Abstract: The present invention achieves power savings by turning off all or some of the baseband processing for codes and timeslots that have not been transmitted due to full or partial DTX. With respect to partial DTX, the transmitted codes and associated timeslots and radio frames within the shortest TTI in the CCTrCH are determined from the received TFCI. Thereafter, the receiver is turned off for the unused codes as indicated by the received TFCI. With respect to full DTX, following TFCI reception, the receiver is turned off for all timeslots within the shortest TTI.

Abstract: Method and apparatus for interference signal code power noise variance estimation employing a reduced number of samples utilizing the equation 1 σ ^ n 2 = T · ∑ i = 1 N sample ⁢ &LeftBracketingBar; h n ⁢ ( i ) &RightBracketingBar; 2 ,

Abstract: A method of for canceling echos at a first end of a telephone call marks every other byte of a first digital representation of a first analog signal originating at the first end of the call with a signature. A second digital representation of a second analog signal from the second end of the call is received at the first end and split into a stream of odd number bytes and a stream of even number bytes. The streams of bytes are analyzed for the presence of the signature and one of the streams of bytes is converted to a third analog signal if the signature is detected.

Abstract: A portable programming device is used in a supervisory remote control system comprising a signal transmission unit for supplying a signal according to a TDM (Time Division Multiplexing) manner, first and second terminals having individual addresses, and a signal line connecting therebetween. According to a set of relation data including an address correspondence between one of the second terminals and one of the first terminals and control data including control parameters of a load, the load connected to the one of the second terminals can be controlled according to a supervisory input provided to the one of the first terminals.

Abstract: A method and apparatus for Time Division Duplex (TDD) synchronization of Access Points (APEs) uses the 1 pulse-per-second timing pulses of the Global Positioning System (GPS) and synchronization state machines for its Time Division Multiple Access (TDMA) structure. As a result, the present invention obviates the need for expensive voltage-controlled oscillators used by the prior art, and achieves stable timing accuracy within approximately 7.5 minutes, as opposed to the 12 to 24-hour period needed by prior art methods.

Abstract: A TTD system implements dynamic link adaptation by adding or changing control information to notify the receiver which timeslots and codes are currently active and which timeslots should be avoided. The system synchronizes the transmitter and the receiver such that the receiver knows which timeslots and codes the transmitter has used to map the coded composite transport channel onto physical channels. The system attempts to avoid the timeslots which are experiencing transmission difficulties, while attempting to utilize the timeslots which are not experiencing transmission problems.

Abstract: When a main device 1 detects an incoming message, the main device 1 transmits a call frame to auxiliary devices 2, 3 during a first time slot of a first cycle. In succession with this, the auxiliary-device 2 transmits a ready frame in a slot 2 to notify main devices of other systems that the communication channel is being used. Neither of the auxiliary devices 2, 3 respond in the third time slot. The same transmission and reception processes are performed in the second cycle. However, afterward in the third cycle, the auxiliary device 2 is brought into an off-hook condition and so transmits an off-hook frame during the third time slot of the third cycle. The main device 1 receives the off-hook frame and transmits a connect frame in the first time slot of the fourth cycle to the auxiliary device 2. In response, the auxiliary device 2 starts communication.

Abstract: In the data transmission system according to the present invention, a master apparatus transmits data to a plurality of slave apparatuses during a time block T1-1 and the individual slave apparatuses transmit data for the master apparatus during a time block T1-3. Slave apparatus control signals transmitted by the master apparatus for the individual slave apparatuses are transmitted through a control channel group 31 having time slots that correspond to the individual slave apparatuses, whereas master apparatus control signals for the master apparatus transmitted by the individual slave apparatuses are transmitted through a control channel group 35 having time slots that correspond to the individual slave apparatuses.

Abstract: Techniques to process data for transmission in a time division duplexed (TDD) communication system. In one aspect, the frequency response of a forward link is estimated at a base station based on reverse link transmissions (e.g., pilots) from a terminal. Prior to a data transmission on the forward link, the base station determines a reverse transfer function based on the pilots transmitted by the terminal, “calibrates” the reverse transfer function with a calibration function to derive an estimate of a forward transfer function, and preconditions modulation symbols based on weights derived from the forward transfer function. In another aspect, the terminal estimates the “quality” of the forward link and provides this information to the base station. The base station then uses the information to properly code and modulate data prior to transmission such that the transmitted data can be received by the terminal at the desired level of performance.

