Abstract: A balanced modulator has a pair of diodes, a plurality of line patterns including a balance-to-unbalance converter, the line patterns including lines extending toward and connected to the diodes, respectively, and at least a set of capacitive stubs disposed near the lines and spaced from each other by a distance of .lambda./8 (.lambda. is the wavelength at a frequency used). The capacitive stubs are connectable to the lines by bonding wires for isolation adjustments.

Abstract: A data transmission and reception system according to this invention comprises a transmitter for transmitting data by modulating transmit data and a receiver for receiving and demodulating a signal from the receiver, wherein the receiver includes a parallel resonator for receiving a PSK signal; a full rectification circuit for detecting output from the parallel resonator; a low pass filter for shaping the waveform of output from the full rectification circuit; and a comparator for converting output from the low pass filter into a binary-coded signal so that demodulated signals can be obtained from the output of the comparator.

Abstract: A digital communication system having a transmitter and a receiver. The receiver transmits a radio-frequency (RF) signal that is continuous phase modulated by digital data. The receiver having a converter, a differential detector, and a sequential decoder. The receiver receives the RF signal. The RF signal is converted into a baseband signal by the converter. The baseband signal is received by the differential detector wherein the continuous phase modulation of the baseband signal is detected. The detected signal is received and the digital data is decoded by the sequential decoder. The sequential decoder has a Viterbi decoder to compensate for intersymbol interference caused by the differential detector. The Viterbi decoder performs reduced Viterbi decoding utilizing a feedback loop (FB) for reducing computing inaccuracies due to the reduction of the number of trellis states.

Abstract: A data and clock recovery circuit includes a front end circuit for receiving a data signal encoded with a Manchester or other bi-phase level code having a sequence of bit frames, and for outputting a recovered data signal and a recovered clock signal in accordance with transitions in the data signal that overlap with a window signal. A window generation circuit generates the window signal in accordance with a delay control signal, and includes circuitry that delays and transforms the recovered clock signal into the window signal. A delay control circuit generates and adjusts the delay control signal. A phase comparison circuit compares the recovered clock signal with leading and lagging portions of the window signal, and generates signals that adjust the delay control signal when the recovered clock signal overlaps with either of the leading and lagging portions of the signal.

Abstract: Transmission system with a transmitter (T), a receiver (R), and a filter combination (FI1, FI2; FQ1, FQ2) for transmitting a digital signal (sr), encoded in symbols (Si), from the transmitter (T) to the receiver (R) at any frequency position by quadrature modulation, wherein one of the two quadrature signal components (ki, kq) in the transmitter is delayed before the quadrature modulation by a time interval td, particularly by td=Tsymb/4. (FIG.

Abstract: In a transmitting unit, an input signal is converted into an I data sequence of an in-phase (I) symbol and a Q data sequence of a quadrature (Q) symbol, a differential encoding is performed for the I and Q data sequences according to a differential binary phase shift keying (DBPSK) modulation to produce an I code sequence and a Q code sequence, a spectrum of the I code sequence is spread by a first spreading code signal to produce an I spread spectrum signal, a spectrum of the Q code sequence is spread by a second spreading code signal to produce a Q spread spectrum signal, the I and Q spread spectrum signals are quadrature-modulated to a synthesized signal, and the synthesized signal is transmitted to a receiving unit.

Abstract: A phase shift modulator at the transmitter has a control input connected to a binary signal source. A high frequency carrier signal is applied to a carrier signal input of the modulator. The modulated carrier signal is transmitted to a receiver where it is mixed with a local oscillator frequency. At the receiver, a modulated signal is amplified by a limit amplifier to form the received signal into square wave pulses of a uniform height. The demodulator detects when the spacing between the edges of the square wave signal change in response to the phase shift modulation at the transmitter. When the spacing between the edges of the square wave IF signal is detected to be shorter than the normal spacing for a steady IF signal with no modulation, this signifies a first binary value. A longer than normal spacing between the edges of the square wave IF signal signifies a second binary value. Frequency drift compensation circuits are disclosed to overcome frequency variations in the carrier and the local oscillator.

