TRUE TIME DELAY PHASE ARRAY RADAR USING ROTARY CLOCKS AND ELECTRONIC DELAY LINES

• US 20120039366A1
• Filed: 06/06/2006
• Published: 02/16/2012
• Est. Priority Date: 06/06/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Mobius Power, LLC
• Inventors: Wood, John, Basit, Haris
• Granted Patent: US 8,629,807 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 7/03 Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
• CPC Class Codes: G01S 7/403 in azimuth, i.e. in the horizontal plane
• CPC Class Codes: G01S 7/4034 in elevation, i.e. in the vertical plane
• CPC Class Codes: H01Q 3/2694 using also variable phase-shifters H01Q3/2688 takes precedence
• CPC Class Codes: H01Q 3/42 using frequency-mixing H01Q3/2676 takes precedence
• CPC Class Codes: H03B 5/1852 the semiconductor device being a field-effect device

Abstract

Local oscillator circuitry for an antenna array is disclosed. The circuitry includes an array of rotary traveling wave oscillators which are arranged in a pattern over an area and coupled so as to make them coherent. This provides for a set of phase synchronous local oscillators distributed over a large area. The array also includes a plurality of phase shifters each of which is connected to one of the rotary oscillators to provide a phase shifted local oscillator for the array. The phase shifter optionally includes a cycle counter that is configured to count cycles of the rotary oscillator to which it is connected and control circuitry that is then operative to provide a shifted rotary oscillator output based on the count from the cycle counter. A system and method for operating a true-time delay phased array antenna system. The system includes a plurality of antenna element circuits for driving or receiving an rf signal from the elements of the array. Each element circuit has a transmit and a receive path and a local multiphase oscillator, such as a rotary traveling wave oscillator. Each path has an analog delay line for providing a true-time delay for the antenna element. Preferably, the analog delay line is a charge coupled device whose control nodes are connected to phases of the local multiphase oscillator to implement a delay that is an integer number local multiphase oscillator periods. A fractional delay is also included in the path by using a sample and hold circuit connected to a particular phase of the oscillator. By delaying each antenna element by a true time delay, broadband operation of the array is possible.

Claims

1. A local oscillator system for a phased array antenna, the oscillator system comprising:

a plurality of rotary traveling wave oscillators, each having a plurality of phase taps, said plurality disposed over an area and coupled so as to make the oscillators coherent; and

a plurality of phase shifters, each providing a local oscillator signal with a selected phase for a phased array antenna, each phase shifter being located proximate to one of the rotary oscillators and being connected to a plurality of phase taps of the proximate oscillator, each phase shifter receiving control information to select one of the phase taps for output as the local oscillator signal.

2. A local oscillator system as recited in claim 1, wherein the oscillators are made coherent by injection locking.

3. A local oscillator system as recited in claim 1,

wherein each phase shifter further includes a cycle counter for counting clock cycles of the proximate oscillator;

further comprising synchronization logic for initializing the cycle counters simultaneously; and

wherein the phase shifter selects one of the phase taps as the local oscillator signal based on the cycle counter so as to provide the local oscillator signal at the selected phase for one or more counts of the cycle counter.

4. A local oscillator system as recited in claim 3, wherein the synchronization logic includes:

a pipeline having a total number of stages, each stage providing signal for initializing one of the counters, the total number of stages being approximately equal to the number of oscillator clocks needed to propagate a signal over the area spanned by the rotary oscillators; and

a plurality of delay circuits, each delay circuit connected between a pipeline stage and a counter and providing a delay in oscillator clocks of the initialization signal at the stage to which the delay circuit is connected, the delay being the difference between the total number of stages and the number of the delay stage at which the delay circuit is connected.

5. A phased array antenna system comprising:

a plurality of antenna elements arranged in a pattern, for receiving radio-frequency signals;

a plurality of down-converters each connected to one of the antenna elements to receive the radio-frequency signal captured by the antenna element, each down converter operative to down-convert the received radio-frequency signal using a local oscillator signal having a selected phase;

a signal combining network for combining the down-converted signals generated by the down-converters to produce an output signal;

a rotary oscillator array for providing local oscillator signals each with a selected phase to each of the down-converters based on control information; and

a control unit for providing the control information to the rotary oscillator array to obtain the phase-shifted local oscillator signals.

6. A phased array antenna system as recited in claim 5, wherein the rotary oscillator array includes:

a plurality of rotary traveling wave oscillators disposed over an area and coupled so as to make the oscillators coherent; and

a plurality of phase shifters each providing a local oscillator signal with a selected phase to one of the down converters, each phase shifter being located proximate to one of the rotary oscillators and being connected to a plurality of phase taps of the proximate oscillator, each phase shifter receiving control information from the control unit to select one of the phase taps for output as the local oscillator signal.

