Directional antenna system including pattern control

A directional antenna system is disclosed which selectively couples two radiating antenna elements to a transceiver through a selective phase, magnitude and matching network which is controlled by the output of a logic circuit. The network provides for equal magnitude current coupling between the transceiver and the two antennas while simultaneously selectively producing either positive or negative approximately 90.degree. phase shifts between the two antennas to produce either of two discrete directive cardioid radiation patterns directed in substantially opposite directions. The logic circuit, in conjunction with a manual step switch, provides for a manually selecting either of the two cardioid radiation patterns, as well as producing a figure eight or an omnidirectional radiation pattern. For generating a transceiver omnidirectional pattern, one antenna is used and the other is connected to a standard broadcast band receiver. Matching networks are simultaneously selectively connected between the two antennas and the transceiver such that maximum power transfer and impedance matching is maintained for different radiation patterns. An automatic scanning switch is coupled to the logic circuit and provides for automatically selecting one of the cardioid radiation patterns as an optimum pattern in which the signal from the remote site is most strongly received by the transceiver. Indicating lights are provided to indicate which one of the radiation patterns is generated for the transceiver.

BACKGROUND OF THE INVENTION 
The present invention generally relates to the field of communication 
apparatus which use directive antennas radiators. In particular, the 
present invention relates to the use of such apparatus with a mobile 
transceiver radio. 
In the past radios and transceivers have generally used omnidirectional 
radiation patterns. Thus the standard transceiver antenna is an 
omnidirectional quarter wavelength radiator. The use of this type of 
radiation pattern makes it impossible for a transceiver to determine what 
direction a signal is being received from. Often times this information is 
extremely important to the transceiver operator. In addition, the use of 
an omnidirectional radiation pattern fails to provide any way for the 
operator of a transceiver to avoid interferring signals. Thus a strong 
signal coming from off to the side of the transceiver or from the rear of 
the transceiver can totally prevent the transceiver from communicating 
with a remote location directly ahead of the transceiver. Such a result is 
obviously undesirable. 
Some base station (fixed location) antennas have generated "directive 
radiation patterns" in response to a manual radiation pattern selection 
process. Generally, this manual process consists of mechanically rotating 
an antenna which generates a single directive beam. Such techniques are 
too costly and too complicated for implementation on a mobile 
installations, such as on an automobile. The term "directive radiation 
pattern" is commonly understood to refer to those patterns in which the 
radiated radio frequency (R.F.) energy of a transmitter, for example, is 
substantially concentrated in one horizontal direction while being 
substantially reduced and having a null in another horizontal direction. 
While it is known that altering the phase between radiating elements can 
result in electrically rotating a directional beam, such systems have not 
been successfully applied to mobile installations, since a uniform 
effective ground plane is not normally available for the radiating antenna 
elements. In addition, prior art antenna phasing systems do not provide 
for maintaining equality between the radiation currents present in the 
phased radiating antennas when the phase between radiating elements is 
changed. Thus beam uniformity is destroyed since it was impossible to 
produce two substantially similar radiation patterns that were directed in 
substantially opposite directions. 
In the past, dual CB (Citizen Band) antennas have been mounted on motor 
vehicles. However, these antennas have been mounted in a direction 
perpendicular to the direction of movement of the motor vehicle and these 
antennas have only been simultaneously utilized with substantially zero 
phase existing between the two antennas. These dual "cophase" antennas are 
used only to produce a single radiation pattern which is generally egg 
shaped and which is only marginally stronger in both the front and rear 
directions of the automobile movement while providing substantially no 
isolation for the transceiver from signals off to the side of the 
automobile. Thus these dual antennas only provide a single radiation 
pattern which cannot be used to indicate the location of a remote 
transmission site with respect to the transceiver, and cannot be used to 
avoid interferring signals which are not directly in line between the 
transceiver and the remote site. If the automobile had a standard 
broadcast band receiver, in addition to a CB transceiver with dual 
antennas, an additional separate antenna must be provided for the 
broadcast receiver. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an improved directional 
antenna system which overcomes all of the aforementioned defiencies. 
