Abstract: A frequency modulation (FM) radio transmitter, such as a cellular telephone, includes an automatic deviation control system to automatically compensate for varying sensitivity of the FM transmitter. The FM transmitter includes a phase lock loop including a controlled oscillator that produces a frequency modulated input signal on an output channel frequency in response to a control input that is applied thereto. A scaler is responsive to the input signal and to at least one scaling content, to scale the input signal based upon the at least one scaling constant and to provide the scaled input signal to the phase lock loop to produce the frequency modulated input signal on the channel frequency. An automatic deviation control system measures the control signal that is applied to the controlled oscillator when tuned to one of the plurality of output channel frequencies and updates at least one of the scaling constants based upon the measured control input, to thereby provide automatic deviation control.

Abstract: The present invention, generally speaking, provides an RF modulator that allows precise, stable phase shifts to be obtained. The modulator uses a PLL structure including an auxiliary feedforward path used to inject a baseband modulation signal into the PLL at a point past a loop filter of the PLL. A phase demodulator recovers phase information from the output signal of the PLL. The recovered phase information is compared to the phase information of the baseband modulation signal. A resulting error signal is used to control injection of the baseband modulation signal into the PLL, to automatically achieve the correct "dosage." A precise, adaptive, phase-stable modulator results. The adaptation of the modulator compensates for variability of the VCO and other components of the PLL.

Abstract: A radio communication device, suitable for use in a portable computer, is capable of operating at any one of a set of common frequencies which are legally permissible in all countries (or a set of countries) and at any frequency on which it detects that a transmission of its own type is being used for a transmission from another device. Thus, users can legally operate the device in different countries, while manufacturers can obtain certification for use in those countries. If the user attempts to select a frequency which is not one of the common frequencies nor detected by transmission, an indication that such frequency is not available is provided to the user.

Abstract: A broadcast transmitter for generating low power modulated signals, especially for a wireless speaker system. A signal source such as a source of composite audio signals including left and right audio signals and a pilot signal are applied to a radio frequency signal oscillator. The radio frequency signal oscillator includes a bipolar transistor connected in a common base configuration, and having a stripline element as a frequency determinative component in the collector circuit of the bipolar transistor. The modulating signal is applied to the base of the bipolar transistor which modulates the collector junction capacitance of the transistor thereby frequency modulating the signal produced by the oscillator. Varactor tuning is provided for setting a nominal frequency of oscillation.

Abstract: A method and a transmitter system is provided for modulating binary information on a frequency shift keying carrier in a very narrow band. Phase reversal keying is initially used to create a carrier. The transmitter of the present invention generates a carrier signal by modulating a reference signal and a control signal having two frequencies representing the binary data to be transmitted. The resulting phase reversal carrier signal is processed by high order filtering such that the output of the transmitter provides a frequency shift keyed carrier at very close frequencies. The resulting carrier signal may, at the receiver, be processed by very narrow band filtering so as to create a communication system which will use only a small part of the available spectrum.

Abstract: The output of a voltage-controlled oscillator (VCO), after being passed through a resonator having a single-peak characteristic, is detected by a detector. The output of the detector is sampled and held at a time instant that the control input voltage to the VCO reaches a maximum and also at a time instant that it reaches a minimum, and the difference between them is fed back to the control input of the VCO. In this way, the center frequency of the VCO is controlled so that it becomes equal to the center frequency of the resonator. In the case of a VCO as an FM modulator in an FM-CW radar, the sample-and-hold timing is derived from a clock signal based on which a triangle wave is generated. In the case of a VCO as an FSK modulator, the sample-and-hold timing is obtained by detecting a 0 and a 1 in input data.

Abstract: A transmitter which can easily suppress diffusion of a spurious signal with a simple constitution, wherein the on/off operations of the transmitting circuit and the carrier signal generating circuit are controlled by the first control signal which rises at the predetermined timing and falls at the predetermined timing, and the on/off operation of the modulator is controlled by the second control signal which gently rises at the same or later timing than the rise timing of the first control signal and gently falls at the same or earlier timing than the fall timing of the first control signal, so that a phenomenon which is similar to pulse modulation of the leaked carrier signal fc becomes hard to be generated, therefore diffusion of the spurious signal can be suppressed.

