JPH0219646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a microwave radar detection device, and particularly to the structure of a horn antenna and mixer used therein.

Prior Art and its Problems Prior art includes US Pat. No. 3,339,275 issued September 5, 1967 by ANDERSON et al. This patent teaches a method of manufacturing a horn antenna in which two identical halves are molded and secured together by flanges. This patent also teaches attaching the center conductor and cone to the throat of the assembled horn. However, it should also be noted that the horn is used over a frequency range of 50-500 MHz, has an overall length of 18 feet, and has an aperture diameter of 12 feet.

U.S. Pat. No. 3,530,482 to PALMER, issued September 22, 1970, teaches a partition horn with variable flare sidewalls. This includes means for varying the physical dimensions and therefore the energy sensitivity of the throat of the horn.

US Pat. No. 4,058,813 issued Nov. 15, 1977 to Lisko teaches a waveguide horn antenna that can be constructed from metal sheets and can have several different embodiments. In any event, the horn antenna shown in this patent still requires a tuning screw in the throat of the horn, and the precise physical dimensions of the horn, and therefore its energy frequency sensitivity, are dependent on the manufacturing method used. It is not something that can be predicted due to the process.

Incidentally, horn antennas for receiving and transmitting microwave energy are well known, and such horns can be formed from conductive materials or by coating or plating non-conductive materials with conductive materials. It is also well known that Additionally, for any frequency, a horn antenna specifically designed as a receiving horn will have a low energy density but distinguishable electromagnetic field at one or more specific frequencies in the throat area of the horn. It is necessary to determine the dimensions and add flares to achieve this. The detector is often inserted into the throat of the horn, via at least one mixer diode, to receive the energy present through these fields at one or more frequencies for which the horn is designed.

Receiving horns specifically used and operated at microwave frequencies such as X-band or K-band frequencies (which are used in police speed detection radars and intruder detection radars for building and community security applications) In this case, a highly sensitive horn is often required. This is especially the case when the radar or microwave frequency energy source to be detected is at a significant distance from the detector.
And in this case, the physical placement of the mixer diode relative to the throat of the horn is important. Generally, plane aberrations can be corrected by a lens placed in front of the horn, but the horn's field collector, or ridge,
There is a requirement that reliable coupling at the correct frequency must exist between the detector circuit and the detection circuit, such as a mixing diode. This typically requires at least a tuning post located inside the throat to ensure that the horn and its coupling operate at the correct frequency or frequencies, and is due, at least in part, to the physical placement of the mixer diode within the throat of the horn. Therefore, these problems are further compounded by the additional problems of frequency stability and sensitivity to temperature due to the physical mounting and placement of the detection circuitry relative to the horn throat and field collector. This will lead to problems.

(Summary of Constituent Characteristics of the Invention) The present invention provides a method for attaching a horn ridge to a feed strip for a diode or a pair of diodes mounted in association with a microstrip plate.
These problems are overcome by creating a secure and physically dimensioned bond. The present invention also provides a horn antenna structure that can be easily installed through the use of standard assembly line techniques without the need to adjust or balance energy focusing or sensing at the throat of the horn. .

In particular, the present invention overcomes the problems described above and in the following by providing a horn antenna structure having the following structure. That is, therein, a substantially rigid, flat mounting plate having an upper surface and a lower surface has a microstrip plate attached to its upper surface, and the microstrip plate is associated therewith. one or more diodes and a feedstrip for the diodes mounted on or near the first exposed edge of the top surface of the microstrip plate; will be placed in A one-piece molded horn element is provided having an open bottom surface, an upwardly flared top wall, and a pair of side walls, and further including a downwardly extending ridge formed on the underside of the top wall. There is. The ridge extends rearwardly of the throat of the horn and extends downwardly in at least the throat region to such an extent that the bottom edge of the ridge in the throat region extends when the molded horn element is secured to the upper side of the mounting plate. It is so close that it makes physical and electrical contact with the feed slip. Furthermore, the top surface of the mounting plate becomes the bottom wall of the horn.