A more particular object of the present invention is to provide an improved 
directional antenna system in which a plurality of discrete directive 
radiation patterns are produced which enable the operator of a 
communication device to avoid interferring signals which are not directly 
in line between the communication device and a desired remote site. 
Another object of the present invention is to provide an improved 
directional antenna system in which a plurality of discrete directive 
radiation patterns are selectively generated for a communication means 
whereby information is provided as to the location of a remote transmitter 
site with respect to the communication means. 
A further object of the present invention to provide an improved 
directional antenna system in which one of a plurality of radiation 
patterns is selected, preferrably automatically, as an optimum radiation 
pattern. 
A still further object of the present invention is to provide an improved 
directional antenna system in which a plurality of directive radiation 
patterns are produced by selectively creating various phase differences 
between at least two simultaneously utilized antennas elements while 
simultaneously insuring that similar radiation patterns are produced by 
providing for substantially equal magnitude current coupling between the 
antenna elements producing the radiation pattern and a transceiver means. 
An additional object of the present invention is to provide an improved 
directional antenna system in which a minimum number of antenna elements 
are utilized for a transceiver and a separate receiver operating at 
different frequencies. 
In an embodiment of the present invention an improved directional antenna 
system is provided, comprising: communication means operative at a carrier 
frequency for establishing communications with a remote site; means 
coupled to said communication means for selectively generating a plurality 
of discrete directive radiation patterns for said communication means; and 
means coupled to said radiation pattern generating means for automatically 
selecting one of said radiation patterns as an optimum radiation pattern, 
said automatically selected optimum radiation pattern corresponding to the 
one pattern of said plurality of patterns in which a desired signal is 
most strongly received by said communication means, whereby the automatic 
selection of an optimum radiation pattern enables the communication means 
to avoid interferring signals which are not directly in line between the 
communication means and the remote site. 
The present invention also provides an improved directional antenna system 
comprising: communication means, including a plurality of antenna elements 
for providing radiation patterns, for establishing communications with a 
remote site; and means coupled to said antenna elements for selectively 
generating a plurality of discrete directive radiation patterns for said 
communication means by simultaneously utilizing at least two of said 
antenna elements, the plurality of radiation patterns including at least 
two radiation patterns directed in substantially opposite directions, said 
radiation pattern generating means including a network for selectively 
creating various phase differences between said simultaneously used 
antenna elements in said plurality of antenna elements while 
simultaneously providing for substantially equal magnitude current 
coupling between said utilized antenna elements and said communication 
means. 
In the preferred embodiment of the present invention, two radiating antenna 
elements are spaced a quarter of a wavelength apart and are mounted on a 
motor vehicle in a line parallel to the straight line of movement of the 
motor vehicle. These two antenna elements are selectively utilized to 
generate the plurality of discrete directive radiation patterns for a 
transceiver which is carried by the motor vehicle, the plurality of 
radiation patterns including at least two substantially similar radiation 
patterns having nulls directed in substantially opposite directions. These 
two oppositely directed patterns are preferrably cardioid in shape. 
The preferred embodiment of the present invention also includes an 
indicating means which is located adjacent to the transceiver and 
indicates which one of the plurality of radiation patterns is selectively 
generated for the transceiver means by the radiation pattern generating 
means. In addition, automatic selecting means is provided for selecting 
the optimum radiation pattern of said two oppositely directed radiation 
patterns during which a desired signal from the remote site is most 
strongly received by the communication means. In this manner, the 
indicator means will provide information as to the location of the remote 
site with respect to the transceiver means. Also, manual selection of any 
one of the plurality of discrete directive radiation patterns is provided 
in the present invention. This enables the operator of the communication 
means to avoid interfering signals which are not directly in line between 
the communication means and the remote site by selecting a radiation 
pattern which more effectively screens out these unwanted signals. 
In addition, an AGC magnitude indication is provided, which, together with 
said pattern indicating means, permits manual determination of the 
location of the remote site. Also only two antenna elements are used to 
create both omnidirectional and directive radiation patterns for a 
transceiver, while also selectively providing radiation patterns for a 
separate receiver.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a motor vehicle 10 on which are mounted first and second 
radiating citizen band (CB) antenna elements 11 and 12, respectively, 
which are positioned in accordance with the teachings of the present 
invention. The distance between the antenna elements 11 and 12 is 
approximately one quarter of a wavelength at a frequency in the middle of 
the CB frequency range. These two antenna elements are positioned in a 
line substantially parallel to the straight of movement of the motor 
vehicle. Perferably, the antenna elements 11 and 12 would both be mounted 
on either the right or left hand side of the motor vehicle, one on the 
cowl portion of the automobile and the other generally on the rear fender. 