Abstract: The present invention relates to a wireless communication system having improved PLL circuits in the RF transmitter and receiver sections. The PLL circuits in the wireless communication system according to the present invention include time constant controllable filters. A series circuit of capacitor and resistor detects turn-on of the power switch for the PLL circuits to generate an output signal to be applied to the filters, thereby controlling the time constant of the filters in the PLL circuits to a lower value than normal for a given time after power-on of the PLL circuits.

Abstract: A first phase-locked loop (PLL) includes a first integrated voltage-controlled oscillator (VCO) whose output signal has a frequency modulated by an input signal of the device about a multiple of a reference frequency. A second PLL includes a second integrated VCO and frequency transposition means. The transposition circuit receive the output signal of the second VCO and a transposition signal having a non-modulated frequency. The second PLL addresses to the second VCO a control signal capable of aligning the frequency of the output signal of the transposition circuit with the frequency of the first VCO. The output signal of the second VCO forms the frequency modulation transmission signal produced by the device.

Abstract: A remote ground terminal transmitter for transmitting a modulated data signal having a constant envelope amplitude. The remote ground terminal transmitter comprises a source of data signals, a modulator for providing a carrier signal, receiving a data signal from the source of data signals, and modulating the carrier signal with the received data signal so as to produce a constant envelope minimum shift key modulation signal. The transmitter further comprises a power amplifier which operates in the saturation mode to amplify the modulated carrier signal produced by the modulator to the desired power level.

Abstract: A frequency modulator controls the center frequency and modulation factor at the same time with one control signal. The frequency modulator includes a voltage-to-current converter that receives an input voltage signal to be modulated, a reference voltage signal, and a control voltage signal, and generates an output current signal by combining the input voltage signal and the control voltage signal. The input voltage signal is amplified by a transconductance amplifier. The control voltage signal is converted into a gain signal which is used to vary the transconductance of the amplifier. A voltage controlled oscillator generates a frequency modulated signal responsive to the output current signal. The center frequency and modulation factor can be controlled by adjusting the value of a resistor in the current-to-voltage converter, a capacitor in the voltage control oscillator, or the control voltage signal.

Abstract: A method an apparatus for controlling frequency of a multi-channel transmitter. A reference frequency is generated and emitted to a thermally stable frequency discriminator. The thermally stable frequency discriminator emits a dc voltage to a plurality of individual oscillators. The individual oscillators in continuous wave mode or modulated by baseband signals are combined into a multi-channel signal at an intermediate range of frequencies. The multi-channel intermediate range of frequencies are preferably amplified and emitted as an output signal. At relatively lower frequencies, such as 4-6 GHz, up-conversion of the output signal is not necessary. At relatively higher frequencies, an up-converter can be used to employ a second thermally stable frequency discriminator.

Abstract: A calibrated VHF/FM source for use in correcting tape recorder and receiver rrors which consolidates these functions in a lightweight rack using commercial test parts and maintains a high precision of accuracy by having the system monitor it's own output and correct the distortion and amplitude errors attributable to the nonlinear behavior of the a Voltage Variable Capacitance diode (VVC diode) of the Voltage Capactive Oscillator (VCO) of the VHF FM transmitter.

Abstract: A selective call receiver (100) for receiving and transmitting paging signals has a transceiver (104) having an integer divide synthesizer (105) for achieving a fast lock time. The transceiver (104) has a reference oscillator (202) that generates a reference signal in a direct injection path and a modulator (206) coupled in the direct injection path modulates the reference signal to generate a modulated reference signal. A phase locked offset loop (220) coupled to the direct injection path generates a low frequency signal derived from the reference signal, a multiplier (210) coupled to the modulator (206) multiplies the modulated reference signal, and a mixer (214) coupled to the multiplier (210) receives the modulated reference signal in the direct injection path and an output signal from the phase locked offset loop (220) to generate a first local oscillator output signal and a modulated transmit carrier.

