Antenna with integral transmission line section

An antenna (105) for receiving radio frequency (RF) signals includes a conductive element (300) having a first electrical length and a first operating impedance and a transmission line (315) having a second electrical length and a second operating impedance for resonating the conductive element (300) at a predetermined operating frequency. A coaxial element (305) having a third electrical length is coupled to the conductive element (300) and the transmission line element (315) for converting the first operating impedance to the second operating impedance. When the conductive element (300) is resonated, the first, second, and third electrical lengths are substantially equal to a quarter wavelength or an odd multiple thereof at the predetermined operating frequency.

FIELD OF THE INVENTION 
This invention relates in general to radio communication, and more 
specifically to monopole antennas for receiving radio signals. 
BACKGROUND OF THE INVENTION 
Conventional paging receivers utilize many types of antennas for receiving 
signals having specific frequencies. Typically, antenna size and shape 
varies with both the frequency of the signals the antenna is to receive 
and the size and shape of the paging receiver which houses the antenna. 
For instance, in many low frequency applications, such as in the low VHF 
(very high frequency) bands, the antenna takes the form of a ferrite loop 
antenna connected to the receiver. In the UHF (ultra high frequency) band, 
antennas are often wireform loop antennas or dipole antennas. In each 
case, however, the antenna must not only function electrically, but also 
physically fit into the paging receiver. 
As technology has advanced, a greater number of features has been included 
in paging receivers due to customer demands. Many of these features, such 
as alphanumeric displays, real time clocks and alarms, musical alerts, 
etc., require a large amount of complex circuitry for implementation, 
which tends to increase the size of a paging receiver including such 
features. At the same time, however, market trends have dictated that 
paging receivers become smaller and lighter such that a user can easily 
carry a paging receiver without strain or discomfort. These conflicting 
requirements have necessarily resulted in paging receivers in which the 
space available for accommodating an antenna has decreased. One solution 
to this problem is to reduce the size of the antenna. This cannot always 
be done, however, without adversely affecting the electrical performance 
of the radio receiver. 
In addition to becoming smaller, paging receivers have, in response to 
customer demand, been manufactured in various form factors for customer 
convenience. For example, paging receivers have been manufactured in a 
"credit card" or pen form for carrying in a shirt pocket and a watch form 
for wearing on the wrist. The number of different form factors in which 
paging receivers are manufactured is almost limitless, and, for each of 
these different form factors, antennas must be designed which not only 
physically fit within the paging receiver, but also function electrically 
such that the paging receiver can receive the desired signals. 
Additionally, antennas which are internal are usually surrounded by 
components which are not part of the antenna but which can interact with 
the antenna to reduce its gain and performance. Thus, what is needed is an 
antenna which can be better isolated from its environment, allowing for 
compact and internal antenna designs which meet or exceed the performance 
of conventional antenna designs. 
SUMMARY OF THE INVENTION 
An antenna for receiving RF signals at a predetermined operating frequency 
comprising a first elongated conductor and a second elongated conductor 
having first and second ends opposite each other, wherein the first end of 
the second elongated conductor is electrically coupled to an end of the 
first elongated conductor. A third elongated conductor surrounds the 
second elongated conductor and has first and second ends, wherein the 
first end of the third elongated conductor is proximal to the first end of 
the second elongated conductor and the second end of the third elongated 
conductor is proximal to the second end of the second elongated conductor 
and electrically coupled to a ground for the antenna. An insulator located 
between the second and third elongated conductors provides electrical 
insulation therebetween. A runner plated on an insulative substrate has a 
first end electrically coupled to the second end of the second elongated 
conductor and has a second end electrically coupled to the ground for the 
antenna. The runner further has a terminal formed between the first and 
second ends of the runner for providing the RF signals to receiving 
circuitry.

