A multiple frequency radar system having improved signal-to-clutter performance. A transmitter responsively coupled to a spacing frequency generator transmits a plurality of mutually coherent frequencies uniformally spaced apart in frequency. An associated non-linear receiver includes a phase detector responsive to the spacing frequency generator for coherent processing of receiver signals provided in response to echoes of the transmitted signal.
A multichannel coherent receiver employing multiple delay lines in series or a tapped delay line into which a received signal band is introduced. The signal band at each tap or increment of delay is mixed with individual related frequencies and the product from the mixers summed and further mixed with the output of a swept oscillator. The composite delayed signal band is introduced into a bank of dispersive filters followed by means for deriving in-phase and quadrature components. Signals contained within the signal band may then be detected resulting in coherent channelization, improved frequency resolution and full time coverage sampling.
The concept of nonlinear coherence employed in carrier tracking to improve telecommunications efficiency is disclosed. A generic tracking loop for a coherent receiver is shown having seven principle feedback signals which may be selectively added and applied to a voltage controlled oscillator to produce a reference signal that is phase coherent with a received carrier. An eighth feedback signal whose nonrandom components are coherent with the phase detected and filtered carrier may also be added to exploit the sideband power of the received signal. A ninth feedback signal whose nonrandom components are also coherent with the quadrature phase detected and filtered carrier could be additionally or alternatively included in the composite feedback signal to the voltage controlled oscillator.
A receiver for angle-modulated signals of the type a sin((ω)t+φ(t)), comprising a frequency transposition stage (3) incorporating a local oscillator (3-1). A frequency shift Δω of the local oscillator relative to the carrier frequency ω may cause the angle modulation signal φ(t) to become faded. An argument detector (4) produces the signal [φ(t)+(Δω)t] which is differentiated by a differentiator (6) to provide the signal [dφ(t)/dt+Δω]. A DC-shift detector (7) determines the DC-component Δω of this signal. This component is integrated by an integrator (8) to provide the signal (Δω)t, which is thereafter subtracted by difference producer (5) from the output signal of the argument detector (4) to provide a clear angle modulation signal.
A digital radio receiver generates coherent signals for synchronous detection without use of a phase-locked loop by employing an adaptive notch filter to cancel the desired signal. The cancelling signal is employed as the coherent signal for synchronous detection. The invention obtains faster locking to the desired signal, a wider capture range, and more efficient software coding in a digital signal processing receiver.
According to the present invention a method and a receiver for high-frequency signals is provided. The receiver comprises a power divider to divide a modulated RF input signal in at least two branches. At least one delay line provides for a delay of the branches relatively to each other by a predetermined delay constant. A calculation circuit calculates at least three power levels based on combinations of the two branches of the input signal relatively delayed to each other. A processing means calculates the phase and the amplitude of a complex signal representing the relation between the two branches of the input signal relatively delayed to each other, on the basis of the said at least three power levels.
In a radar system having a transmitter that produces pulses to be radiated by an antenna and a receiver that detects target information, complex demodulation is performed on an attenuated and limited waveform of the transmitter produced pulse. A matched filter is generated responsive to the complex demodulated waveform that is a time reversed conjugate image of the waveform corresponding to the produced pulse. Complex demodulation is performed on the return signal received by the receiver corresponding the produced pulse and the complex demodulated return signal is correlated with the matched filter that corresponds to the time reversed conjugate image of the waveform of the produced pulse.
A civil aviation passive coherent location system and method is disclosed. A receiver subsystem receives reference transmissions from an uncontrolled transmitter. The receiver subsystem also receives scattered transmissions originating from the uncontrolled transmitter and scattered by an airborne object. The received transmissions are compared to determine measurement differentials such a frequency-difference-of-arrival, a time-difference-of-arrival and an angle of arrival. From the measurement differentials, an object state estimate is determined. A previous state estimate may be updated with the determined state estimate. Processing subsystems determine the measurement differentials and state estimates.
A system incorporates time-hopped impulse radio (TH-IR) and transmitted-reference impulse radio (TR-IR) transceivers in the same wireless network. A transmitter modulates a sequence of bits in a wireless communications network by generating a reference waveform and a data waveform of a waveform pair for each current bit. The phase of the reference waveform depends on a previous modulated bit, and a difference in phase between the reference waveform and the data waveform pair depend on the current bit. A symbol period for the current bit is partitioned into multiple time intervals, and the reference waveform and the data waveform are encoded in a selected one of the time intervals that depends on the current bit.
symbol clock associated with a symbol stream in a synchronized communication receiver can be recovered by adjusting the phase of a symbol clock signal. The phase adjustment is accomplished by applying a digitally controlled delay to the symbol clock signal based on a timing relationship between the symbol clock and symbol transitions in the symbol stream.