Apparatus for communicating diversity signals over a transmission medium

• US 6,268,946 B1
• Filed: 07/01/1998
• Issued: 07/31/2001
• Est. Priority Date: 07/01/1998
• Status: Expired due to Term

• Current Assignee: Wavex Corporation, WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Radio Frequency Systems Incorporated (Amphenol Corporation)
• Inventors: Farris, Robert L., Wu, Qiang, Larkin, Robert S.
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Nguyen, Chau M.
• Application Number:
  US09/108,627
• Time in Patent Office: 1,126 Days
• Field of Search: 375/219, 375/259, 375/272, 375/303, 375/334, 455/103, 455/93, 455/102, 455/118, 455/105, 455/67.1, 455/162, 359/173, 359/152, 359/180, 359/189, 359/219, 359/259
• US Class Current: 398/163
• CPC Class Codes: H04B 10/25758 between a central unit and a single remote unit by means of an optical fibre
• CPC Class Codes: H04B 7/12 Frequency diversity

Abstract

An apparatus for communicating, over a single transmission medium, two signals of substantially the same center frequency. The apparatus offsets in frequency one of the signals by combining the signal with the signal from a local oscillator. The apparatus then transmits the two signals, one offset from the other, as well as the signal from the local oscillator to allow for recovery of the two signals with a precise correction for the offset. In particular, the transmission medium is an optical fiber and the two signals are a main RF signal and a diversity RF signal received, respectively, by a main element and a diversity element of a diversity antenna system. The invention is of use, for example, in providing to a microbase station a main RF signal and its diversity RF signal received at a diversity antenna system remote from the microbase station and connected to the microbase station by an optical fiber.

Claims

1. An apparatus for simultaneously communicating over a single transmission medium two simultaneously arriving signals of substantially a same center frequency using a local oscillator signal provided by an oscillator, comprising:

a) packaging means, responsive to the two arriving signals, for shifting in frequency one of the two arriving signals based on the local oscillator signal, for providing as a combined signal to the transmission medium the shifted arriving signal, the other arriving signal, and the local oscillator signal; and

b) un-packaging means, responsive to the combined signal, for extracting in turn the local oscillator signal, the shifted arriving signal, and the other arriving signal, and for shifting back to the center frequency the shifted arriving signal based on the extracted oscillator signal to produce an un-shifted arriving signal, for providing the other arriving signal and the un-shifted arriving signal.

2. An apparatus as claimed in claim 1, wherein the transmission medium is an optical fiber.

3. An apparatus as claimed in claim 2, wherein the center frequency is a radio frequency.

4. An apparatus as claimed in claim 3, wherein the packaging means comprises:

a) a mixer, responsive to one of the arriving signals and to the local oscillator signal, for providing a signal that is a multiplication of the local oscillator signal and the arriving signal, for providing as output a signal with a frequency component at a shifted frequency, the shifted frequency equal to the center frequency less the frequency of the oscillator signal;

b) a filter, responsive to the output of the mixer, tuned to the shifted frequency, for providing the shifted arriving signal; and

c) a combiner, responsive to the oscillator signal, the shifted arriving signal, and the other arriving signal, for providing a combined signal.

5. An apparatus as claimed in claim 4, wherein the un-packaging means comprises:

a) a splitter, responsive to the combined signal, for providing the combined signal at three splitter outputs;

b) a bandpass filter substantially tuned to the center frequency, responsive to the combined signal provided at one of the splitter outputs, for providing the other arriving signal;

c) a bandpass filter substantially tuned to the mixing frequency, responsive to the combined signal provided at one of the splitter outputs, for providing the oscillator signal;

d) a bandpass filter substantially tuned to the shifted frequency, responsive to the combined signal provided at one of the splitter outputs, for providing the shifted arriving signal;

e) a mixer, responsive to the filtered shifted signal and to the local oscillator signal, for providing a signal having a component with a frequency equal to the original, center frequency; and

f) a bandpass filter substantially tuned to the center frequency, responsive to the local oscillator signal, for providing the un-shifted arriving signal.

6. An apparatus for simultaneously communicating over a single transmission medium two simultaneously arriving signals of substantially a same center frequency using a local oscillator signal provided by an oscillator, comprising:

a) a source of a local oscillator signal at a mixing frequency;

b) means for shifting in frequency one of the two arriving signals by an amount depending on the mixing frequency, for providing a shifted signal;

c) means for combining the local oscillator signal, the shifted signal, and the other arriving signal, for providing a combined signal for communication over the transmission medium;

d) means responsive to the transmitted combined signal, for providing three samples of the transmitted combined signal;

e) means for extracting the local oscillator signal from one of the samples of the transmitted combined signal;

f) means for extracting the shifted signal from another of the samples of the transmitted combined signal;

g) means for shifting in frequency the extracted shifted signal back to the center frequency using the extracted local oscillator signal, for providing an un-shifted signal; and

h) means for extracting the other arriving signal from another of the samples of the transmitted combined signal.

7. An apparatus as claimed in claim 6, wherein the transmission medium is an optical fiber.

8. An apparatus as claimed in claim 7, wherein the center frequency is a radio frequency.