DESCRIPTION OF A PREFERRED EMBODIMENT 
FIG. I is an electrical block diagram of a radio receiver 100 for receiving 
radio frequency (RF) signals. The radio receiver 100 comprises an antenna 
105 configured for receiving a predetermined range of frequencies and 
coupled to receiving circuitry 110 for processing the received RF signals 
provided thereto by the antenna 105. When the radio receiver 100 is a 
paging receiver, the receiving circuitry 110 typically comprises a 
receiver 115 for demodulating the received RF signal and a 
decoder/controller 120 coupled to the receiver 115 for recovering from the 
demodulated RF signal a selective call message, which is subsequently 
stored in a memory 125. The receiving circuitry 110 can further comprise 
an alert mechanism 130 for emitting an audible tone in response to 
reception of the selective call message and a display 135 for displaying 
the selective call message to a user. 
The radio receiver 100 can be embodied in many different housing form 
factors designed in response to customer demand. For example, credit card 
housing form factors have been designed for carrying in shirt pockets, and 
watch housing form factors have been designed for wearing on the wrist. 
Additionally, as shown in FIG. 2, the radio receiver 100 can be embodied 
in a pen housing form factor for clipping to a pocket, belt, or briefcase. 
In this case, the radio receiver 100, including the antenna 105 and the 
receiving circuitry 110, must physically fit into a housing which is not 
only very small, but is also extremely narrow. Consequently, the antenna 
105 must be designed to both fit within the housing and function 
electrically to provide the RF signal to the receiving circuitry 110. 
Referring next to FIG. 3, a top orthographic view of the radio receiver 
100, including the antenna 105 (FIG. 1) according to the present 
invention, is shown. The antenna 105 comprises a first elongated conductor 
forming a monopole element 300, which is a high impedance element that 
functions as the primary radiating element of the antenna 105. In 
accordance with a preferred embodiment of the present invention, the 
monopole element 300 extends outwards from a substrate, such as a printed 
circuit board 302 which is typically lossy and which can collect stray 
signals that sometimes interfere with antenna reception. In alternate 
embodiments of the present invention, however, the monopole element 300 
can be supported by the printed circuit board 302 or an insulative sleeve 
(not shown) to prevent stress and breakage of the monopole element 300. 
The energy collected by the monopole element 300 is provided to a coaxial 
element 305, which preferably extends along the same axis as that along 
which the monopole element 300 is located. Alternatively, the coaxial 
element 305 can be bent or manipulated for accommodation within different 
form factor housings or for layout on different printed circuit board 
designs. The coaxial element 305 is supported by the printed circuit board 
302 and preferably comprises an inner conductor 307, i.e., a second 
elongated conductor, having a first end electrically coupled to the 
monopole element 300. Additionally, the coaxial element 305 further 
includes an outer conductor 310, i.e., a third elongated conductor, which 
surrounds and is electrically insulated from the inner conductor 307 by an 
insulator (not shown). The outer conductor 310 is electrically coupled to 
a ground plane (not shown) for providing a ground potential, e.g., 
voltage, at an end 312 opposite the monopole element 300. The coaxial 
element 305 preferably functions as an impedance-converting element. In 
other words, the coaxial element 305 converts from the high impedance of 
the monopole element 300 to a lower impedance. 
As mentioned above, the first end of the inner conductor 307 is 
electrically coupled to the monopole element 300. The second end of the 
inner conductor 307 is electrically coupled to a first end of a 
transmission line element 315 of the antenna 105. The transmission line 
element 315 is preferably formed by printed circuit runners plated on top 
and bottom surfaces of the printed circuit board 302 along the same axis 
as that along which the monopole element 300 and the coaxial element 305 
are formed. The end of the transmission line element 315 which is distant 
from the coaxial element 305 is preferably coupled to the ground plane, as 
will be described in greater detail below. 
