EP0599409A2
Expired / Lapsed
EP
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A direct conversion receiver
Assignee: Koninklijke Philips NV
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Filing: 1993-11-18
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Granted: —
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Expires: 2013-11-18
Abstract
Abstract In known direct conversion receivers, e.g. for paging, for getting a correct polarity a.f.c. signal, the a.f.c. signal is derived by multiplying demodulated data with an error voltage obtained with a frequency discriminator. Apart from the fact that this requires an elaborate circuit, data filter delay has to be compensated for before multiplying the demodulated data with an output signal of the frequency discriminator. The direct conversion receiver (1) according to the present invention comprises a.f.c. means comprising a digital-to-analog converter (31) for providing a control signal (ct) for a local oscillator (14). The control signal (ct) is determined on a valid data scanning basis, i.e. during scanning intervals, signal quality determining means (32) determine valid data (vdta) while a controller (20) steps through an output range (DAR) of the digital-to-analog converter (31). The control signal (ct) is adjusted within a valid data range (VR), and the scanning is repeated on a regular basis. The present invention provides a simple a.f.c. means, an otherwise necessary loop filter being dispensed with. Signal quality can be based on measured signal frequency or on other criteria such as a valid CRC, a CRC with a unique error syndrome, or the like.
Inventors
- 👤 Rishi Mohindra
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 01:26
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H04; H04B; H04B1/00; H04B1/06; H04B1/16; H04B1/30; H03D; H03D3/00; H03D3/02; H03D3/04; H03D7/00; H03D7/16; H03D7/165
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
152 words
A direct conversion receiver (1) comprising a local frequency generating arrangement (14, 15, 16) which is coupled to a pair of quadrature related mixers (7, 11) for mixing down an rf input signal (rf) to quadrature related signals (I, Q), a demodulator (18) for demodulating the quadrature related signals into demodulated data (dta), and a.f.c. means for providing a control signal (ct) for the local frequency generating arrangement (14), the a.f.c. means being coupled to quadrature paths (4, 5), characterized in that the a.f.c. means comprise a digital-to-analog conversion arrangement (31) for providing the control signal (ct), signal quality determining means (32) for determining a valid data signal (vdta) from the demodulated data (dta), storage means (21) for storing a valid data range (VR) during scanning intervals, and means for adjusting (20, 22) an output signal of the digital-to-analog conversion arrangement (31) to an adjustment value within the valid data range (VR).
Claim 2
Dependent Claim
27 words
A direct conversion receiver (1) as claimed in claim 1, wherein the adjustment value is a value around a mid-range value within the valid data range (VR).
Claim 3
Dependent Claim
42 words
A direct conversion receiver as claimed in claim 1 or 2, wherein in a first operating mode a first range (DAR) is scanned, and in a second operating mode a second, limited, range (LR) is scanned around a previous adjustment value (ct).
Claim 4
Dependent Claim
23 words
A direct conversion receiver (1) as claimed in claim 1, 2 or 3, wherein valid data scanning is halted during expected data frames.
Claim 5
Dependent Claim
23 words
A direct conversion receiver (1) as claimed in claim 1, 2, 3 or 4, wherein the scanning is repeated on a regular basis.
Claim 6
Dependent Claim
46 words
A direct conversion receiver (1) as claimed in any one of claims 1 to 5, wherein the signal quality determining means (32) comprise a frequency-to-voltage converter (40) coupled to an analog-to-digital conversion arrangement or to a comparison arrangement (41), for determining the valid data signal (vdta).
Claim 7
Dependent Claim
40 words
A direct conversion receiver (1) as claimed in any one of the claims 1 to 5, wherein the signal quality determining means (32) comprise a microcontroller (20) coupled to a gated counter (70) for determining the valid data signal (vdta).
Claim 8
Dependent Claim
62 words
A direct conversion receiver (1) as claimed in any one of the claims 1 to 5, wherein the signal quality determining means (32) determine the valid data signal (vdta) on the basis of signal characteristics of the demodulated data (dta), such as a valid CRC, a CRC with a unique error syndrome, a data frame preamble, a sync pattern, or a BER.
Claim 9
Dependent Claim
37 words
A direct conversion communication device (1) as claimed in any one of the claims 1 to 7, wherein filtered demodulated data (fdta) are used for determining the valid data signal (vdta) instead of the demodulated data (dta).
Claim 10
Dependent Claim
63 words
A direct conversion receiver as claimed in any one of the claims 1 to 7, comprising limiters (9, 13) in the quadrature paths (4, 5), wherein an output signal of one of the limiters (9, 13) or a product of the output signals of the limiters (9, 13) is used for determining the valid data signal (vdta) instead of the demodulated data (dta).
Claim 11
Dependent Claim
27 words
A direct conversion receiver (1) as claimed in any one of the preceding claims, wherein the local frequency generating arrangement (14) comprises a thermally insulated crystal (15).
Claim 12
Dependent Claim
162 words
A direct conversion receiver (1) comprising a local frequency generating arrangement (14, 15, 16) which is coupled to a pair of quadrature related mixers (7, 11) for mixing down an rf input signal (rf) to quadrature related signals (I, Q), a demodulator (18) for demodulating the quadrature related signals into demodulated data (dta), and a.f.c. means for providing a control signal (ct) for the local frequency generating arrangement (14), the a.f.c. means being coupled to quadrature paths (4, 5), characterized in that the direct conversion receiver (1) comprises first a.f.c. means as claimed in any one of the preceding claims, second a.f.c. means (14, 15, 16, 17, 18, 20, 21, 22) particularly suitable for relatively strong rf input signals, and RSSI-means (33) for determining a signal strength of the rf input signal (rt), the direct conversion receiver (1) being arranged for switching over from the first to the second a.f.c. means if the determined signal strength exceeds a predetermined threshold value (thr1).
Claim 13
Dependent Claim
70 words
A direct conversion receiver as claimed in claim 12, wherein the second a.f.c. means comprise means (17, 20, 22) for determining a frequency offset (δf) of the local frequency generating arrangement (14) on the basis of measured frequencies (f₀, f₁) of the demodulated data (dta), for an in-range and an out-of-range situation, respectively, and means (LUT) for determining the control signal (ct) on the basis of the determined frequency offset.
Claim 14
Dependent Claim
40 words
A direct conversion receiver as claimed in claim 13, wherein the means for determining the control signal (ct) comprise a lookup-table (LUT) comprising predetermined control signal values, the determined frequency offset (δf) being an address value for addressing the lookup-table.
References Cited (Backward Citations)
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