Abstract: An apparatus and a method for detecting a carrier signal of a phase shift keyed modulated signal. A first counter circuit generates a plurality of counts, with each count being a number of cycles of a reference frequency signal occurring between two consecutive rising edges of an intermediate frequency signal. A comparison circuit compares a first count of reference frequency cycles to a second count of reference frequency cycles when a difference between an initial count of reference frequency cycles and a first predetermined number is less than a second predetermined number. The first predetermined number represents a time period of one cycle of the nominal center frequency, and the first count and the second count respectively represent time periods of first and second cycles of a pair of consecutive cycles of the intermediate frequency signal. The comparison circuit generates a difference signal when a difference between the first count and the second count is less than a third predetermined number.

Abstract: The encoding/transmission of information in an OFDM system is enhanced by using complementary codes. The complementary codes, more particularly, are converted into phase vectors and the resulting phase vectors are then used to modulate respective carrier signals. The modulated result is then transmitted to a receiver which decodes the received signals to recover the encoded information.

Abstract: A rectangular to phase converter (201) includes a first converter circuit (201B) which limits signals to a predetermined level. A phase selector (259) selects a relative phase from the limited signals. According to one aspect of the invention, input rectangular coordinate signals are mapped to the first quadrant in a first quadrant mapping circuit (201A) before the first quadrant signals are limited and the relative phase signal is returned to the original quadrant by an original quadrant mapping circuit (260).

Abstract: The encoding/transmission of information in an OFDM system is enhanced by using complementary codes and different patterns of amplitude modulation representing respective data words. The complementary codes, more particularly, are converted into phase vectors and modulated by the selected pattern. The result is then used to modulate respective carrier signals. The modulated result is then transmitted to a receiver which decodes the received signals to recover the encoded information.

Abstract: A system and method are provided in which a phase modulation generator is used to modulate the output signal of a DDS with a modulation index, h/N. The phase-modulated. DDS output drives a PLL, which is an upconversion stage for a radio transmitter, with the modulated DDS signal as the PLL's reference. The output of the PLL will have a modulation index of h. Consequently, the frequency band of the DDS output is significantly narrower than the frequency band of upconversion stages used in conventional transmitters, and there are significantly less spurious emissions in the transmitted signal. However, a transmitter employing the present phase-modulated DDS-driven PLL topology can still transmit over a relatively wide frequency band.

Abstract: A modulator device is disclosed for a spread spectrum communication system which generates a modulated signal from incoming data. The device includes a QPSK portion for separating the incoming data into two data channels and for further spreading the two channels over a wide bandwidth according to a predetermined spreading code. A phase mapping element coupled to the QPSK portion for processing both channels in order to minimize spectral regrowth of the modulated signal by preventing the RF envelope deviation from going close to zero. Pulse shaping elements coupled to the phase mapping element for further processing each channel in order to improve the modulator spectral efficiency and minimize adjacent channel interference. A quad-mixer coupled to the pulse shaping elements for combining both channels into a recombined signal and for further modulating the recombined signal according to a predetermined carrier frequency.

Abstract: A tunable digital modulator is tunable across an R.F. frequency range for transmission without additional frequency conversion and includes two toggled multiplexed analog-to-digital converters for reducing spurious frequency components in the output. The modulator and digital-to-analog converters are fabricated in a single integrated circuit with the two converters laid out physically in adjacent spaces with their gain and voltage characteristics matched. By alternating the two digital-to-analog converters in producing the analog modulated signal output, transients from switching of the converters have a chance to die out before the output of each converter is sampled. Thus, any spurious glitch energy is greatly attenuated.

