초록 ▼

An asynchronous FSK modulator-demodulator (modem) having a capability of operating at data rates of 300, 600 and 1200 bits per second in a voiceband telephone channel is compatible with the specifications of the Bell 103/113, Bell 202, CCITT V.21 and CCITT V.23 modem types. The modem according to th

An asynchronous FSK modulator-demodulator (modem) having a capability of operating at data rates of 300, 600 and 1200 bits per second in a voiceband telephone channel is compatible with the specifications of the Bell 103/113, Bell 202, CCITT V.21 and CCITT V.23 modem types. The modem according to the invention is incorporated into a single integrated circuit to minimize external components in a system. The modem is pin programmable, that is, the mode and speed of operation is defined by a parallel digital data signal applied to device terminals. Digital signal processing techniques are employed to perform all major functions, including modulation and filtering. Multiplication functions are performed without need for multipliers by employing shift registers and canonic sign arithmetic. Analog-to-digital conversion and digital-to-analog conversion circuits are incorporated into the device.

대표청구항 ▼

An integrated circuit apparatus for modulating and demodulating an analog signal with digital data, said apparatus transmitting and receiving the analog signal in preselected types of voiceband communication channels, said apparatus comprising: means for modulating the analog signal with digital dat

An integrated circuit apparatus for modulating and demodulating an analog signal with digital data, said apparatus transmitting and receiving the analog signal in preselected types of voiceband communication channels, said apparatus comprising: means for modulating the analog signal with digital data and to produce a frequency shift keyed analog signal according to a selected one of a plurality of frequency shift keyed signaling standards; means for transmitting the frequency shift keyed analog signal, said transmitting means includes means for digitally synthesizing digital representations of analog signals at selected frequencies, wherein the selected frequencies are selected according to the bit value of digital data supplied to said transmitting means; wherein the means for digitally synthesizing digital representations of the analog signals at selected frequencies represents the analog signals as time-incremented digital signals; means for incrementing the time-incremented digital signals to generate a digital representation of a sine wave signal having said selected frequency; said transmitting means includes a digital-to analog converter for converting the digitally synthesized representations to modulated analog signals for exciting a voiceband communication channel; means for receiving an analog frequency shift keyed signal and demodulating said signal according to the selected one of said plurality of frequency shift keyed signaling standards; and control means for preselecting said selected one of said plurality of signaling standards in accordance with the preselected type of voiceband communication channel.