7, a beam of electromagnetic waves coming from the particular direction is received in the antenna elements of the antenna21. The beam received in the antenna elements has particular phase differences. The phase of the waves received in each antenna element differs from those received in the antenna elements.

In response to this beam reception, the antenna21produces an object signal in each antenna element. Each mixer25produces a beat signal from the signal of the corresponding antenna element and a local signal of the divider12. The detecting unit40receives the beat signals of the mixers25and detects information about the object while using signal processing such as digital beamforming (DBF).

Accordingly, the receiving block of the antenna apparatus can be further simplified.

In the first to third embodiments, the beam is formed in the unit having a Rotman lens or dielectric lens to be radiated in the particular direction. However, the transmitting beam may be formed without using the Rotman lens or dielectric lens.

FIG. 11is a block diagram of a radar apparatus having an antenna device according to a modification of the first embodiment. As shown inFIG. 11, a radar apparatus9differs from the radar apparatus1shown inFIG. 1in that an antenna device64of the apparatus9has a transmitting block90in place of the block10. The block90has the VCO11, the divider12and the antenna16having a single antenna element. The storing unit32of the controller30has the maps corresponding to the receiving block2C, and the setting unit33outputs instructions to the adjusting unit23.

With this structure of the antenna device64, the array antenna16forms a beam of electromagnetic waves from electric power of the transmission signal outputted from the divider12and radiates the beam in a fixed direction. Electric power of this beam is composed of electric power of a first beam directed in the first direction and electric power of a second beam directed in the second direction.

When the receiving block20receives a beam coming from the fixed direction, the detecting unit40detects information about the object at the fixed bearing angle to the object corresponding to the fixed direction.

Accordingly, the antenna device64can radiate a beam in the fixed direction placed between the first and second directions and can produce a reception signal from the beam to detect information about the object.

Further, the transmitting block of the antenna apparatus can be further simplified.

In the antenna devices63and64, the amplifiers14aand14bor the amplifiers23aand23bare used. However, the phase shifters14cand14dor the amplifiers23cand23dshown inFIG. 6may be used in place of the amplifiers. In this case, the antenna device can radiate a beam in a direction different from the first and second directions or can receive a beam coming from a direction different from the first and second directions.

These embodiments should not be construed as limiting the present invention to structures of those embodiments, and the structure of this invention may be combined with that based on the prior art.