Abstract: In the frequency synthesizer, the stable transmission frequency required by the digital operating mode is created from a frequency produced by a free running oscillator and which includes frequency errors. A local frequency (f.sub.1) and an intermediate frequency (f.sub.IF) including frequency errors are input to a mixer (105) located in the signal path of the transmitter. A transmission frequency transmission signal (f.sub.TX) is input to a phase-lock loop with a voltage-controlled oscillator (103) that produces the local frequency (f.sub.1). Thereby the frequency error caused by the intermediate frequency (f.sub.IF) can be corrected with the local frequency (f.sub.1) by adjusting the voltage-controlled oscillator (103) of the loop with a voltage (V.sub.D) that is proportional to the phase difference between the transmission frequency signal and a reference signal (V.sub.REF) input to a phase comparator.

Abstract: Reduction of transmitter exciter chain generated noise from the receive bank of a portable/hand-held duplex transceiver is achieved using a high output power, low-noise voltage-controlled-oscillator (VCO) in the transmitter exciter chain. Using this high-power, low-noise oscillator as the RF source in the transmitter exciter chain precludes the need for the conventional buffer/driver amlplifier stage and an associated inter-stage noise filter. Elimination of buffer/driver stage components and bulky inter-stage noise filter components allows complete integration of transmitter exciter chain components resulting in reduced size and cost.

Abstract: A DC frequency modulation circuit for modulating audio signals wherein the high frequencies of the audio signals are modulated by a first phase locked loop and the low frequencies of the audio signals, along with the DC signals, are filtered by a low pass filter, applied through an A/D converter, and modulated by a direct digital frequency synthesizer. The two modulated signals are then mixed by a second phase locked loop.

Abstract: A digital frequency shift keying (FSK) transmitter provides direct frequency modulation in a wide bandwidth loop. In one embodiment, a discriminator circuit recovers from the output signal of the transmitter a base band signal, which is then compared with the input base band signal to provide an error signal for controlling the output oscillator circuit. In another embodiment, the output oscillator is controlled by a phase detector detecting the phase difference between the base band modulating signal and the output signal of the transmitter. An additional narrow bandwidth loop can be added to compensate for frequency drift in the output oscillator due to temperature or other environmental changes.

Abstract: A relaxation oscillator of reduced complexity is described which can be constructed as part of a silicon integrated circuit. The current controlled oscillator includes complementary field effect transistors operating in enhancement mode. The drain of one FET is connected to the gate of the other FET and vice versa. The resulting CMOS circuit functions as a four-layer diode. A resistor is connected between the drains of both transistors. A storage capacitor is connected between the sources of both transistors. A current source is connected to charge the storage capacitor such that the frequency of an oscillator output signal is determined by the current generated by the current source.

Abstract: A transceiver (10) includes a dual port phase and magnitude balanced synthesizer modulator (60). The modulator (60) couples a modulation input to a voltage controlled oscillator (40) and to a reference oscillator (42) that are coupled together in a phase locked loop (44). The modulator 60 includes a magnitude balancing circuit (64) that divides a modulation input representing data or the like into a first modulation input signal applied to the reference oscillator (42) and a second modulation input signal for the voltage controlled oscillator (40). A phase balancing circuit (68) induces a negative phase shift in the second modulation input signal that is coupled to the voltage controlled oscillator (40) in order to compensate for the phase lag of the reference oscillator loop (44).

Abstract: A transmitter of a radio communication apparatus includes a voltage controlled oscillator for converting a voltage signal input to the transmitter into a signal having a frequency according to the voltage of the voltage signal, a mixer for mixing a signal having a fixed frequency with the converted input signal and generating a signal for transmission having a frequency at which communication is substantially carried out, a frequency detector for detecting the frequency at which communication is substantially carried out, and a filter for eliminating useless signals that are included in the signal for transmission and have frequencies different from the frequency at which communication is substantially carried out. Signals having frequencies different from the frequency at which communication is substantially carried out are not radiated into space.

