Patent EP0253680A2 successfully refreshed from Google Patents.
EP0253680A2
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EP
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Angle modulated signal receiving apparatus
Assignee: NTT Docomo Inc
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Filing: 1987-07-17
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Granted: —
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Expires: 2007-07-17
Abstract
Abstract Local frequency, which is subject to fluctuate in a mobile subscriber set, is locked to stable transmit frequency of a base station. A mobile subscriber set (Figure 3) for receiving an angle modulated signal has a frequency mixer (3.6, 3.9), for converting a wireless receive frequency to an intermediate frequency by using a local frequency (FL1, FL2), a limiter (3.11) for limiting amplitude of intermediate frequency signal, a discriminator (3.12) for demodulating the angle modulated signal, a standard oscillator (3.1) such as a quartz crystal oscillator and a synthesizer (64) for providing the local frequency to the mixer (3.6), a digital frequency counter (3.14) for measuring intermediate frequency, and control means (3.16) for adjusting the standard oscillator (3.1) depending upon the error in intermediate frequency measured by said counter (3.14).
Inventors
- 👤 Isao Shimizu
- 👤 Katsunori Miyatake
- 👤 Shuji Urabe
- 👤 Kazuaki Murota
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 23:31
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/06; H03J7/065; H03D; H03D7/00; H03D7/16; H03D7/161; H03J5/00; H03J5/02; H03J5/0245; H03J5/0272; H03J5/0281
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
110 words
Angle modulated signal receiving apparatus comprising a standard oscillator (3.1); at least one frequency mixer (3.6) for converting a received radio frequency to a first intermediate frequency signal by using the local frequency signal from the oscillator; a limiter (3.11) for limiting the amplitude of the first intermediate frequency signal; a discriminator (3.12) coupled to the output of the limiter (3.11) for demodulating the angle modulated signal; monitoring means including a digital frequency counter (3.14) coupled with the output of the limiter (3.11) to monitor the first intermediate frequency signal; and control means (3.16) for adjusting the frequency of the oscillator depending upon the output of the digital frequency counter.
Claim 2
Dependent Claim
110 words
Angle modulated signal receiving apparatus comprising a standard oscillator (3.1); at least one frequency mixer (3.6) for converting a received radio frequency to a first intermediate frequency signal by using the local frequency signal from the oscillator; a limiter (3.11) for limiting the amplitude of the first intermediate frequency signal; a discriminator (3.12) coupled to the output of the limiter (3.11) for demodulating the angle modulated signal; monitoring means including a digital frequency counter (3.14) coupled with the output of the limiter (3.11) to monitor the first intermediate frequency signal; and control means (3.16) for adjusting the frequency of the oscillator depending upon the output of the digital frequency counter.
Claim 3
Dependent Claim
48 words
Apparatus according to claim 1, further comprising a frequency synthesizer (64) having a voltage controlled oscillator (3.3), a phase detector (3.2) and a frequency divider (3.4) connected in a loop, the frequency synthesizer being connected to the output of the standard oscillator for providing an adjustable local frequency.
Claim 4
Dependent Claim
31 words
Apparatus according to claim 1 or claim 2, further comprising a noise canceller (3.13) provided between the output of the limiter (3.11) and the input of the digital frequency counter (3.14).
Claim 5
Dependent Claim
37 words
Apparatus according to any of claims 1 to 3, further comprising a frequency divider (3.17) to divide the output frequency of the standard oscillator (3.1) to provide a time base signal to the digital frequency counter (3.14).
Claim 6
Dependent Claim
40 words
Apparatus according to any of the preceding claims, further comprising a second mixer (3.9) for mixing the first intermediate frequency with a second local frequency to generate a second intermediate frequency which is fed to the digital frequency counter (3.14).
Claim 7
Dependent Claim
53 words
Apparatus according to claim 5, further comprising a switch (56) to selectively couple the second intermediate frequency or the second local frequency to the input of the digital frequency counter (58), the control means (60) being responsive to the counts monitored by the digital frequency counter to adjust the frequency of the oscillator.
Claim 8
Dependent Claim
35 words
Apparatus according to claim 5 or claim 6, further comprising a frequency multiplier (3.8a) for providing the second local frequency to the second mixer (3.9) by multiplying the output frequency of the standard oscillator (3.1).
Claim 9
Dependent Claim
87 words
Apparatus according to any of the preceding claims, wherein means (52m) for measuring receive level is provided so that the control means is active only when the receive level is higher than a predetermined level, and a sample and hold circuit (70) is provided to hold a control level when the receive level is higher than the predetermined level, so that the control means (60a) operates with the control level held in the sample and hold circuit (70) when the receive level is lowerthan the predetermined level.
Claim 10
Dependent Claim
53 words
Apparatus according to any of the preceding claims, comprising a plurality of frequency mixers to each of which is fed a common local frequency, a comparator (80) and a switch (82) for selecting the highest level of intermediate frequency, the selected intermediate frequency being applied in use to the digital frequency counter (58).
Claim 11
Dependent Claim
21 words
Apparatus according to any of the preceding claims, further comprising a transmitter, the transmit frequency being provided by the standard oscillator.
Claim 12
Dependent Claim
11 words
A mobile subscriber apparatus according to any of the preceding claims.
Claim 13
Dependent Claim
68 words
Apparatus according to any of claims 1 to 10, wherein the digital frequency counter for measuring IF frequency is provided in a base station to measure receive IF frequency, the base station having means for forwarding the measured error in IF frequency to a subscriber set, the subscriber set being adapted to derive the error from the base station to adjust the standard oscillator in the subscriber set.
References Cited (Backward Citations)
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