Portable radio communication apparatus comprising an antenna member for a broad-band signal

In a portable radio communication apparatus comprising a handset (20) having a side surface (23) and a recessed surface (24), first and second antennae (51 and 52) of different resonance frequencies are fixed to the recessed surface by first and second conductive plates (55 and 56), respectively. First and second conductive lines (61 and 62) connect a common conductive line (63) to the first and the second antennae, respectively. The common conductive line is connected to an electro-audio and audio-electro converting device (30) to feed a transmitting electric signal to the first and the second antennae and to receive the received electric signal from the first and second antennae. The first and the second antennae have first and second antenna widths (W.sub.1 and W.sub.2), respectively. The first and the second conductive plates have first and second plate widths, respectively, and first and second axes centrally of the first and the second plate widths, respectively. The first and the second plate widths are not greater than the first and the second antenna widths, respectively. The first and the second axes are spaced wider than a half of a sum of the first and the second antenna widths.

BACKGROUND OF THE INVENTION 
This invention relates to a portable radio communication apparatus which 
consists of a handset and an antenna member in outline. 
It is general that a whip antenna or a sleeve antenna of a predetermined 
length is used as the antenna member for a portable radio communication 
apparatus of the type described. The whip antenna or the sleeve antenna is 
supported by a casing of the radio communication apparatus so as to 
protrude from the casing, which primarily serves as the handset. Inasmuch 
as the whip antenna or the sleeve antenna protrudes from the casing, a 
conventional radio communication apparatus is defective in that the radio 
communication apparatus is poor in portability and that the antenna is apt 
to be broken when the apparatus is carried by an owner. 
An improved radio communication apparatus is disclosed in Japanese 
Unexamined Patent Publication Ser. No. Syo 59-77724, namely, 77724 of 
1984. As will later be described with reference to several of nine figures 
of the accompanying drawing, the radio communication apparatus comprises a 
casing for a handset. The casing has a side surface, a recessed surface, 
and a connecting surface between the side and the recessed surfaces. An 
antenna member of a predetermined antenna width is fixed to the recessed 
surface by a conductive plate member of a predetermined plate length so 
that the antenna member does not protrude outwardly of the side surface. 
With this structure, the radio communication apparatus has a good 
portability because the antenna member does not project outwardly of the 
side surface. However, an antenna portion comprising the antenna and the 
conductive plate members becomes bulky in order to practically carry out 
communication of a signal of a broad frequency band. This is because the 
antenna width and the plate length should be increased for the broad-band 
communication as will later be described. If the antenna portion becomes 
large in size, portability becomes poor. Thus, the improved radio 
communication apparatus is not suitable to the broad-band communication. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide a portable radio 
communication apparatus which is suitable to broad-band communication. 
It is another object of this invention to provide a portable radio 
communication apparatus of the type described which is small in size. 
Other object of this invention will become clear as the description 
proceeds. 
A portable radio communication apparatus to which this invention is 
applicable comprises a handset having a side surface, a recessed surface, 
and a connecting surface between the side and the recessed surfaces, an 
antenna member, a conductive plate member fixing the antenna member to the 
recessed surface so that the antenna member does not protrude outwardly of 
the side surface, electro-audio and audio-electro converting means housed 
in and coupled to the handset for converting a received electric signal to 
a received audio signal and a transmitting audio signal to a transmitting 
electric signal, and a conductive line member for feeding the transmitting 
electric signal to the antenna member and for receiving the received 
electric signal from the antenna member. According to this invention, the 
antenna member comprises a first and a second antenna having different 
resonance frequencies and first and second predetermined points, 
respectively. The plate member comprises a first and a second conductive 
plate fixing the first and the second antennae to the recessed surface, 
respectively. The conductive line member comprises a first, a second, and 
a common conductive line. The first and the second conductive lines 
connect the common conductive line to the first and the second 
predetermined points, respectively. The common conductive line is 
connected to the electro-audio and audio-electro converting means to feed 
the transmitting electric signal to the first and the second antennae and 
to receive the received electric signal from the first and the second 
antennae.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a conventional portable radio communication apparatus 
will be described for a better understanding of this invention. The 
portable radio communication apparatus is substantially equivalent to the 
improved portable radio communication apparatus described in the preamble 
of the instant specification. The radio communication apparatus comprises 
a handset 20 and an antenna portion 21. The handset 20 has a handset 
casing 22 which is made of a conductive material and which has a box shape 
defining a hollow space therein. The handset casing 22 has a front surface 
which provides the handset 20, a side surface 23 opposed to the front 
surface, a recessed surface 24, and a connecting surface 25 between the 
side and the recessed surfaces 23 and 24. Although not depicted, the 
handset 20 comprises a transmitter and a receiver in the space. 
