Telecommunications – Transmitter – Having harmonic radiation suppression
Reexamination Certificate
1998-02-24
2001-04-03
Nguyen, Lee (Department: 2746)
Telecommunications
Transmitter
Having harmonic radiation suppression
C455S073000, C455S078000, C455S115200, C455S120000, C455S126000
Reexamination Certificate
active
06212367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile phone apparatus.
2. Description of the Prior Art
A known type of mobile phone transmits and receives on separate frequencies in the UHF (Ultra High Frequency) band. Such phones are used in the TDMA [Time Division Multiple Access] (GSM [Global System for Mobile communication]) systems, for which there are stringent specifications on the amount of transmitter noise which falls within the receiver band. A known technique for meeting this specification uses a high Q (quality factor) notch filter at the output of the power amplifier of the phone transmitter. However, such a filter is relatively large and has a significant insertion loss. In order to compensate for this loss, the power amplifier has to provide a higher output power and therefore draws a higher current from the power supply, which is normally a battery within the phone. Thus, for a given size of battery, the talk time of the phone is reduced.
In another known type of phone, a phase locked loop is connected between a modulator which produces a signal to be transmitted in the transmit band and the power amplifier of the phone. The modulator output is connected to an input of the phase sensitive detector of the phase locked loop and the input of the power amplifier is connected to the voltage controlled oscillator of the loop. The wide band noise of the transmitter signal supplied to the power amplifier is then determined by the phase noise of the voltage controlled oscillator when the loop is locked. However, low phase noise voltage controlled oscillators for operation at UHF are relatively expensive.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a mobile phone apparatus which is capable of meeting the stringent specifications on transmitter noise in the receive band.
The object of the present invention is achieved by a mobile phone apparatus comprising a modulator for producing a signal to be transmitted in a transmit band, a power amplifier for supplying the signal to be transmitted to an aerial, a tunable filter disposed between the modulator and the power amplifier and having a passband and an attenuation band, and a control circuit for tuning the filter such that the passband is at the transmit band and the attenuation band is at a receive band of the apparatus.
According to the present invention, none of the power amplifier output is lost so that talk time is not substantially affected. A relatively simple and inexpensive circuit may be used so that the cost of the apparatus is not substantially affected.
The above and other objects, features and advantages of the present invention will become apparent from the following description referring to the accompanying drawings which illustrate an example of a preferred embodiment of the present invention.
REFERENCES:
patent: 4422047 (1983-12-01), Wright
patent: 4618997 (1986-10-01), Imazeki et al.
patent: 5239686 (1993-08-01), Downey
patent: 5448769 (1995-09-01), Jantti
patent: 2092845 (1982-08-01), None
patent: 2276293 (1994-09-01), None
NEC Corporation
Nguyen Lee
Sughrue Mion Zinn Macpeak & Seas, PLLC
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