Abstract: A method and apparatus in a radio communication transmitter (600) stabilizes a carrier frequency locked to a reference oscillator (102). The reference oscillator (102) is controlled by a control signal and generates a first signal at a reference frequency. The first signal is coupled to a frequency multiplier (212) for multiplying the reference frequency by a predetermined factor to generate a second signal at the carrier frequency. Cycles of the carrier frequency are counted (508, 514) during a predetermined interval to determine (516, 518) a measured cycle count. The measured cycle count is compared (520) with an expected cycle count corresponding to a predetermined carrier frequency to determine a drift error. From the drift error a control signal adjustment required to correct the drift error is computed (522). The control signal of the reference oscillator (102) is adjusted (524) by the control signal adjustment to correct the drift error.

Abstract: A method and apparatus for producing a temperature stabilized frequency from a signal generator in a monitoring station is described. The signal generator monitors the voltage response of an RC circuit where the resistive portion is formed by a thermistor, to produce a time-dependent signal. A comparator compares the time-dependent signal to a reference voltage to determine a rise time of the voltage across the capacitor. Based upon a software timer loop, the signal generator determines a temperature range by selecting data from a look-up table based upon the rise time of the RC circuit.

Abstract: A frequency modulation circuit which varies the resonance frequency of an LC resonance circuit, and which corresponds to the frequency modulation conversions of all TV methods with a simple constitution. Each of a plurality of passive element series circuits for varying a time constant of the LC resonance circuit is composed of, for instance, a capacitor and a resistor, which is switched and controlled by connecting to or separating from the LC resonance circuit by a switching circuit such as a transistor. Thereby, the oscillation frequency of the LC resonance circuit can be easily converted to a predetermined frequency.

Abstract: A method of compensating the dependence of the useful transmitter signal on the transfer function of a combiner filter in a mobile radio communication system includes filtering the useful transmitter signal in the base band before it is fed to the combiner filter. This is done in connection with carrier frequency modulation with a filter, the total transfer function of which at least approximately comprises the inverted value of the transfer function of the combiner filter transformed to the base band.

Abstract: In a data transmitter (200), a precision timing signal receiver (201) provides a precise timing signal (203) to an informationally responsive comparator (205). The informationally responsive comparator compares an output (211) of a controllable oscillator (209) to the precise timing signal to produce a comparison metric. An output of the informationally responsive comparator, comprising a combination of an information signal (207) and the comparison metric, is then used to control the controllable oscillator.

Abstract: A frequency synthesizer 10 having a digital to analog converter (DAC) 40 and a feedback system which detects the deviation of a frequency modulated signal and aligns the detected deviation. DAC 40 provides a presteering stimulus for alignment purposes. After presteering alignment, the gain of DAC 40 is accurately set for frequency deviation because modulation is sourced from the same digital to analog converter that performs presteering.

Abstract: A PLL circuit modulatable by a modulation signal having a direct current component has a voltage-controlled main oscillator, a loop divider, a phase comparator and a loop filter. The reference frequency signal for the phase comparator is derived from the modulation signal by a first compensation filter, a voltage-controlled reference oscillator and a reference divider being connected downstream of said first compensation filter. The voltage-controlled main oscillator is controlled by the modulation signal via a second compensation filter followed by a downstream data lowpass.

Abstract: In a radio transmitter, a PM input signal is provided directly to a frequency synthesizer. The synthesizer includes a PLL having a reference frequency input signal and a controlled frequency output signal. The PLL includes a frequency divider which is directly connected in a feedback circuit path between the controlled frequency output signal and the PLL's phase-detector. The frequency divider has a frequency control input signal for setting a division ratio N for the divider, and a PM circuit has as input signal the PM input signal and the frequency control input signal. The PM circuit provides an offset signal to the phase detector output, so that the PLL creates a correcting phase signal resulting from the offset signal. The magnitude of the offset signal changes as a function of the change in the value of N.