Abstract: The present invention provides a subscriber device (10), method (1000, 1500), wireless router (30), and communication system (100). The communication system (100) includes at least one subscriber device (10) having a message generator (1612) for generating a message which includes an indicator of a receive/transmit switching time, and the wireless router (30) for communicating with at least one subscriber device, the wireless router having a scheduler (902), optimizer (904), and an allocation map generator (906), wherein the wireless router (30) prepares an efficient and optimized channel allocation map for transmission to the subscriber device (10) taking into account the indicator of the receive/transmit switching time for the subscriber device (10) and wherein the map indicates at least one allocated transmit time, in a form of a block, having a beginning and an end, for transmission by the subscriber device following a receive time.

Abstract: Signals are transmitted through a plurality of transmission channels, each including at least a pair of signal lines for transmitting an interface signal, between a transmitter and a receiver. A predetermined signal is modulated by a modulator with a high-frequency signal, and the modulated signal is provided to a signal line of one of the plurality of transmission channels. A demodulator receives the modulated signal transmitted via this signal line, and demodulates the modulated signal from the signal line based on the frequency of the high-frequency signal. According to the above-described configuration, an interface control method and apparatus which can newly exchange other data and control signals while conforming to existent interface specifications are provided.

Abstract: Improved approaches to provide flexibility in setting user data rates and managing delay in data transmission systems using a superframe structure and Time Division Duplexing (TDD) are disclosed. These improved approaches operate to provide intelligent insertion of dummy words (bits or bites) into a data stream to be transmitted. By inserting the dummy words, the invention is able to render codewords, symbols and superframes independent from user data rates. As a result, a wide range of user data rates are available in data transmission systems using a superframe and TDD.

Abstract: The present invention discloses a method by which a new Bluetooth piconet is established amongst participants of an old Bluetooth piconet whose master has disappeared. After determining that the master has disappeared, one of the slaves is selected to take the function of the master and reestablishes communications at the Baseband layer by contacting each of the other participants. Further, the present invention discloses a method and an associated device for realizing point-to-multipoint communications using a Bluetooth piconet by using an application adaptation layer and a local addressing list. Also, the present invention discloses a method by which point-to-multipoint communications by an application using a Bluetooth piconet is reestablished amongst participants of an old Bluetooth piconet whose master has disappeared.

Abstract: Disclosed is a simplex/duplex switching system which can easily cope with a simplex configuration or a duplex configuration. The simplex/duplex switching system includes a first device for outputting a predetermined frame signal carrying a plurality of time slot signals; and multiple second devices, each of which is paired with another device having the same structure, wherein, when paired second devices serve together as a simplex device, each of the second devices alternately receives the time slot signals included in the predetermined frame signal; and wherein, when paired second devices serve together as a duplex device, both of the second devices receive all of the time slot signals included in the predetermined frame signal.

Abstract: There is disclosed a radio frequency (RF) modem shelf for use in a fixed wireless access network comprising a plurality of base stations capable of bidirectional time division duplex (TDD) communication with wireless access devices disposed at a plurality of subscriber premises. The radio frequency (RF) modem shelf comprises: a) a first RF modem for communicating with a plurality of the wireless access devices using TDD frames, each TDD frame having an uplink for receiving data and a downlink for transmitting data; and b) a modulation controller associated with the RF modem shelf for determining an optimum modulation configuration for each of the plurality of wireless access devices communicating with the first RF modem.

Abstract: A transceiver for use in a wireless access network comprising a plurality of base stations, each of the plurality of base stations capable of bidirectional time division duplex (TDD) communication with wireless access devices disposed at a plurality of subscriber premises in a corresponding cell site of the wireless access network. The transceiver is associated with a first base station and comprises transmit path circuitry associated with a beam forming network for transmitting directed scanning beam signals in a sector of a cell site of the first base station. The transmit path circuitry transmits at a start of a TDD frame a broadcast beam signal comprising a start of frame field and subsequently transmits downlink data traffic in a downlink portion of the TDD frame to at least one of the wireless access devices using at least one directed scanning beam.

Abstract: A single voltage controlled oscillator (VCO) running at a closed loop controlled fundamental frequency whereby the harmonic products generated by the VCO are used for both transmission and reception. The use of a single VCO and associated supporting circuitry for both transmit and receive portions of the circuit serves to reduce the cost of the transceiver. The radio transceiver comprises a single synthesized oscillator having high harmonic content. The frequency conversions in the receiver make use of the harmonic frequency components of the same oscillator used in performing modulation during transmission.