As shown in FIG. 3, the monopole element 300, the coaxial element 305, and 
the top plate of the transmission line element 315 of the antenna 105 are 
all extending from, supported by, and formed on, respectively, a first 
surface of the printed circuit board 302. The ground plane mentioned above 
is preferably located on a second surface of the primed circuit board 302 
opposite the antenna 105. It will be appreciated that the second surface 
of the printed circuit board 302 can be the other outer layer of the board 
302 or, alternatively, an inner layer of a multi-layer printed circuit 
board. The transmission line element 315 can be electrically coupled to 
the ground plane in a variety of ways, such as by a wire soldered to the 
transmission line element 315 and the ground plane or by a one or more 
holes 320 drilled through the substrate 302 at the appropriate location, 
then plated to provide coupling between the transmission line element 315 
and the ground plane. The outer conductor 310 of the coaxial element 305, 
which is coupled to the ground plane at the end 312, can also be coupled 
to the ground plane by a plated hole 326 drilled through the printed 
circuit board 302. In this situation, the outer conductor 310 can be 
either soldered directly to a pad 324 on the printed circuit board 302 
which is coupled to the ground plane by the plated hole 326, or a ground 
strap 322 can be electrically connected to both the outer conductor 310 
and a pad 324 on the printed circuit board 302 which is coupled to the 
ground plane by a plated hole 326. According to the present invention, the 
ground strap 322 and the length of the coaxial element 305 can be 
advantageously adjusted to optimize antenna performance by varying the 
resonant frequency of a circuit formed by the outer conductor 310, the 
ground plane 505, and the interconnect therebetween. 
In accordance with the preferred embodiment of the present invention, the 
transmission line element 315 further comprises a terminal 328 which is 
electrically coupled to the receiving circuitry 110 to provide received RF 
signals thereto. When the receiving circuitry 110 is mounted on the first 
surface of the printed circuit board 302, as shown, the terminal 328 can 
simply be a printed circuit board runner coupled directly to the receiving 
circuitry 110. Alternatively, when the receiving circuitry 110 is mounted 
on the opposite side of the printed circuit board 302, a plated hole (not 
shown) can be utilized to electrically couple the receiving circuitry 110 
to the transmission line element 315. When the receiving circuitry 110 is 
not mounted on the printed circuit board 302 at all, an actual connector, 
e.g., a coaxial connector, can be employed as the terminal 328. The 
position of the terminal 328 along the length of the transmission line 
element 315 is primarily determined by the driving impedance of the 
receiving circuitry 110, as will be described in greater detail below. 
FIG. 4 is a partial perspective view of the antenna 105 (FIG. 1) in 
accordance with the preferred embodiment of the present invention. As 
shown, the inner conductor 307 of the coaxial element 305 (FIG. 3) is 
insulated from the outer conductor 310 by an insulator 400 surrounding the 
inner conductor 307. The inner conductor 307 is coupled to the monopole 
element 300 at a first end and to the transmission line element 315 at the 
opposite end. 
The monopole element 300, the inner conductor 307 of the coaxial element 
305, the insulator 400, and the outer conductor 310 can all be formed from 
a conventional coaxial line. When a conventional coaxial line is utilized, 
a predetermined length of the outer conductor 310 is simply stripped from 
the coaxial line, thereby forming a first elongated conductor, i.e., the 
monopole element 300. It will be appreciated that, for support reasons, 
the insulator 400 of the coaxial line can, if necessary, be left in place 
around the monopole element 300 without significantly affecting the 
electrical performance of the antenna 105. 
Alternatively, the monopole element 300 and the inner conductor 307 of the 
coaxial element 305 can be formed from a single wire, such as a 
conventional beryllium copper wire. When a standard wire is utilized to 
form the monopole element 300 and the inner conductor 307, an end is 
preferably plated with tin or another solderable material such that the 
inner conductor 307 can be easily soldered, or electrically connected in 
another way, to the transmission line element 315. In this situation, the 
insulator 400 can be a pre-formed cylinder of insulating material which is 
slipped over the wire serving as the inner conductor 307. The insulating 
material should be a low loss dielectric material, such as polyethylene. 