7. A phased array antenna system as recited in claim 6, wherein the oscillators are made coherent by injection locking.

8. A phased array antenna system as recited in claim 6,

wherein each phase shifter further includes a cycle counter for counting clock cycles of the proximate oscillator;

wherein the control unit includes synchronization logic for initializing the cycle counters simultaneously and provides control information for controlling the use of the cycle counters by the phase shifters; and

wherein the phase shifter selects one of the phase taps as the local oscillator signal based on the cycle counter and cycle count control information from the control unit so as to provide the local oscillator signal at the selected phase for one or more counts of the cycle counter.

9. A phased array antenna system as recited in claim 8, wherein the synchronization logic includes:

a pipeline having a total number of stages, each stage providing signal for initializing one of the counters, the total number of stages being approximately equal to the number of oscillator clocks needed to propagate a signal over the area spanned by the rotary oscillators; and

a plurality of delay circuits, each delay circuit connected between a pipeline stage and a counter and providing a delay in oscillator clocks of the initialization signal at the stage to which the delay circuit is connected, the delay being the difference between the total number of stages and the number of the delay stage at which the delay circuit is connected.

10. A phased array antenna system comprising:

a plurality of antenna elements arranged in a pattern, for sending radio-frequency signals;

a plurality of up-converters, each connected to one of the antenna elements to send a radio-frequency signal, each up-converter operative to up-convert the an input signal to a radio-frequency signal using a local oscillator signal having a selected phase;

a signal distribution network for distributing the input signals to the up-converters;

a rotary oscillator array for providing local oscillator signals each with a selected phase to each of the up-converters based on control information; and

a control unit for providing control information to the rotary oscillator array to obtain the phase-shifted local oscillator signals.

11. A phased array antenna system as recited in claim 10, wherein the rotary oscillator array includes

a plurality of rotary traveling wave oscillators disposed over an area and coupled so as to make the oscillators coherent;

and

a plurality of phase shifters each providing a local oscillator signal with a selected phase to one of the up-converters, each phase shifter being located proximate to one of the rotary oscillators and being connected to a plurality of phase taps of the proximate oscillator, each phase shifter receiving control information from the control unit to select one of the phase taps for output as the local oscillator signal.

12. A phased array antenna system as recited in claim 11, wherein the oscillators are made coherent by injection locking.

13. A phased array antenna system as recited in claim 11,

wherein each phase shifter further includes a cycle counter for counting clock cycles of the proximate oscillator;

wherein the control unit includes synchronization logic for initializing the cycle counters simultaneously and provides control information for controlling the use of the cycle counters by the phase shifters; and

wherein the phase shifter selects one of the phase taps as the local oscillator signal based on the cycle counter and cycle count control information from the control unit so as to provide the local oscillator signal at the selected phase for one or more counts of the cycle counter.

14. A phased array antenna system as recited in claim 13, wherein the synchronization logic includes:

a pipeline having a total number of stages, each stage providing signal for initializing one of the counters, the total number of stages being approximately equal to the number of oscillator clocks needed to propagate a signal over the area spanned by the rotary oscillators; and

a plurality of delay circuits, each delay circuit connected between a pipeline stage and a counter and providing a delay in oscillator clocks of the initialization signal at the stage to which the delay circuit is connected, the delay being the difference between the total number of stages and the number of the delay stage at which the delay circuit is connected.

15. A method of providing a plurality of local oscillator signals for a phased array, the method comprising:

providing a plurality of rotary traveling wave oscillators, disposed over an area;

coupling the oscillators so as to make the oscillators coherent;

locating each of a plurality of phase shifters proximate to one of the rotary oscillators;

connecting the phase shifter to a plurality of phase taps of the proximate oscillator; and

receiving control information to select one of the phase taps for output as a local oscillator signal for the phased array.

16. A method of providing a plurality of local oscillator signals for a phased array as recited in claim 15, wherein coupling the oscillators so as to make the oscillators coherent includes injection locking each oscillator with its neighboring oscillators.

17. A method of providing a plurality of local oscillator signals for a phased array as recited in claim 15,

wherein each phase shifter includes a cycle counter that counts cycles of the proximate oscillator;

and

further comprising;

prior to receiving control information to select one of the phase taps, synchronizing the cycle counters in each of the phase shifters; and

receiving control information to enable the local oscillator signal as an output for one or more cycles of the cycle counter.

18. A method of providing a plurality of local oscillator signals for a phased array as recited in claim 17, wherein the step of synchronizing the cycle counters includes:

transmitting a reset signal through a total number of pipeline stages disposed over the area; and

delaying the reset signal provided at a particular stage an amount in clock cycles equal to the difference between the total number of stages and the delay at the particular stage; and

using each delayed signal to reset one of the counters.

19. A phased array antenna system comprising:

a plurality of antenna elements;

a plurality of transceiver blocks, each connected to one of the antenna elements and to an rf port, each transceiver block including a transmit path through which a signal to be transmitted travels to the connected antenna element,

the transmit path including a true time delay of the signal to be transmitted, a receive path through which a received signal travels from the connected antenna element,

the receive path including a true time delay of the signal received, a local multiphase oscillator for supply timing signals to the transmit and receive paths, and a pair of switches for selectably coupling either the transmit path or the receive path between the rf port and the connected antenna element;

a distribution and collection network connected to the transceiver block, for distributing the rf signals to be transmitted and for collecting the rf signals received; and

a controller for providing digital control signals to the transceiver blocks.