The antenna portion 21 comprises an antenna member 26 having a 
predetermined position which serves as a feeding point 27. The antenna 
member 26 has an antenna length L.sub.g, an antenna width W, and a free 
end spaced from the recessed and the connecting surfaces 24 and 25. 
A conductive plate member 28 of the antenna portion 21 fixes the antenna 
member 26 to the recessed surface 24 so that the antenna member 26 does 
not protrude outwardly of the side surface 23. The conductive plate member 
28 has a plate length t and a plate width which is narrower than the 
antenna width W. The plate length t is substantially same as a distance 
between the antenna member 26 and the recessed surface 24. 
An electro-audio and audio-electro converting device 30 is housed in the 
handset casing 22 and coupled to the handset 20. More particularly, the 
converting device 30 is connected to the receiver so as to convert a 
received electric signal to a received audio signal and to the transmitter 
so as to convert a transmitting audio signal to a transmitting electric 
signal. 
A feeding pin 31 of a conductive material is connected to the feeding point 
27. A conductive line 32 connects the feeding pin 31 and the converting 
device 30. The feeding pin 31 and the conductive line 32 are operable as a 
conductive line member which is for feeding the transmitting electric 
signal to the antenna member 26 and for receiving the received electric 
signal from the antenna member 26. The transmitting and the received 
electric signals, as herein called, are transmitted to and received from a 
counterpart radio communication apparatus and are radio signals which may 
have a common wavelength .lambda.. 
The wavelength .lambda. is typically of 900 MHz and is variable in a wide 
frequency band. The transmitting and the received electric signals may 
have different wavelengths in the frequency band. By way of example, the 
portable radio communication apparatus has an apparatus width A 
approximately equal to 0.12.lambda., an apparatus height H approximately 
equal to 0.55.lambda., and an apparatus depth D approximately equal to 
0.24.lambda.. With this structure, the portable radio communication 
apparatus has a good portability because the antenna member 26 does not 
protrude outwardly of the side surface 23. 
Referring to FIG. 2, a directivity of the antenna portion 21 of the radio 
communication apparatus will now be described. In the manner depicted in 
FIG. 1, X-Y-Z orthogonal coordinate axes are parallel to the apparatus 
width A, depth D, and height H, respectively. FIG. 2(a) shows the 
directivity in a plane comprising the Y and Z axes. FIG. 2(b) shows the 
directivity in another plane comprising the X and Z axes. FIG. 2(c) shows 
the directivity in still another plane comprising the X and Y axes. 
Throughout FIGS. 2(a) to (c), E.sub.74 represents an antenna gain as 
regards a vertically polarized wave component while E.sub..phi. represents 
another antenna gain as regards a horizontally polarized wave component. 
It is apparent from FIGS. 2(a) to (c) that the radio communication 
apparatus is capable of broadly radiating the vertically and the 
horizontally polarized wave components. It is therefore possible to carry 
out excellent communication without regard to the direction of the antenna 
member 26 and consequently to angles in which the handset casing 23 is 
held. 