Abstract: A digital transmission system comprises a plurality of wire, sets (151, 155), such as twisted-pair wires for delivering services to subscribers (110, 120, 130, 140). A first wire set (151) carries a time-division duplexed multitone signal VDSL. The system is arranged to individually select the transmitted spectra of the upstream and downstream portions of the duplexed signal so as to minimise cross-talk interference with further signals ADSL, HDSL carried by other wire sets (155). In use, the transmitted spectra of the upstream and downstream portions of the duplexed signal may differ in bandwidth.

Abstract: A method for phase encoding DPSK and N-PSK which maintains phase continuity and which does not require any reference symbols when using N-PSK. A sequence of known DPSK phases are encoded with respect to an initial phase. The N-PSK phases are then all offset by this same initial phase. The known DPSK phases can be used at a receiver to determine a sum consisting of the initial phase and any further phase shift introduced by the channel, and this sum is used to decode the unknown N-PSK phases. The method is more generally applicable to any case where a switch between a phase encoding method which requires an absolute phase reference and a phase encoding method which does not have an absolute phase reference is to be implemented on a single carrier or channel.

Abstract: Concerned is time slot allocation in the CDMA-TDD scheme. A time slot of an uplink (UL) is allocated to a mobile station MS1 in cell 1. At this time, a time slot of a downlink (DL) having the same time slot number as that of the foregoing time slot is allocated to a mobile station MS2 in an adjacent cell 2 without avoiding the allocation. If there can occur deterioration of communication quality a process of allocating another time slot or the like will be performed as in the case of a mobile station MS2-1.

Abstract: A satellite communication system uses dual satellite coverage techniques to simulate the provision of full duplex communications in the system. Each subscriber (100) in the system communicates with two satellites (102, 104) that use complementary time division duplex (TDD) frame structures (50, 72) for communicating with the subscriber (100). In one embodiment, each satellite in the system performs a transition between a first TDD frame structure (50) and a second TDD frame structure (72) while travelling through a transition region (102) of an associated orbit (130). Preferably, the transition is performed gradually so that an abrupt reduction in system capacity is avoided. In another embodiment, individual orbital planes in the satellite system are dedicated for use with particular TDD frame structures. A subscriber thus communicates with one satellite in each of two planes during a connection.

Abstract: A mobile station receives a signal based on a TDD method by receiving a signal based on a FDD method to acquire information of the signal based on the TDD method in a mobile communication system. For instance, the mobile station receives a signal based on a CDMA-FDD method. Then, the mobile station acquires information (e.g. information relating to a code, a frequency and a timing) of a signal based on a CDMA-TDD method from the signal based on the CDMA-FDD method. Then, the mobile station receives the signal based on the CDMA-TDD method on the basis of the acquired information.

Abstract: To better utilize the variable bandwidth of wireless links, a network node in accordance with the present invention escapes rigid bandwidth hierarchy of conventional TDM protocols, which is not suited for fully using the available bandwidth of a wireless link. Specifically, many embodiments of the present invention use TDM frames that have payloads, which do not strictly conform to the bandwidth hierarchy of conventional TDM protocols. For example, many embodiments of the present invention form TDM frames having a payload that is a non-integer multiple of a base bandwidth, such as OC-1/STS-1.

Abstract: In a mobile station apparatus and a base station apparatus in a digital mobile communication using a TDD system and a CDMA system, in the case where there is a difference in communication qualities between a revere link and a forward Link, a burst length of a communication link with lower quality can be made longer than a burst length of a communication link with higher quality. That makes it possible to communicate more signals in the communication link with low communication quality than in the communication link with high communication quality, which allows the equal communication qualities in the reverse link and the forward link.

Abstract: A method and an apparatus provide for controlled access to a shared communication medium. Time slots on a forward channel include information regarding status useful for remote units to determine whether a reverse channel is available for seizure. Additionally, information along the forward channel provides guidance to the remote units to control attempts to seize the reverse channel. In one embodiment a remote unit divides a data package into a plurality of portions and attempts to seize the reverse channel using a single portion of the data package which corresponds to one time slot on the reverse channel. It then waits until it receives notification along the forward channel that the first data portion was successfully received before it attempts to send any of the remainder of its data in consecutive time slots on the reverse channel.

