Abstract: There is disclosed a channel separating filter apparatus for separating a frequency-multiplexed signal comprised of channel signals into respective channel signals. A frequency-converting section frequency-converts the frequency-multiplexed signal into a plurality of channel signals, so that an average value of carrier wave frequencies of two channel signals which are located in the center of the frequency-multiplexed signal and are adjacent to each other becomes substantially zero, and then outputs the plurality of frequency-converted channel signals. Thereafter, a channel separating section separates the plurality of frequency-converted channel signals outputted from the frequency-converting section into respective channel signals each having only a frequency component of each channel signal, thereby separating the frequency-multiplexed signal into at least two channel signals.

Abstract: The symmetrical Cu double lead line is asymmetrically terminated by two digital signal high-pass filters, one thereof at the exchange side being formed with a high-pass filter of the 4th order and the other thereof at the subscriber side being formed with a high-pass filter of the 1st order having a limit frequency of about 0.1.multidot.f.sub.Baud and a high-pass filter of the 2nd order. A high-pass of the 2nd or, respectively, 4th order has a limit frequency of about 100 kHz or with a limit frequency of about 30 kHz given employment of a separate 16 kHz band-stop filter.

Abstract: Auxiliary data is transported in a primary data signal by hiding the data in the form of colored noise. The colored noise has a spectrum that simulates the spectrum of the primary data signal. The data to be transported is first converted to a spread spectrum signal. The primary data signal is analyzed to determine its spectral shape. The same spectral shape is imparted to the spread spectrum signal, which is then combined with the primary data signal for transmission. The spectral shaping can be performed using time domain modeling and synthesis such as linear predictive coding or by using subband coding techniques such as fast Fourier transforms. A plurality of different auxiliary information streams can be transported on the primary data signal. By adjusting the gain of individual spread spectrum signal carrier(s) and the power of the colored noise, the auxiliary information stream(s) can be rendered at a desired level at, below or above an interference threshold in the primary data signal.

Abstract: A transport stream decoder/demultiplexer is provided which includes a program clock recovery circuit for recovering a program clock from program clock reference (PCR) values contained in selected transport packets. A processor is provided for extracting elementary stream data from transport packets labeled with packet identification codes (PIDs) that are specified by a host processor. The processor separately stores the elementary stream data of each stream. A host processor interface is also provided for transferring data between an external host processor and the program clock recovery circuit. A memory manager may be provided for storing the data extracted by the processor for each elementary stream in a corresponding queue. The queues may be maintained by the memory manager in an external RAM. A descrambler interface may be provided for transferring scrambled data and data derived from conditional access information between the processor and an external descrambler.

Abstract: A pulse shaping filter for the .pi./4-shift QPSK modulator employed in IS-54 and JDC. The pulse shaping filter includes symbol determining circuits of the I-channel and the Q-channel, demultiplexers for inverse multiplexing each of the input signal value from the symbol determining circuits, a plurality of shift registers for shifting data from each of the demultiplexers according to odd and even symbol clock, a multiplexer for multiplexing each data from the shift registers to produce the corresponding address values, a plurality of ROM tables for storing the multiplexed address value, and a multiplexing and adding unit for multiplexing the address value stored in the ROM tables and adding the resulting multiplexed value.

Abstract: A network includes a facility for transmitting baseband telephone signals, plural subscriber locations, and twisted pair circuits which connect each subscriber location to the baseband telephone facility. The network further includes apparatus for transmitting and receiving broadband signals over the twisted pair circuits. A broadband transmitter is coupled to a network twisted pair circuit and outputs a broadband signal for delivery to a subscriber location. A first twisted pair circuit is utilized as an intermediate transmission path for the broadband signals. A distribution module is coupled to the first twisted pair circuit and is connected to a destination subscriber location via a destination twisted pair circuit. First filter circuits are connected in the network twisted pair circuit; are transparent to the baseband telephone signals and block the broadband signals.

Abstract: A digital receiver apparatus and method, designed for multiple simultaneous users, digitizes a received analog RF signal and tunes to multiple desired frequencies of the received signal on a time division multiplexed basis. After filtering by a finite impulse response (FIR) filter that also operates in time division multiplexing for multiple service bands, the selected signals are digitally demodulated and signal processed, again on a time-shared basis. Different service bands are accommodated at the same time by separate FIR filters, each including a coefficient memory for its particular service band. The multiplexed frequency signal for each band is multiplied by the coefficients of its respective FIR filter memory in a common complex multiplier. The results are demultiplexed and directed to respective accumulators for decimation in accordance with the FIR coefficient characteristics.

Abstract: A channelized protection circuit for protecting the front-end of a receiver rom the detrimental effects of interference signals within the bandwidth of received signals is disclosed.