In general, the present invention contemplates simultaneously utilizing 
both of the antenna elements 11 and 12 while selectively providing 
predetermined positive and negative phase differences between these 
antennas elements to selectively produce either of two oppositely directed 
cardioid radiation patterns, as well as other radiation patterns. One of 
the cardioid radiation patterns will be directed in the forward motion 
direction of the motor vehicle 10, and therefore have a null in the 
opposite direction, while the other radiation pattern will be directed in 
the rearward motion direction of the vehicle 10. Thus by selectively 
generating these cardioid radiation patterns, a CB transceiver operative 
at a carrier frequency can utilize the antenna elements 11 and 12 and 
effectively communicate with a remote site directly in front of the motor 
vehicle 10 without receiving interferring signals of the same frequency 
from a transmitter operating directly to the rear of the motor vehicle 10 
and vice versa. Thus the present invention enables a CB transceiver to 
avoid interferring signals which are not directly in line between the 
transceiver and the remote site which the operator of the transceiver 
wishes to communicate with. Directive beams other than cardioid beams can 
also be generated from the radiating elements 11 and 12, and the narrower 
these beams, the more resolution and the more effective the antenna system 
would be in avoiding the reception of unwanted signals. Also, when 
directive CB radiation patterns are not needed, antenna 12 can be used to 
generate an omnidirection CB radiation pattern while antenna 11 can 
generate a separate omnidirectional radiation pattern for an AM broadcast 
band receiver. 
FIG. 2 illustrates a communication apparatus 15 which utilizes the 
radiating antenna elements 11 and 12 illustrated in FIG. 1. The apparatus 
15, together with the antenna elements 11 and 12 comprise the directive 
antenna system of the present invention. In FIG. 2, as well as all other 
Figures, identical reference numbers will be used to identify 
corresponding elements. 
The communications apparatus 15 basically comprises a CB transceiver 16 
which includes a transmitter portion and a receiver portion both operable 
at selected carrier frequencies. The receiver portion is contemplated as 
developing an automatic gain control (AGC) signal which has a magnitude 
inversely related to the strength of a CB signal received by the receiver 
portion. The receiver and transmitter portions of the transceiver 16 are 
selectively connected through a transmission line coaxial cable 17 to an 
external terminal 18 of a selective phase, magnitude and matching network 
19. The network 19 also has external terminals 20 and 21. The terminal 20 
is connected to a terminal 22 through a transmission line cable 23, and 
the terminal 22 is coupled to ground through a matching capacitor 24 and 
coupled to the radiating antenna element 11 through a loading coil 25. 
Similarly, the radiating element 12 is coupled by a loading coil 26 to a 
terminal 27 that is coupled to ground through a matching capacitor 28 and 
coupled to the terminal 21 through a transmission line 29. Essentially, 
the network 19 couples the CB transceiver 16 to the radiating antenna 
elements 11 and 12 and selectively provides (1) the proper phase 
difference between the radiating antenna elements, (2) control of the 
magnitude of the radiation currents in the antenna elements with respect 
to the CB transceiver current, and (3) impedence matching between the 
transceiver 16 and the radiating antenna elements 11 and 12. 
The network 19 is controlled by a logic circuit 30 which is coupled thereto 
and supplies a plurality of control signals to the network 19. The logic 
circuit 30 is also coupled to the CB transceiver 16 by an electrical 
connection 31 which couples the AGC voltage of the transceiver 16 to the 
logic circuit 30. An oscillator 32 produces a relatively low frequency 
signal, e.g. 3 Hz, which is coupled to the logic circuit 30 and functions 
as a low frequency timing signal for the circuit 30. A scan activation 
switch 33 is also coupled to the logic circuit 30 and so is a step switch 
34. An indicator means 35 having a plurality of indicating lights is also 
coupled to the logic circuit 30. 