Further, according to the present invention, a high frequency input section of a horn, a local oscillation frequency input section from a local oscillator,
and intermediate frequency IF output, provision is made for very good isolation of the mixer mounted on the microstrip plate. This arrangement is accomplished by providing a pair of mixer diodes connected in antiparallel and a quarter-wavelength stub for the horn's operating frequency on the side of the mixer diode remote from the feed strip. , this is to provide a virtual short circuit on the side far from the mixer diode with respect to the operating frequency. That is, the throat of the horn is considered a capacitive impedance,
This is accomplished by configuring the horn throat to be sized to thereby prevent outward radiation of energy at the local oscillator LO frequency, but to permit a return path of the LO signal to ground. Furthermore, the IF is equipped with a low-pass filter below the LO frequency.
This is done by allowing only the frequency signal to be output from the IF section of the mixer.

(Preferred Embodiment) As mentioned above, the present invention provides
− Bands (i.e. 10.525GHz and 10.525GHz respectively)
The present invention provides a horn antenna structure particularly suitable for microwave detection circuits such as radar detectors operating at 24.150 GHz). It has three main structural members. That is, in Fig. 2, there are 12
A nearly rigid flat mounting plate, also shown in the second
Shown are a microstrip plate 14 on the top surface of the mounting plate 12, and a one-piece molded horn element 16 shown in FIG. The overall assembly structure, viewed from above, is indicated at 10 in FIG.

The details of both the mounting plate and the microstrip plate are not particularly relevant to the present invention, so
It is shown by way of example only. For example, on the mounting plate 12 may be mounted an adjustable inductor 18, a microchip 20, a connecting post terminal 22, and various capacitors, resistors, coils, etc., shown generally at 24, 26, 28. .

Similarly, the details of the microstrip plate 14 are also not particularly relevant, except as follows. That is, it uses printed circuit/microstrip technology, on which circuit components include certain capacitive components for the local oscillator and low-pass filter, and generates signals at LO and IF frequencies below the horn frequency. Other processing circuits are printed or installed. However, on the microstrip board there are one or more mixer diodes attached to the board at point 30 and a conductive feed strip formed as part of the conductive circuitry on the board. A tap 32 is provided. Feedstrip 32 is located on the upper exposed surface of the microstrip plate at or at least near an end 34 thereof. Certain features of mounting mixer diodes in accordance with a preferred embodiment of the present invention are described below in connection with FIG.

Note that the mounting plate 12 is provided with a number of holes, indicated at 36, which are generally symmetrical with the exception of 36a, which secure the horn element 16 to the mounting plate 12. Note in FIG. 1 that the underside of the one-piece molded horn element 16 is provided with a number of studs 38 or 38a. It is clear that the one-piece molded horn element 16 is secured to the mounting plate 12 by screws extending from the underside of the mounting plate 12 through the holes 36 and into the tapped grooves 40 of the studs 38.

Looking at the one-piece mold horn element 16,
Its horn portion 41 has an upwardly flared top wall 42 and side walls 44. It can also be seen that there is an open bottom defined simply by the bottom edges of sidewalls 44. There is a ridge 46 inside the horn section 41, and its exact shape does not matter much;
is sized and formed to provide a field collector (i.e., a means for concentrating the electric field) at at least the X-band and K-band frequencies in the throat region 47 of.

As is clear from FIG.
by inserting and securing the stud 38 into the tapped groove 40 of the stud 38, and when the one-piece molded horn 16 is lowered onto the mounting plate 12, the vertical positioning of the ridge 46 (and its height in the throat region 47) is fixed. ), it is the feed strip 3 on the top surface of the microstrip plate 14.
2. The device is adapted to form physical electrical contact with 2. Furthermore, the top surface of the mounting plate 12 generally forms the bottom wall of the horn 41 in the area indicated at 50, so that the horn is defined by its bottom wall, side walls 44 and top wall 42. A pair of wings 39 formed on either side of the mouth of the horn and extending outwardly from the side wall 44 may be provided for the convenience of attaching other circuit elements.

To complete the horn structure, the ground plate is, of course, produced by coating the mounting plate 12 with a conductive material, at least in the area of the upper surface thereof. moreover,
When molded horn element 16 is secured to the top surface of mounting plate 12 by fasteners, such as screws 48, a connection is formed between the bottom surface of sidewall 44 and the conductive top surface of mounting plate 12. And since at least the interior surface of the one-piece molded horn element is electrically conductive, effective grounding at intermediate frequencies is achieved through physical electrical contact between the ridge 46 of the throat region 47 and the feed strip for the mixer diode. This will ensure that the mixer diode is

The construction of the one-piece molded horn element 16 is most conveniently pressure cast from zinc or other suitable metal, but may also be formed from non-conductive materials such as injection molded thermoplastics (which may be coated with a conductive material at least on its internal surfaces). Other techniques such as laid-up epoxy and fiberglass construction can be used, especially at low frequencies, but dimensional stability may be improved if the horn element is injection molded or pressure cast in metal. This is more reliably guaranteed if the