Abstract: A peak limiter is intended to limit the peak of a signal that has a given frequency, in an assembly comprising other signals of lower amplitude and different frequencies. The peak limiter includes a circulator inserted into a line transporting all the signals. A first branch of the circulator is connected to a line on its upstream side. Its second branch is connected to a line on its downstream side. It's third branch is connected to a reference terminal via the combination of a band-pass filter centered on the given frequency, a threshold element, and an adapted load connected in series.

Abstract: The present invention concerns a method of transmitting a synchronization signal during a synchronization time slot of a system for telecommunication by mobile stations of the time division duplex (TDD) type where the data are transmitted in frames consisting of time slots, the said synchronization signal including a synchronization sequence.

Abstract: In a network that roughly comprises a temporary master station and a plurality of slave stations and is an adhoc network, which can be immediately constructed in situ, and is a temporary master station interposition-type network in which a temporary master station is present, the temporary master station receives and judges an interference detection packet sent from the slave station. By virtue of this construction, an asynchronous interference avoiding method and an asynchronous interference avoiding system can be realized which can reliably avoid interference.

Abstract: A portable game controller for operating an electronic game device. The controller communicates between a person and the game device with a radio frequency sender and receiver. Signal transmission is communicated over the same channel with time domain multiplexing, and can be sent over one or more channels to expand the number of controllers operable in a system. Signal transmission can be delivered in short intervals to conserve battery power. Multiple persons can deliver signals through multiple senders or through a common radio frequency sender, and signals can be transmitted from the radio frequency receiver to the radio frequency sender.

Abstract: A single transmitter transmits K communication bursts in a shared spectrum in a time slot of a time division duplex communication system. The system associated with N midamble sequences. Each burst has an associated midamble sequence. A receiver receives a vector corresponding to the transmitted midamble sequences of the K communication bursts. A matrix having N identical right circulant matrix blocks is constructed based in part on the known N midamble sequences. The wireless channel between the transmitter and receiver is estimated based on in part one of the N blocks and the received vector.

Abstract: A system is described comprising: a finite state machine having a plurality of states interconnected through a plurality of events, wherein certain states and events in said plurality are implemented in software and other states and events in said plurality are implemented in hardware; and a scheduler communicatively coupled to the finite state machine and being programmable with one or more parameters defining scheduled operations to be performed by the scheduler, wherein the finite state machine is configured to select one or more of said parameters to be used by said scheduler upon transition by said finite state machine from a first state to a second state.

Abstract: In a control device for a storage device in which data streams are respectively divided into unit data, which are distributed to storage parts and are sequentially read therefrom for every unit data, there is provided a buffer memory which stores data to be written into the storage parts and data read from the storage parts. An input/output control part causes the unit data from the storage parts in an access cycle corresponding to a bit rate to be stored in the buffer memory and causes the unit data stored in the buffer memory at the bit rate to be written into the storage parts. An input/output interface part reads the unit data from the buffer memory at the bit rate and causes the data transferred at the bit rate to be stored in the buffer memory.

Abstract: A time division multiplexed wireless communication system using the DECT protocol with spread-spectrum modulation. The wireless communication system includes a spread-spectrum transmitter and receiver. The spread spectrum transmitter transmits using an M-ary spread spectrum transmission technique, sending a predefined chip code (symbol code) for each data symbol. The predefined chip codes used are relatively short, so that spread spectrum synchronization is accomplished within about a single data symbol transmission time, well within the constraints of the DECT timing structure. The spread spectrum signal may be transmitted over a bandwidth of under 20 MHz (e.g., about 5 MHz) covering a plurality of DECT frequency channels, so as to be confined within, or overlapping with, the bandwidth of a DECT system, and so as to minimize interference with other users, if any, of the same frequency spectrum.

Abstract: A power efficient and reduced electromagnetic interference (EMI) emissions transmitter for unshielded twisted pair (UTP) data communication applications. Transmit data is processed by a digital filter. The digital filter output data is converted to a current-mode analog waveform by a digital-to-analog converter (DAC). The digital filter is integrated with the DAC binary decoder in a memory device such as a ROM with time multiplexed output. DAC line driver cells are adaptively configurable to operate in either a class-A or a class-B mode depending on the desired operational modality. A discrete-time analog filter is integrated with the DAC line driver to provide additional EMI emissions suppression. An adaptive electronic transmission signal cancellation circuit separates transmit data from receive data in a bidirectional communication system operating in full duplex mode.