The outer conductor 310 can be formed either by plating the exterior of 
the insulator 400 with a low resistance conductive material, such as 
copper, or by surrounding the insulator 400 with a pre-formed low 
resistance, conductive cylinder. The ground strap 322 for coupling the 
outer conductor 310 to the ground plane, via a pad 324 and a plated hole 
326, can be manufactured from any low resistance conductor, then soldered 
to both the outer conductor 310 and the pad 324. Alternatively, the ground 
strap 322 could be eliminated entirely if the outer conductor 310 is 
formed such that it can be directly soldered to the pad 324. 
In accordance with the preferred embodiment of the present invention, the 
transmission line element 315 comprises metallization, such as copper, 
plated onto the printed circuit board 302 in accordance with conventional 
printed circuit board plating techniques. As described above, the inner 
conductor 307 can be electrically coupled to the transmission line element 
315 in a number of ways, such as by soldering or welding. 
Referring next to FIG. 5, a side view of the antenna 105 (FIG. 1) and the 
printed circuit board 302 is depicted. In accordance with the preferred 
embodiment of the present invention, the printed circuit board 302 has 
printed thereon a ground plane 505 on the surface opposite the antenna 
elements. The ground plane 505 is printed on the printed circuit board 302 
using conventional techniques and methods and is coupled to different 
portions of the antenna 105, such as by the plated holes 320, 326. As 
shown, the plated hole 320 is drilled through the printed circuit board 
302 at the far end of the transmission line element 315, then plated with 
a conductive material to electrically couple the far end of the 
transmission line element 315 to the ground plane 505. Additionally, a 
second plated hole 326 is drilled through the printed circuit board 302 at 
the end of the outer conductor 310 near the transmission line element 315. 
The second plated hole 326 electrically couples a pad 324 (FIG. 4) to the 
ground plane 505. As mentioned above, a ground strap 322 can be utilized 
to electrically connect the outer conductor 310 to the pad 324. 
FIG. 6 is a perspective view of the antenna 105' in accordance with an 
alternate embodiment of the present invention. As shown, the printed 
circuit board 302' for this alternate embodiment includes an extension 605 
on which a printed circuit board runner is plated which serves as the 
monopole element 300'. For better performance, the monopole element 300' 
further includes a printed circuit board runner (not shown) plated on the 
opposite surface of the printed circuit board extension 605, which reduces 
losses. The two runners forming the monopole element 300' are preferably 
coupled by a plurality of plated holes 610. According to the alternate 
embodiment of the present invention, the inner conductor 307' of the 
coaxial element 305' is soldered at a first end to the monopole element 
300', as shown, and at a second end to the transmission line element 315'. 
The use of this alternate embodiment simplifies manufacturing of the 
antenna 105'. 
It will be appreciated that FIGS. 1-6 are not shown to scale; rather, FIGS. 
1-6 are depicted in a manner which facilitates understanding of the 
antenna 105. 
The different elements of the antenna 105 can be initially designed using 
the following formulas as guidelines: 
##EQU1## 
The variables and symbols included in each of formulas 1-9 are described 
below. 
______________________________________ 
SYMBOL DESCRIPTION 
______________________________________ 
D diameter of outer conductor 310 
d diameter of inner conductor 307 
.epsilon. dielectric constant of insulator 400 
.epsilon..sub.re 
effective dielectric constant 
Z.sub.o,c characteristic impedance of coaxial element 
305 
.epsilon..sub.r 
dielectric constant of substrate (printed 
circuit board 302) 
W width of transmission line element 315 
h thickness of substrate (printed circuit board 
302) between transmission line element 315 
and ground plane 505 
Z.sub.o,t characteristic impedance of transmission line 
element 315 
.theta..sub.1 
length of transmission line element 315 in 
radians 
R driving impedance of receiving circuitry 110 
R.sub.b modified driving impedance of receiving 
circuitry 110 
Q quality factor of antenna 105 
c speed of light (3 .times. 10.sup.8 meters/second) 
f frequency at which antenna 105 is to receive 
RF signals 
.lambda..sub.o 
wavelength of RF signal in free space 
.lambda..sub.d 
wavelength of RF signal in dielectric 
l.sub.1 length of transmission line element 315 
l.sub.2 length of coaxial element 305 
l.sub.3 length of monopole element 300 
______________________________________ 
It will be appreciated that these formulas presented above merely describe 
a starting point for the theoretical design of the antenna 105, and that 
experimentation is usually required to achieve the final design of an 
antenna 105 having optimum performance. 
