| 摘要 |
A dual-mode transmitter having an antenna, a mode controller, a source encoder, a tunable-frequency synthesizer, a chip-code generator, a spread-spectrum modulator, a narrowband modualator, a power amplifier, and an adjustable bandpass filter. Also provided is a dual-mode receiver having a mode controller, a tunable-frequency synthesizer, a chip-code generator, an antenna, an adjustable bandpass filter, a preamplifier, a frequency converter, an IF amplifier, a spread-spectrum despreader, a spread-spectrum demodulator, a narrowband modulator, and a source decoder. For the transmitter and receiver, the mode controller selects receiving a narrowband modulation or a spread-spectrum modulation. The tunable-frequency synthesizer generates a local oscillator signal for the receiver, and a carrier signal for the transmitter. The chip-code generator generates a chip code signal for both the transmitter and the receiver. With a narrowband modulation setting of the mode controller, the transmitter and receiver have the adjustable bandpass filters adjusted to a narrowband width for telephone communications. With a spread-spectrum setting of the mode controller, the adjustable bandpass filters and the system are adjusted to transmit and receive a wide bandwidth for passing the spread-spectrum signal. |
