Multiplex communications – Wide area network – Packet switching
Patent
1994-09-20
1996-05-07
Hsu, Alpus H.
Multiplex communications
Wide area network
Packet switching
370 30, 375219, 455 77, 455 83, 455 87, 455260, H04B 154, H04B 140, H04L 2704, H04L 2712
Patent
active
055153640
ABSTRACT:
A radio frequency (RF) transceiver includes a direct modulation transmitter and single down-conversion receiver for operation in a time-division-duplex (TDD) telecommunications environment. A single RF signal source, in the form of a phase-lock-loop (PLL), is used on a time-shared basis to provide both the carrier signal for the transmitter and the local oscillator (LO) signal for the receiver. In the transmitter, direct modulation is effected by modulating a voltage-controlled oscillator (VCO) in the PLL with a burst of the transmit data while opening the loop and holding the loop feedback tuning voltage constant. In the receiver, a self-adjusting comparator threshold is provided for automatically setting and adjusting a demodulated signal comparison threshold used in retrieving the data and data clock from the demodulated receive signal. The interface between the transmitter and receiver and the host controller provides the control signals needed for the time-sharing of the single RF signal source, the proper programming of the PLL for the different transmitter carrier and receiver LO frequencies, the PLL loop control for the direct modulation of the VCO, and the enablement, or powering down, of the transmitter and receiver sections to minimize transceiver power consumption.
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Hsu Alpus H.
National Semiconductor Corporation
Ngo Ricky Q.
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