摘要:
An on-line noise figure measurement system for receivers that produces va results whether or not signals are being received. A narrow pulse having a low pulse repetition frequency and low amplitude is injected into the receiver. A processing circuit cyclically measures the output of the RF stage of the receiver to produce a ratio of two signal values. One value is measured in the absence of any signal entering the receiver while the other value is measured with only the pulse signal impressed on the receiver.
摘要:
A digital display system is provided for visually indicating the amplitude of a received signal. A plurality of reference signals incrementally graduated from a low amplitude to a high amplitude is applied as first inputs to a polarity of comparators and the received signal as applied as the second input. The comparators produce an output of polarity commensurate with the instantaneous difference between its inputs and a plurality of series-connected light emitting means, each connected between the outputs of two adjacent comparators, is responsive to a predetermined electrical potential for generating light energy so that the instantaneous amplitude level of the received signal is visually indicated by the actuation of a single such light emitting means at a time.
摘要:
A trim guard assembly apparatus to be used in combination with a vehicle body having an outer protective member, an inner base member, and a flexible, intermediate substantially hollow closure provided therebetween. The hollow closure may be selectively filled with or emptied of a fluid, thereby respectively expanding or retracting the protective member. In use, when in a parked position, the protective member is expanded thereby absorbing minor impacts such as outswung doors, protected shopping carts and the like. When the vehicle is in motion, the protective member is retracted, thereby reachieving aerodynamic streamlining of the automotive vehicle.
摘要:
A signal to be filtered is applied to a commutating filter which is contred by a tunable oscillator tuned to a desired filter frequency. The commutating filter includes a plurality of RC networks to which the input signal is sequentially connected. The output of the commutating filter is a series of discrete voltages from the capacitor sections and of the RC networks which are fed to an analog to digital converter. The resulting digital words produced by the converter are stored in a microprocessor and used to compute the spectral content of the input signal by means of the Discrete Fourier Transform. The computed output from the microprocessor represents the effect of the cascaded filter sections of the system.
摘要:
An RF test signal generator including a driving oscillator, a pulse generr for generating narrow spikes at the oscillator frequency (such as a step recovery diode), a modulator and an attenuator. Since the very narrow pulse exhibits nearly constant amplitude in the frequency domain, a constant amplitude comb spectrum with frequency spacing at the oscillator frequency is generated so as to facilitate automated testing techniques.
摘要:
A modulated signal is injected into receiver under test. The output of theeceiver is fed directly to a first power measuring device and through a digital filter to a second measuring device. The two measured quantities are fed to a divider circuit which provides an output proportional to signal to signal and noise ratio.
摘要:
An apparatus is described for converting the carrier frequency of a moduld signal sampled from the output of an RF transmitter. The conversion provides a replica of the modulated signal at a predetermined center frequency without regard to the selection of a transmitter channel or to the modulation technique used. The replica is presented to a demodulator which provides an information signal suitable for monitoring the quality of modulation of the transmitted signal.
摘要:
A device for generating a plurality of RF signals, all possessing identicalodulation characteristics. A clock source triggers an oscillator to produce a precise pulse train that is filtered and fed to a first double balanced mixer for mixing with the output of a variable frequency oscillator. This output signal is then fed to a second double balanced mixer for mixing with additional modulation inputs which may be Am, FM, PSK and FSK.
摘要:
An analyzer for analyzing radio frequency signals from an FM/PM transmitterithout prior knowledge of the transmitting frequency. The RF signal is sampled and fed to a mixer where it is mixed with the output from a comb generator having a PRF equal to the transmitter channel spacing. The signal out of the mixer is filtered to remove all but the desired frequency components. The filtered signal is fed to a frequency discriminator which provides a demodulated form of the transmitted RF signal and is fed to various parameter indicators.
摘要:
A step recovery diode pulse generator is driven by a fixed frequency oscitor to provide pulses which are modulated in a balanced modulator by means of a voltage controlled oscillator controlled by a variable frequency input. The output of the balanced modulator is attenuated and provides a frequency modulated RF signal output.