Of course, the lower surface of mounting plate 12 carries a printed circuit formed in a conventional manner and using conventional printed circuit techniques. Circuit components 24 and 2 are mounted on the top surface of the mounting plate 12.
6, 28 are connected to the circuit wires below them through their mounting plates. Similarly, the components on microstrip plate 14 are insulated from the ground plane on the top surface of mounting plate 12 by the microstrip plate's insulating material. Therefore, a local oscillator operating at microwave frequencies or intermediate frequencies thereof is supported on a mounting plate or microstrip plate and shielded.

In particular, the integrally molded horn 16 includes its 52, 5
Note that two regions or cavities are formed at point 4, each of which is defined by the provision of a vertically extending wall 56 and an upper wall or cover 58. If the ground plate (conductive coating) on the top surface of the mounting plate 12 is below the bottom edge of the vertically extending wall 56, then the cavity 52
Alternatively, a local oscillator (a first oscillator mounted on the microstrip plate 14 in the cavity 52 and a second oscillator mounted on the mounting plate 12 in the cavity 54) is attached to the mounting plate 54. , these are shielded.

The horn 41 (here defined by a flat bottom surface 50, a pair of side walls 44 and an upwardly extending flared top wall 42) has such a defined shape that the horn For microwave energy that is received and focused, there may be some elevation distortion.
However, most of this elevation distortion is caused by the horn 41
can be removed by placing a lens (indicated by the dashed line at 60 in FIG. 4) in front of the lens.

Several very significant advantages are obtained from the horn antenna structure according to the invention. In particular, the feed strip 3 of the ridge 46 in the throat region 47
2. Physical electrical contact remains virtually constant even when the horn antenna structure is subjected to temperature changes (e.g. from summer to winter) and even when moved from room temperature conditions to extremely hot or cold conditions. Has high temperature stability. Furthermore, by suitably sizing throat region 47 and broadband horn 41, all necessary tuning can be achieved by properly sizing throat region 47 and broadband horn 41.
is realized by the printed parts of the microstrip plate 14 without physical alignment. The mixer diode is physically fixedly attached to the microstrip plate 14. And when the feedstrip 32 is on the microstrip plate 14, there is a positive coupling between the ridge 46 and the low energy microwave frequency field present above the ridge.

For secure physical attachment of the mixer diode, and thus for physical contact and electrical conductivity from the horn to the mixer feed strip 32, a plated through hole from the bottom of the mounting plate 12 is provided for the mixer diode. It is not necessary to provide a ground. That is, the horn provides an effective ground return at intermediate frequencies and also provides a return path for the local oscillator signal.

Compression mechanical coupling of the ridge 46 to the mixer feed strip 32 is most conveniently accomplished by threading a plurality of screws 48 through the hole 36 and into the tapped groove 40 of the stud 38. However, other means may be used, such as fasteners passed downwards towards nuts attached to the bottom of the mounting plate 12 or compression fasteners surrounding the periphery of the horn element 16.

In particular, it should be noted that if the one-piece horn element 16 is pressure cast from zinc, the die in which it is cast is very easily formed. This is because the horn, ridge 46, sidewall 44, cavity sidewall 56, stud 38, and other castings are formed on the underside or "tension" side of the casting.
Therefore, one-time tension pressure casting is possible and the cast zinc microwave horn can be equipped very economically. The present invention is also more economical in that it eliminates the need for tuning posts or other physical and physically movable structures in the throat region.

The horn antenna structure according to the present invention also includes a single tension pressure casting (i.e., a side movable part,
It has no folds or other requirements, can be injection molded very easily, and has temperature stability and effective shielding of the first and second local oscillators, making the entire assembly easy to use. Can be provided very economically.

Finally, by looking at FIG. 6, another advantage of the horn structure of the present invention can be realized.
That is, due to the physical attachment of the horn throat 47 and its ridge 46 to the feedstrip 32, the mixer diode can be physically and fixedly attached to the microstrip plate. This provides microstrip printed circuitry that can be moved at microwave frequencies, thereby achieving highly effective port isolation of the three-port mixer.