Referring to FIG. 3, another conventional antenna portion 35 will be 
described. The antenna portion 35 is known as a micro strip antenna having 
an end which is grounded. The antenna portion 35 comprises an antenna 
member 36 of a rectangular shape having an antenna width W and an antenna 
length L.sub.g. The antenna member 36 has a predetermined position which 
serves as a feeding point 37. A conductive plate member 38 has a plate 
length t and a plate width W which is substantially equal to that of the 
antenna member 36. The plate length t is substantially equal to a distance 
between the antenna member 36 and the grounding conductive plate 39 which 
may be a portion of the handset casing 22 (FIG. 1) and grounds the 
conductive plate member 38. The grounding conductive plate 39 has a hole. 
A feeding pin 41 of a conductive material is put through the hole and is 
connected to the feeding point 37. The feeding pin 41 is insulated from 
the grounding conductive plate 39 around the hole periphery by an 
insulator. The antenna portion 21 illustrated in FIG. 3 becomes equivalent 
to that illustrated in FIG. 1 by narrowing the plate width W and by 
shortening the plate length t of the conductive plate member 38. In other 
words, the conductive plate member 38 of the antenna portion 21 shown in 
FIG. 3 has a decreased inductance in comparison with that illustrated in 
FIG. 1. Therefore, the conductive plate member 38 is electrically 
equivalent to that illustrated in FIG. 1. 
Referring to FIG. 4, an equivalent circuit of the antenna portion 35 
illustrated in FIG. 3 will now be described. The equivalent circuit is 
obtained when the antenna portion 35 is seen from the hole of the 
conductive plate 39. As is known in the art, the equivalent circuit has a 
series connection of an inductance L.sub.f and a resonance circuit which 
is composed of an inductance L, a capacitance C, and a resistance R. The 
inductance L, the capacitance C, and the resistance R are connected 
parallel to one another and are therefore operable as a parallel resonance 
circuit. The inductance L.sub.f is an inductance component of the feeding 
pin 41. The resistance R varies with a location of the feeding point 37 
and increases as the feeding point 37 becomes remote from the conductive 
plate member 38. The antenna portion 35 has a resonance frequency f.sub.0 
which is represnted by: 
EQU f.sub.0 =1/2.pi..sqroot.LC (1) 
Inasmuch as the antenna length L.sub.g is substantially equal to 
.lambda./4, the resonance frequency f.sub.0 is approximately decided by 
the antenna length L.sub.g of the antenna member 36. 
Referring to FIG. 5, a selectivity of the antenna portion 35 illustrated in 
FIG. 3 will now be described and is specified by a quality factor Q. The 
quality factor Q is decided by the antenna width W of the antenna member 
36 and the plate length or the distance t between the antenna member 36 
and the grounding conductive plate 39. Specifically, the quality factor Q 
is approximately inversely proportional to a product of the antenna width 
W and the distance t. 
Referring back to FIG. 1, the antenna portion 21 has an antenna 
characteristic similar to that of the antenna portion 35 illustrated in 
FIG. 3. As long as the radio communication apparatus is used for 
narrowband communication, the antenna width W and the plate length or the 
distance t may not be great as is apparent from FIG. 5. Therefore, the 
antenna portion 21 may be small. As a result, it is possible to realize a 
radio communication apparatus which has a good portability and a small 
size. 
However, the antenna portion 21 becomes large when the radio communication 
apparatus is used for broadband communication. Especially, a plurality of 
channels are used in such a communication system. This is because the 
antenna width W and the distance t must be increased for the broad-band 
communication in the manner which will be understood from FIG. 5. The 
antenna portion 21 has a frequency bandwidth determined by the resonance 
frequency thereof. Let the frequency bandwidth be, for example, about 
eight percent of the resonance frequency of the antenna portion 21 on 
condition that a VSWR (Voltage Standing-Wave Ratio) does not exceed 2. 
Under the circumstances, the antenna portion 21 occupies about six percent 
of an entire volume of the radio communication apparatus. When a cover is 
used in covering the antenna portion 21, the antenna portion 21 and the 
cover occupy about ten percent of the entire volume. 
