Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
144 words
A phase-locked loop comprising a controllable oscillator which is phase-coupled through a phase detection arrangement and a low-pass filter to an input carrier applied to a signal input of the phase detection arrangement, characterized in that the phase detection arrangement comprises first, second and third mixer stages which are mutually coupled in succession, an auxiliary mixing signal being applied to said first and third mixer stages from a signal generator, an input of one of the first and second mixer stages being connected to the signal input of the phase detection arrangement and an input of the other of the two last-mentioned mixer stages being coupled to an output of the controllable oscillator, said low-pass filter having a cut-off frequency which is lower than the fundamental frequency of said auxiliary mixing signal, said fundamental frequency being lower than the frequency of the input carrier.
Claim 2
Dependent Claim
144 words
A phase-locked loop comprising a controllable oscillator which is phase-coupled through a phase detection arrangement and a low-pass filter to an input carrier applied to a signal input of the phase detection arrangement, characterized in that the phase detection arrangement comprises first, second and third mixer stages which are mutually coupled in succession, an auxiliary mixing signal being applied to said first and third mixer stages from a signal generator, an input of one of the first and second mixer stages being connected to the signal input of the phase detection arrangement and an input of the other of the two last-mentioned mixer stages being coupled to an output of the controllable oscillator, said low-pass filter having a cut-off frequency which is lower than the fundamental frequency of said auxiliary mixing signal, said fundamental frequency being lower than the frequency of the input carrier.
Claim 3
Dependent Claim
38 words
A phase-locked loop as claimed in Claim 1, characterized in that the signal input is coupled to the input of the second mixer stage and the controllable oscillator is coupled to the input of the first mixer stage.
Claim 4
Dependent Claim
67 words
3i A phase-locked loop as claimed in Claim 2, characterized in that a filter device is arranged between the second and third mixer stages for selecting the frequency component in the output signal of the second mixer stage, which component is located at the fundamental frequency of the auxiliary mixing signal, and that a delay circuit is arranged between the signal generator and the third mixer stage.
Claim 5
Dependent Claim
24 words
A phase-locked loop as claimed in Claim 3, characterized in that an amplifier/limiter is arranged between the filter device and the third mixer stage.
Claim 6
Dependent Claim
21 words
A phase-locked loop as claimed in Claim 4, characterized in that the amplifier/limiter is provided with a DC negative feedback path.
Claim 7
Dependent Claim
109 words
A directly mixing synchronous AM-receiver having an RF input coupled to a synchronous AM detector to which a synchronous RF carrier is applied through a synchronous in-phase carrier for direct conversion of an RF-AM receiver signal to the baseband, characterized by a phase-locked loop as claimed in any of the preceding Claims 2 to 5, the signal input of said loop being coupled to the said RF input, the controllable oscillator also functioning as a tuning oscillator and being coupled to said carrier input of the synchronous AM detector, the fundamental frequency of the auxiliary mixing signal being lower than the highest modulation frequency in the RF-AM receiver signal.
Claim 8
Dependent Claim
41 words
A directly mixing synchronous AM-receiver as claimed in Claim 6, characterized by a phase-locked loop as claimed in Claim 3, wherein the auxiliary mixing signal is frequency-modulated with a pseudo-random signal and at least substantially does not contain any DC information.
Claim 9
Dependent Claim
89 words
A directly mixing synchronous AM-receiver as claimed in Claim 7, including a phase-locked loop as claimed in Claim 3, characterized in that the filter device includes a bandpass filter having a resonant frequency at the central frequency of the auxiliary mixing signal, and a passband which on the one hand is sufficiently narrow to suppress the DC component in the output signal of the second mixer stage and on the other hand is zufficiently wide to at least predominantly comprise the frequency spectrum of the modulated auxiliary mixing signal.
Claim 10
Dependent Claim
84 words
9 . A directly mixing synchronous AM receiver as claimed in Claim 8, characterized in that the auxiliary mixing signal is a frequency modulated square wave signal having a frequency which varies in a range of the order of 300 Hz around a central value of the order of 2 kHz, said bandpass filter having a 3 dB bandwidth of not more than 2 kHz around the said central value, the delay in the delay circuit being of the order of 120 / usec.