In essence, the logic circuit 30 supplies a plurality of control signals to 
the network 19 which cause the network to generate any one of a plurality 
of discrete directive radiation patterns for the CB transceiver 16 by 
simultaneously utilizing the antenna elements 11 and 12 and selectively 
creating different phase relationships between the antennas elements. The 
circuit 30 also selectively causes the network 19 to generate 
omnidirectional radiation patterns. The exact operation of the logic 
circuit 30 and its relationship to the network 19 will be discussed in 
greater detail subsequently. 
FIG. 3 represents a perferred mechanical embodiment of the present 
invention in which the elements 30 through 35 are contained in a box shape 
container 36 which is attached to a housing 37 of the CB transceiver 16. 
The box type container 36 contains a manually actuatable scan switch 
designated as 33 and a manually actuatable step switch designated as 34, 
in addition to a plurality of indicating lights. The container 36 also has 
a meter 38 which indicates the strength of the AGC signal of the receiver 
portion of the transceiver 16. The electrical connection 31 between the 
transceiver 16 and the logic circuit 30 is contemplated as being provided 
by a pin and socket arrangement forming an electrical connection through 
the housing 37 and the box type container 36. In addition, the box 
container 36 is also contemplated as housing a substantial portion of the 
selective phase, magnitude and matching network 19. 
FIGS. 4A through 4G illustrate the horizontal radiation patterns which can 
be implemented by selectively altering the phase relationship between the 
simultaneously utilized radiating elements 11 and 12, as well as 
selectively utilizing either of the radiating elements 11 or 12. 
FIG. 4A merely illustrates a diagramatical horizontal plane view of the 
motor vehicle 10 and the radiating elements 11 and 12 which can generate 
the radiation patterns 4B through 4G. In FIG. 4A, the elements 11 and 12 
are illustrated as being located in the center, rather than on the right 
or left side, of the vehicle 10. The patterns in FIGS. 4B through 4G are 
those created by centrally locating the antenna elements as shown in FIG. 
4A. If the elements are located on the right or left side of the vehicle, 
then the resultant patterns would be skewed in the direction of the larger 
metallic surface of the vehicle. 
FIG. 4B illustrates the horizontal radiation pattern which results when 
only the radiating element 12 is excited. The radiation pattern is 
omnidirectional, but is somewhat skewed or distorted in the direction of 
the larger metallic surface of the motor vehicle 10. FIG. 4C illustrates 
the resultant horizontal radiation pattern if only the radiating element 
11 is excited. Neither of these patterns has a substantial null in any 
horizontal direction. 
FIG. 4D illustrates a cardioid radiation pattern which is produced when the 
radiating elements 11 and 12 are excited such that the radiation current 
in the element 11 is equal to that in the element 12 and has positive 
approximately 90.degree. phase shift with respect to the current in the 
element 12. This cardioid radiation pattern generally extends in the 
rearward direction of motion of the motor vehicle 10 and has a substantial 
null in the forward direction. 
FIG. 4E illustrates a substantially similarly shaped cardioid radiation 
pattern which extends in the forward direction of motion of the vehicle 10 
and has a substantial null in the rearward direction. This forward 
directional cardioid pattern is produced by having equal radiation 
currents in the elements 11 and 12, but having the radiation current of 
the element 11 having a negative approximately 90.degree. phase 
relationship with respect to the radiation current of the element 12. 
For generating the cardioid radiation patterns 4D and 4E for the present 
invention, it has been found that a substantially 70.degree. phase 
difference between the elements 11 and 12 will produce a much more 
desirably shaped cardioid radiation pattern, in that more of the radiation 
pattern will be directed in the primary front or rear directions and less 
of the pattern directed in the null rear or front directions. 
FIG. 4F illustrates the radiation pattern produced when a 180.degree. phase 
shift exists between equal radiation currents in the antenna 11 and 12. 
FIG. 4G illustrates the radiation pattern produced when a 0.degree. phase 
relationship exists between equal radiation currents in the elements 11 
and 12. This pattern corresponds to the pattern produced by the dual 
"co-phase" antennas previously discussed, except that here the maximum 
gain of the radiation pattern is perpendicular to direction of movement of 
the automobile 10. No substantial horizontal null direction exists for 
this pattern. 