In the hollow space, the handset casing 22 (FIG. 1) contains internal 
elements, such as the electro-audio and audio-electro converting device 
30, the transmitter, the receiver, and an electric power source for 
operating the converting device 30, the transmitter, and the receiver. 
When the antenna portion 21 becomes bulky with the portability of the 
handset 20 kept as it is, the space within the handset casing 22 
inevitably decreases. Such a decreased space makes it difficult to house 
the internal elements in the space. It is therefore difficult to realize 
the radio communication apparatus as a portable type. Thus, the radio 
communication apparatus is unsuitable to the broad-band communication. 
Referring to FIG. 6, a portable radio communication apparatus according to 
an embodiment of this invention comprises similar parts designated by like 
reference numerals. The antenna portion 21 comprises first and second 
antennae 51 and 52 which are operable as the antenna member 26 illustrated 
in FIG. 1 and which may be called radiating plates. The first and the 
second antennae 51 and 52 have first and second antenna lengths L.sub.g1 
and L.sub.g2, respectively. The first and the second antenna lengths 
L.sub.g1 and L.sub.g2 are different from each other so that the first and 
the second antennae 51 and 52 have different resonance frequencies f.sub.1 
and f.sub.2, respectively. The first and the second antennae 51 and 52 
have first and second antenna widths W.sub.1 and W.sub.2, respectively. 
The first and the second antennae 51 and 52 have first and second 
predetermined points serving as first and second feeding points 53 and 54, 
respectively. 
The antenna portion 21 further comprises first and second conductive plates 
55 and 56 which are operable in a manner similar to the conductive plate 
member 28 illustrated in FIG. 1. The first and the second conductive 
plates 55 and 56 fix the first and the second antennae 51 and 52 to the 
recessed surface 24, respectively. The first and the second conductive 
plates 55 and 56 have first and second plate widths, respectively. For 
convenience of description, first and second axes 57 and 58 are defined 
centrally of the first and the second plate widths of the first and the 
second conductive plates 55 and 56, respectively. The first and the second 
plate widths are not greater than the first and the second antenna widths 
W.sub.1 and W.sub.2, respectively. The first and the second conductive 
plates 55 and 56 have first and second plate lengths, respectively. 
In the antenna portion 21, the first and the second antennae 51 and 52 are 
substantially coplanar and are parallel to the recessed surface 24. That 
is, the first and the second plate lengths are substantially equal to each 
other. The first and the second plate lengths are given by first and 
second distances between the recessed surface 24 and the first and the 
second antennae 51 and 52, respectively. The first and the second antennae 
51 and 52 have first and second ends remote from the connecting surface 
25, respectively. Each of the first and the second ends is directed 
upwards of FIG. 6. The first and the second conductive plates 55 and 56 
fix the first and the second antennae 51 and 52 to the recessed surface 24 
at the first and the second ends, respectively. Each of the first and the 
second antennae 51 and 52 has a free end which is adjacent to the 
connecting surfaces 24 and 25 and which is spaced from the recessed and 
the connecting surfaces 24 and 25. The free end is directed downwards of 
FIG. 6. 
The radio communication apparatus further comprises first, second, and 
common conductive lines 61, 62, 63 which are operable in a manner similar 
to the conductive line member described in the conventional radio 
communication apparatus. The first and the second conductive lines 61 and 
62 connect the common conductive line 63 to the first and the second 
predetermined points 53 and 54, respectively. Specifically, the first, the 
second, and the common conductive lines 61, 62, and 63 are connected to 
one another at a line connecting point 64. The first and the second 
conductive lines 61 and 62 have first and second line lengths l.sub.1 and 
l.sub.2, respectively. The common conductive line 63 is connected to the 
electro-audio and audio-electro converting device 30 to feed the 
transmitting electric signal to the first and the second antennae 51 and 
52 and to receive the received electric signal from the first and the 
second antennae 51 and 52. 
The first and the second conductive lines 61 and 62 have first and second 
feeding pins 65 and 66 connected to the first and the second feeding 
points 53 and 54, respectively. First and second coaxial cables are used 
for the first and the second conductive lines 61 and 62, respectively. 