Abstract: A method for allocating control time slots to terminals in a multipoint system based on time-division data transmission. Specific grant numbers are allocated to the terminals in downstream time slots. One grant number is associated with a grant to send information, such as one ATM cell, in corresponding upstream time slots. The terminal may be forbidden by means of a grant number to send in a certain time slot, or the time slot may be called a slotted Aloha time slot or a measurement time slot used for timing advance adjustment. The network terminal sends grant numbers at a predetermined rate to each terminal or sends grant numbers on the basis of how much information the terminals report needs to be sent. ATM channels are accessed rapidly and allocated efficiently, and a short access delay for a speech channel is achieved.

Abstract: A TDD digital radio communication system includes a local oscillator for generating a local oscillation frequency being N times the transmission intermediate frequency and a frequency divider for dividing the local oscillation frequency by N. The frequency divider is enabled in the transmission mode to generate the transmission intermediate frequency and is disabled in the reception mode to completely stop generating the transmission intermediate frequency, so as to prevent interference with the reception intermediate frequency.

Abstract: This invention relates to duplex and to half duplex transmission schemes and more particularly to the application of such schemes in TDMA and other multiple access environments. In accordance with a first aspect of the invention, there is provided a method of multiplexing signals transmitted by a number of terminals onto a communications link; the link having a capacity less than the total capacity of the terminals; the method including the step of varying the rate of encoding of said signals transmitted by said terminals whereby the bandwidth o the transmitted signals corresponds to the portions allocated to the terminals. In accordance with another aspect of the invention, there is provided a system for the communication of signals in real time over a channel; said system adapted to vary the bandwidth of at least one signal such that the number of signals multiplexed onto said channel can be dynamically varied.

Abstract: A multi-carrier transmission system, particularly a discrete multi-tone (DMT) system. Data is transmitted between two transceivers using a plurality of carriers. The frequency bandwidth of the system is divided between the plurality of carriers. The transmission system is adapted for operation in a heterogeneous network including a number of subscriber equipments having different channel characteristics and coexisting on the same cable. The length of cable for each subscriber terminal varies in relation to its respective location. The transmission system includes an allocation device for allocating the traffic of subscriber equipments having a shorter length of cable to tones starting from a higher frequency band of the system bandwidth.

Abstract: An enhanced radio telephone providing both wireless communication and Internet-protocol (IP) telephone communication. In addition to transmitting and receiving digitized and coded speech signals in a wireless fashion using a radio transceiver, the enhanced radio telephone can also exchange coded speech data with a computer which is coupled to a communication network. Thus, the enhanced radio telephone can selectively operate as either a conventional radio telephone or as an improved IP telephone. The enhanced radio telephone includes an internal speech coder which is implemented for low power consumption and which allows the enhanced radio telephone to be used with a relatively low-cost computer for effective and economic IP telephony.In exemplary embodiments, an enhanced radio handset is connected to an input/output port of a personal computer running a software telephony application.

Abstract: A mobile communication system transmitting data in frame unit includes a base station apparatus and a terminal apparatus. The transmitter has a controller having consecutive first and second frames each divided into a first interval and a second interval following the first interval. In a handoff mode, the controller transmits respective frame data in the first interval of the first frame and the second interval of the second frame and stops transmission of the data in the second interval of the first frame and the first interval of the second frame. Further, the terminal apparatus (i.e.

Abstract: A method of demodulating voice or data and control information in systems that support multiple modulation schemes modulates voice or data using a first linear modulation scheme, such as 16QAM modulation scheme, and modulates control information using a second linear modulation scheme, for example, QPSK modulation scheme, that has the same symbol rate as that of the first modulation scheme. The first linear modulation scheme has a higher modulation level than the second linear modulation scheme. Information modulated using the second linear modulation scheme, which uses a reduced signal set of the first linear modulation scheme, are demodulated using the same demodulator that is used for demodulating information modulated using the first linear modulation scheme. Also, in-band signalling information within a traffic channel, such as stealing flags, are modulated using the second modulation scheme.

Abstract: The present invention provides a subscriber device (10), method (1000, 1500), wireless router (30), and communication system (100). The communication system (100) includes at least one subscriber device (10) having a message generator (1612) for generating a message which includes an indicator of a receive/transmit switching time, and the wireless router (30) for communicating with at least one subscriber device, the wireless router having a scheduler (902), optimizer (904), and an allocation map generator (906), wherein the wireless router (30) prepares an efficient and optimized channel allocation map for transmission to the subscriber device (10) taking into account the indicator of the receive/transmit switching time for the subscriber device (10) and wherein the map indicates at least one allocated transmit time, in a form of a block, having a beginning and an end, for transmission by the subscriber device following a receive time.

