Showing papers on "Center frequency published in 1974"

An application of a hexagonal ferrite to a millimeter-wave Y circulator

Abstract: Hexagonal ferrite is used for a circulator at mm-wave frequencies. No external magnet is needed. The center frequency is 73.5 GHz, the bandwidth over which the isolation is greater than 20 dB is 2.4 GHz, and the insertion loss is 1.1 dB at the center frequency. The tensor permeability in a strong uniaxial field is determined. The dependence of the circulator bandwidth on an applied field is determined to show that the large uniaxial field of hexagonal ferrite contributes to the wideband performance at mm-wave frequencies.

Drift compensated phase lock loop

Abstract: A phase lock loop having a crystal voltage controlled oscillator (VCO) which includes a drift compensation mechanism incorporated in the feedback portion of the loop in order to track the difference between a reference input signal and the VCO center frequency which normally tends to drift with age. If the reference signal is lost, the compensation mechanism allows the apparent center frequency for the VCO to be held close to the last known reference value rather than the potentially drift affected real center frequency of the crystal.

Filter stabilized single oscillator transceivers

Abstract: A transceiver, adapted for use as either a master or a slave in a duplex pair, has a single, voltage-tunable, solid-state oscillator to provide the carrier frequency wave, a small portion of which is mixed with the received wave and applied therewith to a single ended mixer; an automatic gain-controlled loop cancels transmitter input modulation from the receiver output. The desired oscillator carrier frequency of the master transceiver is locked to a frequency within the pass band of an RF filter at the receiver input and separated from the center frequency of the filter by one-half the receiver IF frequency. The slave transceiver is first locked to a frequency within the pass band of the filter on the opposite side of its center frequency and separated therefrom by one-half the IF frequency (the slave thus offset from the master by their common IF frequency). Thereafter, upon sensing output from its IF amplifier (from the master), the slave is switched to operate in response to AFC developed by the received signal, such that the master and slave transceivers are locked together at frequencies differing by their common IF frequency. The RF filter also limits the signals to which the receiver can respond. An integrating amplifier provides demodulator and AFC filtering and, together with a bistable device, initial sweeping of the oscillator control voltage in respective directions depending on being in the master mode or the slave mode. Internal auxiliary modulation provides for pre-transmission transmitter modulation cancellation and frequency stability.

Frequency measurement by coincidence detection with standard frequency

Abstract: A method of measuring a desired frequency by comparing it with a standard frequency. The zero crossings of both frequencies are detected. A command pulse is generated at each coincidence and is used to start and stop a pair of frequency counters adapted to count the desired and standard frequencies. A measure of the desired frequency is obtained by multiplying the known standard frequency by the ratio between the desired count and the standard count obtained in the two frequency counters.

Arrangement for simultaneously producing signals having an increasing frequency and signals having a decreasing frequency

Abstract: An arrangement for simultaneously producing signals having a decreasing frequency and signals having an increasing frequency. In this arrangement the signals have frequencies which are complementary relative to the double value of a central frequency. The arrangement includes a pair of voltage-controlled oscillators controlled by signals supplied by a control generator. The arrangement is characterized in that for each oscillator there is provided with a phase control loop and that the control generator is of the digital type designed to supply two pairs of digital signals. One pair is applied to the frequency dividers and the other is applied to the oscillators so as to tune them to such a frequency that they are in the operating range of the phase control loop. Use: Radio-electric transmission of data.

Implication of transistor frequency dependence on intermodulation distortion

Abstract: An analysis is presented for third-order and second-order nonlinear distortion as a function of frequency for a transistor biased in the common-emitter configuration. It is found that, at high frequency, it is the curvature in the loaded cutoff frequency versus collector current curve that determines the degree of intermodulation distortion. Design proposals for obtaining linear cutoff frequency curves (i.e., small third-order distortion) will be discussed.