Abstract: Coherent demodulation of phase shift keyed direct sequence spread spectrum generally needs a strong pilot to provide channel estimates and to avoid phase ambiguities. This invention relates to a novel approach in which the pilot takes the form a few known chips in every bit and in which the channel is estimated primarily by decision directed removal of the modulation and the pilot chips serve to resolve the 180 degree phase ambiguity.

Abstract: A frequency translation device in a first embodiment includes a plurality of multiplying digital-to-analog converters (MDACs) that multiply an input signal by phase shifted digital sinewave approximation signals to perform frequency translation. In the preferred embodiment the input includes inphase and quadrature phase components, one of which is multiplied by a digital sinewave approximation and the other is multiplied by a digital cosinewave approximation. The use of the multiple MDACs with differing sinewave approximation signals provides a signal that multiplies the input signal such that the effects of odd harmonics at an output are mitigated while the advantages of a traditional switching mixer are retained.

Abstract: A high speed telemetry system for implantable devices such as a pacemaker includes a transmitter disposed in an implantable housing and an external receiver. Typically the housing is metallic and it attenuates drastically electromagnetic signals having frequencies above a relatively low cut-off frequency. The transmitter includes circuitry for generating cosine waves of different frequencies and for selectively assembling these waves to define a set of data symbols. Preferably one of the frequency is a multiple of the other. Integer halve-periods of the waves are selected to define the symbols such that the overall data transmission rate exceeds the cutoff frequency. The external receiver synchronizes itself to the transmitter, and decodes the symbols using a constellation chart to decode the symbols into binary data.

Abstract: A re-sampling circuit includes a poly-phase finite impulse response (FIR) interpolator; a polynomial interpolator having a sample input connected to a sample output of the poly-phase FIR interpolator; and a numerically controlled oscillator (NCO) having an output partitioned into: Nc integer bits connected to a control input of the FIR interpolator, and Nf fractional bits connected to a control input of the polynomial interpolator. The circuit may also include a reference clock for generating a reference clock signal. The NCO preferably further comprises a sample clock generator for generating a sample clock signal based on the reference clock signal, and the FIR interpolator further has a sample clock input for receiving the sample clock signal from the sample clock generator.

Abstract: A method and apparatus for receiving and transmitting direct sequence spread spectrum signals uses a single integrated device for converting and demodulating an RF signal into a serial data signal. Critical timing relationships during the acquisition and demodulation of the received signal are satisfied by the use of an integrated circuit specially designed to perform all operations needed to convert the physical signal to an media access circuit level data signal.

Abstract: The number of oscillators required to construct a digital radiocommunication terminal can be reduced and a circuit used for the digital radiocommunication terminal can be reduced in size. For this purpose, the digital radiocommunication terminal for effecting information transmission using an N (integer)-phase-shift-keyed signal (identification symbol number N=4 upon .pi./4 shifted QPSK modulation), is constructed such that an oscillation frequency generated from a reference oscillator employed with a frequency synthesizer is selected to have a common multiple of a second intermediate frequency and an identification symbol phase N and is supplied to a detector for outputting received data therefrom.

Abstract: Binary data is transmitted to a network physical layer from a media access controller as a series of multibit nibbles and is encoded into a multi-level data stream and split among a number of transmission channels, thereby reducing the signal frequency necessary to carry the data on each one of the transmission channels. The multi-level signal is then translated at a receiver back into a binary data stream. In a specific embodiment, the symbol transmission frequency on each of the transmission channels is at the same frequency as the nibble transfer rate between the media access controller and the physical layer.

Abstract: A system for transmitting information over an OFDM channel using phase shift keying encoding employs a bit mapping encoder to reduce the crest factor (ratio of peak voltage to RMS voltage). For a 16 subchannel OFDM system using QPSK encoding, a first set of four symmetrically positioned pairs of subchannels is used to encode two bits of information on each subchannel. A second set of four symmetrically positioned pairs of subchannels is used to encode only one bit of information on each subchannel, with the resultant phasor for each pair of the second set of pairs of subchannels being orthogonal to the resultant phasor for one of the pairs of the first set of subchannels. With this arrangement, the crest factor is reduced.