20. The phase array antenna system of claim 19, wherein the local multiphase oscillator is a rotary traveling wave oscillator.

21. The phase array antenna system of claim 19,

wherein the plurality of transceiver blocks are arranged in a plurality of subarrays and the plurality of subarrays are collected together to form a main array;

wherein the distribution and collection network includes, in each subarray, an H-tree that distributes and collects the rf signals; and

wherein each subarray includes an array of synchronized multiphase oscillators, the array providing timing signals for the transceiver blocks.

22. The phase array antenna system of claim 21, wherein the array of synchronized multiphase oscillators is an array of rotary traveling wave oscillators.

23. The phase array antenna system of claim 21, wherein the H-tree includes a plurality of transmission lines arranged in an ‘

H’

-like configuration and connected to each of the transceiver blocks in the subarray.

24. The phase array antenna system of claim 19,

wherein the plurality of transceiver blocks are arranged in a plurality of subarrays and the plurality of subarrays are collected together to form a main array;

wherein the distribution and collection network includes, in each subarray,

a frequency synthesizer for waveforming an rf signal and a D/A converter that converts the rf signal to an analog signal to be transmitted,

an A/D converter that converts the received rf signal to a digital signal on the distribution and collection network, and

a digital summer for combining the received rf digital signals; and

wherein each subarray includes an array of synchronized multiphase oscillators, the array providing timing signals for the transceiver blocks.

25. The phase array antenna system of claim 24, wherein the array of synchronized multiphase oscillators is an array of rotary traveling wave oscillators.

26. The phase array antenna system of claim 19, wherein the transmit path includes:

an analog delay line for time delaying an rf signal on the rf port in response to the timing signals from the local multiphase oscillator,

a S/H circuit connected to the analog delay line for adding a fractional delay to the delayed rf signal in response to a timing signal from the local multiphase oscillator, and

a power amplifier for boosting the signal from the S/H circuit and for driving the antenna element.

27. The phase array antenna system of claim 26, wherein the analog delay line is a CCD having control inputs connected to the timing signals from the local multiphase oscillator.

28. The phase array antenna system of claim 27, wherein the local multiphase oscillator is a rotary traveling wave oscillator.

29. The phase array antenna system of claim 19, wherein the receive path includes:

a low noise amplifier for boosting the received signal,

a S/H circuit connected to the low noise amplifier, for adding a fractional delay to the received signal in response to a timing signal from the local multiphase oscillator, and

an analog delay line for time delaying the signal from the S/H circuit in response to the timing signals from the local multiphase oscillator.

30. The phase array antenna system of claim 29, wherein the analog delay line is a CCD having control inputs connected to the timing signals from the local multiphase oscillator.

31. The phase array antenna system of claim 30, wherein the local multiphase oscillator is a rotary traveling wave oscillator.

32. An antenna element circuit for providing a true time delay, the circuit comprising:

an rf port for sending or receiving rf signals;

an antenna element port for connecting to an antenna element;

a transmit path through which a signal to be transmitted travels to an antenna element, the transmit path including an analog delay line for time delaying an rf signal on the rf port in response to transmit delay line timing signals, a S/H circuit connected to the analog delay line for adding a fractional delay to the delayed rf signal in response to a transmit sample and hold timing signal, and a power amplifier for boosting the signal from the S/H circuit and for driving the antenna element;

a receive path through which a received signal travels from an antenna element, the receive path including a low noise amplifier for boosting the received signal, a S/H circuit, connected to the low noise amplifier, for adding a fractional delay to the received signal in response to a receive sample and hold timing signal, and an analog delay line for time delaying the signal from the S/H circuit in response to receive delay line timing signals;

local multiphase oscillator for supplying the transmit and receive delay line timing signals and the transmit and receive sample and hold timing signals; and

a pair of switches for selectably coupling either the transmit path or receive path between the rf port and the antenna element.

33. An antenna element circuit as recited in claim 32, wherein the local multiphase oscillator is a rotary traveling wave oscillator.

34. A method for applying a true time delay to an analog rf signal, the method comprising:

delaying the analog rf signal by an integer number of periods of a multiphase oscillator that provides a plurality of phase signals, each oscillating with the period of the multiphase oscillator; and

capturing the delayed rf signal in a S/H circuit and delaying the captured signal by a fractional delay in response to a timing signal from the multiphase oscillator, the fractional delay being a delay determined by a selected one of the phase signals of the multiphase oscillator.

35. A method as recited in claim 34, wherein the step of delaying the analog rf signal is performed by passing the rf signal through a charge coupled device having control nodes that are connected to the phase signals of the multiphase oscillator.

36. A method as recited in claim 35, wherein the local multiphase oscillator is a rotary traveling wave oscillator.