Abstract: Auxiliary data is transported in a conventional audio signal by hiding the data in the form of colored noise. The colored noise has a spectrum that simulates the spectrum of the primary audio signal. The data to be transported is first converted to a spread spectrum signal. The primary audio signal is analyzed to determine its spectral shape. The same spectral shape is imparted to the spread spectrum signal, which is then combined with the primary audio signal for transmission. The spectral shaping can be performed using time domain modeling and synthesis such as linear predictive coding or by using subband coding techniques such as fast Fourier transforms. A plurality of different auxiliary information streams can be transported on the audio signal. By adjusting the gain of individual spread spectrum signal carrier(s) and the power of the colored noise, the auxiliary information stream(s) can be rendered inaudible in the primary audio signal, or at any desired level below or above an audible threshold.

Abstract: The range of digital data communication services, such as a basic rate 2B1Q ISDN channel, to customer premises located beyond the industry standard achievable range of a two-wire loop can be extended by increasing the capacity of the ISDN line code from two information bits per symbol to three information bits per symbol, so as to reduce the effective symbol rate, which is error correction encoded to an effective 4B1H line code for defining a sixteen level PAM signal waveform, and employing enhanced low signal-to-noise ratio signal processing techniques in both the transmitter and receiver to accommodate the increased insertion loss of the two-wire line resulting from its extended length. Such enhanced low signal-to-noise ratio signal processing techniques include a Tomlinson precoder in the transmitter, and an adaptive linear equalizer and a module unit in the receiver.

Abstract: A novel finite impulse response filter apparatus and method. A multiplexed data stream composed of two or more data streams is provided as an input to a tapped delay line. Weight and sum operators are connected to the even or odd delay line taps and generate a filtered output. The filter operates on one data stream per cycle and generates a multiplexed output. In another form, odd weight and sum operates are connected to and odd taps generating two filtered outputs. The filter operates on both data streams in each cycle and generates two multiplexed outputs. A crossbar switch is disclosed for parsing the multiplexed outputs into the constituent filtered data streams. The filter stages may be cascaded.

Abstract: A data transmission system including a telephone service subscriber loop utilized for transmission of data including telephone service signals; a splitter operable for splitting the subscriber loop into a first transmission path including a low pass filter which accommodates a continuation of telephone service signal transmissions along the subscriber loop and a second transmission path, said second transmission path including a capacitive element for attenuating the telephone service signals; and a digital subscriber loop transceiver coupled to the second transmission path for implementing high rate digital data transmission over the subscriber loop, the transceiver including a frontend processing circuit having a transmit path and a receive path, at least said receive path comprising a high pass filter for further attenuating said telephone service signals.

Abstract: A digital signal processing apparatus for frequency multiplexing and demultiplexing of narrow band FDM signals has a first block fine processing stage (11) connected in series to a first block coarse processing stage (16, 17) and in parallel therewith a second block fine processing stage (11a) connected in series to a second block coarse processing stage (16, 17). The two stages 11 and 11a are coupled together at one side remote from the two coarse processing stages (16, 17) to provide a first port (14) and the stages (16 and 17) at the side remote from the port (14) provide a plurality of ports (15). Each stage (11, 11a) is a FIR lowpass filter and each stage (16, 17) incorporates a polyphase filter (16) in connection with a Fast Fourier Transform Unit (17).

Abstract: A wideband frequency signal digitizer and method for digitizing multiple bands of a wideband frequency signal. The digitizer and method providing for optimally positioning a segment (402) of the wideband frequency signal within a Nyquist band of an analog-to-digital converter. Remaining segments (402) of the wideband frequency signal are closely positioned relative to the first segment such that the entire wideband frequency signal (400) is easily digitized using a single or multiple analog-to-digital converters (36) while reducing or eliminating undesirable spurious signals.

Abstract: A modular, multi-channel, contiguous output, multiplexer which combines directional filters with the diplexed output of two multi-channel multiplexers, each covering a contiguous frequency band, i.e., one is a low multiplexer and the other a high multiplexer, and one or more quasi-elliptical directional filters after the diplexer output to cover the hole left by the diplexer crossover. A preferred embodiment may essentially consist of: 1) a 12 channel contiguous multiplexer, either a hybrid directional and manifold type multiplexer or a short circuited multiplexer, covering frequencies, e.g., in the range from 3.7 GHz to 4.2 GHz; 2) a 6 channel contiguous multiplexer spanning frequencies substantially in the range from 3.42 GHz to 3.62 GHz; 3) a diplexer including a 6 section Chebyshev filter, with a passband of frequencies, e.g., in the range of 3.4 to 3.620 GHz, and about 30 dB attenuation at 3.7 GHz, and an 8 section Chebyshev filter passing frequencies, e.g., in the range of 3.7 GHz to 4.

Abstract: Disclosed is an apparatus for digitizing an electromagnetic input signal having frequency components within at least first and second segregated frequency bands, particularly useful in a wireless communications system. The apparatus includes a filtering circuit arrangement for passing only frequency components of the input signal substantially within the first and second frequency bands, to provide a filtered signal having a spectrum with spectral components below a predetermined power level within a frequency gap between the first and second frequency bands. An analog to digital (A/D) converter samples the filtered signal at a sampling rate sufficient to provide a digitized output signal with a frequency spectrum corresponding to that of the filtered signal and also with a replica of spectral components of one of the frequency bands appearing within the frequency gap.