Abstract: A frequency shift keying modulating circuit produces a first frequency according to a surface acoustic wave transducer natural resonant frequency and a second frequency according to the surface acoustic wave in combination with a reactive element. The frequency selected is determined by the state of a PIN switching diode in parallel with the reactive element.

Abstract: A frequency modulation circuit includes a phase-locked loop having a reference frequency input and a controlled frequency output. The phase-locked loop has a phase detector, a filter and a voltage-controlled oscillator and, in a feedback path between the output and the phase detector, a frequency divider. Also included is a converter converting an input signal to a digital modulation signal M, and an adder inverting the most significant bit of the digital modulation signal and adding it to a digital word representing a selected frequency. The frequency divider divides a fractional number (N.F).+-.M, where N is an integer, F is a fraction and M is the digital value of modulation data.

Abstract: A D.C. modulated phase locked oscillator (60, 80, 100, 140, 160, 190, 220, 264, or 290) includes a phase locking oscillator (70, 90, 128, 180, 192, 222, 266, or 292) and a D.C. modulator (72, 92, 130, 156, 182, 194, 224, 268, or 294). Both a forward path (14) and a feedback path (16) are D.C. modulated. D.C.

Abstract: An information transmission arrangement comprising transceiver units (1, 2) located in a propagation medium (10) whose attentuation varies as a function of frequency. At least one unit (1) comprise a meter (67) for measuring the level of the received signal in order to influence the frequency variation control (32) of the control oscillator (28) in the send circuit (26, 28) of the other unit (2). This arrangement profits from a monotonic attenuation gradient of the propagation medium (10) having a zone (Z1) in the 50-60 GHz band to control the send level in a simple and effective manner.

Abstract: A method of providing DC coupled frequency modulation without center frequency offset of a RF carrier frequency generated in a phase-locked loop circuit. The circuit is automatically calibrated to generate a feedback signal for cancelling DC offsets at the input of the coupling integrator with a digital-to-analog converter and resistor network driven by a digital counter. After removing frequency modulation, the coupling integrator's output will ramp while the offsets remain uncancelled. Incrementing or decrementing the digital counter in response to the integrator's output will adjust the feedback signal until the offsets are cancelled and the integrator ceases to ramp. The counter value is stored in a memory to allow subsequent presetting of the feedback signal to the calibrated magnitude. Holding the feedback signal constant thereafter during DC coupled frequency modulation keeps the RF carrier at center frequency.

Abstract: A fractional-N synthesizer realizes automatic frequency control by adding (509) a digital representation of a determined frequency offset to a digital representation of applied modulation to create the modulus control of a programmable frequency divider (203).

Abstract: A D.C. modulated phase locked oscillator (220 or 264) is usable separately to provide an output that is both phase locked and D.C. modulated or is usable in a radio frequency receiver (200). The D.C. modulated phase locked oscillator (220or 264) includes a phase locking oscillator (222 or 266) and a D.C. modulator (224 or 268). Both a forward path (14) and a feedback path (16) are D.C. modulated. In one embodiment. D.C. modulation of the feedback path (16) includes using a modulation oscillator (64) and two flip-flops (228 and 164) to develop quadrature square waves, and using a quadrature phase shift keying (QPSK) mixer (234) to subtract a frequency of one of the square waves from the frequency in the feedback path (16). In another embodiment, D.C.

Abstract: A D.C. modulated phase locked oscillator (60, 80, 100, 140, 160, or 190) and a radio frequency receiver (200) that utilizes the D.C. modulated phase locked oscillator (60, 80, 100, 140, 160, or 190) both include a phase locking oscillator (70, 90, 128, 180, or 192) and a D.C. modulator (72, 92, 130, 156, 182, or 194). Both a forward path (14) and a feedback path (16) are D.C. modulated. D.C.