Each of the first and the second coaxial cables has an inner conductor and 
an outer conductor. The outer conductor is mechanically and electrically 
connected to the handset casing 22. Inasmuch as the handset casing 22 is 
made of a conductive material, the handset casing 22 shields the internal 
elements from an electromagnetic field. 
Referring to FIG. 7, an equivalent circuit of the antenna portion 21 will 
now be described. It can be understood that the antenna portion 21 has a 
pair of antenna portions 35 as illustrated in FIG. 3. Inasmuch as the 
antenna portion 35 has an equivalent circuit shown in FIG. 4, it is 
apparent that the antenna portion 21 has the equivalent circuit shown in 
FIG. 7. 
Like in FIG. 4, first and second pin inductances L.sub.f1 and L.sub.f2 are 
representative of inductance components of the first and the second 
feeding pins 65 and 66, respectively. A first partial antenna portion is 
equivalently represented by inductance L.sub.f1 and a parallel resonance 
circuit which is composed of resistance R.sub.1, inductance L.sub.1, and 
capacitance C.sub.1. Similarly, a second partial antenna portion is 
represented by inductance L.sub.f2 and a parallel circuit of resistance 
R.sub.2, inductance L.sub.2, and capacitance C.sub.2. First and second 
resistances R.sub.1 and R.sub.2 vary with locations of the first and the 
second feeding points 53 and 54, respectively. The first and the second 
resistances R.sub.1 and R.sub.2 increase as the first and the second 
feeding points 53 and 54 become remote from the first and the second 
conductive plates 55 and 56, respectively. 
It will be assumed that the antenna portion 21 has an impedance 
characteristic Z.sub.0 when the antenna portion 21 is seen from the line 
connecting point 64. Inasmuch as the antenna portion 21 is represented by 
a pair of LCR parallel resonant circuits as shown in FIG. 7, the impedance 
characteristic Z.sub.0 can approximately be converted to another impedance 
characteristic of an LCR series resonant circuit by selecting 
predetermined values for the first and the second line lengths l.sub.1 and 
l.sub.2, respectively. 
It will furthermore be assumed that .lambda..sub.0 represents a wavelength 
of the transmitting or the received electric signal which is propagated 
through the first or the second conductive line 61 or 62. Taking the pin 
impedances L.sub.f1 and L.sub.f2 into consideration, each of the first and 
the second line lengths l.sub.1 and l.sub.2 is approximately equal to 
(.lambda..sub.0 /8+n.lambda..sub.0 /2), where n represents an integer 
which is equal to or greater than zero. 
The antenna portion 21 is thus specified by the first and second partial 
antenna portions as mentioned above. The first partial antenna portion 
comprises the first antenna 51, the first conductive plate 55, and the 
first conductive line 61. The second partial antenna portion comprises the 
second antenna 52, the second conductive plate 56, and the second 
conductive line 62. It is assumed that the first partial antenna portion 
has a first partial impedance at the second resonance frequency f.sub.2, 
when seen from the line connecting point 64 and that the second partial 
antenna portion has a second partial impedance at the first resonance 
frequency f.sub.1, when seen from the line connecting point 64. Inasmuch 
as the first resonance frequency f.sub.1 is separated from the second 
resonance frequency f.sub.2, each of the first and the second partial 
impedances has a large imaginary part and a high impedance value in the 
LCR series resonance circuit. As a result, the radio communication 
apparatus has an impedance characteristic of a double resonance type 
wherein an impedance related to the first antenna 51 appears in the 
vicinity of the first resonance frequency f.sub.1 while another impedance 
related to the second antenna 52 appears in the vicinity of the second 
resonance frequency f.sub.2. That is to say, it may be understood that the 
first antenna 51 mainly operates in the vicinity of the first resonance 
frequency f.sub.1 while the second antenna 52 mainly operates in the 
vicinity of the second resonance frequency f.sub.2. 
