High-speed point-to-point modem-less microwave radio frequency link using direct frequency modulation

• US 6,823,178 B2
• Filed: 02/14/2001
• Issued: 11/23/2004
• Est. Priority Date: 02/14/2001
• Status: Expired due to Fees

• Current Assignee: Google Inc. (Alphabet Inc.)
• Original Assignee: YDI Wireless Incorporated (Proxim Wireless Corporation)
• Inventors: Pleasant, Wayne E., Chandler, Joseph
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Jackson, Blane J.
• Application Number:
  US09/783,722
• Publication Number:
  US 20020111150A1
• Time in Patent Office: 1,378 Days
• Field of Search: 455/119, 455/313, 455/76, 455/11.1, 455/20, 455/21, 455/22, 455/23, 455/17
• US Class Current: 455/119
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A point-to-point microwave radio link that operates in a Frequency Division Duplex (FDD) mode using direct digital modulation with a Continuous Phase-Frequency Shift Keyed (CP-FSK) scheme. The transmit signal is generated by a circuit that uses a Voltage-Control Oscillator (VCO) operating in a microwave radio band. The VCO is deviated over a narrow frequency range that is reduced by a predetermined factor. The output of the VCO is then frequency multiplied by the predetermined factor to produce the modulated microwave output signal at the desired band. The deviation frequency of the VCO is thus chosen to be the reciprocal of the multiplication factor times the transport bit rate.

Claims

1. An apparatus comprising:

a transport to microwave radio frequency adapter that accepts an input telecommunications transport signal on an input port and converts information in such signal to a desired microwave Radio Frequency (RD carrier, the input transport signal carrying information at an input bit rate, wherein the transport to microwave RF adapter further comprises;

a voltage-control oscillator, coupled to receive the input transport signal, the voltage-control oscillator implementing a continuous phase frequency shift keyed deviation such that a first frequency is selected to indicate a first logical value for an input data bit in the transport signal and a second frequency is selected to indicate a second logical value for an input data bit in the transport signal, the deviation between the two frequencies selected to be equal to a predetermined fraction of the input bit rate;

a first frequency multiplier connected to receive the output of the voltage-controlled oscillator and to multiply the output of the voltage controlled oscillator to the desired microwave RF carrier; and

a microwave RF to transport adapter, to convert a received microwave RF signal to a transport signal carrying an output telecommunications transport signal, wherein the microwave RF to transport adapter further comprises;

an oscillator, operating at a carrier frequency which is a predetermined fraction of a desired direct down-conversion frequency;

a second frequency multiplier, connected to receive the oscillator output, and to multiply the oscillator output up to the desired direct down-conversion frequency; and

a mixer, coupled to the frequency multiplier and the microwave RF signal, to provide a down-converted transport signal; and

a pair of bandpass filters, a first bandpass filter tuned to a frequency which is equal to the down-conversion frequency plus one-half a data rate of the down-converted transport signal, and a second bandpass filter tuned to a frequency which is equal to the down-conversion frequency minus one-half the data rate of the down-converted transport signal.

2. An apparatus as in claim 1 wherein the telecommunications transport signal is provided on an optical physical medium.

3. An apparatus as in claim 2 additionally comprising:

an optical-to-voltage transducer connected to receive the telecommunications signal and to provide a baseband electrical signal at an output.

4. An apparatus as in claim 1 wherein the first frequency multiplier implements a multiplication factor which is a reciprocal of the predetermined fraction used as the deviation in the voltage-controlled oscillator.

5. An apparatus as in claim 4 wherein the first frequency multiplier is implemented in a plurality of frequency multiplication stages.

6. An apparatus as in claim 1 wherein the voltage-controlled oscillator and first frequency multiplier perform a direct conversion of the input transport signal to the microwave RF carrier.

7. An apparatus as in claim 6 wherein the direct conversion is performed without using the input transport signal to modulate an intermediate carrier signal.

8. An apparatus as in claim 1 additionally comprising:

a microwave bandpass filter connected to the output of the first frequency multiplier to filter harmonics of the carrier frequency of the voltage-controlled oscillator.

9. An apparatus as in claim 1 additionally comprising:

a pair of detector diodes, each diode connected to a respective one of the bandpass filters, and to each provide a detected signal.

10. An apparatus as in claim 9 additionally comprising;

a differential amplifier, connected to receive the two detected signals, and to provide the output transport signal.

11. An apparatus as in claim 10 additionally comprising:

an electrical-to-optical transducer, coupled to the differential amplifier output, to provide an optical transport signal.