Design example referring to formulas 1-9 and the table of variables 
therefor: 
The dimensions of the antenna 105 can be calculated using formulas 1-9 
given values for the characteristic impedance (Z.sub.o,c) of the coaxial 
element 305, the characteristic impedance (Z.sub.o,t) of the transmission 
line element 315, the diameter (D or d) of either the inner conductor 307 
or the outer conductor 310, the dielectric constant () of the insulator 
400, the dielectric constant ( .sub.r) of the printed circuit board 302, 
the thickness (h) of the printed circuit board 302 between the ground 
plane 505 and the transmission line element 315, the quality factor (Q) of 
the antenna 105, the driving impedance (R) of the receiving circuitry 110, 
and the frequency (f) at which the antenna 105 is to receive RF signals. 
By way of example, the dimensions of the antenna 105 can be calculated if 
the following values are known: 
Z.sub.o,c =Z.sub.o,t =50.OMEGA., 
d=0.0254 centimeters (cm), 
=2.2, 
.sub.r =4.5 
h=0.0762 cm, 
Q=30, 
R=50.OMEGA., and 
f=930 Megahertz (MHz). 
Using formula (1), it can be seen that the free space wavelength .lambda. 
is approximately equal to 32.26 centimeters (cm) as calculated using the 
speed of light (c=3.times.10.sup.8 meters/second) and a frequency of 930 
MHz. Next a length is chosen for one of the lengths, i.e., a length for 
either the monopole element 300, the coaxial element 305, or the 
transmission line element 315. For example, the length l.sub.1 of the 
transmission line element 315 can be chosen to equal one/half (0.5) cm, 
which corresponds to an electrical length, i.e., the length at which the 
transmission line element 315 resonates, of 0.028.lambda. at 930 MHz. In 
this case, applying formula (2) and using l.sub.1 =0.5 cm and 
.lambda.=32.26 cm, it can be seen that the lengths of the transmission 
line element 315, the coaxial element 305, and the monopole element 300 
together are preferably less than or equal to eight (8) cm when m=1. To 
satisfy the condition for resonance, the length of the monopole element 
300 could be chosen to be 3.6 cm, which corresponds to an electrical 
length of 0.111.lambda., and the length of the coaxial element 305 could 
be chosen as 2.4 cm, which corresponds to an electrical length of 
0.111.lambda.. These choices also fulfill the requirements of formulas (3) 
and (4). It will be appreciated that the lengths l.sub.1, l.sub.2, and 
l.sub.3 could have been chosen differently for design reasons and to 
satisfy formula (1) when m is not equal to one. 
Next, formulas (5), (6), and (7) can be used to determine the distance from 
the plating hole 320 of the transmission line element 315 to the terminal 
328 of the transmission line element 315. First, the modified driving 
impedance is calculated to be approximately 1.3.OMEGA.. The length in 
radians is then found to be approximately 0.163 radians. To translate this 
length into centimeters, the wavelength in the transmission line element 
315 is calculated using (10) and (11). Formula (7) can be used as an 
equality to calculate the minimum length l.sub.1 of the transmission line 
element 315. Therefore, a simple ratio can be set up to determine that 
0.163 radians is approximately equal to 0.45 cm, which is the distance 
between the plating hole 320 and the terminal 328. The placement of the 
terminal 328 therefore determines the driving impedance of the receiving 
circuitry 110. 
