Agile frequency converter for multichannel systems using IF-RF level exhange and tunable filters

• US 7,003,275 B1
• Filed: 05/18/2000
• Issued: 02/21/2006
• Est. Priority Date: 05/18/2000
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Broadband Innovations, Inc.
• Inventors: Petrovic, Branislav
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Stein, Julie E
• Application Number:
  US09/574,707
• Time in Patent Office: 2,105 Days
• Field of Search: 455/118, 455/127.2, 455/127.3, 455/114.1, 455/114.2, 455/126, 455/114.3
• US Class Current: 455/323
• CPC Class Codes: H03D 7/161 all the frequency changers being connected in cascade
• CPC Class Codes: H04J 1/085 Terminal station; Combined modulator and demodulator circuits
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

Agile frequency converter and method, IF-RF level exchange process, and notch filtering techniques. System noise and spurious levels generated by channel frequency conversion is reduced in applications requiring broadband combining of frequency converters to form multichannel composite signal. Converter employs two-stage frequency conversion process, with gain exchange system using variable pre-mixer gain and variable post-mixer attenuation to maintain constant RF output signal power level. For those few conversion frequencies where distortion component(s) cannot be filtered without degrading desired signal, IF-RF level exchange is optimized for meeting the carrier-to-distortion (C/D) ratio specifications at slight expense of noise level for that channel only, while still meeting aggregate combined carrier-to-noise (C/N) specification requirements. Optimal apportionment of level exchange for each channel depends on specific frequency rejection capability of spurious components and is matched to filtering capability and stored within non-volatile memory of a microcontroller used in the frequency converter.

Claims

1. A method of optimizing frequency conversion, comprising:

receiving an input signal having a first frequency;

controlling a level of said input signal;

receiving a local oscillator signal having a second frequency;

converting said first frequency into a third frequency by mixing said input signal with said local oscillator signal to generate an output signal having said third frequency said converting including a frequency down-conversion of a modulated input IF signal to an assigned one of a plurality of RF output channels having a frequency value selected from a set of desired frequency values by tuning said second frequency of said local oscillator signal to a corresponding frequency value;

controlling a level of said output signal;

combining variable attenuation, and variable or fixed amplification of each of said IF signal and RF channel;

filtering one or more distortion components from at least one of said plurality of assigned RF output channels;

determining a desired trade-off between a signal to noise ratio and a signal to distortion ratio of said output signal for each one of said set of desired frequency values;

achieving said desired trade-off by maintaining a constant desired output RF signal level by adjusting said level of said modulated IF input level to an extent not exceeding specification requirements set for said signal-to-distortion ratio of said output RF signal;

optimizing exchange rate coefficients on a channel-by-channel basis; and

programming said coefficients in non-volatile memory utilizing a controller.

2. A method of optimized frequency conversion for generating a broadband composite signal having a plurality of RF channels, each of the plurality of RF channels including a unique subset of a contiguous range of channel frequencies, the method comprising:

assigning each of a plurality of modulation signals to each of the plurality of RF channels, each of the modulation signals having at least one frequency component and a first frequency;

converting the at least one frequency component from said first frequency to a third frequency wherein the third frequency is contained within the subset of channel frequencies corresponding to the RF channel to which each modulation signal is assigned, the converting further comprising;

mixing said plurality of modulation signals with signals having a first local signal to generate a signal having a second frequency;

amplifying a level of said signal having said second frequency;

mixing said amplified signal with a second local signal to generate a converted output having a frequency component equal to said third frequency;

attenuating said converted output for each of the plurality of modulation signals to produce a desired trade-off between a signal-to-noise ratio and a signal-to-distortion ratio of said output signal while maintaining a desired constant level of said output signal; and

summing the converted outputs.

3. The method of claim 2, wherein said attenuating of said converted output is sufficient to reverse said amplifying of said signal having said second frequency;

and further comprising normalizing said converted outputs to substantially the same output level.

4. The method of claim 3, further comprising filtering a component of said converted outputs to provide a frequency equal to about two times said third frequency.

5. The method of claim 4, wherein said filtering further comprises providing a component of said converted outputs having a frequency equal to said second frequency minus said third frequency.

6. The method of claim 2, wherein said amplifying and said attenuating are skipped for those modulation signals for which a distortion component having a frequency equal to said second frequency minus said third frequency cannot be filtered without affecting said converted signal.