Method and means for coupling a multiplicity of surface acoustic wave transducers to a single electromagnetic wave transmission line

Abstract: The input transducers of a multichannel surface acoustic wave device are electrically connected in a series or series-parallel circuit arrangement and are connected to a single channel electromagnetic wave transmission line through an inductor. The inductance value of the inductor is chosen such that minimum transducer insertion loss is achieved at the center frequency of the midband channel. The circuit arrangement is selected which achieves optimum coupling to the midband channel subject to the constraint that the insertion losses of all the remaining channels, measured at their respective center frequencies, lie at or near the above optimum value within an acceptable prespecified margin.

Skirt-tuned single oscillator transceiver

Abstract: A transceiver, adapted for use as either a master or a slave in a duplex pair, has a single, voltage-tunable, solid state oscillator to provide the carrier frequency wave, a small portion of which is mixed with the received wave and applied therewith to a single ended mixer; an AGC-controlled loop cancels transmitter input modulation from the receiver output. The oscillator of the slave transceiver is locked to a desired carrier frequency by a feedback loop including a tuning cavity adjusted to the same frequency as that of the master transceiver; the slave transceiver is first locked to a frequency on the skirt of its tuning cavity, differing from the center frequency of its tuning cavity by the common IF frequency and thereafter, upon sensing output from its IF amplifier (from the master), is switched to operate in response to AFC controlled by the received signal, such that the master and slave transceivers are locked together at frequencies differing by their common IF frequency. A single integrating amplifier provides demodulator and AFC filtering and, together with a unilaterally-effective bistable device, initial sweeping of the oscillator control voltage to achieve skirt tuning in the slave mode or center tuning in the master mode.

Apparatus and method for oversampled transducers in acoustic surface wave devices

Abstract: Apparatus and method for providing electro-acoustic transducers of an acoustic surface wave device with an increased density of transducer elements. An increased density of transducer elements provides more accurate generation and reproduction of a desired frequency response above the design center frequency. By providing the sets of transducer elements which exchange signals by means of electro-acoustic surface waves with different densities of transducer elements, the transfer of undesired frequency components, introduced by the oversampled density of the transducer element sets, is reduced.

Closed loop variable frequency signal generator

Abstract: A frequency conversion circuit for use in frequency synthesizers, frequency counters, and similar apparatus. Frequency mixing means having first and second inputs is provided, an input frequency being applied to the first mixing means input and a stepping frequency being applied to the second mixing means input. The mixing means is responsive to the input frequency and the stepping frequency to provide an output signal having a frequency equal to the frequency difference between the input frequency and the stepping frequency, both when the input frequency is higher than the stepping frequency, and when the input frequency is lower than the stepping frequency. For a single stepping frequency, an identical mixing means output signal is thus provided for two input frequencies. Means are also provided for determining whether the input frequency is higher or lower than the stepping frequency. Such a circuit may be used in frequency synthesizers using phase-locked loops, for instance, to lock the loop to two different output frequencies with a single stepping frequency.

Information signal transmitting system

Abstract: OF THE DISCLOSURE An information transmitting system including a trans-mitter and at least one receiver The transmitter includes a modula-tor which is modulated by a first control signal intermittently, and whose center frequency is changed continuously in response to a second control signal The receiver is provided with a frequency dis-criminator which demodulates the first and second control signals and the first control signal is applied as a first remotely controllable signal in digital fashion and the second control signal is applied as a second remotely controllable signal in analog fashion in the receiver -i-

Automatically centered pulsed radar receiver

Abstract: Disclosed is a magnetron powered selectable pulsewidth radar system having minimum receiver bandwidth for each pulsewidth and automatic centering of the intermediate frequency at the true center of the input filter pass band. A frequency discriminator adjusts the local oscillator frequency after each transmitted pulse to cause the intermediate frequency on the return of that pulse to equal an internal adjustable frequency reference. The filtered IF noise signal between received pulses is compared to the internal reference by the frequency discriminator and its output is used to adjust the reference to equal the center frequency of the actual receiver input pass band.