FIG. 5 illustrates a preferred construction of the selective phase, 
magnitude and matching network 19 (now shown dashed) with terminals 
corresponding to the terminals 18, 20 and 21 being identically number. The 
terminal 18 is directly coupled to a rotor (wiper arm) terminal of a four 
position rotary switch 40 (shown dashed). In the first, second, third and 
fourth positions of the rotary switch 40, the terminal 18 is connected to 
terminals 41, 42, 43 and 44, respectively. The network 19 also comprises a 
similar four position rotary switch 50 which has a rotor terminal directly 
connected to the terminal 20 and first, second, third and fourth position 
terminals 51, 52, 53 and 54, respectively. Also, the network 19 includes 
another four position rotary switch 60 having a rotor terminal directly 
connected to the terminal 21 and first, second, third and fourth position 
terminals 61 through 64, respectively. The operation of the switches 40, 
50, and 60 is contemplated as being sychronized such that all of the 
switches will either be in their first, second, third, or fourth positions 
at the same time. The control signals received from the logic circuit 30 
determine what position these switches will be in. While rotary position 
switches are illustrated for the switches 40, 50 and 60, it is 
contemplated that electronic switching using PIN diodes which respond to 
electrical control voltage biasing can be used instead of manual or motor 
driven rotary switches. 
The terminal 51 is coupled to ground through a capacitor 65 and is coupled 
to the terminal 41 through an inductor 66. The terminal 41 is directly 
connected to ground through a capacitor 67. The terminal 51 is also 
coupled to the terminal 61 through a 180.degree. phase shift network 
comprising two series connected "L" shaped inductor and capacitor networks 
68 and 69. The terminal 52 is coupled to a terminal 70 through an inductor 
71 connected in series with a variable capacitor 72. The terminal 70 is 
coupled to the terminal 62 through a variable capacitor 73 and is coupled 
to the terminal 42 through an impedance matching network 74 shown in block 
form. Similarly, the terminal 63 is coupled to a terminal 80 through an 
inductor 81 connected in series with a variable capacitor 82, and the 
terminal 80 is coupled to the terminal 53 through a variable capacitor 83 
and to the terminal 43 through a matching network 84. The terminal 44 is 
directly connected to the terminal 64 and the terminal 54 is isolated from 
all other terminals and is connected to an AM broadcast band radio 85. The 
components 40 through 84 comprise all of the essential elements of the 
network 19 illustrated in FIG. 5. 
The network 19 described in the preceding paragraph enables the 
communication apparatus 15 illustrated in FIG. 2 to generate the radiation 
patterns illustrated in FIGS. 4B, 4D, 4E and 4F for the transceiver 16. 
With the switches 40, 50 and 60 in their first positions, a 180.degree. 
phase shift is provided between the terminals 20 and 2l by the networks 68 
and 69, and the elements 65 through 67 impedance match the parallel 
radiation resistances of the elements 11 and 12 at the terminal 51 such 
that a 50 ohm input impedance is presented at the terminal 18 for the CB 
transceiver 16. With the switches in this position the figure eight 
radiation pattern shown in FIG. 4F is produced. 
With the switches 40, 50 and 60 in their fourth positions, only the 
radiating element 12 is excited by the CB transceiver 16, and the CB 
radiation pattern shown in FIG. 4B is produced. In this position the 
radiating element 11 is connected to the AM radio 85 and generates the 
pattern in FIG. 4C for the AM radio. This AM radiation pattern will not 
substantially interfere with the CB radiation pattern produced by the 
element 11 since the transceiver 16 and the AM radio 85 operate at 
different carrier frequencies. 
With the switches 40, 50 and 60 in their second positions, the radiation 
pattern illustrated in FIG. 4D is produced. In this position, the 
radiation current present in the antenna element 11 has a positive 
90.degree. phase with respect to the radiation current in the element 12. 