Abstract: A transmitter/receiver for use in a multichannel time division duplexing system having an independent combiner and divider to isolate a transmission channel from a reception channel. The transmitter/receiver includes a first and second circulator connected, respectively, to a first and second transceiver. A transmission channel, formed between the first and second circulators and an antenna, transfers transmission signals from the first and second transceivers to the antenna in response to a transmission enable signal. A reception channel, formed between the first and second circulators and the antenna, transfers a reception signal from the antenna to the first and second transceiver in response to a reception enable signal. A switching control circuit is provided for generating the transmission enable signal during a transmission mode of operation and for generating the reception enable signal during a reception mode of operation.

Abstract: In order to increase the range of a repeater in a DECT-TDMA system without shortening the time spacing between transmission and reception time-slots (TX, RX), the transmission time-slots (TX) with mobile part functionality (MT) are delayed in time by a bit plurality t.

Abstract: A method and a system to obtain the Primary Receiver Scan Carrier Number (PSCN) starting from the data regarding the multiframe number (MFN) in a personal telephone system realized according to the DECT standard. The following steps are present calculating the minimum common multiple (m.c.m.) between the duration of a multiframe (160 ms) and the period necessary for the complete scanning of the frequencies by a radio fixed part (RFP); dividing this minimum common multiple (m.c.m.) by the duration of a multiframe and taking the quotient to obtain a periodicity value; waiting that the multiframe number (MFN) assumes a whole multiple value of the periodicity calculated as indicated above and beginning and the scanning starting from the known frequency (x) which is common to all fixed radio parts (FRP) to be synchronized.

Abstract: A multi-line key telephone system not having a key service unit includes three analog telephone lines to which up to eight, three-line telephones may be connected to provide enhanced service features with cost-effectiveness. System reliability is maintained, notwithstanding a power dependency of the telephones, by including POTS telephones to provide uninterrupted essential telephone service in the event of a power outage. Both data and voice communications between two or more of the three-line telephones is achieved by converting an input digital bit stream from either a digital or analog source into a corresponding out-of-band binary FSK radio frequency output signal that is transceivingly communicated between the three-line telephones as data packets within a TDM frame. The out-of-band signal thus permits analog voice communications on the same line to proceed without interference.

Abstract: A programmable data link module is used on a time division multiplex data bus. The module is functional as an input device, an output device, or both as an input and output device. It can receive data from the data bus during the selected time slot for a selected number of frames to control output devices connected to it. The data link module includes an input circuit for generating a data output signal data to the data bus in response to the input signals from an input device coupled to the module. The input circuit includes a programmable input communication mode selector, allowing the data bus and the data link module to function with or without a host computer. The mode selector provides simplex or duplex.

Abstract: A swept frequency communication system includes a modulator that multiplies a frequency sweep signal with one or more underlying modulated communication signals to produce a swept frequency signal having a number of headerless tracks located directly adjacent one another in the swept frequency/time domain. A demodulator receives the swept frequency signal after that signal has been passed through a wireless channel, isolates a particular track of the received swept frequency signal to prevent a near/far problem, A/D converts the isolated track, resweeps the digitized isolated track, and then equalizes the isolated track using a blind channel equalizer to eliminate time-varying amplitude/phase impairments caused by transmission of that track through the wireless channel. The demodulator then removes the sweep signal from the equalized swept frequency track and decodes or demodulates the underlying modulated communication signal.

Abstract: A transmitting and receiving apparatus of a time division full-duplex spread spectrum communication system prevents transmitting or receiving sensitivity from deteriorating because of the generation of only one oscillation frequency upon transmission or reception using a PLL.

Abstract: A transceiver circuit with a heterodyne receiver circuit is provided. Output signals of first and second local oscillator 103, 104 are mixed by a local frequency converter 105. An output signal of the converter 105 passes a filter 106 and inputs a modulator 111 of a transmitter circuit 101 as well as a first frequency converter 122 of a receiver circuit 102. The second local oscillator 104 comprises a frequency synthesizer whose output signal varies for a transmission or a receiving mode. The output signal of the second local oscillator 104 also inputs the second frequency converter 124 of the receiving mode. A reference frequency of the second local oscillator 104 is set higher than a frequency step between communication channels so that a quick switching of the frequency is performed. Thus, the transceiver circuit of this invention is suitable for a compact size and hardly generates unwanted spurious components at transmission mode.