Abstract: A multiple-modulation communication system includes a transmitter that modulates and transmits communication signals modulated by a first modulation technique and communication signals modulated by a second modulation technique. The first modulation technique and the second modulation technique are different. The communication system also includes a receiver capable of receiving the communication signals modulated by the first modulation technique and the communication signals modulated by the second modulation technique and demodulating the communication signals.

Abstract: A multichannel frequency phase variable signal source is described having particular application in the simulation of an emitter environment for testing interferometer receivers. An improved direct digital frequency synthesizer produces phase information for initiating the operation of a related frequency synthesizer at a different phase point from those of the remainder of the synthesizers forming the multi channel source. An improved direct digital frequency synthesizer is described for varying this phase information.

Abstract: A broadcasting method for simultaneously broadcasting analog and digital signals in a standard AM broadcasting channel is provided by: broadcasting an amplitude modulated radio frequency signal having a first frequency spectrum, wherein the amplitude modulated radio frequency signal includes a first carrier modulated by an analog program signal; and simultaneously broadcasting a plurality of digitally modulated carrier signals within a bandwidth which encompasses the first frequency spectrum, each of the digitally modulated carrier signals being modulated by a portion of a digital program signal, wherein a first group of the digitally modulated carrier signals lying within the first frequency spectrum are modulated in-quadrature with the first carrier signal, and wherein second and third groups of the digitally modulated carrier signals lie outside of the first frequency spectrum and are modulated both in-phase and in-quadrature with the first carrier signal.

Abstract: A frequency offset compensation method has the steps of raising the detected signal to the M-th power to remove a modulation factor from the received signal, and accumulating the M-th power signals for N (N is an integer) symbols to derive a phase component of the accumulated M-th power signals. Then, the derived phase component is divided into M so as to obtain an estimation value with respect to phase shift due to frequency offset which represents frequency deviation from a true carrier frequency contained in the received signal, and the received signal is multiplied by the obtained estimation value in a form of conjugate complex number to remove the phase shift due to the frequency offset from the received signal.

Abstract: An automatic frequency control apparatus includes a sampling portion for sampling the signal transmitted according to a phase-shift keying method, a phase difference detector for detecting the phase difference between the currently sampled signal and the immediately preceding sampled signal, and a phase bin comparator for determining which of a number of reference phases the phase of the transmitted signal is closest to, using a quantization characteristic of phase during transmission. The frequency offset generated by the distance between the frequency of a carrier wave and the local oscillation frequency of a receiver, or by the Doppler shift, in a MPSK communication method is determined as the phase difference between the detected phase difference information and the determined reference phase information. The apparatus can be used for the automatic frequency control of a modem using any type of MPSK modulation.

Abstract: Microwave two-phase modulator and mixer each comprising a balance/unbalance transformer section to which a microwave signal is applied; a synthetic/branching line section which is connected to the both ends of the balancing line of the balance/unbalance transformer section on the balancing line side; isolation diodes are mounted between diode-mounting lines section and fan-shaped patterns; a plurality of modulating characteristic-adjusting, capacitive stubs placed near the diode-mounting lines; an input line; a modulating signal input line; and a modulated signal output line. The modulating characteristics are adjusted by connecting the diode-mounting lines and the plurality of capacitive stubs by bonding wires or cutting some of the connecting wires.

Abstract: A frequency synthesizer in which a PLL synthesizer 50 generates signals of frequency steps of an integer times a target frequency step. A base band generator 2 digitally generates sine wave signal components of the target frequency step. The outputs from the PLL synthesizer 50 and the base band generator 2 are cross-modulated by use of a quadrature modulator 1 to change the frequency of the output signals with a change step of the base band generator 2.