This phase difference is provided by the presence of the inductor 71. The 
fact that the capacitors 72 and 73 are variable represents an important 
aspect of the present invention. These capacitors should be variable so 
that when the CB transceiver 16 is operative as a transmitter, the 
capacitors could have been adjusted to produce equal magnitude radiation 
currents in the radiating elements 11 and 12. Stating this operation in 
the converse fashion. When the CB transceiver is operative as a receiver, 
the terminal 70 should receive equal magnitude currents from the elements 
11 and 12. This is important since the successful generation of a 
desirable cardioid radiation pattern requires that the radiating currents 
in the elements 11 and 12 be substantially equal. If these currents are 
not substantially equal, a distorted cardioid radiation pattern will be 
produced and this will result in a radiation pattern in which the null is 
not substantially directed in either the forward or reverse directions of 
the vehicle movement. The nonequality of the currents can also result in 
the radiation pattern failing to have any substantial null. The matching 
network 74 is provided to alter the impedance present at the terminal 70 
such that a 50 ohm input impedence is present at the terminal 18. 
With the switches 40, 50 and 60 in their third positions, the radiation 
pattern illustrated in FIG. 4E is produced in a similar manner with 
corresponding components functioning similarly. 
Thus the network 19 in FIG. 5 illustrates a phase, magnitude and matching 
network which selectively simultaneously utilizes the antenna elements 11 
and 12 and provides for a plurality of cardioid radiation patterns while 
simultaneously providing for substantially equal magnitude current 
coupling between the radiation currents in these antenna elements and the 
transceiver apparatus 16. When a 90.degree. phase shift is produced 
between the radiating elements 11 and 12, one of these elements would 
appear to have a radiation resistance of approximately 2 ohms, while the 
other of these elements would have a radiation resistance of approximately 
10 ohms. If the voltage supplied by the transceiver 16 were merely equally 
divided between the two radiating elements, as would normally be the case 
in prior art phase implementing networks, then the radiating current 
produced in the antenna elements 11 and 12 would be vastly different, and 
nothing resembling a cardioid radiation pattern would be produced. The 
present invention overcomes this problem by providing a network in which 
not only is an approximately 90.degree. phase shift between radiating 
elements implemented, but also equal current coupling between the two 
radiating elements and a transceiver is also simultaneously implemented. 
The equal current coupling is provided by adjusting the capacitance 
magnitude of the variable capacitors and this insures the generation of a 
proper cardioid pattern. With a properly generated cardioid radiation 
pattern, the present invention enables a CB mobile apparatus mounted on a 
vehicle to selectively totally ignore all CB transmissions occuring either 
behind or in front of the direction of motion of the vehicle and 
essentially concentrate the CB transceiver sensitivity in either a forward 
or rear direction. 
The radiation patterns shown in FIGS. 4C and 4G represent possible 
radiation patterns which can be produced for the transceiver 16 by a 
network similar to the network 19 if the switches 40, 50 and 60 are made 
additionally complex by having more positions. It should be realized that 
FIG. 4G essentially represents the radiation pattern of a dual "co-phase" 
antenna in which both radiating elements are fed with 0.degree. phase 
difference. This antenna pattern is totally unsuitable for avoiding the 
pick up of unwanted CB signals which are not being transmitted directly in 
line between the CB transceiver and a remote site. This is because the 
radiation pattern is really substantially omnidirectional in its shape and 
has no direction in which a substantial null in the radiation pattern is 
created. 
The operation of the logic circuit 30 will now be explained in detail. A 
specific implementation of this logic circuit has not been illustrated 
because it is believed that any person skilled in the art could construct 
such a circuit to perform the following functions which will now be 
described. 