Referring to FIG. 8, reflection loss characteristics of the antenna 
portions 21 illustrated in FIGS. 1 and 6 will now be described. The 
antenna portion 21 illustrated in FIG. 6 has a reflection loss 
characteristic 71 while the antenna portion 21 illustrated in FIG. 1 has 
another reflection loss characteristic 72. In FIG. 8, the abscissa 
represents a normalized frequency f/f.sub.0 of the transmitting and the 
received electric signal of the antenna portion 21 illustrated in FIGS. 1 
and 6. The ordinate represents reflection loss. When the resonance 
frequency f.sub.0 is 900 MHz, the antenna portion 21 illustrated in FIG. 6 
has the first resonance frequency f.sub.1 approximately equal to 876 MHz 
and the second resonance frequency f.sub.2 approximately equal to 923 MHz. 
It is apparent from FIG. 8 that the antenna portion 21 illustrated in FIG. 
6 has a double resonance characteristic described above. In the antenna 
portion 21 illustrated in FIG. 6, the VSWR of a medium point between the 
first and the second (normalized) resonance frequencies f.sub.1 /f.sub.0 
and f.sub.2 /f.sub.0 becomes worse as a frequency difference between the 
second and the first resonance frequencies f.sub.2 and f.sub.1 becomes 
large. The VSWR of each of the first and the second (normalized) resonance 
frequencies f.sub.1 /f.sub.0 and f.sub.2 /f.sub.0 can be controlled by 
varying each of the first and the second resistances R.sub.1 and R.sub.2 
illustrated in FIG. 7. The first and the second resistances R.sub.1 and 
R.sub.2 can be adjusted by the locations of the first and the second 
feeding points 53 and 54, respectively. 
Under the circumstances, the frequency difference and the locations of the 
feeding points 53 and 54 are selected so that the VSWR of the medium point 
does not exceed an allowable VSWR in the radio communication apparatus 
illustrated in FIG. 6. As a result, the antenna portion 21 of the radio 
communication apparatus illustrated in FIG. 6 is suitable to the 
broad-band communication. 
Referring back to FIG. 6, description will now be made about a gap g 
between the first and the second antennae 51 and 52, in order to consider 
that mutual coupling between the first and the second antennae 51 and 52 
which has been ignored so far. Inasmuch as the mutual coupling actually 
exists between the first and the second antennae 51 and 52, restriction is 
imposed on a width of the gap g when the first and the second antennae 51 
and 52 are attached to the handset casing 22. For example, an excessively 
narrow gap g makes it difficult to independently select the first and the 
second resonance frequencies f.sub.1 and f.sub.2 because the mutual 
coupling becomes large. Under the circumstances, the gap g is decided in 
consideration of the mutual coupling. In addition, the first and the 
second plate widths are not greater than the first and the second antenna 
widths W.sub.1 and W.sub.2, respectively. The first and the second axes 57 
and 58 are spaced from each other by a spacing s. The mutual coupling 
decreases as the spacing s becomes long. Experimentally, as the spacing s 
becomes long, a gap g becomes short. However, the gap g is substantially 
constant in a case where the spacing s is wider than a half of a sum of 
the first and the second antenna widths W.sub.1 and W.sub.2. The spacing s 
is selected so that it is wider than a half of (W.sub.1 +W.sub.2). Thus, 
the first and the second axes 57 and 58 are spaced wider than the half in 
the radio communication apparatus. 
The first and the second conductive plates 55 and 56 have first and second 
plate sides outwardly parallel to the first and the second axes 57 and 58, 
respectively. The first and the second antennae 51 and 52 have first and 
second antenna sides outwardly of the first and the second axes 57 and 58, 
respectively. The first and the second conductive plates 55 and 56 fix the 
first and the second antennae 51 and 52 to the recessed surface 24 with 
the first and the second plate sides rendered coplanar with the first and 
the second antenna sides, respectively. In other words, the first and the 
second conductive plates 55 and 56 are integrally joined to the most 
widthwise outward parts of the upper ends of the first and the second 
antennae 51 and 52, respectively. This makes it possible to narrow the gap 
g. In the radio communication apparatus, the gap g is equal to about 
.lambda./100. Thus, the first and the second antennae 51 and 52 can be 
located adjacent to each other. 