Abstract: A communication system that reduces significantly the processing required to search over unknown time delays and unknown frequency shifts. Convolutional type processing with a unique re-indexing of the desired signal's Fourier transform is provided so as to allow for the design of a communication system that is invariant to time of arrival and frequency shift such as that caused by doppler effects from moving vehicles or moving satellites. The processing required is several orders of magnitude less computationally intensive than conventional approaches to solving this problem. In addition, the inventive convolutional ambiguity multiple access (CAMA) system can be used in conjunction with M-Ary FSK (Frequency Shift Keying) and other coding techniques to decode the various frequency codes efficiently.

Abstract: A selectable demodulator (32) operates in the phase domain to implement a coherent demodulation path (40) and a differentially coherent demodulation path (42). The coherent path (40) includes a differential encoder circuit (46) to produce coherently demodulated differential data. Magnitude converters (62, 62') convert phase errors in each path into magnitude values. A comparison circuit (66) compares magnitude values from the two paths (40, 42) and selects the path encountering the least phase error. A selection circuit (60) provides data codes demodulated in accordance with the selection.

Abstract: In a communications system, an apparatus and method for detecting a valid signal from noise. An adaptive threshold is used to qualify a received signal. The adaptive threshold is set according to the number of false detects occurring within a given time interval. The number of false detects is initially determined by a quick qualification process. This initial number is subsequently adjusted by a more accurate qualification process. The transmitted signal is modulated with a particular pattern. Upon receiving the signal, it is demodulated to retrieve that pattern. The demodulated pattern is correlated against multiple reference patterns and combined to provide a measure of peak correlation that is independent of pattern phase. Furthermore, a tone detector is used to distinguish valid signals from interfering tones. Two different types of detection methods are performed in parallel. One is based on the energy of the received signal, whereas the other is based on the correlation of the received signal.

Abstract: A digital quadriphase-shift keying modulator is described which generates a modulated intermediate carrier frequency (IF) based on a desired number of samples for each input information bit. The design includes a ROM (or RAM) look-up table which stores digitized waveforms. The inphase and quadrature components of a complex baseband signal are translated to an IF at a multiple of the sampling rate simply by alternating the inphase and quadrature samples and alternating signs. The real IF output is produced by summing the inphase and quadrature signals.

Abstract: A slotline binary phase shift keyed (BPSK) modulator that is capable of operating at high frequency with relatively low sensitivity to terminating impedance. The slotline BPSK modulator comprises a slotline formed in a conductive layer disposed on a substrate, and a pair of diodes coupled to the conductive layer and disposed across the slotline. An RF carrier input signal is coupled to the slotline using a microstrip-to-coplanar line transition that forms one portion of a balanced transformer. The balanced transformer applies the RF carrier input signal with equal amplitude and 180 degree phase difference to each of the diodes. A modulating baseband signal is injected into the microstrip-to-coplanar line transition through a microstrip line and a lumped element low pass filter coupled to the microstrip-to-coplanar line transition. A direct via hole is provided for coupling a baseband modulating signal from the microstrip-to-coplanar line transition to the diodes.

Abstract: Data words are transmitted over a radio channel with a novel modulation scheme which transmits data in parallel. An entire data word is modulated by separating a carrier frequency band into a number of discrete `tones`. Tone T.sub.1 is set to a zero phase shift in order to provide timing in synchronization of the signal. The remaining tones are phase shifted according to a predetermined convention, thereby encoding the bits of the data word. The phase shifts for all tones comprises a spectrum which is transmitted to a receiver simultaneously. A receiver monitors tone T.sub.1 for zero phase shifts to provide synchronization of the signal. The remaining tones are analyzed for their phase shift to provide bits which are assembled into a transmitted data word. Since the bits are transmitted in parallel as the data word, as opposed to conventional modulation schemes, the throughput is increased.