The logic circuit 30 is contemplated as receiving a low frequency 
oscillating signal from the oscillator 32. When the scan button 33 is 
depressed, this will cause a counter in the logic circuit 30 to count the 
signal oscillations produced by the oscillator 32. The count of this 
counter will sequentially supply control signals to the network 19 such 
that the switches 40, 50 and 60 are sequentially moved through all of 
their possible positions. While this is occuring, a storage circuit in the 
logic circuit 30 receives the AGC signal of the transceiver 16 along the 
line 31 for each radiation pattern generated. A holding register will hold 
the count of the counter that corresponds to the lowest AGC signal 
produced by the transceiver 16 while the antenna patterns are being 
sequentially scanned. This can be readily implemented by a minimum signal 
detector circuit controlling the loading of the counter count into the 
holding register. Therefore this holding register count will correspond to 
the position of the switches 40, 50 and 60 which resulted in the lowest 
AGC signal. On the next count of the counter after all of the sequential 
radiation patterns have been scanned, the logic circuit 30 will cause the 
count being stored in the holding register, which corresponds to the count 
that produced the lowest AGC signal, to be stored in the counter and no 
further counting will occur. This in essence will produce the same logic 
signals to the selective network 19 that originally produced the lowest 
AGC signal on the line 31. In this manner, the logic circuit 30 and the 
selective network 19 automatically select one of the radiation patterns as 
an optimum radiation pattern wherein this optimum radiation pattern 
corresponds to the radiation pattern in which a desired signal is most 
strongly received by the transceiver means. This is because the lowest AGC 
signal will be produced in response to the strongest signal being received 
by the transceiver. 
If the logic circuit 30 is designed such that it only sequentially steps 
between the two cardioid directive radiation patterns, then this automatic 
radiation pattern selecting apparatus will result in selecting the 
directive radiation pattern which is more nearly directed towards the 
remote site which the CB transceiver desires to communicate with. 
The indicator 35 merely represents a visual indication of which one of the 
radiation patterns is being generated by the radiating antenna elements 11 
and 12. Thus for the network 19 shown in FIG. 5, four indicating lights 
would be provided, each one separately corresponding to the generation of 
one of the radiation patterns 4B, 4D, 4E, or 4F. 
If the logic circuit 30 scans only through the radiation patterns 4D and 
4E, it will select only the radiation pattern which provides the strongest 
received signal to the CB transceiver 16. This selected radiation pattern 
will then be indicated by the indicator 35 and this will indicate whether 
the remote site which the CB transceiver desired to communicate with is 
located in front of or behind the motor vehicle 10. This information can 
often times be extremely valuable to the operator of the mobile CB 
transceiver. Many times transmissions are received which merely inform the 
listener that an accident has occured somewhere on the highway. Without 
knowing whether the transmission originated in front of or behind the 
vehicle 10, it would be impossible for the driver of motor vehicle 10 to 
know whether he should turn off the highway because of the possibility of 
traffic congestion developing ahead due to the accident. 
The manual step switch 34 merely represents a switch which will cause the 
logic circuit 30 to sequentially step the selective network 19 through 
each of the possible radiation patterns in response to each manual 
depression of the step switch 34. This of course can merely be implemented 
by having the manual step switch 34 increment a counter whose count 
controls the position of the switches 40, 50 and 60. In this manner, the 
communication apparatus 15 will not only provide an automatic indication 
of which radiation pattern produces the strongest received signal by use 
of the scanning switch 33, but will also enable the operator of the 
transceiver 16 to avoid interferring signals by selecting a radiation 
pattern which may be weaker in the direction of the remote site but has a 
null advantageously positioned for minimizing the effect of interferring 
signals which are not directly in line between the transceiver and the 
remote communication site which the transceiver desires to communicate 
with. In addition, the AGC signal strength meter 38, visually indicates 
the magnitudes of the received signal. This in conjunction with the manual 
step switch and indicating lights would enable the transceiver operator to 
manually determine the location of a remote transmitting site by comparing 
the AGC signal strengths for each directive radiation pattern generated. 
It should also be pointed out that in the fourth position of the switches 
40, 50 and 60, the terminal 54 is connected to a seperate AM radio 
broadcast receiver 85. This provides for having the transceiver 16 
connected to the radiating element 12 and producing a generally 
omnidirectional radiation pattern such as that shown in FIG. 4B, while a 
separate AM radio apparatus is coupled to the radiating element 11. In 
some applications it is desirable to simultaneously monitor both the AM 
broadcast band as well as the CB band. The present invention therefore, 
conveniently provides two radiating antenna elements which can 
independently perform this function, while providing for utilizing both of 
the antenna elements in the CB frequency band to produce directive CB 
radiation patterns whenever CB transmission or reception is solely 
desired. 
While we have shown and described specific embodiments of this invention, 
further modifications and improvements will occur to those skilled in the 
art. All such modifications which retain to basic underlying principles 
disclosed and claimed herein are with the scope of this invention.