Pulsed doppler radar device having at least one range channel

Abstract: A pulsed Doppler radar device with variable repetition frequency, having at least one range channel operatively connectable at the pulse rate of the pulse repetition frequency, a doppler filter which suppresses clutter interference in the low Doppler frequency range, and a device for the variation of the pulse repetition frequency, in which the doppler filter of each range channel comprises at least one sampling-and-holding circuit and a following high pass or band pass filter, the switching pulse rate of the sampling-and-holding circuit being changeable with changes in the pulse repetition frequency, with the same high pass or band filter being utilized for all repetition frequency variations, the cut-off frequency of the following filter, if a high pass filter or, the lower cut-off frequency of such filter, if a band pass filter being approximately equal to the upper frequency of the clutter band width whereby the latter is suppressed, and the upper cut-off frequency, if a band pass filter is employed, being above the maximum pulse repetition frequency.

Doppler navigation system with tracking filter for multipath discrimination

Abstract: A Doppler navigation system with tracking filter for reducing suceptibility to multipath signals. For acquisition of a Doppler ILS angle representing a signal within a spectrum also containing multipath signals, a self-tracking variable-Q filter arrangement is used, with wide band acquisition (low Q) followed by progressive steering of the filter center frequency to the desired signal frequency, together with decrease of the filter bandwidth to an equivalent of 2 beamwidths (high Q) at final balance.

Radio frequency notch filter

Abstract: A radio frequency notch filter includes a transformer secondary winding connected in series with a transmission line. The transformer primary winding is arranged with a capacitor to be parallel resonant at the filter center frequency. A reactive means is also connected in electrical shunt with the transmission line which responds at the notch frequency to drain current then traversing the secondary winding.

Wideband high-power TRAPATT circuits

Abstract: A lumped-circuit class-C amplifier operating at a center frequency of 2.8 GHz, and developing 75-W output at 6.1-dB gain with 18.7% efficiency, will be described.

IF Variable Equalizers for FM Microwave Radio Links

Abstract: The circuit configuration, operational principles, and some test data on three new types of equalizers applicable for use in FM microwave radio links are described. The equalizers are namely of the reflection type, frequency converter type, and AM-PM conversion type. The reflection type delay equalizer permits variation of relative delay time while keeping the absolute delay time constant at the center frequency or permits variation of absolute delay time while keeping the relative delay time constant. The frequency converter type equalizer adopts a principle whereby variation in local frequency (supplied to the frequency converter) facilitates continuous variation of the relative delay time, absolute delay time, and amplitude frequency response. The AM-PM conversion type differential gain equalizer enables equalization of differential gain through the combined use of the AM-PM converter circuit and the delay circuit.

Multifrequency linear filter networks with active elements

Abstract: A linear filter network incorporating active elements, and which obeys the relation ft ∝√G1 G2, where ft is the band-pass center frequency of the network; and G1 and G2 are the conductance values of certain network circuit elements, has its transfer function for bandpass output controlled by a group of switchable conductances (G1 G2) in a digitally-controllable switching system that reduces the number of conductances required to achieve a given number of discrete pass-bands all having the same, or constant, bandwidth. A network that is switchable among 10 or more frequencies is used in a tone-responsive paging system for response to one or more of a series of calling tones or frequencies that follow each other in equal frequency intervals or steps "Δf" chosen so that for a series of "n" steps no tone in the series is harmonically related to any of the others.

Crystal filtering device

Abstract: An IF crystal filter for frequency modulation receivers of the SCA (Subsidiary Communication Authorization) type, which receive signals utilizing relatively high modulating frequency subcarriers, is provided which includes, on a single circuit card, a phase splitter across its input terminals providing first and second signals of equal amplitude and opposite phase to an output resonant circuit tuned to a given center frequency through first and second resonant crystals, respectively, one resonant above and one resonant below that center frequency in equal amounts.

Burst Processor Tapped Delay Line.

