DIGITAL TAS TRANSMITTER AND RECEIVER SYSTEMS AND METHODS

• US 20080284637A1
• Filed: 01/28/2008
• Published: 11/20/2008
• Est. Priority Date: 02/28/2007
• Status: Abandoned Application

• Current Assignee: Garmin International, Inc. (Garmin Limited)
• Original Assignee: Garmin International, Inc. (Garmin Limited)
• Inventors: Needham, Edward W., Blessing, John C., Hall, Jeffrey S.
• Application Number:
  US12/020,986
• Publication Number:
  US 20080284637A1
• Time in Patent Office: Days
• US Class Current: 342/30
• CPC Class Codes: G01S 13/784 Coders or decoders therefor; Degarbling systems; Defruiting systems
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft
• CPC Class Codes: G01S 3/46 using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 7/4021 of receivers

Abstract

A directional receiver is provided for an aircraft collision avoidance system. The receiver may include input channels that are configured to receive uncompressed linear analog signals from antenna elements that are arranged within a predetermined antenna element geometry. The receiver may further include Analog to Digital (A/D) converter modules, a quadrature converter module and a combiner module. The A/D converter modules can convert each of the analog signals to uncompressed linear digital data and output separate digital data streams that correspond to each of the input channels. The quadrature converter module can mix the digital data streams with corresponding digital reference signals to produce digital In-phase (I) and Quadrature (Q) streams.

Claims

1. A digital receiver for an aircraft collision avoidance system, comprising:

a plurality of antenna elements arranged within a predetermined antenna element geometry;

an analog-to-digital module to convert analog signals received by the antenna elements to uncompressed, linear digital data and outputting separate digital data streams corresponding to each of the antenna elements;

a converter module to mix the digital data streams with corresponding digital reference signals to produce digital In-phase (I) and Quadrature (Q) data streams associated with each of the antenna elements, the reference signals having phase differences there between; and

a combiner module to combine the I and Q data streams to form a directional or omni-directional beam-former data stream.

2. The digital receiver of claim 1, further comprising a log module receiving and converting the beam-former data stream to a log-video data stream, the beam-former data stream representing a non-logarithmic, non-compressed data stream prior to conversion at the log module.

3. The digital receiver of claim 1, further comprising

a first summer to sum the I data streams,

a second summer to sum the Q data streams to form summed I and Q data streams that are uncompressed and linear,

one or more low-pass filters operable to low-pass filter the summed I data and the summed Q data streams to produce filtered I data and filtered Q data,

one or more square calculation modules operable to square the filtered I data and the filtered Q data to produce squared I data and squared Q data, and

a third summer operable to sum the squared I data and squared Q data to produce the beam-former data stream.

4. The digital receiver of claim 1, wherein the converter module includes a plurality of look-up tables, each of the look-up tables storing a digital representation of the reference signal, the converter module addressing the look-up tables at addresses that are offset with respect to one another in order to define a phase difference between the reference signals.

5. The digital receiver of claim 1, wherein the converter module includes local digital oscillators that produce digital oscillator signals representing the reference signals.

6. The digital receiver of claim 1, wherein the converter module includes, in connection with each antenna element, first and second look-up tables storing representations of a common reference signal, the converter module accessing the first and second look-up tables in an offset manner that defines a phase shift of approximately 90°

to form in-phase and quadrature reference signals.

7. The digital receiver of claim 1, wherein the converter module includes a plurality of re-writable look-up tables, each of the look-up tables storing a digital representation of the reference signal, the converter module addressing the look-up tables generally simultaneously in a generally sequential order to produce in-phase reference signals, the phase of each in-phase reference signal being defined by digital data values stored in one or more addresses of each look-up table, and sub-modules to delay each in-phase signal to produce quadrature reference signals which lag behind the in-phase reference signals by approximately 90°

.

8. The digital receiver of claim 1, wherein:

the reference signals include first and second in-phase reference signals to be mixed with first and second digital data streams from corresponding first and second antenna elements to produce the I data streams, and

the reference signals include first and second quadrature reference signals to be mixed with first and second digital data streams from corresponding first and second antenna elements to produce the Q data streams, the first and second quadrature reference signals lagging behind their corresponding in-phase reference signals by approximately 90°

.