The horn 41 has approximately X-band frequencies and K-band frequencies (10.525 GHz, respectively).
24.24.150GHz), the mixer could be arranged as shown in Figure 6 (this is for illustrative purposes only; (not intended to be shown). In any event, the mixer is indicated generally at 62 and includes three ports.
Of these three ports, the high frequency port is primarily defined by feed strip 32, the local oscillator LO port is defined by circuit strip 64, and the intermediate frequency output port is defined by circuit strip 66. . All of these components and other components shown in FIG. 6, except for the horn and diode, can be printed directly onto the microstrip board.

As previously mentioned, the horn with the sidewall 44 is
The ridge 46 covers at least a portion of the feed strip 32;
attached to make physical and electrical contact therewith. Also provided is a circuit strip 68, and the connection point 30 is the point at which a quarter-wave stub 70 for the X-band and a quarter-wave stub 72 for the K-band contact the circuit strip 68. is defined as . A pair of mixer diodes 74 (which are mounted on the mounting layer in an anti-parallel connection) are connected to the feed strip 32.
is connected to the connection point 30 from the end of the . A pair of elements 76, 78 are also provided on the microstrip plate between circuit strips 68 and 66. Elements 76 and 78 serve to provide the function of a low pass filter as described below.

Similarly, another pair of matching stubs 80, 82 are
They are provided at locations along the length of the feed strip 32, as described below.

One of the objects of the present invention is to remove most of the high frequency energy appearing at horn ridge 46 and thereby transferred to feedstrip 32 for further signal processing (which is outside the scope of the present invention). The circuit strip 66 provides a means for converting to intermediate frequency energy. There should be good isolation between the three ports for the mixer, which are defined by feed strip 32 and circuit strips 64 and 68. First, 1/4 wavelength stub 70,
72, a virtual short circuit of the X-band and K-band frequencies is formed at the connection point 30. Therefore, any X-band or K-band frequency energy appearing across mixer diode 74 will cause conductivity excursions by one or the other of the diodes (of course, horn element 16 is (Care must be taken to provide a good ground return for the local oscillator and IF frequencies on board 14). All of the energy reflected back to the feedstrip from mixer diode 74 is absorbed by out-of-phase reflections ( out of phase reflection). Thus, as much of the high frequency signal energy as possible is converted into IF signal energy, and the sensitivity of the radar detector to which the horn antenna structure of the present invention is mounted will therefore be increased.

Considering that the local oscillator frequency is approximately 6.0 GHz and the IF frequency is approximately 1.0 GHz, the low pass filter elements 76 and 78 are arranged and dimensioned to form a low pass filter of approximately 2.0 GHz. . This allows the IF signal 64 of the circuit strip 66 to be
Good isolation from the LO port or 32 high frequency ports is obtained.

Further, at the connection point 30, the X-band and K-band
It also eliminates the possibility of high frequency energy leaking through connection point 30 to either the LO port of circuit strip 64 or the IF output port of circuit strip 66 because a virtual short circuit is formed for the band frequency. absolutely guaranteed.

Because of the physical dimensions of the throat 47 of the horn between the sidewalls 44, the throat between the ridge 46 and the sidewalls 44 appears as a capacitive impedance at the first LO frequency, thus reducing the output from the horn 41 at the local oscillator frequency. There is no direct radiation and a return path to ground is provided for the LO signal. Furthermore, I.
The physical dimensions are such that there is no outward radiation of F frequency signals from the horn 41, since the throat 47 of the horn acts as an effective ground at the IF frequencies. Due to these facts,
Good isolation from the IF frequency port to the high frequency port and good isolation from the LO port to the high frequency port can be obtained.

Finally, the low pass filter provided by circuit elements 76 and 78 provides good isolation from the LO port to the IF port.

Microstrip plate 14 and mounting plate 14
The construction of, and other specific details of the circuit elements mounted or printed on, are not relevant to the present discussion.

(Effects of the Invention) As is clear from the above description, the present invention provides a horn antenna structure that operates at a predetermined frequency such as an X-band or K-band frequency (where the operating frequency is a horn ridge, and determined by the physical dimensioning of the throat area). A reliable and temperature-stable coupling of the tube and the electric field generated above it to the feed strip for the mixer diode is
This can be accomplished without tuning the local oscillator cavity or adjusting the physical mounting of the mixer diode in the throat of the microwave horn. Also, along with good signal isolation in the operation of some of the mixers, the local oscillator and the first intermediate frequency port, good energy conversion and thus high sensitivity are ensured. The appended claims define the limits of the invention.