Referring to FIG. 8 again, the reflection loss characteristics 71 and 72 
are obtained as regards a case where the resonance frequency f.sub.0 is 
approximately equal to a half of a sum of the first and the second 
frequencies f.sub.1 and f.sub.2. 
The conventional radio communication apparatus illustrated in FIG. 1 has a 
first antenna volume which is defined by the antenna member 26 and the 
distance t. The radio communication apparatus illustrated in FIG. 6 has a 
second antenna volume equal to a sum of first and second partial antenna 
volumes and a gap volume. The first partial antenna volume is defined by 
an area of the first antenna 51 and the first distance. The second partial 
antenna volume is defined by an area of the second antenna 52 and the 
second distance. The gap volume is defined by the gap g, a longer one of 
L.sub.g1 and L.sub.g2, and a longer one of the first and the second 
distances. For comparison of the apparatus illustrated in FIGS. 1 and 6, 
it is assumed in FIG. 8 that the second antenna volume is approximately 
equal to the first antenna volume. From the reflection loss 
characteristics 71 and 72, it is possible to estimate a bandwidth .DELTA.f 
of each of the radio communication apparatus illustrated in FIGS. 1 and 6 
under the condition of VSWR.ltoreq.3. More particularly, a ratio 
.DELTA.f/f.sub.0 of the bandwidth .DELTA.f to the frequency f.sub.0 is 
approximately equal to 8 percent in the radio communication apparatus 
illustrated in FIG. 1. On the other hand, the radio communication 
apparatus illustrated in FIG. 6 has the ratio .DELTA.f/f.sub.0 which is 
approximately equal to 13 percent. Thus, the bandwidth .DELTA.f of the 
radio communication apparatus illustrated in FIG. 6 is about 1.5 times 
that of the radio communication apparatus illustrated in FIG. 1. 
Referring to FIGS. 9(a) to (c), a directivity of the antenna portion 21 of 
the radio communication apparatus illustrated in FIG. 6 will now be 
described. In the manner depicted in FIG. 6, X-Y-Z orthogonal coordinate 
axes parallel to the apparatus width, depth, and height, respectively. 
FIG. 9(a) shows the directivity in a plane including the Y and Z axes. 
FIG. 9(b) shows the directivity in another plane including the X and Z 
axes. FIG. 9(c) shows the directivity in still another plane including the 
X and Y axes. Throughout FIGS. 9(a) to (c), F.sub..theta. represents an 
antenna gain as regards a vertically polarized wave component while 
E.sub..phi. represents another antenna gain as regards a horizontally 
polarized wave component. 
Although either the first antenna 51 or the second antenna 52 mainly 
operates for the frequency of the transmitting or the received signal as 
described above, the directivity does not vary due to the frequency. 
Inasmuch as the directivity is approximately equal to the directivity 
illustrated in FIGS. 2(a) to (c), no substantial influence is exerted on 
the directivity by dividing the antenna portion 21 into two partial 
antenna portions, as mentioned above. 
It is now appreciated that this invention provides a portable radio 
communication apparatus which is suitable to broad-band communication. The 
portable communication apparatus is small in size. 
While this invention has thus far been described in conjunction with an 
embodiment thereof, it will be readily possible for those skilled in the 
art to put this invention into practice in various other manners. In the 
portable radio communication apparatus illustrated in FIG. 6, the first 
and the second resonance frequencies f.sub.1 and f.sub.2 can be controlled 
by controlling the first and the second antenna lengths L.sub.g1 and 
L.sub.g2, respectively. From this view, the antenna portion 21 illustrated 
in FIG. 6 can be operated as an antenna for communication of a signal of 
two frequency bands spaced from each other by selecting the VSWR in each 
of the two frequency bands at a value which is not greater than an 
allowable value.