Additionally, using formula (8), the diameter of the outer conductor 310 
can be calculated to be approximately 0.0875 cm. Using formula (9), the 
width of the transmission line element 315 is calculated to be 
approximately 0.146 cm. 
One of ordinary skill in the art will recognize that the above calculated 
values are only approximations, and that further modifications in the 
dimensions may be necessary to optimize the performance of the antenna 105 
and thereby account for stray capacitances and inductances which are 
difficult to calculate. 
It can be seen that this design for the antenna 105 in accordance with the 
preferred embodiment of the present invention offers a tremendous amount 
of flexibility in selection of the dimensions of the different antenna 
elements. As a result, the antenna 105 can conveniently be utilized for a 
variety of different pager form factors. In particular, the antenna 105 
according to the present invention is especially suitable for use in a 
radio receiver 100 (FIG. 1) manufactured in a pen housing form factor 
because the antenna 105 is rather narrow. 
A further feature of the antenna 105 according to the preferred embodiment 
of the present invention is that the receiver terminal 328 (FIG. 3) of the 
transmission line element 315 can be advantageously located to provide a 
driving impedance which "matches" to the receiving circuitry 110 to 
prevent losses and reflections of the RF signals received by the antenna 
105. Conventionally, matching circuitry, which can consist of a number of 
space-consuming components, is electrically coupled between the antenna 
105 and the receiving circuitry 110. In accordance with the present 
invention, however, this additional matching circuitry is unnecessary 
because the placement of the receiver terminal 328 can simply be changed 
to account for changes in the receiver circuitry 110 input impedance and 
components included therein. Consequently, the cost of conventional 
matching circuitry is saved by using the transmission line element 315. 
Additionally, the length of the transmission line element 315 between the 
coaxial element 305 and the ground terminal, i.e., plated hole 320, can be 
conveniently varied to tune the center frequency of the RF signal received 
by the antenna 105. In general, the variation of the center frequency can 
be accomplished without significantly affecting the driving impedance of 
the receiving circuitry 110. 
Referring next to FIG. 7, an electrical diagram depicts the movement of the 
receiver terminal 328 along the length of the transmission line element 
315 and the variation of the transmission line length. As described above, 
the location of the receiver terminal 328 can be varied to change the 
driving impedance R. One method in which this might be conveniently done 
is to drill multiple plated holes 328, 650 along the length of the 
transmission line element 315. The "most correct" via hole 328 for any 
given frequency could than be chosen by experimentally measuring the 
driving impedance at each of the holes 328, 650. The holes 650 other than 
the one chosen to act as the receiver terminal 328 would be disconnected 
from the receiving circuitry 110 by drilling the metallization from the 
holes 650, thereby opening the connections. 
Additionally, a plurality of plated holes 320, 655, 660 could be formed 
near the end of the transmission line element 315 to couple the 
transmission line element 315 to the ground plane 505. The endmost hole 
660 would be located such that the highest desired frequency received by 
the antenna 105 corresponds to the length of the transmission line element 
315 when coupled to the ground plane 505 at the location of the hole 660. 
When tuning the antenna 105 experimentally, the hole 660 would be opened, 
e.g., by drilling out the metallization, to lower the center frequency of 
the received signal. This process would be repeated until the length of 
the transmission line element 315 is such that the antenna 105 is tuned to 
the desired center frequency by selecting the correct electrical length 
which resonates at the desired frequency. In this manner, both the driving 
impedance and the center frequency can be selectively tuned without 
external tuning components, such as variable capacitors. 
Referring next to FIG. 8, a process flow diagram illustrates a process by 
which the radio receiver 100, including the antenna 105, can be 
manufactured. The initial step in the construction process involves 
exposing a photographic image of the printed circuit board runners and 
pads onto a photo-resist deposited on the printed circuit board 302 (FIG. 