Abstract: An improved frequency modulation apparatus (100) is provided comprising a generator (102), a biasing voltage line (116), and an interface circuit (110). The generator (102) is utilized to generate a carrier signal. A control line input (104) on the generator (102) adjusts the frequency of the carrier signal. The biasing voltage line (116) provides DC power in order to DC bias the generator (102). The interface circuit (110) couples an information signal (114) to the biasing voltage line (116) for altering the biasing of the generator (102) in response to the information signal (114). The alteration of the biasing of the generator (102) results in the carrier signal being frequency modulated by the information signal (114).

Abstract: A frequency modulation circuit includes a VCO which constitutes a PLL along with a loop filter which is operated by a current source. Such a frequency modulation circuit is formed in monolithic IC. When a power source of the IC is turned-on, a capacitor included in the loop filter is biased by an output voltage of a voltage follower which receives Vcc/2. Since this output voltage rises in the same manner as Vcc, a center frequency of the VCO can be rapidly pulled into a phase-locked state of the PLL. In addition, the frequency modulation circuit is provided with a voltage-to-current conversion circuit which increases a charging current for the capacitor in response to a mute signal generated when the power source is turned-on, whereby the time constant of the loop filter is decreased substantially.

Abstract: A frequency modulator utilizing a frequency synthesizer is disclosed. The modulator is especially useful in a mobile radio communication apparatus. The synthesizer includes a phase locked loop made up of a voltage controlled oscillator (VCO), a programmable frequency divider, a phase comparator, a second frequency divider, a reference oscillator, and a low-pass filter. When a channel control signal is input to the programmable frequency divider, the modulator sensitivity of the voltage controlled oscillator is undesirably deviated according to the channel selection. An increase of the modulator sensitivity due to an increase of the oscillation frequency is compensated for by adding a simple FET to the VCO bias circuit. A control voltage from the phase locked loop is applied to both the voltage controlled oscillator and its bias circuit.

Abstract: A frequency synthesizer (10) for providing a modulated output signal (fo) includes a reference frequency signal (fr) and a voltage controlled oscillator (14). For dividing the frequency of the output signal from the voltage controlled oscillator (14) by a divisor, a programmable divider (16) is coupled to the output of the voltage controlled oscillator (14). To produce a phase-locked loop in which the frequency of the output signal from the voltage controlled oscillator (14) is equal to the frequency of the reference frequency (fr) signal multiplied by the divisor, a phase detector (12 ) having a first input coupled to the reference frequency signal (fr), a second input coupled to the output of the programmable divider (16), and an output coupled to the input of the voltage controlled oscillator (14) is also provided. A first integrator (24) for integrating a modulating signal provides an integrated signal and a first control signal.

Abstract: A frequency synthesizer for providing a modulated output signal includes a phase comparator, a loop filter, and a voltage controlled oscillator (VCO). The phase comparator receives a reference input signal and a signal related to the VCO output, and generates a control current. A modulation circuit receives a modulation signal and provides both a modulation current and a modulation voltage. The modulation current is summed with the control current at one input of the loop filter, while the modulation voltage is applied to a second input of the loop filter. The VCO is controlled by the output of the loop filter to produce the modulated output signal.

Abstract: In a phase-locked loop type synthesizer comprising a phase-locked loop which comprises a phase comparator, a loop filter, a voltage controlled oscillator having a gain Kv, and a circuit for feeding back an output from the voltage controlled oscillator to the phase comparator through a frequency divider having a frequency division ratio N and which is supplied with first and second modulation signals at first and second sections through first and second adders, first and second gain control circuits are provided on input lines of the first and the second modulation signals, respectively. The first gain control circuit has a first gain adjusted to be in inverse proportion to the frequency division ratio N while the second gain control circuit has a second gain adjusted to be in inverse proportion to the gain Kv. Preferably, the first adder is connected between the phase comparator and the loop filter while the second adder is connected between the loop filter and the voltage controlled oscillator.

Abstract: A transmitter includes a phase-locked loop (PLL) circuit whose output is frequency modulated with a modulation signal. The modulated signal is amplified by an amplifier which is turned on only during a signal transmission of the transmitter. At a time when the amplifier is turned, the output frequency of PLL circuit fluctuates. To depress this frequency fluctuation, the transmitter includes a frequency fluctuation depressing (FFD) circuit. Upon the turning-on of the amplifier, FFD circuit applies a voltage change to the modulation signal so that the frequency fluctuation is depressed.