[Brief explanation of drawings]

The accompanying drawings show an embodiment of a horn antenna structure for a microwave detection circuit according to the present invention, and FIG. 1 is an isometric view from below of a pressure-cast horn and associated shield cavity according to the present invention. .
FIG. 2 is a plan view of a mounting plate with a microstrip plate thereon according to the invention. FIG. 3 is a plan view of the mounting plate of FIG. 2 to which the pressure cast horn shown in FIG. 1 is attached; FIG. FIG. 4 is a cross-sectional view taken in the direction of arrow 4--4 in FIG. Fifth
The figure is a cross-sectional view taken in the direction of arrow 5--5 in FIG. FIG. 6 is a schematic diagram showing the mixer portion of the microstrip plate and its relationship to the horn. In the figure, 12...Mounting plate, 14...Microstrip plate, 16...One-piece molded horn element, 30... Connection point, 32... Feed strip,
42...Top wall, 44...Side wall, 46...Ridge, 47...
Throat, 48... Fastener means, 52, 54... Cavity, 60... Lens, 70, 72... Stub, 74...
Mixer diode, 80, 82...matching stub.

Claims (1)

[Scope of Claims] 1. A horn antenna structure with a microwave detection circuit comprising: a substantially rigid, flat mounting plate having an upper surface and a lower surface; a microstrip plate having two mixer diodes and a feed strip therefor, the feed strip being at or near a first end of the microstrip plate on an upper exposed side thereof; The microstrip plate is located in one piece having an open bottom, an upwardly flared top wall, a pair of side walls, and a downwardly extending ridge formed on the underside of the top wall. a molded horn element; the ridge extending rearwardly into the throat of the horn and extending downwardly at least in the throat region, the one-piece molded horn element being secured to an upper side of the mounting plate; a bottom edge of the ridge in the throat region makes physical and electrical contact with the feed strip, and a top surface of the mounting plate forms a bottom wall of the horn; The horn antenna structure characterized by: 2. The horn antenna structure according to claim 1, wherein at least a portion of the upper surface of the first mounting plate below the horn is coated with a conductive material. 3. The horn antenna structure according to claim 1, wherein the one-piece molded horn element is formed by pressure casting zinc. 4. The horn antenna structure of claim 1, wherein the microstrip plate has a pair of anti-parallel connected mixer diodes mounted in association therewith. 5. The horn antenna structure of claim 1, wherein the one-piece molded horn element is formed from an injection molded thermoplastic material having a conductive coating on at least its bottom side. 6. Claim 4 is characterized in that the lower surface of the mounting plate carries a printed circuit, and the upper surface thereof is plated to serve as a grounding surface at least in the horn region. The horn antenna structure. 7. The horn antenna structure of claim 4, wherein the one-piece molded horn element is secured to the mounting plate by fastener means passing through the mounting plate. 8. According to claim 4, said one-piece molded horn element is formed with at least one additional portion having a vertically extending wall and a top wall, said mounting plate or said microstrip plate The horn antenna structure is characterized in that a cavity is formed that covers and surrounds a portion of the circuit components attached to the horn antenna structure, thereby forming an insulating shield for the covered front circuit components. 9. In claim 8, a first cavity is formed behind the throat to cover and shield the microstrip plate having a first local oscillator coupled to the mixer diode. , wherein the ridge extends slightly into the first cavity. 10. In claim 4, the pressure cast zinc one-piece molded horn element has an , K-band frequencies. 11. The horn antenna structure of claim 10, wherein a lens is disposed at the front end of the horn element. 12. In claim 4, the feedstrip has at least one matching stub coupled thereto so that all of the energy reflected from the mixer diode of at least one frequency in which the horn is dimensioned is a quarter-wavelength stub of at least one frequency is disposed on a remote side of the mixer diode from the feed strip, and a connection between the quarter-wavelength stub and the mixer diode; The horn antenna structure is adapted to create a short circuit at the at least one frequency at a point, and furthermore a local oscillator and a low-pass filter for intermediate frequencies are also connected to the connection point. 13. In claim 12, the throat of the horn is dimensioned such that it appears as a capacitive impedance at the frequency of the local oscillator, thereby reducing energy from the horn at that frequency. Said horn antenna structure, characterized in that outward radiation is virtually eliminated. 14. Claim 13, characterized in that the mixer diode is connected on its side remote from the horn to quarter-wavelength stubs for X-band frequency and K-band frequency signals, respectively. Horn antenna structure.