3 band communication equipment

A three band antenna unit for reception of radio waves in the AM and FM bands and for reception and transmission of radio waves in the UHF band as well as its connection with filters and a communication equipment are disclosed. The antenna unit includes an upper, first element for reception and transmission of a radio wave in the UHF band and a lower, second element for reception of radio waves in the FM band, both connected to a mobile telephone. An AM band signal from the first element is transmitted to the lower, second element through an AM band pass filter. A radio wave signal from the lower, second element is transmitted to an AM/FM tuner through an AM/FM band pass filter. AM band radio wave signal received by the upper, first element which is used for reception and transmission of a radio wave in the UHF band is synthesized with the AM band radio wave signal received by the lower, second element which is used for reception of radio wave in the FM band before it is transmitted to the AM/FM tuner, which therefore exhibits a high AM band reception sensitivity.

FIELD OF THE INVENTION 
The invention relates to 3 band communication equipment for reception of 
radio waves of AM and FM bands and for reception and transmission of UHF 
band radio wave. 
BACKGROUND OF THE INVENTION 
Where individual antennas are provided for reception of radio broadcasting 
waves in the AM and FM bands and for reception and transmission of 
commercial radio telephone wave and/or personal communication wave in the 
UHF band, the resulting increased number of antennas requires an extended 
space for their installation. Accordingly, it is desirable that these 
antennas be integrated into a substantially single antenna unit. Japanese 
laid-Open Patent Application No. 46,601/1985 discloses a substantially 
integrated 3 band antenna in which an upper, first element for reception 
of radio wave in the UHF band and a lower, second element for reception of 
radio waves in the AM and FM bands are coaxially disposed and integrally 
constructed. The second element is used in common for the reception of 
radio waves in the AM and FM bands, but it will be recognized that 
ideally, the length of the second element be one-quarter the wavelength 
.lambda..sub.f of the radio wave of the FM band for reception thereof. If 
the length of the second antenna is chosen equal to .lambda..sub.f /4, 
there results a degraded reception sensitivity for radio waves in the AM 
band inasmuch as wavelengths of radio waves in the AM band are generally 
by two orders of magnitudes greater than the wavelength of radio wave in 
the FM band. Accordingly, where an AM receiver which is adapted for use 
with a devoted AM band reception antenna is used, it must be additionally 
provided with an amplifier. 
SUMMARY OF THE INVENTION 
It is an object of the invention to enhance the reception sensitivity of 
radio waves in the AM band for a communication equipment which utilizes a 
3 band antenna. 
A 3 band communication equipment according to the invention comprises a 3 
band antenna (1 to 4) including an upper, first element (1) for reception 
and transmission of a radio wave in the UHF band and a lower, second 
element (2) for reception of a radio wave in the FM band, both of which 
are disposed coaxially, a UHF band receiver/transmitter (7) connected to 
the upper, first element (1), a filter (5) connected to the upper, first 
element (1) for deriving an AM band radio wave signal, means (13, 14) for 
synthesizing the AM band radio wave signal derived by the filter (5) with 
a radio wave signal from the second element (2), and an AM/FM band wave 
receiver (9) connected to the means (13, 14). It is to be understood that 
numerals appearing in the parentheses denote corresponding elements 
illustrated in an embodiment shown in the drawings and to be described 
later. 
With this communication equipment, the AM band wave signal from the upper, 
first element (1) is synthesized with the radio wave signal from the 
lower, second element (2) by the filter (5) and the synthesizing means 
(13, 14) to be transferred to the AM/FM band receiver (9), thus enhancing 
the reception sensitivity of AM band radio wave by the AM/FM band receiver 
(9). Where an AM wave receiver adapted for use with a devoted AM band 
reception antenna is used, an amplifier which has been added to such 
receiver in the prior art practice can be eliminated or may have a low 
gain. 
Other objects and features of the invention will become apparent from the 
following description of an embodiment thereof with reference to the 
drawings.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring to FIG. 1, a first element 1 For reception and transmission of a 
radio wave in the UHF band slidably extends through a cap 21 and is 
secured to an insulator 22i of a feeder cable 22 by a locking structure, 
not shown. A matching coil 3 is loaded in the insulator 22i and has its 
one end connected to the first element 1 while the other end is connected 
to a feeder rod 4 of the cable 22. A feeder base 17 is secured to the 
lower end of the cable 22, to which the feeder rod 4 is electrically 
connected. A second element 2 for reception of FM band waves comprises a 
telescopic assembly of divided sleeves 2a, 2b, 2c and 2d of increasing 
diameters which are fitted inside the adjacent sleeves in a telescopic 
manner. One end of the sleeve 2a is fixedly connected with the cap 21 and 
the lower end of the sleeve 2d is fixedly connected to a cylindrical 
insulator base 19, through which the feeder cable 22 extends. 
A connecting rod 18 which is electrically insulating and flexible is 
secured to the feeder base 17. While not shown, the rod 18 is bent into a 
U-configuration, with a vertical drive mechanism being coupled to the 
bend. By driving the rod 18 upwardly, the feeder cable 22 can be displaced 
to the upper position shown in FIG. 1. By driving the rod 18 downwardly 
when it occupies such upper position, the feeder cable 22 is lowered. The 
descending movement of tile cable 22 takes place by initially sliding the 
first element 1 down with respect to the cap 21 until its top head bears 
against tile cap 21, whereupon the cap 21 and the first sleeve 2a are 
driven downward together with the first element 1 by a sliding movement 
with respect to the second sleeve 2b until the lower end surface of the 
cap 21 bears against the top of the second sleeve 2b, whereupon the second 
sleeve 2b is driven downward together with the first element 1, the cap 21 
and the first sleeve 2a by a sliding movement with respect to the third 
sleeve 2c. In this manner, the first element 1 and the cap 21 move down 
while accompanying a shrinkage of the second element 2. When the second 
element 2 shrinks to its limit, the fourth sleeve 2d moves down until the 
top of the sleeve 2d moves down close to the upper end face of a rubber 
bushing 23 in the form of an O-ring, which represents the limit of 
downward movement and where the telescopic shrinkage ends. 
