Range-controlled variable gain device for pulse radar receiver

Claim 2

In a pulsed radar system including a radar transmitter and receiver, and a plurality of range selectors operated synchronously with the transmitted pulse of said system to sample the received video in a plurality of range increments comprising a predetermined portion of the interpulse period, a sensitivitytime control device comprising: a multi-stage ladder attenuator means having an input connected to receive video signals from said receiver, said ladder attenuator means having a plurality of taps providing increasing attenuation progressing along the stages thereof from said input; and connection means for connecting the inputs of said range selectors from said taps, in groups of at least one range selector per tap, and in an order such that the signal supplied to range selectors corresponding to the nearest ranges is supplied with the lowest effective gain and range selectors corresponding to farthest ranges is supplied with the greatest effective gain from the video output of said receiver.

Claim 3

Apparatus according to claim 1 in which said ladder attenuator means is divided into a plurality of sub-groups of said stages and a plurality of serially connected amplifier stages are provided and connected thereto, the input of the first of said amplifiers being connected to said receiver video signals, the output of the last of said serially connected amplifiers providing the input for the one of said attenuator sub-groups corresponding to range selectors sampling the latest received signals within said interpulse period, the inputs of the remaining sub-groups of said attenuator being connected to the interconnections of said serial amplifiers whereby the earliest received signals within said interpulse period are provided to the ones of said range selectors with the lowest effective gain from the video output of said receiver.

Claim 4

Apparatus according to claim 2 in which said attenuator means comprises only substantially non-reactive elements.

Claim 5

Apparatus according to claim 1 in which said attenuator means comprises only substantially non-reactive elements.

Claim 6

In a monopulse radar system having sum and difference receiving channels and which includes a plurality of range selectors operated synchronously with the transmitted pulse of said system to sample the received video in a plurality of range increments within a predetermined portion of the receiving period between successive transmitted pulses, a device for providing accurate equalization of signal amplitudes from said receiving channels as a function of echo range delay over said predetermined portion of the receiving period, the combination comprising: a pair of ladder attenuators connected to receive video signals, each from a corresponding one of said receiving channels, said ladder attenuators each having a plurality of taps providing increasing attenuation therealong from the input thereof; and connection means for each of said attenuators for supplying input video signals to corresponding range selectors, said means operating in each channel to connect the input of the range selector corresponding to the nearest in range of said range increments to the attenuator tap providing the greatest attenuation, the other inputs of said range selectors being connected to said taps in groups of at least one range selector input per attenuator tap, so as to provide for decreasing attenuation for said selectors according to increasing range of the corresponding range increments.

Claim 7

In a monopulse radar system having sum and difference receiving channels and which includes a plurality of range selectors operated synchronously with the transmitted pulse of said system to sample the received video in a plurality of range increments within a predetermined portion of the receiving period between successive transmitted pulses, a device for providing accurate equalization of signal amplitudes from said receiving channels as a function of echo range delay over said predetermined portion of the receiving period, the combination comprising: a pair of ladder attenuators connected to receive video signals, each from a corresponding one of said receiving channels, said ladder attenuators each having a plurality of taps providing increasing attenuation therealong from the input thereof; and connection means for each of said attenuators for supplying input video signals to corresponding range selectors, said means operating in each channel to connect the input of the range selector corresponding to the nearest in range of said range increments to the attenuator tap providing the greatest attenuation, the other inputs of said range selectors being connected to said taps in groups of at least one range selector input per attenuator tap, so as to provide for decreasing attenuation for said selectors according to increasing range of the corresponding range increments.

Claim 8

Apparatus according to claim 5 in which said attenuators have n stages, said taps are between said stages, and each of said stages provides an attenuation substantially equal to A/n, where A is the attenuation in decibels necessary over said predetermined portion of said interpulse period to provide an approximation of a fourth power signal-versus-range attenuation function in each of said sum and difference channels.

Claim 9

Apparatus according to claim 6 in which said attenuator means comprises only substantially non-reactive elements.