Abstract: : ICS, Design, Acoustic surface wavesThe object of the program is to develop and demonstrate a doppler resolution filter configured as a tapped delay line. The device will operate at a center frequency of 220 MHz and a 50 MHz 1 dB bandwidth. The Burst Processor Tapped Delay Line geometry will use a parallel channel approach such that each delay output is derived from a separate acoustic channel. The device employs double electrodes for both input and tapping (output) transducers; the input consists of a simple, periodic transducer with six (6) double electrodes, while the outputs use novel 'phase-reversal transducers' with eleven (11) electrodes. The BPTDL also uses a 300 MHz reference channel which directly measures the time delay and controls the insertion phase by means of a temperature control system. The delay line design has been thoroughly analyzed and experimentally tested. Fabrication and evaluation of two prototype devices has been completed. (Modified author abstract)

IF variable equalizers for FM microwave radio links

Abstract: The circuit configuration, operational principles, and some test data on three new types of equalizers applicable for use in FM microwave radio links are described. The equalizers are namely of the reflection type, frequency converter type, and AM-PM conversion type. The reflection type delay equalizer permits variation of relative delay time while keeping the absolute delay time constant at the center frequency or permits variation of absolute delay time while keeping the relative delay time constant. The frequency converter type equalizer adopts a principle whereby variation in local frequency (supplied to the frequency converter) facilitates continuous variation of the relative delay time, absolute delay time, and amplitude frequency response. The AM-PM conversion type differential gain equalizer enables equalization of differential gain through the combined use of the AM-PM converter circuit and the delay circuit.

Electronically Programmable Inductorless Ladder Filters

Abstract: A technique is presented for the design of a programmable filter instrument in which the frequency response may be electronically programmed by an external analog or digital signal. The active ladder structure is used because the passband insertion loss is highly insensitive to element tolerances. The basis of the method is the selection of a set of electronically switched conductances within the general active ladder structure, which is directly related to the frequency domain characteristics of the transfer function. The frequency response is controlled by accurately programming the values of the conductances in this set. An instrument is presented which embodies these principles and illustrates the versatility which is possible with programmable active ladder structures.

Tunable Filters Using Charge Transfer Devices.

Abstract: : To date, CCDs have required complicated off-chip peripheral circuitry. The widespread application of CCDs to transversal filtering in systems depends on the integration of these circuits on the CCD chip. This report describes the design and performance of a completely self-contained and integrated 800-stage CCD transversal filter. The device contains the clock generator and drivers as well as the input and output circuits, so that only dc voltages and one master clock signal are required to operate the device. The chip is designed for general filtering applications and can be mask-programmed for a variety of different transfer functions. Its performance as a tunable bandpass filter with a 3 dB bandwidth of 0.7% of the center frequency and 40 dB sidelobe rejection is described. The center of the passband can be tuned from 500 Hz to 500 kHz. Key problems in the integration of the peripheral circuits have been related to the use of standard MOS circuits to perform these functions. To solve these problems, we have designed voltage amplifiers on this device. A CCD type of structure is used to obtain a differential sampled data voltage amplifier. These amplifiers are used both for the input stage and for the differential output of the filter. These amplifiers provide significant advantages over standard MOS circuits including good linearity, high speed, low power, low noise, and stable gain performance. Experimental results obtained with the bandpass filter are compared to predicted performance. (Author)

Exciter frequency ability system

Abstract: An exciter frequency agility system is disclosed which provides broad seption of carrier sidebands, enhancing microwave system agility while eliminating the need for tunable filters. Preselected, precisely controlled frequencies are combined to provide a high megahertz stable oscillator frequency. This stable frequency is split and directed along three distinct channels for selected combination with an output signal of a variable high frequency generator. In combining the stable frequency with the generated variable frequency, the channels are isolated from adjacent channels and recombined to provide two synchronized output frequency ranges. One frequency is coupled to the receiver front end, the other is transmitted toward the target. The two frequency ranges or bands are maintained a fixed high frequency apart while being variable within their respective ranges. The two signals are combined when the transmitted energy is reflected back to the receiver. Frequency spacing is of such magnitude that the received reflected energy, when recombined, is easily filtered with a bandpass filter to obtain intelligence therefrom.

Non-recursive filtering and the effect of sampling frequency

Abstract: The purpose of this paper is to design a low-pass filter by the Standard Fourier series method and to investigate analytically the effect of varying the sampling frequency for a given number of taps and cut-off frequency. It is shown that to achieve the sharpest cut-off one requires a sampling frequency as close to the Xyquist frequency as is permissible by aliasing and the filtering of higher harmonics of the transfer function.