Abstract: A circuit for use in conjunction with a voltage controlled oscillator (VCO). The circuit introduces modulation into a radio system (to create a substantially flat frequency response) at the same VCO port at which VCO frequency centering and negative bias control signals are introduced. A potentiometer is utilized both for providing an adjustable negative bias to the varactor in the VCO resonant circuit and for setting the VCO to the appropriate center frequency. Modulation compensation circuitry is coupled to the control arm of the potentiometer and to the anode of the varactor (via a choke 4). The modulation compensating circuitry is preferably designed to have a transfer function that is substantially the inverse of the closed loop transfer function of the phase locked loop system with respect to the frequency modulation of the VCO.

Abstract: A single input wideband modulation system for a phase locked loop is achieved by interposing the inverse analogue of the closed phase locked loop transfer function between the modulation source and the VCO modulation input. A first branch of the interposed circuit directly passes high frequency signals from the modulation source to a summing device tied to an input of the VCO. A second branch of the interposed circuit boosts low frequency signals and blocks high frequency signals recieved from the modulation source and passes such signal to the summing device where signals from the first and second branches are summed to permit wideband modulation of the VCO. All the modulation processing is performed outside the phase locked loop.

Abstract: Several embodiments are disclosed of a modulation equalization network associated with a phase locked loop to achieve frequency independent modulation of the VCO. The equalization network is disposed to introduce the modulation signal into the control loop ahead of the loop filter but after the phase detector output. The interposed equalization network requires only a single input port to achieve a flat modulation response thereby lending itself to a modular implementation. The modulation processing is performed totally outside the phase locked loop. The network serves to provide a boost to low frequency signals from the modulation source using an integrator network while providing a high frequency response that is essentially the inverse of the phase locked loop filter response.

Abstract: A phase-locked loop (PLL) frequency synthesizer having an analog, out-of-band component path and a digital, in-band component path to provide frequency modulation (FM) of the synthesized output signal is described. The in-band FM component is octave scaled by an analog scaling means and coupled to an analog-to-digital converter to provide a digital number to be decade added to the PLL divide number to change the PLL frequency in response to the in-band FM signal. The out-of-band FM component is also scaled and applied to a loop summing node and summed with the PLL error signal to vary the PLL frequency. The scaling in both the in-band component path and out-of-band component path is equalized to provide a flat frequency response. Additional, the in-band component is scaled to allow use of the analog-to-digital converter over its maximum range to maintain a high signal-to-noise ratio.

Abstract: An improved frequency modulator apparatus for use in phase-locked loop (PLL) frequency synthesizers is disclosed which makes possible high deviation, low distortion, FM signals for a wide range of modulating signals, such as digital data or low frequency tone modulation. In a first embodiment having the improved frequency modulator, this apparatus advantageously injects the modulation signal into two ports, one at the VCO and the other provided in an unmodulated reference source signal chain. By properly balancing the levels into each of these two ports, a cancellation effect occurs which nulls the modulation signal at the output of the phase detector. In a second embodiment, the improved frequency modulator is incorporated in a PLL frequency synthesizer with an offset mixer to achieve relatively wide percentage deviation at a low frequency RF carrier.

Abstract: A combined phase and frequency modulation device for modulating a data signal in order to generate a plurality of narrow band signals for a communication system is disclosed, characterized by a direct synthesis phase locked loop for generating an output data signal having a selected frequency, a signal divider and phase modulator circuit, and a frequency multiplier for multiplying a modulated signal to produce an output having a desired frequency. The signal divider and phase modulator circuit includes a frequency divider which produces two quadrature related signals from the output data signal. A modulator connected with the frequency divider generates a suppressed carrier double sideband signal from one of the quadrature related signals. A summing device connected with the frequency divider and with the modulator combines the carrier signal with the other quadrature related signal to produce the modulated output signal which is multiplied by the frequency multiplier.