9. A method for controlling a receiver within an aircraft collision avoidance system, comprising:

receiving uncompressed, linear analog signals, from antenna elements located within a predetermined antenna element geometry;

converting each of the linear analog signals to uncompressed, linear digital data and outputting separate digital data streams corresponding to each of the input channels;

mixing the digital data streams with corresponding digital reference signals to produce digital In-phase (I) and Quadrature (Q) data streams associated with each of the antenna elements, the reference signals having phase differences there between; and

combining the I and Q data streams to form a directional or omni-directional beam-former data stream.

10. The method of claim 9, further comprising logarithmically converting the beam-former data stream to a log-video data stream, the beam-former data stream representing a non-logarithmic, non-compressed data stream prior to logarithmic conversion.

11. The method of claim 9, further comprising

summing the I data streams,

summing the Q data streams to form summed I and Q data streams, respectively, that are uncompressed and linear,

low-pass filtering the summed I data and the summed Q data streams to produce filtered I data and filtered Q data,

squaring the filtered I data and the filtered Q data to produce squared I data and squared Q data, and

summing the squared I data and squared Q data together to produce the beam-former data stream.

12. The method of claim 9, wherein the mixing includes accessing a plurality of look-up tables, each of the look-up tables storing a digital representation of the reference signal, the look-up tables being accessed at addresses that are offset with respect to one another in order to define a phase difference between the reference signals.

13. The method of claim 9, wherein the mixing includes producing digital oscillator signals representing the reference signals.

14. The method of claim 9, further comprising storing, in first and second look-up tables associated with one of the antenna elements, representations of a common reference signal, and accessing the first and second look-up tables in an offset manner that corresponds to a phase shift of approximately 90°

to form in-phase and quadrature reference signals.

15. The method of claim 9, further comprising storing, in a plurality of re-writable look-up tables, digital values defining the reference signal and accessing the look-up tables generally simultaneously in a generally sequential order to produce in-phase reference signals at a desired frequency, the phase of each in-phase reference signal being defined by the digital data values stored in one or more addresses of each look-up tables, and delaying each in-phase signal to produce quadrature reference signals which lag the in-phase reference signals by approximately 90°

.

16. The method of claim 9, further comprising:

mixing first and second in-phase reference signals with the first and second digital data streams from corresponding first and second antenna elements to produce the I data streams, and

mixing first and second quadrature reference signals with the first and second digital data streams from corresponding first and second antenna elements to produce the Q data streams, as a subset of the reference signals, the first and second quadrature reference signals lagging behind their corresponding in-phase signals by approximately 90°

.

17. A digital transmitter for an aircraft collision avoidance system, comprising:

a phase control module to generate digital reference counter values which includes a single phase accumulator as a reference of phase, the phase control module being programmable to adjust a frequency and phase of the reference counter-values;

phase-to-amplitude (P/A) module receiving the reference counter values and producing, based thereon, separate digital transmit signals for each of a plurality of antenna elements; and

digital-to-analog (D/A) converters converting the digital transmit signals to analog transmit signals to drive the antenna elements.

18. The transmitter of claim 17, further comprising a phase modulation control module connected to the single phase accumulator, the phase modulation control module introducing, into the reference counter values, a phase offset common to all channels that is operable to be used to modulate the phase of the transmitted signal.

19. The transmitter of claim 17, further comprising phase offset modules associated with each of the antenna elements, the phase offset modules introducing, into the reference counter values, offsets associated with corresponding ones of the transmit channels.

20. The transmitter of claim 17, further comprising programmable amplifiers associated with each of the antenna elements, the amplifiers adjusting a gain of the transmit signals for corresponding antenna elements.

21. The transmitter of claim 17, wherein the P/A modules include Look-Up Tables (LUTs) that store a digital representation of the transmit signals.

22. The transmitter of claim 17, wherein the P/A modules include Look-Up Tables (LUTs) that store a digital representation of the transmit signals, the reference counter values defining pointers into the LUTs to access addresses.

23. The transmitter of claim 17, wherein the P/A module includes a plurality of Look-Up Tables (LUTs), each of the LUTs storing a digital representation of the reference signal, the P/A module addressing the LUTs at addresses that are offset with respect to one another in order to define a phase difference between the transmit signals.

24. The transmitter of claim 17, wherein the transmit signals include first and second transmit signals to produce a phase relationship in transmit signals conveyed from first and second antenna elements in order to create a transmit signal pattern extending from the first and second antenna elements.