3) by use of a device such as a photolithographic processor 705. The 
transmission line element 315, the pad 324 (FIG. 3), and the terminal 328, 
if desired, are imprinted during this process. The printed circuit board 
302 is manufactured using any one of a number of well known printed 
circuit board materials, such as FR-4 (a flame retardant classification) 
or a glass epoxy material. Other materials, including those with higher 
dielectric constants, can be utilized as well. 
Next, the imprinted board 302 is preferably processed by etching equipment 
710 to etch metallization from the board 302 as indicated by the printing 
thereon. This process selectively removes metallization from the board 302 
to form the transmission line element 315, the pad 324, the terminal 328, 
if necessary, and other printed circuitry. Subsequently, a drill press 715 
is employed to drill holes, such as the holes 320, 326 (FIG. 3), through 
the board 302 in designated locations, after which a screen printer 720 
selective laminates the board 302 to apply a non-conductive material, such 
as solder resist, thereon. During this process, selected metallized areas, 
for example, holes 320, 326, the pad 326, and the area of the transmission 
line element 315 to which the inner conductor 307 is to be soldered, are 
not laminated. The exposed metallized areas of the board 302 are 
thereafter plated with a conductive material in a plating tank 725. In 
this manner, different areas of the printed circuit board 302 which are 
connected by the drilled holes can be electrically coupled by the plating 
which flows therethrough. 
When the receiving circuitry 110 is to be mounted on the board 302 in an 
automated process, the board 302 is next processed by placement equipment 
730 for automatically placing receiving components on the appropriate 
component pads, which have been exposed to the plating. A reflow over 735 
is them employed to apply heat to the board 302 to reflow the 
metallization between the receiver components and the component pads, 
thereby securing the receiving circuitry 110 to the board 302. 
Subsequently, the board 302 is processed in post-reflow processes 740, in 
which components not suitable for reflow are attached to the board 302. 
During this process, the monopole element 300 and the coaxial element 305, 
which could have been previously constructed in an antenna manufacturing 
process 745, are soldered to the transmission line element 315 at the end 
of the inner conductor 307. Additionally, the ground strap 322, which, if 
necessary to the antenna design, has been previously manufactured in a 
forming and cutting process 750, is soldered to the pad 324 and the outer 
conductor 310 of the coaxial element 305. 
In summary, the antenna as described above comprises three elongated 
elements formed along a single axis. Therefore, the antenna is especially 
suitable for use in narrow form factor radio receiver housings, such as 
pen form factor pagers, having tight space constraints. Additionally, a 
third of the elongated elements, i.e., the transmission line element, can 
be formed directly on a printed circuit board to which receiving circuitry 
is mounted. Consequently, this element is not separately manufactured, 
stocked, or assembled, which reduces the cost of the radio receiver. 
This transmission line element, furthermore, conveniently performs the 
function of a conventional matching network. More specifically, the 
transmission line element is coupled to other antenna elements at one end 
and to the ground plane at the other end. A terminal formed between the 
two ends couples to the receiving circuitry for providing the RF signals 
thereto. The placement of this terminal advantageously determines the 
driving impedance of the receiving circuitry. As a result, for different 
receiving circuitry and components, the terminal can simply be relocated 
to match to the receiving circuitry and provide optimum receiver 
performance, and space-consuming conventional matching components are 
eliminated. 
Additionally, the frequency of the received RF signal can be adjusted, or 
tuned, by simply increasing or decreasing the length of the transmission 
line element. Provisions for the tuning of the antenna can be conveniently 
made during manufacture of the antenna by drilling a plurality of via 
holes from the transmission line element to ground. The holes can simply 
be opened to adjust the length of the transmission line element, and thus 
the frequency of the received signals. 
It may be appreciated by now that there has been provided an antenna which 
functions electrically in various paging form factors. The antenna 
eliminates the need for conventional matching and tuning circuitry as well 
.