Wristwatch-type selective calling receiver

A selective calling receiver comprising a receiver, a first band, and a second band, the first and the second bands being connected to the receiver at both sides,

• the first band comprising:
• a first antenna extending longitudinally and being electrically connected to the receiver, the first antenna comprising a plurality of points providing different effective antenna lengths, respectively;
• a plurality of stoppers arrayed in the longitudinal direction on the outer surface of the first band, said stoppers each comprising a recess formed in the outer surface of the first band so as not to penetrate through the first band, each of the recesses having an electrode provided therein;
• and
• a plurality of tuning capacitors electrically connected between the electrodes and the points of the first antenna, respectively, for maintaining a tuning frequency at a predetermined frequency regardless of the differences in effective antenna length of the first antenna, and
• the second band comprising:
• a second antenna electrically connected to the receiver;
• and
• a conductive hook electrically connected to said second antenna, said hook being engaged within one of the recesses to electrically contact the electrode within said one of the recesses, and to connect the first band and the second band in a ring form.

A selective calling receiver comprising a receiver having a variable capacitor, a first band, and a second band, the first and the second bands being connected to the receiver at both sides,

• the first band comprising:
• a first antenna extending longitudinally and being electrically connected to the receiver, the first antenna comprising a plurality of points providing different effective antenna lengths, respectively;
• a plurality of stoppers arrayed in the longitudinal direction on the outer surface of the first band, each of the stoppers having an electrode provided therein;
• and
• a plurality of tuning capacitors electrically connected between the electrodes and the points of the first antenna, respectively, for maintaining a tuning frequency at a predetermined frequency regardless of the differences in effective antenna length of the first antenna, and
• the second band comprising:
• a second antenna electrically connected to the receiver;
• and
• a hook capable of being engaged with one of the stoppers to connect the first band and the second band in a ring form, the hook comprising a conductor provided at a predetermined location of the second band and electrically connected to the second antenna, and the conductor being in electrical contact with the electrode in a selected one of the stoppers, wherein the capacitances Cx of the tuning capacitors are set to satisfy the following equation:
• f1=f2=1/2.pi.*[{L4+L3-(n-1)*Ls}{C11+Cx{].sup.-0.5
• where f1 is a transmission frequency of a paging system, f2 is a tuning frequency of the receiver, C11 is a capacitance of the variable capacitor of the receiver, L3 is an inductance of the first antenna from a connecting point between the first and second bands to the variable capacitor and from the connecting point to a capacitor farthest from the receiver along the first band, L4 is an inductance of the second antenna and the hook, Ls is an inductance of a section of the first antenna between adjacent ones of the tuning capacitors, and n equals the total number of tuning capacitors minus the number of tuning capacitors between the connecting point and the receiver along the first band.