Abstract: Binary signals that are transmitted by Manchester coding and frequency modulation are demodulated based on the behavior of the phase or complex vector value of the received signal. The polarities of the information bits may be determined by measuring the phase excursions in the middles of the Manchester symbols. A phase reference is established from a plurality of candidate phase references as a basis for comparison of the mid-symbol phase. The phase can be measured at the start-points and end-points of the symbols and averaged, or measured a plurality of times during each symbol period to generate a reference phase.

Abstract: An error-correcting tandem encoding system includes a transmitter section and a receiver section. The transmitter section comprises a multiplexer for multiplexing data and voice signals supplied thereto, a Reed-Solomon encoder for Reed-Solomon-encoding an output signal from the multiplexer while interleaving the output signal without causing a delay, a convolutional encoder for convolutionally encoding a Reed-Solomon encoded signal from the Reed-Solomon encoder, and a PSK modulator having a fixed bit rate for phase-shift-keying an output signal from the convolutional encoder.

Abstract: A low power consumption BPSK modulator uses only one center-tapped transformer and a single-pole double-throw (SPDT) switching arrangement including four field effect transistors and a pair of termination resistors. An advantage of the subject invention is that the DC switching current is reduced by a factor of approximately 1500 with respect to a conventional diode ring modulator. An extremely important advantage of the subject invention in the field of handheld battery-powered communications equipment is that the subject apparatus can be made relatively small due to the necessity for only one transformer.

Abstract: A low power consumption BPSK modulator uses only a single input transformer which is not required to be center-tapped, and a switching arrangement including four junction field effect transistors. An advantage of the subject invention is that the DC switching current is reduced by a factor of approximately 1500 with respect to a conventional diode ring modulator. The carrier signal loss of the subject apparatus is lower than that exhibited by a ring modulator due to the use of only a single transformer, and due to the low on-resistance of the JFETs. An extremely important advantage of the subject invention in the field of cordless telephone handsets is that the subject apparatus can be made relatively small due to the necessity for only one transformer.

Abstract: A .pi./4-DQPSK differential phase state encoder/decoder (Codec) is presented which can be implemented using a small number of logic gates. The phase state Codec acts upon data in the transmitter and in the receiver of a .pi./4-DQPSK modulating system whereby the use of a look-up table technique or other off-line procedure to ensure proper phase transitions is not required. The phase state Codec is configured to ensure compliance with the IS-54 standard as well as other similar standards.

Abstract: A radio modulator/demodulator particularly suitable for TDMA mobile telephone use employs digital techniques for GMSK phase modulation. Phase numbers representative respectively of an intermediate frequency carrier and modulation symbols are combined digitally to combination phase numbers which are subjected to a single folded cosine table to produce a digital trignometric sequence of numbers for modulating the transmitter. Economy of components and memory is achieved and some of the modulator components are used in demodulation which is effected by the single look-up table used in sine and cosine mode alternately.

Abstract: A transmitting apparatus based on phase modulation including a data encoding circuit (100), a phase locus control circuit (200) and a modulator (300). The data encoding circuit (100) divides input data to be transmitted into a predetermined number of bits, and sequentially outputs them as segmented data. The phase locus control circuit (200) outputs a phase locus control signal representing each of the segmented data by three values of a positive direction, a negative direction and a non-rotation state of the phase rotation. The modulator (300) changes the phase of a transmission signal in response to the phase locus control signal. Using the phase rotation direction information of the three values makes it possible to reduce transmission bits, to increase transmission speed and transmission capacity.

Abstract: A modulator for data transmitted in a reverse channel or upstream spectrum in a cable transmission system requires a single frequency translation from baseband to a selected RF channel, thus eliminating conventional intermediate frequency (IF) translation. The modulator requires fewer components than the conventional modulator while eliminating nonlinearity, noise, and delay introduced by the IF upconversion. In a preferred embodiment, the modulator includes a serial to parallel differential quadrature phase shift keying encoder with transversal FIR filters and interpolation filters connecting the phase shift keyed data to a single mixer stage for directly translating the baseband signal to an RF (e.g., 5-40 MHz) channel spectrum.