A contact assembly 20 is secured to the insulator base 19 and comprises a 
ring body secured to the base 19, and a plurality of leaves which extend 
from the body toward the center of the base 19. As shown in FIG. 1, when 
the feeder cable 22 is in its upper position, the leaves are engaged by 
the feeder base 17. 
The insulator base 19 is located inside a pole 24 of an insulator. A 
bracket 25 and a metal enclosure 10 are fixedly mounted on the pole 24. 
The rubber bushing 23 in the form of an O-ring is filled around the upper 
end face of the pole 24, which is then inserted through an opening formed 
in a metal roof 11 of an automobile. A bracket 16 is fitted around the 
opening, and is then screwed into the bracket 25, whereby the bracket 25 
can be fixedly mounted on the roof 11 of the automobile. It will be 
appreciated that the metal enclosure 10 is electrically connected to the 
automobile roof 11 through the bracket 25. A terminal base 26 having a low 
pass filter 5, a high pass filter 6 and a low pass filter 8 embedded 
therein is fixedly mounted around the enclosure 10. 
The low pass filter 5 has an input end connected to a contacting reed 15 
which is disposed in sliding contact with the contact assembly 20 and an 
output end connected to a contacting reed 14 which is disposed in sliding 
contact with the fourth sleeve 2d of the second element 2, with a ground 
terminal of the filter being connected to the metal enclosure 10. 
The high pass filter 6 includes an input terminal connected to the 
contacting reed 15 disposed in sliding contact with the contact assembly 
20, and an output terminal connected to the input; of a mobile UHF 
automobile telephone 7 through a terminal member 27, with a ground 
terminal of the filter 6 being connected to the metal enclosure 10. The 
ground terminal of the mobile telephone 7 is also connected to the metal 
enclosure 10 through the terminal member 27. 
The low pass filter 8 includes an input terminal connected to a contacting 
reed 13 which is disposed in sliding contact with the fourth sleeve 2d of 
the second element 2 and an output terminal connected to the input of a 
radio tuner 9 which is adapted to receive broadcasting radio waves in the 
AM and FM bands through a terminal member 28, with a ground terminal of 
the filter 8 being connected to the metal enclosure 10. The radio tuner 
includes a ground terminal which is also connected to the metal enclosure 
through the terminal member 28. 
FIG. 2 shows an electrical circuit formed by the mechanical connections or 
contacts mentioned above. Considering a signal in the UHF band, it will be 
seen that a capacitive coupling between the second element 2 on one hand 
and the metal enclosure 10, brackets and roof 11 on the other hand places 
the second element 2 substantially at the same potential as the metal 
enclosure 10, whereby the second element 2, the metal enclosure 10, the 
insulator 22i (FIG. 1) and the feeder rod 4 constitute together a coaxial 
cable 12 which connects the first element 1 and the high pass filter 6 
together. An impedance presented by the first element 1 and the matching 
coil 3 is equal to the characteristic impedance of the coaxial cable 12, 
thereby allowing an efficient transmission of a radio wave signal between 
the first element 1 and the mobile telephone 7. 
The First element 1 has a length which is equal to one-half the wavelength 
.lambda..sub.u of the radio wave (in the UHF band) received by and 
transmitted by the mobile telephone 7. The second element 2 has a length 
which is substantially equal to one-quarter the FM reception wavelength 
.lambda..sub.f. The mobile telephone 7 is connected the feeder rod 4 which 
is in turn connected to the first element 1 through the contacting reed 15 
and the high pass filter 6, the latter transmitting a signal of 
frequencies in the UHF band. The low pass filter 5 is also connected to 
the feeder rod 4 through the contacting reed 15. The low pass filter 5 
transmits the radio wave signal in the AM band which is received by the 
first element to the contacting reed 13 through the contacting reed 14 and 
the second element 2. In other words, there appears on the contacting reed 
13 an electrical signal which represents a synthesis of electrical signals 
corresponding to the radio wave in the AM band received by the first 
element 1 and the radio wave received by the second element 2. The low 
pass filter 8 is effective to derive a radio wave in either AM or FM band 
from the synthesized signal appearing on the contacting reed 13 for 
transmission to the radio tuner 9. The tuner 9 is adapted to cooperate 
with a radio receiver for AM and FM bands. Since the AM radio wave signal 
from the first element 1 which is used for reception and transmission of a 
radio wave in the UHF band is transmitted through the filter 5, contacting 
reed 14, second element 2, contacting reed 13 and low pass filter 8 to the 
tuner 9 associated with the AM/FM receiver, the signal level applied to 
the tuner 9 is high, increasing its reception sensitivity. Where an AM 
receiver (9) adapted to be used with a devoted AM band reception antenna 
is used only a low gain is required of an amplifier which midst be added 
to the receiver or such amplifier may be eliminated. 
While a preferred embodiment has been shown and described, it should be 
understood that a number of changes and modifications are possible therein 
such as replacing the mobile telephone 7 by a personal radio communication 
equipment which utilizes a UHF band wave, replacing the low pass filter 5 
by a band pass filter or band E filter which passes signals in the 
frequencies of the AM band. Accordingly, it is to be understood that there 
is no intention to limit the invention to the precise construction 
disclosed herein, and the right is reserved to all changes and 
modifications coming within the scope of the invention as defined in the 
appended claims.