US 5,475,677 A · Compatible licensed and unlicensed band portable handset unit for TDMA wireless communications system

In a TDM/TDMA digital telephony system having a plurality of fixed ports and a plurality of mobile portable handsets, each of said ports having a transmitter for transmitting a downlink burst signal at one of a plurality of downlink frequencies to at least one portable handset and a receiver for receiving an uplink burst signal at one of a plurality of associated uplink frequencies from at least one of said portable handsets, some of said plurality of ports operating in a frequency-division duplex (FDD) mode in a licensed frequency spectrum in which the downlink frequencies and uplink frequencies are in different predetermined frequency bands and each downlink frequency and associated uplink frequency are separated by a predetermined frequency difference, and others of said ports operating in a time-division duplex (TDD) mode in an unlicensed frequency spectrum in which a downlink frequency and its associated uplink frequency are the same and a downlink burst and an uplink burst are received and transmitted in different time-slots of a frame, a portable handset that is compatible for operation in an FDD mode for communicating with those ports operating in the FDD mode in the licensed frequency spectrum and in the TDD mode for communicating with those ports operating in the TDD mode in the unlicensed frequency spectrum, the compatible portable handset comprising:

frequency synthesizer means for producing a synthesizer signal at a frequency determined by a control signal;
down-converting means for down-converting the downlink frequency of a received downlink burst signal to a first predetermined intermediate frequency (IF) by mixing it with said synthesizer signal;
receiver circuit means comprising means for converting the down-converted downlink burst signal at said first predetermined IF to a baseband signal, means for demodulating the baseband signal, and means for decoding the demodulated baseband signal;
transmitter circuit means comprising means for encoding a signal to be transmitted, means for modulating to a baseband signal the encoded signal to be transmitted, and means for converting the baseband signal to be transmitted to a signal having a second predetermined IF;
the difference in frequency between said first predetermined IF and said second predetermined IF being equal to said predetermined frequency difference;
up-converting means for up-converting the second predetermined IF of the signal to be transmitted to an uplink frequency associated with the downlink frequency by mixing it with said synthesizer signal;
and
control means for determining whether the portable handset is operating in an FDD or TDD mode and for generating said control signal, said synthesizer being maintained by said control signal at the same frequency for both down-converting the downlink frequency to said first predetermined IF and for up-converting said second predetermined IF to said uplink frequency to keep the separation in frequency between said uplink and downlink frequencies at said predetermined frequency difference when said portable handset is in the FDD mode, and in response to said control signal said synthesizer being switched in frequency between down-coverting the downlink frequency to said first predetermined IF and up-converting the second predetermined IF signal to said uplink frequency in between the different time-slots in each frame to keep said uplink and downlink frequencies the same when said portable handset is in the TDD mode.

5 more elements

In a TDM/TDMA digital telephony system having a plurality of fixed ports and a plurality of mobile portable handsets, each of the ports having a transmitter for transmitting a downlink burst signal at one of a plurality of downlink frequencies to at least one portable handset and a receiver for receiving an uplink burst signal at one of a plurality of associated uplink frequencies from at least one of the portable handsets, some of the plurality of ports operating in a frequency-division duplex (FDD) mode in a licensed frequency spectrum in which the downlink frequencies and uplink frequencies are in different predetermined frequency bands and each downlink frequency and associated uplink frequency are separated by a predetermined frequency difference, and others of the ports operating in a time-division duplex (TDD) mode in an unlicensed frequency spectrum in which a downlink frequency and its associated uplink frequency are the same and a downlink burst and an uplink burst are received and transmitted in different time-slots of a frame, a method for compatibly operating a portable handset in an FDD mode for communicating with those ports operating in the FDD mode in the licensed frequency spectrum and in the TDD mode for communicating with those ports operating in the TDD mode in the unlicensed frequency spectrum, the method comprising the steps of:

producing a synthesizer signal at a frequency determined by a control signal;
down-converting the downlink frequency of a received downlink burst signal to a first predetermined intermediate frequency (IF) by mixing it with the synthesizer signal;
converting the down-converted downlink burst signal at the first predetermined IF to a baseband signal, demodulating the baseband signal, and decoding the demodulated baseband signal;
encoding a signal to be transmitted, modulating to a baseband signal the encoded signal to be transmitted, and converting the baseband signal to be transmitted to a signal having a second predetermined IF;
the difference in frequency between the first predetermined IF and the second predetermined 1F being equal to the predetermined frequency difference;
up-converting the second predetermined IF of the signal to be transmitted to an uplink frequency associated with the downlink frequency by mixing it with the synthesizer signal;
and
determining whether the portable handset is operating in an FDD or TDD mode and for generating the control signal, the control signal maintaining the frequency of the synthesizer signal at the same frequency for both down-converting the downlink frequency to the first predetermined IF and for up-converting the second predetermined IF to the uplink frequency to keep the separation in frequency between the uplink and downlink frequencies at the predetermined frequency difference when the portable handset is in the FDD mode, and switching the frequency of the synthesize signal in response to the control signal between down-coverting the downlink frequency to the first predetermined IF and up-converting the second predetermined IF signal to the uplink frequency between the different time-slots in each frame to keep the uplink and downlink frequencies the same when the portable handset is in the TDD mode.

5 more elements

A portable handset for use in a TDM/TDMA digital telephony system that operates in either a frequency-division duplex (FDD) mode in which the portable handset transmits an uplink signal and receives a downlink signal on uplink and downlink carrier frequencies, respectively, that are separated by a predetermined frequency difference, or in a time-division duplex (TDD) mode in which the portable handset transmits an uplink signal and receives a downlink signal on different time-slots at the same uplink and downlink carrier frequency, the portable handset comprising:

a transmitter having an associated first predetermined intermediate frequency (IF);
a receiver having an associated second predetermined IF, said first and second IFs being separated by said predetermined frequency difference;
frequency synthesizer means for producing a synthesizer signal having an adjustable frequency;
means for up-converting said first predetermined IF to said uplink carrier frequency by mixing it with said synthesizer signal;
means for down-converting said downlink carrier frequency to said second predetermined IF by mixing it with said synthesizer signal;
means for keeping said synthesizer signal at the same frequency for both transmitting the uplink signal and receiving the downlink signal when the portable handset is in the FDD mode, and for switching the frequency of said synthesizer signal between transmitting the uplink signal and receiving the downlink signal when the portable handset is in the TDD mode.

3 more elements

In a TDM/TDMA digital telephony system, a method of operating a portable handset in either a frequency-division duplex (FDD) mode in which the portable handset transmits an uplink signal and receives a downlink signal on uplink and downlink carrier frequencies, respectively, that are separated by a predetermined frequency difference, or in a time-division duplex (TDD) mode in which the portable handset transmits an uplink signal and receives a downlink signal on different time-slots at the same uplink and downlink carrier frequency, the method comprising the steps of:

producing a synthesizer signal having an adjustable frequency;
down-converting the downlink carrier frequency of the downlink signal to a first predetermined intermediate frequency (IF) by mixing it with the synthesizer signal;
up-converting a second predetermined IF to the uplink carrier frequency for transmitting the uplink signal by mixing it with the synthesizer signal, the first and second predetermined IFs being separated by said predetermined frequency difference;
keeping the synthesizer signal at the same frequency for both transmitting the uplink signal and receiving the downlink signal when the portable handset is in the FDD mode, and switching the frequency of the synthesizer signal between transmitting the uplink signal and receiving the downlink signal when the portable handset is in the TDD mode.

1 more element

Compatible licensed and unlicensed band portable handset unit for TDMA wireless communications system

Life of this patent

Compatible licensed and unlicensed band portable handset unit for TDMA wireless communications system

Life of this patent

Abstract

Claims14